WO2021192658A1

WO2021192658A1 - Electrode plate and coin-shaped secondary battery

Info

Publication number: WO2021192658A1
Application number: PCT/JP2021/004506
Authority: WO
Inventors: とし惠綿; 淳熊谷
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2020-03-25
Filing date: 2021-02-08
Publication date: 2021-09-30
Also published as: JPWO2021192658A1; CN115298868A

Abstract

Disclosed is a positive electrode plate which comprises a positive electrode collector and an active material layer arranged on the positive electrode collector. The positive electrode collector comprises a plurality of repeating units that are aligned in a row, and an active material layer is arranged on each of the plurality of repeating units. The positive electrode collector has an outer edge which, at a boundary portion between two adjacent repeating units, has a shape that protrudes toward the inside of the boundary part and is composed of a smooth line. Each one of the plurality of repeating units has a generally circular shape or a generally polygonal shape.

Description

Plate and coin-shaped secondary battery

This disclosure relates to a electrode plate and a coin-type secondary battery.

Flat secondary batteries have traditionally been used as power sources for various electronic devices. Examples of a flat secondary battery include a battery using a winding electrode group and a battery using a zigzag bent electrode group. The winding type electrode group is formed by sandwiching a separator between a positive electrode plate and a negative electrode plate and winding them. A battery using a group of electrodes bent in a zigzag manner is disclosed in, for example, Patent Document 1.

Patent Document 1 discloses an example in which the direction in which the positive electrode plate extends and the direction in which the negative electrode plate extends are arranged so as to be offset by 90 °, and they are folded to form an electrode group (see FIG. 2 of Patent Document 1). ..

Japanese Unexamined Patent Publication No. 2016-76329

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

One aspect of this disclosure relates to the electrode plate. The electrode plate is an electrode plate including a current collector and an active material layer arranged on the current collector, and the current collector includes a plurality of repeating units connected in a row, and the plurality of repeating units. The active material layer is arranged on each of the repeating units, and the outer edge of the boundary portion of two adjacent repeating units among the outer edges of the current collector is convex toward the inside of the boundary portion. It has a shape and is composed of smooth lines, and each of the plurality of repeating units is a substantially circular shape or a substantially polygonal shape.

Another aspect of this disclosure relates to coin-type secondary batteries. The coin-shaped secondary battery is a coin-shaped secondary battery including a coin-shaped case and a positive electrode plate and a negative electrode plate arranged in the case, and the positive electrode plate is a positive electrode current collector and the positive electrode. The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer arranged on the negative electrode current collector, and the positive electrode current collector includes a positive electrode active material layer arranged on the current collector. , A plurality of repeating units A connected in a row are included, the negative electrode current collector includes a plurality of repeating units B connected in a row, and the positive electrode active material layer is placed on each of the plurality of repeating units A. The negative electrode active material layer is arranged on each of the plurality of repeating units B, and the positive electrode plate and the negative electrode plate are the positive electrode active material layer and the negative electrode active material layer. Are arranged so as to face each other, the positive electrode current collector is bent with the boundary portion X of the two adjacent repeating units A as a bent portion, and the boundary portion Y of the two adjacent repeating units B is bent. The negative electrode current collector is bent as a bent portion, and when the positive electrode current collector is deployed flat, the outer edge of the boundary portion X among the outer edges of the positive electrode current collector is inside the boundary portion X. The outer edge of the boundary portion Y of the outer edges of the negative electrode current collector is formed when the negative electrode current collector is spread flat. , The boundary portion Y has a convex shape toward the inside and is composed of smooth lines, and each of the plurality of repeating units A and the plurality of repeating units B is substantially circular or substantially many. It is a square.

According to the present disclosure, a electrode plate capable of manufacturing a battery with a high yield and a coin-type secondary battery capable of manufacturing a battery with a high yield can be obtained.

It is sectional drawing which shows typically an example of the coin-type secondary battery of this disclosure. It is sectional drawing which shows typically the electrode group of the coin-type secondary battery shown in FIG. It is a top view which shows an example of the positive electrode plate of the coin-type secondary battery shown in FIG. 1 schematically. It is a figure which shows typically the cross section in the line IIIB-IIIB of FIG. 3A. It is a partially enlarged view of the positive electrode current collector shown in FIG. 3A. It is a top view which shows an example of the negative electrode plate of the coin-type secondary battery shown in FIG. 1 schematically. It is a figure which shows typically the cross section in the line IVB-IVB of FIG. 4A. It is a partially enlarged view of the negative electrode current collector shown in FIG. 4A.

Hereinafter, embodiments of the present disclosure will be described. In the following description, the embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, 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 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 arranged on the current collector. The current collector contains a plurality of repeating units in a row. An active material layer is arranged on each of the plurality of repeating units. Each of the multiple repeating units is a substantially circular or substantially polygonal. In the battery, the current collector is bent with the boundary between two adjacent repeating units as a bent portion. That is, the electrode plate is bent with the boundary portion as a bending portion.

When the electrode plate is a positive electrode plate, the current collector, the repeating unit, the boundary portion, and the active material layer can be read as the 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 can be read as the negative electrode current collector, the repeating unit B, the boundary portion Y, and the 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 the coin-shaped secondary battery described later is an example of the electrode plate of the present disclosure. Therefore, the configuration of the positive electrode plate and / or the negative electrode plate of the coin-shaped secondary battery described later can be applied as the configuration 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 the secondary battery in which the electrode plate is used and the type of the electrode plate (positive electrode plate, negative electrode plate). As the material of the current collector and the active material layer, a known material of the current collector and the active material may be used. Examples of the current collector and the active material layer will be described later.

Of the outer edges of the current collector, the outer edge of the boundary between two adjacent repeating units may be referred to as "outer edge (P)" below. The outer edge (P) may have the following characteristics (1).
(1) The outer edge (P) has a convex shape toward the inside of the boundary portion (in another viewpoint, the center of the boundary portion).

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 of (1) above. The outer edge (P) may have any one of the features (2) to (6) in addition to the feature of the above (1). For example, the outer edge (P) may have the above-mentioned feature (1) and the following feature (2).
(2) The outer edge (P) is composed of smooth lines.
(3) The outer edge (P) has no corners.
(4) The outer edge (P) is rounded.
(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.
(6) The outer edge (P) has a shape with rounded corners composed of two straight lines. Here, the two straight lines are the two sides of the two polygons when the two polygons are joined so as to share the two vertices. The two sides are two unshared sides having one shared vertex as an end point. These will be specifically described in the first embodiment described later.

In the electrode plate of the present disclosure, the boundary portion of the repeating unit is bent when the electrode group is produced. Therefore, a force (tension, etc.) is applied to the boundary portion when the electrode group is manufactured. When a corner portion is present on the outer edge (P) of the boundary portion, the force is concentrated on the corner portion and the current collector is likely to break. Since the current collector including the outer edge (P) having the above-mentioned characteristics does not have a portion at the boundary where the force is particularly likely to be concentrated, breakage or the like is unlikely to occur even when the electrode group is produced. Therefore, the electrode group and the secondary battery can be manufactured with a high yield. Further, by using the electrode plate of the present disclosure, a highly reliable secondary battery can be obtained.

Each of the plurality of repeating units is a substantially circular shape or a substantially polygonal shape. An example of a substantially circular shape is a shape formed by two equal arc-shaped curves arranged line-symmetrically and point-symmetrically so as to be convex outward, and two straight lines connecting the curves. be. An example of such a shape is a shape obtained by cutting a circle (or ellipse) with two parallel lines having the same distance from the center of the circle (or ellipse). In the case of an ellipse, the two parallel lines are parallel to the major or minor axis of the ellipse.

An example of a substantially polygonal shape includes a polygonal portion (polygonal portion) and a portion that fills a region between the polygonal portion and the outer edge (P). The portion that fills the area between the polygon and the outer edge (P) may be referred to as a "rounded portion" below. The number of sides forming the polygonal portion may be in the range of 6 to 12. For example, the polygonal portion may be a hexagon (for example, a regular hexagon), an octagon (for example, a regular octagon), or a decagon (for example, a regular decagon). That is, the repeating unit may be a substantially octagon or a substantially decagon.

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

From one point of view, the shape of the repeating unit may be the following shape. That is, when the innermost diameter of the coin-shaped case in which the electrode plate is arranged is F, the first circle having a diameter of F and the second circle having a diameter of 0.4F and concentric with the first circle. Think of. At this time, the shape of the repeating unit is such that all the outer edges of the repeating unit are regions between the first circle and the second circle (specifically, the circumference of the first circle and the circle of the second circle). It may have a shape that fits in the area between the circumference and the circumference. In one example in this case, the diameter of the second circle may be 0.5F. The innermost diameter F of the case 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).

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 and the shape of the repeating unit B are different, both the outer edge of the repeating unit A and the outer edge of the repeating unit B are in the region between the first circle and the second circle. You may.

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 FIG. 4C) may be larger or smaller than the width WA of the repeating unit A (see FIG. 3C). Further, the length LB of the repeating unit B (see FIG. 4C) may be longer or shorter than the length LA of the repeating unit A (see FIG. 3C). In one example, the area of the repeating unit B is larger than the area of the repeating unit A.

A current collector containing a plurality of repeating units can be composed of one metal sheet. The active material layers arranged on the plurality of repeating units may or may not be connected. For example, the active material layer may not be formed at 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). good.

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 of the plurality of repeating units. The plurality of repeating units and connecting portions can be composed of one metal sheet.

The plurality of repeating units has a shape in which a plurality of polygons are arranged in a row so that two adjacent polygons share two vertices, and the corners of the outer edges of the two vertices are rounded. May be good.

(Coin-type 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 arranged in the case. The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer arranged on the positive electrode current collector. The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer arranged 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”) in a row. The negative electrode current collector includes a plurality of repeating units (hereinafter, may be referred to as “repeating unit B”) in a row. A positive electrode active material layer is arranged on each of the plurality of repeating units A. A negative electrode active material layer is arranged on each of 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 and the negative electrode active material layer face each other.

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 with the boundary portion of two adjacent repeating units A (hereinafter sometimes referred to as "boundary portion X") as a bent portion. The negative electrode current collector is bent with the boundary portion of two adjacent repeating units B (hereinafter, may be referred to as “boundary portion Y”) as a bent portion.

The positive electrode plate and the negative electrode plate are obtained by bending the electrode plate of the present disclosure described above at a boundary portion. Therefore, duplicate explanations may be omitted.

When the current collector (positive electrode current collector, negative electrode current collector) is deployed flat, the boundary portion (boundary portion) of two adjacent repeating units (repeating unit A and repeating unit B) on the outer edge of the current collector. The outer edge (P) of X, the boundary portion Y) has the above-mentioned shape. Further, each of the repeating units (repeating unit A and repeating unit B) is a substantially circular shape or a substantially polygonal shape as described above.

When the positive electrode plate is developed flat, the outer edge of the boundary portion X among the outer edges of the positive electrode plate may have a convex shape toward the inside of the boundary portion X and may be composed of smooth lines. .. When the negative electrode plate is unfolded flat, the outer edge of the boundary portion Y among the outer edges of the negative electrode plate may have a convex shape toward the inside of the boundary portion Y and may be composed of smooth lines. ..

When the positive electrode current collector is unfolded flat, the plurality of repeating units A form a row of the plurality of first polygons so that the two adjacent first polygons share two vertices. Further, it may have a shape in which the corners of the outer edges at the two vertices are rounded. When the negative electrode current collector is unfolded flat, the plurality of repeating units B form a row of a plurality of second polygons so that two adjacent second polygons share two vertices. Further, it may have a shape in which the corners of the outer edges at the two vertices are rounded. The number of sides of the first polygon may 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).

The outer edge (outer edge (P)) of the boundary portion X and the outer edge (outer edge (P)) of the boundary portion Y may be rounded by a curve (for example, an arc) having a radius of curvature R, respectively. For example, the corner portion of the outer edge (P) may be rounded by a curve (for example, an arc) having a radius of curvature R. The radius of curvature of the curve that rounds the outer edge does not have to be constant.

The radius of curvature R may be 0.1 mm or more, 0.3 mm or more, or 1 mm or more. The radius of curvature R may be 2.5 mm or less, or 2 mm or less. The radius of curvature R may be in the range of 0.1 to 2.5 mm (for example, in the range of 0.3 to 2.0 mm). By rounding the outer edge (P) with a curve having a radius of curvature R of 0.3 mm or more, damage to the current collector when forming the electrode group can be particularly reduced. By rounding the outer edge (P) with a curve having a radius of curvature R of 2.0 mm or less, it becomes easy to bend the electrode plate when producing the electrode group.

A plurality of polygons having a side length of S (mm) are arranged in a row so that two adjacent polygons share two vertices, and the corners of the outer edge of the two vertices are curved. Consider the case of rounding with a curve having a radius R (mm) (see FIG. 3C). In this case, the length S and the radius of curvature R may satisfy the formula of 0.04S ≦ R ≦ S or 0.12S ≦ R ≦ 0.8S.

The secondary battery of the present disclosure may include a separator arranged between the positive electrode plate and the negative electrode plate. Further, the secondary battery of the present disclosure may further include a separator arranged between the positive electrode plate and the negative electrode plate, and a non-aqueous electrolyte arranged in the case. That is, the secondary battery of the present disclosure may be a non-aqueous electrolyte secondary battery.

The positive electrode plate and the negative electrode plate may be bent or wound in a zigzag manner, respectively. In these cases, a separator may be arranged 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 may be fixed to the positive electrode active material layer. By fixing the separator to the active material layer, the battery can be easily manufactured. The method for fixing the separator is not particularly limited, and a known technique may be used. For example, the separator may be fixed to the active material layer by a hot press or the like. Alternatively, a separator having an adhesive layer on the surface may be used. As the adhesive layer, for example, a layer containing a resin such as polyvinylidene fluoride can be used.

When the positive electrode plate and the negative electrode plate are each bent in a zigzag pattern, the positive electrode active material layer may be arranged on only one side of the positive electrode current collector, and / or the negative electrode active material layer is the negative electrode current collector. It may be placed on only one side of the body.

The secondary battery of the present disclosure may include at least one positive electrode plate and at least one negative electrode plate so that the total number of the number of positive electrode plates and the number of negative electrode plates is 2 or 3. Three examples (first to third arrangement examples) regarding the number of positive electrode plates and negative electrode plates and the arrangement of the active material layer will be described below.

In the first arrangement example, the number of positive electrode plates and the number of negative electrode plates are 1, respectively. In this case, the positive electrode active material layer is arranged only on one side of the positive electrode current collector, and the negative electrode active material layer is arranged only on one side of the negative electrode current collector. In the second arrangement example, the number of positive electrode plates is 2 and the number of negative electrode plates is 1. In this case, the positive electrode active material layer is arranged on only one side of the positive electrode current collector, and the negative electrode active material layer is arranged on both sides of the negative electrode current collector. In the second arrangement example, the positive electrode plate and the negative electrode plate are arranged so as to sandwich one negative electrode plate between the two positive electrode plates. In the third arrangement example, the number of negative electrode plates is 2, and the number of positive electrode plates is 1. In this case, the positive electrode active material layer is arranged on both sides of the positive electrode current collector, and the negative electrode active material layer is arranged on only one side of the negative electrode current collector. In the third arrangement example, the positive electrode plate and the negative electrode plate are arranged so as to sandwich one positive electrode plate between the two negative electrode plates.

When the positive electrode plate and the negative electrode plate are wound respectively, the positive electrode active material layers may be arranged on both sides of the positive electrode current collector, and the negative electrode active material layers are arranged on both sides of the negative electrode current collector. You may.

The type of the secondary battery disclosed in the present disclosure 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.

Except for using the configurations specific to the present disclosure, there are no particular restrictions on the components of the secondary battery of the present disclosure (cases, materials constituting the positive electrode plate, materials constituting the negative electrode plate, and other components, etc.). No. A known material or a known configuration may be applied to the components of the secondary battery of the present disclosure, except that the configuration peculiar to the present disclosure is used. The components of the case where the secondary battery of the present disclosure is a lithium ion secondary battery are illustrated below, but the present disclosure is not limited to the following examples.

(Positive plate)
Examples of positive electrode current collectors include sheet-like objects (eg, foils, meshes, or punching sheets) made of conductive materials (eg, metal materials). Examples of metal materials constituting the positive electrode current collector include aluminum, aluminum alloys, titanium, titanium alloys, stainless steel and the like. The thickness of the positive electrode current collector may be in the range of, for example, 5 to 300 μm.

The positive electrode active material layer contains a positive electrode active material, and may contain other substances (binding agent, conductive agent, etc.) if necessary. Examples of positive electrode active materials include substances that reversibly occlude and release lithium ions. Specifically, examples of the positive electrode active material include a metal oxide containing lithium, a lithium-transition metal phosphoric acid compound, a lithium-transition metal sulfate compound, and the like. Examples of lithium-containing metal oxides include lithium transition metal composite oxides, lithium-nickel-cobalt-aluminum composite oxides and the like. Examples of lithium transition metal composite oxides include lithium-manganese composite oxides (eg LiMn ₂ O ₄ ), lithium-nickel composite oxides (eg LiNiO ₂ ), lithium-cobalt composite oxides (eg LiCoO ₂ ), and , Composite oxides in which some of these transition metal elements are replaced with other metal elements (typical metal elements and / or transition metal elements) are included.

Examples of binders include fluororesins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubbery polymers. Examples of fluororesins include polytetrafluoroethylene, polyvinylidene fluoride and the like. As the binder, only one kind may be used, or two or more kinds may be used.

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. As the conductive agent, only one kind may be used, or two or more kinds may be used.

(Negative electrode 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 form a connection portion electrically connected to a part of the case (case body or sealing plate) that functions as a terminal. In that case, the connection is connected to a part of the case by welding (eg ultrasonic welding) or the like.

Examples of the negative electrode current collector include a sheet-like material (for example, foil, mesh, or punching sheet) made of a conductive material (for example, a metal material). The metal material of the negative electrode current collector may be a material that does not form lithium and neither an alloy nor an intermetallic compound. Examples of metallic materials for negative electrode current collectors include copper, nickel, iron, and alloys containing these metallic 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 in the range of, for example, 5 to 300 μm.

The negative electrode active material layer contains a negative electrode active material, and may contain other substances (binding agent, conductive agent, thickener, etc.) if necessary. Examples of negative electrode active materials include substances that reversibly occlude and release lithium ions. Specifically, examples of the negative electrode active material include carbon materials, silicon, silicon compounds, lithium alloys, and the like. Examples of carbon materials include graphite, coke, graphitized carbon, graphitized carbon fibers, amorphous carbon and the like.

Examples of binders include fluororesins such as polyvinylidene fluoride (PVDF), acrylic resins such as methyl polyacrylate and ethylene-methyl methacrylate copolymer, styrene butadiene rubber, acrylic rubber, and rubbers thereof. Includes denatured products. Examples of the conductive agent include the conductive agent exemplified in the description of the positive electrode active material layer. Examples of thickeners include water-soluble polymers containing carboxyl groups (eg, carboxymethyl cellulose).

(Separator)
Examples of separators include sheets that are ion permeable and insulating. The separator may be a laminate of a plurality of sheets including a sheet having ion permeability and insulating property. The separator has a size required to insulate the positive electrode plate and the negative electrode plate.

The separator may be a microporous film, a woven fabric, or a non-woven fabric. Examples of the material of the separator include a polymer having an insulating property, and specifically, a polyolefin-based polymer, a polyamide-based polymer, a cellulose-based polymer, and the like. The thickness of the separator may be in the range of 5 to 200 μm.

(Non-aqueous electrolyte)
As the non-aqueous electrolyte, one having lithium ion conductivity is used. A typical non-aqueous electrolyte contains a non-aqueous solvent and lithium ions and anions dissolved in the non-aqueous solvent. The non-aqueous electrolyte may be in the form of a liquid or in the form of a gel. The liquid non-aqueous electrolyte can be prepared by dissolving the lithium salt in a non-aqueous solvent. Lithium ions and anions are produced by dissolving lithium salts (salts of lithium ions and anions) in non-aqueous solvents.

The gel-like non-aqueous electrolyte contains a liquid non-aqueous electrolyte and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of such polymeric materials include fluororesins, acrylic resins, polyether resins and the like.

Examples of the anion of the lithium _{^{_{^{_{^{salt, BF 4 -, ClO 4 -}}}}}} , PF 6 -, CF 3 SO 3 -, CF 3 CO 2 -, anions of imides, and the like anions of oxalate complexes.

Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and halogen substituents (eg, fluorides) thereof. The non-aqueous electrolyte may contain only one of these non-aqueous solvents, or may contain two or more of these non-aqueous solvents.

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

The concentration of the lithium salt in the non-aqueous electrolyte may 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 anions in the non-aqueous electrolyte may be in the range of 0.5 mol / 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. Normally, the case body and the sealing plate each function as electrode terminals. For example, in the case of a general coin-shaped battery, the case 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 each be formed of metal (for example, conductive stainless steel).

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

(Embodiment 1)
A cross-sectional view of the coin-shaped secondary battery of the first embodiment is schematically shown in FIG. The secondary battery 10 of FIG. 1 includes a coin-shaped case 20, an electrode group 30 arranged in the case 20, and a non-aqueous electrolyte (not shown). 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 a sealing plate 22 and a gasket 23.

A cross-sectional view of the electrode group 30 is shown in FIG. FIG. 2 is a cross section along a direction in which the repeating unit 41A and the repeating unit 51B (see FIGS. 3A and 4A) are continuous in a zigzag manner. The electrode group 30 includes a positive electrode plate 40, a negative electrode plate 50, and one separator 60 arranged between them. The positive electrode plate 40, the negative electrode plate 50, and the separator 60 are each bent in a zigzag pattern. The positive electrode active material layer 42 and the negative electrode active material layer 52 face each other with the separator 60 interposed therebetween.

(Positive plate)
A plan view of the positive electrode plate 40 when it is unfolded flat is shown in FIG. 3A, and a cross-sectional view taken along the line IIIB-IIIB of FIG. 3A is shown in FIG. 3B. Further, a partially enlarged view of the positive electrode current collector 41 is shown in FIG. 3C. The positive electrode plate 40 includes a positive electrode current collector 41 and a positive electrode active material layer 42 arranged on the positive electrode current collector 41.

The positive electrode current collector 41 includes a plurality of repeating units 41A connected in a row. 3A and 3C show the boundary 41k of two adjacent 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 repeating unit 41A. The positive electrode active material layer 42 arranged on each of the plurality of repeating units 41A is connected. In the electrode group 30, the positive electrode current collector 41 and the positive electrode plate 40 are bent with all of the boundary portions 41X (peripheral portions of the boundary 41k) of the two adjacent repeating units 41A as bending portions.

The connecting portion 43 is connected to the repeating unit 41A at one end. In the illustrated example, the connecting portion 43 has substantially the same shape as one repeating unit 41A. The connecting 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 arranged on the connecting portion 43. The structure of the connecting portion 43 is not particularly limited as long as the positive electrode current collector 41 can be electrically connected to the case body 21. As shown in FIG. 2, the boundary portion between the connecting portion 43 and the repeating unit 41A is also bent as a bent portion.

With reference to FIG. 3C, one repeating unit 41A includes an octagonal octagonal portion 41Aa and a rounded portion 41Ab. In FIG. 3C, the rounded portion 41Ab is hatched. The shape formed by the plurality of repeating units 41A is such that a plurality of octagonal portions 41Aa are arranged in a row so that two adjacent octagonal portions 41Aa share two vertices, and further, the outer edge of the two vertices is connected. It has a shape with rounded corners. The portion where the corner portion is rounded becomes the rounded portion 41Ab. In the example shown in FIG. 3C, the corners are rounded by a curve (arc) having a radius of curvature R.

When the positive electrode current collector 41 is deployed flat, the outer edge of the boundary portion 41X (bent portion) has a convex shape toward the inside of the boundary portion 41X and is composed of smooth lines. There are no corners on the outer edge of the boundary 41X. The tangent vector of the outer edge of the boundary portion 41X is not discontinuous and changes continuously. A part of the outer edge of the boundary portion 41X may be a straight line.

(Negative electrode plate)
A plan view of the negative electrode plate 50 when unfolded flat is shown in FIG. 4A, and a cross-sectional view taken along the line IVB-IVB of FIG. 4A is shown in FIG. 4B. Further, a partially enlarged view of the negative electrode current collector 51 is shown in FIG. 4C. The negative electrode plate 50 includes a negative electrode current collector 51 and a negative electrode active material layer 52 arranged on the negative electrode current collector 51.

The negative electrode current collector 51 includes a plurality of repeating units 51B connected in a row. 4A and 4C show the boundary 51k of two adjacent repeating units 51B. The plurality of 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 layer 52 arranged on each of the plurality of repeating units 51B is connected. In the electrode group 30, the negative electrode current collector 51 and the negative electrode plate 50 are bent with all of the boundary portions 51Y (peripheral portions of the boundary 51k) of the two adjacent repeating units 51B as bent portions.

A connection portion 53 is connected to the repeating unit 51B at one end. In the illustrated example, the connecting portion 53 has substantially the same shape as 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 or the like, for example. The negative electrode active material layer 52 is not arranged on the connecting portion 53. The structure of the connecting 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 portion between the connecting portion 53 and the repeating unit 51B is also bent as a bent portion.

With reference 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 description of the shape of the repeating unit 51B will be omitted.

The positive electrode current collector 41 and the negative electrode current collector 51 are composed of lines having smooth outer edges of boundary portions X and Y which are bent portions. Therefore, even when stress is applied to the boundary portions X and Y when forming the electrode group 30, it is possible to prevent the boundary portions X and Y from being damaged. On the other hand, when a corner portion is present on the outer edge, stress may be concentrated on the corner portion and the current collector may be easily damaged.

If the positive electrode plate 40 and / or the negative electrode plate 50 comes into contact with the case 20, a short circuit may occur. An insulating member (for example, insulating tape) for preventing such a short circuit may be arranged around the electrode group 30.

In the first embodiment, the case where each of the positive electrode plate, the negative electrode plate, and the separator constituting the electrode group is only one has been described. However, one of the positive electrode plate and the negative electrode plate may be only one, and the other may be two. In that case, the active material layer may be formed on both sides of only one electrode plate, and the active material layer may be formed on one side of each of the other two electrode plates. In that case, two separators may be used. When there is only one positive electrode plate and two negative electrode plates, one positive electrode plate, two negative electrode plates, and two separators are a negative electrode current collector / negative electrode active material layer / separator / positive electrode active material. The layers may be arranged in the order of layer / positive electrode current collector / positive electrode active material layer / separator / negative electrode active material layer / negative electrode current collector, and may be folded in a zigzag manner. Similarly, when there is only one negative electrode plate and two positive electrode plates, the two positive electrode plates, one negative electrode plate, and the two separators are the positive electrode current collector / positive electrode active material layer / separator /. The negative electrode active material layer / negative electrode current collector / negative electrode active material layer / separator / positive electrode active material layer / positive electrode current collector may be arranged in this order and may be folded in a zigzag manner. When active material layers are formed on both sides of a positive electrode plate (or a negative electrode plate), one repeating unit A (or one repeating unit B) is a positive electrode current collector (or a negative electrode current collector) and both surfaces thereof. Includes the arranged positive electrode active material layer (or negative electrode active material layer).

(Manufacturing method of coin-shaped secondary battery)
An example of the method for manufacturing the secondary battery of the present embodiment will be described. Hereinafter, an example of the method for manufacturing the secondary battery 10 described in the first embodiment will be described. Known techniques can be applied to the manufacturing process described below. The method for manufacturing the secondary battery of 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 an example of the 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 onto a conductive sheet (for example, a metal foil) to be the positive electrode current collector 41 to form the positive electrode active material layer 42. In this way, the positive electrode plate 40 is manufactured. The positive electrode plate 40 and the positive electrode current collector 41 are manufactured so as to have the above-mentioned structure (planar shape). Even if the positive electrode plate 40 is 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. good.

In an example of the 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 onto 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. In this way, the negative electrode plate 50 is manufactured. The negative electrode plate 50 and the negative electrode current collector 51 are manufactured so as to have the above-mentioned structure (planar shape). Even if the negative electrode plate 50 is manufactured by forming the negative electrode active material layer 52 in a predetermined region of the large-area conductive sheet and then punching the conductive sheet and the negative electrode active material layer 52 together using a punching die. good.

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 face each other with the separator 60 interposed therebetween. Then, they are bent together in a zigzag manner to prepare an electrode group 30. The positive electrode plate 40, the negative electrode plate 50, and the separator 60 may be bent and then combined to form the electrode group 30. Further, 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 plate is bent. By fixing the separator, it becomes easy to manufacture the electrode group. The separator can be fixed by the method described above.

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

Next, the electrode group 30 and the non-aqueous electrolyte are placed in the fitting body of the sealing plate 22 and the gasket 23. Next, the case body 21 is arranged so as to seal the opening of the fitting body, and then the opening end of the case body 21 is crimped to seal the case body 21. In this way, the secondary battery 10 of the first embodiment is obtained.

When the electrode group 30 is a winding type electrode group, first, the positive electrode plate 40, the negative electrode plate 50, and the separator 60 are arranged so that the separator 60 is arranged between the positive electrode plate 40 and the negative electrode plate 50. And are wound together to make a wound body. After that, the winding body is crushed so as to have a flat shape. At this time, the winding body is crushed so that the boundary portion (rounded portion) of the repeating unit becomes a flat bent portion. In this way, the winding type electrode group 30 can be produced.

The present disclosure will be described in more detail by way of examples. In this example, a secondary battery having a structure similar to that of 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) was a substantially 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 (see FIG. 3C) are 6 mm, respectively. The positive electrode current collector has a shape in which 15 regular octagons are connected in a row and the corners of the outer edge of the boundary between two adjacent regular octagons are rounded. Specifically, the corner portion was rounded with a curve having a radius of curvature R of 1.0 mm. The number of repeating units B (corresponding to the repeating unit 51B in FIG. 4A) of the negative electrode current collector was the same as the number of repeating units A. The length LB of the repeating unit B in the direction ND (see FIG. 4C) was the same as the length LA. Further, the width WB perpendicular to the direction ND was made slightly larger than the width WA.

The positive electrode mixture constituting the positive electrode active material layer consists of lithium cobalt oxide (LiCoO ₂ ), which is a positive electrode active material, acetylene black, which is a conductive agent, and vinylidene polyfluoride, which is a binder, and lithium cobalt oxide: acetylene. It was prepared by mixing with a mass ratio of black: polyvinylidene fluoride = 9: 0.1: 0.1. Aluminum foil was used for the positive electrode current collector. By applying a positive electrode mixture on one side of the positive electrode current collector, a positive electrode active material layer having a thickness of 55 μm was formed. Of the 15 regular octagonal parts, the active material layer was not arranged in two parts at one end, and the connecting part was used for welding. That is, the number of repeating units A in which the positive electrode active material layer was arranged was 13.

The negative electrode mixture constituting the negative electrode active material layer is composed of graphite, which is a negative electrode active material, carboxymethyl cellulose (CMC), which is a thickener, and styrene-butadiene rubber (SBR), which is a binder. Prepared by mixing with a mass ratio of SBR = 9: 0.1: 0.1. A copper foil was used for the negative electrode current collector.

A microporous polyolefin membrane (thickness 14 μm) was used as the separator. The non-aqueous electrolyte was prepared by dissolving _{LiPF 6 in a non-aqueous solvent.} The non-aqueous solvent was prepared by mixing ethylene carbonate, propylene carbonate, and methyl ethyl carbonate in a volume ratio of ethylene carbonate: propylene carbonate: methyl ethyl carbonate = 30: 1: 61.

A positive electrode plate and a negative electrode plate were produced using the above materials. Then, an electrode group (see FIG. 2) in which the positive electrode plate, the negative electrode plate, and the separator were bent in a zigzag pattern was produced. Next, using the electrode group, the non-aqueous electrolyte, and the coin-shaped case, a coin-shaped non-aqueous electrolyte secondary battery was produced by the method described above. The size of the obtained secondary battery was 9.5 mm in outer diameter and 2.0 mm in height. The innermost diameter of the case was 7.5 mm.

(Batteries A2 to A6)
The batteries A2 to A6 were manufactured under the same conditions as the batteries A1 except that the shape of the boundary between the two adjacent repeating units A was changed. Specifically, the curvature of the curve obtained by rounding the corners of the outer edge of the boundary portion was changed in the range of 0.1 to 2.5 mm. The curvatures used in each battery are shown in Table 1 below.

(Battery C1)
Battery C1 was manufactured under the same conditions as battery A1 except that the outer edge of the boundary between two adjacent regular octagons was not rounded.

(Yield evaluation during electrode group fabrication)
Ten electrode groups of the above batteries A1 to A6 and C1 were prepared. Then, the energized states of the positive electrode current collector and the negative electrode current collector were confirmed, and it was evaluated whether or not the current collector was cut off. That is, if energization was not possible, it was determined to be a defective product. If it can be energized, it is judged to be a good product. Then, the yield (%) was calculated from the number of produced electrode groups and the number of non-defective products. The yield is expressed by the following formula.
Yield (%) = 100 x (number of non-defective products) / (number of products manufactured)
(Charge / discharge test)
A charge / discharge cycle test was performed on the above batteries A1 to A6 and C1. The charging step was performed by charging the battery with 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 step was performed by discharging until the battery voltage became 3.0 V at a current value of 6 mA. The charging / discharging cycle was repeated, with the charging / discharging cycle consisting of one charging step and one discharging step as one cycle. Then, the number of charge / discharge cycles n until the battery capacity became 80% of the initial battery capacity was evaluated. For batteries (batteries A3, A1, A4, A5, A6) whose battery capacity is larger than 80% of the initial battery capacity after 1000 cycles, the number of charge / discharge cycles n in Table 1 is set to 1000. The evaluation results are shown in Table 1.

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

This disclosure can be used for electrode plates and coin-type secondary batteries.

10: Secondary battery 20: Case 40: Positive electrode plate 41: Positive electrode

current collector

41A, 51B: Repeating unit 41Aa, 51Ba: Octagonal part (polygonal part)
41Ab, 51Bb:

Rounded portion

41k, 51k:

Boundary

41X, 51Y: Boundary 42: Positive electrode active material layer 50: Negative electrode plate 51: Negative electrode current collector 52: Negative electrode active material layer 60: Separator

Claims

A plate containing a current collector and an active material layer arranged on the current collector.
The current collector contains a plurality of repeating units in a row.
The active material layer is arranged on each of the plurality of repeating units.
The outer edge of the boundary portion of the two adjacent repeating units of the outer edge of the current collector has a convex shape toward the inside of the boundary portion and is composed of smooth lines.
An electrode plate in which each of the plurality of repeating units is substantially circular or substantially polygonal.
The plurality of repeating units have a shape in which a plurality of polygons are arranged in a row so that two adjacent polygons share two vertices, and the corners of the outer edges of the two vertices are rounded. The electrode plate according to claim 1.
A coin-shaped secondary battery including a coin-shaped case and a positive electrode plate and a negative electrode plate arranged in the case.
The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer arranged on the positive electrode current collector.
The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer arranged on the negative electrode current collector.
The positive electrode current collector includes a plurality of repeating units A connected in a row, and includes a plurality of repeating units A.
The negative electrode current collector includes a plurality of repeating units B connected in a row, and includes a plurality of repeating units B.
The positive electrode active material layer is arranged on each of the plurality of repeating units A.
The negative electrode active material layer is arranged on each of the plurality of repeating units B, and the negative electrode active material layer is arranged.
The positive electrode plate and the negative electrode plate are arranged so that the positive electrode active material layer and the negative electrode active material layer face each other.
The positive electrode current collector is bent with the boundary portion X of the two adjacent repeating units A as a bent portion.
The negative electrode current collector is bent with the boundary portion Y of the two adjacent repeating units B as a bent portion.
When the positive electrode current collector is deployed flat, the outer edge of the boundary portion X among the outer edges of the positive electrode current collector has a convex shape toward the inside of the boundary portion X and is smooth. Consists of lines
When the negative electrode current collector is deployed flat, the outer edge of the boundary portion Y of the outer edges of the negative electrode current collector has a convex shape toward the inside of the boundary portion Y and is smooth. Consists of lines
A coin-shaped secondary battery in which each of the plurality of repeating units A and the plurality of repeating units B is substantially circular or substantially polygonal.
When the positive electrode current collector is deployed flat, the plurality of repeating units A form a row of a plurality of first polygons so that two adjacent first polygons share two vertices. Further, it has a shape in which the corners of the outer edges at the two vertices are rounded.
When the negative electrode current collector is deployed flat, the plurality of repeating units B form a row of a plurality of second polygons so that two adjacent second polygons share two vertices. Further, it has a shape in which the corners of the outer edges at the two vertices are rounded.
The coin-shaped secondary battery according to claim 3, wherein the number of sides of the first polygon and the number of sides of the second polygon are the same.
The coin-shaped secondary battery according to claim 3 or 4, wherein the outer edge of the boundary portion X and the outer edge of the boundary portion Y are each rounded with a curve having a radius of curvature in the range of 0.3 to 2.0 mm. ..
The coin-type secondary battery according to any one of claims 3 to 5, further comprising a separator arranged between the positive electrode plate and the negative electrode plate, and a non-aqueous electrolyte arranged in the case. ..
The coin-shaped secondary battery according to any one of claims 3 to 6, wherein the positive electrode plate and the negative electrode plate are each bent or wound in a zigzag manner.
The positive electrode plate and the negative electrode plate are each bent in a zigzag manner.
The positive electrode active material layer is arranged only on one side of the positive electrode current collector, and / or the negative electrode active material layer is arranged only on one side of the negative electrode current collector, claim 3 to 6. The coin-shaped secondary battery according to any one of the items.