CN115298868A

CN115298868A - Polar plate and coin-shaped secondary battery

Info

Publication number: CN115298868A
Application number: CN202180021797.1A
Authority: CN
Inventors: 绵寿惠; 熊谷淳
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2020-03-25
Filing date: 2021-02-08
Publication date: 2022-11-04
Also published as: WO2021192658A1; JPWO2021192658A1

Abstract

The positive electrode plate of the present disclosure includes a positive electrode current collector and an active material layer disposed on the positive electrode current collector. The positive electrode current collector includes a plurality of repeating units connected in a line, and an active material layer is disposed on each of the plurality of repeating units. The outer edge of the boundary portion of two adjacent repeating units in the outer edge of the positive electrode collector has a shape that is convex toward the inside of the boundary portion, and is constituted by a smooth line. The plurality of repeating units are each substantially circular or substantially polygonal.

Description

Pole plate and coin-shaped secondary battery

Technical Field

The present disclosure relates to a polar plate and a coin-shaped secondary battery.

Background

Conventionally, flat secondary batteries are used as power sources for various electronic devices. Examples of flat secondary batteries include batteries using wound electrode groups and batteries using electrode groups bent in a zigzag manner. The wound electrode group is formed by winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween. For example, patent document 1 discloses a battery using an electrode group folded in a zigzag shape.

Patent document 1 discloses an example in which a positive electrode plate and a negative electrode plate are arranged such that the direction in which the positive electrode plate extends and the direction in which the negative electrode plate extends are shifted by 90 ° and are folded to form an electrode group (see fig. 2 of patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2016-76329

Disclosure of Invention

In the field of batteries, it is important to improve the yield. An object of the present disclosure is to provide a plate electrode capable of manufacturing a battery with high yield and a coin-shaped secondary battery capable of manufacturing a battery with high yield.

One aspect of the present disclosure relates to a pole plate. The electrode plate includes a current collector and an active material layer disposed on the current collector, the current collector includes a plurality of repeating units connected in a line, the active material layer is disposed on each of the plurality of repeating units, an outer edge of a boundary portion of two adjacent repeating units among outer edges of the current collector has a shape protruding toward an inner side of the boundary portion and is formed of a smooth line, and each of the plurality of repeating units is substantially circular or substantially polygonal.

Another aspect of the present disclosure relates to a coin-shaped secondary battery. The coin-shaped secondary battery includes a coin-shaped case, and a positive electrode plate and a negative electrode plate disposed in the case, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the positive electrode current collector includes a plurality of repeating units A connected in a row, the negative electrode current collector includes a plurality of repeating units B connected in a row, the positive electrode active material layer is disposed on each of the plurality of repeating units A, the negative electrode active material layer is disposed on each of the plurality of repeating units B, and the positive electrode plate and the negative electrode plate are disposed such that the positive electrode active material layer and the negative electrode active material layer are opposed to each other, the positive electrode current collector is formed by bending a boundary portion X of two adjacent repeating units a as a bent portion, the negative electrode current collector is formed by bending a boundary portion Y of two adjacent repeating units B as a bent portion, an outer edge of the boundary portion X among outer edges of the positive electrode current collector has a shape protruding toward an inner side of the boundary portion X when the positive electrode current collector is spread flatly and is formed by a smooth line, an outer edge of the boundary portion Y among outer edges of the negative electrode current collector has a shape protruding toward an inner side of the boundary portion Y when the negative electrode current collector is spread flatly and is formed by a smooth line, and the plurality of repeating units a and the plurality of repeating units B are each substantially circular or substantially polygonal.

According to the present disclosure, it is possible to obtain a pole plate capable of manufacturing a battery with a high yield and a coin-shaped secondary battery capable of manufacturing a battery with a high yield.

Drawings

Fig. 1 is a cross-sectional view schematically showing an example of a coin-shaped secondary battery of the present disclosure.

Fig. 2 is a sectional view schematically showing an electrode group of the coin-shaped secondary battery shown in fig. 1.

Fig. 3A is a plan view schematically showing an example of the positive electrode plate of the coin-shaped secondary battery shown in fig. 1.

Fig. 3B is a view schematically showing a cross section of line IIIB-IIIB of fig. 3A.

Fig. 3C is a partially enlarged view of the positive electrode collector shown in fig. 3A.

Fig. 4A is a plan view schematically showing an example of the negative electrode plate of the coin-shaped secondary battery shown in fig. 1.

Fig. 4B is a view schematically showing a cross section of line IVB-IVB of fig. 4A.

Fig. 4C is a partially enlarged view of the negative electrode collector shown in fig. 4A.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described. In the following description, embodiments of the present disclosure are described by way of examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials are shown in some cases, but other numerical values and materials may be applied as long as the effects of the present disclosure can be obtained.

(Pole plate)

The electrode plate of the present disclosure is an electrode plate used for a coin-shaped secondary battery, and is a positive electrode plate and/or a negative electrode plate. The electrode plate includes a current collector and an active material layer disposed on the current collector. The current collector includes a plurality of repeating units connected in a row. An active material layer is disposed on each of the plurality of repeating units. The plurality of repeating units are each substantially circular or substantially polygonal. In the battery, the current collector is bent with the boundary portion between two adjacent repeating units as a bent portion. That is, the electrode plate is bent with the boundary portion as a bent portion.

When the electrode plate is a positive electrode plate, the current collector, the repeating unit, the boundary portion, and the active material layer may be referred to as a positive electrode current collector, the repeating unit a, the boundary portion X, and the positive electrode active material layer, respectively. When the electrode plate is a negative electrode plate, the current collector, the repeating unit, the boundary portion, and the active material layer may be referred to as a negative electrode current collector, a repeating unit B, a boundary portion Y, and a negative electrode active material layer, respectively.

The electrode plate of the present disclosure can be used for a coin-shaped secondary battery described later. The positive electrode plate and/or the negative electrode plate of a coin-shaped secondary battery described later are examples of the electrode plate of the present disclosure. Therefore, the structure of the positive electrode plate and/or the negative electrode plate of the coin-shaped secondary battery described later can be applied to the structure of the electrode plate of the present disclosure. The current collector and the active material layer are not particularly limited, and may be selected according to the type of secondary battery using the electrode plate and the type of electrode plate (positive electrode plate and negative electrode plate). As the material of the current collector and the active material layer, known materials of the current collector and the active material layer can be used. Examples of the current collector and the active material layer are described later.

Hereinafter, the outer edge of the boundary portion between two adjacent repeating units in the outer edge of the current collector may be referred to as "outer edge (P)". The outer edge (P) may have the following characteristic (1).

(1) The outer edge (P) has a shape that is convex toward the inside of the boundary portion (the center of the boundary portion in another point of view).

The outer edge (P) has at least one of the following features (2) to (6). The outer edge (P) may have at least one of the features (2) to (6) in addition to the feature (1) described above. The outer edge (P) may have any of the features (2) to (6) in addition to the feature (1) described above. For example, the outer edge (P) may have the feature (1) and the feature (2) below.

(2) The outer edge (P) is formed by a smooth line.

(3) There is no corner at the outer edge (P).

(4) The outer edge (P) is rounded.

(5) At the outer edge (P), the tangent vector to the outer edge (P) is not discontinuous. For example, the tangent vector of the outer edge (P) may be continuously changed.

(6) The outer edge (P) has a shape in which the corner portion formed by two straight lines is rounded.

Here, the two straight lines are two sides of two polygons when the two polygons are joined to share two vertices. The two edges are two edges not in common with a vertex in common as an end point. These matters will be specifically described in embodiment 1 described later.

When an electrode group is produced, the boundary portion of the repeating unit of the electrode plate of the present disclosure is bent. Therefore, when the electrode group is manufactured, a force (tension, etc.) is applied to the boundary portion. When a corner portion exists at the outer edge (P) of the boundary portion, the force concentrates on the corner portion, and the current collector is easily broken. The current collector including the outer edge (P) having the above-described characteristics has no portion where forces are particularly likely to concentrate at the boundary portion, and therefore, breakage or the like is less likely to occur at the time of manufacturing the electrode group. Therefore, the electrode group and the secondary battery can be manufactured with high yield. Further, by using the electrode plate of the present disclosure, a secondary battery with high reliability can be obtained.

The plurality of repeating units are each substantially circular or substantially polygonal. An example of the substantially circular shape is a shape formed by two identical circular arc-shaped curves that are line-symmetric and point-symmetric so as to protrude outward, and two straight lines connecting the two curves. An example of such a shape is a shape obtained by cutting a circle (or ellipse) from two parallel lines at equal distances from the center of the circle (or ellipse). In addition, in the case of an ellipse, the two parallel lines are parallel to the major or minor axis of the ellipse.

An example of the substantially polygonal shape includes a polygonal portion (polygonal portion) and a portion filling a region between the polygonal portion and the outer edge (P). Hereinafter, a portion filling a region between the polygon and the outer edge (P) may be referred to as a "rounded portion". The number of sides constituting the polygonal portion may be in the range of 6 to 12. For example, the polygonal portion may be a hexagon (e.g., a regular hexagon), an octagon (e.g., a regular octagon), a decagon (e.g., a regular decagon). That is, the repeating unit may be substantially octagonal or substantially decagonal.

Examples of the substantially circular and substantially polygonal shapes include a shape including the above-described shape and a portion to be a bent portion. For example, examples of the substantially polygonal shape include a shape including a polygon and a portion to be a bent portion.

In one aspect, the shape of the repeating unit may be as follows. That is, when the innermost diameter of the coin-shaped case in which the pole plates are arranged is F, a1 st circle having a diameter F and a2 nd circle having a diameter of 0.4F and concentric with the 1 st circle are considered. At this time, the shape of the repeating unit may be a shape in which the outer edge of the repeating unit entirely enters the region between the 1 st circle and the 2 nd circle (specifically, the region between the circumference of the 1 st circle and the circumference of the 2 nd circle). In one example of this case, the diameter of the 2 nd circle may also be 0.5F. The innermost diameter F of the housing is not particularly limited. The innermost diameter F may be in the range of 6mm to 9mm (e.g., 7mm to 9 mm).

The shape of the repeating unit a of the positive electrode plate and the shape of the repeating unit B of the negative electrode plate may be the same or different. When the shape of the repeating unit a is different from that of the repeating unit B, the outer edge of the repeating unit a and the outer edge of the repeating unit B may be in the region between the 1 st circle and the 2 nd circle.

The area of the repeating unit a may be larger than that of the repeating unit B. Alternatively, the area of the repeating unit a may be smaller than that of the repeating unit B. For example, the width WB (see fig. 4C) of the repeating unit B may be larger than the width WA (see fig. 3C) of the repeating unit a, or may be smaller than the width WA of the repeating unit a. The length LB of the repeating unit B (see fig. 4C) may be longer than the length LA of the repeating unit a (see fig. 3C), or may be shorter than the length LA of the repeating unit a. In one example, the area of repeat unit B is greater than the area of repeat unit a.

The current collector including a plurality of repeating units can be composed of one metal sheet. The active material layers disposed on the plurality of repeating units may or may not be connected to each other. For example, the active material layer may not be formed in the portion of the bent portion of the current collector.

The number of repeating units contained in one current collector is not particularly limited, and may be in the range of 2 to 30, or 3 or more (for example, in the range of 3 to 30, or in the range of 3 to 15).

A portion (connection portion) for electrically connecting the current collector to the electrode terminal may be connected to the repeating unit existing at one end among the plurality of repeating units. The plurality of repeating units and the connecting portion can be constituted by one metal sheet.

The plurality of repeating units may have a shape in which a plurality of polygons are connected in a line in such a manner that two adjacent polygons share two vertices, and corners of the outer edge at the two vertices are rounded.

(coin-shaped secondary battery)

The coin-shaped secondary battery of the present disclosure includes a coin-shaped case, and a positive electrode plate and a negative electrode plate disposed in the case. The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The positive electrode current collector includes a plurality of repeating units (hereinafter, may be referred to as "repeating unit a") connected in a line. The negative electrode current collector includes a plurality of repeating units (hereinafter, may be referred to as "repeating unit B") connected in a line. The positive electrode active material layer is disposed on each of the plurality of repeating units a. The negative electrode active material layer is disposed on each of the plurality of repeating units B. The positive electrode plate and the negative electrode plate are arranged such that the positive electrode active material layer faces the negative electrode active material layer.

In addition, the coin-shaped secondary battery of the present disclosure also includes a secondary battery having a shape called a button shape. That is, the coin-shaped case also includes a case used for a battery called a button-shaped case.

The positive electrode current collector is bent at a boundary portion between two adjacent repeating units a (hereinafter, sometimes referred to as "boundary portion X") as a bent portion. The negative electrode current collector is bent at a boundary portion between two adjacent repeating units B (hereinafter, sometimes referred to as "boundary portion Y") as a bent portion.

The positive electrode plate and the negative electrode plate are formed by bending the electrode plate of the present disclosure at a boundary portion. Therefore, a repetitive description may be omitted.

When the current collectors (positive electrode current collector, negative electrode current collector) are spread flat, the outer edge (P) of the boundary (boundary X, boundary Y) between two adjacent repeating units (repeating unit a, repeating unit B) in the outer edge of the current collector has the above-described shape. As described above, the repeating units (repeating unit a and repeating unit B) are each substantially circular or substantially polygonal.

When the positive electrode plate is spread flat, the outer edge of the boundary portion X of the outer edge of the positive electrode plate may have a shape protruding inward of the boundary portion X and be formed of a smooth line. When the negative electrode plate is developed flatly, the outer edge of the boundary portion Y of the outer edge of the negative electrode plate may have a shape protruding toward the inside of the boundary portion Y and be formed of a smooth line.

When the positive electrode collector is spread flat, the plurality of repeating units a may have a shape in which a plurality of 1 st polygons are connected in a line such that two adjacent 1 st polygons share two vertices, and corners of outer edges at the two vertices are rounded. When the anode current collector is spread out flat, the plurality of repeating units B may have a shape in which a plurality of 2 nd polygons are connected in a line such that two adjacent 2 nd polygons share two vertices, and corners of outer edges at the two vertices are rounded. The number of sides of the 1 st polygon may be the same as the number of sides of the 2 nd polygon. The 1 st polygon and the 2 nd polygon may be polygons (e.g., congruent polygons) having substantially the same shape.

The outer edge of the boundary portion X (outer edge (P)) and the outer edge of the boundary Y (outer edge (P)) may be rounded with a curve of a curvature radius R (e.g., an arc), respectively. For example, the above-described corner portion of the outer edge (P) may be rounded with a curve (e.g., a circular arc) of a curvature radius R. Further, the curvature radius of the curve rounding the outer edge may not be constant.

The radius of curvature R may be 0.1mm or more, 0.3mm or more, or 1mm or more. The radius of curvature R may be 2.5mm or less, or may be 2mm or less. The radius of curvature R may be in the range of 0.1mm to 2.5mm (for example, in the range of 0.3mm to 2.0 mm). By rounding the outer edge (P) with a curve having a curvature radius R of 0.3mm or more, damage to the current collector during the production of the electrode assembly can be significantly reduced. The outer edge (P) is rounded by a curve with a curvature radius R of 2.0mm or less, so that the electrode plate is easily bent when the electrode group is manufactured.

Consider the following: a plurality of polygons each having a side length S (mm) are connected in a row so that two adjacent polygons share two vertices, and corners of the outer edge at the two vertices are rounded with a curve having a radius of curvature R (mm) (see fig. 3C). In this case, the length S and the radius of curvature R may satisfy the expression 0.04 S.ltoreq.R.ltoreq.S, or may satisfy 0.12 S.ltoreq.R.ltoreq.0.8S.

The secondary battery of the present disclosure may also include a separator disposed between the positive electrode plate and the negative electrode plate. The secondary battery of the present disclosure may further include a separator disposed between the positive electrode plate and the negative electrode plate, and a nonaqueous electrolyte disposed in the case. That is, the secondary battery of the present disclosure may be a nonaqueous electrolyte secondary battery.

The positive and negative plates may be respectively bent in a zigzag shape or respectively wound. In these cases, a separator may be disposed between the positive electrode plate and the negative electrode plate.

At least a part of the separator may be fixed to the negative electrode active material layer or the positive electrode active material layer. By fixing the separator to the active material layer, the battery can be easily manufactured. The method of fixing the separator is not particularly limited, and a known technique can be used. For example, the separator may be fixed to the active material layer by hot pressing or the like. Alternatively, a separator having an adhesive layer on the surface thereof may be used. For the adhesive layer, a layer containing a resin such as polyvinylidene fluoride can be used.

In the case where the positive electrode plate and the negative electrode plate are each folded in a zigzag shape, the positive electrode active material layer may be disposed only on one surface of the positive electrode current collector and/or the negative electrode active material layer may be disposed only on one surface of the negative electrode current collector.

The secondary battery of the present disclosure may include at least one positive electrode plate and at least one negative electrode plate such that the sum of the number of positive electrode plates and the number of negative electrode plates is 2 or 3. Hereinafter, 3 examples (1 st to 3 rd embodiments) relating to the number of positive and negative electrode plates and the arrangement of the active material layers will be described.

In configuration example 1, the number of positive electrode plates and the number of negative electrode plates are one each. In this case, the positive electrode active material layer is disposed on only one surface of the positive electrode current collector and the negative electrode active material layer is disposed on only one surface of the negative electrode current collector. In configuration example 2, the number of positive electrode plates is two, and the number of negative electrode plates is one. In this case, the positive electrode active material layer is disposed on only one surface of the positive electrode current collector, and the negative electrode active material layer is disposed on both surfaces of the negative electrode current collector. In configuration example 2, the positive electrode plate and the negative electrode plate are arranged such that one negative electrode plate is sandwiched between two positive electrode plates. In the 3 rd configuration example, the number of negative electrode plates is two, and the number of positive electrode plates is one. In this case, the positive electrode active material layer is disposed on both surfaces of the positive electrode current collector, and the negative electrode active material layer is disposed on only one surface of the negative electrode current collector. In configuration example 3, the positive electrode plate and the negative electrode plate are arranged so that one positive electrode plate is sandwiched between two negative electrode plates.

When the positive electrode plate and the negative electrode plate are wound separately, the positive electrode active material layer may be disposed on both surfaces of the positive electrode current collector, and the negative electrode active material layer may be disposed on both surfaces of the negative electrode current collector.

The type of the secondary battery of the present disclosure is not particularly limited, and may be a nickel hydride secondary battery or a nonaqueous electrolyte secondary battery. Examples of the nonaqueous electrolyte secondary battery include a lithium secondary battery and a lithium ion secondary battery.

The constituent elements (the case, the material constituting the positive electrode plate, the material constituting the negative electrode plate, and other constituent elements) of the secondary battery of the present disclosure are not particularly limited except for using the configuration unique to the present disclosure. In addition to the specific structure of the present disclosure, known materials and known structures can be applied to the constituent elements of the secondary battery of the present disclosure. The following illustrates constituent elements in the case where the secondary battery of the present disclosure is a lithium-ion secondary battery, but the present disclosure is not limited to the following examples.

(Positive plate)

Examples of the positive electrode current collector include a sheet (e.g., foil, mesh, or punched sheet) made of a conductive material (e.g., a metal material). Examples of the metal material constituting the positive electrode current collector include aluminum, aluminum alloys, titanium alloys, stainless steel, and the like. The thickness of the positive electrode current collector may be, for example, in the range of 5 μm to 300 μm.

The positive electrode active material layer contains a positive electrode active material, and may contain other materials (a binder, a conductive agent, and the like) as needed. Examples of the positive electrode active material include materials that reversibly occlude and release lithium ions. Specifically, examples of the positive electrode active material include a lithium-containing metal oxide, a lithium-transition metal phosphate compound, a lithium-transition metal sulfate compound, and the like. Metallic oxygen containing lithiumExamples of the compound include lithium-containing transition metal composite oxides, lithium-nickel-cobalt-aluminum composite oxides, and the like. Examples of the lithium transition metal composite oxide include lithium-manganese composite oxides (e.g., liMn) ₂ O ₄ ) Lithium-nickel composite oxide (e.g., liNiO) ₂ ) Lithium-cobalt composite oxide (e.g., liCoO) ₂ ) And a composite oxide in which a part of these transition metal elements is replaced with another metal element (typical metal element and/or transition metal element).

Examples of the adhesive include fluorine-containing resins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, rubbery polymers, and the like. Examples of the fluororesin include polytetrafluoroethylene, polyvinylidene fluoride, and the like. Only one kind of the adhesive may be used, or two or more kinds of the adhesives may be used.

Examples of the conductive agent include a carbon material. Examples of the carbon material used as the conductive agent include carbon black (acetylene black, ketjen black, etc.), carbon nanotubes, and graphite. The conductive agent may be used alone or in combination of two or more.

(negative plate)

The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer. A part of the negative electrode current collector may constitute a connection portion electrically connected to a part of the case (the case main body or the sealing plate) functioning as a terminal. In this case, the connection portion is connected to a part of the housing by welding (e.g., ultrasonic welding) or the like.

Examples of the negative electrode collector include a sheet (for example, a foil, a mesh, or a punched sheet) made of a conductive material (for example, a metal material) and the like. The metal material of the negative electrode collector may be a material that does not form an alloy or intermetallic compound with lithium. Examples of the metal material of the negative electrode collector include copper, nickel, iron, and alloys containing these metal elements (copper alloys, stainless steel, and the like). In a preferred example, the metal material of the negative electrode current collector is copper or a copper alloy. The thickness of the negative electrode current collector may be, for example, in the range of 5 μm to 300 μm.

The negative electrode active material layer contains a negative electrode active material, and may contain other materials (a binder, a conductive agent, a thickener, and the like) as needed. Examples of the negative electrode active material include materials that reversibly occlude and release lithium ions. Specifically, examples of the negative electrode active material include a carbon material, silicon, a silicon compound, a lithium alloy, and the like. Examples of the carbon material include graphite, coke, graphitized carbon fiber, amorphous carbon, and the like.

Examples of the adhesive include fluororesins such as polyvinylidene fluoride (PVDF), acrylic resins such as polymethyl acrylate and ethylene-methyl methacrylate copolymer, styrene-butadiene rubber, acrylic rubber, and modified products of these rubbers. Examples of the conductive agent include the conductive agents exemplified in the description of the positive electrode active material layer. Examples of the thickener include a water-soluble polymer having a carboxyl group (e.g., carboxymethyl cellulose).

(spacer)

Examples of the separator include a sheet having ion permeability and insulation properties. The separator may be a separator in which a plurality of sheets including a sheet having ion permeability and insulation properties are laminated. The separator has a size necessary for insulating the positive electrode plate from the negative electrode plate.

The separator may be a microporous film, woven fabric, or nonwoven fabric. Examples of the material of the separator include insulating polymers, specifically, polyolefin polymers, polyamide polymers, cellulose polymers, and the like. The thickness of the separator may be in the range of 5 μm to 200 μm.

(non-aqueous electrolyte)

As the nonaqueous electrolyte, a nonaqueous electrolyte having lithium ion conductivity is used. A typical nonaqueous electrolyte contains a nonaqueous solvent and lithium ions and anions dissolved in the nonaqueous solvent. The nonaqueous electrolyte may be in a liquid state or a gel state. The liquid nonaqueous electrolyte can be prepared by dissolving a lithium salt in a nonaqueous solvent. Lithium ions and anions are generated by dissolving a lithium salt (a salt of lithium ions and anions) in a nonaqueous solvent.

The gel-like nonaqueous electrolyte includes a liquid nonaqueous electrolyte and a matrix polymer. For example, a polymer material gelled by absorbing a nonaqueous solvent is used as the matrix polymer. Examples of such polymer materials include fluorine-containing resins, acrylic resins, polyether resins, and the like.

Examples of the anion of the lithium salt include BF ₄ ^－、ClO ₄ ^－、PF ₆ ^－、CF ₃ SO ₃ ^－、CF ₃ CO ₂ ^－ An imide anion, an anion of an oxalic acid complex, and the like.

Examples of the nonaqueous solvent include esters, ethers, nitriles, amides, halogen substitutes thereof (e.g., fluorides), and the like. The nonaqueous electrolyte may contain only one kind of these nonaqueous solvents, or may contain two or more kinds.

Examples of the ester include a carbonate, a carboxylate and the like. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, fluoroethylene carbonate (FEC) and the like. Examples of the chain carbonate include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and the like. Examples of the cyclic carboxylic acid ester include γ -butyrolactone, γ -valerolactone and the like. Examples of the chain carboxylic acid ester include ethyl acetate, methyl propionate, methyl fluoropropionate, and the like.

The concentration of the lithium salt in the nonaqueous electrolyte may be, for example, in the range of 0.5mol/L to 3.5 mol/L. Here, the concentration of the lithium salt is the sum of the concentration of the dissociated lithium salt and the concentration of the undissociated lithium salt. The concentration of the anion in the nonaqueous electrolyte may be in the range of 0.5mol/L to 3.5 mol/L.

(case)

A typical case includes a case body, a sealing plate, and a gasket disposed between the case body and the sealing plate. Usually, the case main body and the sealing plate function as electrode terminals, respectively. For example, in the case of a general coin-shaped battery, the case main body functions as a positive electrode terminal, and the sealing plate functions as a negative electrode terminal. The case body and the sealing plate can be formed of metal (e.g., conductive stainless steel).

Hereinafter, an example of the secondary battery and the method for manufacturing the same according to the present disclosure will be described in detail with reference to the drawings. The secondary battery described below includes the electrode plate of the present disclosure. The constituent elements of the secondary battery described below can be modified based on the above description. Further, matters described below may be applied to the above-described embodiments. In addition, the components that are not essential to the secondary battery of the present disclosure can be omitted.

(embodiment mode 1)

Fig. 1 schematically shows a cross-sectional view of a coin-shaped secondary battery according to embodiment 1. The secondary battery 10 of fig. 1 includes a coin-shaped case 20, and an electrode group 30 and a nonaqueous electrolyte (not shown) disposed in the case 20. The case 20 includes a cylindrical case body 21 having a bottom, a sealing plate 22, and a gasket 23. Case body 21 is sealed by sealing plate 22 and gasket 23.

A cross-sectional view of the electrode assembly 30 is shown in fig. 2. Fig. 2 is a cross section along a direction in which the repeating unit 41A and the repeating unit 51B (refer to fig. 3A and 4A) are connected in a zigzag shape. The electrode group 30 includes a positive electrode plate 40, a negative electrode plate 50, and a separator 60 disposed therebetween. The positive electrode plate 40, the negative electrode plate 50, and the separator 60 are folded in a zigzag shape. The positive electrode active material layer 42 and the negative electrode active material layer 52 face each other with a separator 60 interposed therebetween.

(Positive plate)

Fig. 3A shows a plan view when the positive electrode plate 40 is spread flat, and fig. 3B shows a cross-sectional view of the line IIIB-IIIB of fig. 3A. Fig. 3C is a partially enlarged view of the positive electrode current collector 41. The positive electrode plate 40 includes a positive electrode current collector 41 and a positive electrode active material layer 42 disposed on the positive electrode current collector 41.

The positive electrode collector 41 includes a plurality of repeating units 41A connected in a line. Fig. 3A and 3C show the boundary 41k of two adjoining repeating units 41A. The plurality of repeating units 41A are connected along one direction PD. A positive electrode active material layer 42 is formed on each of the repeating units 41A. The positive electrode active material layers 42 respectively disposed on the plurality of repeating units 41A are connected. In the electrode group 30, the positive electrode collector 41 and the positive electrode plate 40 are all bent as bent portions at the boundary portions 41X (the peripheral portions of the boundaries 41 k) of the two adjacent repeating units 41A.

The repeating unit 41A at one end is connected to the connecting portion 43. In the illustrated example, the connection portion 43 has substantially the same shape as the one repeating unit 41A. The connection portion 43 is a portion connected to the case main body 21, and is connected to the case main body 21 by welding or the like, for example. The positive electrode active material layer 42 is not disposed in the connection portion 43. The structure of the connection portion 43 is not particularly limited as long as the positive electrode current collector 41 can be electrically connected to the case main body 21. As shown in fig. 2, the boundary between connection portion 43 and repeating unit 41A is also bent as a bent portion.

Referring to fig. 3C, one repeating unit 41A includes an octagonal portion 41Aa having an octagonal shape and a rounded portion 41Ab. In fig. 3C, the rounded portion 41Ab is hatched. The shape formed by the plurality of repeating units 41A has a shape in which a plurality of octagonal portions 41Aa are connected in a line so that two adjacent octagonal portions 41Aa share two vertices, and corners of the outer edge at the two vertices are rounded. The rounded portion of the corner is a rounded portion 41Ab. In the example shown in fig. 3C, the corner portions are rounded off by a curve (arc) having a radius of curvature R.

When the positive electrode current collector 41 is developed flatly, the outer edge of the boundary portion 41X (bent portion) has a shape that is convex toward the inside of the boundary portion 41X, and is constituted by a smooth line. The outer edge of the boundary portion 41X has no corner. The tangent vector of the outer edge of the boundary portion 41X is not discontinuous but continuously changes. The outer edge of the boundary portion 41X may be locally linear.

(negative plate)

Fig. 4A shows a plan view when the negative electrode plate 50 is developed flatly, and fig. 4B shows a cross-sectional view of a line IVB-IVB of fig. 4A. Fig. 4C shows a partially enlarged view of the negative electrode current collector 51. The negative electrode plate 50 includes a negative electrode current collector 51 and a negative electrode active material layer 52 disposed on the negative electrode current collector 51.

The negative electrode collector 51 includes a plurality of repeating units 51B connected in a line. Fig. 4A and 4C show the boundary 51k of two adjoining repeating units 51B. The plurality of repeating units 51B are connected along one direction ND. The negative electrode active material layer 52 is formed on each of the repeating units 51B. The negative electrode active material layers 52 arranged on the plurality of repeating units 51B are connected to each other. In the electrode group 30, the negative electrode collector 51 and the negative electrode plate 50 are all bent as bent portions at the boundary portions 51Y (the peripheral portions of the boundaries 51 k) of two adjacent repeating units 51B.

The repeating unit 51B at one end is connected to the connecting portion 53. In the illustrated example, the connection portion 53 has substantially the same shape as one of the repeating units 51B. The connecting portion 53 is a portion connected to the sealing plate 22, and is connected to the sealing plate 22 by welding or the like, for example. The negative electrode active material layer 52 is not disposed on the connection portion 53. The structure of the connection portion 53 is not particularly limited as long as the negative electrode current collector 51 can be electrically connected to the sealing plate 22. As shown in fig. 2, the boundary between the connection portion 53 and the repeating unit 51B is also bent as a bent portion.

Referring to fig. 4C, one repeating unit 51B includes an octagonal portion 51Ba and a rounded portion 51Bb. The octagonal portion 51Ba and the rounded portion 51Bb have the same shape as the octagonal portion 41Aa and the rounded portion 41Ab, respectively. Therefore, the shape of the repeating unit 51B is not described.

The outer edges of the boundary portions X and Y of the positive electrode collector 41 and the negative electrode collector 51, which are bent portions, are formed of smooth lines. Therefore, even when stress is applied to the boundary portions X and Y when the electrode group 30 or the like is formed, damage to the boundary portions X and Y can be suppressed. On the other hand, when there is a corner portion at the outer edge, stress is concentrated at the corner portion, and the current collector is likely to be broken.

In addition, when the positive electrode plate 40 and/or the negative electrode plate 50 are in contact with the can 20, a short circuit may occur. An insulating member (e.g., an insulating tape) for preventing such short circuit may be disposed around the electrode group 30.

In embodiment 1, a case where only one of each of the positive electrode plate, the negative electrode plate, and the separator constituting the electrode group is used has been described. However, only one of the positive electrode plate and the negative electrode plate may be provided, and the other may be provided in two. In this case, the active material layer may be formed on both surfaces of only one electrode plate, and the active material layer may be formed on one surface of each of the other two electrode plates. In this case, two separators may be used. In the case of only one positive electrode plate and two negative electrode plates, one positive electrode plate, two negative electrode plates, and two separators may be arranged and folded in a zigzag shape in the order of negative electrode current collector/negative electrode active material layer/separator/positive electrode active material layer/positive electrode current collector/positive electrode active material layer/separator/negative electrode active material layer/negative electrode current collector. Likewise, in the case of only one negative electrode plate and two positive electrode plates, the two positive electrode plates, one negative electrode plate, and two separators may be arranged and folded in a zigzag shape in the order of positive electrode collector/positive electrode active material layer/separator/negative electrode active material layer/negative electrode collector/negative electrode active material layer/separator/positive electrode active material layer/positive electrode collector. In the case where active material layers are formed on both surfaces of the positive electrode plate (or the negative electrode plate), one repeating unit a (or one repeating unit B) includes a positive electrode current collector (or a negative electrode current collector) and positive electrode active material layers (or negative electrode active material layers) disposed on both surfaces thereof.

(method for manufacturing coin-shaped Secondary Battery)

An example of the method for manufacturing the secondary battery of the present embodiment will be described. An example of the method for manufacturing the secondary battery 10 described in embodiment 1 will be described below. In the manufacturing process described below, a known technique can be applied. The method for manufacturing the secondary battery according to the present embodiment is not limited to the following manufacturing method.

First, the positive electrode plate 40 and the negative electrode plate 50 are prepared. In one example of the method for manufacturing the positive electrode plate 40, first, materials constituting the positive electrode active material layer 42 are mixed to prepare a positive electrode mixture. Next, the positive electrode mixture is applied to a conductive sheet (for example, a metal foil) to be the positive electrode current collector 41, thereby forming the positive electrode active material layer 42. The positive electrode plate 40 is thus produced. The positive electrode plate 40 and the positive current collector 41 are made to have the above-described structure (planar shape). The positive electrode plate 40 may be produced by forming the positive electrode active material layer 42 in a predetermined region of the large-area conductive sheet, and then punching the conductive sheet and the positive electrode active material layer 42 together using a punching die.

In one example of the method for producing the negative electrode plate 50, first, materials constituting the negative electrode active material layer 52 are mixed to prepare a negative electrode mixture. Next, the negative electrode mixture is applied to a conductive sheet (for example, a metal foil) to be the negative electrode current collector 51 to form the negative electrode active material layer 52. The negative electrode plate 50 is thus produced. The negative electrode plate 50 and the negative electrode collector 51 are fabricated to have the above-described structure (planar shape). The negative electrode plate 50 may be produced by forming the negative electrode active material layer 52 in a predetermined region of a large-area conductive sheet, and then punching the conductive sheet together with the negative electrode active material layer 52 using a punching die.

Next, the positive electrode plate 40, the negative electrode plate 50, and the separator 60 are arranged such that the positive electrode active material layer 42 and the negative electrode active material layer 52 face each other with the separator 60 interposed therebetween. Then, the electrode group 30 is manufactured by folding them together in a zigzag shape. The electrode group 30 may be produced by folding the positive electrode plate 40, the negative electrode plate 50, and the separator 60 and then combining them. In the production of the electrode group 30, at least a part of the separator may be fixed to the positive electrode plate 40 or the negative electrode plate 50 before the electrode plates are folded. By fixing the separator in advance, the electrode group can be easily manufactured. The fixing of the separator can be performed by the above-described method.

Further, the sealing plate 22 is fitted to the gasket 23 to form a fitting body. Subsequently, the connection portion 43 is electrically connected to the case main body 21. Similarly, the connection portion 53 is electrically connected to the sealing plate 22. These electrical connections can be made by, for example, soldering (ultrasonic soldering or the like). Further, the periphery of the electrode group 30 is protected with an insulating member before or after the connection of the connection portions as necessary.

The electrode group 30 and the nonaqueous electrolyte are then placed in the fitting body of the sealing plate 22 and the gasket 23. Next, the case main body 21 was arranged to seal the opening of the fitting, and thereafter, the open end of the case main body 21 was bent and snapped (japanese: 123631237512417. In this way, the secondary battery 10 of embodiment 1 can be obtained.

When the electrode group 30 is a wound-type electrode group, the positive electrode plate 40, the negative electrode plate 50, and the separator 60 are wound together to form a wound body such that the separator 60 is disposed between the positive electrode plate 40 and the negative electrode plate 50. After that, the roll was flattened to a flat shape. At this time, the wound body is flattened so that the boundary portion (rounded portion) of the repeating unit becomes a bent portion having a flat shape. In this manner, the wound electrode group 30 can be manufactured.

Examples

The present disclosure is illustrated in more detail by examples. In this example, a secondary battery having the same structure as the secondary battery 10 shown in fig. 1 was produced and evaluated. In this example, a plurality of types of secondary batteries (batteries A1 to A6 and C1) having different shapes of current collectors were produced. The production and evaluation of these secondary batteries will be described below.

(Battery A1)

In example 1, a battery having the same structure as the secondary battery 10 shown in fig. 1 was produced. The planar shape of the repeating unit a (corresponding to the repeating unit 41A in fig. 3A) is a substantially regular octagon having 2.5mm on one side. The length LA of the repeating unit a in the direction PD and the width WA (see fig. 3C) perpendicular to the direction PD are 6mm, respectively. The positive electrode current collector has a shape in which fifteen regular octagons are connected in a row and corners of outer edges of boundary portions of two adjacent regular octagons are rounded. Specifically, the corner portion is rounded with a curve having a curvature radius R of 1.0 mm. The number of the repeating units B (corresponding to the repeating units 51B of fig. 4A) of the negative electrode collector is the same as the number of the repeating units a. The length LB (see fig. 4C) in the direction ND of the repeating unit B is the same as the length LA. The width WB perpendicular to the direction ND is slightly larger than the width WA.

By using lithium cobalt oxide (LiCoO) as the positive electrode active material ₂ ) Acetylene black as a conductive agent and polyvinylidene fluoride as a binder are mixed in the following ratio of lithium cobalt oxide: acetylene black: polyvinylidene fluoride =9:0.1: a positive electrode mixture constituting the positive electrode active material layer was prepared by mixing at a mass ratio of 0.1. Aluminum foil was used as the positive electrode current collector. A positive electrode active material layer having a thickness of 55 μm was formed by applying a positive electrode mixture to one surface of the positive electrode current collector. In addition, an active material layer is not disposed in two portions at one end among the fifteen regular octagonal-shaped portions as a connection portion for soldering. That is, the number of the repeating units a provided with the positive electrode active material layer is thirteen.

Graphite as a negative electrode active material, carboxymethyl cellulose (CMC) as a thickener, and Styrene Butadiene Rubber (SBR) as a binder were mixed in the following ratio of graphite: CMC: SBR =9:0.1:0.1 by mass ratio, to prepare a negative electrode mixture constituting the negative electrode active material layer. The negative electrode current collector uses a copper foil.

For the separator, a microporous membrane (thickness: 14 μm) made of polyolefin was used. Passing LiPF through a non-aqueous electrolyte ₆ Dissolved in a nonaqueous solvent. By mixing ethylene carbonate, propylene carbonate and ethyl methyl carbonate with ethylene carbonate: propylene carbonate: ethyl methyl carbonate =30:1:61 to prepare a non-aqueous solvent.

The above materials were used to prepare positive and negative plates. Then, an electrode group in which the positive electrode plate, the negative electrode plate, and the separator were bent in a zigzag shape was produced (see fig. 2). Then, a coin-shaped nonaqueous electrolyte secondary battery was produced by the above method using the electrode group, nonaqueous electrolyte, and coin-shaped case. The dimensions of the secondary battery obtained were 9.5mm in outer diameter and 2.0mm in height. In addition, the innermost diameter of the shell was 7.5mm.

(batteries A2 to A6)

Batteries A2 to A6 were produced under the same conditions as battery A1, except that the shape of the boundary between two adjacent repeating units a was changed. Specifically, the curvature of a curve obtained by rounding the corner portions of the outer edge of the boundary portion is varied within a range of 0.1mm to 2.5 mm. The curvature used in each battery is shown in table 1 described later.

(Battery C1)

The battery C1 was produced under the same conditions as the battery A1, except that the corners of the outer edges of the boundary portions of the two adjacent regular octagons were not rounded.

(evaluation of yield in producing electrode group)

10 electrode groups of the batteries A1 to A6 and C1 were prepared. Then, the current-carrying states of the positive electrode current collector and the negative electrode current collector are checked to evaluate whether or not the current collectors are damaged, that is, if the current-carrying is impossible, the current collector is determined to be a defective product, and if the current-carrying is possible, the current collector is determined to be a non-defective product. Then, the yield (%) was determined from the number of electrode groups produced and the number of non-defective products. The yield is represented by the following formula.

Yield (%) =100 × (number of non-defective products)/(number of produced articles)

(Charge and discharge test)

The batteries A1 to A6 and C1 were subjected to a charge-discharge cycle test. The charging process was performed by charging the battery at a current value of 6mA until the battery voltage became 4.35V, and then applying a constant voltage of 4.35V until the current value became 0.5 mA. The discharge step was performed by discharging at a current value of 6mA until the cell voltage became 3.0V. Charge and discharge are repeated with a charge and discharge cycle consisting of a primary charge step and a primary discharge step as one cycle. Then, the number of charge/discharge cycles n until the battery capacity reached 80% of the initial battery capacity was evaluated. In addition, the number of charge and discharge cycles n in table 1 was set to 1000 for the batteries (batteries A3, A1, A4, A5, and A6) having a battery capacity greater than 80% of the initial battery capacity at the stage of the passage of 1000 cycles. The evaluation results are shown in table 1.

[ Table 1]

As shown in table 1, the electrode group yield was higher in the batteries A1 to A6 in which the corners of the boundary portions were rounded, and the number of charge and discharge cycles was larger, compared to the battery C1 having no rounded portion. When the radius of curvature is in the range of 0.3mm to 2.5mm, the electrode group yield is particularly high, and the number of charge and discharge cycles is particularly large.

Industrial applicability

The present disclosure can be used for a pole plate and a coin-shaped secondary battery.

Description of the reference numerals

10. A secondary battery; 20. a housing; 40. a positive plate; 41. a positive electrode current collector; 41A, 51B, repeat units; 41Aa, 51Ba, an octagonal portion (polygonal portion); 41Ab, 51Bb, radius; 41k, 51k, boundary; 41X, 51Y, boundary portion; 42. a positive electrode active material layer; 50. a negative plate; 51. a negative electrode current collector; 52. a negative electrode active material layer; 60. a separator.

Claims

1. An electrode plate comprising a current collector and an active material layer disposed on the current collector, wherein,

the current collector comprises a plurality of repeating units connected in a row,

the active material layer is disposed on each of the plurality of repeating units,

an outer edge of a boundary portion of adjacent two of the repeating units among outer edges of the current collector has a shape that is convex toward an inner side of the boundary portion and is composed of a smooth line,

the plurality of repeating units are each substantially circular or substantially polygonal.

2. The plate of claim 1,

the plurality of repeating units have a shape in which a plurality of polygons are connected in a line such that two adjoining polygons share two vertices, and corners of outer edges at the two vertices are rounded.

3. A coin-shaped secondary battery comprising a coin-shaped can and a positive electrode plate and a negative electrode plate disposed in the can, wherein,

the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector,

the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector,

the positive electrode current collector comprises a plurality of repeating units (A) connected in a row,

the negative electrode current collector comprises a plurality of repeating units (B) connected in a line,

the positive electrode active material layer is disposed on each of the plurality of repeating units (A),

the negative electrode active material layer is disposed on each of the plurality of repeating units (B),

the positive electrode plate and the negative electrode plate are arranged such that the positive electrode active material layer opposes the negative electrode active material layer,

the positive electrode current collector is bent with a boundary portion (X) between two adjacent repeating units (A) as a bent portion,

the negative electrode current collector is bent with a boundary portion (Y) between two adjacent repeating units (B) as a bent portion,

an outer edge of the boundary portion (X) of outer edges of the positive electrode collector has a shape that is convex toward an inner side of the boundary portion (X) when the positive electrode collector is spread flat, and is constituted by a smooth line,

an outer edge of the boundary portion (Y) among outer edges of the negative electrode collector has a shape that is convex toward an inner side of the boundary portion (Y) when the negative electrode collector is spread flat and is constituted by a smooth line,

the plurality of repeating units (a) and the plurality of repeating units (B) are each substantially circular or substantially polygonal.

4. The coin-shaped secondary battery according to claim 3,

the plurality of repeating units (A) have a shape in which a plurality of 1 st polygons are connected in a line such that two adjacent 1 st polygons share two vertices and corners of outer edges at the two vertices are rounded when the positive electrode current collector is spread flat,

the plurality of repeating units (B) have a shape in which a plurality of 2 nd polygons are connected in a line such that two adjacent 2 nd polygons share two vertices and corners of outer edges at the two vertices are rounded when the negative electrode current collector is spread flat,

the number of sides of the 1 st polygon is the same as the number of sides of the 2 nd polygon.

5. The coin-shaped secondary battery according to claim 3 or 4,

the outer edge of the boundary portion (X) and the outer edge of the boundary portion (Y) are rounded by curves having a radius of curvature in the range of 0.3mm to 2.0mm, respectively.

6. The coin-shaped secondary battery according to any one of claims 3 to 5,

the coin-shaped secondary battery further includes a separator disposed between the positive electrode plate and the negative electrode plate, and a nonaqueous electrolyte disposed in the case.

7. The coin-shaped secondary battery according to any one of claims 3 to 6,

the positive plate and the negative plate are respectively bent into a zigzag shape or respectively wound.

8. The coin-shaped secondary battery according to any one of claims 3 to 6,

the positive plate and the negative plate are respectively bent into a zigzag shape,

the positive electrode active material layer is disposed on only one surface of the positive electrode current collector and/or the negative electrode active material layer is disposed on only one surface of the negative electrode current collector.