JP5452202B2 - Lithium ion battery and manufacturing method thereof - Google Patents

Description

  The present invention relates to a lithium ion secondary battery and a method for manufacturing the same.

  Lithium ion secondary batteries are used as power sources for portable information devices such as notebook personal computers and mobile phones, portable acoustic devices, radios, and power tools because of their high energy density. Lithium ion secondary batteries also have the advantages of high capacity and high output. For this reason, in recent years, it has also been used as a power source for power storage systems such as an electric vehicle, a hybrid electric vehicle using both an internal combustion engine and an electric motor (hereinafter, both are referred to as an electric vehicle), and an uninterruptible power supply.

Such a lithium ion secondary battery includes a positive electrode using a positive electrode active material capable of releasing and storing lithium ions by charging and discharging, and a negative electrode using a negative electrode active material capable of storing and releasing lithium ions by charging and discharging. These are superposed through separators and are infiltrated into the electrolytic solution. More specifically, materials such as lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium manganate (LiMn ₂ O ₄ ) are used for the positive electrode, and lithium ions such as carbon materials are stored and released for the negative electrode. Lithium ion secondary batteries using each possible material are widely used.

  The positive electrode active material as described above does not have sufficient electronic conductivity. Therefore, in the positive electrode, in general, the positive electrode active material contains conductive powder that is low-cost and stable in the battery, such as graphite and carbon black, as a conductive auxiliary agent, and a binder is further added and mixed. The positive electrode mixture produced in this way is used. On the other hand, the carbon material used as the negative electrode active material is in a state where 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 ensuring 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 wound type or a laminated type in order to increase capacity and output. That is, a positive electrode and a negative electrode in which an active material is applied to a metal foil serving as a current collector are wound or stacked with a separator interposed therebetween, and the wound body or the stacked body is stored in a metal cylindrical or rectangular battery outer container. doing.

  After the wound body or the laminated body is stored in the battery outer case, the electrolytic solution is subsequently injected, and the lid is attached 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 such a method is given a function as a battery by the first charge after the assembly.

  In the battery raw material and the manufacturing process described above, an internal short circuit may occur if a metal foreign object enters the battery. The mixed metal foreign matter dissolves on the positive electrode and diffuses as ions, and when it reaches the negative electrode, the metal re-deposits. As deposition progresses and the metal grows toward the positive electrode, it becomes an electrical conduction path, and eventually an internal short circuit occurs between the negative electrode and the positive electrode. When the internal short circuit occurs, the charged electricity is consumed, the usable capacity is reduced, or even if an attempt is made to charge the battery, a current flows through the internal short circuit part, and charging does not proceed.

  In order to sort out batteries that are contaminated with metal foreign matter, in Patent Document 1, after charging, the battery is separated from the charging circuit and allowed to stand, and the change in the open circuit voltage of the battery is measured. The product is defective.

  Further, the following method has been proposed as a method for suppressing such an internal short circuit. Patent Documents 2 and 3 describe a method in which a metallic foreign material is dissolved and diffused electrochemically and is not deposited on the negative electrode. Patent Document 4 describes a method in which a substance that traps impurities including cations is contained in a battery and is not deposited as a metal.

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

  In the method described in Patent Document 1, there is a problem that it takes time until it can be determined as a defective product in the configuration of the conventional positive electrode, negative electrode, and separator.

  The methods described in Patent Documents 2 to 4 also take time from dissolution to diffusion. When the mass of the metal foreign matter is large, the diffusion becomes insufficient, and metal ions may reach the negative electrode and precipitate.

  Therefore, an object of the present invention is to provide a lithium ion secondary battery and a method for manufacturing the same, which can detect an internal short circuit due to the mixing of a metal foreign substance with higher sensitivity earlier than before.

In order to solve the above-described problems, a lithium ion secondary battery of the present invention includes a battery outer container, a positive electrode, a negative electrode, an electrical insulating layer provided between the positive electrode and the negative electrode, and an electrolyte. In the lithium ion battery, an electrical conductive layer is provided in an electrical insulating layer between the positive electrode and the negative electrode, and the electrical conductive layer is electrically connected to the negative electrode .

  According to the present invention, it is possible to provide a lithium ion secondary battery capable of detecting an internal short circuit due to the mixing of a metal foreign matter at an early stage with high sensitivity and a method for manufacturing the same.

It is the cross-sectional schematic diagram of the electrode vicinity of the lithium ion secondary battery of this invention. It is the cross-sectional schematic diagram of the electrode vicinity of the conventional lithium ion secondary battery. It is the cross-sectional schematic of the formation process of the electrically conductive layer and electrical insulating layer which have a through-hole. It is the cross-sectional schematic and enlarged view of the electrically conductive layer and electrical insulating layer which have a through-hole. It is the upper surface outline schematic diagram of the electrode lamination type lithium ion secondary battery which has the structure of the present invention. 1 is a schematic cross-sectional view of an electrode laminate type lithium ion secondary battery having the structure of the present invention. 1 is a schematic external view of an electrode winding type lithium ion secondary battery having a structure of the present invention. 1 is a schematic cross-sectional view of an electrode wound body type lithium ion secondary battery having the structure of the present 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 schematic cross-sectional view of the vicinity of the electrode of the lithium ion secondary battery of this example. The battery according to this example includes a positive electrode 16 having a positive electrode side current collector 6 and a positive electrode side mixture layer 5, a negative electrode 15 having a negative electrode side current collector 1 and a negative electrode side mixture layer 2, and a positive electrode 16. And an electric insulating layer 3 provided between the negative electrode 15 and an electric conductive layer 4 provided in the electric insulating layer 3.

  The positive electrode 16 is composed of lithium manganate, which is one of lithium transition metal composite oxides, as an active material, carbon powder as a conductive additive, and polyvinylidene fluoride (hereinafter abbreviated as PVDF) as a binder. The slurry dispersed and kneaded (hereinafter abbreviated as NMP) was applied to the positive electrode side current collector 6 made of Al to form a positive electrode side mixture layer 5, and dried to prepare.

  The negative electrode 15 is a carbon powder that can occlude and release lithium ions as an active material, and a slurry obtained by dispersing and kneading PVDF in NMP as a binder is applied to the negative electrode side current collector 1 made of Cu to apply a negative electrode side mixture layer 2 and dried.

  The electric conductive layer 4 and the electric insulating layer 3 having a through hole between the positive electrode 16 and the negative electrode 15 were produced as follows. Among those used as separators for lithium ion secondary batteries, a microporous polypropylene sheet and a polyethylene sheet each having a thickness of 18 μm were prepared. These become the electrical insulating layer 3. A Cu layer having a thickness of about 0.5 μm was formed on one side of the polypropylene sheet using an ion beam sputtering apparatus to form an electrically conductive layer having a through hole ((1) and (2) in FIG. 3). On this Cu layer, another polyethylene sheet was laminated and thermocompression bonded ((3) and (4) in FIG. 3). As shown in (4) of FIG. 3, a sheet having a three-layer structure of polypropylene / Cu / polyethylene was thereby obtained. Hereinafter, this is referred to as a separator (A).

  As shown in FIG. 4, the electric conductive layer 4 and the electric insulating layer 3 need to be microporous having through-holes 7 in order to permeate an electrolyte (not shown) and maintain ionic conductivity. . The through hole 7 penetrates from the positive electrode 16 to the negative electrode 15. The average pore diameter of the through-holes 7 is preferably 0.05 to 5 μm from the viewpoint of electrolyte permeability, separation between the positive electrode 16 and the negative electrode 15 and prevention of passage of the peeled electrode mixture particles. When an electrolyte is injected in the battery assembly process, the through hole 7 is filled with the electrolyte, and ions in the electrolyte can move between the positive electrode and the negative electrode.

  Here, although the thickness of the electrical insulating layer is 18 μm, the smaller the distance between the positive electrode 16 and the electrical conductive layer 4, the earlier it can detect the contamination of metallic foreign matter with high sensitivity. The thickness may be further reduced as long as the property is maintained.

  Here, although the ion beam sputtering apparatus is used to form the electrically conductive layer 4, an RF sputtering apparatus, a magnetron sputtering apparatus, or a vacuum evaporation apparatus may be used. Since the underlying polypropylene sheet has through-holes 7, when a Cu layer having a thickness of about 0.05 to 20 μm is formed thereon, the through-holes 7 are maintained, electric conductivity is also exhibited, and the through-holes 7 are provided. It becomes an electrically conductive layer.

Cu is used as an example for the electrically conductive layer, but other materials than Cu can be used as long as they have electrical conductivity, do not form an alloy with Li and do not dissolve in the electrolyte, such as Ni or carbon. Also, conductive metal oxides such as indium tin oxide (ITO) and MnO ₂ can be used. In addition, metals, alloys, and conductive polymers can be used.

  In addition to the polypropylene sheet and the polyethylene sheet, other polyolefin resin, polyester resin, polyimide resin, and fluororesin sheet having through holes may be used.

  Furthermore, you may use the lamination sheet which laminated | stacked the polypropylene and polyethylene which have a through-hole mutually.

  A Cu foil serving as a lead wire for electrical connection was pressed and attached to the end of the separator (A). Subsequently, the positive electrode 16, the separator (A), the negative electrode 15, and the separator (A) were sequentially stacked to produce an electrode laminate 14.

Next, a lithium ion secondary battery incorporating the electrode laminate 14 is shown in FIGS. The manufactured electrode laminate 14 was housed in an aluminum laminate type battery outer casing 12, and electrical connection was established between the electrode laminate 14 and the terminals 8, 9, 14 attached to the battery outer casing 12 by lead wires. . The positive electrode of the electrode laminate 14 was connected to the positive electrode terminal 8, the negative electrode of the electrode laminate 14 was connected to the negative electrode terminal 13, and the electric conduction layer 4 was connected to the terminal 10 connected to the electric conduction layer. Thereafter, an 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 sealed with thermocompression bonding and an adhesive, and the batteries shown in FIGS. 5 and 6 were assembled.

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

  During charging, a battery voltage of −4.2 V (referenced to the positive electrode) is applied to the electric conduction layer 4 through the terminal 10 connected to the electric conduction layer, and the potential difference between the electric conduction layer 4 and the positive electrode 16 is applied. And the current was measured.

  Note that a voltage different from that of the negative electrode 15 may be applied to the electrically conductive layer 4. In order to promote dissolution and precipitation, a lower voltage, for example, −4.5 V (referenced to the positive electrode) may be applied to the electrically conductive layer as long as the electrolyte does not decompose. When the same as the negative electrode 15, the same circuit as that connected to the negative electrode 15 during charging can be used, and the control circuit is simplified.

  Alternatively, after charging is completed and the positive electrode 16 and the negative electrode 15 are disconnected from the charging / discharging circuit, a battery voltage of −4.2 V (referenced to the positive electrode) same as that of the negative electrode 15 is applied to the electric conduction layer. The potential difference and current may be measured.

Since the electrical conductive layer 4 is not particularly used after shipment of the lithium ion secondary battery, the terminal 10 connected to the electrical conductive layer is hidden by a member or connected to the electrical conductive layer before shipment after inspection. The terminal 10 and the lead wire may be removed.
(Example 2)
The positive electrode 16 and the negative electrode 15 were produced in the same manner as in Example 1.

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

An alkaline potassium permanganate solution was brought into contact with one surface of one of them, and the polyethylene sheet surface was microetched.
Subsequently, palladium was adsorbed on the micro-etched surface and catalyzed for electroless plating. Thereafter, using an electroless Cu plating method, a Cu film having a thickness of about 0.5 μm was formed to form an electrically conductive layer ((1) and (2) in FIG. 3).

  On this Cu layer, another polyethylene sheet was laminated and thermocompression bonded ((3) and (4) in FIG. 3). As shown in FIG. 3 (4), a sheet having a three-layer structure of polyethylene / Cu / polyethylene was thus obtained. Hereinafter, this is referred to as a separator (B).

  As shown in FIG. 4, the electric conductive layer 4 and the electric insulating layer 3 need to be microporous with through-holes 7 in order to allow the electrolyte to permeate and maintain ionic conductivity. The average pore diameter of the through holes is preferably 0.05 to 5 μm from the viewpoint of electrolyte permeability, separation between the positive electrode and the negative electrode, and prevention of passage of the peeled electrode mixture particles. When an electrolyte is injected in the battery assembly process, the through hole 7 is filled with the electrolyte, and ions in the electrolyte can move between the positive electrode and the negative electrode.

  Here, although the thickness of the electrical insulating layer is 18 μm, the smaller the distance between the positive electrode 16 and the electrical conductive layer 4, the earlier it can detect the contamination of metallic foreign matter with high sensitivity. The thickness may be further reduced as long as the property is maintained.

  Here, only the electroless plating method is used. However, after a Cu film is formed by the electroless plating method, a Cu film or a Ni film may be formed by electroplating using the Cu film as a seed layer. Or after attaching Cu film by dry film-forming method like Example 1, you may form Cu film or Ni film by electroplating method using it as a seed layer.

  Since the underlying polyethylene sheet has through-holes, when a Cu layer having a thickness of about 0.05 to 20 μm is formed thereon, the through-holes are maintained and electrical conductivity is also exhibited, and the electrically conductive layer having through-holes 4

  Cu is used as an example for the electrically conductive layer, but other materials than Cu can be used as long as they have electrical conductivity, do not form an alloy with Li, and do not dissolve in the electrolyte. For example, Ni is used. You can also.

Further, not only a polyethylene sheet but also a sheet of polypropylene resin, polyester resin, polyimide resin, or fluororesin having through holes may be used.
However, in the case of a polyimide resin, surface modification with an aqueous alkali hydroxide solution, ultraviolet light, plasma, or the like is necessary as a pretreatment for electroless plating.
In the case of a fluororesin, surface modification using metallic sodium-naphthalene is necessary as a pretreatment for electroless plating.

  Furthermore, you may use the lamination sheet which laminated | stacked the polyethylene and polypropylene which have a through-hole mutually.

  A Cu foil serving as a lead wire for electrical connection was pressed and attached to the end of the separator (B). Subsequently, the positive electrode, the separator (B), the negative electrode, and the separator (B) were sequentially stacked and wound up, and the electrode winding body 11 was produced.

Next, the electrode winding body 11 was housed in a Ni-plated Fe battery outer container, and electrical connection was established between the electrode winding body and the battery outer container. Thereafter, an electrolyte was injected. As the electrolyte, a solution obtained by dissolving LiPF _{6 in} a mixed solution of EC and DMC was used.

  Subsequently, the battery lid was attached to the battery outer casing and sealed by a caulking method, and the batteries shown in FIGS. 7 and 8 were assembled.

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

  During charging, a battery voltage of −4.2 V (referenced to the positive 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.

  Note that a voltage different from that of the negative electrode may be applied to the electrically conductive layer. In order to promote dissolution and precipitation, a lower voltage, for example, −4.5 V (referenced to the positive electrode) may be applied to the electrically conductive layer as long as the electrolyte does not decompose.

Alternatively, after charging is completed and the positive electrode and negative electrode are disconnected from the charge / discharge circuit, the same battery voltage of −4.2 V (referenced to the positive electrode) as that of the negative electrode is applied to the conductive layer, and the potential difference between the conductive layer and the positive electrode And the current may be measured.
(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 having a through hole between the positive electrode and the negative electrode were produced as follows. Among the separators used for lithium ion secondary batteries, two microporous polyethylene sheets having a thickness of 18 μm were prepared. These become the electrical insulating layer 4.

  On one of them, a slurry in which carbon powder and PVDF are dispersed and dissolved in NMP is applied and dried under reduced pressure at 60 to 100 ° C. to form a carbon film having a thickness of about 1 μm as an electrically conductive layer. An electrically conductive layer was formed ((1) and (2) in FIG. 3). On this carbon layer, another polyethylene sheet was stacked and thermocompression bonded ((3) and (4) in FIG. 3). As shown in FIG. 3 (4), a sheet having a three-layer structure of polyethylene / carbon / polyethylene was thus obtained. Hereinafter, this is referred to as a separator (C).

  As shown in FIG. 4, the electric conductive layer 4 and the electric insulating layer 3 need to be microporous with through-holes 7 in order to allow the electrolyte to permeate and maintain ionic conductivity. The average pore diameter of the through-holes 7 is preferably 0.05 to 5 μm from the viewpoint of electrolyte permeability, isolation between the positive electrode 16 and the negative electrode 15 and blocking the passage of the peeled electrode mixture 2 and 5 particles. When the electrolyte is injected in the battery assembly process, the through hole 7 is filled with the electrolyte, and ions in the electrolyte can move between the positive electrode 16 and the negative electrode 15.

  Here, the thickness of the electrical insulating layer 3 is set to 18 μm. However, the smaller the distance between the positive electrode 16 and the electrical conductive layer 4 is, the earlier it can detect the contamination of metallic foreign matter with high sensitivity. You may make it still thinner as long as insulation is maintained.

  Here, the slurry containing carbon powder is applied to form the electrically conductive layer. However, a solution in which a conductive polymer such as polypyrrole, polythiophene, or polyaniline is dissolved in an organic solvent may be applied.

  The underlying polyethylene sheet has through-holes, and carbon powder is applied to it, so when a carbon film with a thickness of about 0.05 to 20 μm is formed on it, the through-holes are maintained and the electrical conductivity is also improved. It is expressed and becomes an electrically conductive layer having a through hole.

  Further, not only a polyethylene sheet but also a sheet of polypropylene resin, polyester resin, polyimide resin, or fluororesin having through holes may be used.

  Furthermore, you may use the lamination sheet which laminated | stacked the polyethylene and polypropylene which have a through-hole mutually.

  A Cu foil serving as a lead wire for electrical connection was attached by pressure contact to the end of the separator (C). Subsequently, the positive electrode 16, the separator (C), the negative electrode 15, and the separator (C) were sequentially stacked to produce an electrode laminate 14.

Next, the electrode laminate 14 was housed in an aluminum laminate type battery outer casing 12, and electrical connection was established between the electrode stack and the battery outer casing. Thereafter, an electrolyte was injected. As the electrolyte, a solution obtained by dissolving LiPF _{6 in} a mixed solution of EC and DMC was used.

  Subsequently, the battery lid was attached to the battery outer container and sealed with thermocompression bonding and an adhesive, and the batteries shown in FIGS. 5 and 6 were assembled.

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

  During charging, the same battery voltage of −4.2 V (referenced to the positive electrode) as that of the negative electrode was applied to the electrically conductive layer 4, and the potential difference and current between the electrically conductive layer 4 and the positive electrode 16 were measured.

  Note that a voltage different from that of the negative electrode 15 may be applied to the electrically conductive layer 4. In order to promote dissolution and precipitation, a lower voltage, for example, −4.5 V (referenced to the positive electrode) may be applied to the electrically conductive layer as long as the electrolyte does not decompose.

Alternatively, after charging is completed and the positive electrode 16 and the negative electrode 15 are disconnected from the charge / discharge circuit, a battery voltage of −4.2 V (referenced to the positive electrode) is applied to the electrically conductive layer, and the electrically conductive layer 4 and the positive electrode 16 The potential difference and current 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 electric conductive layer 4 and the electric insulating layer 3 having a through hole between the positive electrode 16 and the negative electrode 15 were produced as follows. Among those used as separators for lithium ion secondary batteries, one microporous polyethylene sheet having a thickness of 18 μm was prepared. This becomes an electrically insulating layer. On one side of this polyethylene sheet, a Cu layer having a thickness of about 0.5 μm was formed using an ion beam sputtering apparatus to form an electrically conductive layer having through holes ((1) and (2) in FIG. 3).

On this Cu layer, a solution obtained by dispersing and dissolving PVDF in NMP was applied and dried under reduced pressure at 60 to 100 ° C. to form an electric insulating layer of about 20 μm ((3) and (4) in FIG. 3). . (4) in Fig. 3
As a result, a sheet having a three-layer structure of PVDF / Cu / polyethylene was obtained. Hereinafter, this is referred to as a separator (D).

  As shown in FIG. 4, the electric conductive layer 4 and the electric insulating layer 3 need to be microporous with through-holes 7 in order to allow the electrolyte to permeate and maintain ionic conductivity. The average pore diameter of the through holes is preferably 0.05 to 5 μm from the viewpoint of electrolyte permeability, separation between the positive electrode and the negative electrode, and prevention of passage of the peeled electrode mixture particles. When the electrolyte is injected in the battery assembly process, the through hole 7 is filled with the electrolyte, and ions in the electrolyte can move between the positive electrode 16 and the negative electrode 15.

  Here, although the thickness of the electrical insulating layer is 18 μm, the smaller the distance between the positive electrode 16 and the electrical insulating layer 3, the earlier it can detect the contamination of metallic foreign matter with high sensitivity. The thickness may be further reduced as long as the property is maintained.

  Here, although the ion beam sputtering apparatus is used to form the electrically conductive layer 4, an RF sputtering apparatus, a magnetron sputtering apparatus, or a vacuum evaporation apparatus may be used. Since the underlying polypropylene sheet has through-holes, when a Cu layer having a thickness of about 0.05 to 20 μm is formed thereon, the through-holes are maintained and also exhibit electrical conductivity, and the electrically conductive layer having the through-holes 4

As an example, Cu is used for the electrically conductive layer 4, but other materials than Cu can be used as long as they are electrically conductive, do not form an alloy with Li, and do not dissolve in the electrolyte. Conductive metal oxides such as carbon, indium tin oxide (ITO) and MnO ₂ can also be used.

  Since the underlying electrically conductive layer 4 has through-holes, when a solution in which PVDF is dispersed and dissolved in NMP to about 1 to 20 μm is applied thereon, the through-holes are maintained and electrical insulation is also exhibited. An electrically insulating layer having a through hole is obtained.

  In addition to PVDF, polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) may be used as the electrical insulating layer 3 formed on the Cu layer. Good. In order to maintain the porosity, inorganic particles such as alumina or silica may be mixed.

In addition to a polypropylene sheet, a sheet of polyethylene resin, polyester resin, polyimide resin, or fluororesin having through holes may be used.
Furthermore, you may use the lamination sheet which laminated | stacked the polypropylene and polyethylene which have a through-hole mutually.

  A Cu foil serving as a lead wire for electrical connection was attached by pressure contact to the end of the separator (D). Subsequently, the positive electrode 16, the separator (D), the negative electrode 15, and the separator (D) were sequentially stacked to produce an electrode laminate 14.

Next, the electrode laminate 14 was housed in an aluminum laminate type battery outer casing 12, and electrical connection was established between the electrode stack and the battery outer casing. Thereafter, an electrolyte was injected. As the electrolyte, a solution obtained by dissolving LiPF _{6 in} a mixed solution of EC and DMC was used.
Subsequently, the battery lid was attached to the battery outer container and sealed with thermocompression bonding and an adhesive, and the batteries shown in FIGS. 5 and 6 were assembled.

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

  During charging, a battery voltage of −4.2 V (referenced to the positive 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.

  Note that a voltage different from that of the negative electrode may be applied to the electrically conductive layer. In order to promote dissolution and precipitation, a lower voltage, for example, −4.5 V (referenced to the positive electrode) may be applied to the electrically conductive layer as long as the electrolyte does not decompose.

Alternatively, after charging is completed and the positive electrode and negative electrode are disconnected from the charge / discharge circuit, the same battery voltage of −4.2 V (referenced to the positive electrode) as that of the negative electrode is applied to the conductive layer, and the potential difference between the conductive layer and the positive electrode And the current may be measured.
(Comparative Example 1)
A battery was assembled using a positive electrode, a negative electrode, and an electrolytic solution having the same specifications as those of Examples 1 to 4 except that the electrically conductive layer was not formed on the separator.
Among separators used as separators for lithium ion secondary batteries, a porous polyethylene sheet having a thickness of 35 μm was used.

The first charge after the assembly was completed was performed at a constant voltage of 4.2V and a current value equivalent to a charge current of 1C. However, 1C is a current value for charging the battery capacity in one hour.
(Evaluation example)
In order to confirm the effect of the present invention, in the batteries of Examples 1 to 4 and Comparative Example 1, metallic foreign matters (Fe) having an average particle size of about 80 μm and about 30 μm were placed in the positive electrode and on the positive electrode surface during the electrode preparation process. 1-10 pieces were mixed.

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

During charging, a battery voltage of −4.2 V (referenced to the positive 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 4.2V, and at the same time, a short circuit current is observed. The short circuit current varies depending on the applied voltage and the electrical resistance of the short circuit part. A battery in which such a change in potential difference and a short-circuit current were observed to be larger than the behavior of a non-defective battery in which no metal foreign matter was mixed and no internal short-circuit occurred was judged to be an internal short-circuit and was selected as a defective product.

  Note that a voltage different from that of the negative electrode may be applied to the electrically conductive layer. In order to promote dissolution and precipitation, a lower voltage, for example, −4.5 V (referenced to the positive electrode) may be applied to the electrically conductive layer as long as the electrolyte does not decompose.

  Alternatively, after charging is completed and the positive electrode and negative electrode are disconnected from the charge / discharge circuit, the same battery voltage of −4.2 V (referenced to the positive electrode) as that of the negative electrode is applied to the conductive layer, and the potential difference between the conductive layer and the positive electrode And the current may be measured.

  The results are shown in Table 1. Here, a short circuit occurring between the electrically conductive layer of the present invention and the positive electrode is expressed as an internal short circuit.

平均粒径80μmの金属異物の場合、本発明の電池では，従来の電池の場合の1/12〜1/2の時間内という早期に内部短絡が起きた。

In the case of a metal foreign matter having an average particle diameter of 80 μm, the battery of the present invention caused an internal short circuit as early as 1/12 to 1/2 the time of the conventional battery.

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

  That is, according to the present invention, an internal short circuit due to a metal foreign object can be detected earlier than before. Moreover, even if it is mixed in the past, the present invention can detect an internal short circuit caused by a small metal foreign object that is overlooked because it does not cause an internal short circuit.

1: Negative electrode side current collector
2: Negative electrode mixture layer
3: Electrical insulation layer
4: Electrically conductive layer
5: Positive electrode mixture layer
6: Positive current collector
7: Through hole
8: Terminal connected to the positive electrode
9: Body of the battery case connected to the negative electrode
10: Terminal connected to the electrically conductive layer
11: Electrode wound body
12: Aluminum laminated battery case
13: Terminal connected to negative electrode
14: Electrode laminate
15: Negative electrode
16: Positive electrode

Claims (9)

A battery case,
A positive electrode;
A negative electrode,
An electrical insulating layer provided between the positive electrode and the negative electrode;
In a lithium ion battery comprising an electrolyte,
A lithium ion battery comprising an electrically conductive layer in an electrically insulating layer between the positive electrode and the negative electrode , wherein the electrically conductive layer is electrically connected to the negative electrode . In claim 1,
The lithium ion battery, wherein the electrically insulating layer and the electrically conductive layer are filled with the electrolyte and have through holes penetrating from the positive electrode to the negative electrode. A positive electrode;
A negative electrode,
An electrical insulating layer provided between the positive electrode and the negative electrode;
In a lithium ion battery comprising an electrolyte,
In the electrically insulating layer between the positive electrode and the negative electrode, an electrically conductive layer is provided,
The electrically conductive layer, lithium wherein the positive electrode and the negative electrode electrically independent, to a lead wire for electrical connection, characterized by having an electrical contact between the battery outer container Ion battery. In claim 1,
The lithium ion battery is characterized in that the electrically conductive layer is made of at least one of metal, alloy, carbon, conductive metal oxide, and conductive polymer. In claim 1,
The lithium ion battery is characterized in that the electrical insulating layer is made of at least one of a polypropylene sheet, a polyethylene sheet, a polyolefin resin, a polyester resin, a fluororesin, and a polyimide resin. A battery case,
A positive electrode;
A negative electrode,
An electrical insulating layer provided between the positive electrode and the negative electrode;
In a method for producing a lithium ion battery comprising an electrolyte,
Forming an electroconductive layer having an electroconductive layer therein between the positive electrode and the negative electrode to form an electrode winding body or an electrode laminate;
Filling the electrode winding body or electrode laminate with an electrolyte; and
Charging after the electrolyte is filled;
The manufacturing method of the lithium ion battery characterized by including the process of applying a voltage between the said positive electrode and the said electrically conductive layer. In claim 6 ,
In the charging step, a voltage is applied between the positive electrode and the electrically conductive layer, and the charging is performed while measuring a potential difference and a current between the positive electrode and the electrically conductive layer. A method for producing a lithium ion battery. In claim 7 ,
In the charging step, an electrode potential lower than that of the positive electrode is applied to the electrically conductive layer. In claim 8 ,
A lithium ion battery characterized by applying a voltage between the positive electrode and the electrically conductive layer and measuring a potential difference and a current between the positive electrode and the electrically conductive layer after the charging step. Manufacturing method.

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