Secondary battery

Abstract

The present technology relates to a secondary battery. The diaphragm according to the present invention includes: a first region including a first end portion and a second end portion that face each other in a first direction orthogonal to a thickness direction; and a second region sandwiched by the first region in the first direction and including a central portion of the diaphragm. The surface of the diaphragm is provided with a recess that is disposed at least in the first region and into which the electrolyte can flow. The cross-sectional area of the recess in the first region of the diaphragm is larger than the cross-sectional area of the recess in the second region of the diaphragm when viewed from the first direction.

Description

Technical Field

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

[0002] As a prior art document that discloses the structure of a non-aqueous electrolyte secondary battery, there is Japanese Patent Publication No. 2014-203668. The non-aqueous electrolyte secondary battery described in Japanese Patent Publication No. 2014-203668 includes a negative electrode collector, a negative electrode active material composite material portion, and a separator. The negative electrode collector is a metal film. A plurality of negative electrode active material composite materials are formed and protrude from the negative electrode collector toward the separator.

[0003] As a prior art document that discloses the structure of a lithium-ion battery, there is Japanese Patent Publication No. 2012-243567. The lithium-ion battery described in Japanese Patent Publication No. 2012-243567 has 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 concave and convex surfaces that mesh with each other with a separator sandwiched between them.

[0004] In the secondary batteries described in Japanese Patent Publication No. 2014-203668 and Japanese Patent Publication No. 2012-243567, although the strength of the separator in the electrode body is ensured, there is a possibility that a gap between the separator and the positive electrode plate or the negative electrode plate that can be impregnated with the electrolyte cannot be ensured due to the expansion of the negative electrode active material, etc. Therefore, it is difficult to simultaneously impregnate the electrolyte discharged from the electrode body to the outside during charging, etc., into the inside of the electrode body and ensure the strength of the separator. Summary of the invention

[0005] The present technology has been made to solve the above-mentioned problems, and an object of the present technology is to provide a secondary battery capable of achieving both impregnation of an electrolyte solution into an electrode body and ensuring strength of a separator.

[0006] The present technology provides the following secondary batteries.

[0007] [1] A secondary battery, wherein the secondary battery comprises: a flat electrode body including a positive electrode plate, a separator and a negative electrode plate, the separator being located between the positive electrode plate and the negative electrode plate; and a housing accommodating the electrode body and an electrolyte, wherein the separator comprises: a first region including a first end and a second end facing each other in a first direction orthogonal to the thickness direction when viewed from the thickness direction of the electrode body; and a second region sandwiched by the first region in the first direction and including a central portion of the separator, wherein a recess is provided on a surface of the separator, the recess being arranged at least in the first region and capable of allowing the electrolyte to flow in, and 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.

[0008] [2] The secondary battery according to [1], wherein, when viewed in the thickness direction, an area occupied by the recess in the first region of the separator is larger than an area occupied by the recess in the second region of the separator.

[0009] [3] The secondary battery according to [1] or [2], wherein the electrode body has a rectangular shape including a long side direction and a short side direction when viewed from the thickness direction, and the first direction is the long side direction of the electrode body.

[0010] [4] The secondary battery according to any one of [1] to [3], wherein the recess includes a groove portion extending along the first direction from the first end portion to the second end portion of the separator.

[0011] [5] The secondary battery according to [4], wherein an average depth of the recessed portions in the first region of the separator is greater than an average depth of the recessed portions in the second region of the separator.

[0012] [6] The secondary battery according to any one of [1] to [3], wherein the recess includes a plurality of holes arranged in the first direction.

[0013] [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.

[0014] The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a perspective view showing the structure of the secondary battery according to the first embodiment of the present technology.

[0016] Figure 2 It is a perspective view showing the structure of the electrode body according to the first embodiment of the present technology.

[0017] Figure 3 This is a schematic diagram showing the flow of the electrolyte solution in the secondary battery according to the first embodiment of the present technology.

[0018] Figure 4 It is a plan view showing the structure of a separator included in the electrode assembly of the secondary battery according to the first embodiment of the present technology.

[0019] Figure 5 Observe from the direction of the arrow on the VV line Figure 4 A partial cross-sectional view of a secondary battery.

[0020] Figure 6 Observe from the direction of the arrow on line VI-VI Figure 4 A partial cross-sectional view of a secondary battery.

[0021] Figure 7 This is a partial cross-sectional view showing the structure of a separator included in an electrode body of a secondary battery according to a first modification of the first embodiment of the present technology.

[0022] Figure 8 This is a partial cross-sectional view showing the structure of a separator included in an electrode assembly of a secondary battery according to a second modification of the first embodiment of the present technology.

[0023] Fig. 9 This is a graph showing the discharge characteristics of the secondary batteries by the relationship between the discharge time and the voltage of the secondary batteries according to the first embodiment of the present technology and the comparative example.

[0024] Fig.10 This is a graph showing the relationship between the number of charge and discharge cycles and the degree of battery capacity degradation of the secondary batteries according to the first embodiment of the present technique and the comparative example.

[0025] Fig.11 It is a plan view showing the structure of a separator included in an electrode assembly of a secondary battery according to a second embodiment of the present technique.

[0026] Fig.12 It is a plan view showing the structure of a separator included in an electrode assembly of a secondary battery according to a third embodiment of the present technique. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present technology will be described. In addition, the same reference numerals are given to the same or corresponding parts, and the description thereof may not be repeated.

[0028] In addition, in the embodiments described below, when the number, quantity, etc. are mentioned, the scope of the present technology is not necessarily limited to the number, quantity, etc., unless otherwise specified. In addition, in the following embodiments, except for the cases specifically specified, each structural element is not necessarily essential to the present technology. In addition, the present technology is not necessarily limited to the technology that has all the effects mentioned in the embodiments.

[0029] In addition, in this specification, the descriptions of "comprise", "include", and "have" are open-ended. That is, when a certain structure is included, other structures other than the structure may be included or not included.

[0030] In addition, when geometrical terms and terms indicating position and direction relationships, such as "parallel", "orthogonal", "inclined at 45 degrees", "coaxial", "along", etc., are used in this specification, those terms allow for manufacturing errors or slight changes. When terms such as "upper side" and "lower side" are used in this specification to indicate relative positional relationships, those terms are used as terms indicating relative positional relationships in one state, and the relative positional relationship can be reversed or rotated to any angle depending on the installation direction of each mechanism (for example, turning the entire mechanism upside down, etc.).

[0031] In this specification, the term "battery" is not limited to lithium-ion batteries, and may include other batteries such as nickel-hydrogen batteries and sodium-ion batteries. In this specification, the term "electrode" may collectively refer to a positive electrode and a negative electrode.

[0032] In addition, the "battery module" including the secondary battery in this specification can be mounted on a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an electric vehicle (BEV), etc. However, the use of the "battery module" including the secondary battery in this specification is not limited to vehicle use.

[0033] In addition, in the drawings, the direction in which the first end and the second end of the separator of the electrode body are opposite to each other is set as the X direction as the first direction, the thickness direction of the flat electrode body is set as the Y direction, and the direction orthogonal to the first direction and the thickness direction of the electrode body is set as the Z direction. In addition, in order to facilitate understanding of the present technology, there are parts in which the dimensional ratios of each structure in the drawings are changed from the actual dimensional ratios.

[0034] (Implementation Method 1)

[0035] Figure 1 It is a perspective view showing the structure of the secondary battery according to the first embodiment of the present technology. Figure 2 It is a perspective view showing the structure of the electrode body according to the first embodiment of the present technology.

[0036] The secondary battery involved in this embodiment is, for example, a non-aqueous lithium ion battery. The electrical capacity of the secondary battery is, for example, not less than 20 Ah and not more than 220 Ah. Figure 1 and Figure 2 As shown, the secondary battery 100 includes an electrode terminal 110 , a housing 120 , a gas exhaust valve 130 , and an electrode body 140 .

[0037] The electrode terminal 110 has a positive terminal 111 and a negative terminal 112. The electrode terminal 110 is formed on the case 120.

[0038] The outer shell 120 is a container for accommodating the electrode body 140 and the electrolyte. The outer shell 120 has a substantially rectangular parallelepiped shape. The outer shell 120 is made of aluminum, aluminum alloy, iron, or iron alloy such as stainless steel.

[0039] The length of the housing 120 in the X direction is, for example, 30 mm to 300 mm. In addition, the height of the housing 120 in the Z direction is, for example, 30 mm to 100 mm. The ratio of the length of the housing 120 in the X direction to the height in the Z direction is, for example, 1 to 5 times. In the present embodiment, the ratio of the length of the housing 120 in the X direction to the height in the Z direction is, for example, 3 times.

[0040] like Figure 1 As shown, the housing 120 has a sealing plate 121 , a bottom surface 122 , a pair of long side walls 123 , and a pair of short side walls 124 .

[0041] The sealing plate 121 constitutes the upper surface of the housing 120. The electrode terminal 110 is disposed on the sealing plate 121. The bottom surface 122 faces the sealing plate 121 in the Z direction.

[0042] A pair of long side walls 123 and a pair of short side walls 124 constitute the side of the housing 120. The pair of long side walls 123 and the pair of short side walls 124 intersect the sealing plate 121 and the bottom surface 122, respectively. The pair of long side walls 123 are respectively opposed to each other with the electrode body 140 interposed therebetween in the Y direction. The pair of short side walls 124 are respectively opposed to each other with the electrode body 140 interposed therebetween in the X direction. The pair of long side walls 123 each have an area greater than that of each of the pair of short side walls 124.

[0043] When the pressure in the housing 120 reaches a predetermined value or more, the gas discharge valve 130 is broken, thereby discharging the gas in the housing 120 to the outside of the housing 120 .

[0044] The electrode body 140 functions as a power generation element. Figure 2 As shown, the electrode body 140 includes a positive electrode plate 150 , a negative electrode plate 160 , and a separator 170 .

[0045] The electrode body 140 in this embodiment is a wound type electrode body 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 .

[0046] 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 positive electrode plate 150, the negative electrode plate 160 and the separator 170 are wound in a direction perpendicular to the winding axis A (in the direction of the winding axis A). Figure 3 The electrode body 140 is punched (in the Y direction) to form the electrode body 140 into a flat shape.

[0047] The electrode body 140 may be a stacked electrode body in which positive electrode plates 150, separators 170, and negative electrode plates 160 are alternately stacked. In the case of a stacked electrode body, elongated positive electrode plates, separators, and negative electrode plates may be stacked by folding them in a zigzag shape.

[0048] 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 the present embodiment, the first direction (X direction) of the electrode body 140 is the long side direction of the electrode body 140. In addition, the Z direction of the electrode body 140 is the short side direction of the electrode body 140.

[0049] The positive electrode plate 150 includes 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 .

[0050] Examples of the positive electrode active material include lithium transition metal composite oxides, etc. The lithium transition metal composite oxide in the present embodiment is, for example, lithium nickel cobalt manganese oxide.

[0051] The negative electrode plate 160 includes 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 .

[0052] Examples of the negative electrode active material include carbon materials such as artificial graphite, natural graphite, amorphous coat graphite, and amorphous carbon, non-carbon materials such as SiO, and mixtures of carbon materials and non-carbon materials.

[0053] 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 base material, or a base material and a heat-resistant layer.

[0054] The substrate has ion permeability and insulation, and examples thereof include microporous films, fabrics, or nonwoven fabrics. The material of the substrate is preferably olefin resins such as polyethylene (PE) and polypropylene (PP), or cellulose. The material of the substrate may be, for example, only a PE layer, or a laminated body in which a PE layer is sandwiched between two PP layers.

[0055] The electrode body 140 is immersed in an electrolyte after being housed in the housing 120. The electrolyte is composed of a non-aqueous electrolyte. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (non-aqueous electrolyte), but may also be a solid electrolyte using a colloidal polymer or the like. The non-aqueous 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.

[0056] The number of electrode bodies 140 accommodated in one secondary battery 100 may be one or more. When there are more than one electrode bodies, the plurality of electrode bodies are preferably arranged in a row in the thickness direction (Y direction) of the electrode body 140 .

[0057] Figure 3 This is a schematic diagram showing the flow of the electrolyte solution in the secondary battery according to the first embodiment of the present technology.

[0058] like Figure 3 As shown, the electrode body 140 contained in the housing 120 is impregnated with an electrolyte. When the secondary battery 100 is charged, the electrolyte is discharged from the inside of the electrode body 140 to the outside due to the expansion of the electrode body 140 and the electrolyte. The electrode body 140 in this embodiment is a wound electrode body, so the electrolyte is mainly discharged from both ends of the winding axis A to the outside of the electrode body 140. Figure 3 In the process, the electrolyte is discharged from the interior of the electrode body 140 in the direction F1.

[0059] On the other hand, when the secondary battery 100 is discharged, the electrolyte is impregnated into the electrode body 140 due to the contraction of the electrode body 140 and the electrolyte. As in the case of charging the secondary battery 100, the electrode body 140 in this embodiment is a wound electrode body, so the electrolyte is impregnated into the electrode body 140 mainly from both ends of the winding axis A. Figure 3 In the process, the electrolyte solution is impregnated into the interior of the electrode body 140 from the F2 direction.

[0060] Figure 4 It is a plan view showing the structure of a separator included in the electrode assembly of the secondary battery according to the first embodiment of the present technology. Figure 5 Observe from the direction of the arrow on the VV line Figure 4 A partial cross-sectional view of a secondary battery. Figure 6 Observe from the direction of the arrow on line VI-VI Figure 4 A partial cross-sectional view of a secondary battery.

[0061] like Figures 4 to 6 As shown, the diaphragm 170 includes a first region R1 and a second region R2.

[0062] The first region R1 is located at both ends of the 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 are opposite to each other in the first direction (X direction) orthogonal to the thickness direction (Y direction). The first end 171 and the second end 172 serve as inlets for the electrolyte to be immersed in the interior of the electrode body 140.

[0063] The first region R1 has a length of 1 / 4 or more and 1 / 3 or less of the total length of the diaphragm 170 in the first direction (X direction) on one side. The first region R1 in this embodiment has substantially the same length on the first end 171 side and the second end 172 side in the first direction (X direction), but may be different from each other.

[0064] When viewed from the thickness direction (Y direction) of the electrode body, the second region R2 is sandwiched by the first region R1 in the first direction (X direction) and includes the central portion 173 of the separator 170. The second region R2 has a length of not less than 1 / 3 and not more than 1 / 2 of the total length of the separator 170 in the first direction (X direction). In the present embodiment, each of the first regions R1 on both sides and the second region R2 has a length equally divided into about 1 / 3 in the first direction (X direction).

[0065] The surface of the separator 170 is provided with a recess 174 into which the electrolyte can flow. The recess 174 is disposed at least in the first region R1. By providing the recess 174 at least in the first region R1, a flow path of the electrolyte can be ensured around the first end 171 and the second end 172, which are inlets when the electrolyte is impregnated into the interior of the electrode body 140, so that the electrolyte is easily impregnated into the interior of the electrode body 140. In the present embodiment, the recess 174 is provided in the first region R1 and the second region R2 of the separator 170, respectively.

[0066] The recessed portion 174 in this embodiment includes a plurality of grooves 175. The plurality of grooves 175 included in the recessed portion 174 extend along the first direction (X direction) from the first end 171 of the separator 170 to the second end 172. Since the plurality of grooves 175 are provided by connecting both ends of the separator 170, the electrolyte easily flows in the recessed portion 174.

[0067] like Figure 5 and Figure 6 As shown, when viewed from the first direction (X direction), the cross-sectional area S11 of the recess 174 in the first region R1 of the diaphragm 170 is larger than the cross-sectional area S12 of the recess 174 in the second region R2 of the diaphragm 170. The cross-sectional area of ​​the recess 174 in this embodiment is the sum of the cross-sectional areas of the plurality of grooves 175.

[0068] The cross-sectional area of ​​the recess 174 in the first region R1 and the second region R2 is, for example, 3% to 10% of the cross-sectional area of ​​the separator 170 . Therefore, the strength of the separator 170 can be ensured and the electrolyte can be easily impregnated into the electrode body 140 .

[0069] like Figures 4 to 6 As shown, in this embodiment, when viewed in the thickness direction (Y direction), the occupied area S21 of the recessed portion 174 in the first region R1 of the diaphragm 170 is larger than the occupied area S22 of the recessed portion 174 in the second region R2 of the diaphragm 170. The occupied area of ​​the recessed portion 174 in this embodiment is the area obtained by summing the occupied areas of the plurality of grooves 175.

[0070] The area occupied by the recessed portion 174 varies according to the width of the plurality of grooves 175 in the Z direction. The width W1 of each of the plurality of grooves 175 in the first region R1 is, for example, 3% or more and 5% or less relative to the height of the diaphragm 170 in the Z direction. The width W2 of each of the plurality of grooves 175 in the second region R2 is, for example, 0% or more and less than 3% relative to the height of the diaphragm 170 in the Z direction.

[0071] In the present embodiment, the width of each of the plurality of grooves 175 in the Z direction is smoothly inclined and reduced from the first end 171 and the second end 172 toward the central portion 173. In addition, for the plurality of grooves 175, the occupied area in the first region R1 may be larger than the occupied area in the second region R2, and the shape defining the width of the plurality of grooves 175 may also be a curve such as a wave shape from the first end 171 and the second end 172 toward the central portion 173.

[0072] The average depth of the recesses 174 in the first region R1 of the diaphragm 170 is greater than the average depth of the recesses 174 in the second region R2 of the diaphragm 170. In the present embodiment, the depth D1 of the grooves 175 in the first region R1 is greater than the depth D2 of the grooves 175 in the second region R2.

[0073] The ratio of the depth of the recessed portion 174 in the first region R1 is, for example, 30% to 50% or less relative to the thickness of the diaphragm 170. In the present embodiment, the ratio of the depth D1 of the plurality of grooves 175 in the first region R1 is 30% to 50% or less relative to the thickness of the diaphragm 170. The ratio of the depth of the recessed portion 174 in the second region R2 is, for example, 0% to less than 30% relative to the thickness of the diaphragm 170. In the present embodiment, the ratio of the depth D2 of the plurality of grooves 175 in the second region R2 is 1% to less than 30% relative to the thickness of the diaphragm 170.

[0074] In the present embodiment, the depth of each of the plurality of grooves 175 is smoothly inclined and becomes shallower from the first end 171 and the second end 172 toward the central portion 173. In addition, for the plurality of grooves 175, the average depth in the first region R1 may be 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 from the first end 171 and the second end 172 toward the central portion 173.

[0075] In addition, the widths or depths of the plurality of grooves 175 may be different from each other. When the depths of the plurality of grooves 175 are different, the average depth of the recess 174 can be calculated by averaging the depths of each of the plurality of grooves 175 from the surface of the separator 170 in a cross section in a direction (Z direction) perpendicular to the first direction. In addition, in the present embodiment, the recess 174 is arranged on the positive electrode plate 150 side of the separator 170, but it may also be arranged on the negative electrode plate 160 side.

[0076] The recessed portion 174 is formed, for example, by rolling. Specifically, the diaphragm 170 is passed between a roller and another roller having a convex shape in a portion of the circumferential direction. The convex shape of the one roller contacts the diaphragm 170, deforming the surface of the diaphragm 170. Thus, the convex shape of the one roller is transferred to the surface of the diaphragm 170, so that the recessed portion 174 is formed in the diaphragm 170.

[0077] The cross-sectional shape of the plurality of grooves 175 in the recess 174 is not limited to a curved shape. Figure 7 This is a partial cross-sectional view showing the structure of a separator included in an electrode body of a secondary battery according to a first modification of the first embodiment of the present technology. Figure 8 This is a partial cross-sectional view showing the structure of a separator included in an electrode assembly of a secondary battery according to a second modification of the first embodiment of the present technology.

[0078] like Figure 7 As shown in FIG. 1 , the electrode assembly according to the first modification of the present embodiment includes a separator 170A. The separator 170A includes a recess 174A including a plurality of grooves 175A. The plurality of grooves 175A have an inclined surface shape composed of two flat surfaces.

[0079] like Figure 8 As shown in FIG. 1 , the electrode body 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 plurality of grooves 175B are in a square shape consisting of three flat surfaces.

[0080] The cross-sectional shape of the recessed portion can adopt various shapes depending on the strength of the diaphragm, the depth, width, or number of the recessed portion relative to the diaphragm, or the ease of processing the recessed portion.

[0081] Fig. 9 This is a graph showing the discharge characteristics of the secondary batteries by the relationship between the discharge time and the voltage of the secondary batteries according to the first embodiment of the present technology and the comparative example. Fig.10 This is a graph showing the relationship between the number of charge and discharge cycles and the degree of battery capacity degradation of the secondary batteries according to the first embodiment of the present technique and the comparative example.

[0082] The secondary battery involved in the comparative example does not have a recessed portion on the surface of the separator, which is different from the secondary battery 100 in the present embodiment. When the secondary battery involved in the comparative example is rapidly charged, the electrode body and the electrolyte rapidly expand, so the electrolyte easily flows out of the electrode body, and the concentration of the electrolyte is easily uneven on the outside and inside of the electrode body. Fig. 9 As shown in FIG. 1 , the secondary battery according to the comparative example is prone to uneven salt concentration in the electrolyte, which results in an increase in resistance locally in the electrode body, and the discharge characteristics are prone to deterioration. Fig.10 As shown, in the secondary battery according to the comparative example, when the electrode body is repeatedly charged and discharged, the electrical capacity is easily deteriorated.

[0083] On the other hand, in the secondary battery 100 including the separator 170 having the recessed portion 174 according to the present embodiment, the recessed portion 174 serves as a flow path for the electrolyte, and thus the electrolyte is easily impregnated into the electrode body 140, compared with the secondary battery according to the comparative example. Fig. 9 As shown, the electrolyte salt concentration is not easily uneven, so the increase in resistance is suppressed locally in the electrode body 140, thereby improving the discharge characteristics. The secondary battery 100 in this embodiment can maintain the desired voltage value for a long time compared to the secondary battery in the comparative example. Fig.10 As shown, the electrolyte salt concentration is less likely to vary, so when the electrode body 140 is repeatedly charged and discharged, the deterioration of the electric capacity is suppressed. Compared with the secondary battery in the comparative example, the secondary battery 100 in this embodiment has slower deterioration of the electric capacity even when the charge and discharge cycles are repeated.

[0084] In the secondary battery 100 according to the first embodiment of the present technology, the recess 174 is provided in the first region R1 of the separator 170 including the first end 171 and the second end 172, so that the electrolyte can be easily flowed into the inside of the electrode body 140 through the recess 174. The cross-sectional area of ​​the recess 174 is relatively large in the first region R1 located on the end side of the electrode body 140, and the cross-sectional area of ​​the recess 174 is relatively small in the second region R2 located on the center side of the electrode body 140, thereby making it easy for the electrolyte to flow into the end side of the electrode body 140, and ensuring the strength of the separator 170 on the center side of the electrode body 140 that is easy to bear the load when the electrode body 140 expands. As a result, it is possible to achieve both impregnation of the electrolyte into the inside of the electrode body 140 and ensuring the strength of the separator 170.

[0085] In the secondary battery 100 involved in embodiment 1 of the present technology, the area occupied by the recessed portion 174 when viewed from the thickness direction (Y direction) on the central side of the electrode body 140 is relatively reduced, thereby ensuring the strength of the diaphragm 170 in the central portion 173 of the electrode body 140 where the electrode body 140 is prone to expansion and where the strength of the diaphragm 170 is required.

[0086] In the secondary battery 100 involved in embodiment 1 of the present technology, even if the electrode body 140 is long in the first direction (X direction), the electrolyte can flow into the interior of the electrode body 140 from the recess 174, so that the electrolyte can be impregnated into the interior of the electrode body 140 and the strength of the diaphragm 170 can be ensured.

[0087] In the secondary battery 100 according to the first embodiment of the present technology, the electrolyte solution flowing into the recessed portion 174 can be easily flowed by forming the groove portion 175 extending from the first end portion 171 to the second end portion 172 of the separator 170 .

[0088] In the secondary battery 100 involved in embodiment 1 of the present technology, the average depth of the recess 174 in the first region R1 of the diaphragm 170 is greater than the average depth of the recess 174 in the second region R2 of the diaphragm 170, so that the strength of the diaphragm 170 can be easily ensured in the second region R2 including the central part 173 of the electrode body 140 where the expansion amount of the electrode body 140 is larger.

[0089] In the secondary battery 100 according to the first embodiment of the present technology, the recessed portions 174 are provided at both ends of the wound electrode body in the direction of the winding axis A where the electrolyte mainly flows, so that the electrolyte can be easily impregnated into the wound electrode body.

[0090] The following describes the secondary batteries according to Embodiments 2 and 3 of the present technology. The structure of the recessed portion of the separator of the secondary batteries according to these embodiments is different from that of the secondary battery 100 according to Embodiment 1 of the present technology, and therefore the same structure as that of the secondary battery 100 according to Embodiment 1 of the present technology will not be described repeatedly.

[0091] (Implementation Method 2)

[0092] Fig.11 1 is a plan view showing the structure of a separator included in an electrode body of a secondary battery according to Embodiment 2 of the present technology. Fig.11 As shown, the separator 170C in this embodiment includes a plurality of holes 176C as the recessed portion 174C. The plurality of holes 176C are arranged in the first direction (X direction) and the Z direction. The plurality of holes 176C are square in shape when viewed from the thickness direction (Y direction) of the electrode body.

[0093] The plurality of holes 176C are arranged in the first region R1. The first region R1 and the second region R2 each occupy approximately 1 / 2 of the length of the diaphragm 170C in the first direction (X direction).

[0094] The recess 174C occupies a smaller area 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 plurality of holes 176C are arranged in the Z direction orthogonal to the first direction (X direction).

[0095] In the secondary battery according to the second embodiment of the present technology, the electrolyte flowing from the inside to the outside of the electrode body during charge is accumulated in the recess 174C including the plurality of holes 176C, and the electrolyte accumulated in the plurality of holes 176C can be easily returned to the center during discharge.

[0096] (Implementation 3)

[0097] Fig.12 1 is a plan view showing the structure of a separator included in an electrode body of a secondary battery according to Embodiment 3 of the present technology. Fig.12 As shown, the separator 170D in this embodiment includes a plurality of holes 176D as the recessed portion 174D. The plurality of holes 176D are arranged in the first direction (X direction) and the Z direction. The plurality of holes 176D are circular when viewed from the thickness direction (Y direction) of the electrode body.

[0098] The plurality of holes 176D in the present embodiment are arranged in the first region R1. The first region R1 and the second region R2 each occupy approximately 1 / 2 of the length of the diaphragm 170D in the first direction (X direction).

[0099] In the secondary battery involved in embodiment 3 of the present technology, similar to embodiment 2, the electrolyte flowing from the inside to the outside of the electrode body during charging is accumulated in the recess 174D including the multiple holes 176D, so that the electrolyte accumulated in the multiple holes 176D can be easily returned to the center side during discharge.

[0100] Furthermore, in each of the above-described embodiments, the recessed portion is formed by either a groove portion or a hole, but the present invention is not limited to this structure, and the recessed portion may be formed by combining a groove portion and a hole.

[0101] The embodiments of the present invention have been described, but all points of the embodiments disclosed this time should be considered as illustrative and not limiting. The scope of the present invention is indicated by the claims, and is intended to include the meaning equivalent to the claims and all changes within the scope thereof.

Claims

1. A secondary battery, wherein: The secondary battery has: A flat electrode body, comprising a positive electrode plate, a separator and a negative electrode plate, wherein the separator is located between the positive electrode plate and the negative electrode plate; and a casing accommodating the electrode body and the electrolyte, When viewed from the thickness direction of the electrode body, the separator includes: a first region including a first end and a second end facing each other in a first direction orthogonal to the thickness direction; and a second region, sandwiched by the first region in the first direction and including a central portion of the diaphragm, A recessed portion is provided on the surface of the separator, the recessed portion is arranged at least in the first region and can allow the electrolyte to flow in. When viewed from the first direction, a cross-sectional area of ​​the recessed portion in the first region of the diaphragm is larger than a cross-sectional area of ​​the recessed portion in the second region of the diaphragm.

2. The secondary battery according to claim 1, wherein When viewed in the thickness direction, an area occupied by the recessed portion in the first region of the diaphragm is larger than an area occupied by the recessed portion in the second region of the diaphragm.

3. The secondary battery according to claim 1 or 2, wherein: The electrode body has a rectangular shape including a long side direction and a short side direction when viewed from the thickness direction, and the first direction is the long side direction of the electrode body.

4. The secondary battery according to claim 1 or 2, wherein: The recessed portion includes a groove portion extending along the first direction from the first end portion to the second end portion of the diaphragm.

5. The secondary battery according to claim 4, wherein An average depth of the recessed portions in the first region of the diaphragm is greater than an average depth of the recessed portions in the second region of the diaphragm.

6. The secondary battery according to claim 1 or 2, wherein: The recess includes a plurality of holes arranged in the first direction.

7. The secondary battery according to claim 1 or 2, wherein: The electrode body is a wound type electrode body in which the positive electrode plate, the separator, and the negative electrode plate are wound around an axis in the first direction.

Images