JP2017085037A - Negative electrode body for nonaqueous lithium power storage device, and nonaqueous lithium power storage device arranged by use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode body which can offer a nonaqueous lithium power storage device capable of suppressing the heat generation and combustion during a nail pricking test, keeping a high electric conductivity, and developing a high output.SOLUTION: A negative electrode body for a nonaqueous lithium power storage device comprises: a negative electrode current collector; and a negative electrode active material layer provided on one or each face of the negative electrode current collector. A peel strength when peeling the negative electrode active material layer from the negative electrode current collector is in a range of 0.05-0.60 N/cm.SELECTED DRAWING: None

Description

The present invention relates to a negative electrode body for a non-aqueous lithium storage element and a non-aqueous lithium storage element using the same.

In recent years, midnight power storage systems, home-use distributed power storage systems based on solar power generation technology, power storage systems for electric vehicles, etc. have attracted attention from the viewpoint of global environment conservation and effective use of energy for resource saving. Yes.
The first requirement in these power storage systems is that the energy density of the power storage elements used is high. As a promising candidate for an energy storage device with high energy density that can meet such demands, development of lithium ion batteries has been energetically advanced.
The second requirement is high output characteristics. For example, a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell electric vehicle) requires a high output discharge characteristic in the power storage system during acceleration. Has been.

At present, electric double layer capacitors, nickel metal hydride batteries, and the like have been developed as high power storage elements.
Among the electric double layer capacitors, those using activated carbon for the electrodes have an output characteristic of about 0.5 to 1 kW / L. This electric double layer capacitor has high durability (particularly cycle characteristics and high-temperature storage characteristics), and has been considered as an optimum electric storage element in the field where the high output is required. However, for its practical use, the energy density is as low as about 1 to 5 Wh / L and the output duration is short.

On the other hand, nickel-metal hydride batteries currently used in hybrid electric vehicles achieve high output equivalent to electric double layer capacitors and have an energy density of about 160 Wh / L. However, research is underway energetically to further increase the energy density and output, further improve the stability at high temperatures, and enhance the durability.
In addition, research for higher output is also being conducted in lithium ion batteries. For example, a lithium ion battery has been developed that can obtain a high output exceeding 3 kW / L at a discharge depth (that is, a value representing what percentage of the discharge capacity of the device is discharged) 50%. However, the energy density is 100 Wh / L or less, and the high energy density, which is the greatest feature of the lithium ion battery, is intentionally suppressed. Further, its durability (particularly cycle characteristics and high temperature storage characteristics) is inferior to that of an electric double layer capacitor. Therefore, the lithium ion battery can be used only in a range where the depth of discharge is narrower than the range of 0 to 100% in order to have practical durability. Since the capacity that can actually be used is further reduced, research for further improving the durability is being actively pursued.

As described above, there is a strong demand for practical use of a power storage element having high output density, high energy density, and durability. However, the above-described existing power storage element has advantages and disadvantages. Therefore, a new power storage element that satisfies these technical requirements has been demanded, and development of a power storage element called a lithium ion capacitor has been actively developed as a promising candidate.
A lithium ion capacitor is a kind of power storage element that uses a non-aqueous electrolyte containing an electrolyte containing lithium ions (that is, a non-aqueous lithium-type power storage element),
It is a storage element that charges and discharges by non-Faraday reaction by adsorption / desorption of anions in the positive electrode and by Faraday reaction by occlusion / release of lithium ions in the negative electrode, as in the case of electric double layer capacitors. .

An electric double layer capacitor that charges and discharges by a non-Faraday reaction in both the positive electrode and the negative electrode is excellent in output characteristics as described above, but has a low energy density. On the other hand, a lithium ion battery that is a secondary battery that charges and discharges by a Faraday reaction in both the positive electrode and the negative electrode is excellent in energy density but inferior in output characteristics. A lithium ion capacitor is a new power storage element that aims to achieve both excellent output characteristics and high energy density by performing charge and discharge by a non-Faraday reaction at the positive electrode and a Faraday reaction at the negative electrode.
As an example of a lithium ion capacitor, a non-aqueous lithium storage element that combines high energy density and high output by using activated carbon as a positive electrode active material and a composite porous material as a negative electrode active material has been proposed (patent) Reference 3).

Applications that use lithium ion capacitors include, for example, railways, construction machinery, and automobile power storage. In these applications, since the operating environment is harsh, it is necessary to ensure sufficient safety in the event of crushing, short-circuiting, overcharging, etc. in the case of capacitors used. In particular, ignition of the capacitor at the time of crushing or short circuit is a safety problem. As a countermeasure technique for such a problem, a lithium ion capacitor that suppresses ignition by adding a flame retardant into an electrolytic solution has been proposed (Patent Document 1).
Moreover, although it is a lithium ion secondary battery, the technique which prescribes | regulates the cutting strength of an electrode and ensures high safety | security is proposed (patent document 2).

JP 2011-204822 A JP 2014-209455 A International Publication No. 2014/088074

As a result of studies by the present inventors, according to the non-aqueous lithium storage element described in Patent Document 3, it has become possible to improve both energy density and durability while maintaining high output characteristics. However, in the safety test assuming extremely severe conditions such as crushing and internal short circuit, the electricity storage element has a high heat generation temperature of the electricity storage element and may ignite, which should be improved in terms of safety. There is.
In recent years, in terms of safety, it has been required that further safety be ensured by a test assuming such a severe situation. On the other hand, in pursuit of safety, it is also important that various characteristics (output characteristics, etc.) of the storage element are not deteriorated.
In view of the above situation, the problem to be solved by the present invention is to provide a non-aqueous lithium storage element that exhibits high output in addition to suppressing heat generation and ignition at the time of abnormality and high safety. is there.

The present inventors have advanced research to solve the above-mentioned problems. As a result, by controlling the peel strength of the active material layer in the negative electrode body to a specific range lower than in the prior art, heat generation and ignition during the nail penetration test are suppressed, and higher electrical conductivity is maintained, The present inventors have found that a non-aqueous lithium storage element that exhibits high output can be obtained.
That is, the present invention is as follows.

[1] A negative electrode current collector and a negative electrode active material layer provided on one side or both sides of the negative electrode current collector,
A negative electrode for a non-aqueous lithium storage element, wherein a peel strength when peeling the negative electrode active material layer from the negative electrode current collector is in a range of 0.05 N / cm or more and 0.60 N / cm or less. body.
[2] The negative electrode body for a non-aqueous lithium storage element according to [1], wherein the negative electrode current collector has a through hole.

[3] The negative electrode active material is a composite porous material in which a carbon material is deposited on the surface of activated carbon, and
The amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is Vm1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is Vm2 (cc / g ) Satisfying 0.010 ≦ Vm1 ≦ 0.250, 0.001 ≦ Vm2 ≦ 0.200, and 1.5 ≦ Vm1 / Vm2 ≦ 20.0, according to [1] or [2] A negative electrode body for a non-aqueous lithium storage element.
[4] The negative electrode active material is a composite porous material in which a carbon material is deposited on the surface of activated carbon, and
Lithium ions of 1,050 mAh / g or more and 2,050 mAh / g or less per unit mass of the composite porous material are pre-doped,
The mass ratio of the carbonaceous material to the activated carbon is 10% or more and 60% or less, and the thickness of the negative electrode active material layer is 20 μm or more and 45 μm or less per side, according to [1] or [2] Negative electrode body for water-based lithium storage element.

[5] The electrode laminate including the negative electrode body for a non-aqueous lithium storage element, the positive electrode body, and the separator according to any one of [1} to [4], and a non-aqueous electrolyte solution are housed in an exterior body. And
The positive electrode body includes a positive electrode current collector and a positive electrode active material layer including a positive electrode active material provided on one or both surfaces of the positive electrode current collector, and the positive electrode active material includes activated carbon. A non-aqueous lithium-type electricity storage device characterized by the above.
[6] The amount of mesopores V1 (cc / g) derived from the pores having a diameter of 20 mm or more and 500 mm or less calculated by the BJH method satisfies 0.8 <V1 ≦ 2.5, and the activated carbon was calculated by the MP method. The amount of micropores V2 (cc / g) derived from pores having a diameter of less than 20 mm satisfies 0.8 <V2 ≦ 3.0, and the specific surface area measured by the BET method is 3,000 m ² / g or more 4 , the following 000m ² / g, the non-aqueous lithium-type storage element according to [5].

  The non-aqueous lithium storage element using the negative electrode body for a non-aqueous lithium storage element of the present invention has the effect that heat generation and ignition during a nail penetration test are suppressed, safety is high, and higher output is exhibited. Play.

Hereinafter, although embodiment of this invention is described in detail, this invention is not limited to the following embodiment.
<Negative electrode body>
The negative electrode body for a non-aqueous lithium storage element according to the present invention is composed of a negative electrode current collector and a negative electrode active material layer provided on one or both surfaces thereof, and the negative electrode active material layer is defined as the negative electrode body. The peel strength when peeling from is 0.05 or more and 0.60 N / cm or less. The negative electrode current collector may have a through hole.

The negative electrode body for a non-aqueous lithium storage element in one embodiment of the present invention preferably has a value when the peel strength when the negative electrode active material layer is peeled from the negative electrode body is measured using a tensile tester. Is 0.05 N / cm or more and 0.60 N / cm or less. The upper limit of this value is more preferably 0.55 N / cm or less, and particularly preferably 0.5 N / cm or less. If the peel strength is 0.05 N / cm or more, the active material can be produced without peeling off when assembling an electricity storage device using such a negative electrode body, and the electrical conductivity of the negative electrode body is kept high. be able to. On the other hand, if the peel strength is 0.6 N / cm or less, heat generation and ignition of the electricity storage element during the nail penetration test can be suppressed, and safety can be further improved.
By setting the peel strength when peeling the negative electrode active material layer from the negative electrode body in the above-mentioned range, it is not detailed about the mechanism that can obtain high electrical conductivity while suppressing heat generation and ignition at the time of abnormality. However, the present inventors presume as follows. That is, the negative electrode body for a non-aqueous lithium storage element of the present invention is
At the time of abnormality, the negative electrode active material layer is quickly peeled off from the negative electrode body, so that the energy of the negative electrode active material is dispersed and the energy is not concentrated, so that heat generation and ignition can be suppressed;
Since the amount of each component in the negative electrode active material layer is optimized, the electrical conductivity between the active materials can be kept high.
For these reasons, it is considered that both of these performances can be achieved. However, the present invention is not limited to the above action mechanism.

   The peel strength (N / cm) in the present invention is a value measured using a tensile tester (STB-1225S) manufactured by A & D. The electrode body used for the measurement is cut into a size of 2.5 cm × 10 cm, and cello tape (registered trademark, product number “CT405AP-24”, 24 mm × 35 m) manufactured by Nichiban Co., Ltd. is attached. Remove about 5mm from the end of the tape, and attach the tape side to the upper side (tensile side) of the tensile tester and the electrode side to the lower side (fixed side) of the tensile tester. The integrated average load at a strain of 25 mm to 65 mm in the strength curve when pulled 100 mm at a speed of 50 mm / min in the direction is used as tensile strength data. The test is preferably carried out in a general environment of 25 ° C.

[Component 1 of current collector (current collector)]
As the material of the negative electrode current collector, a metal having high electron conductivity is preferably used. For example, aluminum, copper, nickel, SUS (stainless steel), titanium, etc. are mentioned. Copper is preferred.
The thickness of the current collector is preferably 1 to 100 μm.
The negative electrode current collector used in the present invention may be provided with a through hole.
The shape of the through hole provided in the negative electrode current collector can be a circle, an ellipse, a rhombus, an irregular shape, or the like. The average hole diameter of the through holes is preferably in the range of 0.01 mm or more and 0.19 mm or less. The hole diameter here refers to the shortest linear distance passing through the center of gravity of the planar shape of the through-hole among the distances between the two points on the outer edge of the through-hole. For example, if the shape of the through hole is circular, it means a diameter, and if it is an ellipse, it means a short axis diameter. When the hole diameter is 0.01 mm or more, the negative electrode active material layer can bite into the through hole, which leads to an increase in the adhesive strength between the active material layer and the current collector. When the hole diameter is 0.19 mm or less, the through-hole pattern is difficult to reflect on the uneven pattern on the surface of the active material layer, and the surface roughness of the active material layer can be reduced. In addition, the active material layer is easily supported by the metal foil inside the through hole, and the active material layer is less likely to peel from the current collector.

  The opening ratio, which is the ratio of the total area of the through-hole region to the area of one side of the current collector (including the area of the through-hole region), is preferably 1% or more and 50% or less, and more preferably 10% or more and 30% or less. . If the open area ratio is 1% or more, the electrolyte solution can move in the direction perpendicular to the surface of the current collector, so that the impregnation rate of the electrolyte solution is expected to be improved. Moreover, if the hole area ratio is 50% or less, there is a sufficient area of the current collector material that contributes to electron conductivity, which leads to lower resistance of the electrode and higher strength of the current collector. Here, the area of one surface of the current collector does not include the ear portion for welding the electrode tab (the region of the current collector where the active material layer is not laminated), and the active material layer is laminated. It means the area of only the region.

[Component 2 of the negative electrode body (active material layer)]
(Active material)
The negative electrode active material layer in this embodiment contains at least a negative electrode active material.
The negative electrode active material includes a carbon material that can occlude and release lithium ions. As the negative electrode active material, only this carbon material may be used, or in addition to this carbon material, another material that occludes and releases lithium ions may be used in combination. Examples of the other material include lithium titanium composite oxide and conductive polymer. In the illustrated embodiment, the content of the carbon material capable of occluding and releasing lithium ions is preferably 50% by mass or more, more preferably 70% by mass or more based on the total amount of the negative electrode active material. Although it can be 100% by mass, it is preferably 90% by mass or less, and may be 80% by mass or less, for example, from the viewpoint of obtaining the effect of the combined use of other materials.

Examples of the carbon material that can occlude and release lithium ions include hard carbon, graphitizable carbon, and composite porous carbon material. More preferable examples of the negative electrode active material are composite porous carbon materials 1 and 2 formed by depositing a carbon material on the surface of activated carbon, which will be described later, and these are advantageous in terms of resistance of the negative electrode.
As the carbon material in the negative electrode active material, only one or more selected from the composite porous carbon materials 1 and 2 may be used, or together with one or more selected from the composite porous carbon materials 1 and 2, Other carbon materials may be used in combination.
Hereinafter, the above-described composite porous materials 1 and 2 and other carbon materials will be described individually and sequentially.

-Composite porous material 1-
The composite porous material 1 is a composite porous material in which a carbon material is deposited on the surface of activated carbon, and the mass ratio of the carbon material to the activated carbon is 10% to 60%. This mass ratio is preferably 15% or more and 55% or less, more preferably 18% or more and 50% or less, and particularly preferably 20% or more and 47% or less. If the mass ratio of the carbon material is 10% or more, the micropores possessed by the activated carbon can be appropriately filled with the carbon material, and the charge / discharge efficiency of lithium ions is improved, which may impair durability. Absent. If the mass ratio of the carbon material is 60% or less, the specific surface area can be increased by appropriately holding the pores of the activated carbon. Therefore, the pre-doping amount of lithium ions can be increased. As a result, high output density and high durability can be maintained even if the negative electrode is thinned.

The specific surface area in BET method of the composite porous material ^1, 350m ² / ^g~1,500m 2 / g are ^preferred, 400m ² / ^g~1,100m 2 / g is more preferable. It can be said that the composite porous material 1 having a specific surface area of 350 m ² / g or more appropriately retains pores. Therefore, as a result of increasing the pre-doping amount of lithium ions, the negative electrode can be made thin. On the other hand, when the specific surface area is 1,500 m ² / g or less, it can be said that the micropores possessed by the activated carbon are appropriately filled. Therefore, since the charge / discharge efficiency of lithium ions is improved, durability is not impaired.
The composite porous material 1 can be obtained, for example, by heat treatment in a state where activated carbon and a carbon material precursor coexist.

There is no restriction | limiting in particular as activated carbon used as a raw material of said composite porous material 1 as long as the composite porous material 1 obtained exhibits a desired characteristic. For example, commercially available products obtained from various raw materials such as petroleum-based, coal-based, plant-based, and polymer-based materials can be used. In particular, it is preferable to use activated carbon powder having an average particle diameter of 1 μm or more and 15 μm or less. The average particle size is more preferably 2 μm or more and 10 μm or less.
The carbon material precursor used as the raw material of the composite porous material 1 is an organic material that can deposit the carbon material on activated carbon by heat treatment. The carbon material precursor may be a solid, a liquid, or a substance that can be dissolved in a solvent. Examples of such a carbon material precursor include pitch, mesocarbon microbeads, coke, synthetic resin (for example, phenol resin) and the like. Among these carbon material precursors, it is preferable from the viewpoint of production cost to use an inexpensive pitch. Pitch is roughly divided into petroleum pitch and coal pitch. Examples of petroleum pitches include crude oil distillation residue, fluid catalytic cracking residue (decant oil, etc.), bottom oil derived from thermal crackers, ethylene tar obtained during naphtha cracking, and the like.

  When using the pitch, the pitch is heat-treated in the presence of activated carbon, and the carbon is deposited on the activated carbon by thermally reacting the volatile component or thermal decomposition component of the pitch on the surface of the activated carbon. Material 1 is obtained. In this case, at a temperature of about 200 to 500 ° C., the deposition of pitch volatile components or pyrolysis components into the activated carbon pores proceeds, and at 400 ° C. or higher, the reaction in which the deposited components become carbon materials proceeds. . The peak temperature (maximum temperature reached) during the heat treatment is appropriately determined according to the characteristics of the composite porous material 1 to be obtained, the thermal reaction pattern, the thermal reaction atmosphere, etc., but is preferably 400 ° C. or higher. Is 450 ° C. to 1,000 ° C., more preferably about 500 to 800 ° C. The time for maintaining the peak temperature during the heat treatment may be 30 minutes to 10 hours, preferably 1 hour to 7 hours, and more preferably 2 hours to 5 hours. For example, when the heat treatment is performed for 2 hours to 5 hours at a peak temperature of about 500 to 800 ° C., the carbon material deposited on the activated carbon surface is considered to be a polycyclic aromatic hydrocarbon. The softening point of the pitch used for obtaining the composite porous material 1 is preferably 30 ° C. or higher and 100 ° C. or lower, and more preferably 35 ° C. or higher and 85 ° C. or lower. If the softening point of the pitch is 30 ° C. or higher, handling is not hindered and it is possible to prepare with high accuracy. Since many low molecular compounds exist in the pitch having this value of 100 ° C. or less, it is possible to deposit fine pores in the activated carbon.

The composite porous material 1 is obtained by depositing a carbon material on the surface of activated carbon, but the pore distribution after the carbon material is deposited inside the pores of the activated carbon is important. This pore distribution can be defined by the amount of mesopores and the amount of micropores. That is, the composite porous material 1 is derived from Vm1 (cc / g) mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method, and pores having a diameter of less than 20 mm calculated by the MP method. When the amount of micropores is Vm2 (cc / g), the following conditions:
0.010 ≦ Vm1 ≦ 0.300 and 0.010 ≦ Vm2 ≦ 0.650
It is preferable to satisfy.
If the mesopore amount Vm1 is not more than the upper limit (Vm1 ≦ 0.300), the specific surface area of the composite porous material can be increased, and the pre-doping amount of lithium ions can be increased. In addition to this, since the bulk density of the negative electrode can be further increased, the negative electrode can be made thin. When the micropore amount Vm2 is not more than the upper limit (Vm2 ≦ 0.650), high charge / discharge efficiency for lithium ions can be maintained. On the other hand, if the mesopore volume Vm1 and the micropore volume Vm2 are equal to or higher than the lower limit (0.010 ≦ Vm1, 0.010 ≦ Vm2), high output characteristics can be obtained.

In particular, the following three:
(1) 0.010 ≦ Vm1 ≦ 0.300 and 0.010 ≦ Vm2 ≦ 0.200,
(2) 0.010 ≦ Vm1 ≦ 0.200 and 0.200 ≦ Vm2 ≦ 0.400, and (3) 0.010 ≦ Vm1 ≦ 0.100 and 0.400 ≦ Vm2 ≦ 0.650
It is preferable to satisfy any one of the conditions. As for (1), 0.050 ≦ Vm1 ≦ 0.300 and 0.010 ≦ Vm2 ≦ 0.200 are more preferable.

  In the present embodiment, the MP method refers to a “t-plot method” (BC Lippens, JH de Boer, J. Catalysis, 4319 (1965)). Means a method for obtaining pore area and micropore distribution; It is a method devised by Mikhail, Brunauer, Bodor (RS Mikhal, S. Brunauer, EE Bodor, J. Colloid InterfaceSci., 26, 45 (1968)). The BJH method is a calculation method generally used for analysis of mesopores, and was proposed by Barrett, Joyner, Halenda et al. (EP Barrett, LG Joyner and P. Halenda, J. et al. Am. Chem. Soc., 73, 373 (1951)).

  The average particle size of the composite porous material 1 in the present embodiment is preferably 1 μm or more and 10 μm or less. About a lower limit, More preferably, it is 2 micrometers or more, More preferably, it is 2.5 micrometers or more. About an upper limit, More preferably, it is 6 micrometers or less, More preferably, it is 4 micrometers or less. If the average particle size is 1 μm or more and 10 μm or less, good durability is maintained.

  In the composite porous material 1, the hydrogen atom / carbon atom ratio (hereinafter also referred to as “H / C”) is preferably 0.05 or more and 0.35 or less, and 0.05 or more. More preferably, it is 0.15 or less. When H / C is 0.35 or less, the structure (typically polycyclic aromatic conjugated structure) of the carbon material deposited on the activated carbon surface is sufficiently developed, so the capacity (energy density) ) And charging / discharging efficiency is high. On the other hand, when H / C is 0.05 or more, since carbonization has not progressed excessively, a good energy density can be obtained. H / C is measured by an elemental analyzer.

The composite porous material 1 preferably has an amorphous structure derived from the activated carbon as a raw material and a crystal structure mainly derived from the deposited carbon material. A structure with low crystallinity is preferable for exhibiting high output characteristics, and a structure with high crystallinity is preferable for maintaining reversibility in charge and discharge. From such a viewpoint, the composite porous material 1 has a (002) plane spacing d002 of 3.60 mm or more and 4.00 mm or less measured by the X-ray wide angle diffraction method. The obtained crystallite size Lc in the c-axis direction is preferably 8.0 to 20.0 、, d002 is 3.60 to 3.75 、, and the c-axis direction obtained from the half width of this peak The crystallite size Lc is more preferably 11.0 to 16.0.
In the composite porous material 1, the average pore diameter is preferably 28 mm or more and more preferably 30 mm or more from the viewpoint of obtaining high output characteristics. On the other hand, from the viewpoint of obtaining a high energy density, it is preferably 65 mm or less, and more preferably 60 kg or less. In the present embodiment, the average pore diameter is obtained by dividing the total pore volume per mass obtained by measuring each equilibrium adsorption amount of nitrogen gas at each relative pressure under liquid nitrogen temperature by the BET specific surface area. Value.

-Composite porous material 2-
The composite porous material 2 is a composite porous material defined by the following mesopore volume Vm1 and micropore volume Vm2.
The composite porous material 2 has a mesopore amount derived from pores having a diameter of 20 to 500 mm calculated by the BJH method as Vm1 (cc / g) and a micropore derived from pores having a diameter of less than 20 mm calculated by the MP method. When the amount is Vm2 (cc / g), the material satisfies 0.010 ≦ Vm1 ≦ 0.250, 0.001 ≦ Vm2 ≦ 0.200, and 1.5 ≦ Vm1 / Vm2 ≦ 20.0.
The composite porous material 2 can be obtained, for example, by heat-treating activated carbon and a carbon material precursor in the coexistence state. Specific examples of the activated carbon and the carbon material precursor and the heat treatment method for producing the composite porous material 2 are substantially the same as those described above for the composite porous material 1.

The softening point of the pitch used as the carbon material precursor is preferably 30 ° C. or higher and 250 ° C. or lower, and more preferably 60 ° C. or higher and 130 ° C. or lower. If the softening point of the pitch is 30 ° C. or higher, the handling property is not hindered and it is possible to prepare with high accuracy. Since a relatively large amount of low molecular weight compounds are present in a pitch having a value of 250 ° C. or lower, it is possible to deposit even fine pores in the activated carbon.
As a specific method for producing the composite porous material 2 described above, for example, activated carbon is heat-treated in an inert atmosphere containing hydrocarbon gas volatilized from a carbon material precursor, and the carbon material is deposited in a gas phase. The method of letting it be mentioned. Moreover, the method of heat-processing by mixing activated carbon and a carbon material precursor previously, or the method of heat-processing after apply | coating the carbon material precursor dissolved in the solvent to activated carbon and drying it is also possible.
The composite porous material 2 is obtained by depositing a carbon material on the surface of activated carbon. In the composite porous material 2, the pore distribution after the carbon material is deposited inside the pores of the activated carbon is important, and the ratio of mesopore amount / micropore amount is important.

That is, in one embodiment of the present invention, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method in the composite porous material 2 is Vm1 (cc / g), the diameter calculated by the MP method. When the amount of micropores derived from pores less than 20 mm is Vm2 (cc / g), 0.010 ≦ Vm1 ≦ 0.250, 0.001 ≦ Vm2 ≦ 0.200, and 1.5 ≦ Vm1 / Vm2 It is preferable that ≦ 20.0.
The mesopore amount Vm1 is more preferably 0.010 ≦ Vm1 ≦ 0.225, and further preferably 0.010 ≦ Vm1 ≦ 0.200. About micropore amount Vm2, 0.001 <= Vm2 <= 0.150 is more preferable, and 0.001 <= Vm2 <= 0.100 is still more preferable. The ratio of mesopore amount / micropore amount is more preferably 1.5 ≦ Vm1 / Vm2 ≦ 15.0, and further preferably 1.5 ≦ Vm1 / Vm2 ≦ 10.0.
If the mesopore volume Vm1 is less than or equal to the upper limit (Vm1 ≦ 0.250), high charge / discharge efficiency with respect to lithium ions can be maintained, and the mesopore volume Vm1 and the micropore volume Vm2 are equal to or greater than the lower limit (0.010 ≦ Vm1, 0. If 001 ≦ Vm2), high output characteristics can be obtained.

In a mesopore having a large pore diameter, ion conductivity is higher than that of a micropore. Therefore, the mesopore amount is necessary to obtain high output characteristics. On the other hand, impurities such as moisture, which are considered to adversely affect the durability of the electricity storage element, are difficult to desorb in the micropores having a small pore diameter. For this reason, it is considered necessary to control the amount of micropores in order to obtain high durability. Therefore, it is important to control the ratio between the mesopore amount and the micropore amount. When this value is equal to or higher than the lower limit (1.5 ≦ Vm1 / Vm2) (that is, the carbon material adheres more to the micropores than the mesopores of the activated carbon, and the amount of mesopores in the composite porous material after deposition is large When the amount of micropores is small), high energy density and high output characteristics and high durability (cycle characteristics, float characteristics, etc.) are compatible. When the ratio between the mesopore amount and the micropore amount is not more than the upper limit (Vm1 / Vm2 ≦ 20.0), high output characteristics can be obtained.
The mesopore volume Vm1 and the micropore volume Vm2 of the composite porous material 2 in the present embodiment are the same as those described above for the composite porous material 1, and are measured by the same method.

In the activated carbon used for forming the composite porous material 2 as the negative electrode active material, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method was calculated by V1 (cc / g) and MP method. When the amount of micropores derived from pores having a diameter of less than 20 mm is V2 (cc / g), 0.050 ≦ V1 ≦ 0.500, 0.005 ≦ V2 ≦ 1.000, and 0.2 ≦ V1 It is preferable that /V2≦20.0.
About mesopore amount V1 of activated carbon, 0.050 <= V1 <= 0.350 is more preferable, and 0.100 <= V1 <= 0.300 is still more preferable. The micropore amount V2 is more preferably 0.005 ≦ V2 ≦ 0.850, and further preferably 0.100 ≦ V2 ≦ 0.800. The ratio of mesopore amount / micropore amount is more preferably 0.22 ≦ V1 / V2 ≦ 15.0, and further preferably 0.25 ≦ V1 / V2 ≦ 10.0. When the mesopore volume V1 of the activated carbon is 0.500 or less and the micropore volume V2 is 1.000 or less, in order to obtain the pore structure of the composite porous material 2 of the present embodiment, an appropriate amount Since it is sufficient to deposit a carbon material, the pore structure tends to be easily controlled. For the same reason, when the mesopore volume V1 of the activated carbon is 0.050 or more and the micropore volume V2 is 0.005 or more, V1 / V2 is 0.2 or more and V1 / V2 is 20 Even if it is 0.0 or less, the pore structure of the composite porous material 2 of the present embodiment can be easily obtained from the pore distribution of the activated carbon.
The average particle size, the hydrogen atom / carbon atom number ratio (H / C), and the crystal structure of the composite porous material 2 in the present embodiment have been described above for the composite porous material 1, respectively. It is used as it is.

-Other carbon materials-
Examples of other carbon materials that may be contained as the negative electrode active material in the negative electrode active material layer include amorphous carbonaceous materials such as graphite, graphitizable carbon materials, non-graphitizable carbon materials, polyacene-based materials, and carbon nanotubes. , Fullerenes, carbon nanophones, fibrous carbonaceous materials, etc., which do not fall under any of the composite porous materials 1 and 2 described above.
When the negative electrode active material contains other carbon materials, the use ratio of the other carbon materials is preferably 50% by mass or less, and preferably 20% by mass or less with respect to the total of the carbon materials. More preferred.

[Optional components in the negative electrode active material layer]
The negative electrode active material layer of the negative electrode body for a non-aqueous lithium storage element of the present invention can contain a conductive filler, a binder, etc. in addition to the negative electrode active material, if necessary.
The type of the conductive filler is not particularly limited, and examples thereof include acetylene black, ketjen black, and vapor grown carbon fiber. The addition amount of the conductive filler is preferably 0 to 30% by mass with respect to the negative electrode active material.

Although it does not restrict | limit especially as a binder, For example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), a styrene-butadiene copolymer etc. can be used. At this time, the peel strength and electrical conductivity of the negative electrode body can be controlled by changing the amount and type of the binder.
The greater the amount of the binder, the greater the peel strength of the negative electrode body and the higher the electrical conductivity. That is, in order to maintain the electrical conductivity and peel strength of the negative electrode body, it is required to add a minimum amount of binder. However, if the amount of the binder is increased too much, the events during the nail penetration test increase. For this reason, the amount of the binder is preferably suppressed within a certain range.
A preferable addition amount of the binder varies depending on the kind of the binder, and the peel strength of the negative electrode body should be appropriately adjusted within a range where the predetermined effect of the present invention is exhibited.
For example, when PVdF is used as a binder, the amount of PVdF added is preferably 4 to 8% by mass, more preferably 4.5 to 7.8% by mass, particularly preferably relative to the negative electrode active material. 5 to 7.5% by mass. When the amount of PVdF is 4% by mass or more, the electrical conductivity between the negative electrode active materials can be maintained, and the power storage element can be manufactured without peeling off the active material. Moreover, if the amount of PVdF is 8% by mass or less, the cell heating temperature during the nail penetration test can be suppressed. As a result, a safer non-aqueous lithium storage element can be provided.

[Manufacture of negative electrode body]
The negative electrode body is formed by providing an active material layer on one side or both sides of a negative electrode current collector. In a typical embodiment, the negative electrode active material layer is fixed to the negative electrode current collector.
In the negative electrode active material layer in the negative electrode body for a non-aqueous lithium-type storage element of the present invention, in addition to the negative electrode active material, if necessary, a conductive filler and a binder are mixed with a solvent to form a slurry. It is obtained by applying to one or both sides of the negative electrode current collector and drying the solvent.
The negative electrode body can be manufactured by known electrode manufacturing techniques such as a lithium ion battery and an electric double layer capacitor. For example, various materials including a negative electrode active material are made into a slurry form with water or an organic solvent, this slurry is coated on a negative electrode current collector and dried, and then pressed at room temperature or under heating as necessary to form a negative electrode active material layer Is obtained. Without using a solvent, various materials including a negative electrode active material can be dry-mixed, the obtained mixture can be press-molded, and then attached to the negative electrode current collector using a conductive adhesive.

The thickness of the negative electrode active material layer is preferably 20 μm or more and 45 μm or less, more preferably 25 μm or more and 40 μm or less per side. If this thickness is 20 μm or more, good charge / discharge capacity can be exhibited. On the other hand, if the thickness is 45 μm or less, the energy density can be increased by reducing the cell volume. In the case of using the composite porous material 1 as the negative electrode active material, the thickness of the negative electrode active material layer is preferably 20 μm or more and 45 μm or less, more preferably 20 to 40 μm, from the viewpoint of the resistance of the negative electrode, More preferably, it is 25-35 micrometers.
When the current collector has holes, the thickness of the negative electrode active material layer means the average value of the thickness per one side of the portion of the current collector that does not have holes.
When the bulk density of the negative electrode active material layer is 0.30 g / cm ³ or more, the capacity of the electrode per volume can be increased, and the storage element can be reduced in size. The bulk density of the negative electrode active material layer is more preferably 0.60 g / cm ³ or more, particularly preferably 0.70 g / cm ³ from the viewpoint of expressing good conductivity between the active materials and maintaining high strength. cm ³ or more.

[Pre-doping of negative electrode active material]
The negative electrode active material is preferably predoped with lithium ions. The recommended amount of pre-doping in the present embodiment is as follows.
For example, in the case of the composite porous material 1, the pre-doping amount is preferably 1,050 mAh / g or more and 2,050 mAh / g or less, more preferably 1,100 mAh / g or more per unit mass of the composite porous material 1. It is 2,000 mAh / g or less, More preferably, it is 1,200 mAh / g or more and 1,700 mAh / g or less, Especially preferably, it is 1,300 mAh / g or more and 1,600 mAh / g or less. For example, in the case of the composite porous material 2, the pre-doping amount is preferably 700 mAh / g or more and 1500 mAh / g or less, more preferably 750 mAh / g or more and 1,300 mAh per unit mass of the composite porous material 2. / G or less.

By pre-doping lithium ions into the negative electrode active material, the negative electrode potential is lowered, the cell voltage when this is combined with the positive electrode is increased, and the utilization capacity of the positive electrode is increased. Therefore, capacity and energy density are increased.
In the case of the composite porous material 1, if the amount of pre-doping exceeds 1,050 mAh / g, lithium ions are well pre-doped at irreversible sites that cannot be desorbed once lithium ions in the negative electrode material are inserted. Furthermore, the amount of the negative electrode active material relative to the desired amount of lithium can be reduced. Therefore, the negative electrode film thickness can be reduced, and high durability, good output characteristics, and high energy density can be obtained. Further, as the pre-doping amount increases, the negative electrode potential decreases, and the durability and energy density improve. If the pre-doping amount is 2,050 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal occur.
In the case of the composite porous material 2, if the amount of pre-doping exceeds 700 mAh / g, high durability, high output characteristics, and high energy density can be obtained for the same reason as described above. If it is 500 mAh / g or less, there is no possibility that side effects such as precipitation of lithium metal occur.

As a method for pre-doping lithium ions into the negative electrode active material, a known method can be used. For example, after forming a negative electrode active material into an electrode body, using the negative electrode as a working electrode and metallic lithium as a counter electrode, an electrochemical cell combining non-aqueous electrolyte is prepared, and lithium ions are electrochemically pre-doped. The method of doing is mentioned. Moreover, it is also possible to pre-dope lithium ions into the negative electrode active material by pressing a metal lithium foil on the negative electrode body and placing it in a non-aqueous electrolyte.
By doping lithium ions into the negative electrode active material, it is possible to satisfactorily control the capacity and operating voltage of the obtained power storage element.

<Non-aqueous lithium storage element>
The nonaqueous lithium storage element of the present invention is formed by housing the negative electrode body as described above, the electrode laminate including the positive electrode body and the separator, and the nonaqueous electrolyte solution in an exterior body.
The non-aqueous lithium storage element according to the present embodiment achieves high safety by suppressing heat generation and ignition during a nail penetration test, as will be specifically verified in the examples described later. The output can be maintained.

<Positive electrode body>
The positive electrode body in the non-aqueous lithium storage element of this embodiment has a positive electrode current collector and a positive electrode active material layer including a positive electrode active material provided on one or both surfaces of the positive electrode current collector. .

[Positive electrode current collector]
As the positive electrode current collector, a general current collector usually used in a power storage element can be used. The positive electrode current collector is preferably a metal foil that does not deteriorate due to elution into the electrolytic solution, reaction with the electrolytic solution, or the like. There is no restriction | limiting in particular as such metal foil, For example, copper foil, aluminum foil, etc. are mentioned. In the power storage device of this embodiment, it is preferable that the positive electrode current collector be an aluminum foil and the negative electrode current collector be a copper foil.
The positive electrode current collector may be a metal foil having no holes, or may be a metal foil having a through hole (for example, a punched metal through hole) or an open part (for example, an expanded metal hole).
The thickness of the positive electrode current collector is not particularly limited, but is preferably 1 to 100 μm. A thickness of the positive electrode current collector of 1 μm or more is preferable because the shape and strength of the positive electrode body formed by fixing the positive electrode active material layer to the positive electrode current collector can be maintained. On the other hand, when the thickness of the positive electrode current collector is 100 μm or less, the weight and volume as the power storage element are appropriate, and the performance per weight and volume tends to be high, which is preferable.

[Positive electrode active material layer]
(Positive electrode active material)
The positive electrode active material preferably contains activated carbon. As the positive electrode active material, only activated carbon may be used, or other materials as described later may be used in combination with activated carbon.
There are no particular restrictions on the type of activated carbon and its raw material in the positive electrode active material, but it is preferable to optimally control the pores of the activated carbon in order to achieve both high input / output characteristics and high energy density. Specifically, the amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is V1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is calculated. In order to obtain a high energy density when V2 (cc / g) is satisfied, 0.8 <V1 ≦ 2.5 and 0.8 <V2 ≦ 3.0 are satisfied, and the BET method is used. Activated carbon (hereinafter also referred to as “activated carbon 1”) having a specific surface area of 3,000 m ² / g or more and 4,000 m ² / g or less is preferable. When the BET specific surface area is 3,000 m 2 / g or more, a good energy density is easily obtained. On the other hand, when the BET specific surface area is 4,000 m ² / g or less, there is no need to add a large amount of binder in order to maintain the strength of the electrode, so that the performance per electrode volume tends to be high. A more preferable value of the BET specific surface area of the activated carbon 1 is 3,200 m ² / g or more and 3,800 m ² / g or less.

The activated carbon 1 having the mesopore volume V1 and the micropore volume V2 described above has a higher BET specific surface area than the activated carbon used for the conventional electric double layer capacitor or lithium ion capacitor.
The micropore amount V2 of the activated carbon 1 is preferably a value larger than 0.8 cc / g in order to increase the specific surface area of the activated carbon and increase the capacity. Moreover, it is preferable that it is 3.0 cc / g or less from a viewpoint of increasing the density as an electrode of activated carbon and increasing the capacity | capacitance per unit volume. V2 is more preferably greater than 1.0 cc / g and not greater than 2.5 cc / g, and still more preferably not less than 1.5 cc / g and not greater than 2.5 cc / g. The micropore volume V1 and the mesopore volume V2 are the same as those described above for the micropore volume Vm1 and the mesopore volume Vm2 in the composite porous material 1, and are measured by the same method.

The activated carbon 1 having the above-described characteristics can be obtained using, for example, a raw material (carbon source) and a processing method described below.
The carbon source used as a raw material for the activated carbon 1 is not particularly limited as long as it is a carbon source that is normally used as a raw material for activated carbon. For example, plant-based materials such as wood, wood flour, and coconut shells; fossil-based materials such as petroleum pitch and coke; phenol resin, furan resin, vinyl chloride resin, vinyl acetate resin, melamine resin, urea resin, resorcinol resin, etc. Examples include synthetic resins. Among these raw materials, phenol resin and furan resin are suitable for producing activated carbon 1 having a high specific surface area, and are particularly preferable.
Examples of a method for carbonizing these raw materials or a heating method at the time of activation treatment include known methods such as a fixed bed method, a moving bed method, a fluidized bed method, a slurry method, and a rotary kiln method. The atmosphere at the time of heating is an inert gas such as nitrogen, carbon dioxide, helium, or argon, or a gas mixed with other gases containing these inert gases as a main component. The carbonization temperature is generally about 400 to 700 ° C., and the method of firing for about 0.5 to 10 hours is common.

As the activation method of the carbide after the carbonization treatment, for example, a gas activation method in which firing is performed using an activation gas such as water vapor, carbon dioxide, oxygen, or an alkali metal activation method in which heat treatment is performed after mixing with an alkali metal compound is possible. However, the alkali metal activation method is preferable for producing activated carbon having a high specific surface area. In this activation method, a carbide and an alkali metal compound such as KOH or NaOH are mixed at a mass ratio of carbide: alkali metal compound of 1: 1 or more (the amount of the alkali metal compound is equal to or more than the amount of the carbide). A large amount), followed by heating in the range of 600 to 900 ° C. in an inert gas atmosphere for 0.5 to 5 hours, and then washing and removing the alkali metal compound with acid and water, followed by drying. I do.
In order to increase the amount of micropores and not increase the amount of mesopores, it is preferable to mix with KOH with a larger amount of carbides during activation. In order to increase the amount of any hole, it is preferable to use a large amount of KOH. In order to mainly increase the amount of mesopores, it is preferable to perform water vapor activation after alkali activation treatment.

The average particle diameter of the activated carbon 1 is preferably 1 μm or more and 30 μm or less. More preferably, they are 2 micrometers or more and 20 micrometers or less.
The positive electrode active material may include a material other than activated carbon 1 (for example, activated carbon not having the specific V1 and / or V2, or a material other than activated carbon (for example, a composite oxide of lithium and a transition metal)). Good. In the illustrated embodiment, the content of the activated carbon 1 is preferably more than 50% by mass of the total positive electrode active material, more preferably 70% by mass or more, still more preferably 90% by mass or more, and most preferably 100% by mass. preferable.

(Other ingredients)
The positive electrode active material layer can contain a conductive filler (for example, carbon black), a binder, and the like as necessary.
0-30 mass parts is preferable with respect to 100 mass parts of active materials, and, as for the usage-amount of an electroconductive filler, 1-20 mass parts is more preferable. From the viewpoint of high power density, it is preferable to use a conductive filler. However, when the amount used is 30 parts by mass or less, the proportion of the amount of the positive electrode active material in the positive electrode active material layer increases, This is preferable because the output density tends to increase.
In the positive electrode active material layer, a binder is used for fixing the positive electrode active material and the conductive filler used as necessary on the positive electrode current collector as the positive electrode active material layer. As this binder, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), fluororubber, styrene butadiene copolymer, cellulose derivative and the like can be used. The amount of the binder used is preferably in the range of 3 to 20 parts by mass and more preferably in the range of 5 to 15 parts by mass with respect to 100 parts by mass of the positive electrode active material. A binder does not cover the surface of a positive electrode active material as the said usage-amount of a binder is 20 mass parts or less. Accordingly, it is preferable because ions enter and leave the active material layer quickly and a high power density tends to be obtained. On the other hand, it is preferable that the amount of the binder used is 3 parts by mass or more because the positive electrode active material layer tends to adhere to the positive electrode current collector.

The thickness of the positive electrode active material layer is preferably 15 μm or more and 100 μm or less, more preferably 20 μm or more and 85 μm or less per side. When the thickness is 15 μm or more, an energy density sufficient as a capacitor can be expressed. On the other hand, if this thickness is 100 μm or less, high input / output characteristics as a capacitor can be obtained. When the current collector has holes, the thickness of the positive electrode active material layer means the average value of the thickness per one side of the portion of the current collector that does not have holes.
When the bulk density of the positive electrode active material layer is 0.30 g / cm ³ or more, the capacity of the electrode per volume can be increased, and downsizing of the energy storage device can be achieved. Further, in order to further increase the charge-discharge characteristics at high current, more preferable to be 0.70 g / cm ³ or less, and particularly preferably 0.65 g / cm ³ or less.

An anchor layer may be provided between the positive electrode current collector and the positive electrode active material layer. The reason why the anchor layer is formed is that the anchor layer is formed to improve the adhesive strength between the positive electrode current collector and the positive electrode active material layer, and as a result, the conduction between the two is improved and the output characteristics are excellent. This is to make it possible to obtain a body. Therefore, the conditions required for the anchor layer are as follows: first, the anchor layer itself has high strength, second, the anchor layer itself has high conductivity, and third, the anchor layer and the positive electrode active material. It is mentioned that the interface with the layer has strong adhesive strength.
Therefore, it is preferable to use a mixture of two types of conductive carbon particles of different sizes as the conductive carbon of the anchor layer. Accordingly, the strength of the anchor layer itself can be kept high even if the amount of the binder is small, and the anchor layer itself has high conductivity by decreasing the amount of the binder. Furthermore, the roughness of the anchor layer surface is increased. As a result, the interface between the anchor layer and the positive electrode active material layer has a strong adhesive strength, and can sufficiently satisfy the above three conditions required for the anchor layer.
Examples of the two types of conductive carbon particles include first conductive carbon particles having an average particle diameter of 20 nm or more and less than 1 μm,
A mixture with second conductive carbon particles having an average particle diameter of 1 μm or more and less than 15 μm is preferable.

(Method for producing positive electrode body)
The positive electrode body is formed by providing an active material layer on one side or both sides of a current collector. In a typical embodiment, the active material layer is fixed to the current collector.
The positive electrode body can be manufactured by an electrode manufacturing technique such as a known lithium ion battery or an electric double layer capacitor. For example, various materials including an active material are made into a slurry form with water or an organic solvent, this slurry is applied onto a current collector and dried, and then pressed at room temperature or under heating as necessary to form an active material layer. Can be obtained. Without using a solvent, various materials including an active material can be dry-mixed, and the obtained mixture can be press-molded and then attached to a current collector using a conductive adhesive.

<Electrolyte>
The non-aqueous electrolyte solution used for the electricity storage device of the present invention may be any non-aqueous liquid containing a lithium ion-containing electrolyte. Such a non-aqueous liquid may contain an organic solvent. Examples of such organic solvents include cyclic carbonates represented by ethylene carbonate (EC) and propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (MEC). A chain carbonate ester; a lactone such as γ-butyrolactone (γBL); and a mixed solvent thereof.
As the lithium ion-containing electrolyte () dissolved in these non-aqueous liquids, for example, lithium salts such as LiBF ₄ and LiPF ₆ can be used. The salt concentration of the electrolytic solution is preferably in the range of 0.5 to 2.0 mol / L. At 0.5 mol / L or more, sufficient anions are present, and the capacity of the energy storage device is maintained. On the other hand, at 2.0 mol / L or less, the salt is sufficiently dissolved in the electrolytic solution, and appropriate viscosity and conductivity of the electrolytic solution are maintained.

[Separator]
The positive electrode body and the negative electrode body molded as described above are laminated or wound around via a separator to form an electrode laminate having a positive electrode body, a negative electrode body, and a separator.
As the separator, a polyethylene microporous film or a polypropylene microporous film used in a lithium ion secondary battery, a cellulose nonwoven paper used in an electric double layer capacitor, or the like can be used.
The thickness of the separator is preferably 10 μm or more and 50 μm or less. A thickness of 10 μm or more is preferable because self-discharge due to an internal micro short circuit tends to be small. On the other hand, the thickness of 50 μm or less is preferable because the output characteristics of the electricity storage element tend to be high.

[Exterior body]
A metal can, a laminate film, or the like can be used as the exterior body.
As said metal can, the thing made from aluminum is preferable.
The laminate film is preferably a film in which a metal foil and a resin film are laminated, and an example of a three-layer structure comprising an outer layer resin film / metal foil / interior resin film is exemplified. The outer layer resin film is for preventing the metal foil from being damaged by contact or the like, and a resin such as nylon or polyester can be suitably used. The metal foil is for preventing the permeation of moisture and gas, and foils of copper, aluminum, stainless steel and the like can be suitably used. The interior resin film protects the metal foil from the electrolyte contained in the interior and is used for melting and sealing at the time of heat sealing the exterior body. Polyolefin, acid-modified polyolefin, and the like can be suitably used.

<Performance of non-aqueous lithium storage element>
[Nail penetration test]
The non-aqueous lithium electricity storage device of this embodiment has high safety, and is excellent in, for example, the results of a nail penetration test.
In the present embodiment, in the nail penetration test, the heat generation temperature on the surface of the electricity storage element is measured with a thermocouple, and the presence or absence of ignition is examined visually.
When a nail pierces a power storage element (for example, a laminate type power storage element), the element is short-circuited to generate a large current and generate heat. At this time, if the heat generation temperature is high, it may ignite in some cases. The maximum temperature achieved during heat generation is preferably 150 ° C. or lower, more preferably 130 ° C. or lower, and particularly preferably 100 ° C. or lower. If the maximum temperature reached during heat generation is 150 ° C. or lower, the risk of fire when nailing is extremely small, and therefore it can be determined that the safety is higher.

The heat generation temperature of the power storage element in the present embodiment is the surface temperature of the power storage element when the nail penetration test is performed under a test environment of an environmental temperature of 25 ° C. and a closed system. For the nail penetration test, a nail having a diameter of 2.5 mm, a length of 60 mm, and carbon tool steel (SK) is used. The nail penetration speed is set to 10 mm / s.
The storage element used for the nail penetration test is charged at a constant current until reaching 4.0V at a current value of 1.5C immediately before the test is performed, and then applied at a constant voltage of 4.0V. Are used for a total of 2 hours. The voltage of the electricity storage element and the surface temperature of the laminate are measured in 0.01s increments from just before the nail penetration to 30 minutes after the nail penetration, and the state of the electricity storage element during the nail penetration is visually observed. Observe and check for ignition.

[Initial performance]
The initial performance of the non-aqueous lithium storage element of the present invention can be evaluated by the capacitance F, the internal resistance R, and the time constant R / F.
Capacitance F (F) is a constant current and constant voltage charge with a constant voltage charge time of 1 hour at a current value of 1.5 C, and then a current of 1.5 C up to 2.2 V. The value is calculated from F = Q / (3.8−2.2) from the capacity Q when constant current discharge is performed. The internal resistance R (Ω) is a value obtained by the following method. First, at 25 ° C., constant current charging is performed until a voltage of 3.8 V is reached at a current value of 1.5 C, and then constant current constant voltage charging in which a constant voltage of 3.8 V is applied is performed for a total of 2 hours. Subsequently, a constant current discharge is performed up to 2.2 V at a current value of 50 C, and a discharge curve (time-voltage curve) is obtained. In this discharge curve, when the voltage at the discharge time = 0 second obtained by extrapolating from the voltage values at the time of the discharge time of 1 second and 2 seconds by linear approximation is E0, the drop voltage (ΔE) = 3. 8-E0, and R = ΔE / (50C (current value)). The time constant (ΩF) is a value R · F obtained from the product of the capacitance F (F) and the internal resistance R (Ω).

  Examples and Comparative Examples are shown below to further clarify the features of the present invention, but the present invention is not limited to the Examples.

<Example 1>
[Preparation of negative electrode body]
About commercially available coconut shell activated carbon, pore distribution was measured using nitrogen as an adsorbate using a pore distribution measuring device (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics. Using the desorption side isotherm, the mesopore amount was determined by the BJH method, and the micropore amount was determined by the MP method. As a result, the mesopore volume was 0.198 cc / g, the micropore volume was 0.695 cc / g, V1 / V2 = 0.29, and the average pore diameter was 21.2 mm. The BET specific surface area determined by the BET 1-point method was 1,780 m ² / g.
150 g of this activated carbon is placed in a stainless steel mesh basket, placed on a stainless steel bat containing 150 g of coal-based pitch (softening point: 90 ° C.), and placed in an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm). It installed and heat-processed and the composite porous material 1 was obtained. This heat treatment was performed in a nitrogen atmosphere, and the temperature was raised to 630 ° C. in 2 hours and kept at the same temperature for 4 hours. Subsequently, after cooling to 60 ° C. by natural cooling, the composite porous material 1 was taken out from the furnace.
This composite porous material 1 has a mass ratio of the deposited carbonaceous material to activated carbon of 38 mass%, a BET specific surface area of 434 m ² / g, a mesopore volume (Vm1) of 0.220 cc / g, and a micropore volume. (Vm2) was 0.149 cc / g. Furthermore, it was 2.88 micrometers as a result of measuring an average particle diameter using the Shimadzu Corporation laser diffraction type particle size distribution measuring apparatus (SALD-2000J).
86.4 parts by mass of composite porous material 1 obtained above, 8.6 parts by mass of acetylene black, 5.0 parts by mass of PVDF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed. To obtain a slurry. The obtained slurry was applied on both sides of the etched copper foil, dried and pressed to obtain a negative electrode body having a negative electrode active material layer with a thickness of 30 μm on one side.

[Preparation of positive electrode body]
The phenol resin was carbonized in a baking furnace at 600 ° C. for 2 hours in a nitrogen atmosphere. The fired product obtained was pulverized with a ball mill and classified to obtain a carbide having an average particle size of 7 μm.
This carbide and KOH were mixed at a mass ratio of 1: 5, and activated by heating in a firing furnace at 800 ° C. for 1 hour in a nitrogen atmosphere. Next, after stirring and washing in dilute hydrochloric acid adjusted to a concentration of 2 mol / L for 1 hour, boiling and washing in distilled water until stable between pH 5 and 6, followed by drying to produce activated carbon 1. .
When the mesopore volume and the micropore volume of this activated carbon 1 were measured in the same manner as in Example 1, the mesopore volume V1 was 1.50 cc / g, the micropore volume V2 was 2.28 cc / g, and the BET specific surface area was 3 627 m @ 2 / g.
80.8 parts by mass of this activated carbon 1, 6.2 parts by mass of ketjen black, 10 parts by mass of PVDF (polyvinylidene fluoride), 3.0 parts by mass of PVP (polyvinylpyrrolidone), and NMP (N-methyl) Pyrrolidone) was mixed to obtain a slurry. The obtained slurry was applied to one or both sides of a current collector made of an aluminum foil having a thickness of 15 μm, dried and pressed to obtain a positive electrode body having a positive electrode active material layer thickness of 55 μm per side. It was.

[Preparation of electrolyte]
An electrolyte solution was prepared by dissolving LiPF ₆ in an amount of 1 mol / L in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 4.

[Assembly of storage element]
The double-sided negative electrode body obtained above was cut into 50 mm × 100 mm. An amount of lithium metal foil corresponding to 1,500 mAh / g per unit mass of the composite porous material 1 was attached to one side of the negative electrode body after cutting.
The positive electrode body obtained above was cut into 50 mm × 100 mm.
A single-sided positive electrode body is used for the uppermost surface and the lowermost surface, and further, 5 double-sided negative electrode bodies and 4 double-sided positive electrode bodies are used, and a cellulose nonwoven fabric separator (that is, between the negative electrode body and the positive electrode body) , 11 sheets in total). Thereafter, electrode terminals were connected to the negative electrode body and the positive electrode body to form an electrode laminate. The laminated body was inserted into an outer package made of a laminate film, and the non-aqueous electrolyte solution was injected to seal the outer package, thereby assembling a non-aqueous lithium storage element.

[Initial performance evaluation]
<Measurement of capacitance>
The electricity storage device manufactured as described above is charged to 4 V by constant current and constant voltage charging in which a constant voltage charging time is secured for 1 hour at a current value of 3 C, and then constant current at a current value of 3 C up to 2 V. Discharge was performed. The electrostatic capacity F of this electricity storage element calculated | required by the calculation according to F = Q / (4.0-2.0) from the capacity | capacitance Q and voltage change in that case was 110F.

<Measurement of internal resistance>
The electricity storage device manufactured as described above is subjected to constant current charging until reaching 4.0 V at a current value of 3 C, and then constant current constant voltage charging in which a constant voltage of 4.0 V is applied is 2 in total. Went for hours.
Subsequently, a constant current is discharged to 2.0 V at a current value of 130 C, and is obtained by extrapolating by linear approximation from the voltage value at the time point of discharge time 1 second and 2 seconds of the obtained discharge curve (time-voltage). The internal resistance R was calculated by the internal resistance R = ΔE / (130C (current value)) from the voltage drop (ΔE) = 4.0−E0 when the voltage at discharge time = 0 seconds was E0. . The time constant determined as the product of the capacitance F and the internal resistance R was 1.50ΩF.

[Nail penetration test]
A nail penetration test was carried out on the non-aqueous lithium storage element produced as described above.
First, the battery was charged to 4.0 V at a current value of 2 C, and then charged with constant current and constant voltage of 4.0 V for 2 hours. A thermocouple was affixed to the center of one surface of the storage element after charging with a polyimide tape, and was set in a thermostat in an atmospheric atmosphere.
The voltage and temperature were measured when the nail speed of 10 mm / s was set and a nail having a diameter of 2.5 mm was inserted into the electricity storage device.
When a nail was pierced into the storage element, a short circuit occurred, the voltage of the storage element became 0 V, and heat generation occurred. The maximum value of the surface temperature of the electricity storage device at this time was 80 ° C.
When the N number was set to 5 and the test was repeated, the number of power storage elements that ignited during nail penetration was 0 out of 5.

[Electric conductivity measurement]
The electrical conductivity of the negative electrode body (not doped) produced as described above was measured.
First, the negative electrode body is cut into a size of 70 mm × 320 mm, and the electric conductivity at the positions of (X, Y) = (35 mm, 90 mm), (35 mm, 160 mm), and (35 mm, 230 mm) is measured by four probes. The average value was calculated. For the measurement, a low resistivity meter (Loresta GP) manufactured by Mitsubishi Analytech Co., Ltd. was used. For the change in electric field energy that occurs in the vicinity of the sample end, a correction coefficient was calculated by solving Poisson's equation under a predetermined condition, and a more correct value was calculated using this coefficient.
As a result, the electrical conductivity S / cm of the negative electrode body of Example 1 was 53,800 S / cm.

[Negative electrode peel strength measurement]
The peel strength of the negative electrode body before and after assembling the electricity storage element was measured using a tensile tester (STB-1225S) manufactured by A & D.

(Peel strength before assembly)
First, the negative electrode body (not doped) prepared as described above was cut into a size of 2.5 cm × 10 cm, and the electrode body surface was made of Nichiban Co., Ltd. cello tape (registered trademark, width 24 mm, length). 100 mm). After affixing the tape, peel off about 5 mm at the end, and attach the tape side to the upper side (tensile side) of the tensile tester and the electrode side to the lower side (fixed side) of the tensile tester. The film was pulled 100 mm in the direction of 50 mm / min. Data obtained by adopting an integrated average load of 25 mm to 65 mm of the obtained strength.
When the peel strengths of the front surface and the back surface were measured at N = 3, the average value of all was 0.08 N / cm.

(Peel strength after assembly)
The peel strength of the negative electrode body after assembling the electricity storage element was measured in the same manner as described above. The assembled storage element was disassembled, the negative electrode body was taken out, cut into 2.5 cm × 10 cm, and used as a sample for measurement.
When the peel strengths of the front surface and the back surface were measured at N = 3, the average value of all was 0.07 N / cm.

<Examples 2 to 5 and Comparative Examples 1 and 2>
The single-sided thickness of the negative electrode active material layer was 30 μm in the same manner as in Example 1 except that the composite porous material 1, acetylene black, and PVDF (polyvinylidene fluoride) were used as shown in Table 1. The negative electrode body was obtained. In Comparative Example 1, the storage element could not be assembled due to poor binding of the negative electrode active material layer.
Various evaluations were performed in the same manner as in Example 1 except that this negative electrode body was used.
The evaluation results are shown in Table 2.

<Example 6>
[Preparation of negative electrode body]
About commercially available coconut shell activated carbon, pore distribution measuring apparatus (AUTOSORB-1 AS-1-MP) manufactured by Yuasa Ionics Co., Ltd. was used and nitrogen distribution was measured as an adsorbate. Using the desorption side isotherm, the mesopore volume was determined by the BJH method, and the micropore volume was determined by the MP method. As a result, the mesopore volume was 0.198 cc / g, the micropore volume was 0.695 cc / g, V1 / V2 = 0.29, and the average pore diameter was 21.2 mm. The BET specific surface area determined by the BET 1-point method was 1,780 m ² / g.
150 g of this coconut shell activated carbon is placed in a stainless steel mesh basket, placed on a stainless steel bat containing 270 g of a coal-based pitch (softening point: 50 ° C.), and an electric furnace (effective size in the furnace 300 mm × 300 mm × 300 mm) The composite porous material 2 was obtained by performing heat treatment. This heat treatment was performed in a nitrogen atmosphere, and the temperature was raised to 600 ° C. in 8 hours and held at that temperature for 4 hours. Then, after cooling to 60 degreeC by natural cooling, the composite porous material 2 used as a negative electrode material was taken out from the furnace.
The obtained composite porous material 2 has a BET specific surface area of 262 m ² / g, a mesopore volume (Vm1) of 0.1798 cc / g, a micropore volume (Vm2) of 0.0843 cc / g, and Vm1 / Vm2 = 2. .13.
85.6 parts by mass of the composite porous material 2, 8.5 parts by mass of acetylene black, 5.9 parts by mass of PVDF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) are mixed to form a slurry. Got. The obtained slurry was applied on both sides of the etched copper foil, dried and pressed to obtain a negative electrode body having a negative electrode active material layer with a thickness of 60 μm on one side.

[Assembly and evaluation of storage element]
The double-sided negative electrode body obtained above was cut into 50 mm × 100 mm. An amount of lithium metal foil corresponding to 760 mAh / g per unit mass of the composite porous material 2 was attached to one side of the negative electrode body after cutting.
A storage element was assembled in the same manner as in Example 1 except that the above-described negative electrode body was used, and various evaluations were performed.
The evaluation results are shown in Table 2.

<Examples 7 to 9 and Comparative Examples 3 and 4>
[Preparation of negative electrode body]
The amount of composite porous material 2, acetylene black, and PVDF (polyvinylidene fluoride) used, and the single-sided thickness of the negative electrode active material layer were as described in Table 1, respectively, as in Example 6, A negative electrode body having a thickness of one side of the negative electrode active material layer of 60 μm was obtained.
Various evaluations were performed in the same manner as in Example 1 except that this negative electrode body was used. In Comparative Example 3, the power storage element could not be assembled due to poor binding of the negative electrode active material layer.
The evaluation results are shown in Table 2.

  The power storage element using the negative electrode body for a power storage element of the present invention can be suitably used in fields such as a hybrid drive system application in an automobile and an instantaneous power peak assist application.

Claims (6)

A negative electrode current collector and a negative electrode active material layer provided on one or both surfaces of the negative electrode current collector,
A negative electrode for a non-aqueous lithium storage element, wherein a peel strength when peeling the negative electrode active material layer from the negative electrode current collector is in a range of 0.05 N / cm or more and 0.60 N / cm or less. body.   The negative electrode body for a nonaqueous lithium storage element according to claim 1, wherein the negative electrode current collector has a through hole. The negative electrode active material is a composite porous material in which a carbon material is deposited on the surface of activated carbon; and
The amount of mesopores derived from pores having a diameter of 20 to 500 mm calculated by the BJH method is Vm1 (cc / g), and the amount of micropores derived from pores having a diameter of less than 20 mm calculated by the MP method is Vm2 (cc / g ), 0.010 ≦ Vm1 ≦ 0.250, 0.001 ≦ Vm2 ≦ 0.200, and 1.5 ≦ Vm1 / Vm2 ≦ 20.0 are satisfied. A negative electrode body for a lithium storage element. The negative electrode active material is a composite porous material in which a carbon material is deposited on the surface of activated carbon; and
Lithium ions of 1,050 mAh / g or more and 2,050 mAh / g or less per unit mass of the composite porous material are pre-doped,
3. The non-aqueous lithium according to claim 1, wherein a mass ratio of the carbonaceous material to the activated carbon is 10% or more and 60% or less, and a thickness of the negative electrode active material layer is 20 μm or more and 45 μm or less per side. -Type electrode element negative electrode body. The electrode laminate including the negative electrode body for a non-aqueous lithium storage element according to any one of claims 1 to 4, a positive electrode body, and a separator, and a non-aqueous electrolyte solution are housed in an exterior body,
The positive electrode body includes a positive electrode current collector and a positive electrode active material layer including a positive electrode active material provided on one or both surfaces of the positive electrode current collector, and the positive electrode active material includes activated carbon. A non-aqueous lithium-type electricity storage device characterized by the above. The mesopore amount V1 (cc / g) derived from pores having a diameter of 20 to 500 mm calculated by the BJH method satisfies 0.8 <V1 ≦ 2.5, and the activated carbon is less than 20 mm in diameter calculated by the MP method. The amount of micropores V2 (cc / g) derived from the above pores satisfies 0.8 <V2 ≦ 3.0, and the specific surface area measured by the BET method is 3,000 m ² / g or more and 4,000 m ^2. The non-aqueous lithium storage element according to claim 5, which shows / g or less.