JP2020198196A - battery - Google Patents

Abstract

To provide a battery capable of suppressing falling-off of an active material from an electrode.SOLUTION: A battery includes: a wound electrode including a collector having first and second faces, a first active material layer formed on the first face, and a second active material layer formed on the second face; and an insulating member provided on the electrode. At the end of the electrode on a winding outer circumference side, there is provided a single-sided forming part where only the first active material layer of the first and second active material layers is formed. The insulating member covers the boundary between the single-sided forming part and the second active material layer.SELECTED DRAWING: Figure 2

Description

The present invention relates to a battery.

In recent years, a battery having a wound structure in which a band-shaped positive electrode and a negative electrode are wound via a band-shaped separator has been widely used. Patent Document 1 has a double-sided forming portion in which active material layers are formed on both sides of the current collector, and a single-sided forming portion in which an active material layer is formed only on one side of the current collector. Describes a battery having a wound structure provided at the end of the electrode on the outer peripheral side of the wound.

Japanese Unexamined Patent Publication No. 2004-146222

However, the battery described in Patent Document 1 has a problem that the negative electrode active material is likely to fall off at the boundary between the single-sided forming portion and the double-sided forming portion provided at the end portion on the outer peripheral side of the winding.

An object of the present invention is to provide a battery capable of suppressing the occurrence of a short circuit due to the falling off of the negative electrode active material.

In order to solve the above-mentioned problems, the present invention
A current collector having a first surface and a second surface,
The first active material layer formed on the first surface and
A wound electrode having a second active material layer formed on the second surface, and
Equipped with an insulating member provided on the electrode
At the end of the winding outer peripheral side of the electrode, a single-sided forming portion is provided in which only the first active material layer of the first active material layer and the second active material layer is formed.
The insulating member is a battery that covers the boundary between the single-sided forming portion and the second active material layer.

According to the present invention, it is possible to suppress the occurrence of a short circuit due to the falling off of the negative electrode active material.

It is an exploded perspective view which shows an example of the structure of the non-aqueous electrolyte secondary battery which concerns on 1st Embodiment of this invention. It is sectional drawing along the line II-II of FIG. It is the schematic for demonstrating the winding process. FIG. 3 is an enlarged view showing a region R shown in FIG. It is a block diagram which shows an example of the structure of the electronic device which concerns on 2nd Embodiment of this invention.

Embodiments of the present invention will be described in the following order.
1 First embodiment (example of battery)
2 Second embodiment (example of electronic device)

<1 First Embodiment>
[Battery configuration]
First, with reference to FIGS. 1 and 2, an example of the configuration of a non-aqueous electrolyte secondary battery (hereinafter, simply referred to as “battery”) according to the first embodiment of the present invention will be described. As shown in FIG. 1, the battery has a flat shape. The battery is attached with a positive electrode lead (positive electrode tab) 31 and a negative electrode lead (negative electrode tab) 32, and has a flat wound electrode body 20, an electrolytic solution as an electrolyte (not shown), and these electrodes. It includes a body 20 and a case 10 for accommodating an electrolytic solution. When the battery is viewed in a plane from the direction perpendicular to its main surface, the battery has a rectangular shape.

(Case)
The case 10 is a rectangular parallelepiped thin battery can, which is made of metal. As the metal, for example, iron (Fe) plated with nickel (Ni) can be used. When a metal case is used, by connecting it to either the positive electrode or the negative electrode, the case itself can also serve as a battery terminal, and the battery can be easily miniaturized. The case 10 includes a housing portion 11 and a lid portion 12. The accommodating portion 11 accommodates the electrode body 20. The accommodating portion 11 includes a main surface portion 11A and a wall portion 11B provided on the peripheral edge of the main surface portion 11A. The main surface portion 11A covers the main surface of the electrode body 20, and the wall portion 11B covers the side surface and the end surface of the electrode body 20. A positive electrode terminal 13 is provided on a portion of the wall portion 11B facing one end surface of the electrode body 20 (the end surface on the side from which the positive electrode lead 31 and the negative electrode lead 32 are taken out). The positive electrode lead 31 is connected to the positive electrode terminal 13. The negative electrode lead 32 is connected to the inner surface of the case 10. The lid portion 12 covers the opening of the accommodating portion 11. The top of the wall portion 11B of the accommodating portion 11 and the peripheral edge portion of the lid portion 12 are joined by welding or an adhesive or the like.

(Positive lead, Negative lead)
The positive electrode lead 31 and the negative electrode lead 32 are derived from one end face of the electrode body 20. The positive electrode lead 31 and the negative electrode lead 32 are each made of a metal material such as Al, Cu, Ni, or stainless steel, and each has a thin plate shape or the like.

Sealants (adhesive films) 31A and 32A for preventing the intrusion of outside air are inserted between the case 10 and the positive electrode lead 31 and between the case 10 and the negative electrode lead 32, respectively. The sealants 31A and 32A are made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene or modified polypropylene.

(Electrode body)
As shown in FIG. 2, the electrode body 20 has a pair of flat portions 20A facing each other and a pair of curved portions 20B provided between the pair of flat portions 20A and facing each other. The electrode body 20 is provided on the positive electrode 21 having a band shape, the negative electrode 22 having a band shape, the two separators 23A and 23B having a band shape, the insulating members 25B1 and 25B2 provided on the positive electrode 21, and the negative electrode 22. It includes insulating members 26B1 and 26B2. Separators 23A and 23B are alternately provided between the positive electrode 21 and the negative electrode 22. The electrode body 20 has a structure in which a positive electrode 21 and a negative electrode 22 are laminated via a separator 23A or a separator 23B and wound in the longitudinal direction so as to be flat and spiral. The electrode body 20 is wound so that the positive electrode 21 serves as the innermost electrode and the negative electrode 22 serves as the outermost electrode. The negative electrode 22 which is the outermost electrode is fixed by the winding tape 24. The positive electrode 21, the negative electrode 22, and the separators 23A and 23B are impregnated with the electrolytic solution.

(Positive electrode)
The positive electrode 21 includes a positive electrode current collector 21A having an inner side surface (first surface) 21S1 and an outer surface (second surface) 21S2, and a positive electrode active material layer 21B1 provided on the inner side surface 21S1 of the positive electrode current collector 21A. And the positive electrode active material layer 21B2 provided on the outer surface 21S2 of the positive electrode current collector 21A. In the present specification, the "inner surface" means a surface located on the winding center side, and the "outer surface" means a surface located on the side opposite to the winding center. The thickness of the positive electrode current collector 21A is, for example, 3 μm or more and 20 μm or less. The thickness of the positive electrode active material layers 21B1 and 21B2 is, for example, 30 μm or more and 100 μm or less.

The positive electrode active material layer 21B1 is not provided on the inner side surface 21S1 of the winding outer peripheral side end portion of the positive electrode 21 (hereinafter, simply referred to as “outer peripheral side end portion”), and the inner side surface 21S1 of the positive electrode current collector 21A is exposed. The positive electrode current collector exposed portion 21D1 is provided. The outer surface 21S2 of the outer peripheral end of the positive electrode 21 is not provided with the positive electrode active material layer 21B2, but is provided with the positive electrode current collector exposed portion 21D2 in which the outer surface 21S2 of the positive electrode current collector 21A is exposed. A positive electrode lead 31 is connected to a portion of the positive electrode current collector exposed portion 21D2 corresponding to the flat portion 20A. The length of the positive electrode current collector exposed portion 21D1 in the winding direction is, for example, substantially the same as the length of the positive electrode current collector exposed portion 21D2 in the winding direction.

The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode active material layers 21B1 and 21B2 contain a positive electrode active material capable of occluding and releasing lithium. The positive electrode active material layers 21B and 21B2 may further contain at least one of a binder and a conductive agent, if necessary.

(Positive electrode active material)
As the positive electrode active material, for example, a lithium-containing compound such as a lithium oxide, a lithium phosphorus oxide, a lithium sulfide, or an interlayer compound containing lithium is suitable, and two or more of these may be mixed and used. In order to increase the energy density, a lithium-containing compound containing lithium, a transition metal element, and oxygen is preferable. Examples of such a lithium-containing compound include a lithium composite oxide having a layered rock salt type structure, a lithium composite phosphate having an olivine type structure, and the like. The lithium-containing compound is more preferably one containing at least one selected from the group consisting of Co, Ni, Mn and Fe as a transition metal element. Examples of such a lithium-containing compound, for _{example, LiNi 0.50 Co 0.20 Mn 0.30 O} 2, LiCoO 2, LiNiO 2, LiNiaCo 1-a O 2 (0 <a <1), there is LiMn ₂ O ₄ or LiFePO ₄ or the like ..

In addition to these, lithium-free inorganic compounds such as MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , NiS, and MoS can be used as the positive electrode active material capable of occluding and releasing lithium. it can.

The positive electrode active material capable of occluding and releasing lithium may be other than the above. In addition, two or more kinds of positive electrode active materials exemplified above may be mixed in any combination.

(binder)
The binder is, for example, at least one selected from the group consisting of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, styrene butadiene rubber, carboxymethyl cellulose, and a copolymer mainly composed of one of these resin materials. Seeds can be used.

(Conducting agent)
As the conductive agent, for example, at least one carbon material selected from the group consisting of graphite, carbon fiber, carbon black, acetylene black, ketjen black, carbon nanotubes, graphene and the like can be used. The conductive agent may be any material having conductivity, and is not limited to the carbon material. For example, a metal material, a conductive polymer material, or the like may be used as the conductive agent. The shape of the conductive agent includes, for example, granular, scaly, hollow, needle-shaped, tubular, and the like, but is not particularly limited to these shapes.

(Negative electrode)
The negative electrode 22 includes a negative electrode current collector 22A having an inner side surface (first surface) 22S1 and an outer side surface (second surface) 22S2, and a negative electrode active material layer 22B1 provided on the inner side surface 22S1 of the negative electrode current collector 22A. And the negative electrode active material layer 22B2 provided on the outer surface 22S2 of the negative electrode current collector 22A. The thickness of the negative electrode current collector 22A is, for example, 3 μm or more and 20 μm or less. The thickness of the negative electrode active material layers 22B1 and 22B2 is, for example, 30 μm or more and 100 μm or less.

The negative electrode active material layer 22B1 is not provided on the inner side surface 22S1 of the outer peripheral end portion of the negative electrode 22, and the negative electrode current collector exposed portion 22D1 in which the inner side surface 22S1 of the positive electrode current collector 21A is exposed is provided. The negative electrode active material layer 22B2 is not provided on the outer surface 22S2 of the outer peripheral end portion of the negative electrode 22, and the negative electrode current collector exposed portion 22D2 in which the outer surface 22S2 of the negative electrode current collector 22A is exposed is provided. The negative electrode lead 32 is connected to the portion of the negative electrode current collector exposed portion 22D1 corresponding to the flat portion 20A. The positive electrode lead 31 and the negative electrode lead 32 are provided on the same flat portion 20A side.

The length of the negative electrode current collector exposed portion 22D1 in the winding direction is about one turn longer than the length of the negative electrode current collector exposed portion 22D2 in the winding direction. That is, at the outer peripheral end of the negative electrode 22, a single-sided active material layer forming portion in which only the negative electrode active material layer 22B1 of the negative electrode active material layer 22B1 and the negative electrode active material layer 22B2 is formed on the negative electrode current collector 22A is provided. For example, about one lap is provided.

On the outermost periphery of the negative electrode 22, a portion where both the inner side surface 22S1 and the outer side surface 22S2 of the negative electrode current collector 22A are exposed (that is, the negative electrode current collector exposed portion 22D1 and the negative electrode current collector exposed portion 22D2 are formed on both sides of the positive electrode 21 The provided portion) is provided, for example, over about one round. As a result, the negative electrode current collector exposed portion 22D2 and the inner surface of the case 10 come into electrical contact with each other. Therefore, the negative electrode 22 and the case 10 can be electrically connected to further reduce the resistance.

The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The negative electrode active material layers 22B1 and 22B2 contain a negative electrode active material capable of occluding and releasing lithium. The negative electrode active material layers 22B1 and 22B2 may further contain at least one of a binder and a conductive agent, if necessary.

(Negative electrode active material)
Examples of the negative electrode active material include carbon materials such as non-graphitizable carbon, graphitizable carbon, graphite, thermally decomposed carbons, cokes, glassy carbons, calcined organic polymer compounds, carbon fibers and activated carbon. Can be mentioned. Among these, cokes include pitch coke, needle coke, petroleum coke and the like. The calcined organic polymer compound is a polymer material such as phenol resin or furan resin that is calcined at an appropriate temperature to be carbonized, and some of them are graphitizable carbon or graphitizable carbon. Some are classified as. These carbon materials are preferable because the change in crystal structure that occurs during charging / discharging is very small, a high charging / discharging capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a large electrochemical equivalent and can obtain a high energy density. Further, graphitizable carbon is preferable because excellent cycle characteristics can be obtained. Furthermore, those having a low charge / discharge potential, specifically those having a charge / discharge potential close to that of lithium metal, are preferable because high energy density of the battery can be easily realized.

(binder)
As the binder, the same binders as those of the positive electrode active material layers 21B1 and 21B2 can be used.

(Conducting agent)
As the conductive agent, the same ones as those of the positive electrode active material layers 21B1 and 21B2 can be used.

(Separator)
The separators 23A and 23B separate the positive electrode 21 and the negative electrode 22 and allow lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. Separator 23A and 23B are made of, for example, polytetrafluoroethylene, polyolefin resin (polypropylene (PP) or polyethylene (PE), etc.), acrylic resin, styrene resin, polyester resin or nylon resin, or a resin blended with these resins. It is composed of a porous film made of, and may have a structure in which two or more of these porous films are laminated.

Above all, the porous film made of polyolefin is preferable because it has an excellent short-circuit prevention effect and can improve the safety of the battery by the shutdown effect. In particular, polyethylene is preferable as a material for constituting the separators 23A and 23B because it can obtain a shutdown effect in the range of 100 ° C. or higher and 160 ° C. or lower and is also excellent in electrochemical stability. Among them, low-density polyethylene, high-density polyethylene, and linear polyethylene are preferably used because they have an appropriate melting temperature and are easily available. In addition, a material obtained by copolymerizing or blending a resin having chemical stability with polyethylene or polypropylene can be used. Alternatively, the porous film may have a structure of three or more layers in which a polypropylene layer, a polyethylene layer, and a polypropylene layer are sequentially laminated. For example, it is desirable to have a three-layer structure of PP / PE / PP and have a mass ratio [wt%] of PP to PE of PP: PE = 60:40 to 75:25. Alternatively, from the viewpoint of cost, a single-layer base material having 100 wt% PP or 100 wt% PE can be used. The method for producing the separators 23A and 23B may be wet or dry.

Nonwoven fabrics may be used as the separators 23A and 23B. As the fiber constituting the non-woven fabric, aramid fiber, glass fiber, polyolefin fiber, polyethylene terephthalate (PET) fiber, nylon fiber and the like can be used. Further, these two or more kinds of fibers may be mixed to form a non-woven fabric.

(Electrolytic solution)
The electrolytic solution is a so-called non-aqueous electrolytic solution, and contains an organic solvent (non-aqueous solvent) and an electrolyte salt dissolved in the organic solvent. The electrolyte may contain known additives in order to improve battery characteristics. Instead of the electrolytic solution, an electrolyte layer containing the electrolytic solution and a polymer compound serving as a retainer for holding the electrolytic solution may be used. In this case, the electrolyte layer may be in the form of a gel.

As the organic solvent, a cyclic carbonate ester such as ethylene carbonate or propylene carbonate can be used, and it is preferable to use one of ethylene carbonate and propylene carbonate, particularly both in combination. This is because the cycle characteristics can be further improved.

As the organic solvent, in addition to these cyclic carbonate esters, it is preferable to mix and use a chain carbonate ester such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate or methyl propyl carbonate. This is because high ionic conductivity can be obtained.

As the organic solvent, it is preferable to further contain 2,4-difluoroanisole or vinylene carbonate. This is because 2,4-difluoroanisole can further improve the discharge capacity, and vinylene carbonate can further improve the cycle characteristics. Therefore, it is preferable to mix and use these because the discharge capacity and the cycle characteristics can be further improved.

In addition to these, as organic solvents, butylene carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3 -Dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxynitrile, 3-methoxypropyronitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N- Examples thereof include dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, dimethylsulfoxide, trimethyl phosphate and the like.

A compound in which at least a part of hydrogen of these organic solvents is replaced with fluorine may be preferable because the reversibility of the electrode reaction may be improved depending on the type of electrode to be combined.

Examples of the electrolyte salt include lithium salts, and one type may be used alone or two or more types may be mixed and used. Lithium salts include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF). ₃ ) ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, difluoro [oxorat-O, O'] lithium borate, lithium bisoxalate volate, LiBr and the like. Among them, LiPF ₆ is preferable because it can obtain high ionic conductivity and further improve the cycle characteristics.

(Insulation member)
The insulating members 25B1, 25B2, 26B1, and 26B2 have, for example, a rectangular film shape, and have an adhesive surface on one surface. More specifically, the insulating members 25B1, 25B2, 26B1 and 26B2 include a base material and an adhesive layer provided on the base material. In addition, in this specification, pressure sensitive adhesion is defined as a kind of adhesion. According to this definition, an adhesive layer is considered a type of adhesive layer. The film is also defined as including a sheet. As the insulating members 25B1, 25B2, 26B1 and 26B2, for example, insulating tape is used. Examples of the material of the insulating members 25B1, 25B2, 26B1 and 26B2 include polyethylene terephthalate (PET), polyimide (PI), polyethylene (PE) and polypropylene (PP).

(Insulating member provided on the positive electrode)
The insulating member 25B1 covers the stepped portion at the boundary between the positive electrode current collector exposed portion 21D1 and the positive electrode active material layer 21B1 and the positive electrode current collector exposed portion 21D1. The insulating member 25B2 covers the stepped portion at the boundary between the positive electrode current collector exposed portion 21D2 and the positive electrode active material layer 21B2, and the positive electrode current collector exposed portion 21D2. The insulating member 25B2 covers the positive electrode lead 31 together with the positive electrode current collector exposed portion 21D2. The boundary between the positive electrode current collector exposed portion 21D1 and the positive electrode active material layer 21B1 and the boundary between the positive electrode current collector exposed portion 21D2 and the positive electrode active material layer 21B2 are formed parallel to the winding axis direction of the electrode body 20. There is.

The insulating member 25B1 is provided in a region where the positive electrode current collector exposed portion 21D1 and the negative electrode active material layer 22B2 face each other, and a region where the positive electrode current collector exposed portion 21D1 and the negative electrode current collector exposed portion 22D2 face each other. The insulating member 25B2 is provided in a region where the positive electrode current collector exposed portion 21D2 and the negative electrode active material layer 22B1 face each other, and a region where the positive electrode current collector exposed portion 21D2 and the negative electrode current collector exposed portion 22D1 face each other.

In the positive electrode 21, the outer peripheral end of the positive electrode current collector exposed portion 21D1 is exposed without being covered by the insulating member 25B1, and the outer peripheral end of the positive electrode current collector exposed portion 21D2 is insulated. It has a positive electrode current collector exposed portion 21D4 that is exposed without being covered by the member 25B2.

(Insulating member provided on the negative electrode)
The insulating member 26B1 covers a portion of the negative electrode current collector exposed portion 22D1 where the negative electrode lead 32 is provided and a portion facing the positive electrode current collector exposed portion 21D4. The insulating member 26B1 may cover almost the entire portion corresponding to the flat portion 20A of the negative electrode current collector exposed portion 22D1.

The insulating member 26B2 includes a stepped portion at the boundary 22P between the negative electrode current collector exposed portion 22D2 and the negative electrode active material layer 22B2 (that is, the boundary 22P between the single-sided active material layer forming portion and the negative electrode active material layer 22B2) and the negative electrode current collector. It covers the exposed body portion 22D2. The boundary 22P between the negative electrode current collector exposed portion 22D2 and the negative electrode active material layer 22B2 is formed parallel to the winding axis direction of the electrode body 20. It is preferable that the insulating member 26B2 also covers the portion of the negative electrode current collector exposed portion 22D2 facing the positive electrode current collector exposed portion 21D3. The positive electrode current collector exposed portion 21D3 is located on the winding outer peripheral side of the electrode body 20 with respect to the boundary 22P, and the negative electrode lead 32 is located on the winding outer peripheral side of the electrode body 20 with respect to the positive electrode current collector exposed portion 21D3. There is. The positive electrode current collector exposed portion 21D3 is located, for example, in the flat portion 20A on the opposite side of the flat portion 20A provided with the boundary 22P.

The area density of the end portion of the negative electrode active material layer 22B2 provided on the outer peripheral surface 22S2 of the negative electrode 22 on the winding outer peripheral side is higher than the area density of the portion other than the end portion. Here, "area density" means mass density [g / cm ³ ] per unit area.

In the step of applying the negative electrode mixture slurry, a bulge is formed at the end portion of the negative electrode active material layer 22B2 in the longitudinal direction. When such a raised portion is compression-molded by a roll press or the like, as described above, the area density of the end portion on the winding outer peripheral side of the negative electrode active material layer 22B2 is the area density of the portion other than the end portion. It will be higher than. Further, since a large load is likely to be applied to such a raised portion during compression molding by a roll press machine or the like, peeling is likely to occur on the back surface of the raised portion. Therefore, as described above, in the configuration in which the boundary 22P between the negative electrode current collector exposed portion 22D2 and the negative electrode active material layer 22B2 is covered with the insulating member 26B2, the area density of the end portion on the winding outer peripheral side of the negative electrode active material layer 22B2 is high. It is particularly effective to apply it to a battery having a higher area density than the area density of the portion other than the end portion.

The tip of the insulating member 26B2 on the winding outer peripheral side exceeds the region of the negative electrode current collector exposed portion 22D2 facing the positive electrode current collector exposed portion 21D3, and is located within the range on the winding center side of the negative electrode lead 32. It is preferable to do so. When the tip of the insulating member 26B2 on the winding outer peripheral side exceeds the region facing the positive electrode current collector exposed portion 21D3, contact between the positive electrode current collector exposed portion 21D3 and the negative electrode current collector exposed portion 22D2 is suppressed. Can be done. On the other hand, when the tip of the insulating member 26B2 on the outer peripheral side of the winding is closer to the winding center side than the negative electrode lead 32, it is possible to prevent the insulating member 26B2 from increasing the rigidity of the outer peripheral end of the negative electrode 22 too much. .. Therefore, since the negative electrode 22 can be easily tilted in the “negative electrode end bending step”, the negative electrode 22 is also included in the “separator cutting step” which is a subsequent step of the “negative electrode end bending step” together with the separators 23A and 23B. It can be suppressed from being cut. The details of the "negative electrode end bending step" and the "separator cutting step" will be described later.

The thickness of the insulating member 26B2 is preferably 9 μm or more and 25 μm or less. When the thickness of the insulating member 26B2 is 9 μm or more, it is effective that the negative electrode 22 is bent starting from the boundary 22P between the negative electrode current collector exposed portion 22D2 and the negative electrode active material layer 22B2 in the “bending step of the negative electrode end portion”. Can be suppressed. Therefore, it is possible to effectively prevent the negative electrode active material from falling off from the portion of the negative electrode active material layer 22B1 located on the back surface side of the boundary 22P. Therefore, it is possible to effectively suppress the occurrence of minute short circuits due to the dropout of the negative electrode active material. On the other hand, when the thickness of the insulating member 26B2 is 25 μm or less, it is possible to prevent the insulating member 26B2 from becoming excessively thick, so that the negative electrode 22 can be easily tilted in the “bending step of the negative electrode end”. Therefore, it is possible to prevent the negative electrode 22 from being cut together with the separators 23A and 23B in the "separator cutting step" which is a subsequent step of the "negative electrode end bending step".

[Battery manufacturing method]
Next, an example of a method for manufacturing a battery according to the first embodiment of the present invention will be described.

(Positive electrode manufacturing process)
The positive electrode 21 is manufactured as follows. First, for example, a positive electrode active material, a binder, and a conductive agent are mixed to prepare a positive electrode mixture, and this positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) to form a paste. To prepare a positive electrode mixture slurry of. Next, this positive electrode mixture slurry is applied to both surfaces of the positive electrode current collector 21A, the solvent is dried, and compression molding is performed by a roll press or the like to form the positive electrode active material layers 21B1 and 21B2 to obtain the positive electrode 21. At this time, the coating position of the positive electrode mixture slurry is adjusted so that the positive electrode current collector exposed portions 21D1 and 21D2 are formed at one end of the positive electrode 21.

Next, the positive electrode lead 31 is attached by welding to the positive electrode current collector exposed portion 21D2 provided at one end of the positive electrode 21. Next, the insulating members 25B1 and 25B2 are attached to the exposed positive electrode current collectors 21D1 and 21D2 provided at one end of the positive electrode 21, respectively.

(Negative electrode manufacturing process)
The negative electrode 22 is manufactured as follows. First, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a paste-like negative electrode mixture slurry. To do. Next, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 22A, the solvent is dried, and the negative electrode active material layers 22B1 and 22B2 are formed by compression molding with a roll press or the like to obtain the negative electrode 22. At this time, the coating position of the negative electrode mixture slurry is adjusted so that the negative electrode current collector exposed portions 22D1 and 22D2 are formed at one end of the negative electrode 22.

Next, the negative electrode lead 32 is attached to the negative electrode current collector exposed portion 22D1 provided at one end of the negative electrode 22 by welding. Next, the insulating members 26B1 and 26B2 are attached to the positive electrode current collector exposed portions 21D1 and 21D2 provided at the other end of the negative electrode 22, respectively.

(Rolling process)
As shown in FIG. 3, the electrode body 20 is manufactured by winding the positive electrode 21, the negative electrode 22, and the separators 23A and 23B by the winding core 41 for a specified length. The positive electrode 21 and the negative electrode 22 are cut to a predetermined length in advance.

(Bending process at the negative end)
With a jig (not shown), the outer peripheral end of the negative electrode 22 is tilted in the direction (downward) indicated by the arrow 43. As shown in FIG. 4, the outer peripheral end portion of the negative electrode 22 that is tilted in this way includes a boundary 22P between the negative electrode current collector exposed portion 22D2 and the negative electrode active material layer 22B2. Since the insulating member 26B2 covers the boundary 22P, the rigidity of the negative electrode 22 at the boundary 22P can be increased, and the outer peripheral end of the negative electrode 22 can be prevented from bending from the boundary 22P as a starting point. Therefore, it is possible to prevent the negative electrode active material from falling off from the portion of the negative electrode active material layer 22B1 located on the back surface side of the boundary 22P. Therefore, it is possible to suppress the occurrence of minute short circuits due to the dropout of the negative electrode active material. The outer peripheral end of the negative electrode 22 may be tilted by means other than the jig.

Since the negative electrode lead 32 is attached to the outer peripheral end of the negative electrode 22 in advance, the negative electrode lead 32 can function as a weight when the outer peripheral end of the negative electrode 22 is tilted. Therefore, the outer peripheral end of the negative electrode 22 can be easily tilted. Therefore, it is possible to prevent the negative electrode 22 from being cut together with the separators 23A and 23B in the "separator cutting step" which is a subsequent step of the "negative electrode end bending step".

(Separator cutting process)
The separators 23A and 23B are supported above the electrode body 20 by a support member (not shown), and then the separators 23A and 23B are cut by the cutter 42. After cutting, the outer peripheral end of the negative electrode 22, which is the outermost electrode, is fixed with the winding stop tape 24. As a result, the electrode body 20 is obtained.

In the state after winding shown in FIG. 3, the negative electrode 22 is attracted to the separator 23A by static electricity. If the separators 23A and 23B are cut in this state, the negative electrode 22 is also cut together with the separators 23A and 23B, and the negative electrode 22 may be shorter than the specified length. By tilting the outer peripheral end of the negative electrode 22 as described above and then cutting the separators 23A and 23B, it is possible to prevent the negative electrode 22 from being cut together with the separators 23A and 23B.

(Seal process)
The electrode body 20 is sealed by the case 10 as follows. First, the electrode body 20 and the electrolytic solution are accommodated in the accommodating portion 11. Subsequently, the positive electrode lead 31 is connected to the positive electrode terminal 13 installed in the case 10, and the negative electrode lead 32 is connected to the inner surface of the case 10. Next, the opening of the accommodating portion 11 is covered with the lid portion 12, and the accommodating portion 11 and the peripheral edge portion of the lid portion 12 are joined by welding or an adhesive or the like. As a result, a battery is obtained.

[effect]
In the battery according to the first embodiment, at the outer peripheral end of the negative electrode 22, the insulating member 26B2 is a boundary 22P between the negative electrode active material layer 22B2 and the negative electrode current collector exposed portion 22D2 (that is, the single-sided active material layer forming portion and the negative electrode). It covers the boundary 22P) between the active material layers 22B2. As a result, the rigidity of the negative electrode 22 at the boundary 22P can be increased, and bending of the negative electrode 22 starting from the boundary 22P in the “bending step of the negative electrode end portion” can be suppressed. Therefore, it is possible to prevent the negative electrode active material from falling off from the portion of the negative electrode active material layer 22B1 located on the back surface side of the boundary 22P. Therefore, it is possible to suppress the occurrence of minute short circuits due to the dropout of the negative electrode active material.

The portion of the negative electrode active material layer 22B1 located on the back surface side of the boundary 22P is particularly susceptible to damage during compression molding of the negative electrode 22. Therefore, the effect of covering the boundary 22P with the insulating member 26B2 is remarkably exhibited in the battery produced by compression molding the negative electrode 22 with a roll press or the like. However, the above effect is exhibited even in a battery in which the negative electrode 22 is not compression-molded by a roll press or the like.

<2 Second embodiment>
In the second embodiment, the electronic device including the battery according to the first embodiment described above will be described.

Hereinafter, an example of the configuration of the electronic device 100 according to the second embodiment of the present invention will be described with reference to FIG. 7. The electronic device 100 includes an electronic circuit 110 of the main body of the electronic device and a battery pack 120. The battery pack 120 is electrically connected to the electronic circuit 110 via the positive electrode terminal 123a and the negative electrode terminal 123b. The electronic device 100 may have a structure in which the battery pack 120 can be attached and detached.

Examples of the electronic device 100 include a notebook personal computer, a tablet computer, a mobile phone (for example, a smartphone), a personal digital assistant (PDA), a display device (LCD (Liquid Crystal Display), and an EL (Electro Luminescence). ) Display, electronic paper, etc.), imaging device (for example, digital still camera, digital video camera, etc.), audio equipment (for example, portable audio player), game equipment, cordless phone handset, electronic book, electronic dictionary, radio, headphones, navigation System, memory card, pacemaker, hearing aid, power tool, electric shaver, refrigerator, air conditioner, TV, stereo, water heater, microwave oven, dishwasher, washing machine, dryer, lighting equipment, toys, medical equipment, robot, road conditioner Alternatively, a signal device and the like can be mentioned, but the present invention is not limited to these.

(Electronic circuit)
The electronic circuit 110 includes, for example, a CPU (Central Processing Unit), a peripheral logic unit, an interface unit, a storage unit, and the like, and controls the entire electronic device 100.

(Battery pack)
The battery pack 120 includes an assembled battery 121 and a charge / discharge circuit 122. The battery pack 120 may further include an exterior material (not shown) that houses the assembled battery 121 and the charge / discharge circuit 122, if necessary.

The assembled battery 121 is configured by connecting a plurality of secondary batteries 121a in series and / or in parallel. The plurality of secondary batteries 121a are connected, for example, in n parallel m series (n and m are positive integers). Note that FIG. 7 shows an example in which six secondary batteries 121a are connected in two parallels and three series (2P3S). As the secondary battery 121a, the battery according to the first embodiment described above is used.

Here, a case where the battery pack 120 includes an assembled battery 121 composed of a plurality of secondary batteries 121a will be described. However, the battery pack 120 includes one secondary battery 121a instead of the assembled battery 121. It may be adopted.

The charge / discharge circuit 122 is a control unit that controls the charge / discharge of the assembled battery 121. Specifically, at the time of charging, the charging / discharging circuit 122 controls charging of the assembled battery 121. On the other hand, at the time of discharging (that is, when the electronic device 100 is used), the charging / discharging circuit 122 controls the discharging to the electronic device 100.

As the exterior material, for example, a case made of a metal, a polymer resin, a composite material thereof, or the like can be used. Examples of the composite material include a laminate in which a metal layer and a polymer resin layer are laminated.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[Examples 1 to 5]
(Positive electrode manufacturing process)
The positive electrode was produced as follows. First, 91 parts by mass of lithium cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. Then, it was dispersed in N-methyl-2-pyrrolidone to prepare a paste-like positive electrode mixture slurry.

Next, a strip-shaped aluminum foil having a thickness of 19 μm was prepared as a positive electrode current collector, a positive electrode mixture slurry was applied to both sides of the aluminum foil, dried, and then compression-molded with a roll press to form a positive electrode active material layer. A positive electrode was obtained by forming the above. At this time, the coating position of the positive electrode mixture slurry was adjusted so that exposed portions of the positive electrode current collector were formed on both sides of one end of the positive electrode. Next, among the exposed positive electrode current collectors formed on both sides of one end of the positive electrode, an aluminum positive electrode lead is welded to the exposed positive electrode current collector which becomes the outer surface of the outer peripheral end after winding. And attached. Next, insulating tapes were attached to the exposed portions of the positive electrode current collector formed on both sides of one end of the positive electrode (see FIG. 2).

(Negative electrode manufacturing process)
The negative electrode was manufactured as follows. First, 97 parts by mass of artificial graphite powder as a negative electrode active material and 3 parts by mass of polyvinylidene fluoride as a binder are mixed to form a negative electrode mixture, and then dispersed in N-methyl-2-pyrrolidone to make a paste. A negative electrode mixture slurry was prepared.

Next, a strip-shaped copper foil having a thickness of 6 μm was prepared as a negative electrode current collector, and the negative electrode mixture slurry was applied to both sides of the copper foil and dried, and then compression molded by a roll press to form a negative electrode active material layer. By forming, a negative electrode was obtained. At this time, the coating position of the negative electrode mixture slurry was adjusted so that the negative electrode current collector exposed portions were formed on both sides of one end of the negative electrode. Next, of the exposed negative electrode current collectors formed on both sides of one end of the negative electrode, a nickel negative electrode lead is welded to the exposed negative electrode current collector which becomes the inner side surface of the outer peripheral end after winding. And attached. Next, insulating tapes were attached to the exposed portions of the negative electrode current collector formed on both sides of one end of the negative electrode (see FIG. 2). At this time, the sticking position of the insulating tape was adjusted so that the insulating tape covered the boundary between the negative electrode active material layer and the exposed portion of the current collector on the outer surface of the outer peripheral end portion of the negative electrode. Further, as the insulating tape, as shown in Table 1, tapes having different thicknesses Tt were used in Examples 1 to 5. The thickness Tt of the insulating tape in Table 1 was measured using a negative electrode taken out by disassembling the battery after manufacturing the battery.

(Preparation process of electrolyte)
The electrolyte was prepared as follows. First, ethylene carbonate (EC) and propylene carbonate (PC) were mixed so that the mass ratio was EC: PC = 1: 1 to prepare a mixed solvent. Next, an electrolytic solution was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt in this mixed solvent so as to be 1.0 mol / kg.

(Battery manufacturing process)
The battery was manufactured as follows (see FIGS. 3 and 4). First, the positive electrode, the negative electrode and the two separators were wound by a winding core to obtain a wound electrode body having a flat shape. As the separator, a microporous polyethylene film having a thickness of 25 μm was used. Subsequently, the outer peripheral end of the negative electrode was tilted with a jig. Next, the separator was supported above the electrode body by the support member, and then the separator was cut by the cutter. Then, the outer peripheral end of the negative electrode, which is the outermost electrode, was fixed with a winding stop tape. As a result, an electrode body was obtained. Next, the electrode body and the electrolytic solution were accommodated in the accommodating portion of the metal can, the opening of the accommodating portion was covered with the lid portion, and the peripheral portion of the accommodating portion and the lid portion were joined to seal the metal can. As a result, the target battery was obtained.

[Comparative Example 1]
The insulating tape is attached so that the insulating tape does not cover the boundary between the negative electrode active material layer and the exposed part of the current collector on the outer surface of the outer peripheral end of the negative electrode and is located on the outer peripheral side of the winding after winding. A battery was obtained in the same manner as in Example 1 except that the alignment position was adjusted.

(Occurrence rate of short-circuit voltage abnormality)
The incidence of short-circuit voltage anomalies was evaluated as follows. The occurrence of a short circuit was determined by temporarily applying 100 kV and measuring the resistance while pressing the electrode body after winding the electrode body. The ratio of the total number of electrode bodies in which short circuits occurred to the number of electrode bodies manufactured was defined as the occurrence rate of short-circuit voltage abnormalities. The number of electrode bodies manufactured was 100.

(Currence rate of poor winding)
The incidence of poor winding was evaluated as follows. In the step of manufacturing the winding type electrode body using the winding device, it was confirmed whether or not the negative electrode could not be wound and the negative electrode was cut by the cutter and the device was stopped. The ratio of the total number of electrode bodies in which the apparatus was stopped to the number of manufactured pieces in the process was defined as the incidence of winding defects. The number of electrode bodies manufactured was 100.

表１中における“境界”とは、負極の外周側端部の外側面における負極活物質層と集電体露出部の境界を意味する。 Table 1 shows the battery configurations and evaluation results of Examples 1 to 5 and Comparative Example 1.

The “boundary” in Table 1 means the boundary between the negative electrode active material layer and the current collector exposed portion on the outer surface of the outer peripheral end portion of the negative electrode.

The following can be seen from Table 1.
In the batteries of Examples 1 to 5 in which the insulating tape covers the boundary between the negative electrode active material layer and the negative electrode current collector exposed portion, the comparison in which the insulating tape does not cover the boundary between the negative electrode active material layer and the negative electrode current collector exposed portion. Compared with the battery of Example 1, the occurrence rate of short-circuit voltage abnormality can be reduced.
In the batteries 1 to 5 in which the thickness of the insulating tape is 25 μm or less, the occurrence rate of winding defects can be reduced to 0%.
In the batteries 1 to 4 in which the thickness of the insulating tape is 9 μm or more, the occurrence rate of short-circuit voltage abnormality can be set to 0%.

Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments and examples, and various modifications based on the technical idea of the present invention are possible. Is.

For example, the configurations, methods, processes, shapes, materials, numerical values, etc. given in the above-described embodiments and examples are merely examples, and if necessary, different configurations, methods, processes, shapes, materials, numerical values, etc. May be used. In addition, the configurations, methods, processes, shapes, materials, numerical values, and the like of the above-described embodiments and examples can be combined with each other as long as they do not deviate from the gist of the present invention.

Further, the chemical formulas of the compounds and the like exemplified in the above-described embodiments are representative, and the general names of the same compounds are not limited to the stated valences and the like. Further, in the numerical range described stepwise in the above embodiment, the upper limit value or the lower limit value of the numerical range of one step may be replaced with the upper limit value or the lower limit value of the numerical range of another step. Further, unless otherwise specified, the materials exemplified in the above-described embodiments may be used alone or in combination of two or more.

Further, in the above-described embodiment, the case where the present invention is applied to the negative electrode 22 has been described, but the present invention may be applied to the positive electrode 21. That is, the configurations of the positive electrode 21 and the negative electrode 22 may be interchanged in the first embodiment described above.

10 Case 11 Accommodating part 11A Main surface part 11B Wall part 12 Lid part 20 Electrode body 20A Flat part 20B Curved part 21 Positive electrode 21A Positive electrode current collector 21B1, 21B2 Positive electrode active material layer 22 Negative electrode 22A Negative electrode current collector 22B1, 2B2 Negative electrode active material Layer 23A, 23B Separator 24 Wind-up tape 25B1, 25B2, 26B1, 26B2 Insulation member 21D1, 21D2, 21D3, 21D4 Positive electrode current collector exposed part 22D1, 22D2 Negative electrode current collector exposed part 21S1, 22S1 Inner side surface 21S2, 22S2 31 Positive electrode lead 32 Negative electrode lead 41 Winding core 42 Cutter 100 Electronic equipment 120 Battery pack

Claims (4)

A current collector having a first surface and a second surface,
With the first active material layer formed on the first surface,
A wound electrode having a second active material layer formed on the second surface, and
It is provided with an insulating member provided on the electrode.
At the end on the winding outer peripheral side of the electrode, a single-sided forming portion is provided in which only the first active material layer of the first active material layer and the second active material layer is formed.
The insulating member is a battery that covers the boundary between the one-sided forming portion and the second active material layer. The battery according to claim 1, wherein the thickness of the insulating member is 9 μm or more and 25 μm or less. The battery according to claim 1 or 2, wherein the electrode further includes an electrode tab provided at an end on the winding outer peripheral side of the electrode. The battery according to claim 1, wherein the area density of the end portion on the winding outer peripheral side of the second active material layer is higher than the area density of the portion other than the end portion.

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