Battery

Abstract

To provide a battery which can reduce contact failure.SOLUTION: A battery 100 comprises: a power generation element 10 having a positive electrode 1 to which a positive electrode terminal 4 is connected, a negative electrode 2 to which a negative electrode terminal 5 is connected, and a separator 3 sandwiched between the positive electrode 1 and the negative electrode 2; an insulator 20 which penetrates the power generation element 10 in a first direction z; and a first outer packaging 31 and a second outer packaging 32 which sandwich the power generation element 10 in the first direction z. A natural length of the insulator 20 in the first direction z is longer than a distance D between the first outer packaging 31 and the second outer packaging 32 in the first direction z. The insulator 20 has elastic force of 1 N or higher.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a battery. [Background technology]

[0002] Batteries are widely used as a power source for mobile devices such as cell phones and laptops, as well as for hybrid cars and other vehicles.

[0003] Coin-type or button-type batteries (for example, Patent Document 1) are used in various devices such as watches and earphones. Patent Document 1 describes a coin-type battery in which the roll core is positioned at the center of the wound body. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 5767115 [Overview of the project] [Problems that the invention aims to solve]

[0005] Coin-type or button-type batteries achieve electrical connection to the outside world through the outer casing, as the positive and negative terminals are in close contact with the casing. If the contact between the positive or negative terminal and the casing is insufficient, poor contact may occur due to dropping or vibration.

[0006] This disclosure is made in view of the above-mentioned problems and aims to provide a battery that can reduce contact failures caused by dropping or vibration. [Means for solving the problem]

[0007] To solve the above problems, the following means are provided.

[0008] (1) The battery according to the first embodiment comprises a power generation element having a positive electrode to which a positive electrode terminal is connected, a negative electrode to which a negative electrode terminal is connected, and a separator sandwiched between the positive electrode and the negative electrode; an insulator penetrating the power generation element in a first direction; and a first outer casing and a second outer casing sandwiching the power generation element in the first direction. The natural length of the insulator in the first direction is longer than the distance between the first outer casing and the second outer casing in the first direction, and the elastic force of the insulator is 1N or more.

[0009] (2) In the battery according to the above embodiment, the outer shape of the insulator may be circular at the cross-section obtained by cutting the insulator with a plane that passes through the center of the insulator in the first direction and is perpendicular to the first direction.

[0010] (3) In the battery according to the above embodiment, the first end of the insulator may be deformable in response to a load in the first direction.

[0011] (4) In the cross-section obtained by cutting the insulator of the battery according to the above embodiment with a plane passing through the center of the first direction and perpendicular to the first direction, the cross-sectional shape of the first end of the insulator may be different from the cross-sectional shape at the center of the first direction.

[0012] (5) In the battery according to the above embodiment, the circumference of the first end of the insulator may be longer than the circumference of the insulator at the center in the first direction.

[0013] (6) In the battery according to the above embodiment, the first end of the insulator may have a space inside that extends in the first direction.

[0014] (7) In the battery according to the above embodiment, the insulator may have grooves on its side surface that extend in the first direction.

[0015] (8) In the battery according to the above embodiment, the first end of the insulator may have a different shape from the second end on the opposite side of the first end. [Effects of the Invention]

[0016] The battery according to the above aspect can reduce contact failure due to dropping or vibration.

Brief Description of the Drawings

[0017] [Figure 1] It is a cross-sectional view of the battery according to the first embodiment. [Figure 2] It is a developed view of the power generation element of the battery according to the first embodiment. [Figure 3] It is a cross-sectional view of the insulator of the battery according to the first embodiment. [Figure 4] It is another cross-sectional view of the insulator of the battery according to the first embodiment. [Figure 5] It is another cross-sectional view of the insulator of the battery according to the first embodiment. [Figure 6] It is a cross-sectional view of the insulator of the battery according to the first modification. [Figure 7] It is a cross-sectional view of the insulator of the battery according to the second modification. [Figure 8] It is a cross-sectional view of the insulator of the battery according to the third modification. [Figure 9] It is another cross-sectional view of the insulator of the battery according to the third modification. [Figure 10] It is a cross-sectional view of the insulator of the battery according to the fourth modification. [Figure 11] It is a cross-sectional view of the insulator of the battery according to the fifth modification. [Figure 12] It is another cross-sectional view of the insulator of the battery according to the fifth modification. [Figure 13] It is another cross-sectional view of the insulator of the battery according to the fifth modification.

Modes for Carrying Out the Invention

[0018] The embodiments will be described in detail below, with reference to the figures as appropriate. The drawings used in the following description may be enlarged for convenience to clearly illustrate the features, and the dimensional ratios of each component may differ from those in reality. The materials, dimensions, etc., exemplified in the following description are examples only, and the present invention is not limited to them. It can be implemented with appropriate modifications without changing the essence of the invention.

[0019] First, let's define the directions. The direction in which the insulator penetrates the power generation element is defined as the z-direction. The z-direction is, for example, the direction perpendicular to the bottom surface of the battery. Any direction perpendicular to the z-direction is defined as the x-direction, and the direction perpendicular to both the x-direction and the z-direction is defined as the y-direction. The z-direction is just one example of the first direction. The +z direction is sometimes expressed as "up," and the -z direction as "down." Up and down do not necessarily coincide with the direction in which gravity acts.

[0020] "First Embodiment" Figure 1 is a cross-sectional view of a battery according to the first embodiment. Figure 1 shows a cross-section obtained by cutting along a line segment passing through the centers of the top and bottom surfaces of the battery 100. The battery 100 comprises a power generation element 10, an insulator 20, and an outer casing 30. The shape of the battery 100 is, for example, coin-type or button-type. The type of battery 100 is not limited, but examples include lithium-ion secondary batteries, magnesium-ion secondary batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and all-solid-state batteries.

[0021] (Power generation element) The power generation element 10 comprises a positive electrode 1, a negative electrode 2, and a separator 3. A positive electrode terminal 4 is connected to the positive electrode 1, and a negative electrode terminal 5 is connected to the negative electrode 2. The positive electrode 1, the negative electrode 2, and the separator 3 may be covered at least partially with insulating tape 6 or the like. The insulating tape 6 is, for example, polyimide tape.

[0022] Figure 2 is an unfolded view of the power generation element 10. The power generation element 10 is, for example, a wound body. The wound body is made by winding a unit consisting of a positive electrode 1, a separator 3, a negative electrode 2, and a separator 3. For example, in Figure 2, the power generation element 10 is obtained by stacking the positive electrode 1, separator 3, negative electrode 2, and separator 3 in this order and winding them with the left end as the winding center.

[0023] The lengths L1 of the positive electrode 1, L2 of the negative electrode 2, and L3 of the separator 3 may be different. Lengths L1, L2, and L3 are the widths of the unfolded body and the heights in the z direction of the power generation element 10. The length L3 of the separator 3 is often longer than the length L1 of the positive electrode 1 and the length L2 of the negative electrode 2 in order to prevent short circuits. The length L2 of the negative electrode 2 is often longer than the length L1 of the positive electrode 1. If the power generation element 10 is a wound body, the height of the power generation element 10 in the z direction is approximately equal to the length L2 of the negative electrode 2. The separator 3 often wrinkles or shrinks, and even if the length L3 of the separator 3 is greater than the length L2 of the negative electrode 2, it is difficult to specify the length L3 of the separator 3 in the wound state.

[0024] <Positive electrode> The positive electrode 1 includes, for example, a positive electrode current collector 1A and a positive electrode active material layer 1B. The positive electrode active material layer 1B is located on at least one surface of the positive electrode current collector 1A. The positive electrode active material layer 1B is formed on both sides of the positive electrode current collector 1A, for example.

[0025] [Positive electrode current collector] The positive electrode current collector 1A is, for example, a conductive plate material. The positive electrode current collector 1A is, for example, a thin metal sheet such as aluminum, copper, nickel, titanium, or stainless steel. Lightweight aluminum is suitably used for the positive electrode current collector 1A. The average thickness of the positive electrode current collector 1A is, for example, 10 μm or more and 30 μm or less.

[0026] A positive electrode terminal 4 is connected to the positive electrode current collector 1A. The positive electrode terminal 4 is connected, for example, to one end of the positive electrode current collector 1A. The positive electrode terminal 4 includes, for example, a conductive material such as aluminum, nickel, or copper. The positive electrode terminal 4 is connected to the positive electrode current collector 1A by, for example, welding, screwing, etc. To prevent short circuits, the surface of the positive electrode terminal 4 may be protected with insulating tape. The positive electrode terminal 4 extends, for example, on the first surface in the z direction of the power generation element 10. A portion of the positive electrode terminal 4 is sandwiched between the insulator 20 and the first outer casing 31.

[0027] [Cathode active material layer] The positive electrode active material layer 1B includes, for example, a positive electrode active material. The positive electrode active material layer 1B may also include a conductive additive and a binder, if necessary.

[0028] The positive electrode active material includes an electrode active material capable of reversibly carrying out cation intercalation, cation desorption and insertion, or cation and counteranion doping and dedoping. The cations are, for example, lithium ions and magnesium ions.

[0029] The positive electrode active material can be any known material. The positive electrode active material is, for example, a composite metal oxide. Examples of composite metal oxides include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2), lithium manganese spinel (LiMn2O4), and LiNi x Co y Mn z M a O2 compounds (wherein the general formula x+y+z+a=1, 0≦x<1, 0≦y<1, 0≦z<1, 0≦a<1, and M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, Cr), lithium vanadium compounds (LiV2O5), olivine-type LiMPO4 (wherein M is one or more elements selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr, or VO), lithium titanate (Li4Ti5O 12 ), LiLi x Co y Al zO2 (0.9 < x + y + z < 1.1). The positive electrode active material may be an organic substance. For example, the positive electrode active material may be polyacetylene, polyaniline, polypyrrole, polythiophene, or polyacene.

[0030] The positive electrode active material may be a cation-free material. Examples of the cation-free material include FeF3, a conjugated polymer containing an organic conductive substance, a Chevrel phase compound, a transition metal chalcogenide, a vanadium oxide, a niobium oxide, etc. The cation-free material may be used alone or in combination of a plurality of materials. When the positive electrode active material is a cation-free material, for example, discharging is first performed. Cations are inserted into the positive electrode active material by discharging. In addition, the positive electrode active material may be chemically or electrochemically pre-doped with cations with respect to the cation-free material.

[0031] The conductive assistant enhances the electron conductivity between the positive electrode active materials. Examples of the conductive assistant include carbon powder, carbon nanotubes, carbon materials, metal fine powder, a mixture of carbon materials and metal fine powder, and conductive oxides. Examples of the carbon powder include carbon black, acetylene black, ketjen black, etc. Examples of the metal fine powder include powders of copper, nickel, stainless steel, iron, etc.

[0032] The binder in the positive electrode active material layer 1B binds the positive electrode active materials together. A known binder can be used. The binder is preferably one that does not dissolve in the electrolyte solution, has oxidation resistance, and has adhesiveness. Examples of the binder include fluororesins. Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyamideimide (PAI), polybenzimidazole (PBI), polyethersulfone (PES), polyacrylic acid and its copolymers, metal ion cross-linked products of polyacrylic acid and its copolymers, polypropylene (PP) or polyethylene (PE) grafted with maleic anhydride, and mixtures thereof. PVDF is particularly preferred as the binder used in the positive electrode active material layer 1B.

[0033] <Negative electrode> The negative electrode 2 includes, for example, a negative electrode current collector 2A and a negative electrode active material layer 2B. The negative electrode active material layer 2B is located on at least one surface of the negative electrode current collector 2A. The negative electrode active material layer 2B is formed on both sides of the negative electrode current collector 2A, for example.

[0034] [Negative electrode current collector] The negative electrode current collector 2A is, for example, a conductive plate material. The negative electrode current collector 2A can be the same as the positive electrode current collector 1A.

[0035] A negative electrode terminal 5 is connected to the negative electrode current collector 2A. The negative electrode terminal 5 is connected, for example, to one end of the negative electrode current collector 2A. The negative electrode terminal 5 includes, for example, a conductive material such as aluminum, nickel, or copper. The negative electrode terminal 5 is connected to the negative electrode current collector 2A by, for example, welding, screwing, etc. To prevent short circuits, the surface of the negative electrode terminal 5 may be protected with insulating tape. The negative electrode terminal 5 extends, for example, onto a second surface in the z direction of the power generation element 10. The second surface is the surface opposite to the surface on which the positive electrode terminal 4 is exposed. A portion of the negative electrode terminal 5 is sandwiched between the insulator 20 and the second outer casing 32.

[0036] [Negative electrode active material layer] The negative electrode active material layer 2B includes, for example, a negative electrode active material. The negative electrode active material layer 2B may also include a conductive additive and a binder, if necessary.

[0037] The negative electrode active material can be any compound capable of intercalating and releasing ions, and known negative electrode active materials can be used. Examples of negative electrode active materials include metallic lithium, metallic magnesium, lithium alloys, magnesium alloys, carbon materials, and materials that can alloy with cations. Examples of carbon materials include graphite (natural graphite, artificial graphite) capable of intercalating and releasing ions, carbon nanotubes, non-graphitizable carbon, easily graphitizable carbon, and low-temperature calcined carbon. Examples of materials that can alloy with cations include silicon, tin, zinc, lead, and antimony. These materials can be individual metals, alloys, or oxides containing these elements.

[0038] The conductive additive and binder can be the same as those used for positive electrode 1. In addition to those listed for positive electrode 1, the binder for negative electrode 2 may be, for example, cellulose, styrene-butadiene rubber, ethylene-propylene rubber, polyimide resin, polyamide-imide resin, acrylic resin, etc. Cellulose may be, for example, carboxymethylcellulose (CMC).

[0039] <Separator> The separator 3 is sandwiched between the positive electrode 1 and the negative electrode 2. The separator 3 isolates the positive electrode 1 and the negative electrode 2, preventing a short circuit between them. The separator 3 spreads in plane along the positive electrode 1 and the negative electrode 2. The cations can pass through the separator 3.

[0040] The separator 3 is, for example, a porous film having an electrically insulating porous structure. The separator 3 is, for example, a single layer or laminate of a polyolefin film. The separator 3 may also be a stretched film of a mixture of polyethylene or polypropylene. The separator 3 may also be a fibrous nonwoven fabric made of at least one constituent material selected from the group consisting of cellulose, polyester, polyacrylonitrile, polyamide, polyethylene, and polypropylene. The separator 3 may also be, for example, a solid electrolyte. The solid electrolyte is, for example, a polymer solid electrolyte, an oxide-based solid electrolyte, or a sulfide-based solid electrolyte.

[0041] Separator 3 may also be an inorganic coated separator. An inorganic coated separator is obtained by coating the surface of the above-mentioned film with a mixture of resin such as PVDF or CMC and inorganic materials such as alumina or silica. Inorganic coated separators have excellent heat resistance and suppress the deposition of transition metals leached from the positive electrode onto the negative electrode surface.

[0042] <Electrolyte> The electrolyte is impregnated into the power generation element 10. The electrolyte is impregnated into the positive electrode active material layer 1B and the negative electrode active material layer 2B.

[0043] The electrolyte varies depending on the type of battery, but any known electrolyte can be used. If battery 100 is a solid-state battery, no electrolyte is required.

[0044] For example, in the case of a lithium-ion secondary battery, the electrolyte contains a non-aqueous solvent and an electrolyte salt.

[0045] In the case of lithium-ion secondary batteries, the electrolyte salt is, for example, a lithium salt. Examples of electrolyte salts include LiPF6, lithium borofluoride (LiBF4), LiClO4, LiCF3SO3, LiCF3CF2SO3, LiC(CF3SO2)3, LiN(SO2F)2, LiN(CF3SO2)2, LiN(CF3CF2SO2)2, LiN(CF3SO2)(C4F9SO2), LiN(CF3CF2CO)2, LiBOB, LiN(FSO2)2, etc.

[0046] The non-aqueous solvent may contain, for example, a cyclic carbonate and a linear carbonate. The cyclic carbonate solvates the electrolyte. Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, and butylene carbonate. It is preferable that the cyclic carbonate contains at least propylene carbonate. The linear carbonate reduces the viscosity of the cyclic carbonate. Examples of linear carbonates include diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. Other non-aqueous solvents may include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, etc.

[0047] (Insulator) The insulator 20 penetrates the power generation element 10 in the z direction. The insulator 20 is a columnar body. The insulator 20 is located at the axial center of the winding power generation element 10.

[0048] The natural length of the insulator 20 is longer than the distance D in the z direction between the first outer casing 31 and the second outer casing 32. The natural length of the insulator 20 is the length of the insulator 20 before it is housed in the outer casing 30. That is, the natural length of the insulator 20 is the length of the insulator 20 when no load is applied to it in the z direction. The distance D in the z direction between the first outer casing 31 and the second outer casing 32 is the length of the perpendicular line drawn from the inner surface 31A of the first outer casing 31 to the inner surface 32A of the second outer casing 32. The inner surface 31A is the inner surface of the first outer casing 31 that intersects with the z direction. The inner surface 32A is the inner surface of the second outer casing 32 that intersects with the z direction.

[0049] The z-length L20 of the insulator 20 is, for example, greater than or equal to the z-length L2 of the negative electrode 2. Preferably, the z-length L20 of the insulator 20 is longer than the z-length L2 of the negative electrode 2, and more preferably 1.04 times or more the z-length L2 of the negative electrode 2. The z-length L20 of the insulator 20 is, for example, greater than or equal to the z-length of the power generation element 10. The z-length L20 of the insulator 20 is the z-length of the insulator 20 when it is housed in the outer casing 30. Because a load is applied to the insulator 20 in the z direction within the outer casing 30, the z-length L20 of the insulator 20 is different from the natural length of the insulator 20.

[0050] The elastic force of the insulator 20 is 1 N or more. Preferably, the elastic force of the insulator 20 is 30 N or more. Elastic force is the force that an object that is deformed by an applied force exerts on another object as a reaction. The insulator 20 deforms in the z direction due to the load from the outer casing 30 and exerts an elastic force on the outer casing 30 as it tries to return to its original shape.

[0051] The elastic force of the insulator 20 can be determined, for example, by the following procedure. First, a cross-section of the battery 100 is photographed with X-rays, and the z-length L20 of the insulator 20 housed in the battery 100 is measured. Next, the battery 100 is disassembled, and the insulator 20 is removed. Then, the removed insulator 20 is placed on a load-displacement curve measuring instrument, and the load that the insulator 20 exerts on the instrument at length L20 is measured. This load is the force that the insulator 20 exerts on the instrument as it tries to return to its original shape, and corresponds to the elastic force.

[0052] The insulator 20 protrudes from the upper and lower surfaces of the power generation element 10 in the z direction. The upper end of the insulator 20 protrudes from the upper surface of the power generation element 10. The lower end of the insulator 20 protrudes from the lower surface of the power generation element 10. The upper end of the insulator 20 presses the positive terminal 4 against the first casing 31. The lower end of the insulator 20 presses the negative terminal 5 against the second casing 32.

[0053] Figures 3 to 5 are cross-sectional views of the insulator 20. Figures 3 to 5 show the insulator 20 before it is housed in the outer casing 30, and in a state where no load is applied to the insulator 20 in the z direction. Figure 3 is an xz cross-section of the insulator 20. Figure 4 is a cross-section taken along line AA in Figure 3. Figure 5 is a cross-section taken along line BB in Figure 3.

[0054] The insulator 20 comprises a first end 21, a second end 22, and a central portion 23. The insulator 20 may have a space 24 extending in the z direction inside.

[0055] The central portion 23 is, for example, a cylinder. The outer shape of the xy cross-section of the central portion 23 is, for example, circular. The central portion 23 has, for example, a space 24 extending in the z direction inside. The xy cross-section of the central portion 23 is, for example, an annular shape.

[0056] The first end portion 21 is, for example, the end portion on the first outer casing 31 side. The first end portion 21 may also be the end portion on the second outer casing 32 side. The first end portion 21 is, for example, a region of a predetermined width from the first end of the insulator 20, where the predetermined width is, for example, 10% of the natural length of the insulator 20. The first end portion 21 protrudes, for example, in the z direction from the power generation element 10.

[0057] The first end portion 21 has, for example, a space 24 extending in the z-direction internally. The space 24 communicates from the interior of the central portion 23 to the interior of the first end portion 21. The outer shape of the xy cross-section of the first end portion 21 is, for example, circular. The xy cross-section of the first end portion 21 is, for example, annular. The shape of the xy cross-section of the first end portion 21 is different from the cross-sectional shape of the xy cross-section of the central portion 23. The xy cross-section of the first end portion 21 is, for example, similar to the xy cross-section of the central portion 23.

[0058] The first end portion 21 is, for example, radially wider than the central portion 23. The first end portion 21 gradually increases in diameter from the central portion 23 toward the first end of the insulator 20. The circumference of the first end portion 21 is, for example, longer than the circumference of the central portion 23. The diameter R1 of the first end portion 21 is, for example, longer than the diameter R2 of the central portion 23.

[0059] The first end portion 21 is deformable, for example, under load in the z direction. When the first end portion 21 is housed within the outer casing 30, for example, it is subjected to load in the z direction and expands radially.

[0060] The second end 22 is the end opposite to the first end 21. The second end 22 is, for example, a region of a predetermined width from the second end of the insulator 20, where the predetermined width is, for example, 10% of the natural length of the insulator 20. The central portion 23 is the region between the first end 21 and the second end 22. The second end 22 protrudes, for example, in the z direction from the power generation element 10.

[0061] The shape of the second end 22 is, for example, different from the shape of the first end 21. The second end 22 is, for example, radially narrower than the central part 23. The second end 22 gradually decreases in diameter from the central part 23 toward the second end of the insulator 20. The circumference of the second end 22 is, for example, shorter than the circumference of the central part 23. The diameter of the second end 22 is, for example, shorter than the diameter R2 of the central part 23. The shape of the second end 22, which tapers toward the second end, facilitates insertion of the insulator 20 into the power generation element 10.

[0062] The shape of the second end portion 22 is not limited to this example. The shape of the second end portion 22 may be the same as the central portion 23, the same as the first end portion 21, or a different shape from these.

[0063] The insulator 20 is made of, for example, a resin. Examples of the insulator 20 include polyethylene terephthalate (PET), polyacetal (POM), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polypropylene (PP), polyethylene (PE), and polytetrafluoroethylene (PTFE).

[0064] (Exterior) The outer casing 30 houses the power generation element 10 and the insulator 20 inside. The outer casing 30 prevents the electrolyte from leaking to the outside and prevents moisture and other substances from entering the inside of the battery 100 from the outside.

[0065] The outer casing 30 comprises a first outer casing 31, a second outer casing 32, and a gasket 33. The first outer casing 31 and the second outer casing 32 sandwich the power generation element 10 in the z direction. The gasket 33 seals the space between the first outer casing 31 and the second outer casing 32.

[0066] The first casing 31 and the second casing 32 are conductors. The first casing 31 and the second casing 32 are made of, for example, metal. The first casing 31 is connected to the positive terminal 4. The second casing 32 is connected to the negative terminal 5. The first casing 31 and the positive terminal 4, and the second casing 32 and the negative terminal 5 are welded together, for example.

[0067] "Battery manufacturing method" The battery 100 comprises a process for manufacturing the power generation element 10 and a process for housing the power generation element 10.

[0068] First, the manufacturing process for the power generation element 10 includes, for example, a preparation step and a winding step. In the preparation step, the positive electrode 1, negative electrode 2, and separator 3 shown in Figure 2 are prepared.

[0069] Positive electrode 1 is manufactured, for example, by sequentially performing a slurry preparation process, an electrode coating process, a drying process, a rolling process, and a terminal connection process.

[0070] The slurry preparation process involves mixing the positive electrode active material, binder, conductive additive, and solvent to create a slurry. The solvent is, for example, water or N-methyl-2-pyrrolidone. The preferred mass ratio of the positive electrode active material, conductive additive, and binder is 70 wt% to 100 wt%: 0 wt% to 10 wt%: 0 wt% to 20 wt%. These mass ratios are adjusted to equal 100 wt% overall.

[0071] The electrode coating process involves applying a slurry to the surface of the positive electrode current collector 1A. There are no particular restrictions on the method of slurry application. For example, the slit die coating method and the doctor blade method can be used as slurry application methods.

[0072] The drying process is a process of removing the solvent from the slurry. For example, the positive electrode current collector 1A coated with slurry is dried in an atmosphere of 80°C to 150°C. As the slurry dries, a positive electrode active material layer 1B is formed on the positive electrode current collector 1A.

[0073] The rolling process is performed as needed. The rolling process involves applying pressure to the positive electrode active material layer 1B to adjust its density. The rolling process is performed, for example, using a roll press or the like.

[0074] The terminal connection process involves connecting the positive electrode terminal 4 to the positive electrode current collector 1A. The positive electrode terminal 4 is connected to an uncoated or removed portion of the positive electrode active material layer 1B. The positive electrode terminal 4 is connected to the positive electrode current collector 1A by, for example, welding or screw fastening.

[0075] The negative electrode 2 can be manufactured using the same procedure as the positive electrode 1. The negative electrode 2 is manufactured by forming a negative electrode active material layer 2B on the surface of the negative electrode current collector 2A and connecting the negative electrode terminal 5 to the negative electrode current collector 2A.

[0076] A commercially available separator 3 can be used. The insulator 20 is attached to one end of the separator 3 located at the innermost circumference.

[0077] In the winding process, the separator 3, positive electrode 1, separator 3, and negative electrode 2 are stacked in order, and the insulator 20 is used as the core for winding. After winding, the power generation element 10 is immersed in the electrolyte. Insulating tape 6 may be applied to the top and bottom surfaces of the power generation element 10.

[0078] The process of housing the power generation element 10 includes a welding process and a sealing process. First, the power generation element 10, the insulator 20, and the gasket 33 are inserted into the first casing 31. The first casing 31 and the positive terminal 4 may be welded together. The welding can be performed by, for example, resistance welding or laser welding. Next, the second casing 32 is inserted into the first casing 31. The insulator 20 is subjected to a load in the z direction by the first casing 31 and the second casing 32. The insulator 20 protruding from the power generation element 10 presses the positive terminal 4 against the first casing 31 and the negative terminal 5 against the second casing 32. The first casing 31 and the second casing 32 are sealed by the gasket 33.

[0079] Here, we have shown an example in which the insulator 20 is attached to the separator 3 and then wound around it, but the insulator 20 may also be inserted into the center of the axis of the winding body after the winding body has been fabricated.

[0080] In the battery 100 according to the first embodiment, the insulator 20 presses the positive terminal 4 against the first outer casing 31 and the negative terminal 5 against the second outer casing 32. As a result, the contact between the positive terminal 4 and the first outer casing 31 and the contact between the negative terminal 5 and the second outer casing 32 are improved.

[0081] Although the first embodiment has been described in detail above with reference to the drawings, the configurations and their combinations in the first embodiment are merely examples, and additions, omissions, substitutions, and other modifications to the configurations are possible without departing from the spirit of the present invention.

[0082] For example, Figure 6 is an xy cross-sectional view of the insulator 20A according to the first modified example. Figure 6 is a cross-section of the first end portion 21A of the insulator 20A. The cross-section and xz cross-section of the central portion 23 of the insulator 20A are the same as those in Figures 3 and 5.

[0083] The insulator 20A differs from the insulator 20 in the shape of its first end 21A. The material of the insulator 20A is the same as that of the insulator 20. The first end 21A has a structure in which the annular first end 21 of the insulator 20 is separated by a slit 25. The first end 21 consists of multiple components, with the slit 25 between the multiple components.

[0084] If the first end portion 21A is separated by multiple slits 25, the first end portion 21A becomes more susceptible to deformation due to loads from the z direction.

[0085] For example, Figure 7 is an xz cross-sectional view of the insulator 20B according to the second modified example. The xz cross-sections of the central portion 23 and the first end portion 21B of the insulator 20B are the same as those in Figures 4 and 5.

[0086] The insulator 20B differs from the insulator 20 in the shape of its first end portion 21B. The material of the insulator 20B is the same as that of the insulator 20. The width of the ring of the first end portion 21B varies depending on its position in the z direction. A portion of the first end portion 21B is thinner, making it more susceptible to deformation under load from the z direction.

[0087] For example, Figures 8 and 9 are cross-sectional views of the insulator 20C according to the third modified example. Figure 8 is an xz cross-sectional view of the insulator 20C according to the third modified example. Figure 9 is an xy cross-section of the first end portion 21C. Figure 9 is a cross-section along line AA in Figure 8. The xz cross-section of the central portion 23 of the insulator 20C is the same as in Figure 5.

[0088] The insulator 20C differs from the insulator 20 in the shape of its first end portion 21C. The material of the insulator 20C is the same as that of the insulator 20. The first end portion 21C has, for example, a base portion 21C1 and a projection portion 21C2. The projection portion 21C2 protrudes from the base portion 21C1 in the z direction. The projection portion 21C2 collapses and deforms when a load is applied in the z direction. In Figure 9, the shape of the projection portion 21C2 is shown as circular, but the shape of the projection portion 21C2 is not limited. The number of projection portions 21C2 is also not limited.

[0089] For example, Figure 10 is an xz cross-sectional view of the insulator 20D according to the fourth modified example. The xz cross-sections of the central portion 23 and the first end portion 21D of the insulator 20D are the same as those in Figures 4 and 5.

[0090] The first end portion 21D is made of a different material than, for example, the central portion 23. The first end portion 21D is made of, for example, rubber. The material constituting the first end portion 21D has a lower modulus of elasticity than, for example, the material constituting the central portion 23. The first end portion 21D deforms when a load is applied in the z direction.

[0091] For example, Figures 11 to 13 are cross-sectional views of the insulator 20E according to the fifth modified example. Figure 11 is an xz cross-sectional view of the insulator 20E according to the fifth modified example. Figure 12 is an xy cross-section of the first end portion 21E. Figure 12 is a cross-section along line AA in Figure 11. Figure 13 is an xy cross-section of the central portion 23E. Figure 13 is a cross-section along line BB in Figure 11.

[0092] The insulator 20E comprises a first end 21E, a second end 22E, and a central portion 23E. The material of the insulator 20E is the same as that of the insulator 20.

[0093] The central portion 23E is, for example, a columnar body having grooves 27 extending in the z-direction on its side. The number of grooves 27 is not specified.

[0094] The first end 21E consists of two members spaced apart in the x-direction. The two members are separated by a slit 26. The first end 21E extends in the x-direction from, for example, the central part 23E. The first end 21E is deformable, for example, under a load in the z-direction. When the first end 21E is housed, for example, within the outer casing 30, it is subjected to a load in the z-direction and expands in the x-direction. The second end 22E differs from the second end 22 in that it does not have a space 24 but has a groove 27.

[0095] While several variations have been shown so far, the variations are not limited to these. For example, each characteristic configuration may be combined. For example, the configuration of the central part and the first end of each variation may be swapped. [Examples]

[0096] "Example 1" A positive electrode slurry was applied to one side of an aluminum foil with a thickness of 15 μm. The positive electrode slurry was prepared by mixing a positive electrode active material, a conductive assistant, a binder, and a solvent.

[0097] LiCoO2 was used as the positive electrode active material. Acetylene black was used as the conductive assistant. Polyvinylidene fluoride (PVDF) was used as the binder. N-methyl-2-pyrrolidone was used as the solvent. 97 parts by mass of the positive electrode active material, 1 part by mass of the conductive assistant, 2 parts by mass of the binder, and 70 parts by mass of the solvent were mixed to prepare the positive electrode slurry. The loading amount of the positive electrode active material in the dried positive electrode active material layer was 22 mg / cm 2 The solvent was removed from the positive electrode slurry in a drying furnace to form a positive electrode active material layer. The positive electrode active material layer was pressed by roll pressing. Then, an aluminum positive electrode terminal was attached to the positive electrode current collector.

[0098] Next, a negative electrode slurry was applied to one side of a copper foil with a thickness of 10 μm. The negative electrode slurry was prepared by mixing a negative electrode active material, a conductive assistant, a binder, and a solvent.

[0099] Graphite was used as the negative electrode active material. Carbon black (Super-P) was used as the conductive assistant. Two types of binders, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC), were used. N-methyl-2-pyrrolidone was used as the solvent. 95 parts by mass of the negative electrode active material, 1 part by mass of the conductive assistant, 2.5 parts by mass of SBR, and 1.5 parts by mass of CMC were mixed in N-methyl-2-pyrrolidone to prepare the negative electrode slurry. The loading amount of the negative electrode active material in the dried negative electrode active material layer was 11 mg / cm 2 The solvent was removed from the negative electrode slurry in a drying furnace to form a negative electrode active material layer. The negative electrode active material layer was pressed by roll pressing and then heat-fired at 300 °C or higher for 5 hours under a nitrogen atmosphere. A nickel negative electrode terminal was attached to the negative electrode current collector.

[0100] The electrolyte was prepared by dissolving 1.0 mol / L of lithium hexafluoride phosphate (LiPF6) in a solvent consisting of equal parts ethylene carbonate (EC) and dimethyl carbonate (DEC). Additionally, 5 wt% fluoroethylene carbonate and 0.01 wt% vinylene carbonate were added to the non-aqueous electrolyte. A porous polyethylene sheet was used as the separator.

[0101] Then, a jelly roll was fabricated by winding a laminate consisting of a separator, a positive electrode, a separator, and a negative electrode in that order. The insulator 20 shown in Figures 3 to 5 was then inserted into the axial center of the jelly roll. The material of the insulator 20 was polypropylene (PP). The natural length of the insulator 20 was 5.0 mm.

[0102] The wound body was housed within the first outer casing, and the positive electrode terminal exposed from the first surface of the wound body was welded to the first outer casing. Next, the second outer casing was inserted into the first outer casing. The first and second outer casings were tightly sealed by a gasket, and the power generation element was housed inside. The length of the perpendicular line drawn from the inner surface of the first outer casing to the inner surface of the second outer casing was 5.0 mm. Since there was a positive electrode terminal between the insulator and the first outer casing, and a negative electrode terminal between the insulator and the second outer casing, a load in the z direction was applied to the insulator 20 by the first and second outer casings. The elastic force of the insulator 20 was 1 N.

[0103] The prepared battery was then dropped from a height of 1 meter, and its resistance was measured. The battery's resistance was measured by touching a tester to the first and second outer casings to determine the DC resistance. The maximum resistance of the battery in Example 1 after the drop experiment was 2.014 Ω.

[0104] Examples 2-5, Comparative Example 1 Examples 2-5 and Comparative Examples 1 and 2 differ from Example 1 in that the pin length was changed. All other conditions were the same as in Example 1, and the maximum resistance after the drop test was measured for each. In Example 2, the natural length was set to 5.1 mm. In Example 3, the natural length was set to 5.15 mm. In Example 4, the natural length was set to 5.2 mm. In Example 5, the natural length was set to 5.3 mm. Comparative Example 1 had a natural length of 4.8 mm.

[0105] The results for Examples 1-5 and Comparative Example 1 are summarized in Table 1 below. As shown in Table 1, Examples 1-5 had lower battery resistance after dropping than Comparative Example 1. This is thought to be because the adhesion between the positive terminal and the first casing, and between the negative terminal and the second terminal, was improved by the presence of the insulator, and the contact resistance between them was kept low.

[0106] [Table 1] [Explanation of Symbols]

[0107] 1...Positive electrode, 1A...Positive electrode current collector, 1B...Positive electrode active material layer, 2...Negative electrode, 2A...Negative electrode current collector, 2B...Negative electrode active material layer, 3...Separator, 4...Positive electrode terminal, 5...Negative electrode terminal, 6...Insulating tape, 10...Power generation element, 20, 20A, 20B, 20C, 20D, 20E...Insulator, 21, 21A, 21B, 21C, 21D, 21E...First end, 22, 22E...Second end, 23, 23E...Center, 24...Space, 25, 26...Slit, 27...Groove, 30...Outer casing, 31...First outer casing, 32...Second outer casing, 31A, 32A...Inner surface, 33...Gasket, 100...Battery

Claims

1. A power generation element comprising a positive electrode to which a positive terminal is connected, a negative electrode to which a negative terminal is connected, and a separator sandwiched between the positive electrode and the negative electrode, An insulator that penetrates the power generation element in a first direction, The power generation element is enclosed by a first outer casing and a second outer casing that sandwich it in the first direction, The insulator presses the positive terminal against the first housing and the negative terminal against the second housing in the first direction. The natural length of the insulator in the first direction is longer than the distance between the first outer casing and the second outer casing in the first direction. The elastic force of the insulator is 1 N or more. A battery in which the first end of the insulator widens radially from the central part of the insulator in the first direction, and the second end of the insulator opposite to the first end narrows radially from the central part of the insulator.

2. The battery according to claim 1, wherein the outer shape of the insulator is circular in a cross-section obtained by cutting the insulator with a plane passing through the center of the insulator in the first direction and perpendicular to the first direction.

3. The battery according to claim 1 or 2, wherein the first end of the insulator is deformable with respect to a load in the first direction.

4. In the cross-section obtained by cutting the insulator through the center in the first direction and with a plane perpendicular to the first direction, The battery according to any one of claims 1 to 3, wherein the cross-sectional shape of the first end of the insulator is different from the cross-sectional shape at the center in the first direction.

5. The battery according to any one of claims 1 to 4, wherein the circumference of the first end of the insulator is longer than the circumference of the insulator at the center in the first direction.

6. The battery according to any one of claims 1 to 5, wherein the first end of the insulator has a space inside that extends in the first direction.

7. The battery according to any one of claims 1 to 6, wherein the insulator has a groove extending in the first direction on its side surface.

8. The battery according to any one of claims 1 to 7, wherein the first end of the insulator has a different shape from the second end opposite to the first end.

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