Plates and coin-shaped secondary batteries

Abstract

The positive electrode plate disclosed herein 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 row, and the active material layer is disposed on each of the plurality of repeating units. The outer edge of the boundary between two adjacent repeating units on the outer edge of the positive electrode current collector has a shape that is convex toward the inner side of the boundary and is composed of a smooth line. The plurality of repeating units are each roughly circular or roughly polygonal.

Description

Technical Field

[0001] The present disclosure relates to a plate and a coin-shaped secondary battery. Background Art

[0002] Flat secondary batteries have traditionally been used as power sources for various electronic devices. Examples of flat secondary batteries include those using wound electrode assemblies and those using zigzag-shaped electrode assemblies. Wound electrode assemblies are formed by winding positive and negative electrode plates with a separator sandwiched between them. For example, Patent Document 1 discloses a battery using a zigzag-shaped electrode assembly.

[0003] Patent Document 1 discloses an example of forming an electrode group by folding the positive electrode plate and the negative electrode plate so that the positive electrode plate extending direction and the negative electrode plate extending direction are offset by 90 degrees (see Patent Document 1). Figure 2 ).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-76329 Summary of the Invention

[0007] In the field of batteries, improving yield is important. One object of the present disclosure is to provide a battery electrode plate that can be manufactured with high yield, and a coin-shaped secondary battery that can be manufactured with high yield.

[0008] One aspect of the present disclosure relates to a plate. The plate includes a current collector and an active material layer disposed on the current collector, the current collector including a plurality of repeating units connected in a row, the active material layer disposed on each of the plurality of repeating units, the outer edge of the boundary between two adjacent repeating units having a shape that bulges inwardly toward the boundary and is formed of a smooth line, and the plurality of repeating units are each substantially circular or substantially polygonal.

[0009] Another aspect of the present disclosure relates to a coin-shaped secondary battery. The coin-shaped secondary battery comprises a coin-shaped shell and a positive electrode plate and a negative electrode plate disposed in the shell, wherein the positive electrode plate comprises a positive electrode collector and a positive electrode active material layer disposed on the positive electrode collector, the negative electrode plate comprises a negative electrode collector and a negative electrode active material layer disposed on the negative electrode collector, the positive electrode collector comprises a plurality of repeating units A connected in a row, the negative electrode collector comprises a plurality of repeating units B connected in a row, the positive electrode active material layer is respectively disposed on the plurality of repeating units A, the negative electrode active material layer is respectively disposed on the plurality of repeating units B, the positive electrode plate and the negative electrode plate are configured so that the positive electrode active material layer and the negative electrode active material layer are mutually opposite. The positive electrode current collector is bent with the boundary X of the two adjacent repeating units A as a bending portion, and the negative electrode current collector is bent with the boundary Y of the two adjacent repeating units B as a bending portion. When the positive electrode current collector is flatly unfolded, the outer edge of the boundary X in the outer edge of the positive electrode current collector has a shape that bulges toward the inner side of the boundary X and is composed of a smooth line. When the negative electrode current collector is flatly unfolded, the outer edge of the boundary Y in the outer edge of the negative electrode current collector has a shape that bulges toward the inner side of the boundary Y and is composed of a smooth line. The multiple repeating units A and the multiple repeating units B are respectively approximately circular or approximately polygonal.

[0010] According to the present disclosure, it is possible to obtain an electrode plate for a battery that can be manufactured with high yield, and a coin-shaped secondary battery that can be manufactured with high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a cross-sectional view schematically showing an example of a coin-shaped secondary battery of the present disclosure.

[0012] Figure 2 It is schematically represented Figure 1 A cross-sectional view of an electrode assembly of a coin-shaped secondary battery is shown.

[0013] Figure 3A It is schematically represented Figure 1 A plan view of an example of a positive electrode plate of a coin-shaped secondary battery shown in FIG.

[0014] Figure 3B It is schematically represented Figure 3A FIG is a diagram of a cross section along line IIIB-IIIB.

[0015] Figure 3C yes Figure 3A A partial enlarged view of the positive electrode collector is shown.

[0016] Figure 4A It is schematically represented Figure 1 A plan view of an example of a negative electrode plate of a coin-shaped secondary battery shown in FIG.

[0017] Figure 4B It is schematically represented Figure 4A FIG. 5 is a diagram of a cross section along line IVB-IVB.

[0018] Figure 4C yes Figure 4A A partial enlarged view of the negative electrode collector is shown. DETAILED DESCRIPTION

[0019] The following describes embodiments of the present disclosure. While the following description provides examples of the embodiments of the present disclosure, the present disclosure is not limited to the examples described below. While specific numerical values ​​and materials are sometimes illustrated in the following description, other numerical values ​​and materials may be used as long as the effects of the present disclosure are achieved.

[0020] (plate)

[0021] The electrode plate disclosed herein is a electrode plate used in 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 respectively approximately circular or approximately polygonal. In the battery, the current collector bends the boundary between two adjacent repeating units as a bend. That is, the electrode plate bends the boundary as a bend.

[0022] When the electrode plate is a positive electrode plate, the current collector, repeating unit, boundary portion, and active material layer can be replaced by positive electrode current collector, repeating unit A, boundary portion X, and positive electrode active material layer, respectively. When the electrode plate is a negative electrode plate, the current collector, repeating unit, boundary portion, and active material layer can be replaced by negative electrode current collector, repeating unit B, boundary portion Y, and negative electrode active material layer, respectively.

[0023] The electrode plate disclosed herein can be used in a coin-shaped secondary battery described later. The positive electrode plate and / or negative electrode plate of the coin-shaped secondary battery described later is an example of the electrode plate disclosed herein. Therefore, the structure of the positive electrode plate and / or negative electrode plate of the coin-shaped secondary battery described later can be applied as the structure of the electrode plate disclosed herein. The current collector and the active material layer are not particularly limited and can be selected according to the type of secondary battery using the electrode plate and the type of electrode plate (positive plate, negative plate). The materials of the current collector and the active material layer can also use well-known materials of the current collector and the active material. Examples of the current collector and the active material layer are described later.

[0024] Hereinafter, the outer edge of the current collector, which is the boundary between two adjacent repeating units, may be referred to as the “outer edge (P).” The outer edge (P) may have the following feature (1).

[0025] (1) The outer edge (P) has a shape that is convex toward the inside of the boundary portion (from another viewpoint, the center of the boundary portion).

[0026] The outer edge (P) has at least one of the following features (2) to (6). In addition to the above feature (1), the outer edge (P) may also have at least one of the features (2) to (6). In addition to the above feature (1), the outer edge (P) may also have any one of the features (2) to (6). For example, the outer edge (P) may also have the feature (1) above and the feature (2) below.

[0027] (2) The outer edge (P) is composed of a smooth line.

[0028] (3) There are no corners at the outer edge (P).

[0029] (4) The outer edge (P) is rounded.

[0030] (5) At the outer edge (P), the tangent vector of the outer edge (P) is not discontinuous. For example, the tangent vector of the outer edge (P) may change continuously.

[0031] (6) The outer edge (P) has a shape obtained by rounding a corner formed by two straight lines.

[0032] Here, the two straight lines are two sides of two polygons when the two polygons are joined to form two shared vertices. The two sides are two unshared sides with a shared vertex as endpoints. These contents will be described in detail in the first embodiment described below.

[0033] When manufacturing an electrode group, the boundary portion of the repeating unit of the electrode plate of the present disclosure is bent. Therefore, when manufacturing an electrode group, a force (tension, etc.) is applied to the boundary portion. In the case where there is a corner at the outer edge (P) of the boundary portion, the force is concentrated at the corner, and the collector is easily broken. The current collector including the outer edge (P) having the above-mentioned characteristics does not have a portion where the force is particularly likely to be concentrated at the boundary portion, so it is not easy to cause breakage, etc. when manufacturing an electrode group. Therefore, the electrode group and the secondary battery can be manufactured with a good yield. Furthermore, by using the electrode plate of the present disclosure, a secondary battery with higher reliability can be obtained.

[0034] A plurality of repeating units are respectively roughly circular or roughly polygonal. An example of a roughly circular shape is a shape formed by two identical arc-shaped curves configured in a line symmetric and point symmetrical manner toward the outside and two straight lines connecting the two curves. An example of such a shape is a shape obtained by cutting a circle (or ellipse) with two parallel lines equidistant 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 axis or minor axis of the ellipse.

[0035] An example of a roughly polygonal shape includes a polygonal portion (a polygonal part) and a portion filling the area between the polygonal portion and the outer edge (P). Hereinafter, the portion filling the area between the polygon and the outer edge (P) is sometimes 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), or a decagon (e.g., a regular decagon). That is, the repeating unit may also be a roughly octagonal or roughly decagonal shape.

[0036] Examples of substantially circular and substantially polygonal shapes include shapes including the above shapes and portions to be bent. For example, examples of substantially polygonal shapes include shapes including polygons and portions to be bent.

[0037] From one viewpoint, the shape of the repeating unit may also be the following shape. That is, when the innermost diameter of the coin-shaped shell in which the electrode plates are arranged is set to F, consider a first circle with a diameter of F and a second circle that is concentric with the first circle and has a diameter of 0.4F. 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 area between the first circle and the second circle (specifically, the area between the circumference of the first circle and the circumference of the second circle). In an example of this case, the diameter of the second circle may also be 0.5F. The innermost diameter F of the shell is not particularly limited. The innermost diameter F may be in the range of 6 mm to 9 mm (for example, 7 mm to 9 mm).

[0038] Furthermore, 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 the shape of the repeating unit B, the shape may be such that the outer edges of the repeating unit A and the outer edges of the repeating unit B both enter the region between the first circle and the second circle.

[0039] The area of ​​the repeating unit A may be larger than the area of ​​the repeating unit B. Alternatively, the area of ​​the repeating unit A may be smaller than the area of ​​the repeating unit B. For example, the width WB of the repeating unit B (see Figure 4C ) can be greater than the width WA of the repeating unit A (refer to Figure 3C ), it can also be smaller than the width WA of the repeating unit A. In addition, the length LB of the repeating unit B (refer to Figure 4C ) can be longer than the length LA of the repeating unit A (refer to Figure 3C ) is longer than, or shorter than the length LA of the repeating unit A. In one example, the area of ​​the repeating unit B is greater than the area of ​​the repeating unit A.

[0040] A current collector comprising multiple repeating units can be formed from a single metal sheet. The active material layers disposed on the multiple repeating units may or may not be connected. For example, the active material layer may not be formed on the bent portion of the current collector.

[0041] 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 may be 3 or more (eg, in the range of 3 to 30, or in the range of 3 to 15).

[0042] The repeating unit at one end of the plurality of repeating units may be connected to a portion (connecting portion) for electrically connecting the current collector to the electrode terminal. The plurality of repeating units and the connecting portion may be formed from a single metal sheet.

[0043] The plurality of repeating units may have a shape in which a plurality of polygons are connected in a row such that two adjacent polygons share two vertices, and the corners of the outer edges at the two vertices are rounded.

[0044] (Coin-shaped secondary battery)

[0045] The coin-shaped secondary battery disclosed herein includes a coin-shaped shell and a positive electrode plate and a negative electrode plate arranged in the shell. The positive electrode plate includes a positive electrode collector and a positive electrode active material layer arranged on the positive electrode collector. The negative electrode plate includes a negative electrode collector and a negative electrode active material layer arranged on the negative electrode collector. The positive electrode collector includes a plurality of repeating units connected in a row (hereinafter sometimes referred to as "repeating unit A"). The negative electrode collector includes a plurality of repeating units connected in a row (hereinafter sometimes referred to as "repeating unit B"). Positive electrode active material layers are respectively arranged on the plurality of repeating units A. Negative electrode active material layers are respectively arranged on the plurality of repeating units B. The positive electrode plate and the negative electrode plate are arranged so that the positive electrode active material layer is opposite to the negative electrode active material layer.

[0046] Furthermore, the coin-shaped secondary battery of the present disclosure also includes secondary batteries having a so-called button-shaped shape. In other words, the coin-shaped casing also includes casings used for so-called button-shaped batteries.

[0047] The positive electrode current collector is bent at the boundary between two adjacent repeating units A (hereinafter sometimes referred to as "boundary X"), while the negative electrode current collector is bent at the boundary between two adjacent repeating units B (hereinafter sometimes referred to as "boundary Y").

[0048] The positive electrode plate and the negative electrode plate are formed by bending the electrode plate of the present disclosure at the boundary portion. Therefore, duplicate descriptions may be omitted.

[0049] When the current collector (positive electrode current collector, negative electrode current collector) is flattened, the outer edge (P) of the boundary portion (boundary portion X, boundary portion Y) between two adjacent repeating units (repeating unit A, repeating unit B) in the outer edge of the current collector has the above-mentioned shape. In addition, as described above, the repeating units (repeating unit A, repeating unit B) are each roughly circular or roughly polygonal.

[0050] Alternatively, when the positive electrode plate is flattened, the outer edge of the boundary portion X in the outer edge of the positive electrode plate may have a shape that is convex toward the inside of the boundary portion X and may be formed by a smooth line. Alternatively, when the negative electrode plate is flattened, the outer edge of the boundary portion Y in the outer edge of the negative electrode plate may have a shape that is convex toward the inside of the boundary portion Y and may be formed by a smooth line.

[0051] When the positive electrode current collector is flatly unfolded, the plurality of repeating units A may have a shape in which the plurality of first polygons are connected in a row in such a manner that two adjacent first polygons have two vertices in common and the corners of the outer edges at the two vertices are rounded. When the negative electrode current collector is flatly unfolded, the plurality of repeating units B may have a shape in which the plurality of second polygons are connected in a row in such a manner that two adjacent second polygons have two vertices in common and the corners of the outer edges at the two vertices are rounded. The number of sides of the first polygon may also be the same as the number of sides of the second polygon. The first polygon and the second polygon may be polygons having substantially the same shape (for example, congruent polygons).

[0052] The outer edge of the boundary portion X (outer edge (P)) and the outer edge of the boundary portion Y (outer edge (P)) may each be rounded with a curve (e.g., an arc) having a curvature radius R. For example, the aforementioned corner of the outer edge (P) may be rounded with a curve (e.g., an arc) having a curvature radius R. Furthermore, the curvature radius of the curve that rounds the outer edge may not be constant.

[0053] The radius of curvature R may be greater than 0.1 mm, greater than 0.3 mm, or greater than 1 mm. The radius of curvature R may be less than 2.5 mm, or less than 2 mm. The radius of curvature R may also be in the range of 0.1 mm to 2.5 mm (for example, in the range of 0.3 mm to 2.0 mm). By rounding the outer edge (P) with a curve having a radius of curvature R of 0.3 mm or greater, the damage to the current collector during the manufacture of the electrode group can be significantly reduced. By rounding the outer edge (P) with a curve having a radius of curvature R of 2.0 mm or less, it is easy to bend the electrode plate during the manufacture of the electrode group.

[0054] Consider the following situation: a plurality of polygons with a side length of S (mm) are connected in a row so that two adjacent polygons share two vertices and the corners of the outer edges at the two vertices are rounded with a curve with a curvature radius of R (mm) (refer to Figure 3C In this case, the length S and the curvature radius R may satisfy the equation of 0.04S≤R≤S, or 0.12S≤R≤0.8S.

[0055] The secondary battery of the present disclosure may also include a separator disposed between the positive electrode plate and the negative electrode plate. Furthermore, 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 non-aqueous electrolyte disposed within the housing. In other words, the secondary battery of the present disclosure may be a non-aqueous electrolyte secondary battery.

[0056] The positive electrode plate and the negative electrode plate may be bent into a zigzag shape or wound separately. In these cases, a separator may be arranged between the positive electrode plate and the negative electrode plate.

[0057] At least a portion of the separator may be fixed to the negative electrode active material layer or to the positive electrode active material layer. By fixing the separator to the active material layer, the manufacture of the battery becomes easier. The method for fixing the separator is not particularly limited, and known techniques can be used. For example, the separator can be fixed to the active material layer by hot pressing or the like. Alternatively, a separator having an adhesive layer on the surface can be used. The adhesive layer can be made of, for example, a layer containing a resin such as polyvinylidene fluoride.

[0058] When the positive electrode plate and the negative electrode plate are respectively bent into a zigzag shape, the positive electrode active material layer may be disposed only on one side of the positive electrode current collector and / or the negative electrode active material layer may be disposed only on one side of the negative electrode current collector.

[0059] 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. Three examples (first to third configuration examples) regarding the number of positive and negative electrode plates and the arrangement of active material layers are described below.

[0060] In the first configuration example, the number of positive electrode plates and the number of negative electrode plates are each one. In this case, the positive electrode active material layer is arranged only on one side of the positive electrode collector, and the negative electrode active material layer is arranged only on one side of the negative electrode collector. In the second configuration example, 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 arranged only on one side of the positive electrode collector, and the negative electrode active material layer is arranged on both sides of the negative electrode collector. In the second configuration example, the positive electrode plates and the negative electrode plates are arranged so that one negative electrode plate is sandwiched between two positive electrode plates. In the third 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 arranged on both sides of the positive electrode collector, and the negative electrode active material layer is arranged only on one side of the negative electrode collector. In the third configuration example, the positive electrode plates and the negative electrode plates are arranged so that one positive electrode plate is sandwiched between two negative electrode plates.

[0061] When the positive electrode plate and the negative electrode plate are wound separately, the positive electrode active material layer may be arranged on both surfaces of the positive electrode current collector, and the negative electrode active material layer may be arranged on both surfaces of the negative electrode current collector.

[0062] The type of the secondary battery disclosed herein is not particularly limited, and may be a nickel-hydrogen secondary battery or a non-aqueous electrolyte secondary battery. Examples of non-aqueous electrolyte secondary batteries include lithium secondary batteries and lithium-ion secondary batteries.

[0063] In addition to using the structure unique to the present disclosure, the constituent elements of the secondary battery disclosed in the present disclosure (shell, material constituting the positive electrode plate, material constituting the negative electrode plate, and other constituent elements, etc.) are not particularly limited. In addition to using the structure unique to the present disclosure, the constituent elements of the secondary battery disclosed in the present disclosure can be applied to known materials and known structures. The following examples illustrate constituent elements when the secondary battery disclosed in the present disclosure is a lithium-ion secondary battery, but the present disclosure is not limited to the following examples.

[0064] (Positive plate)

[0065] Examples of positive electrode current collectors include sheets (e.g., foil, mesh, or punched sheet) made of conductive materials (e.g., metal materials). Examples of metal materials constituting the positive electrode current collector include aluminum, aluminum alloys, titanium, titanium alloys, and stainless steel. The thickness of the positive electrode current collector can be, for example, in the range of 5 μm to 300 μm.

[0066] The positive electrode active material layer contains a positive electrode active material and may also contain other substances (binders, conductive agents, etc.) as needed. Examples of positive electrode active materials include substances that can reversibly absorb and release lithium ions. Specifically, examples of positive electrode active materials include metal oxides containing lithium, lithium-transition metal phosphate compounds, lithium-transition metal sulfate compounds, etc. Examples of metal oxides containing lithium include lithium transition metal composite oxides and lithium-nickel-cobalt-aluminum composite oxides. Examples of lithium transition metal composite oxides include lithium-manganese composite oxides (such as LiMn2O4), lithium-nickel composite oxides (such as LiNiO2), lithium-cobalt composite oxides (such as LiCoO2), and composite oxides in which part of these transition metal elements are replaced by other metal elements (typical metal elements and / or transition metal elements).

[0067] Examples of adhesives include fluororesins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubber polymers. Examples of fluororesins include polytetrafluoroethylene and polyvinylidene fluoride. One type of adhesive may be used alone, or two or more types may be used.

[0068] Examples of conductive agents include carbon materials. Examples of carbon materials used as conductive agents include carbon black (acetylene black, Ketjen Black, etc.), carbon nanotubes, and graphite. A single conductive agent may be used, or two or more conductive agents may be used.

[0069] (Negative plate)

[0070] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer. A portion of the negative electrode current collector may constitute a connection portion electrically connected to a portion of the housing (housing body or sealing plate) functioning as a terminal. In this case, the connection portion is connected to the portion of the housing by welding (e.g., ultrasonic welding).

[0071] Examples of the negative electrode current collector include sheets (e.g., foil, mesh, or punched sheet) made of a conductive material (e.g., a metal material). The metal material of the negative electrode current collector may be a material that does not form an alloy or an intermetallic compound with lithium. Examples of the metal material of the negative electrode current collector include copper, nickel, iron, and alloys containing these metal elements (copper alloys, stainless steel, etc.). 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.

[0072] The negative electrode active material layer contains a negative electrode active material and may also contain other substances (binders, conductive agents, thickeners, etc.) as needed. Examples of negative electrode active materials include substances that reversibly absorb and release lithium ions. Specifically, examples of negative electrode active materials include carbon materials, silicon, silicon compounds, and lithium alloys. Examples of carbon materials include graphite, coke, graphitized carbon, graphitized carbon fibers, and amorphous carbon.

[0073] Examples of binders 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 forms of these rubbers. Examples of conductive agents include those exemplified in the description of the positive electrode active material layer. Examples of thickeners include water-soluble polymers containing carboxyl groups (e.g., carboxymethyl cellulose).

[0074] (Separator)

[0075] Examples of separators include sheets having ion permeability and insulating properties. Alternatively, the separator may be a laminate of multiple sheets including sheets having ion permeability and insulating properties. The separator has the necessary dimensions to insulate the positive electrode plate from the negative electrode plate.

[0076] The separator can also be a microporous membrane, woven fabric, or nonwoven fabric. Examples of separator materials include insulating polymers, specifically polyolefin polymers, polyamide polymers, and cellulose polymers. The separator thickness can be in the range of 5 μm to 200 μm.

[0077] (non-aqueous electrolyte)

[0078] As the non-aqueous electrolyte, a non-aqueous electrolyte having lithium ion conductivity is used. A typical non-aqueous electrolyte comprises a non-aqueous solvent and lithium ions and anions dissolved in the non-aqueous solvent. The non-aqueous electrolyte may be in liquid or gel form. A liquid non-aqueous electrolyte can be prepared by dissolving a lithium salt in a non-aqueous solvent. Lithium ions and anions are generated by dissolving a lithium salt (a salt of lithium ions and anions) in a non-aqueous solvent.

[0079] The gel-like nonaqueous electrolyte comprises a liquid nonaqueous electrolyte and a matrix polymer. For example, a polymer material that absorbs a nonaqueous solvent and forms a gel is used as the matrix polymer. Examples of such polymer materials include fluororesins, acrylic resins, and polyether resins.

[0080] Examples of anions of lithium salts include BF4 － 、ClO4 － PF6 － CF3SO3 － CF3CO2 －, imide anions, oxalic acid complex anions, etc.

[0081] Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and halogen-substituted products thereof (eg, fluorides). The non-aqueous electrolyte may contain only one of these non-aqueous solvents, or may contain two or more.

[0082] Examples of esters include carbonates and carboxylic acid esters. Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, and fluoroethylene carbonate (FEC). Examples of chain carbonates include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone. Examples of chain carboxylic acid esters include ethyl acetate, methyl propionate, and methyl fluoropropionate.

[0083] The concentration of the lithium salt in the non-aqueous electrolyte can be, for example, in the range of 0.5 mol / 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 non-aqueous electrolyte can be in the range of 0.5 mol / L to 3.5 mol / L.

[0084] (case)

[0085] A typical housing includes a housing body, a sealing plate, and a gasket disposed between the housing body and the sealing plate. Typically, the housing body and the sealing plate function as electrode terminals, respectively. For example, in the case of a general coin-shaped battery, the housing body functions as a positive terminal, and the sealing plate functions as a negative terminal. The housing body and the sealing plate can be formed using metal (e.g., conductive stainless steel).

[0086] Hereinafter, an example of a secondary battery disclosed herein and a method for manufacturing the same will be described in detail with reference to the accompanying drawings. The secondary battery described below includes the electrode plate disclosed herein. The components of the secondary battery described below can be modified based on the above description. In addition, the matters described below can also be applied to the above-mentioned embodiments. In addition, components that are not essential to the secondary battery disclosed herein can be omitted.

[0087] (Implementation Method 1)

[0088] Figure 1 2 is a schematic cross-sectional view of a coin-shaped secondary battery according to the first embodiment. Figure 1 The secondary battery 10 includes a coin-shaped case 20, an electrode assembly 30, and a non-aqueous electrolyte (not shown) disposed within the case 20. The case 20 includes a bottomed cylindrical case body 21, a sealing plate 22, and a gasket 23. The case body 21 is sealed by the sealing plate 22 and the gasket 23.

[0089] Figure 2A cross-sectional view of the electrode group 30 is shown in FIG. Figure 2 Along the repeating unit 41A and the repeating unit 51B (refer to Figure 3A and Figure 4A ) is a cross-section in the direction in which the electrodes are connected in a zigzag pattern. The electrode assembly 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 each bent into a zigzag shape. The positive electrode active material layer 42 and the negative electrode active material layer 52 face each other with the separator 60 interposed therebetween.

[0090] (Positive plate)

[0091] Figure 3A FIG. 4 shows a plan view of the positive electrode plate 40 when it is flatly unfolded. Figure 3B Show Figure 3A In addition, Figure 3C A partial enlarged view of the positive electrode current collector 41 is shown. The positive electrode plate 40 includes the positive electrode current collector 41 and a positive electrode active material layer 42 disposed on the positive electrode current collector 41 .

[0092] The positive electrode current collector 41 includes a plurality of repeating units 41A connected in a row. Figure 3A and Figure 3C The boundary 41k between two adjacent repeating units 41A is shown. Multiple repeating units 41A are connected along one direction PD. A positive electrode active material layer 42 is formed on each repeating unit 41A. The positive electrode active material layers 42 disposed on the multiple repeating units 41A are connected. In the electrode assembly 30, the positive electrode current collector 41 and the positive electrode plate 40 are bent so that the boundary 41X between two adjacent repeating units 41A (the periphery of the boundary 41k) is completely bent.

[0093] The repeating unit 41A at one end is connected to the connecting portion 43. In the example shown in the figure, the connecting portion 43 has a shape substantially the same as that of one repeating unit 41A. The connecting portion 43 is a portion connected to the shell body 21, and is connected to the shell body 21 by, for example, welding. The positive electrode active material layer 42 is not configured in the connecting portion 43. In addition, as long as the positive electrode current collector 41 can be electrically connected to the shell body 21, the structure of the connecting portion 43 is not particularly limited. Figure 2 As shown, the boundary between the connecting portion 43 and the repeating unit 41A is also bent as a bent portion.

[0094] refer to Figure 3C , one repeating unit 41A includes an octagonal portion 41Aa and a rounded portion 41Ab. Figure 3CIn the figure, the rounded portion 41Ab is shaded. The shape formed by the plurality of repeating units 41A has a shape in which the plurality of octagonal portions 41Aa are connected in a row so that two adjacent octagonal portions 41Aa share two vertices, and the corners of the outer edges at the two vertices are rounded. The portion with the rounded corners is the rounded portion 41Ab. Figure 3C In the example shown, the corners are rounded with a curve (arc) having a curvature radius R.

[0095] When the positive electrode current collector 41 is flattened, the outer edge of the boundary portion 41X (the bent portion) is convex toward the inside of the boundary portion 41X and is formed as a smooth line. The outer edge of the boundary portion 41X has no corners. The tangent vector of the outer edge of the boundary portion 41X is not discontinuous but changes continuously. Part of the outer edge of the boundary portion 41X may also be a straight line.

[0096] (Negative plate)

[0097] Figure 4A FIG. 2 shows a plan view of the negative electrode plate 50 when it is flatly unfolded. Figure 4B Show Figure 4A In addition, Figure 4C A partial enlarged view of the negative electrode current collector 51 is shown. The negative electrode plate 50 includes the negative electrode current collector 51 and a negative electrode active material layer 52 disposed on the negative electrode current collector 51 .

[0098] The negative electrode current collector 51 includes a plurality of repeating units 51B connected in a row. Figure 4A and Figure 4C The boundary 51k between two adjacent repeating units 51B is shown. Multiple repeating units 51B are connected along one direction ND. A negative electrode active material layer 52 is formed on each repeating unit 51B. The negative electrode active material layers 52 disposed on the multiple repeating units 51B are connected. In the electrode assembly 30, the negative electrode current collector 51 and the negative electrode plate 50 are bent so that the boundary 51Y between two adjacent repeating units 51B (the perimeter of the boundary 51k) is completely bent.

[0099] The repeating unit 51B at one end is connected to the connecting portion 53. In the example shown in the figure, the connecting portion 53 has a shape substantially the same as that of one repeating unit 51B. The connecting portion 53 is a portion connected to the sealing plate 22, and is connected to the sealing plate 22 by welding, for example. The negative electrode active material layer 52 is not configured in the connecting portion 53. In addition, as long as the negative electrode current collector 51 and the sealing plate 22 can be electrically connected, the structure of the connecting portion 53 is not particularly limited. Figure 2 As shown, the boundary between the connecting portion 53 and the repeating unit 51B is also bent as a bent portion.

[0100] refer to Figure 4COne 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 shapes as the octagonal portion 41Aa and the rounded portion 41Ab, respectively. Therefore, the description of the shape of the repeating unit 51B is omitted.

[0101] The outer edges of the boundaries X and Y, which form the bends of the positive and negative current collectors 41 and 51, are formed as smooth lines. Therefore, even when stress is applied to the boundaries X and Y during formation of the electrode assembly 30, damage to the boundaries X and Y is suppressed. On the other hand, if these outer edges have corners, stress may concentrate at these corners, potentially causing damage to the current collectors.

[0102] Furthermore, a short circuit may occur when the positive electrode plate 40 and / or the negative electrode plate 50 contacts the case 20. An insulating member (eg, insulating tape) may be disposed around the electrode group 30 to prevent such a short circuit.

[0103] In embodiment 1, the case where there is only one positive plate, negative plate, and separator constituting the electrode group is described. However, it is also possible that there is only one positive plate and one negative plate, and two other plates. In this case, the active material layer can be formed on both sides of only one electrode plate, and the active material layer can be formed on a single side of each of the other two electrode plates. In this case, two separators can be used. In the case where there is only one positive electrode plate and two negative electrode plates, one positive electrode plate, two negative electrode plates, and two separators can be arranged in the order of negative electrode collector / negative electrode active material layer / separator / positive electrode active material layer / positive electrode collector / positive electrode active material layer / separator / negative electrode active material layer / negative electrode collector and folded into a zigzag shape. Similarly, 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 can be arranged 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 and folded into a zigzag shape. In the case of active material layers formed on both sides of the positive electrode plate (or negative electrode plate), one repeating unit A (or one repeating unit B) includes a positive electrode collector (or negative electrode collector) and positive electrode active material layers (or negative electrode active material layers) arranged on both sides thereof.

[0104] (Method for manufacturing coin-shaped secondary battery)

[0105] An example of a method for manufacturing a secondary battery according to this embodiment will be described. Below, an example of a method for manufacturing the secondary battery 10 described in Embodiment 1 will be described. In the manufacturing process described below, known techniques can be applied. The method for manufacturing a secondary battery according to this embodiment is not limited to the following method.

[0106] First, prepare the positive electrode plate 40 and the negative electrode plate 50. In one example of a method for producing the positive electrode plate 40, first, the 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 (such as a metal foil) to be the positive electrode collector 41 to form the positive electrode active material layer 42. The positive electrode plate 40 is produced in this way. The positive electrode plate 40 and the positive electrode collector 41 are made to have the above-mentioned structure (planar shape). The positive electrode plate 40 can also be produced by forming the positive electrode active material layer 42 in a predetermined area of ​​a conductive sheet with a large area and then punching out the conductive sheet and the positive electrode active material layer 42 together using a punching die.

[0107] In one example of a method for producing the negative electrode plate 50, first, the 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 (e.g., metal foil) to be the negative electrode current collector 51 to form the negative electrode active material layer 52. In this manner, the negative electrode plate 50 is produced. The negative electrode plate 50 and the negative electrode current collector 51 are produced to have the above-described structure (planar shape). Alternatively, the negative electrode active material layer 52 may be formed in a predetermined area of ​​a large conductive sheet, and then the conductive sheet and the negative electrode active material layer 52 may be punched out together using a punching die to produce the negative electrode plate 50.

[0108] Next, the positive electrode plate 40, the negative electrode plate 50, and the separator 60 are arranged so that the positive electrode active material layer 42 and the negative electrode active material layer 52 are opposite to each other with the separator 60 interposed therebetween. Then, the electrode group 30 is produced by bending them together into a zigzag shape. Alternatively, the positive electrode plate 40, the negative electrode plate 50, and the separator 60 may be bent and then combined to produce the electrode group 30. In addition, in the production of the electrode group 30, at least a portion of the separator may be fixed to the positive electrode plate 40 or the negative electrode plate 50 before the electrode plates are bent. By pre-fixing the separator, the production of the electrode group becomes easier. The separator can be fixed by the above-mentioned method.

[0109] In addition, a chimeric body is formed by fitting the sealing plate 22 to the gasket 23. Next, the connecting portion 43 is electrically connected to the housing body 21. Similarly, the connecting portion 53 is electrically connected to the sealing plate 22. These electrical connections can be implemented, for example, by welding (ultrasonic welding, etc.). In addition, as needed, before or after the connection of the connecting portion, the surrounding of the electrode group 30 is protected by an insulating member.

[0110] The electrode assembly 30 and the nonaqueous electrolyte are then placed within the assembly of the sealing plate 22 and the gasket 23. The case body 21 is then positioned to seal the opening of the assembly. The open end of the case body 21 is then bent and snapped together to seal the opening. This completes the secondary battery 10 of Embodiment 1.

[0111] If the electrode assembly 30 is a wound-type electrode assembly, the positive and negative electrode plates 40, 50, and separator 60 are first wound together, with the separator 60 disposed between the positive and negative electrode plates 40, 50, to form a wound body. The wound body is then flattened to form a flat shape. The wound body is flattened so that the boundaries (rounded portions) of the repeating units form flattened bends. In this manner, a wound-type electrode assembly 30 can be produced.

[0112] Example

[0113] The present disclosure is described in more detail by way of examples. In this example, a Figure 1 Secondary batteries having the same structure as the secondary battery 10 shown were evaluated. In this example, multiple secondary batteries (batteries A1 to A6 and C1) having different current collector shapes were produced. The production and evaluation of these secondary batteries will be described below.

[0114] (Battery A1)

[0115] In Example 1, a Figure 1 The battery has the same structure as the secondary battery 10 shown in FIG. Repeating unit A (equivalent to Figure 3A The planar shape of the repeating unit 41A is set to be a regular octagon with a side of 2.5 mm. The length LA of the repeating unit A along the direction PD and the width WA perpendicular to the direction PD (refer to Figure 3C ) are 6 mm. The positive electrode current collector has a shape formed by connecting fifteen regular octagons in a row and rounding the corners of the outer edges of the boundaries of two adjacent regular octagons. Specifically, the corners are rounded with a curve having a curvature radius R of 1.0 mm. The repeating unit B of the negative electrode current collector (equivalent to Figure 4A The number of repeating units 51B) is the same as the number of repeating units A. The length LB in the direction ND of the repeating unit B (refer to Figure 4C ) is the same as the length LA. In addition, the width WB perpendicular to the direction ND is slightly larger than the width WA.

[0116] The positive electrode mixture constituting the positive electrode active material layer is prepared by mixing lithium cobalt oxide (LiCoO2) as a positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder in a mass ratio of lithium cobalt oxide: acetylene black: polyvinylidene fluoride = 9:0.1:0.1. Aluminum foil is used as the positive electrode collector. A positive electrode active material layer with a thickness of 55 μm is formed by applying the positive electrode mixture to one side of the positive electrode collector. In addition, the active material layer is not configured at two parts at one end of the fifteen regular octagonal parts, serving as connecting parts for welding. That is, the number of repeating units A configured with the positive electrode active material layer is thirteen.

[0117] The negative electrode mixture constituting the negative electrode active material layer was prepared by mixing graphite as the negative electrode active material, carboxymethyl cellulose (CMC) as the thickener, and styrene-butadiene rubber (SBR) as the binder at a mass ratio of graphite:CMC:SBR = 9:0.1:0.1. Copper foil was used as the negative electrode current collector.

[0118] A microporous polyolefin membrane (14 μm thick) was used as the separator. The nonaqueous electrolyte was prepared by dissolving LiPF6 in a nonaqueous solvent. The nonaqueous solvent was prepared by mixing ethylene carbonate, propylene carbonate, and ethyl methyl carbonate in a volume ratio of ethylene carbonate:propylene carbonate:ethyl methyl carbonate = 30:1:61.

[0119] The positive and negative plates are prepared using the above materials. Then, the positive and negative plates and the separators are bent into a zigzag electrode group (see Figure 2 Next, a coin-shaped nonaqueous electrolyte secondary battery was fabricated using the electrode assembly, nonaqueous electrolyte, and coin-shaped casing using the above method. The resulting secondary battery had an outer diameter of 9.5 mm and a height of 2.0 mm. The innermost diameter of the casing was 7.5 mm.

[0120] (Batteries A2 to A6)

[0121] Batteries A2 to A6 were fabricated under the same conditions as Battery A1, except that the shape of the boundary between two adjacent repeating units A was modified. Specifically, the curvature of the curve used to round the corners of the outer edges of these boundaries was varied within a range of 0.1 mm to 2.5 mm. The curvatures used in each battery are shown in Table 1 below.

[0122] (Battery C1)

[0123] Battery C1 was produced under the same conditions as Battery A1 except that the corners of the outer edges of the boundaries between two adjacent regular octagons were not rounded.

[0124] (Evaluation of Yield in Electrode Assembly Production)

[0125] Ten electrode assemblies were produced for each of the batteries A1 to A6 and C1. The current conduction status of the positive and negative current collectors was then verified to assess whether the current collectors were damaged. If no current flowed, the product was considered defective; if it did, it was considered acceptable. The yield (%) was then calculated based on the number of electrode assemblies produced and the number of acceptable products. The yield is expressed as follows.

[0126] Yield rate (%) = 100 × (number of qualified products) / (number of products produced)

[0127] (Charge and discharge test)

[0128] The above-mentioned batteries A1 to A6 and C1 were subjected to a charge and discharge cycle test. The charging process was performed by charging at a current value of 6 mA until the battery voltage reached 4.35 V, and then applying a constant voltage of 4.35 V until the current value reached 0.5 mA. The discharging process was performed by discharging at a current value of 6 mA until the battery voltage reached 3.0 V. A charge and discharge cycle consisting of one charging process and one discharging process was considered as one cycle, and charging and discharging were repeated. Then, the number of charge and discharge cycles n until the battery capacity reached 80% of the initial battery capacity was evaluated. In addition, for batteries (batteries A3, A1, A4, A5, A6) whose battery capacity was greater than 80% of the initial battery capacity after 1000 cycles, the number of charge and discharge cycles n in Table 1 was set to 1000. The evaluation results are shown in Table 1.

[0129] [Table 1]

[0130]

[0131] As shown in Table 1, compared to battery C1 without rounded corners, batteries A1 to A6, whose boundary corners were rounded, had a higher electrode assembly yield and a greater number of charge-discharge cycles. The yield of the electrode assembly was particularly high and the number of charge-discharge cycles was particularly high when the curvature radius was in the range of 0.3 mm to 2.5 mm.

[0132] Industrial applicability

[0133] The present disclosure can be applied to electrode plates and coin-shaped secondary batteries.

[0134] Description of Reference Numerals

[0135] 10. Secondary battery; 20. Casing; 40. Positive electrode plate; 41. Positive electrode collector; 41A, 51B, repeating unit; 41Aa, 51Ba, octagonal portion (polygonal portion); 41Ab, 51Bb, rounded portion; 41k, 51k, boundary; 41X, 51Y, boundary portion; 42. Positive electrode active material layer; 50. Negative electrode plate; 51. Negative electrode collector; 52. Negative electrode active material layer; 60. Separator.

Claims

1. A 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 respectively arranged on the plurality of repeating units, The outer edge of the boundary between two adjacent repeating units in the outer edge of the current collector has a shape that is convex toward the inside of the boundary and is composed of a smooth line. The multiple repeating units are respectively roughly polygonal, The plurality of repeating units have a shape in which a plurality of polygons are connected in a row so that two adjacent polygons share two vertices, and the corners of the outer edges at the two vertices are rounded. The corners of the outer edges at the two vertices are rounded with a curve having a curvature radius R. The length S of one side of the polygon and the curvature radius R satisfy 0.04S≤R≤S, The curvature radius R is in the range of 0.3mm to 2.5mm, The substantially polygonal portion includes a polygonal portion and a portion filling an area between the polygonal portion and the outer edge P, wherein the polygonal portion is a regular polygon. The outer edge P is the outer edge of the boundary between two adjacent repeating units in the outer edge of the current collector.

2. The electrode plate according to claim 1, wherein: The length S and the curvature radius R satisfy 0.12S≤R≤0.8S.

3. A coin-shaped secondary battery comprising a coin-shaped housing and a positive electrode plate and a negative electrode plate disposed in the housing, 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 row, The positive electrode active material layer is respectively arranged on the plurality of repeating units A, The negative electrode active material layer is respectively arranged on the plurality of repeating units B, The positive electrode plate and the negative electrode plate are arranged so that the positive electrode active material layer faces the negative electrode active material layer. The positive electrode current collector is bent with the boundary X between two adjacent repeating units A serving as a bent portion. The negative electrode current collector is bent with the boundary Y between two adjacent repeating units B serving as a bent portion. When the positive electrode current collector is flattened, the outer edge of the boundary portion X in the outer edge of the positive electrode current collector has a shape that is convex toward the inside of the boundary portion X and is composed of a smooth line. When the negative electrode current collector is flattened, the outer edge of the boundary portion Y of the outer edge of the negative electrode current collector has a shape that is convex toward the inside of the boundary portion Y and is composed of a smooth line. The plurality of repeating units A and the plurality of repeating units B are respectively roughly polygonal, When the positive electrode current collector is flattened, the plurality of repeating units A have a shape in which a plurality of first polygons are connected in a row so that two adjacent first polygons share two vertices, and the corners αA of the outer edges at the two vertices are rounded. When the negative electrode current collector is flattened, the plurality of repeating units B have a shape in which a plurality of second polygons are connected in a row so that two adjacent second polygons share two vertices, and the corners αB of the outer edges at the two vertices are rounded. The number of sides of the first polygon is the same as the number of sides of the second polygon, The corner αA is rounded with a curve having a curvature radius R1. The corner αB is rounded with a curve having a curvature radius R2. The length S1 of one side of the first polygon and the curvature radius R1 satisfy 0.04S1≤R1≤S1, The length S2 of one side of the second polygon and the curvature radius R2 satisfy 0.04S2≤R2≤S2, The curvature radius R1 and the curvature radius R2 are respectively in the range of 0.3 mm to 2.5 mm. The substantially polygonal portion includes a polygonal portion and a portion filling an area between the polygonal portion and the outer edge P, wherein the polygonal portion is a regular polygon. The outer edge of the boundary portion X in the outer edge of the positive electrode current collector is the outer edge P, and the outer edge of the boundary portion Y in the outer edge of the negative electrode current collector is the outer edge P.

4. The coin-shaped secondary battery according to claim 3, wherein The length S1 and the curvature radius R1 satisfy 0.12S1≤R1≤0.8S1, The length S2 and the curvature radius R2 satisfy 0.12S2≤R2≤0.8S2.

5. The coin-shaped secondary battery according to claim 3, wherein The coin-shaped secondary battery further includes a separator disposed between the positive electrode plate and the negative electrode plate, and a non-aqueous electrolyte disposed in the case.

6. The coin-shaped secondary battery according to claim 3, wherein The positive electrode plate and the negative electrode plate are respectively bent into a zigzag shape or respectively wound.

7. The coin-shaped secondary battery according to claim 3, wherein The positive electrode plate and the negative electrode plate are respectively bent into a zigzag shape, The positive electrode active material layer is disposed only on one side of the positive electrode current collector and / or the negative electrode active material layer is disposed only on one side of the negative electrode current collector.

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