Electrode assembly and battery

Abstract

The invention relates to the technical field of battery production, in particular to an electrode assembly and a battery, the electrode assembly comprises a positive plate, a negative plate and a diaphragm, the diaphragm is arranged between the positive plate and the negative plate, and the positive plate comprises a first current collector; the first active material layer is coated on the surface of the first current collector; the positive plate comprises a first plane area positioned on the innermost ring; the positive plate further comprises a first concave-convex area located on the first active material layer, and the first concave-convex area comprises a plurality of convex parts arranged at intervals and concave parts arranged corresponding to the convex parts; a spacing distance is reserved between the first concave-convex area and the first arc section in the length direction of the electrode assembly. According to the technical scheme, the electrolyte infiltration effect can be effectively improved, and the cycle performance and the safety performance of the battery are further improved.

Description

Technical Field

[0001] The present application relates to the technical field of battery production, and in particular to an electrode assembly and a battery. Background Art

[0002] Lithium-ion batteries have been widely used in many aspects of modern society due to their advantages such as high energy efficiency and long cycle life. At the same time, continuously improving energy density has always been an important direction for battery development. Thick electrodes with large size, high loading and high compaction density play an important role in the process of high specific energy of lithium-ion batteries, because they help reduce the proportion of inactive materials inside the single cell.

[0003] During the charge and discharge process of lithium-ion batteries, the negative electrode sheets will expand, and there will be extrusion between the layers of the electrode sheets. In particular, the arc area of ​​the wound lithium-ion battery formed by winding has a large stress accumulation, and there is extrusion between the electrode sheets in the arc area itself. In addition, during the charge and discharge process, the negative electrode sheets will expand, and the extrusion between the electrode sheets will be aggravated. At the same time, this extrusion will also be transmitted from the arc area to the flat area. This interlayer extrusion will eventually lead to insufficient electrolyte and poor wetting between the layers, resulting in interface deterioration, and even lithium deposition on the negative electrode sheets, affecting the safety of the battery cell. Summary of the invention

[0004] The present application provides an electrode assembly and a battery, which are used to solve the problems of insufficient electrolyte and poor electrode wetting effect in the related art.

[0005] According to an implementation of an embodiment of the present application, an electrode assembly includes: a positive electrode sheet, a negative electrode sheet and a separator, the separator is arranged between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet includes a first current collector;

[0006] The first active material layer is coated on the surface of the first current collector; the first active material layer also includes a first electrode tab region, the first current collector is exposed from the first electrode tab region, and the positive electrode tab is located on the first current collector in the first electrode tab region.

[0007] The positive electrode sheet includes a first plane area located at the innermost circle of the battery cell and a first arc segment connected to the first plane area;

[0008] The positive electrode sheet also includes a first concave-convex area located on the first active material layer, the first concave-convex area includes a plurality of protrusions arranged at intervals and concave portions arranged corresponding to the protrusions; along the length direction of the electrode assembly, the first arc segment is not provided with the first concave-convex area.

[0009] According to an implementation manner provided in an embodiment of the present application, ends of the first active material layer on both sides of the first current collector in the first planar region close to the interior of the battery cell are flush.

[0010] According to an implementation method provided in an embodiment of the present application, the area of ​​a single side of the positive electrode sheet is S2, and the area of ​​the first concave-convex area on the single side of the positive electrode sheet is S1, wherein 10%S2≤S1≤80%S2.

[0011] According to an implementation method provided in an embodiment of the present application, the distances between the two side edges of the first concave-convex area in the width direction and the two side edges corresponding to the first active material layer are L2 and L3 respectively, wherein 1mm≤L2≤20mm, and / or 0mm≤L3≤20mm.

[0012] According to an implementation manner provided in an embodiment of the present application, along the length direction of the electrode assembly, the first planar area is not provided with a first concave-convex area.

[0013] According to an implementation method provided in an embodiment of the present application, the positive electrode sheet further includes a second planar region connected to the first arc segment and a second bent segment connected to the second planar region.

[0014] The second bending section bends in a direction close to the first plane area;

[0015] Along the length direction of the electrode assembly, the second planar area is not provided with the first concave-convex area, and / or along the length direction of the electrode assembly, the second bending section is not provided with the first concave-convex area.

[0016] According to an implementation method provided in an embodiment of the present application, a first concave-convex area is arranged around the first pole tab area, and a distance between the first pole tab area and an edge of the first concave-convex area is L1, wherein 1mm≤L1≤50mm.

[0017] According to an implementation method provided in an embodiment of the present application, the negative electrode sheet includes a second current collector and a second active material layer coated on the surface of the second current collector, and a second electrode tab region is provided on the second active material layer;

[0018] The first active material layer also includes a first adhesive tape area;

[0019] In the thickness direction of the battery cell, the projection of the first adhesive tape area and the second tab area at least partially overlap;

[0020] The distance between the periphery of the first adhesive tape area and the edge of the first concave-convex area is L4, wherein 1mm≤L4≤50mm, and / or

[0021] A second tape area is provided at the end of the first active material layer of the positive electrode sheet, and the second tape area covers part of the first active material layer and part of the first current collector. The spacing between the peripheral side of the second tape area and the edge of the first concave-convex area is L5, where 1mm≤L5≤50mm.

[0022] According to an implementation provided by an embodiment of the present application, a height h1 between the apex of the convex portion of the first concavo-convex region and the surface of the first active material layer is less than or equal to a depth h2 between the bottom of the concave portion of the first concavo-convex region and the surface of the first active material layer;

[0023] and / or, the number of convex portions is n, wherein 2≤n≤50;

[0024] and / or, the diameter of the projection of the convex portion in the thickness direction of the first active material layer is R1, and the center distance of the projection of two adjacent convex portions in the thickness direction of the first active material layer is R2, wherein 0.2R2≤R1≤R2;

[0025] And / or, the area of ​​the figure of all the convex portions corresponding to the projection in the thickness direction of the first active material layer is S5, and the area of ​​the first concavo-convex region not including the convex portions is S6, wherein 0.2S6≤S5≤2.5S6.

[0026] According to an implementation method provided in an embodiment of the present application, the tensile strength of the first current collector in the length and width direction is Rm, wherein:

[0027] The heights h1 and Rm between the apex of the convex portion of the first concavo-convex region and the surface of the first active material layer satisfy: 0.3Rm≤h1≤0.5Rm, and / or

[0028] 280MPa≤Rm;

[0029] According to an implementation provided in an embodiment of the present application, the negative electrode sheet includes a second current collector and a second active material layer coated on the surface of the second current collector.

[0030] The second active material layer includes a second tab region and a recessed region; the recessed region includes a plurality of recessed portions arranged at intervals;

[0031] The second current collector is exposed from the second electrode tab region, and the negative electrode tab is located on the second current collector in the second electrode tab region.

[0032] According to an implementation method provided in an embodiment of the present application, the concave portion of the negative electrode sheet is formed by bending a portion of the second current collector toward the second active material layer, and / or

[0033] The convex portion of the positive electrode sheet is formed by bending a side surface of the positive electrode sheet close to the center of the battery cell toward a side surface of the positive electrode sheet far from the center of the battery cell.

[0034] According to an implementation method provided in an embodiment of the present application, along the length direction of the negative electrode sheet, the negative electrode sheet includes a hollow foil area, a single-sided area with a second active material layer formed on one side of the second current collector, and a double-sided area with a second active material layer formed on both sides of the second current collector;

[0035] The second active material layer in the single-sided area is located on the surface of the second current collector on one side away from the center of the battery cell;

[0036] The single-side area is provided with a recessed area.

[0037] According to an implementation method provided in an embodiment of the present application, the single-sided area includes a third arc segment connected to the empty foil area, a third straight segment, a fourth arc segment, and a fourth straight segment; the third arc segment is bent toward a direction close to the first plane area;

[0038] The fourth arc segment is bent toward the direction close to the empty foil area; the first plane area and the third straight segment of the negative electrode sheet are arranged opposite to each other;

[0039] The protected recessed area is formed in at least one of the third arc segment, the third straight segment, the fourth arc segment or the fourth straight segment.

[0040] According to an implementation method provided in an embodiment of the present application, a spacing distance is formed between the recessed area of ​​the single-sided area and the boundary of the single-sided area close to the empty foil area; and / or

[0041] A spacing distance is formed between the concave area of ​​the single-sided area and the boundary between the single-sided area and the double-sided area.

[0042] According to an implementation method provided in an embodiment of the present application, the distances between the two side edges of the recessed area in the width direction and the two side edges of the second active material layer are L8 and L9 respectively, wherein 2mm≤L8≤30mm, and / or 0mm≤L9≤30mm.

[0043] According to an implementation method provided in an example of the present application, the negative electrode sheet includes one or more of silicon-based materials, graphite, mesophase carbon microbeads, graphene, soft carbon, hard carbon or soft / hard carbon-coated graphite materials, silicon-carbon composite materials, and silicon-oxygen composite materials.

[0044] A second aspect of the present invention provides a battery, comprising the above electrode assembly.

[0045] The electrode assembly provided by the present application includes a positive electrode sheet, a negative electrode sheet and a separator, and the separator is arranged between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes: a first current collector; a first active material layer, and the first active material layer is coated on the surface of the first current collector; the positive electrode sheet also includes a first concave-convex area located on the first active material layer, and the first concave-convex area includes a plurality of protrusions arranged at intervals and concave parts arranged corresponding to the protrusions; when the battery cell expands, the protrusions can effectively support the separator, and prevent the separator from being deformed by the expansion stress of the negative electrode sheet. At the same time, a space for accommodating electrolyte is formed between the protrusions of the positive electrode sheet and the separator, thereby increasing the storage space of the electrolyte, improving the infiltration capacity of the electrolyte in this area, and avoiding abnormal situations such as insufficient electrolyte and poor infiltration between the positive electrode and the separator.

[0046] In addition, considering that when the positive electrode sheet, the negative electrode sheet and the diaphragm are stacked and wound, the arc area of ​​the winding structure has a large stress accumulation, especially the arc segment of the innermost circle of the winding core, which has the shortest bending radius and is subjected to the greatest stress during winding. If the first concave-convex area is formed in the first arc segment, the structural stability of the active material layer of the first arc segment will be affected to a certain extent. When the first arc segment forming the first concave-convex area is bent, its bending radius is too small and the stress it is subjected to is too large, which may easily cause the active material layer of the first arc segment to fall off, that is, powder fall off. The fallen active material particles may easily fall onto the negative electrode sheet, causing a micro short circuit, and then causing the K value to be too large. Therefore, by not providing the first concave-convex area in the first arc segment, that is, the first concave-convex area is not formed on the first arc segment, the first arc segment is kept empty, thereby preventing the first arc segment from causing micro short circuits or excessive K values ​​due to powder fall off during the winding process, thereby improving the safety performance of the battery cell.

[0047] Moreover, the first arc segment is located at the innermost side of the winding core, its width direction dimension is small, and it is subjected to greater force. In the process of forming the first concave-convex area, due to its small size, it is difficult to effectively disperse the stress, which can easily cause cracks to appear on the top of the convex part in the first concave-convex area, thereby causing interface problems in this area and even the risk of lithium plating in the corresponding negative electrode sheet.

[0048] Furthermore, if the first concave-convex area is formed on the first arc segment, the first active material layer on the first arc segment becomes uneven, which increases the friction of the first active material layer, and the bending radius of the first arc segment itself is the shortest. Compared with the outer circle, the first arc segment of the positive electrode sheet and the diaphragm fit more closely. Therefore, during the winding process, the first arc segment and the diaphragm are in close contact and friction. The first concave-convex area on the first arc segment with greater roughness is prone to powder loss during the friction process, so that the active material particles fall onto the diaphragm, thereby increasing the self-discharge of the battery cell. By leaving a spacing distance between the first concave-convex area and the first arc segment, that is, the first concave-convex area is not formed on the first arc segment, and the first arc segment is kept away from air, thereby preventing the convex part of the first concave-convex area from losing powder or cobalt precipitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0050] Figure 1A schematic diagram of the surface structure of the first active material layer in a positive electrode sheet provided in an embodiment of the present application;

[0051] Figure 2 A schematic diagram of a specific structure of a first concave-convex area in a positive electrode sheet provided in an embodiment of the present application;

[0052] Figure 3 A schematic diagram of the composition structure of a pole piece provided in an embodiment of the present application;

[0053] Figure 4 A schematic diagram of the structure of the surface of the second active material layer in a negative electrode sheet provided in an embodiment of the present application;

[0054] Figure 5 This is a schematic diagram of the structure of a battery cell formed by winding an electrode assembly provided in an embodiment of the present application.

[0055] Description of reference numerals:

[0056] 100-positive electrode sheet; 110-first current collector; 120-first active material layer; 1211-first plane area; 1212-second plane area; 122-first concave-convex area; 1221-convex part; 123-first pole ear area; 1241-first adhesive tape area; 1242-second adhesive tape area; 200-negative electrode sheet; 210-second current collector; 220-second active material layer; 222-concave area; 223-second pole ear area; 300-diaphragm.

[0057] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution 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. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0059] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the present application and are not intended to limit the scope of protection of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0060] Secondly, it should be noted that in the description of the present application, terms such as "front", "rear", "left", "right", "up", "down", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the present application.

[0061] In addition, it should be noted that in the description of this application, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0062] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0063] Lithium-ion batteries have been widely used in many aspects of modern society due to their advantages such as high energy efficiency and long cycle life. At the same time, continuously improving energy density has always been an important direction for battery development. Thick electrodes with large size, high loading and high compaction density play an important role in the process of high specific energy of lithium-ion batteries, because they help reduce the proportion of inactive materials inside the single cell.

[0064] During the charge and discharge process of lithium-ion batteries, the negative electrode sheets will expand, and there will be extrusion between the layers of the electrode sheets. In particular, the arc area of ​​the wound lithium-ion battery formed by winding has a large stress accumulation, and there is extrusion between the electrode sheets in the arc area itself. In addition, during the charge and discharge process, the negative electrode sheets will expand, and the extrusion between the electrode sheets will be aggravated. At the same time, this extrusion will also be transmitted from the arc area to the flat area. This interlayer extrusion will eventually lead to insufficient electrolyte and poor wetting between the layers, resulting in interface deterioration, and even lithium deposition on the negative electrode sheets, affecting the safety of the battery cell.

[0065] In response to the above problems, an embodiment of the present application provides an electrode assembly, which includes: a positive electrode sheet 100, a negative electrode sheet 200 and a separator 300, wherein the separator 300 is arranged between the positive electrode sheet 100 and the negative electrode sheet 200, and the positive electrode sheet 100 includes: a first current collector 110, a first active material layer 120, and the first active material layer 120 is coated on the surface of the first current collector 110.

[0066] The first active material layer 120 further includes a first electrode tab region 123 . The first current collector 110 is exposed from the first electrode tab region 123 . The positive electrode tab is located on the first current collector 110 in the first electrode tab region 123 .

[0067] The positive electrode sheet 100 includes a first planar region 1211 located at the innermost circle of the battery cell and a first arc segment connected to the first planar region 1211 .

[0068] The positive electrode sheet 100 also includes a first concave-convex area 122 located on the first active material layer 120, and the first concave-convex area 122 includes a plurality of convex portions 1221 arranged at intervals and concave portions arranged corresponding to the convex portions 1221; the concave-convex area is embossed on the positive electrode sheet 100, for example, by adding an embossing roller containing the convex portions 1221 during the winding process.

[0069] Along the length direction of the electrode assembly, there is a spacing distance between the first arc segment where the first concavoconvex region 122 is not provided, that is, the first concavoconvex region 122 and the first arc segment are staggered, the first concavoconvex region 122 is not formed on the first arc segment, and the first concavoconvex region 122 can be formed on other regions except the first arc segment;

[0070] Figure 4 This is a schematic diagram of the structure of the surface of the second active material layer in a negative electrode sheet provided in an embodiment of the present application. Figure 5 This is a schematic diagram of the structure of a battery cell formed by winding an electrode assembly provided in an embodiment of the present application. Figure 4 , Figure 5As shown, the electrode assembly provided in the present application includes a positive electrode sheet 100 , a negative electrode sheet 200 and a separator 300 , and the separator 300 is disposed between the positive electrode sheet 100 and the negative electrode sheet 200 . The positive electrode sheet 100 includes: a first current collector 110; a first active material layer 120, and the first active material layer 120 is coated on the surface of the first current collector 110; the positive electrode sheet 100 also includes a first concave-convex area 122 located on the first active material layer 120, and the first concave-convex area 122 includes a plurality of convex portions 1221 arranged at intervals and concave portions arranged corresponding to the convex portions 1221; when the battery cell expands, the convex portions 1221 can effectively support the diaphragm 300, and prevent the diaphragm 300 from being deformed by the expansion stress of the negative electrode sheet 200. At the same time, a space for accommodating electrolyte is formed between the convex portions 1221 of the positive electrode sheet 100 and the diaphragm 300, thereby increasing the storage space of the electrolyte, improving the infiltration ability of the electrolyte in this area, and avoiding abnormal situations such as insufficient electrolyte and poor infiltration between the positive electrode and the diaphragm 300; furthermore, the concave portion of the first concave-convex area 122 can accommodate more electrolyte to ensure the infiltration ability of the electrolyte.

[0071] In addition, considering that when the positive electrode sheet 100, the negative electrode sheet 200 and the separator 300 are stacked and wound, the arc area of ​​the winding structure has a large stress accumulation, especially the arc segment of the innermost circle of the winding core, which has the shortest bending radius and is subjected to the greatest stress during winding. If the first concave-convex area 122 is formed in the first arc segment, the structural stability of the active material layer of the first arc segment will be affected to a certain extent. When the first arc segment forming the first concave-convex area 122 is bent, its bending radius is too small, and the stress is If the active material layer of the first arc segment is too large, it is easy to cause the active material layer of the first arc segment to fall off, that is, powder falling, and the fallen active material particles are easy to fall on the negative electrode sheet 200, causing a micro short circuit, and then causing the K value to be too large; therefore, by leaving a spacing distance without the first concave-convex area 122 in the first arc segment, that is, the first concave-convex area 122 is not formed on the first arc segment, and the first arc segment is avoided, thereby preventing the first arc segment from falling off during the winding process. The problem of micro short circuit or excessive K value, thereby improving the safety performance of the battery cell. Among them, the K value refers to the voltage drop of the battery per unit time, which is an indicator used to measure the self-discharge rate of lithium batteries.

[0072] Moreover, the first arc segment is located at the innermost side of the winding core, has a smaller dimension in the width direction, and is subjected to greater force. In the process of forming the first concave-convex area 122, due to its small size, it is difficult to effectively disperse the stress, which can easily cause cracks to appear on the top of the convex portion 1221 in the first concave-convex area 122, thereby causing interface problems in this area and even the risk of lithium deposition in the corresponding negative electrode sheet 200.

[0073] Furthermore, if the first concave-convex area 122 is formed on the first arc segment, the first active material layer 120 on the first arc segment becomes uneven, which increases the friction of the first active material layer 120, and the bending radius of the first arc segment itself is the shortest. Compared with the outer circle, the first arc segment of the positive electrode sheet 100 and the diaphragm 300 fit more closely. Therefore, during the winding process, the first arc segment and the diaphragm 300 are in close contact and friction. The first concave-convex area 122 on the first arc segment with greater roughness is prone to powder loss during the friction process, so that the active material particles fall onto the diaphragm 300, thereby increasing the self-discharge of the battery cell; by leaving a spacing distance between the first concave-convex area 122 and the first arc segment, that is, the first concave-convex area 122 is not formed on the first arc segment, and the first arc segment is avoided, thereby preventing the convex portion 1221 of the first concave-convex area 122 from losing powder or cobalt precipitation.

[0074] Figure 1 Schematic diagram of the surface structure of the first active material layer in a positive electrode sheet provided in an embodiment of the present application, Figure 2 A schematic diagram of the specific structure of the first concave-convex area in a positive electrode sheet provided in an embodiment of the present application, and Figure 3 A schematic diagram of the composition structure of a positive electrode sheet provided in an embodiment of the present application.

[0075] Reference Figure 1 As shown, in one implementation provided by an embodiment of the present application, the ends of the first active material layer 120 on both sides of the first current collector 110 of the first plane area 1211 close to the inside of the battery cell are flush. In other words, the head of the positive electrode sheet 100 is a double-sided area, that is, or the first active material layer 120 is on both sides of the first current collector 110 of the head of the positive electrode sheet 100, thereby improving the energy density of the battery cell. In addition, in the embodiment where the head of the positive electrode sheet 100 is a double-sided area, if the first arc segment is embossed, the active material layer of the first arc segment will be more uneven, and the contact area with the diaphragm 300 will be larger, so the probability of powder falling due to friction will be greater; by avoiding the first arc segment, the problem of powder falling due to excessive force in the first arc segment can be avoided while ensuring the improvement of the energy density of the battery cell.

[0076] In a specific example, the protrusion 1221 of the positive electrode sheet 100 is formed by bending one side surface of the positive electrode sheet 100 close to the center of the battery cell toward the side surface of the positive electrode sheet 100 away from the center of the battery cell, that is, the protrusion 1221 of the positive electrode sheet 100 protrudes outward from the inside of the battery cell.

[0077] It should be noted that the length of the first concave-convex area 122 is the distance between the boundary of the first protrusion at the head end of the electrode and the boundary of the last protrusion along the length direction; the width of the first concave-convex area 122 is the distance between the boundary of the first protrusion at the top of the electrode and the boundary of the lowest protrusion along the width direction. It is understandable that the positive electrode 100 may include multiple first concave-convex areas 122.

[0078] It is understandable that if the embossed first concave-convex area 122 accounts for a small proportion in the first active material layer 120, the effect of the first concave-convex area 122 in supporting and containing the electrolyte will be deteriorated; if the embossed first concave-convex area 122 accounts for a large area, it is easy to cause the first concave-convex area 122 of the electrode to be subjected to excessive force during the formation process, and the electrode is prone to wrinkling or even rupture.

[0079] like Figure 1 , Figure 2 , Figure 3 As shown, according to an implementation of the embodiment of the present application, the area of ​​a single side of the positive electrode sheet is S2, and the area of ​​the first concave-convex area 122 on the single side of the positive electrode sheet 100 is S1, wherein 10%S2≤S1≤80%S2.

[0080] Exemplarily, the embossed convex area S1 should account for 20%-70% of the overall area S2 of the single side of the electrode sheet. The embossed convex area S1 meets the above conditions, which is conducive to alleviating the expansion of the negative electrode sheet 200 and improving the infiltration effect of the electrolyte.

[0081] Furthermore, if the ratio of the embossed convex area S1 to the total area S2 of a single side of the electrode is too large, the first current collector 110 area corresponding to the first concave-convex area 122 on the electrode may be wrinkled or even ruptured due to excessive force, leading to short circuit or lithium deposition of the negative electrode 200; if the ratio is too small, the concave-convex area on the surface of the electrode will be insufficient, making it difficult to alleviate the expansion of the negative electrode 200 and improve the wetting effect of the electrolyte.

[0082] like Figure 1 , Figure 2 As shown, according to an implementation of the embodiment of the present application, the spacing between the two side edges of the first concave-convex area 122 in the width direction and the two side edges corresponding to the first active material layer 120 are L2 and L3, respectively, wherein 1mm≤L2≤20mm, 0mm≤L3≤20mm. That is to say, the bottom edge of the first concave-convex area 122 in the width direction can be flush with the bottom edge corresponding to the first active material layer 120.

[0083] Exemplarily, the first concave-convex area 122 of the pole piece is set to avoid air, and in the width direction of the pole piece, the upper and lower air-avoiding distances of the pole piece are L2 and L3 respectively. The L2 and L3 provided in the embodiment of the present application should satisfy: 3mm≤L2≤10mm, 0mm≤L3≤10mm. The spacing L2 and L3 formed by the air-avoiding setting of the embossed area of ​​the pole piece satisfying the above conditions is conducive to preventing the upper and lower edges of the pole piece in the width direction from falling off or folding due to excessive force when forming the first concave-convex area 122.

[0084] According to an implementation method of the embodiment of the present application, the first plane area 1211 is not provided with the first concave-convex area 122, that is, the first concave-convex area 122 will not be formed in the first plane area 1211 and the first arc segment, that is, the first concave-convex area 122 is arranged away from the first folding area of ​​the positive electrode sheet 100, thereby simplifying the embossing process, speeding up the preparation efficiency of the electrode sheet, and preventing the active material layer from easily falling off due to excessive stress or friction with the diaphragm 300 causing powdering and excessively large K value after the first concave-convex area 122 is formed in the first plane area 1211.

[0085] According to one implementation of the embodiment of the present application, the positive electrode sheet 100 further includes a second planar region 1212 connected to the first arc segment and a second bending segment connected to the second planar region 1212, the second bending segment is bent in a direction close to the first planar region 1211; along the length direction of the electrode assembly, the second planar region 1212 is not provided with the first concave-convex region 122, and / or along the length direction of the electrode assembly, the second bending segment is not provided with the first concave-convex region 122. In other words, the first concave-convex region 122 is not formed in the second bending segment and / or the second planar region 1212, and the second bending segment and / or the second planar region 1212 are not embossed.

[0086] Since the first fold and the second fold (i.e., the first planar area 1211 and the second planar area 1212 and the first and second arc segments) of the positive electrode sheet 100 are basically opposite to the active material layer of the single-sided area of ​​the negative electrode sheet 200, only one side of the second current collector 210 in the single-sided area has the active material layer, and the force is uneven. If the first fold and the second fold are embossed, the winding stress of the innermost circle and the second inner circle is relatively large during winding, which may easily cause powder falling due to excessive force on the first fold and the second fold of the positive electrode sheet 100 or the active material layer in the single-sided area of ​​the negative electrode sheet 200, and the fallen active material particles may easily fall onto the opposite electrode sheet, causing a short circuit.

[0087] like Figure 1 , Figure 2As shown, according to an implementation of an embodiment of the present application, the first active material layer 120 also includes a first pole lug area 123, and a first concave-convex area 122 is arranged around the first pole lug area 123, and the distance between the first pole lug area 123 and the edge of the first concave-convex area 122 is L1, wherein 1mm≤L1≤50mm.

[0088] Exemplarily, a pole lug assembly is disposed in the first pole lug region 123, and the pole lug assembly includes a positive pole lug and an insulating protective adhesive, wherein the insulating protective adhesive is made of an insulating material and is disposed corresponding to the metal pole lug to prevent lithium deposition from occurring in the metal pole lug.

[0089] According to one implementation of the embodiment of the present application, the first concave-convex area 122 and the first pole lug area 123 are arranged at intervals, that is, preferably, the three spacings L1 formed between the convex portion 1221 closest to the first pole lug area 123 in the first concave-convex area 122 and the first pole lug area 123 satisfy 3mm≤L1≤10mm.

[0090] It should be noted that the spacing L1 between the first tab area 123 and the first concave-convex area 122 can prevent the tab from being compressed and affecting the tab welding tension, and prevent the tab from compressing the current collector below the tab or wrinkling or folding the tab.

[0091] like Figure 1 , Figure 2 As shown, according to an implementation of the embodiment of the present application, the negative electrode sheet 200 includes a second current collector 210 and a second active material layer 220 coated on the surface of the second current collector 210, and a second pole lug area 223 is provided on the second active material layer 220; the first active material layer 120 also includes a first adhesive tape area 1241; in the thickness direction of the battery cell, the projection of the first adhesive tape area 1241 and the second pole lug area 223 at least partially overlap;

[0092] The spacing between the periphery of the first adhesive tape area 1241 and the edge of the first concave-convex area 122 is L4, wherein 1mm≤L4≤50mm, and / or a second adhesive tape area 1242 is provided at the end of the first active material layer 120 of the positive electrode sheet 100, the second adhesive tape area 1242 covers part of the first active material layer 120 and part of the first current collector 110, and the spacing between the periphery of the second adhesive tape area 1242 and the edge of the first concave-convex area 122 is L5, wherein 1mm≤L5≤50mm.

[0093] It should be noted that the first adhesive tape area 1241 is a protective adhesive tape area, which has the function of protecting the pole ear on the corresponding pole piece and preventing lithium deposition at the pole ear. The second adhesive tape area 1242 is provided with a finishing adhesive tape, which is the adhesive tape at the junction of the paste coating area at the end of the pole piece and the current collector. The second adhesive tape area 1242 is used to ensure that the adhesive tape covers and prevents lithium deposition at the end of the battery cell.

[0094] The first adhesive tape area 1241 and the edge of the first concave-convex area 122 are spaced apart with a spacing of 1mm≤L4≤50mm; the first adhesive tape area 1241 is used to prevent the normal deintercalation of lithium ions from the active material layer at the positive electrode sheet 100 corresponding to the negative electrode ear, thereby preventing lithium deposition at the negative electrode ear; the first concave-convex area 122 is used to avoid the first adhesive tape area 1241, thereby preventing embossing on the first adhesive tape area 1241, which makes it easy for the first adhesive tape area 1241 to be driven to fold due to insufficient adhesion, thereby causing the negative electrode ear to lose protection, and lithium deposition is likely to occur, or the adhesive tape rebounds after being compressed and a gap is formed between the active material layer.

[0095] By setting a gap between the second tape area 1242 and the first concave-convex area 122, that is, the second tape area 1242 is kept away from air, the first tape area 1241 is prevented from being easily folded due to insufficient adhesion, thereby preventing the negative electrode ear from losing protection and causing lithium deposition or the tape to rebound after being compressed and form a gap between the active material layer. It can also prevent the embossing from overwhelming the boundary between the active material layer and the current collector, and the end of the active material layer from being easily subjected to stress and powdering, thereby causing the risk of short circuit.

[0096] like Figure 3 As shown, according to one implementation of the embodiment of the present application, the height h1 between the vertex of the convex portion 1221 of the first concave-convex region 122 and the surface of the first active material layer is less than or equal to the depth h2 between the bottom of the concave portion of the first concave-convex region 122 and the surface of the first active material layer 120; that is, h1≤h2.

[0097] It should be noted that an implementation method of the embodiment of the present application limits the first protrusion height h1 and the second protrusion height h2 of the protrusion 1221 by making h1≤h2, that is, the thickness of the protrusion 1221 is thinner, thereby improving the deformation ability of the protrusion 1221, so that when the negative electrode sheet 200 expands during the charging and discharging process, the protrusion 1221 contacts the negative electrode sheet 200, and through its high deformation ability, it can partially offset the expansion stress of the negative electrode sheet 200.

[0098] In some embodiments, the number of protrusions 1221 is n, and the number of protrusions 1221 per unit area of ​​the pole piece needs to satisfy 2≤n≤50. It is understandable that the pole piece area per unit area can be, for example, 1*1mm, 2*2mm, 5*5mm, or 0.5*0.5mm.

[0099] Preferably, in the embodiment of the present application, the density of the protrusions in the convex area is limited. When the number n of the protrusions 1221 satisfies 3≤n≤20, it is beneficial to effectively improve the electrolyte storage capacity and wettability thereof, and at the same time can also have a buffering effect on the actual situation of expansion and deformation occurring during the use of the negative electrode.

[0100] In some embodiments, the diameter of the projection of the protrusion 1221 in the thickness direction of the first active material layer 120 is R1, and the center distance of the projection of two adjacent protrusions 1221 in the thickness direction of the first active material layer 120 is R2, wherein 0.2R2≤R1<R2.

[0101] Preferably, the diameter R1 of the groove of the first concave-convex area 122 and the distance R2 between the center points of the tops of the two protrusions 1221 should satisfy 0.5≤R1:R2≤0.8, and R1 and R2 satisfy the relationship, that is, the relationship between the diameter of the protrusion and the distance between the protrusions is controlled. If the ratio of R1:R2 is too small, it means that the distribution area of ​​the protrusions is relatively sparse, making it difficult for the first concave-convex area 122 to improve the infiltration of the electrolyte and alleviate the expansion of the negative electrode sheet; if the ratio of R1:R2 is too large, it means that the distribution of the protrusions 1221 is too dense, which makes it easy for the electrode sheet to be subjected to excessive force when the protrusions are formed, and the force is too concentrated, resulting in the problem of local fracture of the electrode sheet.

[0102] In some embodiments, the area of ​​the pattern of all the protrusions 1221 corresponding to the projection in the thickness direction of the first active material layer 120 is S5, and the area of ​​the first concave-convex region 122 excluding the protrusions 1221 is S6, wherein 0.2S6≤S5≤2.5S6.

[0103] Preferably, in the embodiment of the present application, 0.8≤S5:S6≤1.8 should be satisfied, and the appropriate number of convex points is more effective in improving the liquid storage capacity of the electrode, the wettability to the electrolyte, and the buffering effect on the expansion of the negative electrode. If the ratio of the area S5 of the convex portion 1221 to the area S6 of the flat area is too small, it means that the distribution area of ​​the convexity is relatively sparse, making it difficult for the first concave-convex area 122 to improve the infiltration of the electrolyte and alleviate the expansion of the negative electrode sheet 200; if the ratio is too large, it means that the distribution of the convex portion 1221 is too dense, which makes it easy for the electrode sheet to be subjected to excessive force when the convexity is formed, and the force is too concentrated, resulting in partial fracture of the electrode sheet, and then the problem of lithium precipitation.

[0104] According to one implementation of the embodiment of the present application, the tensile strength of the first current collector 110 in the length and width directions is Rm, wherein the height h1 and Rm between the apex of the convex portion 1221 of the first concave-convex region 122 and the surface of the first active material layer 120 satisfy: 0.3Rm≤h1≤0.5Rm, and / or 280MPa≤Rm.

[0105] It should be noted that in the embodiment of the present application, the first current collector 110 of the embossed electrode is limited to 280MPa≤Rm, that is, the first current collector 110 is a high-ductility aluminum foil; therefore, when the first concave-convex area 122 is embossed on the first current collector 110, the active material layer is stretched under force, and the high-ductility aluminum foil can be stretched along with the active material layer, thereby preventing the first current collector 110 from breaking; and the height between the vertex of the convex portion 1221 of the first concave-convex area 122 and the surface of the first active material layer 120 is controlled within this range. During the charge and discharge process, the first concave-convex area 122 of the positive electrode sheet 100 contacts the expanded negative electrode sheet 200, and the convex portion 1221 and the concave portion of the first concave-convex area 122 are deformed, and the first current collector 110 will also be deformed accordingly, thereby preventing the first current collector 110 from breaking during deformation, and avoiding the occurrence of lithium deposition in the battery cell. In addition, Rm and h1 satisfying the above relationship can also help alleviate the huge stress caused by the volume expansion of the battery cell during the cycle process, thereby improving the volume expansion of the battery cell.

[0106] It is worth mentioning here that the embossing depth, that is, the height h1 between the vertex of the convex portion 1221 of the first concave-convex area 122 and the surface of the first active material layer 120, is greater when the protrusion height is greater, and the required tensile strength of the aluminum foil is also greater. Therefore, the tensile strength of the aluminum foil must meet the deformation of the vertex of the convex portion 1221 of the first concave-convex area 122, and should also ensure that the current collector does not break during the deformation of the embossed pole piece.

[0107] According to an implementation of the embodiment of the present application, the first active material layer 120 includes one or more of lithium cobalt oxide, ternary material, lithium iron phosphate, lithium nickel manganese oxide, and lithium-rich manganese base.

[0108] It should be noted here that the preparation method of the positive electrode sheet 100 provided in the embodiment of the present application is: lithium cobalt oxide, a conductive agent (a mixture of conductive carbon black and carbon nanotubes), and PVDF (polyvinylidene fluoride) are placed in NMP (N-methylpyrrolidone) at a mass ratio of 97.60:1.35:1.05, and stirred evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the front and back sides of the aluminum foil, and the coating surface density is 0.01704g / cm2; after drying and rolling treatment in sequence, a positive electrode sheet 100 with a double-sided thickness of 90μm is obtained; the cut positive electrode sheet 100 is subjected to embossing processing with a special roller containing embossments, and the height of the embossment 1221 is 80-120μm, the spacing between the embossments 1221 is 0.5-5mm, and the diameter is 200-3000μm.

[0109] According to one implementation of the embodiment of the present application, the negative electrode sheet 200 includes a second current collector 210 and a second active material layer 220 coated on the surface of the second current collector 210, the second active material layer 220 includes a second pole ear region 223 and a recessed region 222; the recessed region 222 includes a plurality of recesses arranged at intervals; the second current collector 210 is exposed from the second pole ear region 223, and the negative pole ear is located on the second current collector 210 in the second pole ear region 223. By forming the recessed region 222 on the negative electrode sheet 200, the wetting effect of the electrolyte on the negative electrode sheet 200 is improved, thereby improving the power performance of the negative electrode sheet 200. The recessed region 222 can be formed, for example, by embossing or laser wire processing.

[0110] According to an implementation of the embodiment of the present application, the concave portion of the negative electrode sheet 200 is formed by bending a portion of the second current collector 210 toward the second active material layer 220 .

[0111] It is understandable that the negative electrode sheet 200 is also provided with a convex area formed by embossing on the positive electrode sheet 100, which is used to improve the wetting effect of the electrode in the electrolyte and increase the liquid storage space.

[0112] According to one implementation of the embodiment of the present application, along the length direction of the negative electrode sheet 200, the negative electrode sheet 200 includes an empty foil area, a single-sided area with a second active material layer 220 formed on one side of the second current collector 210, and a double-sided area with a second active material layer 220 formed on both sides of the second current collector 210; the second active material layer 220 in the single-sided area is located on the surface of the side of the second current collector 210 away from the center of the battery cell; the single-sided area is provided with a recessed area 222. By embossing a recessed area on the single-sided area of ​​the inner circle of the negative electrode sheet 200, the problem of uneven stress on both sides caused by the active material layer on only one side of the single-sided area of ​​the negative electrode sheet 200 is solved, which further causes the head of the negative electrode sheet 200 to be easily folded when rolled.

[0113] According to an implementation manner of the embodiments of the present application, the single-sided area includes a third arc segment, a third straight segment, a fourth arc segment and a fourth straight segment connected to the empty foil area; the third arc segment is bent in a direction close to the first plane area 1211; the fourth arc segment is bent in a direction close to the empty foil area; the first plane area 1211 and the third straight segment of the negative electrode sheet 200 are arranged opposite to each other; the recessed area 222 is formed in at least one of the third arc segment, the third straight segment, the fourth arc segment or the fourth straight segment.

[0114] According to one implementation of the embodiments of the present application, a spacing distance is formed between the recessed area 222 of the single-sided area and the boundary of the single-sided area close to the empty foil area; and / or a spacing distance is formed between the recessed area 222 of the single-sided area and the junction of the single-sided area and the double-sided area, thereby preventing the embossing roller from pressing onto the boundary of the single-sided area close to the empty foil area or the junction of the single-sided area and the double-sided area when forming the recessed area 222 of the negative electrode sheet 200. The stresses on both sides of these two places are different, and it is easy to break due to uneven force during the embossing process.

[0115] According to one implementation of the embodiment of the present application, the spacing between the two side edges of the recessed area 222 in the width direction and the two side edges of the second active material layer 220 are L8 and L9 respectively, wherein 2mm≤L8≤30mm, and / or, 0mm≤L9≤30mm. By leaving a spacing between the two side edges in the width direction, the problem of edge powdering or edge folding in the width direction can be prevented.

[0116] According to one implementation of the embodiment of the present application, the negative electrode sheet 200 includes one or more of silicon-based materials, graphite, mesophase carbon microbeads, graphene, soft carbon, hard carbon or soft / hard carbon-coated graphite materials, silicon-carbon composite materials, and silicon-oxygen composite materials.

[0117] 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. The present invention can arrange silicon grains in the pores of the porous carbon matrix by deposition, by arranging silicon grains in the pores, and by forming a carbon layer on the surface of the porous carbon matrix, and 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, ensure the structural strength of the silicon-carbon material, thereby avoiding the problems of cracking, pulverization, and shedding of the negative electrode active layer, and improving the cycle performance and rate performance of the battery.

[0118] In a specific embodiment, the carbon layer includes openings arranged corresponding to the pores of the porous carbon matrix. When the carbon layer is provided with openings, the wettability of the electrolyte to the negative electrode sheet 200 can be improved, and the expansion performance of the silicon-based material can be reduced, thereby reducing the impedance of the battery and improving the cycle performance and rate performance of the battery.

[0119] 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 negative electrode active layer 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.

[0120] 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.

[0121] In a specific embodiment, the powder resistivity of the silicon-carbon composite material and / or the silicon-oxygen composite material is 0.1-1000 Ω·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, which can improve the conductivity of the negative electrode active layer, thereby improving the cycle performance and rate performance of the battery.

[0122] 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 may lead 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.

[0123] It should be noted that the scheme for preparing the negative electrode sheet 200 in the embodiment of the present application can be to place silicon-containing artificial graphite, conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose in deionized water at a mass ratio of 97.2:0.5:1.3:1, wherein the silicon content in the silicon-containing artificial graphite is 10%; the above slurry is stirred evenly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode collector, and the negative electrode sheet 200 is obtained after drying, rolling, and slitting in sequence, and after cleaning and sheeting.

[0124] According to one implementation of the embodiment of the present application, the battery may be composed of a positive electrode sheet 100 or may be formed by winding an electrode assembly.

[0125] It should be noted that the method for preparing the battery in the embodiment of the present application can be to stack the above-mentioned cut positive electrode sheet 100, separator 300, and negative electrode sheet 200 in sequence, and then wind them into a winding core with a winding structure, and then package, inject liquid, form, and perform secondary sealing on the winding core to obtain a lithium-ion battery.

[0126] The present invention is further described below by specific examples and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, conventional materials and conventional instruments, which can be commercially available, and the reagents and materials involved can also be synthesized by conventional synthesis methods.

[0127] Embodiment 1:

[0128] 1. Preparation of positive electrode

[0129] Lithium cobalt oxide, a conductive agent (a mixture of conductive carbon black and carbon nanotubes), and PVDF are placed in NMP at a mass ratio of 97.60:1.35:1.05, and stirred evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the front and back sides of an aluminum foil, and the coating surface density is 0.01704 g / cm2; the positive electrode sheet with a double-sided thickness of 90 μm is obtained by drying and rolling (rolling compaction is 4.2) in sequence; the cut positive electrode sheet is subjected to convex processing with a special roller containing convex portions, the height of the convex portions is 80-120 μm, the convex portion spacing is 0.5-5 mm, and the diameter is 200-3000 μm, thereby obtaining the positive electrode sheet of the embodiment of the present application.

[0130] 2. Preparation of negative electrode sheet

[0131] Silicon-containing artificial graphite, conductive carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose are placed in deionized water at a mass ratio of 97.2:0.5:1.3:1, wherein the silicon content in the silicon-containing artificial graphite is 10%; the above slurry is stirred evenly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode collector, and is dried, rolled and slit in sequence, and then cleaned and sheeted to obtain a negative electrode sheet.

[0132] 3. Preparation of batteries

[0133] The separator of the present application adopts a 9μm thick substrate + ceramic + coated separator. The electrolyte includes lithium salt LiPF6 and a solvent, and the solvent includes ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), wherein the molar ratio of the three is DEC:EC:EMC=1:1:1. The above-mentioned cut positive electrode sheet 100, separator 300, and negative electrode sheet 200 are stacked in sequence and wound into a wound structure battery cell. After the battery cell is packaged, injected, formed, and second-sealed, a lithium-ion battery is obtained.

[0134] In this embodiment, the ratio of S1:S2 is 0.2, the spacing distance L2 between the first concave-convex area 122 and the edge of the first active material layer 120 is 3 mm, the spacing distance L3 between the first concave-convex area 122 and the edge of the first active material layer 120 is 3 mm, the spacing distance L1 between the peripheral side of the first electrode ear area 123 and the edge of the first concave-convex area 122 is 3 mm, the spacing distance L4 between the first adhesive tape area 1241 and the second adhesive tape area 1242 and the edge of the first concave-convex area 122 is 3 mm, and the first protrusion height h1 is 3 mm. The relationship between the protrusion height h2 satisfies h1=h2, the number of protrusions 1221 n=10, the ratio of the diameter of the projection pattern of the protrusion 1221 corresponding to the thickness direction of the first active material layer 120 to the center distance of two adjacent protrusions 1221 R1:R2=0.8, the ratio of the graphic area of ​​the projection of the protrusion 1221 corresponding to the thickness direction of the first active material layer 120 to the area of ​​the projection area of ​​the first concave-convex area 122 not including the protrusion 1221 S5:S6=2.5, the tensile strength of the first current collector 110 in the length and width direction Rm=280MPa, the ratio of the first protrusion height to the tensile strength of the first current collector 110 in the length and width direction h1:Rm=0.3

[0135] In addition, the parameter L6 on the negative electrode sheet 200 corresponds to L1, L7 corresponds to L4, and L8 and L9 correspond to L2 and L3.

[0136] Example 2

[0137] The preparation process is basically the same as that of Example 1, except that, in this embodiment, L1=L2=L3=L4=L6=L7=L8=L9=1mm.

[0138] Example 3

[0139] The preparation process is basically the same as that of Example 1, except that, in this embodiment, L1=L2=L3=L4=L6=L7=L8=L9=20mm.

[0140] Example 4

[0141] The preparation process is basically the same as that of Example 1, except that in this embodiment, the negative electrode sheet 200 and the positive electrode sheet 100 are not embossed, that is, L1=L2=L3=L4=L6=L7=L8=L9=0mm.

[0142] Example 5

[0143] The preparation process is basically the same as that of Example 1, except that, in this embodiment, L1=L2=L3=L4=L6=L7=L8=L9=25mm.

[0144] Example 6

[0145] The preparation process is basically the same as that in Example 1, except that in this example, S1:S2=0.1.

[0146] Example 7

[0147] The preparation process is basically the same as that in Example 1, except that in this example, S1:S2=0.8.

[0148] Example 8

[0149] The preparation process is basically the same as that in Example 1, except that in this example, S1:S2=0.9.

[0150] Example 9

[0151] The preparation process is basically the same as that in Example 1, except that in this example, R1=R2.

[0152] Example 10

[0153] The preparation process is basically the same as that in Example 1, except that in this example, h1:Rm=0.6.

[0154] Embodiment 11

[0155] The preparation process is basically the same as that of Example 1, except that in this embodiment, S5:S6=2

[0156] Example 12

[0157] The preparation process is basically the same as that of Example 1, except that in this example, R1:R2=0.5

[0158] Example 13

[0159] The preparation process is basically the same as that of Example 1, except that in this example, S5:S6=0.3

[0160] Comparative Example 1

[0161] The preparation process is basically the same as that of Example 1, except that both the positive electrode sheet 100 and the negative electrode sheet 200 are embossed.

[0162] The positive electrode sheet 100 and the negative electrode sheet 200 of Example 1 are replaced with the positive electrode sheet 100 and the negative electrode sheet 200 of this comparative example to obtain the battery cell of this comparative example.

[0163] The specific parameters and test results of the above embodiments and comparative examples can be found in Tables 1 to 5.

[0164] Table 1

[0165]

[0166] Table 2

[0167]

[0168] Table 3

[0169]

[0170] Table 4

[0171]

[0172] Table 5

[0173]

[0174] According to Table 1, the positive electrode sheet 100 in Example 4 is not embossed as a whole, and the head area of ​​the positive electrode sheet 100 in Comparative Example 1 is embossed. The K value of the embossed head area is 0.052, while the K value of the head area without embossing in Example 1 and Example 4 is 0.032. In Comparative Example 1, the poor coverage ratio reaches 7%, so the embossing in the head area easily causes the positive electrode sheet 100 to contact and rub with the separator 300, resulting in an increase in the K value and the poor coverage ratio.

[0175] According to Example 1, Example 2, Example 3, and Example 5 in Table 1, it can be seen that if the avoidance distance is too large, lithium deposition may occur on the electrode surface, and if the avoidance distance is too small, insufficient adhesion may occur on the battery cell interface, causing the adhesive tape to fold and bubbles to appear on the electrode surface.

[0176] Therefore, setting a space avoidance distance is beneficial to improving the machine process yield, avoiding lithium deposition at the tail of the battery cell, improving the adhesion of the battery cell, and reducing the poor coverage ratio, especially when the electrode end is not embossed, and setting a space avoidance distance between the non-embossed area and the embossed area can further improve the wettability of the battery, reduce the battery expansion change rate, and improve the battery K value to improve the battery cell yield.

[0177] According to Table 2, the ratio of the single-sided area of ​​the first concave-convex region 122 to the single-sided area of ​​the positive electrode sheet 100, S1:S2, is too large to easily cause lithium deposition on the single-sided area of ​​the negative electrode of the battery cell, and too small to cause the wrinkling problem on the surface of the electrode sheet to be not significantly improved. Therefore, when S1:S2 meets the above conditions, it is beneficial to solve the wrinkling problem of the single-sided area of ​​the electrode sheet, which can improve the process capability and solve the wrinkling problem that occurs during the preparation of the electrode sheet.

[0178] According to Table 3, a too large ratio of R1:R2 will easily cause the electrode to serpentine and the cell thickness to increase and lose ED, while a too small ratio will result in a poor electrode cycle retention rate. R1 and R2 satisfy the relationship, which is beneficial to improving the electrode wettability and cycle performance, and is not likely to cause the electrode to serpentine, thus avoiding the occurrence of cell thickness increase.

[0179] According to Table 4, a too large ratio between Rm and h1 can easily cause damage to the paste area and lithium deposition on the electrode surface. When Rm and h1 satisfy the above relationship, it can help alleviate the huge stress caused by the volume expansion of the battery cell during the cycle, thereby improving the volume expansion of the battery cell.

[0180] According to Table 5, if the ratio of the area of ​​S5:S6 is too large, it is easy to cause the convex area to wrinkle and crack, which is easy to cause lithium deposition on the electrode surface. If it is too small, it is easy to cause insufficient improvement in cycle performance. The ratio of the area S5 of the convex portion 1221 to the area S6 of the flat area satisfies the above relationship, which is conducive to improving the electrode cycle performance and reducing the risk of wrinkling and cracking of the convex area of ​​the pole piece and lithium deposition.

[0181] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0182] It should be understood that the present application is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. An electrode assembly, characterized in that: include: A positive electrode sheet (100), a negative electrode sheet (200) and a separator (300), wherein the separator (300) is arranged between the positive electrode sheet (100) and the negative electrode sheet (200). The positive electrode sheet (100) includes a first current collector (110); a first active material layer (120), the first active material layer (120) being coated on the surface of the first current collector (110); the first active material layer (120) further comprising a first electrode tab region (123), the first current collector (110) being exposed from the first electrode tab region (123), and the positive electrode tab being located on the first current collector (110) in the first electrode tab region (123); The positive electrode sheet (100) comprises a first planar area (1211) located at the innermost circle of the battery cell and a first arc segment connected to the first planar area (1211); The positive electrode sheet (100) further comprises a first concave-convex region (122) located on the first active material layer (120), the first concave-convex region (122) comprising a plurality of convex portions (1221) arranged at intervals and concave portions arranged corresponding to the convex portions (1221); along the length direction of the electrode assembly, the first arc segment is not provided with the first concave-convex region (122).

2. An electrode assembly according to claim 1, characterized in that: The first active material layer (120) on both sides of the first current collector (110) located in the first plane area (1211) is flush with the ends close to the inside of the battery cell.

3. An electrode assembly according to claim 2, characterized in that: The area of ​​a single surface of the positive electrode sheet (100) is S2, and the area of ​​the first concave-convex region (122) on the single surface of the positive electrode sheet (100) is S1, wherein 10%S2≤S1≤80%S2.

4. An electrode assembly according to claim 3, characterized in that: The spacings between the two side edges of the first concave-convex area (122) in the width direction and the two side edges corresponding to the first active material layer (120) are L2 and L3 respectively, wherein 1 mm ≤ L2 ≤ 20 mm, and / or 0 mm ≤ L3 ≤ 20 mm.

5. The electrode assembly according to claim 1, characterized in that: Along the length direction of the electrode assembly, the first planar area (1211) is not provided with the first concave-convex area (122).

6. The electrode assembly according to claim 1, characterized in that: The positive electrode sheet (100) further comprises a second plane region (1212) connected to the first arc segment and a second bent segment connected to the second plane region (1212). The second bent section bends in a direction close to the first planar area (1211); Along the length direction of the electrode assembly, the second planar area (1212) is not provided with the first concave-convex area (122), and / or along the length direction of the electrode assembly, the second bending section is not provided with the first concave-convex area (122).

7. The electrode assembly according to claim 1, characterized in that: A first concave-convex region (122) is arranged around the first pole lug region (123), and a distance between the first pole lug region (123) and an edge of the first concave-convex region (122) is L1, wherein 1 mm ≤ L1 ≤ 50 mm.

8. The electrode assembly according to claim 1, characterized in that: The negative electrode sheet (200) comprises a second current collector (210) and a second active material layer (220) coated on the surface of the second current collector (210), wherein a second electrode tab region (223) is provided on the second active material layer (220); The first active material layer (120) further includes a first adhesive tape area (1241); In the thickness direction of the battery cell, the projection of the first adhesive tape area (1241) and the second tab area (223) at least partially overlap; The distance between the peripheral side of the first adhesive tape area (1241) and the edge of the first concave-convex area (122) is L4, wherein 1mm≤L4≤50mm, and / or A second adhesive tape area (1242) is provided at the end of the first active material layer (120) of the positive electrode sheet (100), and the second adhesive tape area (1242) covers a portion of the first active material layer (120) and a portion of the first current collector (110). The spacing between the peripheral side of the second adhesive tape area (1242) and the edge of the first concave-convex area (122) is L5, wherein 1mm≤L5≤50mm.

9. The electrode assembly according to claim 1, characterized in that: A height h1 between the apex of the convex portion (1221) of the first concave-convex region (122) and the surface of the first active material layer (120) is less than or equal to a depth h2 between the bottom of the concave portion of the first concave-convex region (122) and the surface of the first active material layer (120); and / or, the number of the convex portions (1221) is n, where 2≤n≤50; and / or, the diameter of a figure of the projection of the convex portion (1221) in the thickness direction of the first active material layer (120) is R1, and the center distance of a figure of the projection of two adjacent convex portions (1221) in the thickness direction of the first active material layer (120) is R2, wherein 0.2R2≤R1≤R2; And / or, the area of ​​the figure of all the protrusions (1221) corresponding to the projection in the thickness direction of the first active material layer (120) is S5, and the area of ​​the first concave-convex region (122) not including the protrusions (1221) is S6, wherein 0.2S6≤S5≤2.5S6.

10. An electrode assembly according to claim 9, characterized in that: The tensile strength of the first current collector (110) in the length and width directions is Rm, wherein: The heights h1 and Rm between the apex of the convex portion (1221) of the first concavo-convex region (122) and the surface of the first active material layer (120) satisfy: 0.3Rm≤h1≤0.5Rm, and / or 280MPa≤Rm.

11. The electrode assembly according to claim 1, characterized in that: The negative electrode sheet (200) comprises a second current collector (210) and a second active material layer (220) coated on the surface of the second current collector (210). The second active material layer (220) comprises a second tab region (223) and a recessed region (222); the recessed region (222) comprises a plurality of recessed portions arranged at intervals; The second current collector (210) is exposed from the second pole lug region (223), and a negative pole lug is provided on the second current collector (210) in the second pole lug region (223).

12. An electrode assembly according to claim 11, characterized in that: The concave portion of the negative electrode sheet (200) is formed by bending a portion of the second current collector (210) toward the second active material layer (220), and / or The convex portion (1221) of the positive electrode sheet (100) is formed by bending a side surface of the positive electrode sheet (100) close to the center of the battery cell toward a side surface of the positive electrode sheet (100) away from the center of the battery cell.

13. The electrode assembly according to claim 11, characterized in that: Along the length direction of the negative electrode sheet (200), the negative electrode sheet (200) comprises a hollow foil area, a single-sided area having a second active material layer (220) formed on one side of the second current collector (210), and a double-sided area having second active material layers (220) formed on both sides of the second current collector (210); The second active material layer (220) in the single-sided area is located on a surface of the second current collector (210) that is away from the center of the battery cell; The single-sided area is provided with the recessed area (222).

14. An electrode assembly according to claim 13, characterized in that: The single-sided area comprises a third arc segment, a third straight segment, a fourth arc segment and a fourth straight segment connected to the empty foil area; the third arc segment is bent in a direction close to the first plane area (1211); The fourth arc segment is bent in a direction close to the empty foil area; the first plane area (1211) and the third straight segment of the negative electrode sheet (200) are arranged opposite to each other; The protected recessed area (222) is at least formed in at least one of the third arc segment, the third straight segment, the fourth arc segment or the fourth straight segment.

15. The electrode assembly according to claim 13, characterized in that: A spacing distance is formed between the concave area (222) of the single-sided area and the boundary of the single-sided area close to the empty foil area; and / or A spacing distance is formed between the concave area (222) of the single-sided area and the junction between the single-sided area and the double-sided area.

16. The electrode assembly according to claim 11, characterized in that: The distances between the two side edges of the recessed area (222) in the width direction and the two side edges of the second active material layer (220) are L8 and L9 respectively, wherein 2 mm ≤ L8 ≤ 30 mm, and / or 0 mm ≤ L9 ≤ 30 mm.

17. An electrode assembly according to any one of claims 1 to 16, characterized in that: The negative electrode sheet (200) comprises one or more of silicon-based materials, graphite, mesophase carbon microspheres, graphene, soft carbon, hard carbon or soft / hard carbon-coated graphite materials, silicon-carbon composite materials, and silicon-oxygen composite materials.

18. A battery, characterized in that: An electrode assembly comprising any one of claims 1-17.

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