Battery cells, energy storage devices and electrical equipment

Abstract

The present application provides a battery cell, an energy storage device, and an electrical appliance. The battery cell is wound by a first electrode, a diaphragm, and a second electrode. Along the winding direction of the first electrode, the first electrode includes a hollow foil segment and a first starting segment connected to the hollow foil segment. The hollow foil segment is bent relative to the first starting segment, and the straight portion of the hollow foil segment and the straight portion of the first starting segment are spaced apart along the thickness direction of the battery cell. Along the winding direction of the second electrode, the second electrode includes a second starting segment; wherein the first starting segment exceeds the second starting segment in the opposite direction of the winding direction of the first electrode. The hollow foil segment includes a body and a stamping portion. The stamping portion is connected to the body and includes a raised surface. Along the thickness direction of the body, the raised surface protrudes relative to the body. The stamping portion is provided with a groove, and the opening of the groove is provided on the surface of the stamping portion facing away from the raised surface. The battery cell provided by the present application can improve the cycle performance of the battery cell by providing a hollow foil segment and providing a stamping portion on the hollow foil segment.

Description

Technical Field

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

[0002] Existing battery cells are typically formed by winding a cathode sheet, an anode sheet, and a separator. They are widely used in portable electronic devices and other fields. Cycling performance is a key indicator of battery performance in these applications. Therefore, improving the cycling performance of battery cells is of great significance. Summary of the Invention

[0003] The purpose of the embodiments of the present application is to provide a battery cell, an energy storage device, and an electrical device that can improve the cycle performance of the battery cell.

[0004] The present application provides a battery cell, which is formed by winding a first electrode piece, a diaphragm, and a second electrode piece. The diaphragm is provided between the first electrode piece and the second electrode piece. Along the winding direction of the first electrode piece, the first electrode piece includes a hollow foil segment and a first starting segment connected to the hollow foil segment. The hollow foil segment and the first starting segment both include a straight portion. The straight portion of the hollow foil segment and the straight portion of the first starting segment are spaced apart along the thickness direction of the battery cell. Along the winding direction of the second electrode piece, the second electrode piece includes a second starting segment. The second starting segment is located on a side of the first starting segment facing away from the hollow foil segment.

[0005] Among them, the first starting section exceeds the second starting section in the opposite direction of the winding direction of the first pole piece. The empty foil section includes a main body and a stamping portion. The stamping portion is connected to the main body and includes a raised surface. Along the thickness direction of the main body, the raised surface protrudes relative to the main body. The stamping portion is provided with a groove, and the opening of the groove is provided on the surface of the stamping portion away from the raised surface.

[0006] In the battery cell provided in the embodiment of the present application, by providing an empty foil segment in the first electrode sheet and providing a stamping portion in the empty foil segment, on the one hand, the groove provided in the stamping portion in the empty foil segment can store electrolyte when the battery cell is injected, and when the outer shell is subjected to force to squeeze the battery cell, the electrolyte in the groove is not easily squeezed out, so that in the middle and late stages of the battery cell cycle, when the electrolyte inside the winding of the first electrode sheet is exhausted, the electrolyte stored in the groove can be replenished to the first electrode sheet in time to ensure that the transmission path of lithium ions is unobstructed, thereby improving the cycle performance of the battery cell. On the other hand, compared with other methods of improving the cycle performance of the battery cell, the embodiment of the present application can improve the cycle performance of the battery cell by adding the process step of providing the stamping portion, without the need to increase the material cost, which is beneficial to reducing the production cost of the battery cell. In addition, the empty foil segment does not contain active materials, which is equivalent to saving the cost of active materials, thereby further reducing the production cost of the battery cell.

[0007] Furthermore, the straight portion of the hollow foil segment is spaced apart from the straight portion of the first starting segment in the thickness direction of the battery cell, which is equivalent to increasing the thickness of the first electrode sheet within the space inside the battery cell. This reduces the curvature of the second electrode sheet at the winding corner when the second electrode sheet is wound around the first electrode sheet, thereby reducing the risk of active layer material falling off the second electrode sheet and even breaking. Furthermore, due to the large area and thin thickness of the hollow foil segment, the surface stress of the hollow foil segment can easily cause the hollow foil segment to curl, thereby affecting the winding efficiency of the hollow foil segment and even directly folding the hollow foil segment, resulting in uneven thickness of the hollow foil segment. By providing a stamped portion on the hollow foil segment, the surface stress distribution of the hollow foil segment can be greatly improved, reducing the risk of curling of the hollow foil segment.

[0008] In addition, by setting the first starting section of the first pole piece to extend beyond the second starting section of the second pole piece in the opposite direction of the winding direction of the first pole piece, an excess coefficient of the first pole piece to the second pole piece is created, so that the first pole piece has sufficient lithium insertion positions to ensure that lithium is not deposited.

[0009] In one possible embodiment, the main body includes a first surface and a second surface arranged opposite to each other along the thickness direction, the first surface faces the second starting section, and the second surface faces away from the second starting section. There are multiple stamped parts, and along the width direction of the battery cell, the multiple stamped parts include a first stamped part and a second stamped part. The convex surface of the first stamped part protrudes relative to the first surface of the main body, and the convex surface of the second stamped part protrudes relative to the second surface of the main body.

[0010] In a possible implementation manner, the plurality of first embossing portions and the plurality of second embossing portions are arranged alternately.

[0011] In one possible embodiment, there are multiple stamped parts along the direction from the bottom to the top of the battery cell, and the openings of the grooves of the multiple stamped parts gradually increase, so that the grooves of the stamped parts near the top cover in the assembled energy storage device can store more electrolyte for replenishing the electrolyte, maintaining the smooth transmission path of lithium ions, and thus improving the cycle performance of the energy storage device.

[0012] In a possible implementation manner, a height H of the raised surface of the embossing portion relative to the main body is 5 μm≤H≤50 μm.

[0013] In a possible embodiment, the first starting segment further includes a bent portion, and the bent portion of the first starting segment is connected between the straight portion of the empty foil segment and the straight portion of the first starting segment; or, the empty foil segment further includes a bent portion, and the bent portion of the empty foil segment is connected between the straight portion of the empty foil segment and the straight portion of the first starting segment; or, the first starting segment and the empty foil segment both include a bent portion, the bent portion of the first starting segment is connected to the straight portion of the first starting segment, and the bent portion of the empty foil segment is connected to the straight portion of the empty foil segment, and is connected to the end of the bent portion of the first starting segment facing away from the straight portion of the first starting segment.

[0014] In one possible embodiment, the battery cell includes two first surfaces and two second surfaces, the two first surfaces are arranged opposite to each other along a thickness direction of the battery cell, and the two second surfaces are arranged opposite to each other along a width direction of the battery cell;

[0015] The first pole piece also includes a first tail section, the first tail section and the first starting section are arranged opposite to each other along the winding direction of the first pole piece, the first tail section includes a first tail end face, the first tail end face is arranged along the winding direction of the first tail section and away from the first starting section, the first tail section ends at a second face, and the first tail end face is located between the two first faces, so that the first tail section of the first pole piece does not go up to the first face of the battery cell, avoiding the first tail section of the first pole piece from going up to the first face making the first tail end face of the first tail section the highest point of the entire first face, on the one hand, while maintaining While ensuring that the capacity of the battery cell can be normally utilized, the thickness of the battery cell is avoided from being increased, thereby helping to reduce the thickness margin of the energy storage device formed by the assembly of the battery cells. On the other hand, during the process of hot pressing or cold pressing to form the battery cell, as well as when the cycle battery cell touches the shell, the battery cell is prevented from being subjected to external forces and causing stress points to be generated at the position of the first tail section, which is then transmitted to the inner layers of the battery cell, causing the electrolyte at the stress point to be squeezed out of the electrode, resulting in poor electrolyte infiltration, thereby causing the current density around the stress point to be too large, resulting in purple spots or lithium precipitation problems in the battery cell.

[0016] In one possible embodiment, the second surface is a curved surface, and the second surface has a widest position. The second electrode sheet also includes a second tail section, which is arranged opposite to the second starting section along the extension direction of the second electrode sheet. The second tail section includes a second tail end face, which is arranged along the extension direction of the second tail section and away from the second starting section. The second tail section ends at a second surface, and the second tail end face does not exceed the widest position, so that the tail of the second electrode sheet does not exceed the widest part of the battery cell, thereby avoiding the second tail section of the second electrode sheet exceeding the widest position of the second surface, resulting in an increase in the winding thickness of the battery cell in the width direction. On the one hand, while ensuring that the battery cell capacity can be normally exerted, the width of the battery cell is avoided from being increased, thereby facilitating reducing the width skirt margin of the energy storage device formed by assembling the battery cells, and avoiding the problem that high-energy-density lithium-ion energy storage devices with a relatively extreme design of the width skirt margin make it difficult for the battery cell to be inserted into the shell. After the battery cell is installed in the shell, the shell is more easily squeezed on both sides in the width direction, thereby increasing the risk of "S"-shaped deformation of the battery cell.

[0017] In a possible implementation, the second ending segment and the first ending segment end at the same second surface, and along the winding direction of the battery cell, the first ending end surface of the first ending segment exceeds the second ending end surface of the second ending segment.

[0018] In a possible implementation, in the winding direction of the battery cell, a length L by which the first end face exceeds the second end face, and L is ≥ 3.5 mm.

[0019] An embodiment of the present application further provides an energy storage device, comprising a housing and at least one battery cell as described above, wherein the battery cell is installed on the inner side of the housing.

[0020] In a possible implementation, the energy storage device satisfies: 85%≤D2 / D1≤105%, where D1 represents the inner diameter of the housing along the thickness direction, and D2 represents the total length of the battery cell along the thickness direction.

[0021] In a possible implementation, there are two battery cells, and the two battery cells are installed on the inner side of the housing along the thickness direction of the battery cells.

[0022] An embodiment of the present application further provides an electrical device, comprising the energy storage device as described above, wherein the energy storage device is used to supply power to the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 An application scenario diagram of the energy storage device provided in an embodiment of the present application;

[0025] Figure 2 A side view of the energy storage device provided in the first embodiment of the present application;

[0026] Figure 3 for Figure 2 A schematic cross-sectional view of the energy storage device shown;

[0027] Figure 4 for Figure 3 A schematic diagram of the exploded structure of the energy storage device before assembly;

[0028] Figure 5 for Figure 2 A schematic diagram of the cross-sectional structure of a battery cell in the energy storage device shown;

[0029] Figure 6 for Figure 4 A schematic diagram of the top view of the hollow foil segment of the battery cell shown;

[0030] Figure 7 for Figure 6 Schematic diagram of the cross-sectional structure of the empty foil segment at CC;

[0031] Figure 8 A schematic cross-sectional view of the energy storage device provided in the second embodiment of the present application;

[0032] Figure 9 This is a schematic cross-sectional structural diagram of the energy storage device provided in the third embodiment of the present application.

[0033] Reference numerals: energy storage system 5000, electric energy conversion device 4500, wind energy conversion device 4000, second electric device 3000, energy storage device 1000, housing 100, bottom housing 110, side housing 130, top cover 200, battery cell 300, first pole piece 310, second pole piece 330, diaphragm 350, first current collector 301, first active layer 303, first starting section 10, straight portion 11, bent portion 13, first starting end face 15, first middle section 20, first ending section 30, first ending end face 31, empty foil section 40, this Body 41, first surface 411, second surface 413, straight portion 42, stamped portion 43, first stamped portion 431, second stamped portion 433, bent portion 44, raised surface 45, groove 46, second current collector 305, second active layer 307, second starting section 50, second starting end face 51, second middle section 60, second ending section 70, second ending end face 71, starting film segment 80, middle film segment 91, ending film segment 92, first pole ear 360, second pole ear 370, first surface 380, second surface 390, corner position A, widest position B. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] Taking electrochemical energy storage as an example, this solution provides an energy storage device with a group of chemical batteries inside. The energy storage device mainly uses the chemical elements in the chemical batteries as energy storage media. The charging and discharging process is accompanied by chemical reactions or changes in the energy storage medium. Simply put, the electricity generated by wind and solar energy is stored in the chemical batteries. When the use of external electricity reaches its peak, the stored electricity is released for use, or transferred to places where electricity is scarce for use.

[0036] Currently, energy storage (i.e., energy storage) has a wide range of application scenarios, including (wind and solar) power generation-side energy storage, grid-side energy storage, base station-side energy storage, and user-side energy storage. The corresponding energy storage device types include:

[0037] (1) Large energy storage containers used in grid-side energy storage scenarios can serve as high-quality active and reactive power regulation power sources in the grid, achieving load matching of electricity in time and space, enhancing the ability to absorb renewable energy, and are of great significance in grid system backup, alleviating peak load power supply pressure, and peak and frequency regulation;

[0038] (2) Small and medium-sized energy storage cabinets used in industrial and commercial energy storage scenarios (banks, shopping malls, etc.) on the user side mainly operate in the "peak shaving and valley filling" mode. Since there is a large price difference in electricity prices at peak and valley locations according to electricity demand, after users have energy storage equipment, in order to reduce costs, they usually charge the energy storage cabinets / boxes during the low electricity price period; during the peak electricity price period, they release the electricity in the energy storage equipment for use, thereby saving electricity costs.

[0039] It should be noted that the above-mentioned energy storage containers, small and medium-sized energy storage cabinets, household small energy storage boxes and other equipment containing energy storage devices can be understood as electrical equipment.

[0040] See also Figure 1 , Figure 1 This is a diagram of an application scenario of the energy storage device 1000 provided in an embodiment of the present application.

[0041] The energy storage device 1000 provided in the embodiment of the present application is applied to an energy storage system 5000, which includes an electric energy conversion device 4500 (photovoltaic panel), a wind energy conversion device 4000 (windmill), a first electric device (grid), a second electric device 3000 (base station) and an energy storage device 1000. The energy storage system also includes an energy storage cabinet, and the energy storage device 1000 is installed in the energy storage cabinet, which can be installed outdoors. Specifically, the first electric energy conversion device can convert solar energy into electric energy during periods of low electricity prices, and the energy storage device 1000 is used to store the electric energy and supply it to the first electric device or the second electric device during peak electricity consumption, or to supply power when the first electric device or the second electric device is powered off / out of power. The second electric energy conversion device can convert wind energy into electric energy, and the energy storage device 1000 is used to store the electric energy and supply it to the first electric device or the second electric device during peak electricity consumption, or to supply power when the first electric device or the second electric device is powered off / out of power. Among them, the transmission of electric energy can be carried out using high-voltage cables.

[0042] It should be noted that the first electric device, the second electric device and other devices including the energy storage device 1000 can be understood as electric devices.

[0043] See also Figure 2 、 Figure 3 and Figure 4 , Figure 2 This is a side view of the energy storage device 1000 provided in the first embodiment of the present application. Figure 3 for Figure 2 The cross-sectional structural diagram of the energy storage device 1000 is shown in FIG. Figure 4 for Figure 3 The schematic diagram of the exploded structure of the energy storage device 1000 before assembly is shown.

[0044] For the convenience of description, we define Figure 2 The energy storage device 1000 shown has a length direction of the X-axis, a width direction of the Y-axis, and a thickness direction of the Z-axis. The X-axis, Y-axis, and Z-axis directions are perpendicular to each other.

[0045] The energy storage device 1000 includes a housing 100, a top cover 200, a battery cell 300 and an electrolyte ( Figure 2 and Figure 3 (not shown), the top cover 200 is mounted on the housing 100, the battery cell 300 is mounted on the inner side of the housing 100, and the electrolyte is filled in the inner side of the housing 100 and soaks the battery cell 300. Exemplarily, the energy storage device 1000 includes a battery cell, a battery module, or a battery pack.

[0046] Specifically, the housing 100 may be an aluminum housing. The housing 100 includes a bottom housing 110 and side housings 130. The side housings 130 surround the bottom housing 110 and, together with the bottom housing 110, form a housing cavity. The top cover 200 is mounted on the side housings 130 and positioned opposite the bottom housing 110 to facilitate mounting of the top cover 200 on the housing 100. The top cover 200 faces the positive X-axis direction, while the bottom housing 110 faces the negative X-axis direction.

[0047] The battery cell 300 is installed in the accommodating cavity of the housing 100 so that the battery cell 300 is installed on the inner side of the housing 100. The top of the battery cell 300 is the end facing the top cover 200, and the bottom of the battery cell 300 is the end facing away from the top cover 200. In this embodiment, the length direction of the battery cell 300 is the X-axis direction, the width direction is the Y-axis direction, and the thickness direction is the Z-axis direction. The top of the battery cell 300 faces the positive direction of the X-axis, and the bottom faces the negative direction of the X-axis. There can be one or more battery cells 300. When there are multiple battery cells 300, the assembled energy storage device 1000 forms a multi-JR (jelly roll) structure. At this time, the multiple battery cells 300 can be electrically connected in parallel. In this embodiment, there are two battery cells 300, and the two battery cells 300 are installed on the inner side of the housing 100 along the thickness direction of the battery cells 300. The assembled energy storage device 1000 has a 2JR structure.

[0048] The energy storage device 1000 has a width skirt margin and a thickness skirt margin. The width skirt margin = W2 / W1, where W1 represents the inner diameter of the outer shell 100 along the width direction, and W2 represents the length of each battery cell 300 along the width direction. The thickness skirt margin = D2 / D1, where D1 represents the inner diameter of the outer shell 100 along the thickness direction, and D2 represents the total length of the battery cell 300 along the thickness direction. The width direction of the battery cell 300 is the Y-axis direction, and the thickness direction is the Z-axis direction. In this embodiment, the length of a single battery cell 300 along the thickness direction is D3, that is, the thickness of the battery cell 300 is D3. When there are N battery cells 300 in the energy storage device 1000, N≥2, and N is an integer, D2=N*D3. For example, the thickness D3 of the battery cell 300 is 30mm~38mm, and the width W2 is 166mm~171mm.

[0049] It should be understood that "width skirt margin > 100%" indicates an interference fit between the housing 100 and the battery cell 300 in the width direction, and "thickness skirt margin > 100%" indicates an interference fit between the housing 100 and the battery cell 300 in the thickness direction. For example, in the embodiment of the present application, the thickness skirt margin of the energy storage device 1000 is 85% to 105%, that is, the energy storage device 1000 satisfies the following conditions: 85% ≤ D2 / D1 ≤ 105%.

[0050] See Figure 5 , Figure 5 for Figure 2 The cross-sectional structure diagram of the battery cell 300 in the energy storage device 1000 is shown. Figure 5 The dotted line in represents the diaphragm 350 .

[0051] The length direction of the battery cell 300 is the X-axis direction, the width direction is the Y-axis direction, and the thickness direction is the Z-axis direction. The battery cell 300 is formed by winding a material including a first pole piece 310, a second pole piece 330, and a diaphragm 350. The diaphragm 350 is arranged between the first pole piece 310 and the second pole piece 330. Exemplarily, in this embodiment, the winding direction of the battery cell 300 is clockwise, and the winding directions of the first pole piece 310 and the second pole piece 330 are both clockwise. In this embodiment, the material including the first pole piece 310, the second pole piece 330, and the diaphragm 350 is wound in a clockwise direction and then hot-pressed or cold-pressed to form the battery cell 300. In this embodiment, the first pole piece 310 is the anode piece, and the second pole piece 330 is the cathode piece. Among them, in the wound battery cell 300, the second pole piece 330 is coated on the outside of the first pole piece 310, forming a negative-enclosing-positive structure. It is understandable that, in other embodiments, the first electrode piece 310 may also be a cathode piece, and the second electrode piece 330 may be an anode piece.

[0052] Specifically, the first electrode 310 includes a first current collector 301 and a first active layer 303 covering the surface of the first current collector 301. In this embodiment, the first active layer 303 covers both sides of the first current collector 301 along the thickness direction. Exemplarily, the thickness of the first electrode 310 is 100μm to 140μm. Along the winding direction of the first electrode 310, the first electrode 310 includes a hollow foil segment 40, a first starting segment 10, a first middle segment 20 and a first ending segment 30. The first starting segment 10 is connected to the hollow foil segment 40 and is arranged opposite to the first ending segment 30 along the winding direction of the first electrode 310. The first middle segment 20 is connected between the first starting segment 10 and the first ending segment 30. In this embodiment, the hollow foil segment 40 is the first current collector and is not coated with the material of the first active layer 303. The first starting section 10 , the first middle section 20 and the first ending section 30 all include a first current collector 301 and a first active layer 303 covering the surface of the first current collector 301 .

[0053] In particular, along the winding direction of the first pole piece 310, the first starting section 10 is provided with a first starting end face 15, and the first starting end face 15 is arranged along the extension direction of the first starting section 10. In this embodiment, the first starting section 10 includes a straight portion 11 and a bent portion 13. The straight portion 11 extends along the Y-axis direction, and the bent portion 13 is connected to the straight portion 11 and bent relative to the straight portion 11. The bent portion 13 includes a first starting end face 15, and the first starting end face 15 is arranged along the extension direction of the bent portion 13 and away from the straight portion 11.

[0054] The hollow foil segment 40 is connected to the first starting end face 15 of the bent portion 13 of the first starting segment 10, facing away from the straight portion 11. In this embodiment, the hollow foil segment 40 is integrally connected to the first current collector 301 of the bent portion 13 of the first starting segment 10, thereby achieving an integral connection between the hollow foil segment 40 and the first current collector 301 of the first starting segment 10. The hollow foil segment 40 includes a straight portion 42. The straight portion 42 of the hollow foil segment 40 is integrally connected to the first current collector 301 of the bent portion 13 of the first starting segment 10, thereby achieving connection between the straight portion 42 of the hollow foil segment 40 and the end of the bent portion 13 of the first starting segment 10, facing away from the straight portion 11 of the first starting segment 10. Furthermore, the straight portion 42 of the hollow foil segment 40 and the straight portion 11 of the first starting segment 10 are spaced apart along the thickness direction of the battery cell 300, thereby achieving a spaced apart arrangement between the hollow foil segment 40 and the first starting segment 10 along the thickness direction of the battery cell 300.

[0055] Specifically, the empty foil segment 40 includes a main body 41 and a stamping portion 43. The main body 41 is connected to the first current collector 301 in the bent portion 13 to achieve a connection between the empty foil segment 40 and the bent portion 13, thereby achieving a connection between the empty foil segment 40 and the first starting segment 10. The main body 41 includes a first surface 411 and a second surface 413 that are arranged opposite to each other in the thickness direction. The first surface 411 faces the straight portion 11, and the second surface 413 faces away from the straight portion 11. The stamping portion 43 is connected to the main body 41 and protrudes relative to the main body 41 in the thickness direction of the main body 41. The stamping portion 43 includes a raised surface 45 that protrudes relative to the main body 41 in the thickness direction of the main body 41, and the stamping portion 43 is provided with a groove 46, the opening of which is provided on the surface of the stamping portion 43 facing away from the raised surface 45. Among them, the groove 46 can be used to retain the electrolyte after the battery cell 300 is injected with the electrolyte, so as to facilitate the subsequent replenishment of the electrolyte inside the battery cell 300. In this embodiment, an embossing process can be used to stamp a stamped portion 43 on the flat body 41. Exemplarily, the height of the raised surface 45 of the stamped portion 43 relative to the body 41 is H, 5μm≤H≤50μm. Exemplarily, the groove 46 of the stamped portion 43 is a square groove. It can be understood that in other embodiments, the shape of the groove 46 of the stamped portion 43 can also be a rectangular groove, a circular groove, etc., and this application does not limit the shape of the groove 46.

[0056] like Figure 5As shown, in this embodiment, there are multiple stamped portions 43 along the width of the battery cell 300. The multiple stamped portions 43 include a first stamped portion 431 and a second stamped portion 433. The raised surface 45 of the first stamped portion 431 protrudes in a first direction relative to the first surface 411 of the body 41, and the raised surface 45 of the second stamped portion 433 protrudes in a second direction relative to the second surface 413 of the body 41. The second direction is opposite to the first direction. In this embodiment, the first direction is the positive direction of the Z axis, and the second direction is the negative direction of the Z axis. It will be understood that the height of the raised surface 45 of the first stamped portion 431 relative to the first surface 411 is the height of the first stamped portion 431 relative to the body 41, and the height of the raised surface 45 of the second stamped portion 433 relative to the second surface 413 is the height of the second stamped portion 433 relative to the body 41. In this embodiment, the multiple first stamped portions 431 and the multiple second stamped portions 433 are arranged alternately along the width of the battery cell 300.

[0057] See also Figure 6 and Figure 7 , Figure 6 for Figure 4 The schematic diagram of the top view of the hollow foil segment 40 of the battery cell 300 is shown. Figure 7 for Figure 6 The cross-sectional structure diagram of the hollow foil segment 40 at CC is shown. In this embodiment, along the length direction of the battery cell 300 and from the bottom to the top of the battery cell 300, that is, along the positive direction of the X-axis, there are multiple stamped portions 43, and the openings of the grooves 46 of the multiple stamped portions 43 gradually increase. In this embodiment, along the length direction of the battery cell 300, the multiple stamped portions 43 include a first stamped portion 431 and a second stamped portion 433, and the multiple first stamped portions 431 and the multiple second stamped portions 433 are arranged alternately along the length direction of the battery cell 300. It is understood that in other embodiments, along the length direction of the battery cell 300, the multiple stamped portions 43 can all be first stamped portions 431; or, the multiple stamped portions 43 can all be second stamped portions 433; or, some of the multiple stamped portions 43 can be first stamped portions 431 and some can be second stamped portions 433. This is not limited in this application.

[0058] It is understood that in other embodiments, the hollow foil segments 40 may be wound into multiple layers, with the multiple layers of hollow foil segments 40 being sequentially connected. The multiple layers of hollow foil segments 40 are spaced apart along the thickness direction of the battery cell 300. For example, the hollow foil segments 40 may be bent multiple times to form multiple layers of hollow foil segments 40 that are bent in a serpentine shape.

[0059] Continue reading Figure 5The first intermediate section 20 is connected to the end of the straight portion 11 in the first starting section 10 away from the bent portion 13, so as to realize the connection between the first intermediate section 20 and the first starting section 10. In this embodiment, the first intermediate section 20 is wound in multiple layers along the winding direction of the first pole piece 310. The first tail section 30 is connected to the end of the first intermediate section 20 away from the first starting section 10, so as to realize the connection between the first intermediate section 20 and the first starting section 10 and the first tail section 30. At this time, the first tail section 30 and the first starting section 10 are arranged opposite to each other along the winding direction of the first pole piece 310. The first tail section 30 includes a first tail end face 31, which is arranged along the winding direction of the first tail section 30 and away from the first intermediate section 20, so as to realize the first tail end face 31 away from the first starting section 10.

[0060] The second pole piece 330 includes a second current collector 305 and a second active layer 307 covering the surface of the second current collector 305. In this embodiment, the second active layer 307 covers both sides of the second current collector 305 along the thickness direction. Exemplarily, the thickness of the second pole piece 330 is 150μm to 200μm. Exemplarily, in this embodiment, the second pole piece 330 is made by mixing materials including cathode active material, conductive agent, adhesive and dispersant in a certain proportion, coating them on the second current collector 305 and then cold pressing them. Exemplarily, the compaction density of the second pole piece 330 is 2.30g / cm 3 ~2.60g / cm 3 The cathode active material may be lithium iron phosphate, the conductive agent may be carbon nanotubes (CNTs), the adhesive may be polyvinylidene difluoride (PVDF), and the dispersant may be polyvinylpyrrolidone (PVP). For example, in some embodiments, the PVDF content in the second active layer 307 is 1.0% to 4.0%.

[0061] Along the winding direction of the second electrode sheet 330, the second electrode sheet 330 includes a second starting section 50, a second middle section 60, and a second ending section 70. The second starting section 50 and the second ending section 70 are arranged opposite each other along the winding direction of the second electrode sheet 330, and the second middle section 60 is connected between the second starting section 50 and the second ending section 70. In this embodiment, the second starting section 50, the second middle section 60, and the second ending section 70 all include a second current collector 305 and a second active layer 307 covering the surface of the second current collector 305.

[0062] The second starting section 50 is located on the side of the first starting section 10 that is away from the empty foil section 40, wherein the first surface 411 of the main body 41 in the empty foil section 40 faces the second starting section 50, and the second surface 413 faces away from the second starting section 50. In this embodiment, the second starting section 50 extends along the Y-axis direction. Along the winding direction of the second pole piece 330, the second starting section 50 includes a second starting end face 51, and the second starting end face 51 is arranged along the extension direction of the second starting section 50. In this embodiment, the second starting end face 51 faces the negative direction of the Y-axis, and the second starting end face 51 is the starting winding end face of the second pole piece 330, that is, the feeding position of the second pole piece 330. The first starting end face 15 protrudes relative to the second starting end face 51 in the opposite direction of the winding direction of the first electrode piece 310, so that the first starting section 10 exceeds the second starting section 50 in the opposite direction of the winding direction of the first electrode piece 310, thereby achieving that the feeding position of the second electrode piece 330 is shorter than the feeding position of the first starting section 10 in the first electrode piece 310. In this embodiment, along the width direction of the battery cell 300, the maximum distance between the second starting end face 51 of the second starting section 50 and the bent portion 13 in the first starting section 10 is h. Exemplarily, 3mm≤h≤20mm. Along the width direction of the battery cell 300, the position at which the bent portion 13 in the first starting section 10 is at the maximum distance from the second starting end face 51 is the corner position A of the first starting section 10, and the maximum distance between the corner position A and the second starting end face 51 along the width direction of the battery cell 300 is the maximum distance h.

[0063] The second intermediate section 60 is connected to the end of the second starting section 50 that is away from the second starting end face 51 to achieve a connection between the second intermediate section 60 and the second starting section 50. In this embodiment, the second intermediate section 60 is wound into multiple layers along the winding direction of the battery cell 300. The second tail section 70 is connected to the end of the second intermediate section 60 that is away from the second starting section 50 to achieve a connection between the second intermediate section 60 and the second tail section 70. At this time, the second tail section 70 and the second starting section 50 are arranged opposite to each other along the winding direction of the second pole piece 330. The second tail section 70 includes a second tail end face 71, which is arranged along the extension direction of the second tail section 70 and away from the second intermediate section 60 to achieve the second tail end face 71 away from the second starting section 50.

[0064] Exemplarily, the thickness of the diaphragm 350 is 7 μm to 18 μm. Along its extension, the diaphragm 350 includes a starting film segment 80, an intermediate film segment 91, and a finishing film segment 92. The intermediate film segment 91 is connected between the starting film segment 80 and the finishing film segment 92. The starting film segment 80 is positioned between the first starting segment 10 and the second starting segment 50 to separate them. Furthermore, the starting film segment 80 is positioned between the hollow foil segment 40 and the first starting segment 10 to separate them. In this embodiment, the starting film segment 80 also covers the portion of the first starting segment 10 that extends beyond the second starting segment 50. The intermediate film segment 91 is positioned between the first intermediate segment 20 and the second intermediate segment 60 to separate them. The first intermediate segment 20 and the second intermediate segment 60 are located on either side of the intermediate film segment 91 along its thickness. The tail film segment 92 is isolated between the first tail segment 30 and the second tail segment 70 to isolate the first tail segment 30 and the second tail segment 70. The first tail segment 30 and the second tail segment 70 are located on both sides of the tail film segment 92 along the thickness direction of the tail film segment 92.

[0065] The battery cell 300 further includes a first electrode tab 360 and a second electrode tab 370 . There can be multiple first electrode tabs 360 , each of which is electrically connected to the first electrode sheet 310 . There can also be multiple second electrode tabs 370 , each of which is electrically connected to the second electrode sheet 330 .

[0066] In the battery cell 300 provided in the embodiment of the present application, by providing a hollow foil segment 40 in the first electrode 310 and providing a stamping portion 43 in the hollow foil segment 40, on the one hand, the groove 46 provided in the stamping portion 43 in the hollow foil segment 40 can store electrolyte when the battery cell 300 is filled with liquid. When the shell 100 is pressed against the battery cell 300, the electrolyte in the groove 46 is not easily squeezed out. As a result, in the middle and late stages of the cycle of the battery cell 300, when the electrolyte inside the winding of the first electrode 310 is exhausted, the electrolyte stored in the groove 46 can be replenished to the first electrode 310 in time to ensure that the transmission path of lithium ions is unobstructed, thereby improving the cycle performance of the battery cell 300. On the other hand, compared with other methods of improving the cycle performance of the battery cell 300, the embodiment of the present application can improve the cycle performance of the battery cell 300 by adding the process step of providing the stamping portion 43, without the need for additional material costs, which is conducive to reducing the production cost of the battery cell 300. In addition, the empty foil segment 40 does not contain active materials, which is equivalent to saving the cost of active materials, thereby further reducing the production cost of the battery cell 300.

[0067] In addition, the applicant's research found that compared with the first pole piece 310, the active layer material in the second pole piece 330 is generally coated with a higher density and compacted with a higher density. Therefore, when the second pole piece 330 is wound, it is more likely to cause the active layer material to fall off or even break. In the battery cell 300 provided in the embodiment of the present application, by adding a hollow foil segment 40 to the first pole piece 310, on the one hand, the straight portion 42 of the hollow foil segment 40 and the straight portion 11 of the first starting segment 10 are spaced apart in the thickness direction of the battery cell 300, which is equivalent to increasing the thickness of the first pole piece 310 in the inner space of the battery cell 300, thereby reducing the curvature of the second pole piece 330 at the winding corner when the second pole piece 330 is wound around the first pole piece 310, thereby reducing the problem of the active layer material falling off or even the risk of breaking of the second pole piece 330. In addition, since the empty foil segment 40 has a large area and a thin thickness, the surface stress of the empty foil segment 40 can easily cause the empty foil segment 40 to curl, thereby affecting the winding efficiency of the empty foil segment 40, and even causing the empty foil segment 40 to be directly folded inwardly, resulting in uneven thickness of the empty foil segment 40. By providing the stamping portion 43 on the empty foil segment 40, the surface stress distribution of the empty foil segment 40 can be greatly improved, thereby reducing the risk of curling of the empty foil segment 40.

[0068] In addition, by setting the first starting section 10 of the first pole piece 310 to extend beyond the second starting section 50 of the second pole piece 330 in the opposite direction of the winding direction of the first pole piece 310, an excess coefficient of the first pole piece 310 to the second pole piece 330 is created, so that the first pole piece 310 has sufficient lithium insertion positions to ensure that lithium is not deposited.

[0069] In addition, during use of the energy storage device 1000, the electrolyte is gradually consumed, wherein the electrolyte near the top cover 200 of the energy storage device 1000 dries up first. In the embodiment of the present application, the openings of the grooves 46 of the multiple stamped portions 43 in the empty foil segment 40 are gradually enlarged along the length direction of the battery cell 300 and toward the top cover 200, so that the grooves 46 of the stamped portion 43 near the top cover 200 can store more electrolyte for replenishing the electrolyte, maintaining the transmission path of lithium ions unobstructed, and thus improving the cycle performance of the battery cell 300.

[0070] In addition, by setting the starting membrane segment 80 of the diaphragm 350 between the first starting segment 10 of the first electrode piece 310 and the second starting segment 50 of the second electrode piece 330, and covering the portion of the first starting segment 10 that exceeds the second starting segment 50, on the one hand, the starting membrane segment 80 is used to isolate the first electrode piece 310 and the second electrode piece 330, and on the other hand, after the first electrode piece 310 is wound, the portion of the first starting segment 10 that exceeds the second starting segment 50 can be isolated from the first middle segment 20 of the first electrode piece 310 by the starting membrane segment 80, thereby avoiding the problem of short circuit in the battery cell 300.

[0071] Continue reading Figure 5 In the assembled battery cell 300, the battery cell 300 includes two first surfaces 380 and two second surfaces 390. The two first surfaces 380 are arranged opposite to each other along the thickness direction of the battery cell 300, and the two second surfaces 390 are arranged opposite to each other along the width direction of the battery cell 300, and each second surface 390 is connected between the two first surfaces 380. In this embodiment, the first electrode 310, the second electrode 330 and the diaphragm 350 are wound to form a runway-shaped battery cell 300. In this embodiment, the first surface 380 is roughly planar, and the second surface 390 is curved. Among them, the second surface 390 is provided with a widest position B. Both second surfaces 390 have a widest position B. The widest position B of a second surface 390 refers to the position of one second surface 390 farthest from the other second surface 390 along the width direction of the battery cell 300.

[0072] In this embodiment, the first terminal segment 30 of the first pole piece 310 terminates at the second surface 390, and the first terminal end surface 31 of the first terminal segment 30 is located between the two first surfaces 380. "The first terminal segment 30 terminates at the second surface 390" means that the first terminal end surface 31 of the first terminal segment 30 does not extend to the first surface 380. In this embodiment, the first terminal segment 30 extends in a direction parallel to the second surface 390.

[0073] The embodiment of the present application also optimizes the design of the tail position of the first electrode piece 310. By arranging the first tail end surface 31 between the two first surfaces 380, the first tail section 30 of the first electrode piece 310 does not contact the first surface 380 of the battery cell 300. This avoids the first tail end surface 31 of the first tail section 30 of the first electrode piece 310 becoming the highest point of the entire first surface 380 due to contact with the first surface 380. On the one hand, while ensuring that the capacity of the battery cell 300 can be normally utilized, the thickness of the battery cell 300 is avoided from being increased. This helps reduce the thickness margin of the energy storage device 1000 formed by assembling the battery cells 300. On the other hand, it can prevent the battery cells 300 from being subjected to external forces and causing stress points to be generated at the position of the first tail section 30 during the process of hot pressing or cold pressing to form the battery cells 300, as well as when the cycled battery cells 300 touch the shell. This can then be transmitted to the inner layers of the battery cells 300, causing the electrolyte at the stress points to be squeezed out of the pole pieces, resulting in poor electrolyte infiltration, thereby causing excessive current density around the stress points, and causing purple spots or lithium deposition in the battery cells 300.

[0074] The second tail section 70 of the second pole piece 330 terminates at the second surface 390. Herein, "the second tail section 70 terminates at the second surface 390" means that the second tail end surface 71 of the second tail section 70 does not extend to the first surface 380. In this embodiment, the second tail section 70 extends in a direction parallel to the second surface 390. Herein, the second tail section 70 and the first tail section 30 terminate at the same second surface 390 in the same direction, and along the winding direction of the battery cell 300, the first tail end surface 31 of the first tail section 30 exceeds the second tail end surface 71 of the second tail section 70. Exemplarily, the length by which the first tail end surface 31 of the first tail section 30 exceeds the second tail end surface 71 of the second tail section 70 is L, and L ≥ 3.5 mm.

[0075] Furthermore, the second end face 71 of the second end section 70 in the second pole piece 330 does not exceed the widest portion B of the second surface 390. The phrase "the second end face 71 does not exceed the widest portion B" means that when the second pole piece 330 is wound along the winding direction of the battery cell 300, the second end section 70 is wound from one first surface 380 to the second surface 390, and the second end section 70 is located between the widest portions B of the first surface 380 and the second surface 390, so that the second end face 71 is located between the widest portions B of the first surface 380 and the second surface 390. In this embodiment, the widest portion B of the second surface 390 is located at 1 / 2 of the thickness of the battery cell 300. The second surface 390 is generally semi-arc-shaped, and the widest portion B is approximately located at 1 / 2 of the arc segment of the semi-arc-shaped second surface 390.

[0076] The embodiment of the present application also optimizes the design of the tail position of the second electrode piece 330. By setting the second tail end face 71 not to exceed the widest position B of the second surface 390, the tail of the second electrode piece 330 does not exceed the widest part of the battery cell 300. This avoids the second tail section 70 of the second electrode piece 330 exceeding the widest position B of the second surface 390, which causes the battery cell 300 to increase by one layer of winding thickness in the width direction. On the one hand, while ensuring that the capacity of the battery cell 300 can be normally exerted, the width of the battery cell 300 is avoided from being increased, thereby facilitating the reduction of the width skirt margin of the energy storage device 1000 formed by assembling the battery cell 300. This avoids the problem that high-energy-density lithium-ion energy storage devices with a relatively extreme width skirt margin design make it difficult for the battery cell 300 to be inserted into the housing 100. After the battery cell 300 is installed in the housing 100, the housing 100 is more easily squeezed on both sides in the width direction, thereby increasing the risk of "S"-shaped deformation of the battery cell 300.

[0077] See Figure 8 , Figure 8 This is a schematic cross-sectional structural diagram of the energy storage device 1000 provided in the second embodiment of the present application.

[0078] The energy storage device 1000 of the second embodiment differs from the energy storage device 1000 of the first embodiment in that the first starting section 10 of the first pole piece 310 of the energy storage device 1000 of the second embodiment includes only a straight portion 11 , and the hollow foil segment 40 also includes a bent portion 44 .

[0079] Specifically, along the extension direction of the hollow foil segment 40, the hollow foil segment 40 includes a straight portion 42 and a bent portion 44. The straight portion 42 of the hollow foil segment 40 and the straight portion 11 of the first starting segment 10 are spaced apart along the thickness direction of the battery cell 300. The bent portion 44 of the hollow foil segment 40 connects between the straight portion 42 of the hollow foil segment 40 and the first current collector 301 of the straight portion 11 of the first starting segment 10, thereby establishing a connection between the hollow foil segment 40 and the first starting segment 10. At this time, the end surface of the straight portion 11 of the first starting segment 10 facing the bent portion 44 of the hollow foil segment 40 is the first starting end surface 15.

[0080] In the second embodiment, the stamping portion 43 is located on the straight portion 42 of the empty foil segment 40 . It is understood that in other embodiments, the stamping portion 43 may also be located on both the bent portion 44 and the straight portion 42 of the empty foil segment 40 .

[0081] See Figure 9 , Figure 9 This is a schematic cross-sectional structural diagram of an energy storage device 1000 provided in the third embodiment of the present application.

[0082] The energy storage device 1000 of the third embodiment differs from the energy storage device 1000 of the first embodiment in that the first starting section 10 in the first pole piece 310 of the energy storage device 1000 of the third embodiment includes a straight portion 11 and a bent portion 13 , and along the extension direction of the empty foil segment 40 , the empty foil segment 40 includes a straight portion 42 and a bent portion 44 .

[0083] Specifically, the bent portion 44 of the hollow foil segment 40 is connected to the straight portion 42 of the hollow foil segment 40 and is also connected to the end of the bent portion 13 of the first starting segment 10 that faces away from the straight portion 11 of the first starting segment 10. At this point, the bent portion 44 of the hollow foil segment 40 and the bent portion 13 of the first starting segment 10 together constitute the winding corner portion of the first electrode 310. In the third embodiment, the stamped portion 43 is located on the straight portion 42 of the hollow foil segment 40. It is understood that in other embodiments, the stamped portion 43 may also be located on both the bent portion 44 and the straight portion 42 of the hollow foil segment 40.

[0084] The above disclosure is only a preferred embodiment of the present application, and it is certainly not intended to limit the scope of the rights of the present application. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made in accordance with the claims of the present application are still within the scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell is formed by winding a first electrode piece, a diaphragm, and a second electrode piece. The diaphragm is provided between the first electrode piece and the second electrode piece. Along the winding direction of the first electrode piece, the first electrode piece includes a hollow foil segment and a first starting segment connected to the hollow foil segment. The hollow foil segment and the first starting segment both include a straight portion. The straight portion of the hollow foil segment and the straight portion of the first starting segment are spaced apart along the thickness direction of the battery cell. Along the winding direction of the second electrode piece, the second electrode piece includes a second starting segment. The second starting segment is located on a side of the first starting segment facing away from the hollow foil segment. The first starting section extends beyond the second starting section in a direction opposite to the winding direction of the first electrode sheet. The hollow foil section includes a body and a stamped portion. The stamped portion is connected to the body and includes a raised surface. Along the thickness direction of the body, the raised surface protrudes relative to the body. The stamped portion is provided with a groove. The opening of the groove is provided on the surface of the stamped portion facing away from the raised surface. There are multiple stamped portions along the direction from the bottom to the top of the battery cell, and the openings of the grooves of the multiple stamped portions gradually increase. The battery cell comprises two first surfaces and two second surfaces, the two first surfaces are arranged opposite to each other along the thickness direction of the battery cell, and the two second surfaces are arranged opposite to each other along the width direction of the battery cell; The first pole piece further includes a first ending section, the first ending section and the first starting section are arranged opposite to each other along the winding direction of the first pole piece, the first ending section includes a first ending end surface, the first ending end surface is arranged along the winding direction of the first ending section and away from the first starting section, the first ending section ends at one of the second surfaces, and the first ending end surface is located between the two first surfaces; The second surface is a curved surface, and the second surface is provided with a widest position. The second pole piece further includes a second tail section, and the second tail section and the second starting section are arranged opposite to each other along the extension direction of the second pole piece. The second tail section includes a second tail end face, and the second tail end face is arranged along the extension direction of the second tail section and away from the second starting section. The second tail section ends at one of the second surfaces, and the second tail end face does not exceed the widest position.

2. The battery cell according to claim 1, characterized in that The main body includes a first surface and a second surface arranged opposite to each other in the thickness direction, the first surface faces the second starting section, and the second surface faces away from the second starting section. There are multiple stamping parts, and the multiple stamping parts include a first stamping part and a second stamping part. The convex surface of the first stamping part protrudes relative to the first surface of the main body, and the convex surface of the second stamping part protrudes relative to the second surface of the main body.

3. The battery cell according to claim 2, characterized in that The plurality of first stamping portions and the plurality of second stamping portions are arranged alternately.

4. The battery cell according to claim 1, characterized in that The height of the raised surface relative to the main body is H, 5 μm≤H≤50 μm.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The first starting section further includes a bent portion, wherein the bent portion of the first starting section is connected between the straight portion of the empty foil section and the straight portion of the first starting section; Alternatively, the empty foil segment further includes a bent portion, and the bent portion of the empty foil segment is connected between the straight portion of the empty foil segment and the straight portion of the first starting segment; Alternatively, the first starting segment and the empty foil segment both include a bent portion, the bent portion of the first starting segment is connected to the straight portion of the first starting segment, and the bent portion of the empty foil segment is connected to the straight portion of the empty foil segment, and is connected to the end of the bent portion of the first starting segment facing away from the straight portion of the first starting segment.

6. The battery cell according to claim 1, characterized in that The second ending section and the first ending section end at the same second surface, and along the winding direction of the battery cell, the first ending end surface exceeds the second ending end surface.

7. The battery cell according to claim 6, characterized in that Along the winding direction of the battery core, the length of the first tail end face exceeding the second tail end face is L, and L is ≥ 3.5 mm.

8. An energy storage device, characterized in that: The battery comprises a housing and at least one battery core according to any one of claims 1 to 7, wherein the battery core is installed on the inner side of the housing.

9. The energy storage device according to claim 8, characterized in that The energy storage device satisfies the following conditions: 85%≤D2 / D1≤105%, wherein D1 represents the inner diameter of the shell along the thickness direction, and D2 represents the total length of the battery cell along the thickness direction.

10. The energy storage device according to claim 8, characterized in that: There are two battery cells, and the two battery cells are installed on the inner side of the shell along the thickness direction of the battery cells.

11. An electrical device, characterized in that: It comprises the energy storage device according to any one of claims 8 to 10, wherein the energy storage device is used to supply power to the electrical equipment.

Images