JP2002313348A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide highly safe nonaqueous electrolyte secondary battery having superior cycle characteristics, charge and discharge characteristics and heat radiating characteristics, capable of excellently keeping an initial external form because there is no risk of deformation of the external form caused by a swelling even if charge and discharge is repeatedly carried out. SOLUTION: In this nonaqueous secondary battery, a positive electrode active material layer 1 is disposed face to face with a negative electrode active material layer 2 through a sheet-like porous separator 3, and these positive electrode active material layer 1, the negative electrode active material layer 2, and the porous separator 3 are held between collectors 4 from the outside by the elasticity of the collector having a collector plate 4a and a bonded part 4b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a secondary battery,
More specifically, the present invention relates to a stacked secondary battery using a non-aqueous electrolyte such as a lithium secondary battery or a lithium ion secondary battery.

[0002]

2. Description of the Related Art In recent years, as devices have become more portable and cordless, expectations for a non-aqueous electrolyte secondary battery having a small size, light weight, and high energy density have increased. Also, demands for larger, lighter, and higher capacity batteries are increasing. This non-aqueous electrolyte secondary battery
A positive electrode sheet having a structure in which a positive electrode active material layer of lithium manganate, lithium cobaltate, lithium nickelate, or the like is bonded to a sheet-like electrode, and a negative electrode active material layer of carbon or the like is bonded to a sheet-like electrode. With a structure in which a negative electrode sheet with a structure is laminated via a porous membrane separator,
Despite its small size, it has been widely studied because an electromotive force exceeding 4 V can be obtained. This nonaqueous electrolyte secondary battery is characterized by being superior to conventional secondary batteries in terms of high capacity and safety.

[0003]

The above-described non-aqueous electrolyte secondary battery has a structure in which a positive electrode sheet and a negative electrode sheet are laminated with a porous membrane separator interposed therebetween.
During repeated charging and discharging, the outer shape is deformed due to swelling, and the initial outer shape cannot be maintained well. In addition, when the cycle characteristics are evaluated by measuring the capacity retention ratio after charging and discharging,
Since the capacity retention ratio tends to gradually decrease as charging / discharging is repeated, there is a problem in that deterioration is caused during repeated charging / discharging, and a sufficient electromotive force cannot be obtained. Further, in the conventional electrode structure, charge and discharge characteristics and heat radiation characteristics were not sufficient, so that heat was easily stored, which was one of the causes of lowering reliability.

[0004] The present invention has been made in view of the above circumstances, and even when charging and discharging are repeatedly performed,
There is no possibility that the outer shape is deformed due to swelling, so that the initial outer shape can be favorably maintained,
Moreover, it is an object of the present invention to provide a non-aqueous electrolyte secondary battery having excellent cycle characteristics, charge / discharge characteristics, and heat radiation characteristics as well as high safety.

[0005]

Means for Solving the Problems The present inventor has made intensive studies to achieve the above object, and as a result, completed the present invention. That is, the secondary battery according to claim 1 of the present invention is:
In a secondary battery in which a positive electrode active material layer and a negative electrode active material layer are arranged to face each other, these active material layers are sandwiched by a chargeable / dischargeable current collector having a thickness capable of maintaining a shape. It is characterized by.

According to a second aspect of the present invention, there is provided a secondary battery in which a plurality of positive electrode active material layers and a plurality of negative electrode active material layers are alternately stacked in a thickness direction thereof with a porous film interposed therebetween. Each of the polar outermost active material layers is connected to a chargeable / dischargeable current collector having a thickness capable of maintaining its shape.
The plurality of active material layers are sandwiched by a pair of current collectors.

A secondary battery according to a third aspect of the present invention is the secondary battery according to the first or second aspect, wherein the current collector is a pair of plate-shaped current collectors sandwiching the plurality of active material layers. Are joined together, and the thickness of the joined portion is not less than the thickness of the plate-shaped portion.

According to a second aspect of the present invention, in the secondary battery according to the first or second aspect, the current collector is formed by bending a plate-shaped current collector to have a U-shaped cross section. The plurality of active material layers are sandwiched by elasticity of a U-shaped current collector.

A secondary battery according to a fifth aspect of the present invention is the secondary battery according to the first or second aspect, wherein the current collector has a bag shape for accommodating the plurality of active material layers. The plurality of active material layers are sandwiched by elasticity of a body.

A secondary battery according to a sixth aspect of the present invention is the secondary battery according to any one of the first to fifth aspects, wherein the current collector is a metal thin plate or a shape memory alloy thin plate. .

A secondary battery according to a seventh aspect of the present invention is the secondary battery according to the sixth aspect, wherein the metal thin plate is a copper thin plate or an aluminum thin plate.

According to an eighth aspect of the present invention, in the secondary battery according to the sixth aspect, the shape memory alloy thin plate is a Ni-Ti alloy thin plate containing nickel and titanium as main components. I do.

According to a ninth aspect of the present invention, in the secondary battery according to any one of the first to eighth aspects, the current collector has a thickness of 50 μm or more and 120 μm or less. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a secondary battery according to the present invention will be described using a nonaqueous electrolyte secondary battery as an example. First Embodiment FIG. 1 is a cross-sectional view showing a nonaqueous electrolyte secondary battery according to a first embodiment of the present invention. In the drawing, reference numeral 1 denotes a positive electrode having lithium manganate as a main active material. An active material layer 2, a negative electrode active material layer mainly composed of carbon,
Reference numeral 3 denotes a sheet-like porous membrane separator made of polyethylene or the like, 4 denotes a plate-shaped current collector which is connected to the outside of the positive electrode active material layer 1 and has a thickness capable of maintaining its shape and is chargeable and dischargeable, and 5 denotes a negative electrode active material. A chargeable / dischargeable foil-shaped current collector connected to the layer 2.

The non-aqueous electrolyte secondary battery is a prismatic battery, and this shape is merely an example, and can take various shapes depending on the difference in electromotive force and capacity. Further, the thickness differs depending on the size of the area. One end of each of a pair of rectangular current collector plates 4a sandwiching the positive electrode active material layer 1 from outside is joined to each other by welding or the like to form a joint 4b.
The central part of the terminal protrudes outward to form a rectangular terminal 6 as shown in FIG.

The current collecting plate 4a and the joint 4b
Due to the overall elasticity, the positive electrode active material layer 1 and the negative electrode active material layer 2 that are opposed to each other via the porous membrane separator 3 are sandwiched from the outside. The entirety of the positive electrode active material layer 1 to the current collector 5 except for the tip of the terminal 6 is covered with the laminate 7.

As the current collector 4, a metal thin plate or a shape memory alloy thin plate having a thickness of 50 μm or more and 120 μm or less is preferably used. As the metal thin plate, one of a copper (Cu) thin plate and an aluminum (Al) thin plate is preferable.

As the shape memory alloy thin plate, for example, an alloy capable of returning to a stored original shape by heating as necessary during the manufacturing process of the secondary battery is preferable. By repeating the above, it is more preferable that the shape memory alloy thin plate is deformed in a direction of contracting as the temperature becomes higher, and as a result, the external shape of the secondary battery is maintained in a desired shape. As a shape memory alloy, Ni-T
i-alloy, Ni-Ti-Cu alloy, Ti-In alloy and the like are preferably used.

Here, the reason why the thickness of the metal thin plate or the shape memory alloy thin plate is 50 μm or more and 120 μm or less is that if the thickness is less than 50 μm, the mechanical strength is not sufficient and the positive electrode active material layer 1 to the porous film This is because the shape of the entirety of the separator 3 and the current collector 5 cannot be maintained, and if the thickness exceeds 120 μm, processing is difficult due to being too hard.

In this non-aqueous electrolyte secondary battery, the current collector plate 4a
The positive electrode active material layer 1 to the porous membrane separator 3 and the current collector 5 are sandwiched from the outside by the elasticity of the current collector 4 having the bonding portion 4b. Can be maintained in a desired shape, and there is no possibility that deformation such as swelling due to heat generation caused by repeated charging and discharging occurs.

Further, even when an external impact or the like is applied, the above-mentioned current collector 4 protects the positive electrode active material layer 1 to the porous membrane separator 3 and the current collector 5 from external impact and the like. Since the external shape is maintained, the positive electrode active material layer 1 to the porous membrane separator 3 and the current collector 5 are not likely to be deformed or damaged even when an external impact or the like is applied.

The current collector 4 is a thin metal plate having a thickness of 50 μm or more and 120 μm or less, in particular, a Cu thin plate,
By using any one of the thin plates, there is no possibility that the capacity retention ratio is reduced even when charge and discharge are repeatedly performed in the cycle characteristic evaluation. Therefore, even if charging and discharging are repeated many times, there is no risk of deterioration, and a sufficient electromotive force can be secured. Further, since the heat radiation characteristics are excellent, heat is hardly stored, and the reliability can be improved.

Further, as the current collector 4, the shape memory alloy is deformed in a direction to be reduced as the temperature becomes higher by repeating charging and discharging, and as a result, the external shape of the secondary battery is maintained in a desired shape. When a thin plate is used, the shape memory alloy thin plate is deformed in a direction in which it shrinks in response to a change in ambient temperature, so that the external shape of the secondary battery can always be maintained in a desired shape.

In FIG. 1, the porous membrane separators 3 are arranged on both sides of the anode active material layer 2, and the cathode active material layers 1 are arranged outside each of the porous membrane separators 3, and these are sandwiched by the current collector 4. Although the positive electrode active material layer 1 and the negative electrode active material layer 2 are arranged to face each other, the porous membrane separator 3 is arranged between them, and these are sandwiched by the current collector 4.

Second Embodiment FIG. 3 is a sectional view showing a nonaqueous electrolyte secondary battery according to a second embodiment of the present invention. In the drawing, reference numeral 11 denotes the outermost positive electrode active material layer 1. A chargeable / dischargeable plate-shaped current collector having a thickness capable of maintaining the shape and connected to the cathode active material layer 12 connected to the positive electrode active material layer 1 excluding the outermost layer; Is a chargeable / dischargeable foil-shaped current collector connected to the negative electrode active material layer 2.

This non-aqueous electrolyte secondary battery has a size of 120 mm ×
This is a stacked prismatic battery having a size of 70 mm and a thickness of 1.0 mm to 5.0 mm. This shape is an example, and various shapes can be adopted depending on differences in electromotive force and capacity. Further, the thickness differs depending on the size of the area. As shown in FIGS. 3 and 4, one end of each of a pair of rectangular current collectors 11a sandwiching the outermost positive electrode active material layer 1 from outside is joined to the current collector 11 by welding or the like. The central portion of the joint 11b protrudes outward to form a rectangular terminal 6.

The current collector plate 11a and the joint 1
1b, the positive electrode active material layer 1 and the negative electrode active material layer 2
Are alternately laminated with the porous membrane separator 3 interposed therebetween.
A laminate of 0 layers (excluding the porous membrane separator 3) is sandwiched from the outside. In FIG. 3, for ease of explanation, the positive electrode active material layers 1 and the negative electrode active material
It has a layered structure. As shown in FIG. 5, the current collector 11 and the laminate are entirely covered with the laminate 7 except for the terminals 6.

As the current collector 11, a metal sheet or a shape memory alloy sheet having a thickness of 50 μm or more and 120 μm or less is preferably used, just like the current collector 4 described above.
The thickness of the current collector 11 in this case is set so as to have sufficient mechanical strength to maintain the shape of the stacked body. As the metal sheet, any of a Cu sheet and an Al sheet is preferably used, and as the shape memory alloy sheet, Ni-
Ti alloy thin plates, Ni-Ti-Cu alloy thin plates, Ti-In alloy thin plates and the like are preferably used.

In this non-aqueous electrolyte secondary battery, the current collector 11
a and the elasticity of the current collector 11 having the joint portion 11b,
Since the positive electrode active material layer 1 and the negative electrode active material layer 2 sandwich a laminated body alternately laminated via the porous membrane separator 3 from the outside, the outer shape of the secondary battery can be adjusted to a desired shape by the current collector 11. The shape can be maintained, and there is no risk of deformation such as swelling due to heat generated by repeated charge and discharge. When an external impact or the like is applied, the current collector 11 protects the laminate from external impact or the like and retains its outer shape. There is no possibility that deformation or damage will occur even in the case of the addition.

The current collector 11 has a thickness of 50 μm.
Metal sheet having a thickness of not less than 120 μm or less, in particular, a Cu sheet,
By using any of the Al thin plates, in the cycle characteristic evaluation, the capacity retention rate does not decrease even if charge and discharge are repeated. Thereby, even if charging and discharging are repeated many times, there is no possibility of deterioration, and a sufficient electromotive force is secured. Further, since the heat dissipation characteristics are excellent, heat is hardly stored, and the reliability is improved.

Further, the current collector 11 is deformed in a direction to be reduced as temperature rises by repeating charging and discharging, and as a result, a shape memory alloy which keeps the outer shape of the secondary battery in a desired shape is obtained. When a thin plate is used, the shape memory alloy thin plate is deformed in a direction in which it shrinks in response to a change in ambient temperature, so that the outer shape of the sandwiched laminate can be constantly maintained in a desired shape. As a result, In addition, the external shape of the secondary battery can always be kept in a desired shape.

Next, the non-aqueous electrolyte secondary battery of this embodiment will be described in more detail. As the positive electrode active material constituting the positive electrode active material layer 1, the above-mentioned lithium manganate is suitably used. On the other hand, as the negative electrode active material constituting the negative electrode active material layer 2, a carbon material such as lithium, a lithium alloy, graphite capable of occluding and releasing lithium, or amorphous carbon is preferably used. Porous membrane separator 3
Although not particularly limited, a woven fabric, a glass fiber, a porous synthetic resin film, or the like can be used. For example, a polypropylene or polyethylene porous film is suitable in terms of a thin film, large area, film strength and film resistance.

As the solvent for the non-aqueous electrolyte, those which are commonly used may be used. For example, carbonates, chlorinated hydrocarbons, ethers, ketones, nitriles and the like are preferably used. Particularly preferably, at least one of ethylene carbonate (EC), propylene carbonate (PC), and γ-butyrolactone (GBL) is used as the high dielectric constant solvent, and diethyl carbonate (DEC) and dimethyl carbonate (DMC) are used as the low viscosity solvent. , Ethyl methyl carbonate (EMC), esters and the like, and a mixture thereof is suitably used.

As a supporting salt, LiClO_Four, LiI,
LiPF₆, LiAlCl_Four, LiBF_Four, CF_ThreeSO_ThreeL
At least one kind selected from i.
You. Electrolyte and supporting salt are used for battery environment and battery
It is sufficient to select and adjust as appropriate taking into account optimization etc.
Is, as a supporting salt, 0.8 to 1.5 M LiClO _Four,
LiBF_FourOr LiPF₆And EC + as a solvent
At least DEC, PC + DMC, PC + EMC
It is desirable to use one kind.

As the configuration of the nonaqueous electrolyte secondary battery, various shapes such as a rectangular shape, a paper type, a laminated type, a cylindrical type, and a coin type can be adopted. In addition, the components include a current collector, an insulating plate, and the like, but these are not particularly limited, and may be appropriately selected according to the above shape.

Hereinafter, the non-aqueous electrolyte secondary battery of this embodiment will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 A laminated square cell was prototyped using a positive electrode containing lithium manganate as a main active material. First, lithium manganate and a conductivity-imparting agent are dry-mixed, and a binder polyvinylidene fluoride (PVD) is used.
F) dissolved in N-methyl-2-pyrrolidone (NM
A slurry was prepared by uniformly dispersing it in P). Then
This slurry was applied on an aluminum metal foil having a thickness of 25 μm, and NMP was evaporated to obtain a positive electrode sheet.
The solid content ratio in the positive electrode was lithium manganate: conductivity imparting agent: PVDF = 80: 10: 10 (% by weight).

On the other hand, the negative electrode sheet is made of carbon: PVDF =
NMP was mixed so as to have a ratio of 90:10 (% by weight).
And applied to a copper foil having a thickness of 20 μm. As for the outermost layer, thicknesses of 45, 50, 10
Electrodes composed of four types of Cu foil current collectors of 0 and 125 μm were used. The present electrode used had an outermost layer that was continuous. The electrode sheets of the positive electrode and the negative electrode prepared as described above were laminated via a polyethylene porous membrane separator having a thickness of 25 μm. The electrolyte used was 1 M LiPF ₆ as a supporting salt, and a mixture of propylene carbonate (PC): diethyl carbonate (DEC) in a ratio of 50:50 (vol%) was used as a solvent.

Comparative Example 1 A positive electrode sheet was produced in the same manner as in Example 1. The negative electrode sheet is carbon: PVDF = 9
The mixture was mixed so as to have a ratio of 0:10 (% by weight), dispersed in NMP, and applied on a copper foil having a thickness of 20 μm.
The separator and the electrolyte were the same as in Example 1.

[Evaluation 1] The cycle characteristics at 45 ° C. were evaluated using the laminated square cells produced in Example 1 and Comparative Example 1. Initial charge is 1A to 4.2V, discharge is 5
A was applied to 3.0 V. Table 1 shows that the stacked cells prepared in Example 1 and Comparative Example 1 were 100, 200, and 3 at 45 ° C.
The capacity retention rate (%) after 00 Cycle (cycle) is shown.

[0041]

[Table 1]

In Table 1, the thickness of the outermost current collector is 12
In the case of 5 μm, the current collector is too hard, so that processing becomes difficult.

Example 2 A laminated square cell was prototyped using a positive electrode containing lithium manganate as a main active material. First, lithium manganate and a conductivity-imparting agent were dry-mixed, and uniformly dispersed in N-methyl-2-pyrrolidone (NMP) in which PVDF as a binder was dissolved to prepare a slurry. The slurry was applied on an aluminum metal foil having a thickness of 25 μm, and NMP was evaporated to obtain a positive electrode sheet. The solid content ratio in the positive electrode was lithium manganate: conductivity imparting agent: PVDF = 80: 10: 10 (% by weight).

On the other hand, the negative electrode sheet is made of carbon: PVDF =
NMP was mixed so that the ratio became 90:10 (% by weight).
And applied to a copper foil having a thickness of 20 μm. For the outermost layer, an electrode made of an 80-μm-thick Al foil current collector was used. The present electrode used had an outermost layer that was continuous. The electrode sheets of the positive electrode and the negative electrode prepared as described above were laminated via a polyethylene porous membrane separator having a thickness of 25 μm. The electrolyte is 1M LiP
Using F ₆ as a supporting salt, propylene carbonate (PC):
A mixture of diethyl carbonate (DEC) at a ratio of 50:50 (vol%) was used as a solvent.

Comparative Example 2 A negative electrode sheet was produced in the same manner as in Example 1. The positive electrode sheet is made of Al having a thickness of 20 μm.
The active material was applied on a foil to produce the film. The separator and the electrolyte were the same as in Example 1.

"Evaluation 2" Using the laminated square cells produced in Example 2 and Comparative Example 2, nailing evaluation was performed at room temperature. Initial charge up to 4.2V at 1A, discharge at 3A at 5A.
It went to 0V. Table 2 shows the results of comparative evaluation of the heat generation temperature on the cell surface during the nailing test of the laminated cells manufactured in Example 2 and Comparative Example 2.

[0047]

[Table 2]

According to the present embodiment, it was found that the obtained non-aqueous electrolyte secondary battery exhibited excellent cycle characteristics and good safety.

[Third Embodiment] FIG. 6 is a perspective view showing a current collector of a nonaqueous electrolyte secondary battery according to a third embodiment of the present invention. The difference from the current collector of the second embodiment is that, in the current collector 11 of the second embodiment, each end of the current collector plate 11a is joined to each other by welding or the like to form a joint portion 11b. On the other hand, in the current collector 21 of the present embodiment, one end of each of a pair of rectangular current collector plates 21a sandwiching the outermost positive electrode active material layer 1 from the outside and each of the other ends are formed. One or two or more joint pieces are joined by welding or the like to form joints 21b and 21c, respectively. FIG. 6 shows an example in which a rectangular joining piece is formed at two places at the other end of the current collector plate 21a.

The current collector plate 21a and the joint 2
Due to the elasticity of the whole 1b, a laminated body in which the positive electrode active material layer 1 and the negative electrode active material layer 2 are alternately laminated via the porous membrane separator 3 is sandwiched from the outside. As shown in FIG. 7, also in the current collector 21, the entire part except the terminal 6 is covered with the laminate 7.

In this non-aqueous electrolyte secondary battery, the first
In addition, similarly to the secondary battery of the second embodiment, the outer shape of the secondary battery can be maintained in a desired shape by the current collector 21, and deformation such as swelling due to heat generated by repeating charge and discharge occurs. There is no fear. Further, when an impact or the like is applied from the outside, the current collector 21 protects the laminate from an impact or the like from the outside and retains the outer shape thereof. There is no possibility that deformation or damage will occur even in the case of the addition.

[Fourth Embodiment] FIG. 8 is a perspective view showing a current collector of a nonaqueous electrolyte secondary battery according to a fourth embodiment of the present invention. The difference from the current collector of the third embodiment is that, in the current collector 21 of the third embodiment, the central portion of the joining portion 21b in which one end of the current collecting plate 21a is joined is projected outward to make the rectangular shape. In contrast to the shape of the terminal 6, the current collector 31 of the present embodiment is different from the current collector 31 in that the entire joint 31 b of the current collector plate 31 a protrudes outward to form a rectangular terminal 32. In the current collector 31, as in the third embodiment, one or two or more joint pieces formed at the other end of the pair of rectangular current collector plates 31a are joined by welding or the like. The joining portion 31c is provided. FIG. 8 shows the current collector 31.
An example is shown in which a rectangular joint piece is formed at two places at the other end of a. As shown in FIG. 9, the entire current collector 31 and the laminate are covered with the laminate 7 except for the terminals 32.

In this non-aqueous electrolyte secondary battery, the first
As in the non-aqueous electrolyte secondary batteries of the third to third embodiments, the current collector 31 can maintain the outer shape of the secondary battery in a desired shape, and swelling due to heat generation caused by repeated charging and discharging. There is no risk of deformation. Further, when an impact or the like is applied from the outside, the current collector 31 protects the laminate from the impact from the outside and keeps its outer shape, so that the laminate has an impact from the outside. There is no possibility that deformation or damage will occur even in the case of the addition.

[Fifth Embodiment] FIG. 10 shows a fifth embodiment of the present invention.
FIG. 13 is a perspective view illustrating a current collector of a nonaqueous electrolyte secondary battery according to the fourth embodiment. The difference between the current collector according to the present embodiment and the current collector according to the fourth embodiment is the fourth embodiment. In the current collector 31 in the form, one end of each of a pair of rectangular current collectors 31a and joining pieces of the other end are joined by welding or the like,
In contrast to the junctions 31b and 31c, respectively, in the current collector 41 of the present embodiment, one rectangular current collector plate 42 is bent into two to form a U-shaped cross section, and the U-shaped cross section is formed. The bent portion of the current collector 42 is machined into a rectangular flange to form a terminal 43, and the other ends are joined to each other by welding or the like to form a joint 42a. In the current collector 41 as well, the entire portion except for the terminal 43 is covered with a laminate.

In this non-aqueous electrolyte secondary battery, the first
As in the non-aqueous electrolyte secondary batteries of the fourth to fourth embodiments, the outer shape of the secondary battery can be maintained in a desired shape by the current collector 41, and swelling due to heat generated by repeated charge and discharge, There is no risk of deformation. Further, when an impact or the like is applied from the outside, the current collector 41 protects the laminate from the impact or the like from the outside and retains the outer shape thereof. There is no possibility that deformation or damage will occur even in the case of the addition.

In this non-aqueous electrolyte secondary battery, the other end of the current collector plate 42 having a U-shaped cross section is joined to each other by welding or the like to form a joint 42a. The shape of the current collector plate 42 may be bent into two to form a U-shaped cross section. Also in this case, the same operation and effect as the non-aqueous electrolyte secondary battery of the second embodiment can be obtained.

[Sixth Embodiment] FIG. 11 shows a sixth embodiment of the present invention.
It is a cross-sectional view showing a non-aqueous electrolyte secondary battery of the embodiment,
The difference between the non-aqueous electrolyte secondary battery of the present embodiment and the non-aqueous electrolyte secondary battery of the above-described second embodiment is that, in the secondary battery of the second embodiment, a sheet-like porous membrane separator 3 is provided. While the positive electrode active material layers 1 and the negative electrode active material layers 2 are alternately stacked via the intermediary of the positive electrode active material layer 2, each of the negative electrode active material layers 2 is covered with a bag-shaped porous membrane separator 51 in the secondary battery of the present embodiment. The point is that the active material layers 1 and the negative electrode active material layers 2 covered with the bag-shaped porous membrane separators 51 are alternately laminated.

In this non-aqueous electrolyte secondary battery, the second
As in the non-aqueous electrolyte secondary battery of the embodiment, the current collector 11 can maintain the outer shape of the secondary battery in a desired shape, and deformation such as swelling due to heat generated by repeated charging and discharging can be prevented. There is no danger. In addition, since the negative electrode active material layer 2 is covered with the bag-shaped porous membrane separator 51, the positive electrode active material layer 1 and the negative electrode active material layer 2 are in a well-separated state, thereby extending the life of the battery. Can be.

[Seventh Embodiment] FIG. 12 shows a seventh embodiment of the present invention.
It is a cross-sectional view showing a non-aqueous electrolyte secondary battery of the embodiment,
The difference between the nonaqueous electrolyte secondary battery of the present embodiment and the nonaqueous electrolyte secondary battery of the above-described second embodiment is that, in the secondary battery of the second embodiment, the outermost positive electrode active material layer 1 was connected to a chargeable / dischargeable current collector 11 having a thickness capable of maintaining its shape, and a chargeable / dischargeable foil-shaped current collector 12 was connected to the positive electrode active material layer 1 except for the outermost layer. On the other hand, in the secondary battery of the present embodiment, a current collector 61 having a thickness capable of maintaining its shape and capable of charging and discharging is connected to all the positive electrode active material layers 1 including the outermost layer.

The current collector 61 has a rectangular current collector plate 11a connected to the outside of the outermost positive electrode active material layer 1, and a rectangular current collector plate on all the positive electrode active material layers 1 except the outermost layer. 11a are inserted in a state where they are inserted, and one end of each of the current collector plates 11a is joined by welding or the like to form a joint portion 11b.
It has been.

In the current collector 61, these current collector plates 11a
Also, due to the elasticity of the joint portion 11b, a stacked body in which the positive electrode active material layer 1 and the negative electrode active material layer 2 are alternately stacked via the porous membrane separator 3 is sandwiched. As the current collector 61, as in the second embodiment, any one of a metal thin plate and a shape memory alloy thin plate is suitably used.

In this nonaqueous electrolyte secondary battery, the second
Similarly to the non-aqueous electrolyte secondary battery of the embodiment, the current collector 61 can keep the outer shape of the secondary battery in a desired shape, and deformation such as swelling due to heat generated by repeated charging and discharging can be prevented. There is no danger. Moreover, since the current collectors 11a were connected to all the positive electrode active material layers 1 including the outermost layer,
Compared to a configuration in which only the outermost layer is sandwiched between the current collector plates 11a, the effect of maintaining the outer shape and preventing deformation such as swelling due to heat generation can be further enhanced. This effect is remarkable when the size of the secondary battery is increased.

Further, as the current collector 61, a shape memory alloy which is deformed in a direction to be reduced as the temperature becomes higher by repeating charging and discharging, thereby holding the outer shape of the secondary battery in a desired shape. The use of a thin plate can further enhance the effect of maintaining the external shape and preventing deformation such as bulging due to heat generation.

As described above, each embodiment of the secondary battery of the present invention has been described by taking a non-aqueous electrolyte secondary battery as an example.
The specific configuration is not limited to each of the above embodiments, and a design change or the like can be made without departing from the gist of the present invention. For example, in the nonaqueous electrolyte secondary battery of the second embodiment, the number of layers of the stacked body is set to 2 to 40, but the number of layers of the stacked body is appropriately set according to the required electromotive force and the magnitude of the capacity. do it.

In this non-aqueous electrolyte secondary battery, the central portion of the joint portion 11b is projected outward to form a rectangular terminal 6, but the terminal 6 may be any terminal as long as it satisfies its function. The position and shape can be appropriately changed as needed. For example, a portion other than the central portion of the joint portion 11b may be protruded outward to form a terminal, or the entire joint portion 11b may be protruded outward to form a terminal.

In the non-aqueous electrolyte secondary battery of the seventh embodiment, the rectangular current collector plate 11a is connected to all the positive electrode active material layers 1 including the outermost layer. 1, a current collector plate is connected to a certain positive electrode active material layer 1, and a current collector foil is connected to an adjacent positive electrode active material layer 1, for example. It is good also as a structure which connected the electrofoil alternately.

[0067]

As described above, according to the secondary battery of the present invention, the positive electrode active material layer and the negative electrode active material layer are sandwiched between the chargeable and dischargeable current collectors having a thickness capable of maintaining the shape. Therefore, even when charge and discharge are repeatedly performed, there is no possibility that deformation such as swelling occurs, and the external shape can be favorably maintained. Further, even when an external impact or the like is applied, the current collector protects the laminate from external impact or the like and retains its outer shape. There is no possibility that deformation or damage will occur even in the case of adding.

In addition, since a metal thin plate having a thickness of 50 μm or more and 120 μm or less, particularly one of a copper thin plate and an aluminum thin plate, is used as the current collector, the capacity retention rate is not affected by repeated charge and discharge in the cycle characteristic evaluation. It does not decrease, and there is no risk of deterioration even if charging and discharging are repeated many times, and a sufficient electromotive force can be secured. Further, since the heat radiation characteristics are excellent, heat is hardly stored, and the reliability can be improved.

As described above, even when charge / discharge is repeatedly performed, there is no possibility that the outer shape is deformed due to swelling. Therefore, the initial outer shape can be favorably maintained, and high safety can be achieved. And a non-aqueous electrolyte secondary battery having excellent cycle characteristics, charge / discharge characteristics, and heat radiation characteristics.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a nonaqueous electrolyte secondary battery according to a first embodiment of the present invention.

FIG. 2 is a plan view showing an external shape of the nonaqueous electrolyte secondary battery according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a non-aqueous electrolyte secondary battery according to a second embodiment of the present invention.

FIG. 4 is a perspective view illustrating a current collector of a nonaqueous electrolyte secondary battery according to a second embodiment of the present invention.

FIG. 5 is a plan view illustrating an external shape of a nonaqueous electrolyte secondary battery according to a second embodiment of the present invention.

FIG. 6 is a perspective view illustrating a current collector of a nonaqueous electrolyte secondary battery according to a third embodiment of the present invention.

FIG. 7 is a plan view showing an external shape of a nonaqueous electrolyte secondary battery according to a third embodiment of the present invention.

FIG. 8 is a perspective view showing a current collector of a nonaqueous electrolyte secondary battery according to a fourth embodiment of the present invention.

FIG. 9 is a plan view showing the external shape of a nonaqueous electrolyte secondary battery according to a fourth embodiment of the present invention.

FIG. 10 is a perspective view showing a current collector of a nonaqueous electrolyte secondary battery according to a fifth embodiment of the present invention.

FIG. 11 is a sectional view showing a non-aqueous electrolyte secondary battery according to a sixth embodiment of the present invention.

FIG. 12 is a sectional view showing a non-aqueous electrolyte secondary battery according to a seventh embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode active material layer 2 Negative electrode active material layer 3 Porous membrane separator 4 Plate-shaped current collector 4a Current collector 4b Junction 5 Foil-shaped current collector 6 Terminal 7 Laminate 11 Current collector 11a Current collector 11b Joint 12, 13 foil-shaped current collector 21 current collector 21a current collector 21b, 21c junction 31 current collector 31a current collector 31b, 31c junction 32 terminal 41 current collector 42 current collector 42a junction 43 terminal 51 bag-shaped porous membrane separator 61 current collector

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H017 AA03 AS02 CC03 CC20 EE01 EE05 HH03 HH05 5H029 AJ02 AJ05 AJ12 AK03 AL06 AL07 AL12 AM03 AM04 AM05 AM07 BJ02 BJ03 BJ04 BJ12 CJ03 DJ07 DJ11 EJ01 HJ04 HJ12

Claims (9)

[Claims] 1. A secondary battery in which a positive electrode active material layer and a negative electrode active material layer are arranged to face each other, wherein these active material layers are formed of a current collector having a thickness capable of maintaining a shape and capable of being charged and discharged. A secondary battery characterized by being sandwiched. 2. A secondary battery in which a plurality of positive electrode active material layers and a plurality of negative electrode active material layers are alternately stacked in the thickness direction with a porous film interposed therebetween, wherein an outermost active material layer having one of the polarities is provided. A current collector having a thickness capable of maintaining its shape and capable of being charged and discharged, and the plurality of active material layers sandwiched between the current collectors. 3. The current collector is formed by joining one end of each of a pair of plate-shaped current collectors sandwiching the plurality of active material layers, and the thickness of the joined portion is equal to or greater than the thickness of the plate-shaped portion. The secondary battery according to claim 1, wherein: 4. The current collector is formed by bending a plate-shaped current collector to have a U-shaped cross section and sandwiching the plurality of active material layers by the elasticity of the U-shaped current collector. The secondary battery according to claim 1, wherein: 5. The current collector is formed in a bag shape accommodating the plurality of active material layers, and the plurality of active material layers are sandwiched by the elasticity of the bag-shaped current collector. Claim 1
Or the secondary battery according to 2. 6. The secondary battery according to claim 1, wherein the current collector is a metal sheet or a shape memory alloy sheet. 7. The secondary battery according to claim 6, wherein the metal sheet is a copper sheet or an aluminum sheet. 8. The secondary battery according to claim 6, wherein the shape memory alloy sheet is a Ni—Ti alloy sheet mainly composed of nickel and titanium. 9. The secondary battery according to claim 1, wherein the current collector has a thickness of 50 μm or more and 120 μm or less.