KR101375422B1 - Lithium-ion battery and method for producing same - Google Patents

Abstract

The present invention provides a lithium ion battery capable of detecting an internal short circuit due to incorporation of a metal foreign matter at high sensitivity and a method of manufacturing the same.
In a lithium ion battery comprising a positive electrode 16, a negative electrode 15, and an electrolyte, an electrical insulating layer 3 having an electrically conductive layer 4 is provided between the positive electrode and the negative electrode, and the positive electrode 16 is charged during charging. A voltage is applied between the electrode and the electrically conductive layer 4 to measure the potential difference and the current between the positive electrode 16 and the electrically conductive layer 4, so that when metal foreign matter is mixed, the positive electrode electrically conducts faster than the positive electrode negative electrode. Since a short circuit occurs between the layers, it is possible to detect that an internal short circuit can occur with high sensitivity early.

Description

Lithium ion battery and its manufacturing method {LITHIUM-ION BATTERY AND METHOD FOR PRODUCING SAME}

The present invention relates to a lithium ion secondary battery and a manufacturing method thereof.

BACKGROUND ART Lithium ion secondary batteries are used for power sources such as notebook personal computers and portable information devices such as mobile phones, portable acoustic devices, radios, and power tools due to their high energy density. Moreover, the lithium ion secondary battery also has the advantage of high capacity and high output. Therefore, it has recently been used as a power source for electric power storage systems, such as electric vehicles, hybrid electric vehicles (hereinafter, both electric vehicles) using an electric motor together with an electric motor, and an uninterruptible power supply.

The lithium ion secondary battery overlaps a positive electrode using a positive electrode active material capable of releasing and occluding lithium ions by charging and discharging, and a negative electrode using a negative electrode active material capable of occluding and releasing lithium ions by charging and discharging through a separator. And these are infiltrated in electrolyte solution. In more detail, materials such as lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), and the like are contained in the positive electrode, Lithium ion secondary batteries using each of the possible materials are widely used.

The positive electrode active material as described above does not have sufficient electronic conductivity. Therefore, in the positive electrode, the positive electrode mixture generally contains a conductive powder which is stable in the battery at low cost, such as graphite or carbon black, as a conductive aid, and further adds a binder (binder) and mixes them. Used. On the other hand, the carbon material used as the negative electrode active material is in a state in which lithium ions are completely released during battery assembly, that is, in a discharged state. In the negative electrode, a negative electrode mixture prepared by adding a binder for securing adhesion to the negative electrode active material and mixing them is used.

Usually, the electrode internal structure of a lithium ion secondary battery is a winding type | mold or a lamination type in order to raise a capacity and an output. That is, the positive electrode and negative electrode which apply | coated the active substance to the metal foil used as an electrical power collector are wound or laminated | stacked through a separator, and this wound body or laminated body is accommodated in the metal cylindrical or rectangular battery outer container.

After the wound body or the laminated body was accommodated in the battery outer container, the electrolyte solution was then poured and the lid was covered and sealed. In addition to the metal container, an aluminum laminate container is also used for the battery outer container. The lithium ion secondary battery assembled by this method gives a function as a battery by the initial charge after assembly.

In the above-described raw materials and manufacturing processes of the battery, when a metal foreign matter is mixed in the battery, internal short circuit may occur. The mixed metal foreign matter is dissolved on the positive electrode, becomes ions and diffuses, and when it reaches the negative electrode, the metal is reprecipitated. Precipitation proceeds, and as the metal grows toward the positive electrode, it becomes an electrically conductive path, which eventually causes an internal short circuit between the negative electrode and the positive electrode. When the internal short circuit occurs, the charged electricity is consumed, and the usable capacity decreases, or even when charging, the electric current does not flow through the internal short circuit section, thereby preventing the battery from functioning as a normal battery.

In order to select a battery in which metal foreign matter is mixed, Patent Literature 1 discloses that after charging, the battery is separated from the charging circuit and left to stand, the change in the open circuit voltage of the battery is measured, and the open circuit voltage is significantly lowered due to an internal short circuit. I make it a defective article.

Moreover, the following method is proposed as a method of suppressing such an internal short circuit. Patent Literatures 2 and 3 describe methods for dissolving and diffusing a metal foreign matter electrochemically and not depositing on a negative electrode. In addition, Patent Document 4 discloses a method in which a substance that traps impurities containing cations is contained in a battery and is not precipitated as a metal.

Japanese Patent Laid-Open No. 2003-36887 Japanese Patent Laid-Open No. 2005-243537 Japanese Patent Laid-Open No. 2007-26752 Japanese Patent Laid-Open No. 2000-77103

In the method of patent document 1, in the structure of the conventional positive electrode, negative electrode, and separator, there exists a problem that it takes time until it can determine as a defective product.

Moreover, the method of patent documents 2-4 also takes time from melt | dissolution to diffusion. When the mass of the metal foreign matter is large, the diffusion becomes insufficient, and metal ions may reach and precipitate on the negative electrode.

Therefore, an object of this invention is to provide the lithium ion secondary battery which can detect an internal short circuit by the incorporation of a metal foreign material at high sensitivity earlier than before, and its manufacturing method.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the lithium ion secondary battery of this invention is a lithium ion battery provided with a battery exterior container, a positive electrode, a negative electrode, the electrical insulation layer provided between the said positive electrode and the said negative electrode, and the said electrolyte. An electrical conductive layer is provided in the electrical insulation layer between a positive electrode and a negative electrode.

According to the present invention, it is possible to provide a lithium ion secondary battery capable of detecting an internal short circuit caused by the incorporation of a metal foreign matter at a high sensitivity and a manufacturing method thereof.

BRIEF DESCRIPTION OF THE DRAWINGS It is schematic sectional drawing of the electrode vicinity of the lithium ion secondary battery of this invention.
2 is a schematic cross-sectional view of an electrode vicinity of a conventional lithium ion secondary battery.
3 is a schematic cross-sectional view of a process of forming an electrically conductive layer and an electrically insulating layer having through holes.
4 is a schematic cross-sectional view and enlarged view of an electrically conductive layer and an electrically insulating layer having through holes.
5 is a schematic top view of an electrode-laminated lithium ion secondary battery having a structure of the present invention.
6 is a schematic cross-sectional view of an electrode-laminated lithium ion secondary battery having a structure of the present invention.
7 is an external schematic diagram of an electrode wound body-type lithium ion secondary battery having a structure of the present invention.
8 is a schematic cross-sectional view of an electrode wound body-type lithium ion secondary battery having a structure of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.

(Example 1)

Fig. 1 shows a cross-sectional schematic diagram of the vicinity of the electrode of the lithium ion secondary battery of this embodiment. The battery according to this embodiment includes a positive electrode 16 having a positive electrode current collector 6 and a positive electrode side mixture layer 5, and a negative electrode having a negative electrode current collector 1 and a negative electrode side mixture layer 2. 15), the electrical insulation layer 3 provided between the positive electrode 16 and the negative electrode 15, and the electrical conductive layer 4 provided in the electrical insulation layer 3 are provided.

The positive electrode 16 contains lithium manganate, which is one of lithium transition metal composite oxides as an active substance, carbon powder as a conductive aid, and polyvinylidene fluoride (hereinafter referred to as PVDF) as a binder, 1-methyl-2-pyrrolidone. The slurry dispersed and kneaded in the following (hereinafter referred to as NMP) was coated onto Al positive electrode current collector 6 to be a positive electrode mixture layer 5, and dried.

The negative electrode 15 is coated with a negative electrode side current collector 1 by coating a slurry made of carbon powder capable of occluding and releasing lithium ions as an active substance and a mixture of PVDF dispersed in NMP as a binder and mixed with a negative electrode side current collector 1 made of Cu. It was set as the layer (2), and it produced by drying.

The electrically conductive layer 4 and the electrically insulating layer 3 having a through hole between the positive electrode 16 and the negative electrode 15 were produced as follows. Of those used as separators for lithium ion secondary batteries, one microporous polypropylene sheet and one polyethylene sheet each having a thickness of 18 µm were prepared. These become the electrical insulation layer 3. Among them, a Cu layer having a thickness of about 0.5 μm was formed on one side of the polypropylene sheet by using an ion beam sputtering device to obtain an electrically conductive layer having through holes (FIGS. 3 (1) and 2). The other polyethylene sheet was repeatedly thermocompressed on this Cu layer ((3) and (4) of FIG. 3). As shown in Fig. 3 (4), a three-layered sheet of polypropylene / Cu / polyethylene was thus formed. This will be referred to as separator (A) below.

This electrically conductive layer 4 and the electrically insulating layer 3 are microporous with a through hole 7 so that electrolyte (not shown) can penetrate and maintain ion conductivity as shown in FIG. There is a need. The through hole 7 penetrates from the positive electrode 16 to the negative electrode 15. The average pore size of the through hole 7 is preferably 0.05 to 5 µm from the viewpoint of the permeability of the electrolyte, the separation of the positive electrode 16 and the negative electrode 15, and the passage of particles of the peeled electrode mixture. When the electrolyte is injected in the battery assembly step, the through hole 7 is filled with the electrolyte, so that ions in the electrolyte can move between the positive electrode and the negative electrode.

Although the thickness of the electrical insulation layer is 18 µm here, the smaller the distance between the positive electrode 16 and the electrically conductive layer 4 is, the higher the sensitivity can be detected and the incorporation of metal foreign matter is maintained, thereby maintaining mechanical strength and electrical insulation. It can also be made thinner in the range.

In addition, although the ion beam sputtering apparatus was used for formation of the electrically conductive layer 4 here, an RF sputtering apparatus, a magnetron sputtering apparatus, or a vacuum vapor deposition apparatus can also be used. Since the base polypropylene sheet has a through hole 7, when the Cu layer having a thickness of about 0.05 to 20 mu m is formed thereon, the through hole 7 is retained, and the electrical conductivity is also expressed, and the through hole 7 It becomes an electrically conductive layer which has.

Cu is used as an example of the electrically conductive layer, but any material other than Cu may be used as long as it is electrically conductive, does not form an alloy with Li, and does not dissolve in the electrolyte. For example, Ni, carbon, indium tin oxide, or the like may be used. Conductive metal oxides such as (ITO) and MnO ₂ can also be used. In addition, metals, alloys, and conductive polymers can also be used.

Moreover, not only a polypropylene sheet and a polyethylene sheet, but the sheet | seat of other polyolefin resin, polyester resin, polyimide resin, and fluororesin which have a through hole can also be used.

Moreover, the laminated sheet which laminated | stacked polypropylene and polyethylene which have a through-hole each other can also be used.

Cu foil which serves as a lead wire for making electrical connection was attached to the edge part of separator A by pressing. Subsequently, the electrode laminated body 14 was produced by superimposing the said positive electrode 16, the separator (A), the negative electrode 15, and the separator (A) one by one.

Next, the lithium ion secondary battery which incorporates the electrode laminated body 14 is shown in FIG. 5 and FIG. The manufactured electrode laminated body 14 is accommodated in the aluminum laminated battery outer container 12, and the terminals 8 and 9 attached to the electrode laminated body 14 and the battery outer container 12 by lead wires. , Electrical connection with (14) was established. The positive electrode of the electrode laminate 14 is connected to the positive electrode terminal 8, the negative electrode of the electrode laminate 14 is connected to the negative electrode terminal 13, and the electrically conductive layer 4 is connected to the electrically conductive layer. (10) was connected. Thereafter, the electrolyte was injected. As the electrolyte, a solution in which lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solution of ethylene carbonate (hereinafter referred to as EC) and dimethyl carbonate (hereinafter referred to as DMC) was used.

Subsequently, a battery cover (not shown) was attached to the battery outer container 12, and the battery cover shown in Figs. 5 and 6 was assembled by sealing by thermocompression bonding and an adhesive.

After the completion of assembly, the first charge was performed at a constant voltage of 4.2 V and a current value equivalent to 1 C of charge current. However, 1 C is a current value for charging the battery capacity in one hour.

During charging, a battery voltage of −4.2 V (relative to the positive electrode) equal to the negative electrode is applied to the electrically conductive layer 4 via the terminal 10 connected to the electrically conductive layer, so that the electrically conductive layer 4 and the positive electrode 16 The potential difference and current between were measured.

In addition, a voltage different from that of the negative electrode 15 may be applied to the electrically conductive layer 4. To promote dissolution and precipitation, a lower voltage, such as -4.5 V (based on the positive electrode), may be applied to the electrically conductive layer in the range where the electrolyte is not decomposed. When making it the same as the negative electrode 15, the same thing as the circuit connected to the negative electrode 15 at the time of charge can be used, and the circuit for control is simplified.

Alternatively, after the charging is completed, the positive electrode 16 and the negative electrode 15 are separated from the charge / discharge circuit, and the electric conduction layer is applied with a battery voltage of -4.2 V (based on the positive electrode), which is the same as that of the negative electrode 15, to electrically conduct the electric conduction. The potential difference and current between the layer and the positive electrode 16 may also be measured.

In addition, since the electrically conductive layer 4 is not particularly used after shipment of the lithium ion secondary battery, the terminal 10 connected to the electrically conductive layer is hidden by a member before shipment after shipment, or the terminal connected to the electrically conductive layer. 10 and the lead wire can also be removed.

(Example 2)

The positive electrode 16 and the negative electrode 15 were produced in the same manner as in Example 1.

The electrically conductive layer 4 and the electrically insulating layer 3 having a through hole between the positive electrode 16 and the negative electrode 15 were produced as follows. Two sheets of microporous polyethylene sheets having a thickness of 18 µm were prepared among those used as separators for lithium ion secondary batteries. These become the electrical insulation layer 3.

Among them, an alkaline potassium permanganate solution was brought into contact with one surface, and the surface of the polyethylene sheet was microetched.

Palladium was then adsorbed onto the micro etched surface and catalyzed for electroless plating. Thereafter, a Cu film having a thickness of about 0.5 µm was formed using an electroless Cu plating method to obtain an electrically conductive layer ((1) and (2) in FIG. 3).

The other polyethylene sheet was piled up on this Cu layer and thermocompression-bonded (FIG. 3 (3), (4)). As shown in Fig. 3 (4), a sheet having a three-layer structure of polyethylene / Cu / polyethylene was thus formed. This will be referred to as separator (B) below.

This electrically conductive layer 4 and the electrically insulating layer 3 need to be microporous with the through hole 7 in order for electrolyte to penetrate and maintain ion conductivity as shown in FIG. The average pore size of the through hole is preferably 0.05 to 5 m in view of the permeability of the electrolyte, the separation of the positive electrode and the negative electrode, and the prevention of passage of the particles of the peeled electrode mixture. When the electrolyte is injected in the battery assembly step, the through hole 7 is filled with the electrolyte, so that ions in the electrolyte can move between the positive electrode and the negative electrode.

Although the thickness of the electrical insulation layer is 18 µm here, the smaller the distance between the positive electrode 16 and the electrically conductive layer 4 is, the higher the sensitivity can be detected and the incorporation of metal foreign matter is maintained, thereby maintaining mechanical strength and electrical insulation. It can also be made thinner in the range.

In addition, although only the electroless plating method was used here, after a Cu film is affixed by the electroless plating method, a Cu film or a Ni film can also be formed as an seed layer by the electroplating method. Alternatively, a Cu film or a Ni film may be formed by electroplating as a seed layer after depositing a Cu film as in the first embodiment.

Since the base polyethylene sheet has a through hole, when the Cu layer having a thickness of about 0.05 to 20 μm is formed thereon, the through hole is retained and the electrical conductivity is also expressed, resulting in the electrically conductive layer 4 having the through hole. .

Although Cu was used as an example of the electrically conductive layer, any material other than Cu may be used as long as it is a material having electrical conductivity, which does not form an alloy with Li, and does not dissolve in the electrolyte. For example, Ni may be used.

In addition to the polyethylene sheet, a sheet of a polypropylene resin, a polyester resin, a polyimide resin, or a fluorine resin having a through hole may be used.

However, in the case of polyimide resin, surface modification by alkali hydroxide aqueous solution or ultraviolet-ray, plasma, etc. is required as a pretreatment of electroless plating.

In the case of the fluororesin, surface modification using metal sodium-naphthalene is required as the pretreatment of electroless plating.

Moreover, the laminated sheet which laminated | stacked polyethylene and polypropylene which have a through-hole each other can also be used.

Cu foil which serves as a lead wire for making an electrical connection was crimped | bonded and attached to the edge part of separator B. FIG. Subsequently, the positive electrode, the separator (B), the negative electrode, and the separator (B) were sequentially stacked and wound up to prepare an electrode wound body 11.

Subsequently, the electrode wound body 11 was housed in a Ni-plated Fe battery outer container, and electrical connection was made between the electrode wound body and the battery outer container. Thereafter, the electrolyte was injected. As the electrolyte, a liquid in which LiPF ₆ was dissolved in a mixed solution of EC and DMC was used.

Subsequently, the battery cover was attached to the battery outer container, and the battery cover was sealed by a caulking method to assemble the battery shown in FIGS. 7 and 8.

After the completion of assembly, the first charge was performed at a constant voltage of 4.2 V and a current value equivalent to 1 C of charge current. However, 1 C is a current value for charging the battery capacity in one hour.

During charging, a battery voltage of -4.2 V (positive electrode) as the negative electrode was applied to the electrically conductive layer, and the potential difference and current between the electrically conductive layer and the positive electrode were measured.

In addition, a voltage different from that of the negative electrode may be applied to the electrically conductive layer. To promote dissolution and precipitation, a lower voltage, such as -4.5 V (based on the positive electrode), may be applied to the electrically conductive layer in the range where the electrolyte is not decomposed.

Alternatively, after the charging is completed, the positive electrode and the negative electrode are separated from the charge / discharge circuit. Then, a battery voltage of -4.2 V (relative to the positive electrode), which is the same as that of the negative electrode, is applied to the electrically conductive layer, so that the potential difference and current between the electrically conductive layer and the positive electrode are adjusted. You can also measure.

(Example 3)

The positive electrode 16 and the negative electrode 15 were produced in the same manner as in Example 1.

The electrically conductive layer 4 and the electrically insulating layer 3 which have through-holes between a positive electrode and a negative electrode were produced as follows. Two sheets of microporous polyethylene sheets having a thickness of 18 µm were prepared among those used as separators for lithium ion secondary batteries. These become the electrical insulation layer 4.

On one of the sheets, a slurry in which carbon powder and PVDF were dispersed and dissolved in NMP was applied, dried under reduced pressure at 60 to 100 ° C., and a carbon film having a thickness of about 1 μm was formed to form an electrically conductive layer (FIG. 3). (1), (2)). The other polyethylene sheet was piled up on this carbon layer and thermocompression-bonded (FIG. 3 (3), (4)). As shown in Fig. 3 (4), a sheet having a three-layer structure of polyethylene / carbon / polyethylene was thus formed. This is hereinafter referred to as separator (C).

The electrically conductive layer 4 and the electrically insulating layer 3 need to be microporous with a through hole 7 in order to allow the electrolyte to penetrate and maintain ion conductivity as shown in FIG. 4. The average pore size of the through hole 7 is 0.05 to 5 µm in view of the permeability of the electrolyte, the separation of the positive electrode 16 and the negative electrode 15, and the prevention of passage of the particles of the peeled electrode mixtures 2 and 5. Is preferred. When the electrolyte is injected in the battery assembly step, the through hole 7 is filled with the electrolyte, so that ions in the electrolyte can move between the positive electrode 16 and the negative electrode 15.

Although the thickness of the electrical insulation layer 3 is 18 micrometers here, since the smaller the distance of the positive electrode 16 and the electrically conductive layer 4, the incorporation of a metal foreign material can be detected early with high sensitivity, and therefore mechanical strength and electrical It can also be made thinner in the range in which insulation is maintained.

Here, although the electrically conductive layer was formed by apply | coating the slurry containing carbon powder, the solution which melt | dissolved the conductive polymers, such as polypyrrole, polythiophene, and polyaniline, in the organic solvent can also be apply | coated.

Since the base polyethylene sheet has a through hole, and carbon powder is coated thereon, when a carbon film having a thickness of about 0.05 to 20 μm is formed thereon, the through hole is retained, and electrical conductivity is also expressed, and the through hole has a through hole. It becomes an electrically conductive layer.

In addition to the polyethylene sheet, a sheet of a polypropylene resin, a polyester resin, a polyimide resin, or a fluorine resin having a through hole may be used.

Moreover, the laminated sheet which laminated | stacked polyethylene and polypropylene which have a through-hole each other can also be used.

Cu foil which serves as a lead wire for making an electrical connection was crimped | bonded and attached to the edge part of separator (C). Subsequently, the electrode laminated body 14 was produced by superimposing the said positive electrode 16, the separator (C), the negative electrode 15, and the separator (C) one by one.

Subsequently, the electrode laminated body 14 was accommodated in the aluminum laminated battery outer container 12, and the electrical connection between the electrode laminated body and the battery outer container was established. Thereafter, the electrolyte was injected. As the electrolyte, a liquid in which LiPF ₆ was dissolved in a mixed solution of EC and DMC was used.

Subsequently, the battery cover was attached to the battery outer container, and the battery cover shown in FIGS. 5 and 6 was assembled by sealing by heat pressing and adhesive.

After the completion of assembly, the first charge was performed at a constant voltage of 4.2 V and a current value equivalent to 1 C of charge current. However, 1 C is a current value for charging the battery capacity in one hour.

During charging, a battery voltage of −4.2 V (positive electrode reference) equal to that of the negative electrode was applied to the electrically conductive layer 4 to measure the potential difference and current between the electrically conductive layer 4 and the positive electrode 16.

In addition, a voltage different from that of the negative electrode 15 may be applied to the electrically conductive layer 4. To promote dissolution and precipitation, a lower voltage, such as -4.5 V (based on the positive electrode), may be applied to the electrically conductive layer in the range where the electrolyte is not decomposed.

Alternatively, after the charging is completed, the positive electrode 16 and the negative electrode 15 are separated from each other by the charge / discharge circuit. Then, a battery voltage of -4.2 V (based on the positive electrode), which is the same as that of the negative electrode, is applied to the electrically conductive layer, whereby the electrically conductive layer 4 ) And the electric potential difference between the positive electrode 16 and the positive electrode 16 may be measured.

(Example 4)

The positive electrode 16 and the negative electrode 15 were produced in the same manner as in Example 1.

The electrically conductive layer 4 and the electrically insulating layer 3 having a through hole between the positive electrode 16 and the negative electrode 15 were produced as follows. Of the microporous polyethylene sheets having a thickness of 18 µm, one sheet was used as the separator for a lithium ion secondary battery. This becomes an electrical insulation layer. On one side of this polyethylene sheet, a Cu layer having a thickness of about 0.5 탆 was formed using an ion beam sputtering device to obtain an electrically conductive layer having through holes (FIGS. 3 (1) and (2)).

The solution which disperse | distributed and dissolved PVDF in NMP was apply | coated on this Cu layer, and it dried under reduced pressure at 60-100 degreeC, and formed the electrical insulation layer of about 20 micrometers (FIG. 3 (3), (4)). As shown in Fig. 3 (4), a sheet having a three-layer structure of PVDF / Cu / polyethylene was thus formed. This is hereinafter referred to as separator (D).

This electrically conductive layer 4 and the electrically insulating layer 3 need to be microporous with the through hole 7 in order for electrolyte to penetrate and maintain ion conductivity as shown in FIG. The average pore size of the through hole is preferably 0.05 to 5 m in view of the permeability of the electrolyte, the separation of the positive electrode and the negative electrode, and the prevention of passage of the particles of the peeled electrode mixture. When the electrolyte is injected in the battery assembly step, the through hole 7 is filled with the electrolyte, so that ions in the electrolyte can move between the positive electrode 16 and the negative electrode 15.

Although the thickness of the electrical insulation layer is 18 占 퐉, here, the smaller the distance between the positive electrode 16 and the electrical insulation layer 3, the more sensitively the incorporation of metal foreign matter can be detected early, thus maintaining mechanical strength and electrical insulation. It can also be made thinner in the range.

In addition, although the ion beam sputtering apparatus was used for formation of the electrically conductive layer 4 here, an RF sputtering apparatus, a magnetron sputtering apparatus, or a vacuum vapor deposition apparatus can also be used. Since the base polypropylene sheet has a through hole, when the Cu layer having a thickness of about 0.05 to 20 μm is formed thereon, the through hole is retained, and the electrical conductivity is also expressed, so that the electrically conductive layer 4 having the through hole is do.

Cu was used as an example of the electrically conductive layer 4, but any material other than Cu can be used as long as it has a material of electrical conductivity, does not form an alloy with Li, and does not dissolve in the electrolyte. For example, Ni, carbon, or indium may be used. A conductive metal oxide such as tin oxide (ITO) or MnO ₂ may be used.

Since the base electrically conductive layer 4 has a through hole, when a solution in which PVDF is dispersed and dissolved in NMP at about 1 to 20 µm is applied thereon, the through hole is retained, and electrical insulation is also exhibited. It becomes an electrical insulation layer which has.

As the electrical insulation layer 3 formed on a Cu layer, polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), and carboxymethylcellulose (CMC) can also be used besides PVDF. In order to keep the porous, inorganic particles such as alumina or silica may be mixed.

In addition to the polypropylene sheet, a sheet of a polyethylene resin, a polyester resin, a polyimide resin, or a fluorine resin having a through hole may be used.

Moreover, the laminated sheet which laminated | stacked polypropylene and polyethylene which have a through-hole each other can also be used.

Cu foil which serves as a lead wire for making an electrical connection was crimped | bonded and attached to the edge part of the separator (D). Subsequently, the positive electrode 16, the separator (D), the negative electrode 15, and the separator (D) were sequentially superposed, and the electrode laminated body 14 was produced.

Subsequently, the electrode laminated body 14 was accommodated in the aluminum laminated battery outer container 12, and the electrical connection between the electrode laminated body and the battery outer container was established. Thereafter, the electrolyte was injected. As the electrolyte, a liquid in which LiPF ₆ was dissolved in a mixed solution of EC and DMC was used.

Subsequently, the battery cover was attached to the battery outer container, and the battery cover shown in FIGS. 5 and 6 was assembled by sealing by heat pressing and adhesive.

After the completion of assembly, the first charge was performed at a constant voltage of 4.2 V and a current value equivalent to 1 C of charge current. However, 1 C is a current value for charging the battery capacity in one hour.

During charging, a battery voltage of -4.2 V (positive electrode) as the negative electrode was applied to the electrically conductive layer, and the potential difference and current between the electrically conductive layer and the positive electrode were measured.

In addition, a voltage different from that of the negative electrode may be applied to the electrically conductive layer. To promote dissolution and precipitation, a lower voltage, such as -4.5 V (based on the positive electrode), may be applied to the electrically conductive layer in the range where the electrolyte is not decomposed.

Alternatively, after the charging is completed, the positive electrode and the negative electrode are separated from the charge / discharge circuit. Then, a battery voltage of -4.2 V (relative to the positive electrode), which is the same as that of the negative electrode, is applied to the electrically conductive layer, so that the potential difference and current between the electrically conductive layer and the positive electrode are adjusted. You can also measure.

(Comparative Example 1)

A battery was assembled using the positive electrode, the negative electrode, and the electrolyte solution having the same specifications as in Examples 1 to 4 except that the electrically conductive layer was not formed on the separator.

The separator used the porous polyethylene sheet of 35 micrometers in thickness, used as a separator for lithium ion secondary batteries.

After the completion of assembly, the first charge was performed at a constant voltage of 4.2 V and a current value equivalent to 1 C of charge current. However, 1 C is a current value for charging the battery capacity in one hour.

(Evaluation example)

In order to confirm the effects of the present invention, in the batteries of Examples 1 to 4 and Comparative Example 1, metal foreign materials (Fe) having an average particle diameter of about 80 μm and about 30 μm in the electrode manufacturing process, 1 to 10 on the positive electrode and on the positive electrode surface. Dogs were incorporated.

After the completion of assembly, the first charge was performed at a constant voltage of 4.2 V and a current value equivalent to 1 C of charge current. However, 1 C is a current value for charging the battery capacity in one hour.

During charging, a battery voltage of -4.2 V (positive electrode) as the negative electrode was applied to the electrically conductive layer, and the potential difference and current between the electrically conductive layer and the positive electrode were measured.

When an internal short circuit occurs, the absolute value of the potential difference between the electrically conductive layer and the positive electrode becomes smaller than 4.2 V, and a short circuit current is observed at the same time. The short circuit current changes depending on the applied voltage and the electrical resistance of the short circuit. The battery whose change in potential difference and short-circuit current were observed to be large compared to the behavior of a good battery in which an internal short circuit did not occur without the incorporation of metallic foreign matter was judged as an internal short circuit, and was selected as a defective product.

In addition, a voltage different from that of the negative electrode may be applied to the electrically conductive layer. To promote dissolution and precipitation, a lower voltage, such as -4.5 V (based on the positive electrode), may be applied to the electrically conductive layer in the range where the electrolyte is not decomposed.

Alternatively, after the charging is completed, the positive electrode and the negative electrode are separated from the charge / discharge circuit. Then, a battery voltage of -4.2 V (relative to the positive electrode), which is the same as that of the negative electrode, is applied to the electrically conductive layer, so that the potential difference and current between the electrically conductive layer and the positive electrode are adjusted. You can also measure.

The results are shown in Table 1. Here, the short circuit which occurred between the electrically conductive layer and the positive electrode of this invention is represented by the internal short circuit.

In the case of a metal foreign material having an average particle diameter of 80 mu m, an internal short circuit occurred early in the battery of the present invention within a time of 1/12 to 1/2 of the conventional battery.

In the case of a metal foreign material having an average particle diameter of 30 µm, internal short circuit did not occur in the conventional battery, but internal short circuit occurred in the battery of the present invention.

That is, according to the present invention, the internal short circuit caused by the metal foreign matter could be detected earlier than before. In addition, in the present invention, the internal short circuit caused by the small metal foreign matter missed was detected because the internal short circuit did not occur even when mixed.

1: negative electrode current collector
2: negative electrode mixture layer
3: electrical insulation layer
4: electrical conductive layer
5: positive electrode mixture layer
6: positive electrode current collector
7: through hole
8: Terminal connected to the positive electrode
9: Body of battery outer container connected to negative electrode
10: terminal connected to the electrically conductive layer
11: electrode winding body
12: battery laminated container of aluminum laminate type
13: terminal connected to the negative electrode
14: electrode stack
15: negative electrode
16: positive electrode

Claims (10)

Battery outer container,
The positive electrode,
Negative,
An electrical insulation layer provided between the positive electrode and the negative electrode;
In a lithium ion battery provided with an electrolyte,
An electric conductive layer is provided in the electric insulating layer between the positive electrode and the negative electrode,
The said electrically conductive layer is electrically connected with the negative electrode, The lithium ion battery characterized by the above-mentioned. The method of claim 1,
The electrically insulating layer and the electrically conductive layer have a through hole filled with the electrolyte and penetrating from the positive electrode to the negative electrode. delete Battery outer container,
The positive electrode,
Negative,
An electrical insulation layer provided between the positive electrode and the negative electrode;
In a lithium ion battery provided with an electrolyte,
An electric conductive layer is provided in the electric insulating layer between the positive electrode and the negative electrode,
The electrically conductive layer is electrically independent of the positive electrode and the negative electrode, and has a lead wire for electrical connection and an electrical contact with the battery outer container. The method of claim 1,
The electrically conductive layer is a lithium ion battery, characterized in that it comprises at least one of metal, alloy, carbon, conductive metal oxide, conductive polymer. The method of claim 1,
The electrical insulation layer comprises at least one of polypropylene sheet, polyethylene sheet, polyolefin resin, polyester resin, fluorine resin, polyimide resin. Battery outer container,
The positive electrode,
Negative,
An electrical insulation layer provided between the positive electrode and the negative electrode;
In the manufacturing method of a lithium ion battery provided with an electrolyte,
Forming an electrode winding body or an electrode laminate by forming an electric insulation layer having an electric conductive layer therein between the positive electrode and the negative electrode;
Filling an electrode into the electrode winding body or the electrode laminate;
Performing charging after the electrolyte filling;
And applying a voltage between the positive electrode and the electrically conductive layer.
The manufacturing method of the lithium ion battery characterized by the above-mentioned. 8. The method of claim 7,
In the charging step, a voltage is applied between the positive electrode and the electrically conductive layer to perform the charging while measuring a potential difference and a current between the positive electrode and the electrically conductive layer. 9. The method of claim 8,
In the charging step, an electrode potential lower than that of the positive electrode is applied to the electrically conductive layer. 8. The method of claim 7,
And a voltage is applied between the positive electrode and the electrically conductive layer after the step of charging to measure the potential difference and the current between the positive electrode and the electrically conductive layer.

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