Secondary battery

Abstract

To immerse the inside of an electrode with an electrolyte and secure the strength of a separator at the same time.SOLUTION: A separator 170 includes: a first region R1 including a first end part 171 and a second end part 172 facing each other in a first direction perpendicular to the thickness direction; and a second region R2 between the first regions R1 in a first direction, the second region including a center part 173 of the separator 170. In the surface of the separator 170, there is a recessed part 174 arranged at least in the first region R1, the recessed part being capable of receiving inflow of an electrolyte. The cross section of the recessed part 174 in the first region R1 of the separator 170 viewed from the first direction is larger than the cross section of the recessed part 174 in the second region R2 of the separator 170.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present technology relates to a secondary battery. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2014-203668 (Patent Document 1) is a prior art document that discloses the configuration of a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery described in Patent Document 1 includes a negative electrode current collector, a negative electrode active material composite part, and a separator. The negative electrode current collector is a metal film. A plurality of negative electrode active material composite parts are formed and protrude from the negative electrode current collector toward the separator.

[0003] Japanese Patent Laid-Open Publication No. 2012-243567 (Patent Document 2) is a prior art document that discloses the configuration of a lithium-ion battery. The lithium-ion battery described in Patent Document 2 includes a wound electrode group. The wound electrode group is wound with a separator sandwiched between a positive electrode and a negative electrode. The positive electrode and the negative electrode have uneven surfaces that mesh with each other with the separator sandwiched between them. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-203668 A [Patent Document 2] JP 2012-243567 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the secondary batteries described in Patent Documents 1 and 2, although the strength of the separator in the electrode assembly is ensured, there is a possibility that a gap for the electrolyte to penetrate between the separator and the positive or negative electrode plate cannot be ensured due to the expansion of the negative electrode active material, etc. For this reason, it is difficult to simultaneously ensure the strength of the separator and the electrolyte that is discharged from the electrode assembly to the outside during charging, etc., to penetrate into the electrode assembly.

[0006] The present technology has been made to solve the above-mentioned problems, and aims to provide a secondary battery that can achieve both the impregnation of an electrolyte into the inside of an electrode body and the securing of the strength of the separator. [Means for solving the problem]

[0007] The present technology provides the following secondary battery. [1] A flat electrode assembly including a positive electrode plate, a separator, and a negative electrode plate, the separator being disposed between the positive electrode plate and the negative electrode plate; A case is provided to accommodate the electrode assembly and an electrolyte solution, When viewed from the thickness direction of the electrode body, the separator includes a first region including a first end and a second end that face each other in a first direction perpendicular to the thickness direction, and a second region that is sandwiched between the first regions in the first direction and includes a central portion of the separator, a recessed portion is provided on a surface of the separator, the recessed portion being disposed at least in the first region and into which the electrolytic solution can flow; a cross-sectional area of ​​the recess in the first region of the separator is larger than a cross-sectional area of ​​the recess in the second region of the separator when viewed from the first direction. [2] The secondary battery according to [1], wherein, when viewed in the thickness direction, an area occupied by the recesses in the first region of the separator is larger than an area occupied by the recesses in the second region of the separator. [3] The secondary battery according to [1] or [2], wherein the electrode body has a rectangular shape including a longitudinal direction and a lateral direction when viewed from the thickness direction, and the first direction is the longitudinal direction of the electrode body. [4] The secondary battery described in any one of [1] to [3], wherein the recess includes a groove portion extending along the first direction and reaching from the first end to the second end of the separator. [5] The secondary battery according to [4], wherein an average depth of the recesses in the first region of the separator is greater than an average depth of the recesses in the second region of the separator. [6] The secondary battery according to any one of [1] to [3], wherein the recess includes a plurality of holes aligned in the first direction. [7] The secondary battery according to any one of [1] to [6], wherein the electrode body is a wound electrode body in which the positive electrode plate, the separator and the negative electrode plate are wound around an axis in the first direction. Effect of the Invention

[0008] According to the present technology, it is possible to achieve both impregnation of the electrolyte into the electrode assembly and ensuring the strength of the separator. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a configuration of a secondary battery according to a first embodiment of the present technology. [Diagram 2] 1 is a perspective view showing a configuration of an electrode body according to a first embodiment of the present technology. [Diagram 3] 2 is a schematic diagram showing a flow of an electrolyte in a secondary battery according to a first embodiment of the present technology. FIG. [Figure 4] 1 is a plan view showing a configuration of a separator included in an electrode assembly of a secondary battery according to a first embodiment of the present technology. [Diagram 5] 5 is a partial cross-sectional view of the secondary battery of FIG. 4, as viewed from the direction of the VV line arrow. [Figure 6]6 is a partial cross-sectional view of the secondary battery of FIG. 4, taken along the line VI-VI. [Figure 7] 1 is a partial cross-sectional view showing a configuration of a separator included in an electrode assembly of a secondary battery according to a first modified example of embodiment 1 of the present technology. FIG. [Figure 8] 11 is a partial cross-sectional view showing a configuration of a separator included in an electrode assembly of a secondary battery according to a second modified example of the first embodiment of the present technology. FIG. [Figure 9] 1 is a graph showing discharge characteristics of a secondary battery in terms of the relationship between discharge time and voltage of the secondary battery according to the first embodiment of the present technology and a comparative example. [Figure 10] 1 is a graph showing the relationship between the number of charge / discharge cycles and the degree of battery capacity deterioration of secondary batteries according to the first embodiment of the present technology and a comparative example. [Figure 11] 11 is a plan view showing a configuration of a separator included in an electrode body of a secondary battery according to embodiment 2 of the present technology. FIG. [Figure 12] 11 is a plan view showing a configuration of a separator included in an electrode body of a secondary battery according to embodiment 3 of the present technology. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present technology will be described. Note that the same or corresponding parts are denoted by the same reference characters, and description thereof will not be repeated.

[0011] In the embodiments described below, when referring to the number, amount, etc., the scope of the present technology is not necessarily limited to the number, amount, etc., unless otherwise specified. In addition, in the following embodiments, each component is not necessarily essential to the present technology, unless otherwise specified. In addition, the present technology is not necessarily limited to those that achieve all of the effects and advantages mentioned in the present embodiment.

[0012] In this specification, the words "comprise", "include" and "have" are open-ended, i.e., when a certain configuration is included, other configurations may or may not be included.

[0013] Furthermore, when geometric terms and terms expressing positional and directional relationships, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along" are used in this specification, these terms allow for manufacturing errors and slight variations. When terms expressing relative positional relationships, such as "upper side" and "lower side," are used in this specification, these terms are used to indicate relative positional relationships in one state, and the relative positional relationships can be inverted or rotated to any angle depending on the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0014] In this specification, the term "battery" is not limited to lithium ion batteries, but may include other batteries such as nickel-metal hydride batteries and sodium ion batteries. In this specification, the term "electrode" may collectively refer to a positive electrode and a negative electrode.

[0015] In addition, the "battery module" including the secondary battery in this specification can be mounted on hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), etc. However, the use of the "battery module" including the secondary battery in this specification is not limited to vehicle mounting.

[0016] In the drawings, the direction in which the first end and the second end of the separator of the electrode body face each other is the first direction, which is the X direction, the thickness direction of the flat electrode body is the Y direction, and the direction perpendicular to the first direction and the thickness direction of the electrode body is the Z direction. In addition, in order to facilitate understanding of the present technology, the dimensional ratios of each component in the drawings are sometimes shown differently from the actual dimensional ratios.

[0017] (Embodiment 1) Fig. 1 is a perspective view showing a configuration of a secondary battery according to a first embodiment of the present technology, Fig. 2 is a perspective view showing a configuration of an electrode assembly according to the first embodiment of the present technology.

[0018] The secondary battery according to the present embodiment is, for example, a non-aqueous lithium ion battery. The electric capacity of the secondary battery is, for example, 20 Ah or more and 220 Ah or less. As shown in Figs. 1 and 2, the secondary battery 100 includes an electrode terminal 110, a case 120, a gas release valve 130, and an electrode body 140.

[0019] The electrode terminal 110 has a positive electrode terminal 111 and a negative electrode terminal 112. The electrode terminal 110 is formed on a case 120.

[0020] The case 120 is a container that contains the electrode assembly 140 and the electrolyte. The case 120 has a substantially rectangular parallelepiped shape. The case 120 is made of aluminum, an aluminum alloy, iron, or an iron alloy such as stainless steel.

[0021] The length of case 120 in the X direction is, for example, 30 mm or more and 300 mm or less. The height of case 120 in the Z direction is, for example, 30 mm or more and 100 mm or less. The ratio of the length of case 120 in the X direction to the height of case 120 in the Z direction is, for example, 1 to 5 times. In this embodiment, the ratio of the length of case 120 in the X direction to the height of case 120 in the Z direction is, for example, 3 times.

[0022] As shown in FIG. 1, the case 120 has a sealing plate 121, a bottom surface 122, a pair of long side walls 123, and a pair of short side walls .

[0023] The sealing plate 121 constitutes the upper surface of the case 120. The electrode terminals 110 are disposed on the sealing plate 121. The bottom surface 122 faces the sealing plate 121 in the Z direction.

[0024] The pair of long side walls 123 and the pair of short side walls 124 form the side surfaces of the case 120. The pair of long side walls 123 and the pair of short side walls 124 intersect with the sealing plate 121 and the bottom surface 122, respectively. The pair of long side walls 123 face each other in the Y direction with the electrode body 140 therebetween. The pair of short side walls 124 face each other in the X direction with the electrode body 140 therebetween. Each of the pair of long side walls 123 has an area larger than each of the pair of short side walls 124.

[0025] The gas exhaust valve 130 breaks when the pressure inside the case 120 reaches or exceeds a predetermined value, thereby allowing the gas inside the case 120 to be exhausted to the outside of the case 120.

[0026] The electrode assembly 140 functions as a power generating element. As shown in FIG.

[0027] The electrode assembly 140 in this embodiment is a wound type electrode assembly in which a positive electrode plate 150, a negative electrode plate 160, and a separator 170 are wound around a winding axis A in a first direction (X direction). The separator 170 is located between the positive electrode plate 150 and the negative electrode plate 160.

[0028] The electrode body 140 is flat. For example, after the positive electrode plate 150, the negative electrode plate 160, and the separator 170 are wound, the electrode body 140 is pressed in a direction perpendicular to the winding axis A (the Y direction in FIG. 3 ) to form a flat shape.

[0029] The electrode body 140 may be a laminated electrode body in which positive electrode plates 150, separators 170, and negative electrode plates 160 are alternately laminated. When the electrode body is a laminated electrode body, the long positive electrode plates, separators, and negative electrode plates may be laminated by folding them in a zigzag shape.

[0030] The electrode body 140 has a rectangular shape including a long side direction and a short side direction when viewed from the thickness direction (Y direction). In this embodiment, the first direction (X direction) of the electrode body 140 is the long side direction of the electrode body 140. The Z direction of the electrode body 140 is the short side direction of the electrode body 140.

[0031] The positive electrode plate 150 has a positive electrode core 151 and a positive electrode active material layer 152. The positive electrode core 151 is a conductive sheet. The positive electrode core 151 is, for example, an aluminum alloy foil. The positive electrode active material layer 152 is disposed on the surface of the positive electrode core 151.

[0032] The positive electrode active material may be a lithium transition metal composite oxide, etc. In the present embodiment, the lithium transition metal composite oxide is, for example, lithium nickel cobalt manganese oxide.

[0033] The negative electrode plate 160 has a negative electrode core 161 and a negative electrode active material layer 162. The negative electrode core 161 is a conductive sheet. The negative electrode core 161 is, for example, a copper alloy foil. The negative electrode active material layer 162 is disposed on the surface of the negative electrode core 161.

[0034] Examples of the negative electrode active material include carbon materials such as artificial graphite, natural graphite, amorphous coated graphite, and amorphous carbon, non-carbon materials such as SiO, and mixtures of carbon materials and non-carbon materials.

[0035] The separator 170 is provided to insulate the positive electrode plate 150 from the negative electrode plate 160. The separator 170 has a structure including only a porous sheet as a substrate, or including a substrate and a heat-resistant layer.

[0036] The substrate has ion permeability and insulation properties, and examples of the substrate include a microporous thin film, a woven fabric, and a nonwoven fabric. The substrate is preferably made of an olefin resin such as polyethylene (PE) or polypropylene (PP), or cellulose. The substrate may be made of only a PE layer, or a laminate in which a PE layer is sandwiched between two PP layers.

[0037] The above-mentioned electrode body 140 is housed in the case 120 and then impregnated with an electrolytic solution. The electrolytic solution is composed of a nonaqueous electrolyte. The nonaqueous electrolyte includes a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. The nonaqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolyte), and may be a solid electrolyte using a gel-like polymer or the like. The nonaqueous solvent may be, for example, esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, or a mixed solvent of two or more of these.

[0038] The number of electrode bodies 140 contained in one secondary battery 100 may be one or more. When the number of electrode bodies is more than one, it is desirable that the electrode bodies are arranged side by side in the thickness direction (Y direction) of the electrode body 140.

[0039] FIG. 3 is a schematic diagram showing the flow of the electrolyte in the secondary battery according to the first embodiment of the present disclosure.

[0040] As shown in Fig. 3, the electrode assembly 140 housed inside the case 120 is impregnated with an electrolyte. When the secondary battery 100 is charged, the electrolyte is discharged from inside the electrode assembly 140 to the outside due to expansion of the electrode assembly 140 and the electrolyte. Since the electrode assembly 140 in this embodiment is a wound electrode assembly, the electrolyte is discharged to the outside of the electrode assembly 140 mainly from both ends of the winding axis A. In Fig. 3, the electrolyte is discharged from inside the electrode assembly 140 in the direction F1.

[0041] On the other hand, when the secondary battery 100 is discharged, the electrolyte permeates the inside of the electrode body 140 due to contraction of the electrode body 140 and the electrolyte, etc. As in the case of charging the secondary battery 100, since the electrode body 140 in this embodiment is a wound electrode body, the electrolyte permeates the inside of the electrode body 140 mainly from both ends of the winding axis A. In Fig. 3, the electrolyte permeates the inside of the electrode body 140 from the direction F2.

[0042] Fig. 4 is a plan view showing a configuration of a separator included in an electrode body of a secondary battery according to embodiment 1 of the present disclosure. Fig. 5 is a partial cross-sectional view of the secondary battery of Fig. 4, seen from the direction of the VV arrows. Fig. 6 is a partial cross-sectional view of the secondary battery of Fig. 4, seen from the direction of the VI-VI arrows.

[0043] As shown in FIGS. 4 to 6, the separator 170 includes a first region R1 and a second region R2.

[0044] The first region R1 is located at both ends in a first direction (X direction). When viewed from the thickness direction (Y direction) of the electrode body, the first region R1 includes a first end 171 and a second end 172 that face each other in a first direction (X direction) perpendicular to the thickness direction (Y direction). The first end 171 and the second end 172 serve as inlets for the electrolyte to permeate the inside of the electrode body 140.

[0045] The first region R1 has a length on one side that is ¼ to ⅓ of the total length in the first direction (X direction) of separator 170. In the present embodiment, the first region R1 has approximately the same length on each of the first end 171 side and the second end 172 side in the first direction (X direction), but may have different lengths.

[0046] The second region R2 is sandwiched between the first regions R1 in the first direction (X direction) when viewed from the thickness direction (Y direction) of the electrode body, and includes the central portion 173 of the separator 170. The second region R2 has a length that is ⅓ or more and ½ or less of the total length of the separator 170 in the first direction (X direction). In this embodiment, each of the first regions R1 on both sides and the second region R2 has a length that is equally divided into about ⅓ in the first direction (X direction).

[0047] The surface of the separator 170 is provided with recesses 174 into which the electrolyte can flow. The recesses 174 are disposed in at least the first region R1. By providing the recesses 174 in at least the first region R1, a flow path for the electrolyte can be secured around the first end 171 and the second end 172, which serve as inlets for the electrolyte to permeate the inside of the electrode body 140, so that the electrolyte can easily permeate the inside of the electrode body 140. In the present embodiment, the recesses 174 are provided in each of the first region R1 and the second region R2 of the separator 170.

[0048] The recess 174 in this embodiment includes a plurality of grooves 175. Each of the plurality of grooves 175 included in the recess 174 extends along the first direction (X direction) and reaches from the first end 171 to the second end 172 of the separator 170. Since the plurality of grooves 175 are provided to communicate with both ends of the separator 170, the electrolyte can easily flow through the recess 174.

[0049] 5 and 6, when viewed from the first direction (X direction), a cross-sectional area S11 of the recess 174 in the first region R1 of the separator 170 is larger than a cross-sectional area S12 of the recess 174 in the second region R2 of the separator 170. The cross-sectional area of ​​the recess 174 in this embodiment is the sum of the cross-sectional areas of the multiple groove portions 175.

[0050] The cross-sectional area of ​​the recesses 174 in the first region R1 and the second region R2 is, for example, in the range of 3% to 10% of the cross-sectional area of ​​the separator 170. This makes it possible to easily impregnate the inside of the electrode body 140 with the electrolyte while ensuring the strength of the separator 170.

[0051] 4 to 6, in the present embodiment, when viewed in the thickness direction (Y direction), an occupied area S21 of the recess 174 in the first region R1 of the separator 170 is larger than an occupied area S22 of the recess 174 in the second region R2 of the separator 170. The occupied area of ​​the recess 174 in the present embodiment is the sum of the occupied areas of the multiple groove portions 175.

[0052] The area occupied by the recess 174 varies depending on the width in the Z direction of the multiple grooves 175. The width W1 of each of the multiple grooves 175 in the first region R1 is, for example, 3% to 5% of the height in the Z direction of the separator 170. The width W2 of each of the multiple grooves 175 in the second region R2 is, for example, 0% to less than 3% of the height in the Z direction of the separator 170.

[0053] In this embodiment, the width in the Z direction of each of the plurality of grooves 175 smoothly slopes down from the first end 171 and the second end 172 toward the central portion 173. Note that it is sufficient for the plurality of grooves 175 to have an occupied area in the first region R1 larger than their occupied area in the second region R2, and the shape defining the width of the plurality of grooves 175 may be a curve such as a wave shape extending from the first end 171 and the second end 172 toward the central portion 173.

[0054] The average depth of the recesses 174 in the first region R1 of the separator 170 is greater than the average depth of the recesses 174 in the second region R2 of the separator 170. In the present embodiment, the depth D1 of the multiple grooves 175 in the first region R1 is greater than the depth D2 of the multiple grooves 175 in the second region R2.

[0055] The ratio of the depth of the recesses 174 in the first region R1 is, for example, 30% or more and 50% or less with respect to the thickness of the separator 170. In this embodiment, the ratio of the depth D1 of the multiple grooves 175 in the first region R1 is 30% or more and 50% or less with respect to the thickness of the separator 170. The ratio of the depth of the recesses 174 in the second region R2 is, for example, 0% or more and less than 30% with respect to the thickness of the separator 170. In this embodiment, the ratio of the depth D2 of the multiple grooves 175 in the second region R2 is 1% or more and less than 30% with respect to the thickness of the separator 170.

[0056] In this embodiment, the depth of each of the plurality of grooves 175 smoothly slopes downward from the first end 171 and the second end 172 toward the central portion 173. Note that it is sufficient for the plurality of grooves 175 to have an average depth in the first region R1 that is deeper than the average depth in the second region R2, and the shape that defines the depth of the plurality of grooves 175 may be a curve such as a wave shape extending from the first end 171 and the second end 172 toward the central portion 173.

[0057] The width or depth of each of the plurality of grooves 175 may be different. When the depths of the plurality of grooves 175 are different, the average depth of the recess 174 can be calculated, for example, by averaging the depths of the plurality of grooves 175 from the surface of the separator 170 in one cross section in a direction (Z direction) perpendicular to the first direction. In the present embodiment, the recess 174 is disposed on the positive electrode plate 150 side of the separator 170, but may be provided on the negative electrode plate 160 side.

[0058] The recesses 174 are formed, for example, by roll pressing. Specifically, the separator 170 is passed between one roll having a convex shape in a part of the circumferential direction and the other roll. The convex shape of the one roll comes into contact with the separator 170, deforming the surface of the separator 170. As a result, the convex shape of the one roll is transferred to the surface of the separator 170, and the recesses 174 are formed in the separator 170.

[0059] The cross-sectional shape of the grooves 175 in the recess 174 is not limited to a curved shape. Fig. 7 is a partial cross-sectional view showing a configuration of a separator included in an electrode body of a secondary battery according to a first modified example of the first embodiment of the present technology. Fig. 8 is a partial cross-sectional view showing a configuration of a separator included in an electrode body of a secondary battery according to a second modified example of the first embodiment of the present technology.

[0060] 7, the electrode assembly according to the first modification of the present embodiment includes a separator 170A. The separator 170A has a recess 174A that includes a plurality of grooves 175A. The plurality of grooves 175A have an inclined surface shape formed by two flat surfaces.

[0061] 8, the electrode assembly according to the second modification of the present embodiment includes a separator 170B. The separator 170B has a recess 174B including a plurality of grooves 175B. The shape of the plurality of grooves 175B is a polygonal shape defined by three planes.

[0062] The cross-sectional shape of the recesses can be various shapes depending on the strength of the separator, the depth, width or number of the recesses relative to the separator, or the ease of processing the recesses.

[0063] Fig. 9 is a graph showing the discharge characteristics of the secondary battery based on the relationship between the discharge time and the voltage of the secondary battery according to the first embodiment of the present technology and the comparative example. Fig. 10 is a graph showing the relationship between the number of charge / discharge cycles and the battery capacity deterioration degree of the secondary battery according to the first embodiment of the present technology and the comparative example.

[0064] The secondary battery according to the comparative example differs from the secondary battery 100 according to the present embodiment in that no recess is provided on the surface of the separator. When the secondary battery according to the comparative example is rapidly charged, the electrode body and the electrolyte expand rapidly, so that the electrolyte is likely to flow out of the electrode body, and the concentration of the electrolyte is likely to be uneven between the outside and inside of the electrode body. Therefore, as shown in FIG. 9, the secondary battery according to the comparative example is likely to have uneven salt concentration of the electrolyte, so that the electrode body is likely to have an increase in electrical resistance in parts, and the discharge characteristics are likely to deteriorate. In addition, as shown in FIG. 10, the secondary battery according to the comparative example is likely to have a deteriorated electric capacity when the electrode body is repeatedly charged and discharged.

[0065] On the other hand, in the secondary battery 100 including the separator 170 in which the recesses 174 of the present embodiment are formed, the recesses 174 become a flow path for the electrolyte, so that the electrolyte is more likely to penetrate into the electrode body 140 than in the secondary battery according to the comparative example. Therefore, as shown in FIG. 9, unevenness in the salt concentration of the electrolyte is less likely to occur, and an increase in electrical resistance is partially suppressed in the electrode body 140, thereby improving the discharge characteristics. The secondary battery 100 of the present embodiment can maintain a desired voltage value for a long time compared to the secondary battery of the comparative example. In addition, as shown in FIG. 10, unevenness in the salt concentration of the electrolyte is less likely to occur, so that deterioration of the electrical capacity is suppressed when the electrode body 140 is repeatedly charged and discharged. In the secondary battery 100 of the present embodiment, deterioration of the electrical capacity is slower even when the charge and discharge cycle is repeated than in the secondary battery of the comparative example.

[0066] In the secondary battery 100 according to the first embodiment of the present technology, by providing a recess 174 in the first region R1 of the separator 170 including the first end 171 and the second end 172, it is possible to facilitate the inflow of the electrolyte into the inside of the electrode body 140 through the recess 174. By making the cross-sectional area of ​​the recess 174 relatively large in the first region R1 located on the end side of the electrode body 140 and relatively small in the second region R2 located on the center side of the electrode body 140, it is possible to facilitate the inflow of the electrolyte at the end side of the electrode body 140 and to ensure the strength of the separator 170 at the center side of the electrode body 140 where a load is likely to be applied when the electrode body 140 expands. As a result, it is possible to achieve both the impregnation of the electrolyte into the inside of the electrode body 140 and the ensuring of the strength of the separator 170.

[0067] In the secondary battery 100 according to embodiment 1 of the present technology, by making the area occupied by the recess 174 relatively small when viewed from the thickness direction (Y direction) at the center of the electrode body 140, the electrode body 140 is prone to expansion, and the strength of the separator 170 can be ensured in the central portion 173 of the electrode body 140 where the strength of the separator 170 is required.

[0068] In the secondary battery 100 according to the first embodiment of the present technology, even if the electrode body 140 is elongated in the first direction (X direction), the electrolyte can be caused to flow into the inside of the electrode body 140 from the recess 174, so that it is possible to achieve both the impregnation of the electrolyte into the inside of the electrode body 140 and the securing of the strength of the separator 170.

[0069] In the secondary battery 100 according to the first embodiment of the present technology, a groove portion 175 is formed extending from the first end 171 to the second end 172 of the separator 170, thereby making it easier for the electrolyte to flow into the recess 174.

[0070] In the secondary battery 100 relating to embodiment 1 of the present technology, the average depth of the recesses 174 in the first region R1 of the separator 170 is greater than the average depth of the recesses 174 in the second region R2 of the separator 170, making it easier to ensure the strength of the separator 170 in the second region R2 including the central portion 173 of the electrode body 140 where the amount of expansion of the electrode body 140 is large.

[0071] In the secondary battery 100 according to the first embodiment of the present technology, by providing recesses 174 on both ends of the wound electrode body in the direction of the winding axis A along which the electrolyte mainly flows, it is possible to easily impregnate the inside of the wound electrode body with the electrolyte.

[0072] Secondary batteries according to embodiments 2 and 3 of the present technology will be described below. Since the secondary batteries according to these embodiments have different configurations of the separator recesses from secondary battery 100 according to embodiment 1 of the present technology, the description of the configurations similar to those of secondary battery 100 according to embodiment 1 of the present technology will not be repeated.

[0073] (Embodiment 2) Fig. 11 is a plan view showing a configuration of a separator included in an electrode assembly of a secondary battery according to embodiment 2 of the present technology. As shown in Fig. 11, a separator 170C in this embodiment includes a plurality of holes 176C as recesses 174C. The plurality of holes 176C are aligned in a first direction (X direction) and Z direction. The plurality of holes 176C are rectangular when viewed from the thickness direction (Y direction) of the electrode assembly.

[0074] The holes 176C are arranged in the first region R1. Each of the first region R1 and the second region R2 occupies about half the length of the separator 170C in the first direction (X direction).

[0075] The occupancy area of ​​the recess 174C decreases from the first region R1 toward the second region R2. The cross-sectional area of ​​the recess 174C can be confirmed in a cross section at a position where the multiple holes 176C are aligned in the Z direction perpendicular to the first direction (X direction).

[0076] In the secondary battery according to the second embodiment of the present technology, the electrolyte that flows from the inside to the outside of the electrode body during charging is stored in the recess 174C that includes the multiple holes 176C, making it easier to return the electrolyte that has accumulated in the multiple holes 176C to the center during discharging.

[0077] (Embodiment 3) Fig. 12 is a plan view showing a configuration of a separator included in an electrode assembly of a secondary battery according to embodiment 3 of the present technology. As shown in Fig. 12, separator 170D in this embodiment includes a plurality of holes 176D as recesses 174D. The plurality of holes 176D are aligned in a first direction (X direction) and Z direction. The plurality of holes 176D are round when viewed from the thickness direction (Y direction) of the electrode assembly.

[0078] In the present embodiment, the holes 176D are arranged in the first region R1. Each of the first region R1 and the second region R2 occupies about half the length of the separator 170D in the first direction (X direction).

[0079] In the secondary battery according to embodiment 3 of the present technology, as in embodiment 2, the electrolyte that flows from the inside to the outside of the electrode body during charging is stored in recess 174D including multiple holes 176D, making it easier to return the electrolyte that has accumulated in multiple holes 176D to the center during discharging.

[0080] In each of the above-described embodiments, the recess is configured as either a groove or a hole, but is not limited to this configuration, and the recess may be configured as a combination of a groove and a hole.

[0081] Although the embodiment of the present technology has been described above, the embodiment disclosed herein should be considered as illustrative and not restrictive in all respects. The scope of the present technology is defined by the claims, and it is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0082] 100 secondary battery, 110 electrode terminal, 111 positive electrode terminal, 112 negative electrode terminal, 120 case, 121 sealing plate, 122 bottom surface, 123 pair of long side walls, 124 pair of short side walls, 130 gas exhaust valve, 140 electrode body, 150 positive electrode plate, 151 positive electrode core body, 152 positive electrode active material layer, 160 negative electrode plate, 161 negative electrode core body, 162 negative electrode active material layer, 170, 170A, 170B, 170C, 170D separator, 171 first end, 172 second end, 173 central portion, 174, 174A, 174B, 174C, 174D recess, 175, 175A, 175B multiple groove portions, 176C, 176D Multiple holes, A winding axis, R1 first region, R2 second region.

Claims

1. A flat electrode assembly including a positive electrode plate, a separator, and a negative electrode plate, the separator being disposed between the positive electrode plate and the negative electrode plate; A case is provided to accommodate the electrode assembly and an electrolyte solution, When viewed from a thickness direction of the electrode body, the separator includes a first region including a first end and a second end that face each other in a first direction perpendicular to the thickness direction, and a second region that is sandwiched between the first regions in the first direction and includes a central portion of the separator, a recessed portion is provided on a surface of the separator, the recessed portion being disposed at least in the first region and into which the electrolytic solution can flow; A secondary battery, wherein a cross-sectional area of ​​the recess in the first region of the separator is larger than a cross-sectional area of ​​the recess in the second region of the separator when viewed from the first direction.

2. The secondary battery according to claim 1 , wherein an area occupied by the recesses in the first region of the separator is larger than an area occupied by the recesses in the second region of the separator when viewed in the thickness direction.

3. 3 . The secondary battery according to claim 1 , wherein the electrode body has a rectangular shape including a longitudinal direction and a lateral direction when viewed from the thickness direction, and the first direction is the longitudinal direction of the electrode body.

4. 3. The secondary battery according to claim 1, wherein the recess includes a groove portion that extends along the first direction and reaches from the first end to the second end of the separator.

5. The secondary battery according to claim 4 , wherein an average depth of the recesses in the first region of the separator is greater than an average depth of the recesses in the second region of the separator.

6. The secondary battery according to claim 1 , wherein the recess includes a plurality of holes aligned in the first direction.

7. 3. The secondary battery according to claim 1, wherein the electrode assembly is a wound electrode assembly in which the positive electrode plate, the separator, and the negative electrode plate are wound around an axis in the first direction.

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