WO2017145212A1

WO2017145212A1 - Thin battery

Info

Publication number: WO2017145212A1
Application number: PCT/JP2016/005231
Authority: WO
Inventors: 裕也浅野; 智博植田; 陽子佐野
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2016-02-24
Filing date: 2016-12-27
Publication date: 2017-08-31
Also published as: JPWO2017145212A1

Abstract

A thin battery includes an electrode group, a nonaqueous electrolyte, and an external body. The electrode group is equipped with a first electrode, a second electrode, and a separator. The first electrode includes a first collector sheet and a first active material layer, and the second electrode includes a second collector sheet and a second active material layer. The first collector sheet includes a first tab extending in a first direction and has a first lead connected to the first tab. The second collector sheet includes a second tab extending in the first direction and has a second lead connected to the second tab. The external body has a sealing margin for holding the first lead and the second lead. A linear spacer is arranged between the sealing margin and the edge of the active material layer close to the sealing margin, a first gap is formed between the sealing margin and the spacer, and a second gap is formed between the spacer and the edge of the active material layer close to the sealing margin.

Description

Thin battery

The present invention relates to a thin battery including a sheet-like electrode group.

In recent years, as a power source for small electronic devices such as bio-applied devices, mobile phones, audio recording / playback devices, watches, video and still image cameras, liquid crystal displays, calculators, IC cards, temperature sensors, hearing aids, pressure-sensitive buzzers, etc. Thin batteries are used. Such a thin battery is required to have flexibility. For example, a thin battery mounted on a biological sticking type device or a wearable portable terminal is required to be deformed so as to follow the movement of the living body.

Patent Document 1 proposes that in a thin electrochemical device, a tab is formed on a current collector plate, and a lead drawn out of the exterior body is connected to the tab. Further, it has been proposed that a tab is sandwiched with a fixture together with a lead, and is further sandwiched with a seal portion of an exterior body.

The inside of the outer package of the thin battery is decompressed in a state where the electrode group and the non-aqueous electrolyte are accommodated.

Therefore, the appearance of the thin battery tends to be uneven depending on the shape of the electrode group. Therefore, Patent Document 2 proposes to arrange a spacer in the exterior body in order to suppress wrinkles and distortion in the exterior body.

JP 2006-278897 A JP 2011-210661 A

However, in the methods proposed by Patent Documents 1 and 2, the rigidity in the vicinity of the seal portion is increased, and when the thin battery is bent, high stress is easily generated in the exterior body, and cracks are easily generated in the exterior body. Such a defect tends to concentrate in the vicinity of the seal portion from the stepped portion where the thickness of the electrode group changes.

In view of the above, a thin battery according to one aspect of the present disclosure includes a sheet-like electrode group, a nonaqueous electrolyte impregnated in the electrode group, and an exterior body that hermetically stores the electrode group and the nonaqueous electrolyte. The electrode group includes a sheet-like first electrode, a sheet-like second electrode, and a separator disposed between the first electrode and the second electrode. The second active material includes a first active material layer attached to the surfaces of the current collector sheet and the first current collector sheet, and the second electrode is attached to the surfaces of the second current collector sheet and the second current collector sheet. Including layers. The first current collector sheet includes a first tab extending in a first direction from a part of one side of the first current collector sheet, and a first lead drawn out of the exterior body is connected to the first tab. The second current collector sheet includes a second tab extending in a first direction from a part of one side of the second current collector sheet, and a second lead drawn out of the exterior body by the second tab Is connected. The exterior body has a sealing margin for sandwiching the first lead and the second lead, and a line is formed between the sealing margin and the end portion on the sealing margin side of the first active material layer and the second active material layer. The first spacer is formed between the sealing margin and the spacer, and the spacer and the end of the first active material layer and the second active material layer on the sealing margin side A second gap is formed between them.

According to the thin battery according to the present disclosure, the first gap is formed between the sealing margin and the line-shaped spacer, and the second gap is formed between the spacer and the end portion on the sealing margin side of the active material layer. Therefore, the exterior body is curved along the spacer, and the unfolded length when the exterior body is stretched becomes long. Thereby, a margin for absorbing expansion and contraction is generated in the exterior body. Therefore, when the thin battery is bent, cracks are unlikely to occur at the stepped portion where the thickness of the electrode group changes.

FIG. 1 is a plan view in which a part of an outer package of a thin battery according to an embodiment of the present invention is cut away. FIG. 2 is a longitudinal sectional view of a main part of the thin battery. FIG. 3 is a conceptual diagram showing a state of the exterior body when the thin battery is bent.

A thin battery according to an embodiment of the present invention includes a sheet-like electrode group, a nonaqueous electrolyte impregnated in the electrode group, and an exterior body that hermetically stores the electrode group and the nonaqueous electrolyte. The electrode group includes a sheet-like first electrode, a sheet-like second electrode, and a separator disposed between the first electrode and the second electrode. The first electrode includes a first current collector sheet and a first active material layer attached to the first current collector sheet. The second electrode includes a second current collector sheet and a second active material layer attached to the second current collector sheet. The first current collector sheet has a first tab extending in a first direction from a part of one side of the first current collector sheet, and the second current collector sheet is one side of the second current collector sheet. A second tab extending in a first direction from a portion of the first tab. A first lead that is pulled out in the first direction is connected to the first tab, and a second lead that is pulled out in the first direction is connected to the second tab. Yes.

The exterior body has a sealing margin for sandwiching the first lead and the second lead, and a line is formed between the sealing margin and the end portion on the sealing margin side of the first active material layer and the second active material layer. Shaped spacers are arranged. A first gap is formed between the sealing margin and the spacer. Further, a second gap is formed between the spacer and the end portion on the sealing margin side of the first active material layer and the second active material layer.

Note that the sealing allowance of the outer package is, for example, when the outer package is formed by bonding the peripheral portions of two film materials, or the peripheral portions other than the folds are bonded by folding one film material. The peripheral part when forming an exterior body. For example, if the outer shape of the exterior body is a rectangle or a shape close to a rectangle, the peripheral edge along one of the four sides serves as a sealing margin for sandwiching the first lead and the second lead.

Further, the end portion on the sealing margin side of the first active material layer and the second active material layer means the entire end portion including the first active material layer and the second active material layer. When one of the first active material layer and the second active material layer protrudes more toward the sealing margin than the other, the end of the protruding active material layer is the entire end.

The exterior body includes a first portion that faces the first active material layer and the second active material layer, a region of the first current collector sheet that does not have the first active material layer, and a second current collector sheet. It has the 2nd site | part which opposes the area | region which does not have an active material layer.

The inside of the outer package of the thin battery is depressurized while the electrode group and the nonaqueous electrolyte are accommodated. At this time, according to the said structure, the 2nd site | part of an exterior body curves along a spacer. Thereby, the expansion | deployment length when an exterior body is extended becomes long.

When the thin battery is bent, on the outer surface where the thin battery has a convex shape, the second part of the curved exterior body expands to absorb the stress. Therefore, the crack of the exterior body at the step portion of the electrode group is less likely to occur. Especially, the crack of an exterior body tends to generate | occur | produce in the edge part vicinity of the sealing margin side of a 1st active material layer and a 2nd active material layer. Therefore, when the inside of the exterior body is decompressed, it is particularly important that the second part of the exterior body enters the second gap and curves.

Also, on the outer surface where the thin battery becomes concave, the second part of the outer package is curved along the spacer in advance, so that the outer package is less likely to bulge into a convex shape. If the second part of the exterior body that has entered the first gap and the second gap has a concave shape, it enters deeper into the inside of the first gap and the second gap, so that the convex bulge is further suppressed.

Next, it is desirable that the thickness T1 of the portion where the spacer is disposed and the thickness T2 of the portion having the sealing allowance satisfy T1> T2. Thereby, the expansion | deployment length when an exterior body is extended becomes still longer. Therefore, cracks and unnecessary wrinkles in the exterior body are less likely to occur.

When the thickness of the portion where the spacer of the thin battery is arranged is not uniform, the minimum thickness of the portion where the spacer of the thin battery is arranged may be obtained as T1. Similarly, when the thickness T2 at the sealing margin of the thin battery is not uniform, the minimum thickness at the sealing margin of the thin battery may be obtained as T2.

More preferably, the thickness T1 of the portion where the spacer of the thin battery is disposed and the thickness T2 in the sealing allowance satisfy 1.1 <T1 / T2 <6.0, and 2.0 ≦ T1 / More preferably, T2 ≦ 3.0 is satisfied. Thereby, it becomes easy to ensure the deployment length when the exterior body is stretched.

A line-shaped spacer is a member having an elongated shape (bar shape, strip shape, semi-cylindrical shape, etc.). The spacer has a width that can be accommodated between the sealing margin and the end portion on the sealing margin side of the active material layer. It is desirable that the length of the spacer substantially corresponds to the width of the electrode group, and is preferably about 60 to 120% of the longer of the end portions on the sealing margin side of the first active material layer and the second active material layer. 80 to 110% is more preferable, and about 90 to 100% is more preferable. The width of the spacer is sufficiently shorter than the length of the spacer, for example, 20% or less of the length, and specifically, preferably 1.0 to 5.0 mm.

It is preferable that the spacer has a thickness capable of forming an elongated ridge between the sealing margin and the end portion on the sealing margin side of the active material layer so as not to exceed the thickness of the electrode group. The elongated ridge has a shape like a rib or a ridge along a line-shaped spacer. Such a raised portion is formed, for example, by the second portion of the exterior body entering the first gap and the second gap adjacent to both sides in the width direction of the spacer and bending along the shape of the spacer.

The material of the spacer is not particularly limited, but a thermoplastic resin having heat weldability is preferable. A spacer formed of a thermoplastic resin having a heat welding property can be fixed to any part of the current collector sheet or the tab by heat welding. Therefore, it is possible to prevent the spacer from moving from a desired position or falling off during manufacturing or when the battery is bent. The thermoplastic resin is not particularly limited, and polyolefin resin, ethylene-vinyl acetate copolymer, and the like can be used. As the polyolefin resin, polypropylene, ethylene-propylene copolymer, and the like are preferable from the viewpoint of excellent resistance to nonaqueous electrolytes.

The line-shaped spacers are arranged along the end portions on the sealing margin side of the first active material layer and the second active material layer. That is, it is desirable that the end portion on the sealing margin side of the active material layer and the length direction of the spacer are parallel or as close to parallel as possible. The angle formed by the end portion on the sealing margin side of the active material layer and the length direction of the spacer is preferably 170 to 190 degrees (°), and more preferably 180 degrees. Thereby, when a thin battery bends along the first direction, it becomes easier to bend. In addition, cracks are less likely to occur at the step portions where the thickness of the electrode group changes, and convex bulges are less likely to occur.

The thickness T1 of the portion where the spacer of the thin battery is disposed and the thickness T3 of the portion where the first active material layer and the second active material layer are disposed are 0.5 <T1 / T3 <1. 5 is preferably satisfied, and more preferably 0.7 ≦ T1 / T3 ≦ 1.2. Accordingly, the raised portion formed by the spacer does not protrude excessively in the thickness direction, the battery can be easily handled, and the battery can be easily attached to the device in use. Also here, when the thickness T3 of the portion where the first active material layer and the second active material layer of the thin battery are arranged is not uniform, the first active material layer and the second active material layer of the thin battery are arranged. What is necessary is just to obtain | require the minimum thickness of the site | part which is present as T3.

The width G of the second gap and the length L in the first direction of the first active material layer and the second active material layer preferably satisfy 0.01 <G / L <0.2, and 0.05 ≦ It is more preferable to satisfy G / L ≦ 0.15. This makes it possible to form a thin battery having a sufficient volumetric energy density and to easily ensure a sufficiently long development length when the exterior body is stretched.

It is preferable that the linear spacer is a pair of sheet members that sandwich the first tab and the second tab. In this case, one sheet member (hereinafter referred to as a spacer sheet) serving as a spacer is arranged on each side of the sheet-like electrode group. For example, a pair of spacer sheets are abutted against each other in a state where the first tab and the second tab are sandwiched, bonded together, and fixed to each tab.

For the spacer sheet, it is preferable to use, for example, a polyolefin resin which is a thermoplastic resin having a heat-welding property. The thickness of the spacer sheet may be selected according to the thickness of the thin battery, but may be, for example, 20 to 500 μm.

The spacer sheet preferably includes a core material that does not melt at the melting point of the polyolefin resin. Due to the presence of the core material, excessive deformation of the spacer sheet is avoided, and the spacer sheet can easily maintain a desired thickness. Therefore, the work of thermally welding the spacer sheet to an arbitrary part of the current collector sheet or tab is facilitated. The material of the core material is not particularly limited, but a non-woven fabric or a woven fabric formed of heat-resistant resin fibers is suitable. Examples of the heat resistant resin include polyamide, polyimide, polyamideimide, polyphenylene sulfide, polyvinylidene fluoride, and polytetrafluoroethylene.

The thickness of the thin battery is not particularly limited, but is preferably 3 mm or less, more preferably 2 mm or less, or 1.5 mm or less in consideration of flexibility. The lower limit of the thickness of the thin battery is, for example, 50 μm.

When at least a part of the non-aqueous electrolyte forms a gel electrolyte, the gel electrolyte can adhere the first active material layer and the separator and the second active material layer and the separator. it can. Thereby, although the bending performance of an electrode group is improved, on the other hand, when a battery is greatly bent, the load applied to an exterior body tends to increase. Even in such a case, the second portion of the exterior body is curved along the spacer, so that a remarkable effect of reducing the load applied to the exterior body is exhibited.

A battery-mounted device according to an embodiment of the present invention includes the thin battery and a flexible electronic device driven by power supply from the thin battery, and the thin battery and the electronic device are integrated into a sheet. It has become. Electronic devices that are integrated into a sheet with a thin battery include, for example, a bio-applied device or a wearable mobile terminal, a mobile phone, a voice recording / playback device, a wristwatch, a video and still image camera, a liquid crystal display, Calculators, IC cards, temperature sensors, hearing aids, pressure-sensitive buzzers, etc. In particular, the bio-applied device is required to be flexible because it is used in close contact with a living body. Examples of the biological sticking type device include a biological information measuring device and an iontophoresis transdermal dosage device.

The thickness of the sheet-like battery-mounted device may be thicker than the thin battery, but is preferably 5 mm or less, more preferably 3 mm or less. If the thickness of the battery-mounted device is about 5 mm or less, relatively good flexibility can be obtained. The lower limit of the thickness of the battery-mounted device is, for example, 50 μm.

The configuration of the electrode group is not particularly limited, and examples thereof include the following.

The electrode group having the simplest structure includes one first electrode, one second electrode, and a separator interposed between the first electrode and the second electrode. In this case, the first electrode may be a single-sided electrode including the first current collector sheet and the first active material layer attached to one surface thereof. The second electrode may also be a single-sided electrode including a second current collector sheet and a second active material layer attached to one surface thereof.

Next, the electrode group having a simple structure has a three-layer structure including one first electrode and two second electrodes sandwiching the first electrode. Such a thin battery has a small thickness and a sufficiently practical capacity. In this case, the second electrode may be a single-sided electrode including the second current collector sheet and the second active material layer attached to one surface thereof. On the other hand, the first electrode may be a double-sided electrode including a first current collector sheet and a first active material layer attached to both surfaces.

The electrode group having another structure includes, for example, two or more first electrodes and three or more second electrodes, and the first electrodes and the second electrodes are alternately stacked. Among such electrode groups, the simplest structure has two first electrodes, one second electrode interposed between the two first electrodes, and one each outside the two first electrodes. And a second electrode disposed. Such a thin battery has not only a small thickness but also a high capacity. In this case, the first electrode may be a double-sided electrode including a first current collector sheet and a first active material layer attached to both surfaces. One second electrode interposed between the two first electrodes may also be a double-sided electrode including a second current collector sheet and a second active material layer attached to both surfaces thereof. On the other hand, the second electrodes arranged on the outermost sides may be single-sided electrodes including a second current collector sheet and a second active material layer attached to one surface thereof.

Hereinafter, embodiments of the present invention will be described in more detail. However, the following embodiments do not limit the scope of the invention.

Next, a thin battery according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view in which a part of an outer package of a thin battery is cut out, and FIG. 2 is a longitudinal sectional view showing a main part of the thin battery. 2 corresponds to a cross-sectional view taken along the line II-II of the thin battery shown in FIG.

The thin battery 100 includes an electrode group 103, a non-aqueous electrolyte (not shown), and an exterior body 108 that houses them. The electrode group 103 includes one first electrode 110 and a pair of second electrodes 120 that sandwich the first electrode 110, and a separator 107 is interposed between the first electrode 110 and the second electrode 120. Yes. The first electrode 110 includes a first current collector sheet 111 and a first active material layer 112 attached to both surfaces. The second electrode 120 includes a second current collector sheet 121 and a second active material layer 122 attached to one surface thereof.

The first current collector sheet 111 has a first tab 114 extending in the first direction from one side thereof. A first lead 113 is connected to the first tab 114. The first lead 113 is sandwiched by the sealing allowance 108S of the exterior body 108 via the sealing material 130, and is drawn out of the exterior body 108 in the first direction.

Similarly, the second current collector sheet 121 has a second tab 124 extending from one side thereof in the first direction. The second tabs 124 of the pair of second current collector sheets 121 are overlapped with each other and electrically connected by, for example, welding. Thereby, the collective tab 124A is formed. A second lead 123 is connected to the assembly tab 124A. The second lead 123 is sandwiched between the sealing margins 108S of the exterior body 108 via the sealing material 130, and is drawn out of the exterior body 108 in the first direction. End portions of the first lead 113 and the second lead 123 led out of the exterior body 108 function as a first external terminal or a second external terminal, respectively.

The exterior body 108 includes a first portion 108A that faces the first active material layer 112 and the second active material layer 122, and a region of the first current collector sheet 111 that does not include the first active material layer 112 (particularly, the first active material layer 112). Tab) and a region of the second current collector sheet 121 that does not have the second active material layer 122 (particularly, the second tab) and the second portion 108B that faces the region.

Between the sealing margin 108S and the end portion (hereinafter referred to as the active material layer end portion) 103T on the sealing margin side of the first active material layer and the second active material layer (hereinafter referred to as the end portion of the active material layer) 103T shown by a broken line in FIG. A spacer 109 is arranged. A first gap G1 is formed between the sealing margin 108S and the spacer 109, and a second gap G2 is formed between the spacer 109 and the active material layer end portion 103T.

The length of the spacer 109 is about 95 to 105% of the length (width) of the end portion 103T on the sealing margin side of the first active material layer and the second active material layer having substantially the same width. The width of the spacer is about 1.0 to 5.0 mm. In the illustrated example, a pair of spacer sheets 109 are abutted and bonded together with the first tab 114 and the second tab 124 sandwiched therebetween. The thickness of one spacer sheet 109 is, for example, about 20 to 500 μm or 50 to 300 μm.

The sealing material 130 interposed between the exterior body 108 and each lead is used to enhance the sealing performance of the sealing allowance after joining. For the sealing material 130, a thermoplastic resin having a heat welding property can be used. As a thermoplastic resin, the material illustrated as a material of a spacer, for example is mentioned, Polyolefin resin is preferable.

In FIG. 1, the electrode group 103 is generally rectangular, but the shape of the electrode group 103 is not limited to this. The shape of the electrode excluding the tab may be a shape having a straight portion from which the tab protrudes, and is rectangular (including a square), trapezoid, parallelogram, substantially elliptical shape having a straight portion in part, at least one round Examples include a substantially rectangular shape having a corner, a substantially trapezoidal shape, and a substantially parallelogram shape. From the viewpoint of productivity, a rectangular shape or a substantially rectangular shape is preferable. When the electrode group is rectangular or substantially rectangular, the shape of the thin battery is also rectangular or substantially rectangular, and the ratio of the length of the long side L1 to the short side L2 is, for example, long side: short side = 1: 1 to 8: 1. Usually, the direction along the long side is the first direction in which the tab extends.

The shape of the tab is not particularly limited. The shape of the tab is, for example, a rectangle (including a square), a trapezoid, a parallelogram, a semicircle, a semi-ellipse, a rectangle with an arc at the tip, a substantially rectangle having at least one round corner, a substantially trapezoid, and a substantially parallelogram. Such as shape.

As shown in FIG. 2, the exterior body 108 includes a first part 108 </ b> A that faces the first active material layer 112 and the second active material layer 122, and the first active material layer 112 of the first current collector sheet 111. A second region 108B that opposes the region (particularly the first tab) that does not include the region (particularly the second tab) that does not include the second active material layer 122 of the second current collector sheet 121. The second portion 108B covers a linear spacer 109 provided so as to intersect perpendicularly with the first direction. The second portion 108 </ b> B of the exterior body 108 partially enters the first gap G <b> 1 and the second gap G <b> 2 and is curved along the shape of the spacer 109.

The minimum thickness T1 of the portion where the spacer 109 is arranged and the minimum thickness T2 at the sealing allowance 108S are measured from the cross section taken along the line II′-II ′ of FIG. The minimum thickness T1 generally corresponds to the total thickness when two exterior bodies 108 and two spacers 109 are overlapped, and the minimum thickness T2 approximately corresponds to the total thickness when two exterior bodies 108 are overlapped. To do. At this time, 1.1 <T1 / T2 <6.0 is satisfied, and T1 and the thickness T3 of the portion where the first active material layer and the second active material layer are arranged are 0.5 <T1 / T3 < Designed to meet 1.5. The width G of the second gap and the length L in the first direction of the first active material layer and the second active material layer are designed to satisfy 0.01 <G / L <0.2.

Next, the role of the linear spacer 109 will be further described with reference to FIG. In FIG. 3, it is assumed that the thin battery 100 is bent along a curved arrow. As conceptually shown by the arrows in FIG. 3, when the sheet-like thin battery 100 is bent, one outer surface of the thin battery has a convex shape and the other outer surface has a concave shape. At this time, on the outer surface having a convex shape, in the vicinity of the active material layer end portion 103T of the electrode group 103, the second portion 108B of the exterior body 108 that is curved along the shape of the spacer 109 has the first gap G1 and It is pulled out from the second gap G2 and developed. Therefore, excessive stress is not applied to the exterior body, and cracks are less likely to occur in the exterior body 108 at the stepped portion of the electrode group 103. On the other hand, on the outer surface having a concave shape, the second portion 108B that has previously entered the first gap G1 and the second gap G2 enters deeper into the inside of the first gap and the second gap. Is suppressed.

Similarly, the first gap G1 and the second gap G2 have the effect of suppressing the stress applied to the exterior body 108 and the convex bulge. However, from the viewpoint of enhancing the effect of suppressing defects at the stepped portion where the thickness of the electrode group changes (particularly, near the end portions on the sealing margin side of the first active material layer and the second active material layer), the spacer 109 It is important to intentionally form the second gap G2.

The step of accommodating the electrode group 103 in the outer package 108 in a state where the ends of the first lead 113 and the second lead 123 are led out from the opening of the outer package 108 and impregnating the electrode group 103 with a nonaqueous electrolyte under reduced pressure. Done. If the sealing material 130 is interposed between the opening end portion (sealing allowance 108S) of the exterior body 108 and each lead, the sealing material 130 is heated under reduced pressure, and the opening of the exterior body 108 is sealed. A thin battery is obtained.

Next, the electrodes, leads, separators, non-aqueous electrolyte, exterior body, etc. constituting the electrode group will be described.

(Negative electrode)
The negative electrode has a negative electrode current collector sheet as the first or second current collector sheet and a negative electrode active material layer as the first or second active material layer. A metal film, metal foil, etc. are used for a negative electrode collector sheet. The material of the negative electrode current collector sheet is preferably at least one selected from the group consisting of copper, nickel, titanium and alloys thereof, and stainless steel. The thickness of the negative electrode current collector sheet is preferably 5 to 30 μm, for example.

The negative electrode active material layer includes a negative electrode active material, and optionally includes a binder and a conductive agent. The negative electrode active material layer may be a deposited film formed by a vapor phase method (for example, vapor deposition). Examples of the negative electrode active material include Li metal, a metal or alloy that electrochemically reacts with Li, a carbon material (for example, graphite), a silicon alloy, and a silicon oxide. The thickness of the negative electrode active material layer is preferably, for example, 1 to 300 μm.

(Positive electrode)
The positive electrode has a positive electrode current collector sheet as a first or second current collector sheet and a positive electrode active material layer as a first or second active material layer. A metal film, a metal foil, or the like is used for the positive electrode current collector sheet. The material of the positive electrode current collector sheet is preferably at least one selected from the group consisting of, for example, silver, nickel, palladium, gold, platinum, aluminum, alloys thereof, and stainless steel. The thickness of the positive electrode current collector sheet is preferably 1 to 30 μm, for example.

The positive electrode active material layer includes a positive electrode active material and a binder, and includes a conductive agent as necessary. The positive electrode active material is not particularly limited. When the thin battery is a secondary battery, a lithium-containing composite oxide such as LiCoO ₂ or LiNiO ₂ is used. When the thin battery is a primary battery, manganese dioxide is used. Carbon fluoride (fluorinated graphite), lithium-containing composite oxide, and the like can be used. The thickness of the positive electrode active material layer is preferably 1 to 300 μm, for example.

As the conductive agent contained in the active material layer, graphite, carbon black, or the like is used. The amount of the conductive agent is, for example, 0 to 20 parts by mass per 100 parts by mass of the active material. As the binder to be included in the active material layer, fluorine resin, acrylic resin, rubber particles, or the like is used. The amount of the binder is, for example, 0.5 to 15 parts by mass per 100 parts by mass of the active material.

(Separator)
As the separator, a resin microporous film or a nonwoven fabric is preferably used. As the material (resin) for the separator, polyolefin (polyethylene, polypropylene, etc.), polyamide, polyamideimide, etc. are preferable. The thickness of the separator is, for example, 8 to 30 μm.

(Lead)
The negative electrode lead and the positive electrode lead are connected to the negative electrode current collector sheet or the positive electrode current collector sheet, respectively, by welding or the like. As the negative electrode lead, a copper lead, a copper alloy lead, a nickel lead, a nickel-plated copper lead, or the like is preferably used. As the positive electrode lead, a nickel lead, an aluminum lead or the like is preferably used.

(Nonaqueous electrolyte)
When the thin battery is a lithium ion battery, the nonaqueous electrolyte is preferably a mixture of a lithium salt and a nonaqueous solvent that dissolves the lithium salt. Examples of the lithium salt include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , and imide salts. Non-aqueous solvents include propylene carbonate, ethylene carbonate, butylene carbonate and other cyclic carbonate esters, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate and other chain carbonate esters, γ-butyrolactone, γ-valerolactone and other cyclic carboxylic acid esters. Etc.

It is preferable that at least a part of the nonaqueous electrolyte impregnated in the electrode group forms a gel electrolyte. The gel electrolyte is preferably present at least in the interface region between each active material layer and each separator. The presence of the gel electrolyte in the interface region between the active material layer and the separator improves the adhesion between the electrode and the separator. The gel electrolyte is preferably also present in the voids of each active material layer and / or in the pores of each separator.

The gel electrolyte includes, for example, a non-aqueous electrolyte and a resin that swells with the non-aqueous electrolyte. As the resin that swells with the nonaqueous electrolyte, a fluororesin containing a vinylidene fluoride unit is preferable. A fluororesin containing a vinylidene fluoride unit tends to retain a nonaqueous electrolyte and easily gels.

Examples of the fluororesin containing a vinylidene fluoride unit include polyvinylidene fluoride (PVdF), a copolymer (PVdF-HFP) containing a vinylidene fluoride (VdF) unit and a hexafluoropropylene (HFP) unit, and vinylidene fluoride (VdF). ) Units and trifluoroethylene (TFE) units. The amount of the vinylidene fluoride unit contained in the fluororesin containing the vinylidene fluoride unit is preferably 1 mol% or more so that the fluororesin can easily swell with the nonaqueous electrolyte.

When the gel electrolyte is disposed in the interface region between the active material layer and the separator, for example, a resin that swells with a nonaqueous electrolyte is applied to the surface of the active material layer and / or the surface of the separator, for example, in a thin film shape. Thereafter, the active material layer and the separator are laminated via a resin coating, and the obtained laminate or electrode group is impregnated with a nonaqueous electrolyte. As a result, the resin swells with the non-aqueous electrolyte, and a gel electrolyte is formed in the interface region. When a fluororesin containing a vinylidene fluoride unit is used for the gel electrolyte, the amount of the resin contained in the coating film is per unit surface area of the interface region between the active material layer and the separator (that is, per unit surface area of the active material layer or separator). 1 to 30 g / m ² is preferable.

The exterior body is formed of, for example, a laminate film material including a barrier layer against water vapor and resin layers formed on both sides thereof. The material used for the barrier layer is not particularly limited, but it is preferable to use a metal layer, a ceramic layer, or the like. For example, metal materials such as aluminum, titanium, nickel, iron, platinum, gold, silver, and tin, and ceramic materials such as silicon oxide, magnesium oxide, and aluminum oxide are preferable. The thickness of the barrier layer is preferably 0.01 to 50 μm, for example. The resin layer material disposed on the inner surface side of the outer package is made of polyolefin such as polyethylene and polypropylene, polyethylene terephthalate, polyamide, polyurethane, and polyethylene-acetic acid from the viewpoint of ease of thermal welding, electrolyte resistance, and chemical resistance. A vinyl copolymer (EVA) or the like is preferable. The thickness of the resin layer on the inner surface side is preferably 10 to 100 μm. The resin layer disposed on the outer surface side of the exterior body is made of polyamide such as 6,6-nylon, polyolefin, polyethylene terephthalate, polyester such as polybutylene terephthalate, etc. from the viewpoint of strength, impact resistance and chemical resistance. preferable. The thickness of the resin layer on the outer surface side is preferably 5 to 100 μm.

Next, the present invention will be described based on examples, but the following examples do not limit the scope of the invention.

Example 1
In the following procedure, a thin battery having a pair of negative electrodes and a positive electrode sandwiched between them was produced.

(1) Production of negative electrode An electrolytic copper foil having a thickness of 8 μm was prepared as a negative electrode current collector sheet. The negative electrode mixture slurry was applied to one surface of the electrolytic copper foil, dried and rolled to form a negative electrode active material layer, thereby obtaining a negative electrode sheet. The negative electrode mixture slurry was prepared by mixing 100 parts by mass of graphite as a negative electrode active material, 8 parts by mass of polyvinylidene fluoride (PVdF) as a binder, and an appropriate amount of N-methyl-2-pyrrolidone (NMP). Prepared. The thickness of the negative electrode active material layer was 54 μm. A negative electrode having a size of 47.5 mm × 18 mm having a negative electrode tab of 5 mm × 5 mm was cut out from the negative electrode sheet, and the active material layer was peeled off from the negative electrode tab to expose the copper foil. Thereafter, a copper negative electrode lead was ultrasonically welded to the tip of the negative electrode tab.

(2) Production of positive electrode An aluminum foil having a thickness of 15 μm was prepared as a positive electrode current collector sheet. The positive electrode mixture slurry was applied to both surfaces of the aluminum foil, dried and then rolled to form a positive electrode active material layer to obtain a positive electrode sheet. The positive electrode mixture slurry is a mixture of 100 parts by mass of lithium cobalt oxide as a positive electrode active material, 1.2 parts by mass of acetylene black as a conductive agent, 1.2 parts by mass of PVdF as a binder, and an appropriate amount of NMP. Prepared. The thickness (per side) of the positive electrode active material layer was 38 μm. A 45 mm × 16 mm positive electrode having a 6 mm × 5 mm tab was cut out from the positive electrode sheet, and the active material layer was peeled off from the positive electrode tab to expose the aluminum foil. Thereafter, an aluminum positive electrode lead was ultrasonically welded to the tip portion of the positive electrode tab.

(3) Nonaqueous electrolyte The nonaqueous electrolyte was prepared by dissolving LiPF ₆ in a mixed solvent containing ethylene carbonate (EC) and diethyl carbonate (DEC) as main components.

(4) Line-shaped spacer A pair of strip-shaped spacer sheets having a length of 17 mm and a width of 2 mm was cut out from a polypropylene sheet (thickness: 100 μm) which is a thermoplastic resin having a heat-welding property.

(5) Assembly of thin battery 5 parts by weight of PVdF was dissolved in 100 parts by weight of the mixed solvent to prepare a polymer solution. The obtained polymer solution was applied to both sides of a separator composed of a 49 mm × 18 mm microporous polyethylene film (thickness 9 μm), and then the solvent was stripped to form a PVdF film. The amount of PVdF applied was 15 g / m ² . Thereafter, the positive electrode was disposed between the pair of negative electrodes via a separator so that the negative electrode active material layer and the positive electrode active material layer faced each other, thereby forming an electrode group. At this time, both the positive electrode tab and the negative electrode tab were projected from the same side of the electrode group. Next, the first tab and the second tab were sandwiched by a pair of spacer sheets, and the spacer sheets were bonded together by welding and also welded to each tab.

(6) Production of exterior body and battery assembly As a material for the exterior body, a laminate film material (thickness: 75 μm) having a barrier layer of aluminum foil, an inner layer of polypropylene and an outer layer of nylon is used. Formed body. First, the laminate film material was cut into a rectangle of 29 mm × 120 mm and folded in half at the center in the longitudinal direction.

Next, the electrode group 103 was sandwiched between two folded laminate film materials, and each lead of the electrode group 103 was led out from the opposite side of the fold. Next, the joining margin of the two sides crossing the crease was welded, and the envelope-shaped exterior body 108 in a state where the electrode group 103 was accommodated was formed. Next, each lead portion that overlaps the sealing margin (opening end) of the envelope-shaped outer package 108 is surrounded by a sealing material (thermoplastic resin) 130, and then a non-aqueous electrolyte is injected from the opening to obtain −740 mmHg. The sealing margin was thermally welded under reduced pressure. Thereafter, the thin battery was aged in an environment of 45 ° C., and the entire electrode group was impregnated with a nonaqueous electrolyte. Finally, the battery was pressed at 25 ° C. at a pressure of 0.25 MPa for 30 seconds to produce a battery A having a thickness of 0.45 mm.

The ratio of the thickness T1 (0.35 mm) of the part where the linear spacer of the battery A is arranged to the minimum thickness T2 (0.14 mm) in the sealing margin: T1 / T2 is 2.5. It was. Further, the ratio of T1 to the thickness T3 (0.45 mm) of the portion where the first active material layer and the second active material layer of the battery A are disposed: T1 / T3 was 0.78. Further, the width G of the second gap G2 was 2.5 mm.

[Evaluation]
(Initial battery capacity)
Under the environment of 25 ° C., the battery A was charged and discharged as follows to determine the initial capacity (C ₀ ). However, the design capacity of the battery A is 1 C (mAh).

(1) Constant current charging: 0.2 CmA (end voltage 4.35 V)
(2) Constant voltage charging: 4.35 V (end current 0.05 CmA)
(3) Constant current discharge: 0.2 CmA (end voltage 3.0 V)
(Capacity maintenance rate after bending test)
A pair of expandable and contractible fixing members were horizontally arranged opposite to each other, and a battery A in a discharged state was attached to each fixed member and fixed. Then, in an environment of 25 ° C., the distance between both ends of the fixing member was shortened so that the curvature radius of the battery became R30 mm, and then both ends of the fixing member were returned to the original state to return the battery to a flat state. After repeating this operation 1000 times, the front and back of the battery were exchanged, and bending was performed 1000 times on the opposite surface of the battery.

Thereafter, the thin battery was charged and discharged under the same conditions as described above, and the discharge capacity (C _x ) after the bending test was obtained. From the obtained discharge capacity C _x and initial capacity C ₀ , the capacity retention rate was obtained from the following equation.

Capacity retention ratio after bending test (%) = (C _x / C ₀ ) × 100
Ten batteries A were produced, and the same test was performed on each of them to determine the average value of the capacity retention rate. The results are shown in Table 1. In addition, the number of defective batteries in which cracks in the outer package or convex bulges (外装) occurred in the stepped portion where the thickness of the electrode group changed was visually confirmed.

<< Comparative Example 1 >>
Ten batteries B were produced and evaluated in the same manner as in Example 1 except that the line spacer was not attached to the positive electrode tab and the negative electrode tab of the electrode group. The results are shown in Table 1.

As shown in Table 1, in Example 1, a high capacity retention rate was obtained and no defective battery was generated, whereas in Comparative Example 1, 8 defective batteries were generated, and the capacity maintenance rate was also lowered. did.

The thin battery of the present invention is suitable for use in a small electronic device such as a biological sticking device or a wearable portable terminal.

DESCRIPTION OF SYMBOLS 100 Thin battery 103 Electrode group 103T Active material layer edge part 107 Separator 108 Exterior body 108S Sealing allowance 108A 1st site | part 108B 2nd site | part 109 Line-shaped spacer 110 1st electrode 111 1st collector sheet 112 1st active material layer 113 1st lead 114 1st tab 120 2nd electrode 121 2nd collector sheet 122 2nd active material layer 123 2nd lead 124 2nd tab 124A Collecting tab 130 Sealing material

Claims

A sheet-like electrode group, a non-aqueous electrolyte impregnated in the electrode group, and an exterior body that hermetically stores the electrode group and the non-aqueous electrolyte,
The electrode group includes:
A sheet-like first electrode;
A sheet-like second electrode;
A separator disposed between the first electrode and the second electrode;
Comprising
The first electrode includes a first current collector sheet and a first active material layer attached to a surface of the first current collector sheet;
The second electrode includes a second current collector sheet and a second active material layer attached to a surface of the second current collector sheet,
The first current collector sheet includes a first tab extending in a first direction from a part of one side of the first current collector sheet, and is drawn to the outside of the exterior body by the first tab. The lead is connected,
The second current collector sheet includes a second tab extending in a first direction from a part of one side of the second current collector sheet, and the second current collector sheet is pulled out of the exterior body by the second tab. 2 leads are connected,
The exterior body has a sealing margin for sandwiching the first lead and the second lead,
A linear spacer is disposed between the sealing margin and the end portion on the sealing margin side of the first active material layer and the second active material layer,
A first gap is formed between the sealing margin and the spacer;
A thin battery in which a second gap is formed between the spacer and an end portion on the sealing margin side of the first active material layer and the second active material layer.
The thin battery according to claim 1, wherein the thickness T1 of the portion where the spacer is disposed and the thickness T2 of the portion having the sealing allowance satisfy T1> T2.
The thin battery according to claim 2, satisfying 1.1 <T1 / T2 <6.0.
The thickness T1 of the portion where the spacer is disposed and the thickness T3 of the portion where the first active material layer and the second active material layer are disposed are 0.5 <T1 / T3 <1. The thin battery according to any one of claims 1 to 3, which satisfies 5.
The width G of the second gap and the length L in the first direction of the first active material layer and the second active material layer satisfy 0.01 <G / L <0.2. 5. The thin battery according to any one of 1 to 4.
6. The thin battery according to claim 1, wherein the spacer is a pair of sheet members that sandwich the first tab and the second tab.
The thin sheet battery according to claim 6, wherein the sheet member includes a polyolefin resin.
The thin battery according to claim 7, wherein the sheet member includes a core material that does not melt at a melting point of the polyolefin resin.
The thin battery according to any one of claims 1 to 8, wherein the thickness is 3 mm or less.