Battery cells, energy storage devices and electrical equipment

Abstract

The present application provides a battery cell, an energy storage device and an electrical equipment, wherein the battery cell is wound by a material including a first electrode sheet, a diaphragm and a second electrode sheet, the diaphragm is arranged between the first electrode sheet and the second electrode sheet, the first electrode sheet includes a first starting section, the first starting section includes an extension portion and a folded portion, the folded portion is connected to the extension portion and folded toward one side of the extension portion along the thickness direction, the second electrode sheet includes a second starting section, the second starting section and the folded portion are located on the same side of the extension portion along the thickness direction of the extension portion, and are spaced apart from the folded portion along the width direction of the battery cell, the diaphragm includes a starting film section, the starting film section is arranged between the first starting section and the second starting section, and at least partially covers the folded portion. The present application can solve the problem of stress concentration occurring at the feeding position of the cathode sheet and the feeding position of the anode sheet of the battery cell.

Description

Technical Field

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

[0002] Existing battery cells are usually formed by winding cathode sheets, anode sheets and separators. Among them, in the wound battery cells, the feeding position of the cathode sheet and the feeding position of the anode sheet may be inconsistent, resulting in inconsistent thickness of the battery cell at the feeding position of the cathode sheet and the feeding position of the anode sheet, which easily leads to stress concentration problems at the feeding position of the cathode sheet and the feeding position of the anode sheet. 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 equipment, which can solve the problem of stress concentration at the feeding position of the cathode sheet and the feeding position of the anode sheet of the battery cell.

[0004] An embodiment of the present application provides a battery cell, which is formed by winding a material including a first electrode piece, a diaphragm and a second electrode piece, the diaphragm is arranged between the first electrode piece and the second electrode piece, the first electrode piece includes a first starting section, the first starting section includes an extension portion and a folded portion, the folded portion is connected to the extension portion and is folded toward one side of the extension portion along the thickness direction, the second electrode piece includes a second starting section, the second starting section and the folded portion are located on the same side of the extension portion along the thickness direction of the extension portion, and are spaced apart from the folded portion along the width direction of the battery cell, the diaphragm includes a starting film section, the starting film section is arranged between the first starting section and the second starting section, and at least partially covers the folded portion.

[0005] In the battery cell provided in the embodiment of the present application, the second starting section of the second pole piece is spaced apart from the folded portion of the first starting section of the first pole piece, so that the feeding position of the second pole piece is shorter than that of the first pole piece, thereby allowing the first pole piece to have sufficient lithium insertion position to ensure that lithium is not deposited.

[0006] In order to solve the problem of inconsistent thickness of the battery cell at the feeding position of the first and second pole pieces introduced when the feeding position of the second pole piece is shorter than that of the first pole piece. In the embodiment of the present application, on the one hand, by folding the folded part in the first starting section of the first pole piece relative to the extended part, it is equivalent to increasing the thickness of the first pole piece at the folded part, making up for the missing thickness at the feeding position of the second pole piece, which is conducive to improving the thickness consistency of the battery cell, thereby solving the problem of stress concentration of the battery cell at the feeding position of the first pole piece and the feeding position of the second pole piece, thereby reducing the risk of uneven current density distribution of the battery cell at the stress concentration point. In addition, by arranging the folded part of the first pole piece and the second starting section of the second pole piece on the same side of the extended part, so that the folded part in the first starting section of the first pole piece is folded in the opposite direction relative to the extended part, and there is no extra layer of extended part between the folded part and the second starting section, while compensating for the missing thickness at the feeding position of the second pole piece, it is more conducive to improving the uneven thickness distribution of the battery cell caused by the feeding position of the second pole piece, thereby solving the problem of stress concentration in the battery cell at the feeding position of the first pole piece and the feeding position of the second pole piece.

[0007] On the other hand, by setting the starting film segment in the diaphragm between the first starting segment and the second starting segment, and at least partially covering the folded portion, the starting film segment covering the folded portion can further increase the thickness of the battery cell at the folded portion of the first pole piece, thereby further compensating for the missing thickness at the feeding position of the second pole piece, which is more conducive to improving the thickness consistency of the battery cell and reducing the risk of uneven current density distribution at the stress concentration point of the battery cell. In addition, the folded portion and the second starting segment are separated only by the starting film segment, which is ductile and will not produce creases under the action of external force. In the process of hot pressing or cold pressing to form the battery cell, the starting film segment can be deformed under external force to adjust the thickness at the folded portion and the thickness at the second starting segment, thereby further compensating for the difference between the thickness of the battery cell at the folded portion and the thickness of the battery cell at the second starting segment, thereby further improving the thickness consistency of the battery cell, so that the battery cell will not produce pressure marks, and further reducing the risk of uneven current density distribution at the stress concentration point of the battery cell. In addition, the starting film segment is used to isolate the first pole piece and the second pole piece, and can also prevent the battery cell from short circuiting.

[0008] In addition, when the feeding position of the second pole piece is shorter than the feeding position of the first pole piece, the overall thickness of the battery cell on the side of the feeding position of the first pole piece is thin, which will cause the curvature of the innermost second pole piece to be too large during the process of hot pressing or cold pressing to form the battery cell, and thus easily lead to the risk of the innermost second pole piece breaking. The embodiment of the present application can also play a supporting role at the corner of the winding of the second pole piece by setting the folded part of the first pole piece to be folded relative to the extended part, which is conducive to reducing the curvature of the second pole piece at the corner, thereby helping to solve the problem of the active layer material falling off due to the excessive curvature of the second pole piece, and even the risk of breaking.

[0009] In a possible embodiment, the folded portion includes a first starting end face facing the second starting section, the second starting section includes a second starting end face facing the folded portion, and along the extension direction of the extension portion, the second starting end face and the first starting end face are spaced apart along the width direction of the battery cell, and the distance between the second starting end face and the first starting end face is H, 0<H≤40mm.

[0010] In a possible implementation, along the width direction of the battery core, the maximum distance between the second starting end surface and the folded portion is h, and 30 mm ≤ h ≤ 50 mm.

[0011] In a possible implementation manner, the extension length of the folded portion is 10 to 30 mm.

[0012] In a possible embodiment, along the winding direction of the starting film segment, the starting film segment includes a first part and a second part connected to the first part, the first part is located on the side of the extension portion away from the folded portion, and the first part is wound into multiple layers, and the second part covers the folded portion. By setting the first part to be wound into multiple layers, it is equivalent to further increasing the winding thickness of the first pole piece and the second pole piece on the inner side of the battery cell, thereby reducing the curvature of the first pole piece and the second pole piece on the inner side, which is conducive to improving the problem of the active layer material falling off due to excessive curvature of the first pole piece or the second pole piece, or even the risk of breaking.

[0013] In a possible implementation, the surface of the folded portion facing the extended portion is fitted with the surface of the extended portion facing the folded portion to avoid further increasing the thickness of the first starting section at the folded portion, thereby improving the uneven thickness distribution of the battery cell and avoiding increasing the thickness of the battery cell.

[0014] In a possible embodiment, the battery cell includes 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 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 surface, and the first tail end face is located between the two first surfaces, so that the first tail section of the first pole piece does not go up to the first surface of the battery cell, thereby avoiding the first tail section of the first pole piece from being on the first surface The first tail end face of the first tail section becomes the highest point of the entire first face. On the one hand, while ensuring that the capacity of the battery cell can be normally exerted, 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 assembling the battery cells. On the other hand, during the process of forming the battery cell by hot pressing or cold pressing, and when the circulating battery cell touches the shell, it can prevent the battery cell from being subjected to external force and causing stress points at the position of the first tail section, which are then transmitted to the inner layers of the battery cell, so that the electrolyte at the stress point is squeezed out of the pole piece, 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 in the battery cell.

[0015] In a possible embodiment, the second surface is a curved surface, and the second surface is provided with a widest position, the second pole piece also includes a second tail section, the second tail section and the second starting section are arranged opposite to each other along the winding direction of the second pole piece, the second tail section includes a second tail end face, the second tail end face is arranged along the winding 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 pole piece does not exceed the widest part of the battery cell, avoiding the second tail section of the second pole piece exceeding the widest position of the second surface, resulting in an increase in the thickness of the battery cell in the width direction. On the one hand, while ensuring that the capacity of the battery cell can be normally exerted, the width of the battery cell is avoided from being increased, thereby facilitating the reduction of the width skirt margin of the energy storage device formed by the assembly of the battery cells, and avoiding the high-energy-density lithium-ion energy storage device with a relatively extreme design of the width skirt margin, which makes it difficult for the battery cell to enter the shell, and 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.

[0016] In a possible implementation manner, 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.

[0017] In a possible implementation, along the winding direction of the battery cell, the length of the first tail end face exceeding the second tail end face is L, and L is ≥ 3.5 mm.

[0018] An embodiment of the present application also provides an energy storage device, including a housing and a battery cell as described above, wherein the battery cell is installed on the inner side of the housing.

[0019] In a possible implementation, the energy storage device satisfies: 85%≤D2 / D1≤105%, wherein 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.

[0020] 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.

[0021] 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

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative work.

[0023] Figure 1 An application scenario diagram of the energy storage device provided in the embodiment of the present application;

[0024] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of the energy storage device shown;

[0025] Figure 3 for Figure 2 A schematic diagram of the exploded structure of the energy storage device before assembly;

[0026] Figure 4 for Figure 3 A schematic diagram of the cross-sectional structure of a battery cell in the energy storage device shown;

[0027] Figure 5 for Figure 4 A schematic structural diagram of the first starting section of the first pole piece in the battery cell is shown.

[0028] Reference numerals: energy storage system 5000, electric energy conversion device 4500, wind energy conversion device 4000, second electric equipment 3000, energy storage device 1000, housing 100, 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, extension part 11, folded part 13, first starting end face 15, first middle section 20, first The finishing section 30, the first finishing end face 31, the second current collector 305, the second active layer 307, the second starting section 50, the second starting end face 51, the second middle section 60, the second finishing section 70, the second finishing end face 71, the starting film section 80, the first part 81, the second part 82, the middle film section 91, the finishing film section 92, the first pole ear 360, the second pole ear 370, the first surface 380, the second surface 390, the corner position A, and the widest position B. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] Taking electrochemical energy storage as an example, this solution provides an energy storage device, which has a group of chemical batteries in it. The chemical elements in the chemical batteries are mainly used as energy storage media. The charging and discharging process is accompanied by chemical reactions or changes in the energy storage media. Simply put, the electricity generated by wind and solar energy is stored in 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.

[0031] At present, 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 types of energy storage devices include:

[0032] (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, achieve load matching of electric energy in time and space, enhance the ability to absorb renewable energy, and are of great significance in grid system backup, relieving peak load power supply pressure, and peak and frequency regulation;

[0033] (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, the electricity in the energy storage equipment is discharged for use to achieve the purpose of saving electricity bills.

[0034] 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.

[0035] 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.

[0036] 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 the period of low electricity prices, and the energy storage device 1000 is used to store the electric energy and supply the first electric device or the second electric device during peak power 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 the first electric device or the second electric device during peak power 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.

[0037] It should be noted that the first power-consuming device, the second power-consuming device and other devices including the energy storage device 1000 can be understood as power-consuming devices.

[0038] See also Figure 2 and Figure 3 , Figure 2 for Figure 1 The schematic cross-sectional structure diagram of the energy storage device 1000 is shown in FIG. Figure 3 for Figure 2 The schematic diagram of the exploded structure of the energy storage device 1000 before assembly is shown.

[0039] For the convenience of description, we define Figure 2The energy storage device 1000 shown has a length direction of the X-axis direction, a width direction of the Y-axis direction, and a thickness direction of the Z-axis direction. The X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other.

[0040] The energy storage device 1000 includes a housing 100, a battery cell 300 and an electrolyte ( Figure 2 and Figure 3 (not shown), the battery cell 300 is installed on the inner side of the housing 100, and the electrolyte is filled on 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.

[0041] Specifically, the housing 100 may be an aluminum housing. The battery cell 300 may be one or more. 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 may 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, and the assembled energy storage device 1000 is a 2JR structure.

[0042] The energy storage device 1000 has a width skirt margin and a thickness skirt margin. Wherein, the width skirt margin = W2 / W1, 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. Thickness skirt margin = D2 / D1, 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. Wherein, 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. Exemplarily, the thickness D3 of the battery cell 300 is 30mm~38mm, and the width W2 is 166mm~171mm.

[0043] It should be understood that "width skirt margin>100%" means that the housing 100 and the battery cell 300 have an interference fit in the width direction, and "thickness skirt margin>100%" means that the housing 100 and the battery cell 300 have an interference fit in the thickness direction. Exemplarily, 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: 85%≤D2 / D1≤105%.

[0044] See also Figure 4 and Figure 5 , Figure 4 for Figure 3 The schematic diagram of the cross-sectional structure of the battery cell 300 in the energy storage device 1000 is shown. Figure 5 for Figure 4 The schematic diagram of the structure of the first starting section 10 of the first pole piece 310 in the battery cell 300 is shown. Figure 4 The middle dashed line represents the diaphragm 350 .

[0045] 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 wound by a material including a first pole piece 310, a second pole piece 330, and a diaphragm 350. The diaphragm 350 is disposed 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. 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 an anode piece, and the second pole piece 330 is a cathode piece. It is understandable that in other embodiments, the first pole piece 310 may also be a cathode piece, and the second pole piece 330 may be an anode piece.

[0046] Specifically, the first pole piece 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 pole piece 310 is 100μm to 140μm. Along the winding direction of the first pole piece 310, the first pole piece 310 includes a first starting section 10, a first middle section 20 and a first ending section 30, and the first middle section 20 is connected between the first starting section 10 and the first ending section 30. In this embodiment, 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.

[0047] Wherein, the first starting section 10 includes an extension portion 11 and a folded portion 13. The extension portion 11 extends in the Y-axis direction. The folded portion 13 is connected to the extension portion 11, and is folded relative to the extension portion 11 toward one side of the extension portion 11 along the thickness direction. In the present embodiment, the folded portion 13 is folded relative to the extension portion 11 toward one side of the extension portion 11 along the positive direction of the Z-axis. In the present embodiment, the surface of the folded portion 13 facing the extension portion 11 is bonded with the surface of the extension portion 11 facing the folded portion 13, that is, the first active layer 303 of the folded portion 13 along the thickness direction and facing the extension portion 11 is bonded with the first active layer 303 of the extension portion 11 along the thickness direction and facing the folded portion 13, so as to avoid further increasing the thickness of the first starting section 10 at the folded portion 13, thereby improving the uneven thickness distribution of the battery cell 300 and avoiding increasing the thickness of the battery cell 300.

[0048] Exemplarily, the extension length of the folded portion 13 is 10 mm to 30 mm. In this embodiment, the folded portion 13 is formed by extending the first starting section 10 by a certain length relative to the feeding position of the first pole piece 310, and folding the excess portion relative to the feeding position. The first starting section 10 is provided with a first starting end face 15. The first starting end face 15 is arranged along the winding direction of the first starting section 10. In this embodiment, the end face of the folded portion 13 that is arranged along the winding direction of the folded portion 13 and is away from the extension portion 11 is the first starting end face 15.

[0049] The first middle section 20 is connected to one end of the extension portion 11 away from the folded portion 13 to achieve the connection between the first middle section 20 and the extension portion 11, thereby achieving the connection between the first middle section 20 and the first starting section 10. In this embodiment, the first middle section 20 is wound in multiple layers along the winding direction of the battery cell 300. The first tail section 30 is connected to one end of the first middle section 20 away from the first starting section 10 to achieve the connection between the first middle 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 middle section 20, so that the first tail end face 31 is away from the first starting end face 15 of the first starting section 10 along the winding direction of the first pole piece 310.

[0050] 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 the present 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 150 μm to 200 μm. Exemplarily, in the present embodiment, the second pole piece 330 is made by mixing materials including a cathode active material, a conductive agent, an adhesive and a dispersant in a certain proportion, applying them to the second current collector 305 and then cold pressing. Exemplarily, the compaction density of the second pole piece 330 is 2.30 g / cm 3 ~2.60g / cm 3 The cathode active material may be lithium iron phosphate, the conductive agent may be carbon nanotubes (CNT), the adhesive may be polyvinylidene difluoride (PVDF), and the dispersant may be polyvinylpyrrolidone (PVP). For example, in some embodiments, the content of PVDF in the second active layer 307 is 1.0% to 4.0%.

[0051] Along the winding direction of the second pole piece 330, the second pole piece 330 includes a second starting section 50, a second middle section 60 and a second ending section 70, 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.

[0052] Specifically, the second starting section 50 extends in the Y-axis direction. The second starting section 50 and the folded portion 13 of the first starting section 10 are located on the same side of the extension portion 11 along the thickness direction of the extension portion 11. In this embodiment, the second starting section 50 is located on the side of the extension portion 11 along the positive direction of the Z-axis. The second starting section 50 and the folded portion 13 are arranged at intervals along the width direction of the battery cell 300. Among them, the second starting section 50 includes a second starting end face 51, which is arranged along the winding direction of the second starting section 50 and faces the folded portion 13. The second starting end face 51 and the first starting end face 15 of the folded portion 13 are arranged at intervals along the width direction of the battery cell 300, so as to realize that the second starting section 50 and the folded portion 13 are arranged at intervals along the width direction of the battery cell 300. In this embodiment, the second starting end face 51 is the feeding position of the second pole piece 330. Along the width direction of the battery cell 300, the spacing between the second starting end face 51 and the first starting end face 15 is H, and H>0. Among them, "the spacing H between the second starting end face 51 and the first starting end face 15 along the width direction of the battery cell 300" is also the minimum distance between the second starting end face 51 and the folded portion 13 along the width direction of the battery cell 300. Exemplarily, 0<H≤40mm. Along the width direction of the battery cell 300, the maximum distance between the second starting end face 51 and the folded portion 13 of the first starting section 10 in the first pole piece 310 is h. Exemplarily, 30mm≤h≤50mm. Among them, along the width direction of the battery cell 300, the position of the maximum distance between the folded portion 13 in the first starting section 10 and the second starting end face 51 is the corner position A of the first starting section 10, and the 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.

[0053] The second middle section 60 is connected to one end of the second starting section 50 away from the second starting end face 51 to achieve the connection between the second middle section 60 and the second starting section 50. In this embodiment, the second middle section 60 is wound in multiple layers along the winding direction of the battery cell 300. The second tail section 70 is connected to one end of the second middle section 60 away from the second starting section 50 to achieve the connection between the second middle 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 winding direction of the second tail section 70 and away from the second middle section 60, so that the second tail end face 71 is away from the second starting end face 51 of the second starting section 50 along the winding direction of the second pole piece 330.

[0054] Exemplarily, the thickness of the diaphragm 350 is 7 μm to 18 μm. Along the winding direction of the diaphragm 350, the diaphragm 350 includes a starting film segment 80, an intermediate film segment 91 and a tailing film segment 92. The intermediate film segment 91 is connected between the starting film segment 80 and the tailing film segment 92. Among them, the starting film segment 80 is arranged between the first starting segment 10 and the second starting segment 50 to isolate the first starting segment 10 and the second starting segment 50. The starting film segment 80 at least partially covers the folded portion 13 of the first starting segment 10. In this embodiment, along the winding direction of the starting film segment 80, the starting film segment 80 includes a first portion 81 and a second portion 82, the first portion 81 is located on the side of the extension portion 11 away from the folded portion 13, and is wound into multiple layers. The second portion 82 is connected to the first portion 81, and is isolated between the first starting segment 10 and the second starting segment 50, and completely covers the surface of the folded portion 13 in the first starting segment 10 along the thickness direction and away from the extension portion 11. By setting the first part 81 to be wound in multiple layers, the winding thickness of the first pole piece 310 and the second pole piece 330 on the inner side of the battery cell 300 is further increased, thereby reducing the curvature of the first pole piece 310 and the second pole piece 330 on the inner side, which is beneficial to improving the problem of active layer material falling off or even the risk of breakage of the first pole piece 310 or the second pole piece 330 due to excessive curvature.

[0055] The middle film segment 91 is isolated between the first middle segment 20 and the second middle segment 60 to isolate the first middle segment 20 and the second middle segment 60. The first middle segment 20 and the second middle segment 60 are located on both sides of the middle film segment 91 along the thickness direction of the middle film segment 91. The end film segment 92 is isolated between the first end segment 30 and the second end segment 70 to isolate the first end segment 30 and the second end segment 70. The first end segment 30 and the second end segment 70 are located on both sides of the end film segment 92 along the thickness direction of the end film segment 92.

[0056] The battery cell 300 further includes a first pole tab 360 and a second pole tab 370 . There may be a plurality of first pole tabs 360 , and the plurality of first pole tabs 360 are electrically connected to the first pole sheet 310 . There may be a plurality of second pole tabs 370 , and the plurality of second pole tabs 370 are electrically connected to the second pole sheet 330 .

[0057] In the battery cell 300 provided in this embodiment, the second starting section 50 of the second pole piece 330 is spaced apart from the folded portion 13 in the first starting section 10 of the first pole piece 310, so that the feeding position of the second pole piece 330 is shorter than the feeding position of the first pole piece 310, thereby allowing the first pole piece 310 to have sufficient lithium insertion positions to ensure that lithium is not deposited.

[0058] The applicant has found that the thickness distribution of the battery cell 300 at the feeding position of the first pole piece 310 and the feeding position of the second pole piece 330 is uneven, which will cause stress concentration in the battery cell 300 at the feeding position of the first pole piece 310 and the feeding position of the second pole piece 330. In order to solve the problem of inconsistent thickness of the battery cell 300 at the feeding position of the first pole piece 310 and the second pole piece 330 introduced when the feeding position of the second pole piece 330 is shorter than the feeding position of the first pole piece 310. In the embodiment of the present application, on the one hand, by folding the folded portion 13 in the first starting section 10 of the first pole piece 310 relative to the extended portion 11, the thickness of the first pole piece 310 at the folded portion 13 is increased, and the missing thickness at the feeding position of the second pole piece 330 is compensated, which is beneficial to improving the thickness consistency of the battery cell 300, thereby solving the problem of stress concentration in the battery cell 300 at the feeding position of the first pole piece 310 and the feeding position of the second pole piece 330, thereby reducing the risk of uneven current density distribution in the battery cell 300 at the stress concentration point. In addition, when the folded portion 13 of the first pole piece 310 and the second starting section 50 of the second pole piece 330 are located on different sides of the extended portion 11, the folded portion 13 is positively folded relative to the extended portion 11. Although it can make up for the missing thickness at the feeding position of the second pole piece 330, there is a layer of extended portion 11 between the folded portion 13 and the second starting section 50, which causes the battery cell 300 to produce a step-shaped crease under the action of external force, which is not conducive to improving the thickness consistency of the battery cell 300. In the embodiment of the present application, the folded portion 13 of the first pole piece 310 and the second starting section 50 of the second pole piece 330 are arranged on the same side of the extension portion 11, so that the folded portion 13 in the first starting section 10 of the first pole piece 310 is folded in the opposite direction relative to the extension portion 11, and there is no additional layer of extension portion 11 between the folded portion 13 and the second starting section 50. While compensating for the missing thickness at the feeding position of the second pole piece 330, it is more conducive to improving the uneven thickness distribution of the battery cell 300 caused by the feeding position of the second pole piece 330, and at the same time can solve the problem of stress concentration of the battery cell 300 at the feeding position of the first pole piece 310 and the feeding position of the second pole piece 330.

[0059] On the other hand, by setting the starting membrane segment 80 in the diaphragm 350 between the first starting segment 10 and the second starting segment 50, and at least partially covering the folded portion 13, the starting membrane segment 80 covering the folded portion 13 can further increase the thickness of the battery cell 300 at the folded portion 13 of the first pole piece 310, thereby further compensating for the missing thickness at the feeding position of the second pole piece 330, which is more conducive to improving the thickness consistency of the battery cell 300, and thereby reducing the risk of uneven current density distribution at the stress concentration point of the battery cell 300. In addition, the folded portion 13 and the second starting section 50 are separated only by the starting film section 80, which is ductile and will not produce creases under the action of external force. In the process of hot pressing or cold pressing to form the battery cell 300, the starting film section 80 can be deformed under external force to adjust the thickness at the folded portion 13 and the thickness at the second starting section 50, so as to further make up for the possible difference between the thickness of the battery cell 300 at the folded portion 13 and the thickness of the battery cell 300 at the second starting section 50, thereby further improving the thickness consistency of the battery cell 300, so that the battery cell 300 will not produce pressure marks, and further reduce the risk of uneven current density distribution at the stress concentration point of the battery cell 300. In addition, the starting film section 80 is used to isolate the first pole piece 310 and the second pole piece 330, and can also prevent the battery cell 300 from short circuiting.

[0060] In addition, the applicant has also found that when the feeding position of the second pole piece 330 is shorter than the feeding position of the first pole piece 310, the thickness of the battery cell 300 at the feeding position of the first pole piece 310 and the feeding position of the second pole piece 330 will be inconsistent, and the overall thickness of the battery cell 300 on one side of the feeding position of the first pole piece 310 is thin, so that during the process of hot pressing to form the battery cell 300, the curvature of the innermost second pole piece 330 is too large, which will lead to the risk of breaking the innermost second pole piece 330. The embodiment of the present application can also play a supporting role at the winding corner of the second pole piece 330 by setting the folded portion 13 of the first pole piece 310 to be folded relative to the extended portion 11, which is conducive to reducing the curvature of the second pole piece 330 at the corner, thereby helping to solve the problem of the active layer material falling off due to the excessive curvature of the second pole piece 330 and even the risk of breaking.

[0061] Continue reading Figure 4In 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, 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 pole piece 310, the second pole piece 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, and the widest position B of a second surface 390 refers to the position of a second surface 390 farthest from another second surface 390 along the width direction of the battery cell 300.

[0062] In this embodiment, the first end section 30 of the first pole piece 310 ends at the second surface 390, and the first end end surface 31 of the first end section 30 is located between the two first surfaces 380. Wherein, “the first end section 30 ends at the second surface 390” means that the first end end surface 31 of the first end section 30 does not extend to the first surface 380. In this embodiment, the first end section 30 extends in a direction parallel to the second surface 390.

[0063] The embodiment of the present application further optimizes the design of the tail position of the first pole piece 310, by setting the first tail end surface 31 between the two first surfaces 380, so as to achieve that the first tail section 30 of the first pole piece 310 does not go up the first surface 380 of the battery cell 300, thereby avoiding that the first tail section 30 of the first pole piece 310 goes up the first surface 380 and the first tail end surface 31 of the first tail section 30 becomes the highest point of the entire first surface 380. On the one hand, while ensuring that the capacity of the battery cell 300 can be normally exerted, the thickness of the battery cell 300 is avoided to be increased. This is beneficial for reducing 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 circulating battery cells 300 touch the shell. The stress points are then transmitted to the inner layers of the battery cells 300, so that the electrolyte at the stress points is squeezed out of the pole pieces, resulting in poor electrolyte infiltration, thereby causing excessive current density around the stress points, resulting in purple spots or lithium precipitation in the battery cells 300.

[0064] The second tail section 70 of the second pole piece 330 ends at the second surface 390. Wherein, "the second tail section 70 ends 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. Wherein, the second tail section 70 and the first tail section 30 end 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≥3.5mm.

[0065] In addition, the second end face 71 of the second end section 70 in the second pole piece 330 does not exceed the widest position B of the second surface 390. Wherein, "the second end face 71 does not exceed the widest position 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 a first surface 380 to the second surface 390, and the second end face 71 is located between the widest position B of the first surface 380 and the second surface 390. In this embodiment, the widest position B of the second surface 390 is the position at 1 / 2 of the thickness of the battery cell 300, the second surface 390 is approximately semi-arc-shaped, and the widest position B is approximately at 1 / 2 of the arc segment of the semi-arc-shaped second surface 390.

[0066] The embodiment of the present application also optimizes the design of the tail position of the second pole piece 330, by setting the second tail end face 71 not exceeding the widest position B of the second surface 390, so that the tail of the second pole piece 330 does not exceed the widest part of the battery cell 300, thereby avoiding the second tail section 70 of the second pole piece 330 exceeding the widest position B of the second surface 390, which causes the battery cell 300 to increase a 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, it is avoided to increase the width of the battery cell 300, thereby facilitating reducing the width skirt margin of the energy storage device 1000 formed by assembling the battery cell 300, and avoiding the high energy density lithium ion energy storage device with a relatively extreme design of the width skirt margin, which makes it difficult for the battery cell 300 to be inserted into the shell 100, and after the battery cell 300 is installed in the shell 100, the shell 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.

[0067] What is disclosed above is only a preferred embodiment of the present application, and it certainly cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A battery cell, characterized in that: The battery cell is formed by winding a material including a first electrode sheet, a diaphragm and a second electrode sheet, the diaphragm is arranged between the first electrode sheet and the second electrode sheet, the first electrode sheet includes a first starting section, the first starting section includes an extension portion and a folded portion, the folded portion is connected to the extension portion and folded toward one side of the extension portion along the thickness direction, the second electrode sheet includes a second starting section, the second starting section and the folded portion are located on the same side of the extension portion along the thickness direction of the extension portion, and are spaced apart from the folded portion along the width direction of the battery cell, the diaphragm includes a starting film section, the starting film section is arranged between the first starting section and the second starting section, and at least partially covers the folded portion; Along the winding direction of the starting film segment, the starting film segment includes a first portion and a second portion connected to the first portion, the first portion is located on the side of the extending portion away from the folded portion, and the first portion is wound into multiple layers, and the second portion covers the folded portion.

2. The battery cell according to claim 1, characterized in that: The folded portion includes a first starting end face facing a second starting section, the second starting section includes a second starting end face facing the folded portion, and along the extension direction of the extension portion, the second starting end face and the first starting end face are spaced apart along the width direction of the battery cell, and the distance between the second starting end face and the first starting end face is H, 0<H≤40mm.

3. The battery cell according to claim 2, characterized in that: Along the width direction of the battery core, the maximum distance between the second starting end surface and the folded portion is h, 30mm≤h≤50mm.

4. The battery cell according to claim 1, characterized in that: The surface of the folded portion facing the extending portion is in contact with the surface of the extending portion facing the folded portion.

5. The battery cell according to any one of claims 1 to 4, characterized in that: 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 also includes a first tailing section, which is arranged opposite to the first starting section along the winding direction of the first pole piece. The first tailing section includes a first tailing end face, which is arranged along the winding direction of the first tailing section and away from the first starting section. The first tailing section ends at one of the second faces, and the first tailing end face is located between the two first faces.

6. The battery cell according to claim 5, characterized in that: The second surface is a curved surface, and the second surface is provided with a widest position. The second pole piece also includes a second tailing section, and the second tailing section and the second starting section are arranged opposite to each other along the winding direction of the second pole piece. The second tailing section includes a second tailing end face, and the second tailing end face is arranged along the winding direction of the second tailing section and away from the second starting section. The second tailing section ends at one of the second surfaces, and the second tailing end face does not exceed the widest position.

7. The battery cell according to claim 6, 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 core, the first ending end surface exceeds the second ending end surface.

8. The battery cell according to claim 7, 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.

9. An energy storage device, characterized in that: The invention comprises a housing and a battery cell as claimed in any one of claims 1 to 8, wherein the battery cell is installed on the inner side of the housing.

10. The energy storage device according to claim 9, characterized in that: The energy storage device satisfies: 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.

11. The energy storage device according to claim 9, 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.

12. An electrical device, characterized in that: It comprises an energy storage device as described in any one of claims 9 to 11, wherein the energy storage device is used to supply power to the electrical equipment.

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