Battery cell and battery

Abstract

The invention provides a battery cell and a battery, the battery cell comprises a first pole piece and a second pole piece, the first pole piece and the second pole piece are different in polarity, and the first pole piece and the second pole piece are stacked and wound to form a roll core; the first pole piece comprises a first current collector and a first active material layer arranged on at least one side of the first current collector; the second pole piece comprises a second current collector and a second active material layer arranged on at least one side of the second current collector, and the second active material layer comprises a silicon-carbon composite material and / or a silicon-oxygen composite material; the positions, at least corresponding to the corner areas of the roll core, of the first pole piece are provided with pores, and the pores penetrate through the first current collector and the first active material layer in the first direction, so that the problems of deformation, breakage and the like of the pole piece are solved to a certain extent.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery cell and a battery. Background Art

[0002] Currently, lithium-ion batteries are widely used not only in portable electronic devices such as mobile phones and laptops, but also in electric equipment such as electric vehicles and electric bicycles.

[0003] The battery cell is the core component of the lithium-ion battery. The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. Since the negative electrode active layer in the negative electrode sheet is a silicon-containing active layer, the silicon content will affect the expansion of the negative electrode sheet during the charging and discharging process. The higher the silicon content in the negative electrode active layer, the greater the expansion of the negative electrode sheet, and the more severe the extrusion between the positive and negative electrode sheets, which can easily cause deformation and fracture of the electrode sheets, affecting the normal use of the battery cell. Summary of the invention

[0004] In view of this, the embodiments of the present invention are directed to providing a battery cell and a battery, so as to at least improve the problems of electrode deformation, fracture, etc. caused by expansion to a certain extent.

[0005] In a first aspect, the present invention provides a battery core, comprising a first pole piece and a second pole piece, wherein the first pole piece and the second pole piece have different polarities, and the first pole piece and the second pole piece are stacked and wound to form a winding core;

[0006] The winding core comprises a straight area and a corner area, wherein the corner area is located at two opposite sides of the straight area;

[0007] The first pole piece includes a first current collector and a first active material layer disposed on at least one side of the first current collector;

[0008] The second pole piece includes a second current collector and a second active material layer disposed on at least one side of the second current collector, wherein the second active material layer includes a silicon-carbon composite material and / or a silicon-oxygen composite material;

[0009] A pore is provided at least at a position of the first pole piece corresponding to the corner region, and the pore is provided through the first current collector and the first active material layer along the first direction.

[0010] Optionally, the total number of winding folds of the winding core is N, where N is a positive integer, and at least part of the pores are located in the N-1th fold and / or the Nth fold region of the first pole piece.

[0011] Optionally, in the direction from the winding head end of the winding core to the winding tail end of the winding core, the ratio of the length L1 of the pore located on the corner area to the length L of the corresponding corner area satisfies:

[0012] 1%≤L1 / L≤100%.

[0013] Optionally, in the direction from the winding head end of the winding core to the winding tail end of the winding core, the pores located on the corner area extend to the straight area.

[0014] Optionally, a length M of the pore extending to the straight area satisfies: M≤5 mm.

[0015] Optionally, the first pole piece is provided with the pore at a position corresponding to the straight area; the first pole piece is provided with a pole ear, and the pole ear is located in the straight area;

[0016] At least a portion of the pores located on the flat region at least partially overlaps with a projection of the position of the electrode tab in the thickness direction of the battery cell.

[0017] Optionally, in the direction from the winding head end of the winding core to the winding tail end of the winding core, the first pole sheet sequentially includes a double-sided area and a single-sided area, the single-sided area is an area where the first active material layer is provided on one side of the first current collector, and the double-sided area is an area where the first active material layer is provided on both sides of the first current collector;

[0018] The double-sided area is provided with the pores, and / or the single-sided area is provided with the pores.

[0019] Optionally, along the second direction, a ratio of a width d of the pore to a width D of the first pole piece satisfies: 5%≤d / D≤95%;

[0020] And / or, the pore extends to an edge of the first pole piece along the second direction;

[0021] And / or, in the direction from the winding inner circle to the winding outer circle of the winding core, at least two adjacent circles of the electrode sheets are provided with the pores, and at least part of the projections of the pores on at least two adjacent circles in the thickness direction of the battery core are overlapped;

[0022] And / or, the pores include a plurality of buffer holes penetrating the first pole piece along the first direction, and among all the buffer holes, at least a portion of the buffer holes are arranged at intervals along the second direction.

[0023] Optionally, in the direction from the inner winding circle to the outer winding circle of the winding core, the width of the pores on the outermost winding circle along the second direction is greater than the width of the pores on the innermost winding circle along the second direction;

[0024] and / or, in the direction from the winding inner circle to the winding outer circle of the winding core, the length of the pores on the outermost winding circle along the third direction is greater than the length of the pores on the innermost winding circle along the third direction;

[0025] And / or, there are a plurality of pores, and the plurality of pores are arranged at intervals along a direction from a winding head end of the first pole piece to a winding tail end of the first pole piece;

[0026] In the direction from the winding inner circle to the winding outer circle of the winding core, the number of pores located on the winding outermost circle is greater than the number of pores located on the winding innermost circle.

[0027] Optionally, along the first direction, the pores have different pore diameters at both ends.

[0028] Optionally, along the first direction, the pore diameter gradually decreases.

[0029] Optionally, the first pole piece includes a first portion and a second portion, and the second portion is located on one side of the first portion along the first direction;

[0030] The pore comprises a first pore segment and a second pore segment which are arranged opposite to each other and are connected, the first pore segment penetrates the first part along the first direction, and the second pore segment penetrates the second part along the first direction;

[0031] In the direction from the first pore segment to the second pore segment, the pore diameter of the first pore segment gradually decreases; in the direction from the second pore segment to the first pore segment, the pore diameter of the second pore segment gradually decreases.

[0032] Optionally, a plurality of recessed portions and a plurality of raised portions corresponding to the recessed portions are provided on the first active material layer, and the recessed portions are recessed toward the first current collector.

[0033] Optionally, the recessed portion and the pore are spaced apart;

[0034] and / or, along the third direction, a distance F between the recessed portion and the pore satisfies: 0.1 mm ≤ F ≤ 5 mm;

[0035] And / or, along the first direction, the first pole piece has a first side and a second side relative to each other, the recessed portion is formed by the first current collector and the first active material layer being recessed toward the second side, and the raised portion is formed at a position on the second side corresponding to the recessed portion and protruding toward a direction away from the first side.

[0036] Optionally, the pores are provided on both the first pole piece and the second pole piece.

[0037] Optionally, the pores on the second pole piece are arranged corresponding to the pores on the first pole piece, and the projection of the pores on the second pole piece on the first pole piece is located within the area enclosed by the pores on the first pole piece.

[0038] Optionally, an insulating layer is provided on the surface of the first pole piece facing the second pole piece, the insulating layer is provided corresponding to the pores on the first pole piece, and the projection of the pores on the second pole piece on the first pole piece is located in the area covered by the insulating layer.

[0039] In a second aspect, the present invention provides a battery, comprising a shell and the battery cell as described above, wherein the battery cell is located in the shell.

[0040] The battery cell and battery provided by the present invention, by making the second active material layer of the second pole piece of the battery cell include a silicon-carbon composite material and / or a silicon-oxygen composite material, and arranging pores at a position of at least the first pole piece of the battery cell corresponding to the corner area of ​​the winding core, so that along the first direction, the pores penetrate the first current collector and the first active material layer. In this way, when the silicon-doped second pole piece expands, for example, during the charging and discharging process, the presence of the pores on the first pole piece provides a reserved buffer space for the expansion of the second pole piece, which can effectively accommodate the volume expansion of the second pole piece, thereby effectively releasing the expansion stress of the second pole piece, at least reducing the expansion stress of the second pole piece in the corner area and the squeezing force between the first pole piece and the second pole piece, thereby reducing the risk of deformation and fracture of the first pole piece, the second pole piece, etc.

[0041] Moreover, by setting pores at least at the position corresponding to the corner area of ​​the winding core of the first pole piece, the wetting effect of the electrolyte can be improved to a certain extent, so that lithium ions can diffuse rapidly in the electrolyte, thereby improving the battery's kinetic performance and cycle performance.

[0042] In addition, since the pores run through the first current collector and the first active material layer, the amount of active material in the corner area of ​​the first pole piece is reduced to a certain extent, thereby reducing the amount of lithium ions received by the second pole piece, thereby at least making the corner area less prone to lithium deposition, reducing the risk of lithium deposition in the corner area, and improving the electrical performance, safety and life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The cross-sectional structure of the first pole piece according to an embodiment of the present invention is shown in FIG. Figure 1 ;

[0044] Figure 2 It is a schematic diagram of the partial structure of two adjacent circles of pole pieces in an unfolded state according to an embodiment of the present invention;

[0045] Figure 3A top view of a partial structure of a battery cell according to an embodiment of the present invention Figure 1 ;

[0046] Figure 4 It is a schematic structural diagram of a battery cell according to an embodiment of the present invention;

[0047] Figure 5 Schematic diagram of the local structure of the first pole piece in an unfolded state according to an embodiment of the present invention Figure 1 ;

[0048] Figure 6 Schematic diagram of the local structure of the first pole piece in an unfolded state according to an embodiment of the present invention Figure 2 ;

[0049] Figure 7 A top view of a partial structure of a battery cell according to an embodiment of the present invention Figure 2 ;

[0050] Figure 8 The cross-sectional structure of the first pole piece according to an embodiment of the present invention is shown in FIG. Figure 2 ;

[0051] Fig. 9 The cross-sectional structure of the first pole piece according to an embodiment of the present invention is shown in FIG. Figure 3 ;

[0052] Fig.10 The cross-sectional structure of the first pole piece according to an embodiment of the present invention is shown in FIG. Figure 4 ;

[0053] Fig.11 The cross-sectional structure of the first pole piece according to an embodiment of the present invention is shown in FIG. Figure 5 ;

[0054] Fig.12 The cross-sectional structure of the first pole piece according to an embodiment of the present invention is shown in FIG. Figure 6 ;

[0055] Fig.13 A partial structural cross-section of a battery cell according to an embodiment of the present invention Figure 1 ;

[0056] Fig.14 A partial structural cross-section of a battery cell according to an embodiment of the present invention Figure 2 .

[0057] Among them, 100, battery cell; 1, first pole piece; 10, pore; 101, buffer hole; 102, first pore section; 103, second pore section; 11, first current collector; 12, first active material layer; 13, corner area; 14, straight area; 15, double-sided area; 16, single-sided area; 17, empty foil area; 18, first side; 181, recessed portion; 19, second side; 191, raised portion; 2, second pole piece; 21, second current collector; 22, second active material layer; 3, pole ear; 31, pole ear protective tape; 4, diaphragm; 5, insulating layer. DETAILED DESCRIPTION

[0058] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0059] Lithium-ion batteries include a shell and a battery cell, which is the core component of lithium-ion batteries. The battery cell includes a positive electrode sheet, a negative electrode sheet and a separator. The separator is located between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet from contact with the negative electrode sheet. Among them, the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer arranged on the surface of the positive electrode collector. The negative electrode sheet includes a negative electrode collector and a negative electrode active material layer arranged on the surface of the negative electrode collector. The capacity of the battery is provided by the electrochemical reaction between the active material of the positive electrode active material layer and the active material of the negative electrode active material layer.

[0060] When the negative electrode active material layer is a silicon-containing active layer, the silicon content will affect the expansion of the negative electrode sheet during the charge and discharge process. The higher the silicon content in the negative electrode active layer, the greater the expansion of the negative electrode sheet, and the more severe the compression between the positive and negative electrode sheets, which can easily cause deformation and breakage of the electrode sheet, affecting the normal use of the battery cell.

[0061] Based on this, an embodiment of the present invention provides a battery cell and a battery, in which the active material layer of the second pole piece of the battery cell is a silicon-doped active layer, and pores are arranged at a position of at least the first pole piece of the battery cell corresponding to the corner area of ​​the winding core, so that along the first direction, the pores penetrate the first current collector and the first active layer of the first pole piece. The presence of the pores can effectively accommodate the volume expansion of the second pole piece, reduce the expansion stress of the second pole piece and the squeezing force between the first pole piece and the second pole piece, thereby improving the deformation, fracture and other problems of the pole piece to a certain extent.

[0062] The following is a detailed description of the battery cell and battery provided by the present invention through specific embodiments in conjunction with the accompanying drawings:

[0063] Reference Figures 1 to 14As shown, this embodiment provides a battery cell 100, which is applied to a battery, and the battery may be, for example, a lithium-ion battery.

[0064] The battery cell 100 may specifically include: a first pole piece 1, a second pole piece 2 and a diaphragm 4. The first pole piece 1 and the second pole piece 2 have different polarities. The diaphragm 4 is located between the first pole piece 1 and the second pole piece 2.

[0065] Reference Figure 4 As shown, the first pole piece 1 , the diaphragm 4 and the second pole piece 2 are stacked and wound to form a winding core. The winding core includes a straight area 14 and a corner area 13 , and the corner area 13 is located on two opposite sides of the straight area 14 .

[0066] The first pole piece 1 specifically includes: a first current collector 11 and a first active material layer 12 disposed on at least one side of the first current collector 11. The first current collector 11 has two opposite sides, and the two opposite sides are used to coat the first active material layer 12. In specific implementation, the first active material layer 12 can be disposed on both sides of the first current collector 11, or only on one side of the first current collector 11, which can be set according to actual needs.

[0067] The second pole piece 2 specifically includes: a second current collector 21 and a second active material layer 22 disposed on at least one side of the second current collector 21. The second current collector 21 has two opposite sides, and the two opposite sides are used to coat the second active material layer 22. In specific implementation, the second active material layer 22 can be disposed on both sides of the second current collector 21, or only on one side of the second current collector 21, which can be set according to actual needs.

[0068] Exemplarily, the first electrode sheet 1 may be a positive electrode sheet, and the second electrode sheet 2 may be a negative electrode sheet.

[0069] Specifically, the first current collector 11 is, for example, aluminum foil, and the material of the first active material layer 12 can be, for example, positive electrode active materials such as lithium cobalt oxide, ternary materials or lithium iron phosphate.

[0070] The second current collector 21 may be, for example, a copper foil, and the second active material layer 22 includes a silicon-carbon composite material and / or a silicon-oxygen composite material. In other words, the negative electrode sheet may be formed as a silicon-doped negative electrode sheet.

[0071] In specific implementation, the silicon content in the second active material layer will affect the expansion of the second electrode during the charge and discharge process. The higher the silicon content, the greater the expansion of the second electrode. If the expansion of the second electrode is not effectively alleviated, the compression between the first electrode and the second electrode will be more severe, resulting in risks such as deformation and fracture of the electrode. Based on this, refer to Figure 1 and Figure 4As shown, a pore 10 is provided at least at a position corresponding to the corner area 13 of the first pole piece 1 , and the pore 10 is provided through the first current collector 11 and the first active material layer 12 along the first direction.

[0072] Reference Figure 1 As shown, the first direction here can be specifically Figure 1 The up-down direction in the figure may be, for example, the thickness direction of the first pole piece 1 .

[0073] Since the pore 10 is provided at least at the position corresponding to the corner area 13 of the first pole piece 1, the existence of the pore 10 provides a reserved buffer space for the expansion of the second pole piece 2, which can effectively accommodate the volume expansion of the second pole piece 2, reduce the expansion stress of the second pole piece 2, and reduce the squeezing force between the first pole piece 1 and the second pole piece 2, thereby reducing the risk of deformation and fracture of the pole piece.

[0074] In the actual manufacturing process, the corner area 13 is generally subjected to greater compression during winding. When the second pole piece 2 expands in volume, the corner area 13 is relatively more prone to deformation, fracture and other risks. By locating at least part of the pores 10 in the corner area 13, a certain buffer space is provided for the expansion of the second pole piece 2, at least reducing the expansion stress of the pole piece in the corner area 13, thereby at least to some extent avoiding the risk of deformation, wrinkling or fracture of the pole piece in the corner area 13. This arrangement can also release the stress of the corner area 13 itself and improve the strength and stability of the corner area 13.

[0075] Moreover, by providing the pores 10 on the first pole piece 1, the wettability of the electrolyte can be improved to a certain extent, so that lithium ions can diffuse rapidly in the electrolyte, thereby improving the dynamic performance and cycle performance of the battery.

[0076] In addition, since the pore 10 runs through the first current collector 11 and the first active material layer 12, the amount of active material in the corner area 13 of the first pole piece 1 is reduced to a certain extent, thereby reducing the amount of lithium ions received by the second pole piece 2, so that at least the corner area 13 is not easy to deposit lithium, reducing the risk of lithium deposition in the corner area 13, and improving the electrical performance, safety and life of the battery.

[0077] In specific implementation, the pores 10 can be punched out on the first pole piece 1 by mechanical punching, or can be formed on the first pole piece 1 by laser ablation. In addition, after laser ablation, the generated waste can be removed by combining negative pressure adsorption transfer, for example. That is, the active material layer and the current collector at the set position are removed together by mechanical punching or laser ablation, so as to form the pores 10 at the set position.

[0078] In addition, in a specific implementation, the above-mentioned pores 10 can be formed at least at the position corresponding to the corner area 13 of the first pole piece 1 by mechanical punching, laser ablation, etc. in any process before or after rolling the first pole piece 1 or before winding.

[0079] Continue to refer to Figure 1 As shown, in a specific implementation, one pore 10 may be provided on the first pole piece 1 , or a plurality of pores 10 may be provided on the first pole piece 1 , and the plurality of pores 10 are arranged at intervals on the first pole piece 1 .

[0080] The battery cell provided in this embodiment is configured such that the second active material layer 22 of the second pole piece 2 of the battery cell 100 includes a silicon-carbon composite material and / or a silicon-oxygen composite material, and a pore 10 is provided at a position of at least the first pole piece 1 of the battery cell 100 corresponding to the corner area 13 of the winding core, so that along the first direction, the pore 10 penetrates the first current collector 11 and the first active material layer 12. In this way, when the silicon-doped second pole piece 2 expands, for example, during the charging and discharging process, the presence of the pore 10 on the first pole piece 1 provides a reserved buffer space for the expansion of the second pole piece 2, which can effectively accommodate the volume expansion of the second pole piece 2, thereby effectively releasing the expansion stress of the second pole piece 2, at least reducing the expansion stress of the second pole piece 2 in the corner area 13 and the squeezing force between the first pole piece 1 and the second pole piece 2, thereby reducing the risk of deformation and fracture of the first pole piece 1, the second pole piece 2, etc.

[0081] Moreover, by providing the pores 10 at least at the position corresponding to the winding core corner area 13 of the first pole piece 1, the wetting effect of the electrolyte can be improved to a certain extent, so that lithium ions can diffuse rapidly in the electrolyte, thereby improving the dynamic performance and cycle performance of the battery.

[0082] In addition, since the pore 10 runs through the first current collector 11 and the first active material layer 12, the amount of active material in the corner area 13 of the first pole piece 1 is reduced to a certain extent, thereby reducing the amount of lithium ions received by the second pole piece 2, so that at least the corner area 13 is not easy to deposit lithium, reducing the risk of lithium deposition in the corner area 13, and improving the electrical performance, safety and life of the battery.

[0083] In some embodiments, the mass percentage of the silicon-carbon composite material and / or the silicon-oxygen composite material in the second active material layer 22 may be less than or equal to 50 wt %, for example, 1.5-40 wt %.

[0084] The silicon-carbon composite material includes a porous carbon matrix, silicon grains in the pores of the porous carbon matrix, and a carbon layer on the surface of the porous carbon matrix. For example, the silicon grains can be disposed in the pores of the porous carbon matrix by deposition, by disposing the silicon grains in the pores, and by forming a carbon layer on the surface of the porous carbon matrix, the carbon layer can be shaped carbon or amorphous carbon. When the silicon grains expand, the interior of the porous carbon matrix can provide sufficient expansion space to prevent the overall structure of the silicon-carbon composite material from deforming, and the carbon layer can constrain the outward expansion force of the porous carbon matrix during the silicon expansion process, ensuring the structural strength of the silicon-carbon material, thereby avoiding the cracking, pulverization, and shedding of the second active material layer 22, improving the cycle performance and rate performance of the battery, and further avoiding the deformation and fracture of the first pole piece 1 and the second pole piece 2 due to expansion and extrusion.

[0085] In a specific embodiment, the carbon layer includes openings arranged corresponding to the pores of the porous carbon matrix. When the openings are arranged on the carbon layer, the wettability of the electrolyte to the second pole piece 2 can be improved, and the expansion performance of the silicon-based material can be reduced, and the expansion stress of the second pole piece 2 can be reduced, thereby reducing the impedance of the battery, improving the cycle performance and rate performance of the battery, and further avoiding the deformation and fracture of the second pole piece 2 and the first pole piece 1.

[0086] In a specific embodiment, the specific surface area of ​​the silicon-carbon composite material and / or the silicon-oxygen composite material is 0.5-10 m 2 / g, for example 0.5m 2 / g, 1m 2 / g, 2m 2 / g, 3m 2 / g, 4m 2 / g, 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g or 10m 2 When the specific surface area of ​​the silicon-carbon composite material is within the above range, the SEI film formed on the surface of the second active material layer 22 during the charge and discharge process is appropriate, which can reduce the impedance of the battery and improve the cycle performance and rate performance of the battery.

[0087] In a specific embodiment, the particle size Dv50 of the silicon-carbon composite material and / or the silicon-oxygen composite material is 6-15 μm, for example, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm. When the particle size Dv50 of the silicon-carbon composite material and / or the silicon-oxygen composite material is within the above range, the particle size Dv50 of the silicon-carbon composite material is appropriate, which can avoid the situation where the particle size is too small, which easily leads to an increase in the specific surface area of ​​the silicon particles and an increase in side reactions, and can also avoid the situation where the particle size is too large, which easily leads to excessive expansion of the silicon particles, resulting in blocking of the pores of the porous carbon matrix and affecting the infiltration of the electrolyte, thereby improving the cycle performance and rate performance of the battery.

[0088] In a specific embodiment, the powder resistivity of the silicon-carbon composite material and / or the silicon-oxygen composite material is 0.1-1000Ω·cm, for example, 0.1Ω·cm, 0.5Ω·cm, 1Ω·cm, 5Ω·cm, 10Ω·cm, 50Ω·cm, 100Ω·cm, 200Ω·cm, 300Ω·cm, 400Ω·cm, 500Ω·cm, 600Ω·cm, 700Ω·cm, 800Ω·cm, 900Ω·cm or 1000Ω·cm. When the powder resistivity of the silicon-carbon composite material is within the above range, the conductivity of the silicon-carbon composite material is high, and the conductivity of the second active material layer 22 can be improved, thereby improving the cycle performance and rate performance of the battery.

[0089] In a specific embodiment, the silicon content in the silicon-carbon composite material and / or the silicon-oxygen composite material is 30-75%, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%, etc. When the silicon content in the silicon-carbon composite material and / or the silicon-oxygen composite material is within the above range, it is possible to avoid excessive silicon content in the silicon-carbon composite material and / or the silicon-oxygen composite material, which leads to excessive expansion of the silicon-carbon composite material and / or the silicon-oxygen composite material, and deformation of the overall structure of the silicon-carbon composite material and / or the silicon-oxygen composite material, thereby avoiding cracking and pulverization of the negative electrode active layer, ensuring the energy of the silicon-carbon composite material and / or the silicon-oxygen composite material, and improving the cycle performance and rate performance of the battery; at the same time, it is further possible to avoid deformation and fracture of the pole piece due to expansion and extrusion.

[0090] If the length of the pores in the corner area is too long, it will cause the pole piece to break prematurely, but if the length of the pores in the corner area is too short, it will reduce the buffering effect on expansion. Figure 5 As shown, in some embodiments, in the direction from the winding head end to the winding tail end of the winding core, the ratio of the length L1 of the pore 10 located on the corner area 13 to the length L of the corresponding corner area 13 satisfies: 1%≤L1 / L≤100%.

[0091] The winding head end here can be understood as the area where the winding of the battery cell starts during the winding process, that is, the head area, which is located inside the battery cell. Correspondingly, the winding tail end can be understood as the area where the battery cell is wound to the end.

[0092] Reference Figure 5 and Figure 6 As shown, in the direction from the winding head end to the winding tail end of the winding core, it can be specifically Figure 5 and Figure 6 The left and right directions in the figure are, for example, the length direction of the first pole piece 1 in the unfolded state. The length L1 of the pore 10 in the corner area 13 can be specifically the length of the pore 10 in the corner area 13 along the Figure 5 The length in the left-right direction.

[0093] Exemplarily, the ratio of L1 / L may be, for example, 1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%.

[0094] By setting the length of the pore 10 on the corner area 13 as above, the pore 10 on the corner area 13 does not exceed the corner area 13. While ensuring the buffering effect of the pore 10 on the expansion of the pole piece, the structural strength and stability of the corner area 13 are guaranteed, avoiding the premature fracture of the first pole piece 1.

[0095] The cross-section of the pore 10 may be circular, elliptical, square, etc., which is not particularly limited in this embodiment.

[0096] It should be noted that Figure 5 In the above, a single hole 10 is provided on the corner area 13. Of course, a plurality of holes 10 may also be provided on the corner area 13. Figure 6 As shown, for example, two pores 10 are provided on the corner area 13, and the two pores 10 are arranged at intervals along the left-right direction. The lengths of the two pores 10 on the corner area 13 are both L11, for example. In this case, the length L1 of the above-mentioned pore 10 refers to the sum of the lengths L11 of the two pores 10 arranged along the left-right direction.

[0097] Continue to refer to Figure 6 As shown, in the direction from the winding head end of the winding core to the winding tail end of the winding core, the pores 10 located on the corner area 13 extend to the straight area 14.

[0098] By extending the pore 10 from the corner area 13 to the straight area 14, the buffer space can be further increased, thereby effectively alleviating the expansion force on the electrode, reducing the expansion stress of the second electrode 2, further reducing the squeezing force between the first electrode 1 and the second electrode 2, and further improving the wettability of the electrolyte, thereby improving the cycle performance of the battery.

[0099] In specific implementation, if the length of the pore 10 extending from the corner area 13 to the straight area 14 is too large, a large stress difference will occur in the first pole piece 1, thereby affecting the performance of the interface layer of the first pole piece 1. Based on this, in some embodiments, the length M of the pore 10 extending to the straight area 14 can satisfy: M≤5mm.

[0100] The length M here is the length of the pore 10 extending to the straight area 14 along the Figure 6 The dimension in the left-right direction. Exemplarily, the length M may be, for example, 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm.

[0101] By setting the length of the pore 10 extending to the straight area 14 within the above range, it is avoided that the extension length is too long and causes a large stress difference in the first pole piece 1, thereby affecting the performance of the interface layer of the first pole piece 1. Moreover, such a setting can ensure the structural strength of the connection area between the corner area 13 and the straight area 14 to a certain extent, thereby ensuring the stability of the first pole piece 1.

[0102] For example, refer to Figure 6 As shown, both ends of the pore 10 in the corner area 13 along the left-right direction can extend to the corresponding straight area 14. Of course, one end of the pore 10 can also extend to the corresponding straight area 14.

[0103] Continue to refer to Figure 4 ,like Figure 4 As shown at A in FIG. 1 , in some embodiments, a hole 10 is further provided at a position of the first pole piece 1 corresponding to the straight region 14 .

[0104] This arrangement can at least alleviate the expansion of the flat area 14, for example, Figure 4 As shown in A, the pores 10 are arranged in the flat area 14 corresponding to the positive electrode sheet. When the negative electrode sheet expands, the existence of the pores 10 can better accommodate the expansion of the electrode material, such as providing expansion space for the negative electrode sheet located in the inner or outer circle of the positive electrode sheet, thereby reducing the expansion stress of the negative electrode sheet and avoiding deformation and fracture of the electrode sheet. Moreover, at least part of the pores 10 are arranged in the flat area 14, which improves the wettability of the electrolyte and the ion transmission rate, and improves the charging, discharging, and cycling performance of the battery.

[0105] In specific implementation, in different areas of the battery cell, there may be a difference in thickness of the battery cell 100 in the thickness direction due to the different number of diaphragm layers, pole piece layers, adhesive tape layers, and the arrangement of the pole lug 3. Based on this, in some embodiments, the pores 10 may be arranged in the area of ​​the first pole piece 1 corresponding to the thicker battery cell 100, so as to reduce the total thickness of the battery cell 100 to a certain extent, thereby facilitating the improvement of the unit volume energy density of the battery cell 100. In other words, while providing a buffer space for the expansion of the electrode material, the unit volume energy density of the battery cell 100 is also improved.

[0106] Combination Figure 4 and Figure 7 As shown, in some embodiments, a pole ear 3 is provided on the first pole piece 1, and the pole ear 3 is located in the straight area 14. Specifically, a pole ear protection tape 31 can be attached to the position of the first pole piece 1 corresponding to the pole ear 3 to protect the pole ear 3, and the provision of the pole ear protection tape 31 can prevent the positive and negative electrodes from being short-circuited.

[0107] Continue to refer to Figure 4 As shown in A of FIG. 1 , in some embodiments, at least a portion of the pores 10 located on the flat area 14 may overlap at least a portion of the projection of the position of the tab 3 in the thickness direction of the battery cell 100. The thickness direction may be Figure 4 This arrangement provides a buffer space for the expansion of the electrode sheet and reduces the total thickness of the battery cell 100 to a certain extent, thereby facilitating the improvement of the energy density per unit volume of the battery cell 100.

[0108] Of course, the pores 10 may also be disposed in other thicker regions of the battery cell 100 to improve the energy density per unit volume of the battery cell 100 while alleviating the expansion.

[0109] Combination Figure 4 and Figure 8 As shown, in some embodiments, in the direction from the winding head end to the winding tail end of the winding core, the first pole piece 1 may include a double-sided area 15 , a single-sided area 16 and a hollow foil area 17 .

[0110] The double-sided area 15 specifically refers to the first current collector 11 corresponding to the section of the first pole piece 1, both sides of which are coated with the first active material layer 12. The single-sided area 16 specifically refers to the first current collector 11 corresponding to the section of the first pole piece 1, only one side of which is coated with the first active material layer 12. The empty foil area 17 specifically refers to the first current collector 11 corresponding to the section of the first pole piece 1, which is not coated with the first active material layer 12.

[0111] In some embodiments, continue to refer to Figure 8 As shown, at least part of the pores 10 can be arranged in the double-sided area 15, that is, along the Figure 8In the up-down direction, the pores 10 are arranged through the double-sided area 15. One pore 10 can be arranged on the double-sided area 15, or a plurality of pores 10 can be arranged.

[0112] Since the thickness of the double-sided area 15 is relatively thick, by setting the pores 10 in the double-sided area 15, a larger expansion buffer space can be provided for the expansion of the second pole piece 2, so that the volume expansion of the second pole piece 2 can be further effectively accommodated, and the squeezing force between the first pole piece 1 and the second pole piece 2 is reduced, and the stress of the first pole piece 1 can be reduced, further reducing the risk of deformation and fracture of the first pole piece 1 and the second pole piece 2.

[0113] In some embodiments, continue to refer to Figure 8 As shown, at least part of the pores 10 can also be arranged in the single-sided area 16, that is, along the Figure 8 In the up and down directions, the pores 10 are arranged through the single-sided area 16. One pore 10 can be arranged on the single-sided area 16, and a plurality of pores 10 can also be arranged.

[0114] During the battery cell manufacturing process, the single-sided area 16 of the first pole piece 1 is thinner than the double-sided area 15, and the single-sided area 16 is easily over-pressurized. Over-pressurization can easily lead to poor electrolyte infiltration in this area, thereby reducing the battery's charging and discharging performance, cycle performance, etc. By setting at least part of the pores 10 in the single-sided area 16, not only a certain expansion buffer space is provided to reduce the expansion stress of the second pole piece 2, and reduce the squeezing force between the first pole piece 1 and the second pole piece 2, thereby reducing the risk of deformation and fracture of the first pole piece 1, the second pole piece 2, etc., but also, the electrolyte infiltration effect is improved to a certain extent, thereby improving the battery's charging and discharging, cycle and other performances.

[0115] Reference Figure 8 As shown, in some embodiments, pores 10 may be provided on both the double-sided area 15 and the single-sided area 16 to further increase the expansion buffer space, and thus make the force on the first pole piece 1 more uniform, further improving the structural stability of the first pole piece 1.

[0116] Specifically, the total number of winding folds of the first pole piece 1 is N, where N is a positive integer, that is, in the direction from the inner winding circle to the outer winding circle, the corresponding folds are C1, C2, C3, C4, C5...C N-1 , C N .

[0117] Continue to refer to Figure 4 ,like Figure 4 As shown at B, in some embodiments, at least part of the pores 10 may be located in the region of the N-1th fold and / or the Nth fold of the first pole piece 1 .

[0118] The further to the outer circle, the greater the expansion force on the pole piece. By making at least part of the pores 10 located in the N-1th fold and / or the Nth fold area of ​​the first pole piece 1, it can further ensure that the expansion stress of the pole piece located in the outer circle is effectively alleviated, and further avoid deformation, fracture and the like of the first pole piece 1, the second pole piece 2 and the like.

[0119] Reference Figure 4 As shown, in some embodiments, at least part of the pores 10 may be arranged at C N-1 , C N The corner area 13 corresponding to the number of folds can further reduce the expansion stress of the pole piece in the corner area 13, relieve the stress in the corner area 13, improve the structural strength and stability of the corner area 13, and avoid the breakage and deformation of the pole piece.

[0120] If the width of the pore 10 is too large, the first pole piece 1 will break prematurely. However, if the width of the pore 10 is too small, the buffer space will be small, thereby reducing the expansion buffer effect. Figure 5 As shown, in some embodiments, along the second direction, the ratio of the width d of the pore 10 to the width D of the first pole piece 1 satisfies: 5%≤d / D≤95%.

[0121] The second direction here can be specifically Figure 5 In the vertical direction, for example, the width direction of the first electrode 1, the width d of the pore 10 is the width of the pore 10 along the Figure 5 The dimension in the vertical direction is the width D of the first pole piece 1, that is, the width D of the first pole piece 1 along the Figure 5 The size in the upper and lower directions.

[0122] Exemplarily, the ratio of d / D may be, for example, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95%.

[0123] It should be noted that Figure 5 The example description is based on the fact that the region of the first pole piece 1 has one pore 10 along the second direction. Of course, in other implementations, the first pole piece 1 may also have multiple pores 10 along the second direction, such as multiple pores 10 arranged at intervals along the second direction. In this case, the width d of the pore 10 specifically refers to the sum of the widths of the multiple pores 10 arranged in a row along the second direction.

[0124] By setting the width of the pore 10 within the above range, while ensuring that the pore 10 can provide sufficient buffer space for the expansion of the second pole piece 2, the structural strength and stability of the first pole piece 1 in the corresponding area are guaranteed, thereby avoiding premature fracture of the first pole piece 1.

[0125] The above-mentioned size setting of the pores 10 is applicable to the pores 10 on the corner area 13 as well as the pores 10 on the straight area 14 .

[0126] In a specific implementation, the pore 10 may include a plurality of buffer holes 101 penetrating the first pole piece 1 along a first direction, and the plurality of buffer holes 101 are arranged at intervals on the first pole piece 1 .

[0127] Reference Figure 2 As shown, illustratively, among all the buffer holes 101, at least a portion of the buffer holes 101 can be arranged along the second direction of the first pole piece 1 (specifically, Figure 2 They are arranged at intervals in the up and down direction, for example, the width direction of the first pole piece 1.

[0128] Continue to refer to Figure 2 and Figure 3 As shown, in some embodiments, the pore 10 may be extended to the edge of the first pole piece 1 along the second direction.

[0129] The second direction here can be specifically Figure 2 The vertical direction in the second direction is, for example, the width direction of the first pole piece 1. The pore 10 may extend to the upper edge of the first pole piece 1 along the second direction, or may extend to the lower edge of the first pole piece 1 along the second direction.

[0130] This arrangement further increases the buffer space, so that the pole piece can be relieved from expansion to a certain extent in both the length and width directions, thereby further reducing the expansion stress of the second pole piece 2, and further reducing the squeezing force between the first pole piece 1 and the second pole piece 2, thereby avoiding deformation and breakage of the first pole piece 1, the second pole piece 2, etc.

[0131] Continue to refer to Figure 2 and Figure 3 As shown, in some embodiments, in the direction from the inner winding circle to the outer winding circle of the winding core, pores 10 are provided on at least two adjacent circles of the pole pieces, and the projections of the pores 10 on at least two adjacent circles in the thickness direction of the battery cell 100 are at least partially overlapped.

[0132] Exemplary, combined Figure 2 and Figure 3 As shown, for example, when Figure 2 The first pole piece 1 and the second pole piece 2 are stacked and arranged along Figure 2 After winding from left to right in the figure, the area where the pores 10 indicated by S2 are located is located just in the adjacent outer circle of the area where the pores 10 indicated by S1 are located.

[0133] The at least partial overlapping arrangement of the projections of the pores 10 on at least two adjacent circles in the thickness direction of the battery cell may specifically be: for a wound battery cell, the projections of the pores 10 on at least two adjacent circles on the same surface are partially staggered and the other partially overlapped, or the projections of the pores 10 on at least two adjacent circles completely overlap.

[0134] The projection here can be, for example, the aperture 10 at Figure 3 Projection on paper shown.

[0135] With such an arrangement, for example, in the direction from the outer circle to the inner circle of the battery cell 100, the gaps 10 on the two adjacent circles form a larger connected space as a whole, thereby further increasing the expansion buffer space of the second pole piece 2, so that the expansion of the pole piece in multiple directions can be effectively buffered, thereby further reducing the expansion stress of the second pole piece 2 and the squeezing force between the first pole piece 1 and the second pole piece 2, thereby further reducing the risk of breakage and deformation of the first pole piece 1 and the second pole piece 2.

[0136] Combination Figure 2 and Figure 3 Further explanation: Figure 3 The solid line pores in the figure are specifically the pores 10 indicated by S2. Figure 3 The dotted pores in the figure are specifically the pores 10 indicated by S1. After the battery cell is wound, the projections of the pores 10 indicated by S1 and the pores 10 indicated by S2 are partially overlapped and partially offset, so that the pores 10 on at least two adjacent circles form a large connected space as a whole along the direction from the inner circle to the outer circle of the winding. For example, the combination of the two circles of pores 10 forms a long strip of connected pores as a whole, thereby further increasing the expansion buffer space for the electrode material, thereby further improving the expansion relief effect of the electrode material, and further reducing the risk of fracture and deformation of the electrode piece.

[0137] Of course, in other embodiments, the apertures 10 on two adjacent circles may also be completely staggered.

[0138] Figure 3 The following description is made by taking the case where two adjacent circles of pole pieces are provided with apertures 10 at the same radial position of the corresponding winding core. Of course, it is also possible that three adjacent circles of pole pieces or more than three circles of pole pieces are provided with apertures 10.

[0139] In addition, on this basis, part of the pores 10 also extend to the edge of the first pole piece 1, thereby further improving the buffering effect, further reducing the expansion stress of the second pole piece 2, and effectively preventing the first pole piece 1, the second pole piece 2, etc. from deformation and breakage.

[0140] In some embodiments, along the direction from the inner winding circle to the outer winding circle of the winding core, the width of the pores 10 on the outermost winding circle along the second direction can be greater than the width of the pores 10 on the innermost winding circle along the second direction. The second direction can be, for example, the width direction of the first pole piece 1.

[0141] The length of the pores 10 on the outermost winding circle along the third direction can also be greater than the length of the pores 10 on the innermost winding circle along the third direction. The third direction here is the direction from the winding head end to the winding tail end of the winding core, for example, it can be the length direction of the first pole piece 1.

[0142] In addition, when there are multiple pores 10, the number of pores 10 located on the outermost winding circle can be greater than the number of pores 10 located on the innermost winding circle.

[0143] For example, the further outward the circle is, the larger the size of the corner area 13 is. By making the size and / or number of the pores 10 located on the outermost circle larger, the expansion buffer space can be further increased, thereby further reducing the risk of deformation and fracture of the pole piece.

[0144] Moreover, the closer to the outer ring of the winding, the greater the expansion force on the pole piece section located at the outer ring of the winding. The above arrangement can better alleviate the expansion of the outer ring pole piece, thereby effectively alleviating the expansion of the entire battery cell, further reducing the risk of deformation and breakage of the pole piece.

[0145] For example, let C N The length of the pore 10 on the fold is greater than that at C N-1 The length of the pore 10 on the fold, or, N The width of the pore 10 on the fold is greater than that at C N-1 The width of the folded aperture 10, or, N The number of buffer holes 101 on the fold is more than C N-1 The number of buffer holes on the fold can better accommodate the volume expansion of the electrode material and further improve the occurrence of problems such as deformation and breakage of the electrode.

[0146] Reference Fig. 9 As shown, in some embodiments, along the first direction, the pore diameters at both ends of the pore 10 are different.

[0147] The first direction here can be specifically Fig. 9 The vertical direction in the vertical direction is, for example, the thickness direction of the first pole piece 1. The aperture of the pore 10 is specifically the diameter of the pore 10 along the Fig. 9 The two ends of the pore 10 refer to the pore 10 along the left and right directions. Fig. 9 The upper and lower ends in the up-down direction.

[0148] This arrangement not only provides a certain expansion buffer space for the second pole piece 2, but also makes it difficult for the first pole piece 1 to collapse during the winding or hot pressing process of the pole piece, thereby improving the structural stability of the first pole piece 1 and the battery cell. In addition, it can also improve the wetting effect of the electrolyte to a certain extent, thereby improving the charging, discharging, and cycling performance of the battery.

[0149] In some embodiments, the aperture of the pore 10 can be gradually reduced along the first direction. That is, the cross-section of the pore 10 is a trapezoidal structure. This arrangement further increases the expansion buffer space, so that the expansion of the second pole piece 2 is further effectively alleviated; and this makes the pore 10 easier to manufacture, reducing the difficulty of manufacture; in addition, it further makes it difficult for the first pole piece 1 to collapse during the winding or hot pressing process of the first pole piece 1, thereby improving the structural stability of the first pole piece 1 and the battery cell; it also improves the infiltration effect of the electrolyte, thereby improving the charging, discharging, and cycling performance of the battery; it can also prevent powder from falling off during the manufacture of the pore 10 to a certain extent, thereby improving the structural strength of the first pole piece 1, and ensuring the amount of the active material layer of the first pole piece 1, and ensuring the capacity and other performance of the battery to a certain extent.

[0150] For example, taking the method of laser ablation to form the pore 10 as an example, laser ablation can be performed on one side of the first pole piece 1 to form the pore 10 as shown in FIG. Fig. 9 The pore 10 is shown. When laser ablation is performed on one side, the pore 10 can be formed by burning through once, or by burning through twice. In addition, laser ablation can also be performed on both sides of the first pole piece 1.

[0151] Of course, in other implementations, the pore size of the pore 10 may also decrease in a step-like trend along the first direction.

[0152] Reference Fig.10 As shown, in some embodiments, along the first direction, the first pole piece 1 may include a first portion and a second portion, and the second portion is located on one side of the first portion along the first direction.

[0153] The first direction here can be specifically Fig.10 The up-down direction shown is, for example, the thickness direction of the first pole piece 1 .

[0154] Correspondingly, the pore 10 includes a first pore segment 102 and a second pore segment 103, which are arranged opposite to each other and are connected. Specifically, the first pore segment 102 penetrates the first part of the first pole piece 1 along the first direction, and the second pore segment 103 penetrates the second part of the first pole piece 1 along the first direction.

[0155] In the direction from the first pore segment 102 to the second pore segment 103 (for example Fig.10 In the direction from the second pore segment 103 to the first pore segment 102 (for example, Fig.10 In the direction from bottom to top in the figure, the pore diameter a of the second pore section 103 gradually decreases. The pore diameter a here is Fig.10 The pore size in the left and right direction along the middle. Fig.10 For example, an inverted trapezoidal aperture may be formed on the first portion of the first pole piece 1 , and a trapezoidal aperture may be formed on the second portion of the first pole piece 1 .

[0156] Such an arrangement can increase the expansion buffer space to a certain extent, so that the expansion of the second pole piece 2 can be further alleviated, thereby further preventing the pole piece from deforming or breaking; moreover, such an arrangement can further prevent powder loss during the process of making the pores 10, thereby further improving the structural strength of the first pole piece 1, and further ensuring the amount of the active material layer of the first pole piece 1, thereby ensuring the capacity and other performance of the battery to a certain extent; in addition, such an arrangement can also prevent the collapse of the first pole piece 1 to a certain extent when the first pole piece 1 is hot pressed; in addition, such an arrangement can also improve the wetting effect of the electrolyte to a certain extent, thereby improving the charging, discharging, and cycling performance of the battery.

[0157] For example, taking the formation of the pore 10 on the first pole piece 1 by laser ablation as an example, refer to Fig.10 As shown, for example, double-sided laser ablation may be used to form the first aperture segment 102 by laser ablation from the upper side of the first pole piece 1 , and to form the second aperture segment 103 by laser ablation from the lower side of the first pole piece 1 .

[0158] Of course, in other implementations, the pores 10 may be formed by single-sided laser ablation or mechanical punching.

[0159] Reference Fig.11 As shown, in some embodiments, at least one recessed portion 181 is further provided on the side of the first active material layer 12 away from the first current collector 11, and the recessed portion 181 is recessed toward the first current collector 11. Specifically, the recessed portion 181 can be formed by laser drilling or line punching on the first active material layer 12.

[0160] Exemplarily, there may be a plurality of recessed portions 181 , and the plurality of recessed portions 181 are arranged at intervals along the length direction of the first pole piece 1 , for example.

[0161] By providing the recessed portion 181, the expansion buffer space is further increased, thereby further reducing the risk of deformation and fracture of the pole piece, etc. Moreover, the presence of the recessed portion 181 can further increase the liquid storage capacity of the pole piece and the wettability of the electrolyte, so that lithium ions can diffuse rapidly in the electrolyte, further improving the dynamic performance and cycle performance of the battery.

[0162] Reference Fig.12 As shown, in some embodiments, the first active material layer 12 is provided with a plurality of recessed portions 181 and a plurality of raised portions 191 corresponding to the recessed portions 181 . The recessed portions 181 are recessed toward the first current collector 11 .

[0163] By providing a plurality of recessed portions 181, the expansion buffer space is further increased, thereby further reducing the risk of deformation and fracture of the pole piece, etc. Moreover, the presence of the recessed portions 181 can further increase the liquid storage capacity of the pole piece and the wettability of the electrolyte, so that lithium ions can diffuse rapidly in the electrolyte, further improving the dynamic performance and cycle performance of the battery.

[0164] Moreover, such a configuration allows the area between two adjacent protrusions 191 to form a buffer space, thereby further increasing the overall expansion buffer space, so that the expansion of the second pole piece 2 can be further effectively alleviated, further ensuring that the first pole piece 1 and the second pole piece 2 are not prone to deformation or fracture. Moreover, the liquid storage capacity and the wettability of the electrolyte can be further increased, thereby further improving the dynamic performance and cycle performance of the battery.

[0165] Exemplarily, specifically, it can be that along the first direction (specifically Fig.12 In the up and down direction, for example, the thickness direction of the first electrode sheet 1), the first electrode sheet 1 has a first side 18 and a second side 19 relative to each other, the recessed portion 181 is formed by the first current collector 11 and the first active material layer 12 being recessed toward the second side 19, and a protruding portion 191 protruding toward the direction away from the first side 18 is formed at a position of the second side 19 corresponding to the recessed portion 181.

[0166] Exemplarily, the recessed portion 181 can be formed by, for example, rolling the first side 18 of the first pole piece 1 with a roller having convex points on the surface (i.e., embossing the first pole piece 1). That is, the roller presses part of the first active material layer 12 and the first current collector 11 downward toward the second side 19, so that the part of the first active material layer 12 and the first current collector 11 protrude toward the second side 19, thereby forming a recessed portion 181 on the first side 18 and a convex portion 191 on the second side 19.

[0167] Compared with a solution in which the recess 181 is formed only on the first side 18 and the second side 19 remains unchanged (i.e., a hole is punched on the first side 18 to remove part of the first active material layer 12 to form the recess 181), this arrangement can avoid waste of material of the active material layer and capacity loss because the material at the protrusion 191 is formed by the protrusion of the material at the original recess 181.

[0168] In addition, since the protrusion 191 can be formed by setting the recess 181 on the first pole piece 1, that is, the compaction of a partial area of ​​the first pole piece 1 is relatively increased, thereby improving the adhesion and structural strength of the first active material layer 12 of the first pole piece 1, and to a certain extent increasing the peeling force between the first active material layer 12 and the first current collector 11, thereby improving the problem of active material shedding and large expansion of the first pole piece 1 during the cycle process, and improving the stability of the battery cell during cycling and storage.

[0169] Of course, the recessed portion 181 and the raised portion 191 may also be formed by other methods.

[0170] The concave portion 181 may be a pit, a groove, etc., and the convex portion 191 may be a convex hull. The cross-sectional shape of the concave portion 181 may be circular, elliptical, square, etc., and the cross-sectional shape of the convex portion 191 may also be circular, elliptical, square, etc.

[0171] Continue to refer to Fig.12 As shown, in some embodiments, the recessed portion 181 is spaced from the pore 10, that is, there is a distance between the recessed portion 181 and the pore 10. This can avoid, to a certain extent, the overlap of the recessed portion 181 and the pore 10, which may cause the first pole piece 1 to break prematurely during the manufacturing process or during the use of the battery cell.

[0172] In the third direction, the distance F between the recessed portion 181 and the pore 10 can satisfy: 0.1 mm ≤ F ≤ 5 mm. Fig.12 As shown, the third direction here can be specifically Fig.12 The left-right direction in the figure is, for example, the length direction of the first pole piece 1. The spacing F specifically refers to the distance between the center line of the recessed portion 181 and the center line of the pore 10.

[0173] Exemplarily, the spacing F may be, for example, 0.1 mm, 1 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, or 5 mm.

[0174] Of course, the positions of the recessed portion 181 and the pore 10 on the first pole piece 1 may also overlap. For example, taking the formation of the recessed portion 181 on the first pole piece 1 by the above-mentioned embossing method as an example, the recessed portion 181 and the raised portion 191 may be formed by embossing on the first pole piece 1 first, and then the pore 10 may be formed at the positions of the recessed portion 181 and the raised portion 191 by mechanical punching or laser ablation.

[0175] Reference Fig.13 and Fig.14 As shown, in some embodiments, both the first pole piece 1 and the second pole piece 2 are provided with pores 10 .

[0176] The structure, specific arrangement and implementation principle of the pores 10 on the second pole piece 2 may refer to the description of the pores 10 on the first pole piece 1 above, and will not be described in detail here.

[0177] When the pores 10 are provided on the second pole piece 2, the existence of the pores 10 can also better alleviate the expansion of the second pole piece 2 itself, reduce the expansion stress of the second pole piece 2, reduce the squeezing force between the first pole piece 1 and the second pole piece 2, and further prevent the second pole piece 2 and the first pole piece 1 from deformation and breakage.

[0178] For example, when the pores 10 are provided on the first pole piece 1, they can be provided by mechanical punching, for example. For another example, when the pores 10 are provided on the second pole piece 2, they can be provided by laser ablation or mechanical punching.

[0179] By providing the pores 10 on both the first pole piece 1 and the second pole piece 2, the expansion buffer space of the entire battery cell can be further increased, the expansion stress of the pole pieces can be further reduced, and the first pole piece 1 and the second pole piece 2 can be further prevented from being deformed or broken.

[0180] Further, in order to avoid the lithium precipitation phenomenon to a certain extent, continue to refer to Fig.13 As shown, in a feasible implementation, the pores 10 on the second pole piece 2 can be arranged corresponding to the pores 10 on the first pole piece 1, and the projection of the pores 10 on the second pole piece 2 on the first pole piece 1 is located within the area surrounded by the pores 10 on the first pole piece. That is, the area of ​​the pores 10 on the second pole piece 2 is smaller than the area of ​​the pores 10 on the first pole piece 1, so as to ensure that the first pole piece 1 at any position of the battery cell is covered by the second pole piece 2, so as to effectively accommodate the volume expansion of the second pole piece 2, reduce the expansion stress of the second pole piece 2, and the extrusion force between the first pole piece 1 and the second pole piece 2, and avoid the lithium precipitation phenomenon to a certain extent.

[0181] Reference Fig.14As shown, an insulating layer 5 is provided on the surface of the first pole piece 1 facing the second pole piece 2, and the insulating layer 5 is provided corresponding to the pores 10 on the first pole piece 1, and the projection of the pores 10 on the second pole piece 2 on the first pole piece 1 is located in the area covered by the insulating layer 5. That is, the area of ​​the pores 10 on the second pole piece 2 is smaller than the coverage area of ​​the insulating layer 5, so as to ensure that the first pole piece 1 at any position of the battery cell is covered by the second pole piece 2, so as to effectively accommodate the volume expansion of the second pole piece 2, reduce the expansion stress of the second pole piece 2, and the extrusion force between the first pole piece 1 and the second pole piece 2, and avoid the lithium deposition phenomenon to a certain extent.

[0182] Exemplarily, the insulating layer 5 may be, for example, insulating tape, which is pasted on the first pole piece 1 to cover a local area on the first pole piece 1. Of course, the insulating layer 5 may also be other insulating materials besides insulating tape.

[0183] This embodiment also provides a battery, which may be a lithium-ion battery, for example. The battery may be used as a power source or energy storage unit for electronic devices, and the electronic devices may be, but are not limited to, mobile devices (mobile phones, laptops, tablet computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, electric bicycles, etc.).

[0184] The battery specifically comprises a shell and a battery cell, wherein the battery cell is located inside the shell.

[0185] The structure and implementation principle of this battery cell are the same as those of the battery cell 100 provided in the above embodiment, and can bring the same or similar technical effects, which will not be described one by one here, and the details can be referred to the description of the above embodiment.

[0186] In this article, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, or it can be indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In addition, the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0187] In this article, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0188] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery cell, characterized in that: It includes a first pole piece and a second pole piece, the first pole piece and the second pole piece have different polarities, and the first pole piece and the second pole piece are stacked and wound to form a winding core; The winding core comprises a straight area and a corner area, wherein the corner area is located at two opposite sides of the straight area; The first pole piece includes a first current collector and a first active material layer disposed on at least one side of the first current collector; The second pole piece includes a second current collector and a second active material layer disposed on at least one side of the second current collector, wherein the second active material layer includes a silicon-carbon composite material and / or a silicon-oxygen composite material; A pore is provided at least at a position of the first pole piece corresponding to the corner region, and the pore is provided through the first current collector and the first active material layer along the first direction.

2. The battery cell according to claim 1, characterized in that: The total number of winding folds of the winding core is N, where N is a positive integer, and at least part of the pores are located in the N-1th fold and / or the Nth fold region of the first pole piece.

3. The battery cell according to claim 1, characterized in that: In the direction from the winding head end of the winding core to the winding tail end of the winding core, the ratio of the length L1 of the pore located on the corner area to the length L of the corresponding corner area satisfies: 1%≤L1 / L≤100%.

4. The battery cell according to claim 1, characterized in that: In the direction from the winding head end of the winding core to the winding tail end of the winding core, the pores located on the corner area extend to the straight area.

5. The battery cell according to claim 4, characterized in that: The length M of the pore extending to the straight area satisfies: M≤5mm.

6. The battery cell according to claim 1, characterized in that: The first pole piece is provided with the pore at a position corresponding to the straight area; the first pole piece is provided with a pole ear, and the pole ear is located in the straight area; At least a portion of the pores located on the flat region at least partially overlaps with a projection of the position of the electrode tab in the thickness direction of the battery cell.

7. The battery cell according to claim 1, characterized in that: In the direction from the winding head end of the winding core to the winding tail end of the winding core, the first pole piece includes a double-sided area and a single-sided area, the single-sided area is an area where the first active material layer is provided on one side of the first current collector, and the double-sided area is an area where the first active material layer is provided on both sides of the first current collector; The double-sided area is provided with the pores, and / or the single-sided area is provided with the pores.

8. The battery cell according to claim 1, characterized in that: In the second direction, the ratio of the width d of the pore to the width D of the first pole piece satisfies: 5%≤d / D≤95%; And / or, the pore extends to an edge of the first pole piece along the second direction; And / or, in the direction from the inner winding circle to the outer winding circle of the winding core, at least two adjacent circles of the electrode sheets are provided with the pores, and at least the projections of the pores on the two adjacent circles in the thickness direction of the battery core at least partially overlap; And / or, the pores include a plurality of buffer holes penetrating the first pole piece along the first direction, and among all the buffer holes, at least a portion of the buffer holes are arranged at intervals along the second direction.

9. The battery cell according to claim 1, characterized in that: In the direction from the inner winding circle to the outer winding circle of the winding core, the width of the pores on the outermost winding circle along the second direction is greater than the width of the pores on the innermost winding circle along the second direction; and / or, in the direction from the winding inner circle to the winding outer circle of the winding core, the length of the pores on the outermost winding circle along the third direction is greater than the length of the pores on the innermost winding circle along the third direction; And / or, there are a plurality of pores, and the plurality of pores are arranged at intervals along a direction from a winding head end of the first pole piece to a winding tail end of the first pole piece; In the direction from the winding inner circle to the winding outer circle of the winding core, the number of pores located on the winding outermost circle is greater than the number of pores located on the winding innermost circle.

10. The battery cell according to claim 1, characterized in that: Along the first direction, the apertures at two ends of the aperture are different.

11. The battery cell according to claim 10, characterized in that: Along the first direction, the pores have pore diameters that gradually decrease.

12. The battery cell according to claim 1, characterized in that: The first pole piece includes a first portion and a second portion, wherein the second portion is located on one side of the first portion along the first direction; The pore comprises a first pore segment and a second pore segment which are arranged opposite to each other and are connected, the first pore segment penetrates the first part along the first direction, and the second pore segment penetrates the second part along the first direction; In the direction from the first pore segment to the second pore segment, the pore diameter of the first pore segment gradually decreases; in the direction from the second pore segment to the first pore segment, the pore diameter of the second pore segment gradually decreases.

13. The battery cell according to any one of claims 1 to 12, characterized in that: The first active material layer is provided with a plurality of recessed portions and a plurality of raised portions corresponding to the recessed portions, and the recessed portions are recessed toward the first current collector.

14. The battery cell according to claim 13, characterized in that: The recessed portion is spaced apart from the pore; and / or, along the third direction, a distance F between the recessed portion and the pore satisfies: 0.1 mm ≤ F ≤ 5 mm; And / or, along the first direction, the first pole piece has a first side and a second side relative to each other, the recessed portion is formed by the first current collector and the first active material layer being recessed toward the second side, and the raised portion is formed at a position on the second side corresponding to the recessed portion and protruding toward a direction away from the first side.

15. The battery cell according to any one of claims 1 to 12, characterized in that: The pores are disposed on both the first pole piece and the second pole piece.

16. The battery cell according to claim 15, characterized in that: The pores on the second pole piece are arranged corresponding to the pores on the first pole piece, and the projection of the pores on the second pole piece on the first pole piece is located in the area surrounded by the pores on the first pole piece.

17. The battery cell according to claim 15, characterized in that: An insulating layer is provided on a surface of the first pole piece facing the second pole piece, the insulating layer is provided corresponding to the pores on the first pole piece, and a projection of the pores on the second pole piece on the first pole piece is located within an area covered by the insulating layer.

18. A battery, characterized in that: It comprises a shell and a battery cell as claimed in any one of claims 1 to 17; the battery cell is located in the shell.

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