Battery pole piece and battery roll core

Abstract

The invention discloses a battery pole piece and a battery roll core. The battery pole piece comprises a current collector; the active coating comprises a first coating section and a second coating section which are arranged on the current collector, and the first coating section can be positioned on the outer side of the second coating section when the battery pole piece is wound; and the first groove is formed in the first coating section. In the application, the first groove is formed in the first coating section, and different areas of the battery pole piece are differentially arranged in combination with actual application, so that the first groove is prevented from deforming and collapsing, and the first groove is ensured to improve the flowing speed of an electrolyte, the infiltration effect on the battery pole piece and the liquid storage capacity of the battery pole piece; the contact reaction area of the active coating of the battery pole piece is increased, and extrusion caused by expansion of the battery pole piece is relieved, so that the cycle and fast charge performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery pole piece and a battery winding core. Background Art

[0002] With the development of the new energy era, the rapid development of lithium batteries has also followed. In recent years, lithium batteries have been widely used in electronic devices such as mobile phones and tablets, and hybrid vehicles and new energy electric vehicles have gradually become popular in people's lives, which has put forward higher requirements for the performance of lithium batteries. Therefore, high-performance lithium-ion secondary batteries with large capacity, high energy density and fast charging and discharging have received widespread attention. At the same time, the safety of lithium batteries has also attracted much attention. During the long-term use of the battery, the battery pole piece will expand, causing extrusion, causing the electrolyte to gather on both sides of the battery pole piece, causing lithium precipitation on the edges of both sides of the battery pole piece, and the electrolyte reflux is blocked, which will cause the middle part of the battery pole piece to burn black due to insufficient electrolyte, which will have a negative impact on the battery's cycle and fast charging performance.

[0003] Although there is currently a prior art that proposes to provide a groove structure on the surface of the battery pole piece to improve the wettability of the electrolyte to the pole piece and the liquid storage capacity of the pole piece, in actual applications, after the battery pole piece is wound to form a battery core, the stress in the area close to the center of the battery core is significantly greater than the stress in the area far from the center of the battery core, which makes the groove structure prone to uneven force and causes deformation and collapse of the internal groove structure. It is impossible to effectively improve the battery's cycle and fast charging performance in actual applications. Summary of the invention

[0004] The present application provides a battery pole piece, which realizes differentiated settings of different areas of the battery pole piece in combination with practical applications, effectively preventing the first groove from deforming and collapsing due to uneven force, thereby effectively improving the battery's cycle and fast charging performance in practical applications.

[0005] A battery pole piece according to an embodiment of the present application includes: a current collector; an active coating, the active coating including a first coating segment and a second coating segment arranged on the current collector, and the first coating segment can be located on the outside of the second coating segment when the battery pole piece is wound; a first groove, the first groove is arranged on the first coating segment.

[0006] In the present battery pole piece, the first coating section is wound and arranged on the outer side of the coating of the second coating section so that the stress on the first coating section is smaller than that on the second coating section, and the first groove is arranged on the first coating section, so that different areas of the battery pole piece can be differentiated in combination with actual applications, and the first groove can be effectively prevented from being deformed and collapsed due to uneven force, ensuring that the first groove can increase the flow rate of the electrolyte, the wetting effect of the electrolyte on the battery pole piece and the liquid storage capacity of the battery pole piece in actual applications, increase the contact reaction area of ​​the active coating of the battery pole piece, alleviate the extrusion caused by the expansion of the battery pole piece, and thus improve the battery cycle and fast charging performance.

[0007] According to some embodiments of the present application, it also includes a second groove extending along the mechanical stretching direction, and the second groove is arranged on the second coating section.

[0008] According to some embodiments of the present application, the current collector has two side surfaces arranged opposite to each other, and the second coating section includes a second primer layer and a second surface layer, wherein: the second primer layer is arranged on at least one of the side surfaces, the second surface layer is stacked on the second primer layer, and the second groove is arranged on the second surface layer.

[0009] According to some embodiments of the present application, the first coating section includes a first base coating and a first surface coating, the first base coating is disposed on at least one of the side surfaces, the first surface coating is stacked on the first base coating, and the first groove is disposed on the first surface coating.

[0010] According to some embodiments of the present application, the arrangement ratio of the second grooves on any side of the current collector is R1; the expression of R1 is: Wherein a1 is the length of the second groove, b1 is the width of the second groove, d1 is the depth of the second groove, n1 is the number of the second grooves on either side of the current collector, M is the weight of the active coating on either side of the current collector, X is the length of the second coating section, and S is the length of the current collector.

[0011] According to some embodiments of the present application, 0≤R1≤10%.

[0012] According to some embodiments of the present application, the arrangement ratio of the first grooves on any side of the current collector is R2; the expression of R2 is: Wherein a2 is the length of the first groove, b2 is the width of the first groove, d2 is the depth of the first groove, and n2 is the number of the first grooves on any side of the current collector.

[0013] Based on the same inventive concept, the present application also proposes a battery roll core, comprising: a diaphragm and two battery pole sheets as described above, wherein the active coating in any one of the battery pole sheets is composed of a first active substance, and the active coating in the other of the battery pole sheets is composed of a second active substance; the diaphragm is arranged between the two battery pole sheets to isolate the two battery pole sheets.

[0014] According to some embodiments of the present application, the expression for the length of the second coating section is: Wherein x is the thickness of any one of the battery pole sheets, y is the thickness of another of the battery pole sheets, z is the thickness of the diaphragm, r is the diameter of the winding needle, and m is the number of winding turns of the second coating section.

[0015] According to some embodiments of the present application, 1≤m≤50.

[0016] In summary, the battery electrode provided by this application has the following technical effects:

[0017] The first coating section is wound and arranged on the outer side of the second coating section so that the stress on the first coating section is smaller than that on the second coating section, and the first groove is arranged on the first coating section, so that different areas of the battery pole piece can be differentiated in combination with actual applications, and the first groove can be effectively prevented from being deformed and collapsed due to uneven force, ensuring that the first groove can increase the flow rate of the electrolyte, the wetting effect of the electrolyte on the battery pole piece and the liquid storage capacity of the battery pole piece in actual applications, increase the contact reaction area of ​​the active coating of the battery pole piece, alleviate the extrusion caused by the expansion of the battery pole piece, and thus improve the cycle and fast charging performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the planar structure of a battery electrode of an embodiment of the present application;

[0019] Figure 2 This is a schematic diagram of the structure of a battery electrode of an embodiment of the present application;

[0020] Figure 3 This is a schematic structural diagram of a battery pole piece in the first embodiment of the present application;

[0021] Figure 4 This is a schematic structural diagram of a second form of a battery electrode according to an embodiment of the present application;

[0022] Figure 5 This is a schematic structural diagram of the third form of the battery pole piece of an embodiment of the present application;

[0023] Figure 6 This is a schematic structural diagram of a fourth form of a battery electrode according to an embodiment of the present application;

[0024] Figure 7 This is a schematic structural diagram of a fifth form of a battery pole piece according to an embodiment of the present application;

[0025] Figure 8 This is a structural schematic diagram of a sixth form of a battery pole piece according to an embodiment of the present application;

[0026] Fig. 9 This is a structural schematic diagram of the seventh form of the battery pole piece of an embodiment of the present application;

[0027] Fig.10 This is a structural schematic diagram of the eighth form of the battery pole piece of an embodiment of the present application.

[0028] The meanings of the reference numerals are as follows:

[0029] 1. Current collector; 2. Active coating; 21. First coating section; 211. First base coating; 212. First surface coating; 22. Second coating section, 221. Second base coating; 222. Second surface coating; 3. First groove; 4. Second groove. DETAILED DESCRIPTION

[0030] For better understanding and implementation, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0031] In the description of the present application, it should be noted that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do 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.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0033] See also Figure 1-Figure 10The present application discloses a battery pole piece, which includes a current collector 1, an active coating 2 and a first groove 3. In some embodiments, the active coating 2 includes a first coating segment 21 and a second coating segment 22 arranged on the current collector 1, and the first coating segment 21 can be located on the outside of the coating of the second coating segment 22 when the battery pole piece is wound; the first groove 3 is arranged on the first coating segment 21. In this way, the first coating section 21 is wound and arranged on the outside of the second coating section 22 so that the stress on the first coating section 21 is smaller than that on the second coating section 22, and the first groove 3 is arranged on the first coating section 21, so as to realize differentiated arrangement of different areas of the battery pole piece in combination with actual application, effectively prevent the first groove 3 from deformation and collapse due to uneven force, and ensure that the first groove 3 can improve the flow rate of the electrolyte, the wetting effect of the electrolyte on the battery pole piece and the liquid storage capacity of the battery pole piece in actual application, increase the contact reaction area of ​​the active coating 2 of the battery pole piece, alleviate the extrusion caused by the expansion of the battery pole piece, thereby improving the cycle and fast charging performance of the battery.

[0034] See also Figure 1 , Figure 3 , Figure 4 , Figure 5 and Figure 6In some embodiments, with the long-term use of the battery, the area where the second coating section 22 on the battery pole piece is located may still face the problem of expansion and extrusion, causing the electrolyte to gather on both sides of the second coating section 22, etc., which affects the battery's cycle and fast charging performance. Preferably, it also includes a second groove 4 extending along the machine direction (i.e., MD direction), and the second groove 4 is arranged on the second coating section 22. In this way, by arranging the second groove 4 on the second coating section 22 with greater stress, and utilizing the characteristic that the second groove 4 is extended along the MD direction, the second groove 4 can provide additional space to facilitate the relief of the expansion effect of the area where the second coating section 22 is located, avoiding the deformation and collapse of the second groove 4, ensuring that the second groove 4 can increase the flow rate of the electrolyte, the infiltration effect of the electrolyte on the area where the second coating section 22 is located, and the liquid storage capacity of the area where the second coating section 22 is located, and increase the contact reaction area of ​​the active coating 2 in the area where the second coating section 22 is located, thereby improving the battery's cycle and fast charging performance. In this embodiment, by arranging the first groove 3 on the first coating section 21 and arranging the second groove 4 on the second coating section 22, so that the first groove 3 and the second groove 4 are respectively located at different positions, the first groove 3 and the second groove 4 are respectively adapted to different stress conditions in different regions, thereby avoiding deformation and collapse of the groove structure. In this way, the battery pole piece can utilize the corresponding groove structure in different regions to increase the flow rate of the electrolyte, the wetting effect of the electrolyte on the battery pole piece, and the liquid storage capacity of the battery pole piece, increase the contact reaction area of ​​the active coating 2, alleviate the extrusion caused by the expansion of the region, and thus improve the cycle and fast charging performance of the battery.

[0035] See also Figure 2 In some embodiments, the current collector 1 has two opposite sides, and the second coating section 22 includes a second primer layer 221 and a second surface layer 222, wherein: the second primer layer 221 is disposed on at least one of the sides, the second surface layer 222 is stacked on the second primer layer 221, and the second groove 4 is disposed on the second surface layer 222. In this way, the second primer layer 221 and the second surface layer 222 are stacked on at least one of the sides of the current collector 1, so that the second groove 4 is disposed on at least one of the sides of the current collector 1. Optionally, when the second primer layer 221 and the second surface layer 222 are stacked on any of the sides of the current collector 1, the other side is coated with a corresponding active material; optionally, when the second primer layer 221 and the second surface layer 222 are stacked on both sides of the current collector 1, the second groove 4 is disposed on both sides of the current collector 1.

[0036] Optionally, the number of the second grooves 4 may be one or more; optionally, when the number of the second grooves 4 is multiple, the sizes (length, width, depth) of the second grooves 4 may be different from each other; optionally, the second grooves 4 are formed by laser burning the second surface coating 222. Specifically, at the three nodes after the pole piece is coated, after cold pressing or before winding, the active material on the second surface coating 222 is burned by laser to form the second groove 4 on the second surface coating 222. At the same time, the active material after burning can be adsorbed and removed by a dust collector, without the need to add an additional process for cleaning the battery pole piece.

[0037] Furthermore, after the second groove 4 is set on the second surface coating 222, the active material on the current collector 1 will inevitably be lost. When the active material on the current collector 1 is lost too much, it will have a great impact on the rated capacity or charging NP ratio of the battery, resulting in adverse phenomena such as low capacity or lithium precipitation, which will seriously affect the cycle performance and storage performance of the battery. Preferably, the surface density of the second base coating 221 is greater than the surface density of the second surface coating 222, the compaction density of the second base coating 221 is greater than the compaction density of the second surface coating 222, and the thickness of the second base coating 221 is greater than the thickness of the second surface coating 222. In this way, the loss of active materials caused by setting the second groove 4 on the second surface coating 222 can be effectively reduced, and the influence of setting the second groove 4 in the second surface coating 222 on the cycle performance and storage performance of the battery can be effectively reduced. At the same time, the battery capacity is positively correlated with the compaction density, that is, the greater the compaction density, the greater the battery capacity. Therefore, by making the compaction density of the second base coating 221 greater than the compaction density of the second surface coating 222, it is prevented that after the second groove 4 is set in the second surface coating 222, the compaction density of the active material on the current collector 1 will change significantly, thereby effectively ensuring the battery capacity.

[0038] In some embodiments, since the area where the second coating section 22 is located needs to withstand greater stress, the second coating section 22 may not be provided with the second groove 4. Figure 2 , Figure 7 , Figure 8 , Fig. 9 and Fig.10, to prevent the collapse of the groove structure inside the battery pole piece, but with the long-term use of the battery, the area where the second coating section 22 is located may still face expansion and extrusion, causing the electrolyte to gather on both sides of the pole piece and other problems that affect the battery's circulation and fast charging performance. Therefore, it is necessary to set the size of the second groove 4 on the second coating section 22 to a specific size, and the extension direction of the second groove 4 can only be the MD direction, so as to avoid the problem of uneven force during use caused by the large size and depth of the second groove 4, thereby preventing the collapse of the groove structure inside the battery pole piece; preferably, the setting ratio of the second groove 4 on any side of the current collector 1 is R1, and the expression of R1 is: See Figure 1 , a1 is the length of the second groove 4, b1 is the width of the second groove 4, d1 is the depth of the second groove 4, n1 is the number of the second grooves 4 on any side of the current collector 1, M is the weight of the active coating 2 on any side of the current collector 1, X is the length of the second coating section 22, and S is the length of the current collector 1.

[0039] Specifically, the length a1 of the second groove 4 is less than or equal to the length X of the second coating section 22, wherein the MD direction is parallel to the length direction of the second coating section 22, so the length a1 of the second groove 4 extending along the MD direction is less than or equal to the length X of the second coating section 22, which also means that the second groove 4 can pass through the second coating section 22, but cannot touch the pole ear. If the pole ear is damaged, the tape is likely to break during subsequent winding. Optionally, limited by the existing processing technology, the length a1 of the second groove 4 is ≥ 0.005 mm, that is, the current minimum value of the length a1 of the second groove 4 is 0.005 mm, but with the development of processing technology and corresponding processing equipment, the minimum value a1 of the length of the second groove 4 is 1min Can be further reduced to 0.005>a 1min ≥0, so the current range of the length a1 of the second groove 4 is: X≥a1≥0.005mm. Optionally, in order to avoid the problem of uneven force during use caused by the size of the second groove 4 being too large, the width b1 of the second groove 4 needs to be in the range of: b1≤0.2mm to prevent the second groove 4 from collapsing. Optionally, limited by the existing processing technology, the width b1 of the second groove 4 is ≥0.005mm, that is, the current minimum value of the width b1 of the second groove 4 is 0.005mm, but with the development of processing technology and corresponding processing equipment, the minimum value b1 of the width of the second groove 4 1min Can be further reduced to 0.005>b 1min≥0, so currently the width b1 of the second groove 4 is in the range of: 0.2mm≥b1≥0.005mm. Optionally, the weight M of the active coating 2 on any side of the current collector 1 is the sum of the weights of the active materials of the first coating section 21 and the second coating section 22 located on any side of the current collector 1.

[0040] In some embodiments, since the area where the second coating section 22 is located needs to withstand greater stress, the second coating section 22 may not be provided with the second groove 4, so the minimum value of the setting ratio R1 of the second groove 4 on any side of the current collector 1 is 0, that is, 0≤R1; further, when the number of the second grooves 4 exceeds the preset range, the setting ratio R1 of the second grooves 4 on any side of the current collector 1 will increase, causing the second grooves 4 on any side of the current collector 1 to be prone to uneven force during use, so R1≤10% to prevent The number of the second grooves 4 exceeds the preset range, so the setting ratio R1 of the second grooves 4 on any side of the current collector 1 is in the range of: 0≤R1≤10%, thereby avoiding deformation and collapse of the second grooves 4, ensuring that the second grooves 4 can increase the flow rate of the electrolyte, the wetting effect of the electrolyte on the area where the second coating section 22 is located, and the liquid storage capacity of the area where the second coating section 22 is located, increase the contact reaction area of ​​the active coating 2 in the area where the second coating section 22 is located, alleviate the extrusion caused by the expansion of the area where the second coating section 22 is located, thereby improving the battery's cycle and fast charging performance.

[0041] See also Figure 2 In some embodiments, the first coating section 21 includes a first primer layer 211 and a first surface layer 212, wherein the first primer layer 211 is disposed on at least one of the side surfaces, the first surface layer 212 is stacked on the first primer layer 211, and the first groove 3 is disposed on the first surface layer 212. In this way, the first primer layer 211 and the first surface layer 212 are stacked on at least one of the side surfaces of the current collector 1, so that the first groove 3 is disposed on at least one side surface of the current collector 1. Preferably, the stacked structure formed by the first base coating 211 and the first surface coating 212 and the stacked structure formed by the second base coating 221 and the second surface coating 222 are arranged in sequence on the current collector 1; optionally, when the first base coating 211 and the first surface coating 212 are stacked on any one of the side surfaces of the current collector 1, the other side surface is coated with a corresponding active material; optionally, when the first base coating 211 and the first surface coating 212 are stacked on both side surfaces of the current collector 1, the first groove 3 is provided on both side surfaces of the current collector 1.

[0042] Optionally, the number of the first grooves 3 may be one or more. Optionally, when the number of the first grooves 3 is multiple, the sizes and extension directions of the first grooves 3 may be different from each other. Optionally, the first grooves 3 are formed by laser burning the first surface coating 212. Specifically, at the three nodes after the pole piece is coated, after cold pressing or before winding, the active material on the first surface coating 212 is burned by laser to form the first groove 3 on the first surface coating 212. At the same time, the active material after burning can be adsorbed and removed by a dust collector, without the need to add an additional process for cleaning the battery pole piece.

[0043] Optionally, the first groove 3 may be extended along the TD direction (Transverse Direction, i.e., the transverse direction, which is a direction perpendicular to the MD direction) or the MD direction; optionally, the cross-sectional shape of the first groove 3 is not unique, and optionally, the cross-sectional shape of the first groove 3 may be one of a rectangle, a trapezoid, a cone and an arc; optionally, the first groove 3 is evenly distributed on the first surface coating 212; optionally, the first groove 3 is distributed in a local area of ​​the first surface coating 212; optionally, the first grooves 3 on the same first surface coating 212 are distributed at intervals, that is, adjacent first grooves 3 are independent and separated from each other, or, the first grooves 3 are cross-distributed, and further, the first surface coating 212 has both cross-distributed first grooves 3 and spaced-distributed first grooves 3, that is, the distribution of the first grooves 3 is one or more of cross-distribution and spaced-distribution.

[0044] Optionally, the form of the battery electrode is as follows: Figure 3 As shown, the second surface coating layer 222 is provided with the second groove 4 extending along the MD direction, and the first surface coating layer 212 is provided with the first groove 3 extending along the TD direction, and the first groove 3 and the second groove 4 are used to increase the storage capacity of the battery electrode for the electrolyte, and increase the reaction area of ​​the active material on the surface of the battery electrode, thereby improving the reaction activity;

[0045] Optionally, the form of the battery electrode is as follows: Figure 4 As shown, the second surface coating 222 is provided with the second groove 4 extending along the MD direction, and the first groove 3 on the first surface coating 212 is inclined in the TD direction, thereby greatly increasing the reaction area of ​​the active material on the surface of the battery pole piece and the storage capacity of the electrolyte, and the first groove 3 can serve as a gas discharge channel, effectively reducing the pressure inside the battery, improving the safety performance of the battery, and alleviating the occurrence of side reactions between the battery pole pieces;

[0046] Optionally, the form of the battery electrode is as follows: Figure 5 As shown, the second surface coating 222 is provided with the second groove 4 extending along the MD direction, and the first surface coating 212 is provided with the first groove 3 extending along the MD direction. The first groove 3 and the second groove 4 are used to increase the reaction area of ​​the active material on the surface of the battery pole piece, improve the reaction activity, and provide additional space to alleviate the expansion of the battery pole piece, prevent the first groove 3 and / or the second groove 4 from collapsing and deforming, and improve the phenomenon of uneven current in the middle and on both sides of the battery pole piece;

[0047] Optionally, the form of the battery electrode is as follows Figure 6 As shown, the second surface coating 222 is provided with the second groove 4 extending along the MD direction, and the first surface coating 212 is provided with at least two first grooves 3, any one of the first grooves 3 is extended along the MD direction, and the other first groove 3 is extended along the TD direction, and there is an intersection point at the first grooves 3 of two different extension directions, so as to increase the reaction area of ​​the active material, improve the reaction activity and the storage capacity of the electrolyte, and can alleviate the expansion effect of the battery pole piece, prevent the first groove 3 and / or the second groove 4 from collapsing and deforming, and improve the phenomenon of uneven current in the middle and on both sides of the battery pole piece;

[0048] Optionally, the battery pole piece may be in the form of Figure 7 As shown, the second surface coating layer 222 does not have the second groove 4, and the first surface coating layer 212 is provided with the first groove 3 extending along the TD direction, and the first groove 3 is used to increase the storage capacity of the battery electrode for the electrolyte, and increase the reaction area of ​​the active material on the surface of the battery electrode, thereby improving the reaction activity;

[0049] Optionally, the battery pole piece may be in the form of Figure 8 As shown, there is no second groove 4 on the second surface coating 222, and the first groove 3 on the first surface coating 212 is inclined in the TD direction, thereby greatly increasing the reaction area of ​​the active material on the surface of the battery pole piece and the storage capacity of the electrolyte, and the first groove 3 can serve as a gas discharge channel, effectively reducing the pressure inside the battery, improving the safety performance of the battery, and alleviating the occurrence of side reactions between the battery pole pieces;

[0050] Optionally, the battery pole piece may be in the form of Fig. 9As shown, the second surface coating 222 does not have the second groove 4, and the first surface coating 212 is provided with the first groove 3 extending along the MD direction, so that the first groove 3 increases the reaction area of ​​the active material on the surface of the battery pole piece, improves the reaction activity, and can provide additional space to ease the expansion of the pole piece, prevent the first groove 3 from collapsing and deforming, and improve the phenomenon of uneven current in the middle and on both sides of the battery pole piece;

[0051] Optionally, the battery pole piece may be in the form of Fig.10 As shown, there is no second groove 4 on the second surface coating 222, and at least two first grooves 3 are provided on the first surface coating 212, any one of the first grooves 3 is extended along the MD direction, and the other first groove 3 is extended along the TD direction, and there is an intersection point at which the first grooves 3 in two different extension directions are connected, thereby increasing the reaction area of ​​the active material, improving the reaction activity and the electrolyte storage capacity, and relieving the expansion effect of the battery pole piece, preventing the first groove 3 from collapsing and deforming, and improving the phenomenon of uneven current in the middle and on both sides of the battery pole piece;

[0052] Furthermore, after the first groove 3 is set on the first surface coating layer 212, the active material on the current collector 1 will inevitably be lost. When the active material on the current collector 1 is lost too much, it will have a great impact on the rated capacity or charging NP ratio of the battery, resulting in adverse phenomena such as low capacity or lithium precipitation, which will seriously affect the cycle performance and storage performance of the battery. Preferably, the surface density of the first base coating 211 is greater than the surface density of the first surface coating 212, the compaction density of the first base coating 211 is greater than the compaction density of the first surface coating 212, and the thickness of the first base coating 211 is greater than the thickness of the first surface coating 212. In this way, the loss of active materials caused by setting the first groove 3 on the first surface coating 212 can be effectively reduced, and the influence of setting the first groove 3 in the first surface coating 212 on the cycle performance and storage performance of the battery can be effectively reduced. At the same time, the battery capacity is positively correlated with the compaction density, that is, the larger the compaction density, the larger the battery capacity. Therefore, by making the compaction density of the first base coating 211 greater than the compaction density of the first surface coating 212, it is prevented that after the first groove 3 is set in the first surface coating 212, the compaction density of the active material on the current collector 1 will change significantly, thereby effectively ensuring the battery capacity.

[0053] In some embodiments, the arrangement ratio of the first grooves 3 on any side of the current collector 1 is R2, and the expression of R2 is: See Figure 1, a2 is the length of the first groove 3, b2 is the width of the first groove 3, d2 is the depth of the first groove 3, and n2 is the number of the first grooves 3 on any side of the current collector 1. Optionally, the length direction of the first coating section 21 is parallel to the MD direction, so the length of the first coating section 21 is (SX), wherein the length X of the second coating section 22 can be set by the user according to the actual situation; Optionally, the length a2 of the first groove 3 is less than or equal to the length (SX) of the first coating section 21, which also means that the first groove 3 can pass through the first coating section 21, but cannot touch the pole ear. If the pole ear is damaged, the tape is likely to break in the subsequent winding. Optionally, limited by the existing processing technology, the length a2 of the first groove 3 is ≥ 0.005 mm, that is, the current minimum value of the length a2 of the first groove 3 is 0.005 mm, but with the development of processing technology and corresponding processing equipment, the minimum value a of the length of the first groove 3 is 2min Can be further reduced to 0.005>a 2min ≥0, so the current range of the length a2 of the first groove 3 is: (SX) ≥ a1 ≥ 0.005 mm. Similarly, the width b2 of the first groove 3 is less than or equal to the width L of the first coating section 21, and limited by the existing processing technology, the width b2 of the first groove 3 is ≥ 0.005 mm, but with the development of processing technology and corresponding processing equipment, the minimum value b2 of the width of the first groove 3 is 2min Can be further reduced to 0.005>b 2min ≥0, so currently the range of the width b2 of the first groove 3 is: L≥b1≥0.005mm.

[0054] Furthermore, based on the existing process, after the first groove 3 is set on the first surface coating 212, the active material on the current collector 1 will inevitably be lost, and when the active material on the current collector 1 is lost too much, it will have a greater impact on the rated capacity of the battery or the charging NP ratio, resulting in undesirable phenomena such as low capacity or lithium precipitation, which seriously affects the cycle performance and storage performance of the battery. Preferably, 0.01%≤R2≤20% is used to avoid excessive loss of active materials on the current collector 1 after the first groove 3 is set on the first surface coating 212, and at the same time ensure that the first groove 3 can increase the flow rate of the electrolyte, the wetting effect of the electrolyte on the area where the first coating section 21 is located, and the liquid storage capacity of the area where the first coating section 21 is located, increase the contact reaction area of ​​the active coating 2 in the area where the first coating section 21 is located, and alleviate the extrusion caused by the expansion of the area where the first coating section 21 is located, thereby improving the cycle and fast charging performance of the battery.

[0055] In some embodiments, a battery roll core comprises: a diaphragm and two battery pole sheets as described above, wherein the active coating 2 in any one of the battery pole sheets is composed of a first active substance, and the active coating 2 in the other of the battery pole sheets is composed of a second active substance; the diaphragm is arranged between the two battery pole sheets to isolate the two battery pole sheets. Optionally, the first active substance is a positive electrode active material, wherein the positive electrode active material is any one or more of lithium ferrous phosphate, ternary material nickel cobalt manganese, lithium manganate, lithium cobalt oxide, nickel cobalt aluminum oxide, etc.; the optional second active substance is a negative electrode active material, wherein the negative electrode active material is any one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon, etc.; in this way, the battery electrode with the first active substance is a positive electrode electrode, and the battery electrode with the second active substance is a negative electrode electrode. Optionally, two of the battery electrodes are stacked with the diaphragm, and the diaphragm is arranged between the two battery electrodes to isolate the two battery electrodes, and then the structure composed of the two battery electrodes and the diaphragm is wound to form a battery roll core.

[0056] In some embodiments, the structure composed of two battery pole sheets and the diaphragm is wound to form a battery core, and the first coating section 21 is wound outside the second coating section 22, so that the stress borne by the area where the first coating section 21 is located is less than the stress borne by the area where the second coating section 22 is located. Preferably, the length of the second coating section 22 is expressed as: Wherein x is the thickness of any one of the battery pole sheets, y is the thickness of another of the battery pole sheets, z is the thickness of the diaphragm, r is the diameter of the winding needle, and m is the number of winding turns of the second coating section 22 . Optionally, since the winding needle includes an inner needle and an outer needle, the inner needle clamps the starting end of the second coating section 22, and the outer needle is opened to provide space for the molding of the battery electrode and the diaphragm. Optionally, when the battery electrode is wound, the inner needle clamps the starting end of the second coating section 22 and rotates, driving the second coating section 22 to wind at least one inner circle, and since the starting end of the first coating section 21 is connected to the end of the second coating section 22, the inner needle can pull the first coating section 21 through the second coating section 22 to be wound on the outer circumference of the inner circle. Therefore, when calculating the length X of the second coating section 22, the influence of the winding needle diameter r needs to be considered. Optionally, the number of winding turns of the second coating section 22 can be determined according to factors such as battery specifications, capacity requirements, performance stability, manufacturing process and equipment. Preferably, the number of winding turns of the second coating section 22 is in the range of 1≤m≤50, thereby effectively limiting the length of the second coating section 22 in the battery core, realizing differentiated settings for different areas of the battery core in combination with actual applications, effectively avoiding deformation and collapse of the groove structure, and thereby driving the battery core to utilize the first groove 3 or the second groove 4 in different areas to increase the flow rate of the electrolyte, the wetting effect of the electrolyte on the battery core, and the liquid storage capacity of the battery electrode, thereby increasing the contact reaction area of ​​the active coating 2, and alleviating the extrusion caused by the expansion of the battery core, thereby improving the battery's cycle and fast charging performance.

[0057] The technical means disclosed in the present application are not limited to the technical means disclosed in the above-mentioned implementation methods, but also include technical solutions composed of any combination of the above technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of this application, and these improvements and modifications are also regarded as the protection scope of this application.

Claims

1. A battery pole piece, characterized in that: include: current collector(1); An active coating (2), the active coating (2) comprising a first coating section (21) and a second coating section (22) arranged on the current collector (1), and the first coating section (21) can be located outside the second coating section (22) when the battery electrode sheet is wound; A first groove (3), wherein the first groove (3) is arranged on the first coating section (21).

2. The battery pole piece according to claim 1, characterized in that: It also comprises a second groove (4) extending along the mechanical stretching direction, wherein the second groove (4) is arranged on the second coating section (22).

3. The battery pole piece according to claim 2, characterized in that: The current collector (1) has two side surfaces arranged opposite to each other, the second coating section (22) comprises a second primer layer (221) and a second surface layer (222), wherein: The second base coating (221) is arranged on at least one of the side surfaces, the second surface coating (222) is stacked on the second base coating (221), and the second groove (4) is arranged on the second surface coating (222).

4. The battery pole piece according to claim 3, characterized in that: The first coating section (21) comprises a first base coating layer (211) and a first surface coating layer (212), wherein the first base coating layer (211) is arranged on at least one of the side surfaces, the first surface coating layer (212) is stacked on the first base coating layer (211), and the first groove (3) is arranged on the first surface coating layer (212).

5. The battery pole piece according to any one of claims 2 to 4, characterized in that: The arrangement ratio of the second grooves (4) on any side surface of the current collector (1) is R1; The expression of R1 is: Wherein a1 is the length of the second groove (4), b1 is the width of the second groove (4), d1 is the depth of the second groove (4), n1 is the number of the second grooves (4) on any side of the current collector (1), M is the weight of the active coating (2) on any side of the current collector (1), X is the length of the second coating section (22), and S is the length of the current collector (1).

6. The battery pole piece according to claim 5, characterized in that: 0≤R1≤10％。 7. The battery pole piece according to any one of claims 1 to 4, characterized in that: The arrangement ratio of the first grooves (3) on any side surface of the current collector (1) is R2; The expression of R2 is: Wherein a2 is the length of the first groove (3), b2 is the width of the first groove (3), d2 is the depth of the first groove (3), and n2 is the number of the first grooves (3) on any side of the current collector (1).

8. A battery roll core, characterized in that: include: A separator and two battery pole pieces according to any one of claims 1 to 7, Wherein, the active coating (2) in any one of the battery pole pieces is composed of a first active substance, and the active coating (2) in another of the battery pole pieces is composed of a second active substance; The diaphragm is arranged between the two battery pole pieces to separate the two battery pole pieces.

9. The battery roll core according to claim 8, characterized in that: The expression for the length of the second coating section (22) is: Wherein x is the thickness of any one of the battery pole sheets, y is the thickness of another of the battery pole sheets, z is the thickness of the diaphragm, r is the diameter of the winding needle, and m is the number of winding turns of the second coating section (22).

10. The battery roll core according to claim 9, characterized in that: 1≤m≤50。

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