Battery cell, battery pack and energy storage system

Abstract

The invention provides a battery cell, a battery pack and an energy storage system. The battery cell comprises a shell and a roll core. The shell comprises two opposite first side plates and two opposite second side plates. The two first side plates are flat side plates. The roll core comprises two opposite first side surfaces and two opposite second side surfaces, the first side surfaces are flat side surfaces and are arranged towards the first side plate, and the second side surfaces are arc-shaped side surfaces and are arranged towards the second side plate. The second side plate is an arc-shaped side plate; or a plurality of pits are formed in the surfaces of the sides, facing the roll core, of the second side plates, and each second side plate is a flat side plate or an arc-shaped side plate. When the battery pack is charged, the volume of the roll core is expanded, and the arc-shaped side faces are in contact with the arc-shaped side plates, so that the arc-shaped side plates generate acting force perpendicular to the arc-shaped side faces on the arc-shaped side faces, and extrusion stress on the interiors of the arc-shaped side faces is reduced. The pits can increase the space between the side plates and the arc-shaped side faces, so that the extrusion stress of the second side plates on the arc-shaped side faces of the roll core is reduced when the roll core expands.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery pack, and an energy storage system. Background Art

[0002] Typically, in an energy storage battery pack, the core of the battery cell is formed by winding the positive electrode sheet, the separator, and the negative electrode sheet. During the charging process of the energy storage battery pack, the core will expand in volume as the negative electrode sheet expands. As the lithium insertion depth of the negative electrode material of the negative electrode sheet increases, the volume expansion of the core will become more obvious. For example, a negative electrode sheet made of graphite will typically produce a volume expansion of 10% to 15%, and a negative electrode sheet made of silicon-based material can produce a volume expansion of 300%. After the capacity is split, when the battery pack is charged, the core will gradually approach the inner wall of the aluminum shell of the battery cell during the volume expansion process. However, at the arc corners of the core, because the inner wall of the aluminum shell exerts forces in different directions on the arc surface of the core, when the stress on the core exceeds the yield strength of the negative electrode sheet, the negative electrode sheet will undergo plastic deformation, resulting in deformation and wrinkling, causing safety risks such as lithium deposition on the electrode sheet. Summary of the Invention

[0003] The present application provides a battery cell, a battery pack, and an energy storage system to reduce the stress of the pole pieces of the winding core, avoid wrinkling or brittle fracture of the pole pieces, and thus improve the safety of the battery pack.

[0004] In a first aspect, the present application provides a battery core. The battery core includes a shell and a winding core located in the shell. Specifically, the shell includes four side panels connected in sequence, and the four side panels include two first side panels arranged opposite to each other, and two second side panels arranged opposite to each other. The two first side panels are respectively flat side panels, and the area of ​​the two first side panels is greater than the area of ​​the two second side panels. The winding core includes four side panels connected in sequence, and the four side panels include two first side panels arranged opposite to each other, and two second side panels arranged opposite to each other, the two first side panels are respectively flat sides and are arranged facing the two first side panels, and the two second side panels are respectively curved sides and are arranged facing the two second side panels. The two second side panels may be curved side panels. Alternatively, a plurality of pits are provided on the surface of each of the two second side panels facing the winding core, and each second side panel may be a flat side panel or a curved side panel.

[0005] The battery cell of the present application is applied to a battery pack, and when the battery pack is charged, the negative electrode sheet of the roll core expands in volume. In one technical solution, the outer shell includes two flat side panels arranged opposite to each other and two curved side panels arranged opposite to each other, and the shape enclosed by the two flat side panels and the two curved side panels matches the side surface of the roll core. Therefore, when the roll core expands, the curved side surface of the roll core contacts the curved side panel of the outer shell, so that the curved side panel exerts a force perpendicular to the curved side surface on the curved side surface, thereby reducing the extrusion stress on the inside of the curved side surface, avoiding wrinkling or brittle fracture of the electrode sheet of the roll core, and thus improving the safety of the battery pack. In another technical solution, the second side panel of the outer shell can be a flat side panel or a curved side panel, and the inner wall of the second side panel facing the roll core is provided with a plurality of pits. In this technical solution, multiple pits can increase the space between the inner wall of the side plate and the side of the core to reserve space for the expansion of the core, so that when the core expands, the extrusion stress of the second side plate on the curved side of the core is reduced, thereby avoiding wrinkling or brittle fracture of the pole piece of the core, thereby improving the safety of the battery pack.

[0006] The housing is used to house the winding core and electrolyte. The housing can be made of aluminum alloy or stainless steel of a certain thickness. In one possible implementation, the thickness of the housing is 400 to 1000 microns. The housing can be easily formed into an arc shape, and recessed inner walls can also be formed through a pressing process.

[0007] When the inner wall of the second side plate is provided with a plurality of pits, the plurality of pits may be distributed in an array, or the plurality of pits may be distributed irregularly.

[0008] In a possible implementation, the depth of the pit is 50 microns to 200 microns. The pit of this depth can increase the space between the second side plate and the winding core, and at the same time prevent the shell from being too thin at the pit.

[0009] In one possible implementation, each of the two second side surfaces is provided with a cushioning pad, which covers each second side surface and is provided with a plurality of through holes. By wrapping the curved cushioning pad around the curved side surface area of ​​the winding core, the compression of the curved side surface by the second side plate can be reduced.

[0010] In one possible implementation, the radius of curvature of the cushion is equal to the radius of curvature of each second side surface, the height of the cushion is equal to the height of each second side surface, and the length of the cushion is greater than or equal to the arc length of each second side surface. In this way, the cushion matches the curved side surface of the winding core, thereby completely covering the second side surface of the winding core and improving protection for the second side surface.

[0011] In a possible implementation, the diameters of the plurality of through holes are in a range of 100 micrometers to 500 micrometers, so that the electrolyte contacts the curved side surfaces through the through holes.

[0012] In a possible implementation, the thickness of the buffer pad is 100 micrometers to 500 micrometers. The buffer pad within this thickness range can ensure the buffering effect on the second side surface while avoiding the buffer pad from occupying too much space.

[0013] In the present application, the material of the buffer pad is not limited, and may include, for example, rubber, vinyl elastomer, polyolefin elastomer or polyester elastomer.

[0014] In one possible implementation, the winding core includes a positive electrode sheet, a diaphragm and a negative electrode sheet. The diaphragm is located between the positive electrode sheet and the negative electrode sheet. A rubber layer is provided on the surface of the diaphragm facing the second side plate. The rubber layer has a buffering effect and can reduce the force of the second side plate on the curved side.

[0015] In one possible implementation, the adhesive layer includes a first side and a second side parallel to the height direction of the winding core. Of two adjacent adhesive layers along the length direction of the winding core, the first side of one adhesive layer has a first projection on the curved surface of the other adhesive layer, and the distance between the first projection and the first side of the other adhesive layer is less than or equal to 0.5 mm. The second side of the one adhesive layer has a second projection on the curved surface, and the distance between the second projection and the second side of the other adhesive layer is less than or equal to 0.5 mm.

[0016] In one possible implementation, the coating density of the adhesive layer is 2 g / m 2 -6g / m 2 .

[0017] In the present application, the material of the adhesive layer is not specifically limited, and can be, for example, one or any two of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, and polyacrylate.

[0018] In a second aspect, the present application further provides a battery pack. The battery pack specifically comprises a housing and at least one battery cell according to the first aspect, the battery cell being located within the housing. The battery cells within the battery pack are less susceptible to wrinkling or brittle fracture, thereby improving the safety of the battery pack.

[0019] In a third aspect, the present application further provides an energy storage system, which includes the battery pack and a power converter according to the second aspect, wherein the power converter is configured to convert the electrical energy outputted by an external power source into power and then output the power to the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of a battery pack provided in an embodiment of the present application;

[0021] Figure 2 A schematic diagram of a winding core provided in an embodiment of the present application;

[0022] Figure 3 A schematic diagram of a battery cell provided in an embodiment of the present application;

[0023] Figure 4 A schematic diagram of a housing provided in an embodiment of the present application;

[0024] Figure 5 Another schematic diagram of a battery cell provided in an embodiment of the present application;

[0025] Figure 6 for Figure 5 Schematic diagram of the middle shell;

[0026] Figure 7 Another schematic diagram of a battery cell provided in an embodiment of the present application;

[0027] Figure 8 for Figure 7 Schematic diagram of the middle shell;

[0028] Figure 9 A schematic diagram of a cushion provided in an embodiment of the present application;

[0029] Figure 10 Another schematic diagram of a battery cell provided in an embodiment of the present application;

[0030] Figure 11 Another schematic diagram of a winding core provided in an embodiment of the present application;

[0031] Figure 12 for Figure 11 Schematic diagram of the septum;

[0032] Figure 13 for Figure 12 Schematic diagram of the septum located in the arc area.

[0033] Reference numerals:

[0034] 10-Battery Pack

[0035] 11- Shell

[0036] 12-battery cells

[0037] 121-Core

[0038] 122-Shell

[0039] 123-Buffer

[0040] 1211-Positive electrode

[0041] 1212-diaphragm

[0042] 1213-Negative electrode

[0043] 1214-Glue layer

[0044] 1221-First side panel

[0045] 1222-Second side panel

[0046] 1223-Pit

[0047] 1231-Through hole

[0048] A-First Surface

[0049] B-Second Surface

[0050] S1-First side

[0051] S2-Second side DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of this application clearer, this application will be further described in detail below with reference to the accompanying drawings.

[0053] It should be noted that the terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and claims of this application, the singular expressions "a," "an," "said," "above," "the," and "this" are intended to include expressions such as "one or more," unless the context clearly indicates otherwise.

[0054] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in yet other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0055] In order to facilitate the understanding of the battery cells, battery packs and energy storage systems provided in the embodiments of the present application, their application scenarios are explained below. The energy storage system of the present application can be used in multiple application scenarios of industrial and commercial energy storage and power station energy storage. Industrial and commercial energy storage may, for example, include small-scale industrial and commercial (small factories, etc.) energy storage, medium-sized industrial and commercial energy storage, large-scale industrial and commercial energy storage, photovoltaic storage and charging station energy storage, small and medium-sized microgrid (island, etc.) energy storage, etc. Power station energy storage may, for example, include wind and solar storage power stations, grid storage power stations, large microgrid power stations, etc. In addition, energy storage equipment can also be used in application scenarios such as data centers and vehicle charging stations. The energy storage equipment contains a power converter and at least one battery pack, and the power converter is used to convert the electric energy output by the external power supply into power and output it to the aforementioned at least one battery pack. Figure 1 Schematic diagram of the battery pack provided in the embodiment of the present application. Figure 1 As shown, the battery pack 10 may include a housing 11, which contains at least one battery cell 12. In the present application, the battery cell 12 includes a housing, a winding core 121 located within the housing, and an electrolyte, wherein the electrode of the winding core 121 is immersed in the electrolyte. Figure 2 This is a schematic diagram of a winding core provided in an embodiment of the present application. Figure 2 As shown, the winding core 121 is typically cylindrical, with a cross-section perpendicular to the axial direction forming an irregular elliptical shape. Along the circumferential direction, the winding core 121 includes two opposing and parallel flat sides and two opposing curved sides. When the battery pack 10 is charged, the winding core 121 expands in volume and gradually approaches the inner wall of the outer casing. In particular, the expansion of the negative electrode sheet in the thickness direction compresses the space in the curved side areas.

[0056] However, because the inner wall of the casing exerts forces in different directions on the curved surface of the winding core 121, when the stress on the winding core 121 exceeds the yield strength of the negative electrode sheet, the negative electrode sheet is constrained by the casing, causing stress to concentrate and squeeze the curved side areas, and then spread to the flat side areas. The negative electrode sheet is constrained in the curved side areas and undergoes plastic deformation, resulting in deformation and wrinkling, which may cause safety risks such as lithium deposition on the electrode sheet.

[0057] Therefore, the present application provides a battery cell, battery pack, and energy storage system to reduce the stress on the electrode sheets of the winding core, avoid wrinkling or brittle fracture of the electrode sheets, and thus improve the safety of the battery pack. The following describes a battery cell, battery pack, and energy storage system provided by exemplary embodiments of the present application in conjunction with the application scenarios of the present application and with reference to the accompanying drawings.

[0058] Figure 3 A schematic diagram of a battery cell provided in an embodiment of the present application is shown. Figure 4 A schematic diagram of a housing provided in an embodiment of the present application. Figure 3 and Figure 4As shown, the battery cell 12 includes a shell 122 and a winding core 121 located in the shell 122. Specifically, the shell 122 is cylindrical and includes four side panels connected in sequence. The four side panels include two first side panels 1221 arranged opposite to each other, and two second side panels 1222 arranged opposite to each other, wherein the two first side panels 1221 are flat side panels, and the area of ​​the two first side panels 1221 is larger than the area of ​​the two second side panels 1222. Figure 2 As shown, the winding core 121 includes four side surfaces connected in sequence, and the four side surfaces include two first side surfaces S1 arranged opposite to each other, and two second side surfaces S2 arranged opposite to each other. The two first side surfaces S1 are flat side surfaces and are respectively arranged toward the first side plate 1221, and the two second side surfaces S2 are curved side surfaces and are respectively arranged toward the second side plate 1222. Figure 3 and Figure 4 As shown, in one embodiment, the two second side plates 1222 are respectively arc-shaped side plates. That is, the cross-section of the outer shell 122 perpendicular to the axial direction is an irregular ellipse, so that the inner wall of the outer shell 122 matches the shape of the core 121. Since the shape of the outer shell 122 in the arc-shaped side area is also arc-shaped, when the core 121 expands, the second side plate 1222 generates a force on the second side surface S2 of the core 121. The force is perpendicular to the tangent of the arc-shaped side surface (i.e., the point of action), thereby reducing the extrusion stress on the inside of the arc-shaped side surface, avoiding wrinkles or brittle fractures of the core 121, and thus improving the safety of the battery pack 10. Figure 5 This is another schematic diagram of a battery cell provided in an embodiment of the present application. Figure 6 for Figure 5 Schematic diagram of the middle shell, where Figure 6 Schematic diagrams of the inner walls of the two second side panels of the housing are shown respectively. Figure 5 and Figure 6 As shown, in another embodiment, the two second side plates 1222 are respectively flat side plates, that is, the outer shell 122 can be a square outer shell. In the curved side area, a plurality of pits 1223 are provided on the surface of each second side plate 1222 of the two second side plates 1222 facing the core 121. In this embodiment, the pits 1223 can increase the space between the inner wall of the side plate of the outer shell 122 and the side of the core 121 to reserve space for the expansion of the core 121, so as to reduce the asymmetric shear stress generated on the contact surface between the core 121 and the outer shell 122 when the core 121 expands, thereby reducing the extrusion stress of the second side plate 1222 on the inner side of the curved side of the core 121, avoiding the phenomenon of wrinkling or brittle fracture of the pole piece of the core 121, and thereby improving the safety of the battery pack 10. Figure 7 This is another schematic diagram of a battery cell provided in an embodiment of the present application. Figure 8 for Figure 7 Schematic diagram of the housing. Figure 7 and Figure 8 As shown, in another embodiment, the two second side plates 1222 are respectively arc-shaped side plates. Moreover, in the arc-shaped side area, a plurality of pits 1223 are provided on the surface of each second side plate 1222 of the two second side plates 1222 facing the core 121. In this embodiment, the inner wall of the outer shell 122 matches the shape of the core 121, and the pits 1223 can increase the space between the inner wall of the side plate of the outer shell 122 and the side of the core 121, thereby reducing the extrusion stress of the second side plate 1222 on the inner side of the arc-shaped side of the core 121 when the core 121 expands, avoiding the phenomenon of wrinkling or brittle fracture of the pole piece of the core 121, and thereby improving the safety of the battery pack 10.

[0059] The housing 122 is used to house the winding core and electrolyte. The housing 122 can be made of aluminum alloy or stainless steel of a certain thickness. In one possible implementation, the thickness of the housing 122 is 400 to 1000 microns. The housing 122 can be easily formed into an arc shape, and the inner wall recess 1223 can also be formed through a pressing process.

[0060] Within the shell 122, the multiple pits 1223 on the inner wall of the second side plate 1222 can be distributed in an array or irregularly. The depth of the pits 1223 is 50 microns to 200 microns, which can increase the space between the second side plate 1222 and the winding core 121 while preventing the shell 122 from being too thin at the pits 1223. During actual manufacturing, an embossing roller (convex on top and flat on the bottom) or a convex-concave roller (including an upper embossing roller and a lower embossing roller, the upper embossing roller having multiple protrusions and the lower embossing roller having multiple grooves, with the protrusions and grooves being matched one to one, and the protrusions being able to extend into the grooves) can be used to apply pressure to the shell 122, thereby pressing out the pits 1223 of the aforementioned depth. In order to press out the pits 1223 of the aforementioned depth, the applied pressure can be 0.5 MPa to 1 MPa. In the present application, the shape of the pit 1223 is not limited and may be circular, elliptical, diamond-shaped, rectangular or polygonal, etc., and the shapes of the above-mentioned multiple pits 1223 may be the same or different.

[0061] Figure 9 A schematic diagram of a buffer pad provided in an embodiment of the present application, Figure 10 This is another schematic diagram of the battery cell provided in the embodiment of the present application. Figure 9 and Figure 10As shown, in one embodiment, each of the two second side surfaces S2 is provided with a buffer pad 123, the buffer pad 123 covers each second side surface S2, and the buffer pad 123 is provided with a plurality of through holes 1231. By wrapping the arc-shaped buffer pad 123 in the arc-shaped side area of ​​the winding core 121, the extrusion of the arc-shaped side surface by the inner wall of the shell 122 can be reduced. In practical applications, the buffer pad 123 is made of an organic polymer material, for example, it can be a rubber (such as natural / synthetic rubber, silicone rubber), vinyl elastomer, polyolefin elastomer and polyester elastomer. Specifically, when the buffer pad 123 is a rubber buffer pad 123, materials such as styrene-butadiene rubber, vinyl chloride rubber, fluororubber or EPDM rubber can be used.

[0062] In the above-mentioned battery cell 12, the buffer pad 123 wraps the curved side surface of the core 121, and the electrolyte can contact the curved side surface of the core 121 through the through hole 1231. Among the above-mentioned multiple through holes 1231, the shape of each through hole 1231 is not limited, for example, it can be circular, elliptical, diamond-shaped, rectangular or polygonal. In the above-mentioned embodiment, the diameter of the above-mentioned multiple through holes 1231 can be 100 microns to 500 microns, so that the electrolyte can contact the curved side surface through the through hole 1231. In addition, the thickness of the buffer pad 123 can be 100 microns to 500 microns. The buffer pad 123 in this thickness range can not only ensure the buffering effect on the second side surface S2, but also avoid the buffer pad 123 occupying too much space.

[0063] In one embodiment, the radius of curvature of the cushion 123 is equal to the radius of curvature of each second side surface S2, the height of the cushion 123 is equal to the height of each second side surface S2, and the length of the cushion 123 is greater than or equal to the arc length of each second side surface S2. In this way, the cushion 123 can completely wrap around the second side surface S2 without affecting the installation of the tab on the top surface of the core 121. During actual installation of the cushion 123, the cushion 123 can be secured to the core 121 using adhesive tape.

[0064] Figure 11 Another schematic diagram of the winding core provided in an embodiment of the present application, Figure 12 for Figure 11 Schematic diagram of the diaphragm, where Figure 11 Showing the top surface of the core, Figure 12 Figure 2 shows the expanded schematic diagram of the diaphragm. Figure 11 and Figure 12 As shown, in one embodiment, the winding core 121 includes a positive electrode sheet 1211, a separator 1212 and a negative electrode sheet 1213. The separator 1212 is located between the positive electrode sheet 1211 and the negative electrode sheet 1213. The positive electrode sheet 1211, the separator 1212 and the negative electrode sheet 1213 are wound and formed into a cylindrical shape. A glue layer 1214 is provided on the side surface of the separator 1212 facing the second side plate 1222. Figure 12As shown, the curved diaphragm segment provided with the adhesive layer 1214 is located in the curved region of the winding core 121, and the flat diaphragm segment between two adjacent adhesive layers 1214 is located in the flat region of the winding core 121. In this embodiment, taking the curved diaphragm segment of the diaphragm 1212 located in the curved region as an example, the curved diaphragm segment has a first surface A facing one of the second side plates 1222, and a second surface B facing the axis of the winding core 121. In one embodiment, the first surface A may be provided with the adhesive layer 1214, while the second surface B is not provided with the adhesive layer 1214. In another embodiment, the first surface A is not provided with the adhesive layer 1214, while the second surface B may be provided with the adhesive layer 1214. In another embodiment, the first surface A may be provided with the adhesive layer 1214, while the second surface B may be provided with the adhesive layer 1214. In another embodiment, the first surface A may be provided with the adhesive layer 1214, while the second surface B may be provided with the adhesive layer 1214.

[0065] When the adhesive layer 1214 is specifically made, a polymer binder, a dispersant and a solvent can be prepared into a liquid phase mixture, and a coating amount of a set surface density is applied to the surface of the diaphragm 1212 by a coating process. After drying in an oven with hot air (a temperature of 100 degrees Celsius to 120 degrees Celsius), an adhesive layer 1214 is formed on the surface of the diaphragm 1212. In this embodiment, the polymer binder can include any one or a combination of any two of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polyacrylate (PMMA). In addition, the above-mentioned coating process can be any one or more combinations of spray coating, anilox roller transfer coating, and electrostatic spinning coating. For example, in a specific implementation, a combination of spray coating and anilox transfer coating, a combination of anilox coating and electrostatic spinning coating, a combination of spray coating, anilox coating and electrostatic spinning coating, etc. can be used. In other embodiments, the coating process may also include gravure, micro-gravure, and electrospinning coating methods. In the above embodiment, the coating surface density of the adhesive layer 1214 is 2 g / m 2 -6 g / m 2 For example, the coating surface density of the adhesive layer 1214 can be 2g / m 2 , 2.3g / m 2 , 2.9g / m 2 3.2g / m 2 3.5g / m 2 , 4g / m 2 , 4.2g / m 2 , 4.6g / m 2 , 5.4g / m 2 , 5.82g / m 2 , or 6g / m 2 .

[0066] Figure 13 for Figure 12 Schematic diagram of the diaphragm located in the arc area, where Figure 13 The top of the diaphragm is shown. Figure 13 As shown, in one embodiment, the adhesive layer 1214 includes a first side L1 and a second side L2 parallel to the height direction of the core 121. Of two adjacent adhesive layers 1214 along the length direction of the core 121, the spacing d1 between the first side L1 of one adhesive layer 1214 (e.g., the adhesive layer 1214 located on the first surface A) and the first side L1 of the other adhesive layer 1214 (e.g., the adhesive layer 1214 located on the second surface B) along the circumferential direction of the core 121 is less than or equal to 0.5 mm, and the spacing d2 between the second side L2 of one adhesive layer 1214 and the second side L2 of the other adhesive layer 1214 along the circumferential direction of the core 121 is less than or equal to 0.5 mm. In other words, the adhesive layers 1214 on both sides of the second winding portion may be staggered, with the staggered spacing being less than or equal to 0.5 mm. Of course, in other embodiments, one adhesive layer 1214 and another adhesive layer 1214 may also be arranged alternately, that is, the projection of one adhesive layer 1214 on the arc surface where the other adhesive layer 1214 is located partially overlaps or does not overlap with the other adhesive layer 1214.

[0067] In the present application, the material of the adhesive layer 1214 is not specifically limited, and can be, for example, one or any two of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, and polyacrylate.

[0068] Table 1 below uses a 280 Ah battery pack 10 as an example. In this battery pack 10, the core 121 has 25 winding layers. The thickness of the positive electrode sheet 1211 is 0.154 mm, and the thickness of the negative electrode sheet 1213 is 0.127 mm. The core 121 is 169 mm wide, 16 mm thick, and 196 mm tall. In the curved area, the height of the adhesive layer 1214 is 196 mm. The lengths of the adhesive layer 1214 along the circumference of the core 121 are: 6 mm, 6.8 mm, 7.6 mm, 8.4 mm, ..., 22.8 mm, 23.6 mm, 24.4 mm, ..., 25.2 mm. The lengths of the flat areas are: 312 mm, 314 mm, 316 mm, 318 mm, ..., 354 mm, 356 mm, 358 mm, ..., 360 mm.

[0069] Table 1

[0070] Sequence number of the blank area of ​​the diaphragm Length of diaphragm blank area / mm Sequence number of diaphragm glue coating area Length of diaphragm coating area / mm 1 312 1 6 2 314 2 6.8 3 316 3 7.6 4 318 4 8.4 …… …… …… …… 22 354 22 22.8 23 356 23 23.6 24 358 24 24.4 25 360 25 25.2

[0071] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A battery cell, characterized in that: The invention comprises a shell and a winding core located in the shell, wherein: The housing includes four side panels connected in sequence, the four side panels including two first side panels arranged opposite to each other, and two second side panels arranged opposite to each other, the two first side panels are respectively flat side panels, and the areas of the two first side panels are larger than the areas of the two second side panels; The winding core includes four side surfaces connected in sequence, the four side surfaces including two first side surfaces arranged opposite to each other, and two second side surfaces arranged opposite to each other, the two first side surfaces are respectively flat side surfaces and arranged toward the two first side panels, and the two second side surfaces are respectively curved side surfaces and arranged toward the two second side panels; The two second side plates are arc-shaped side plates; or, a surface of each of the two second side plates facing the winding core is provided with a plurality of pits, and each of the second side plates is a flat side plate or an arc-shaped side plate.

2. The battery cell according to claim 1, wherein: The thickness of the shell is 400 microns to 1000 microns.

3. The battery cell according to claim 1 or 2, characterized in that: The plurality of pits are distributed in an array.

4. The battery cell according to any one of claims 1 to 3, characterized in that The depth of the pit is 50 microns to 200 microns.

5. The battery cell according to any one of claims 1 to 4, characterized in that A buffer pad is provided on each of the two second side surfaces, the buffer pad covers each of the second side surfaces, and the buffer pad is provided with a plurality of through holes.

6. The battery cell according to claim 5, characterized in that The curvature radius of the buffer pad is equal to the curvature radius of each second side surface, the height of the buffer pad is equal to the height of each second side surface, and the length of the buffer pad is greater than or equal to the arc length of each second side surface.

7. The battery cell according to claim 5 or 6, characterized in that: The diameters of the plurality of through holes are in a range of 100 micrometers to 500 micrometers.

8. The battery cell according to any one of claims 5 to 7, characterized in that: The thickness of the buffer pad is 100 microns to 500 microns.

9. The battery cell according to any one of claims 5 to 8, characterized in that The material of the buffer pad includes rubber, vinyl elastomer, polyolefin elastomer or polyester elastomer.

10. The battery cell according to any one of claims 1 to 9, characterized in that The winding core includes a positive electrode sheet, a separator and a negative electrode sheet. The separator is located between the positive electrode sheet and the negative electrode sheet. A glue layer is provided on a surface of the separator facing the two second side plates.

11. The battery cell according to claim 10, wherein: The adhesive layer includes a first side edge and a second side edge parallel to the height direction of the winding core; Among the two adhesive layers adjacent to each other along the length direction of the core, the first side edge of one of the adhesive layers has a first projection on the arc surface where the other adhesive layer is located, and the distance between the first projection and the first side edge of the other adhesive layer is less than or equal to 0.5 mm; the second side edge of one of the adhesive layers has a second projection on the arc surface, and the distance between the second projection and the second side edge of the other adhesive layer is less than or equal to 0.5 mm.

12. The battery cell according to claim 10 or 11, characterized in that: The coating surface density of the adhesive layer is 2g / m 2 -6g / m 2 .

13. The battery cell according to any one of claims 10 to 12, characterized in that: The material of the adhesive layer includes one or any two of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, and polyacrylate.

14. A battery pack, characterized in that: The invention comprises a shell and at least one battery cell according to any one of claims 1 to 13, wherein the at least one battery cell is located in the shell.

15. An energy storage system, characterized in that: The energy storage system includes the battery pack as claimed in claim 14 and a power converter, wherein the power converter is used to convert the electric energy output by an external power source and output the converted electric energy to the battery pack.

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