Battery cell and battery

Abstract

The invention provides a battery cell and a battery, the battery cell comprises a first pole piece, a second pole piece and diaphragms, the first pole piece, the second pole piece and the diaphragms are stacked and wound, and the diaphragms are arranged between the first pole piece and the second pole piece at intervals; the first pole piece comprises a first current collector and a first active material layer arranged on the first current collector, a tab groove is formed in the first active material layer, and a tab is connected in the tab groove; the first pole piece comprises a first straight section located on the innermost ring of the battery cell, the first pole piece is provided with a concave-convex structure, the concave-convex structure comprises a plurality of protrusions arranged at intervals and pits opposite to the protrusions, and at least part of the protrusions and the pits are located on the first straight section; the ratio of the area S1 of the concave-convex structure to the area S2 of the first straight section is 20% < = S1 / S2 < = 60%. The invention is used for solving the technical problem of poor coverage of positive and negative pole pieces and a film caused by easy sliding of the pole pieces.

Description

Technical Field

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

[0002] With the rapid development of lithium-ion battery technology, lithium-ion batteries have been widely used in various fields, such as electronic equipment, aerospace, etc. People's requirements for lithium-ion batteries are getting higher and higher, especially for the improvement of the cycle life and safety performance of lithium-ion batteries.

[0003] At present, it is difficult to make breakthroughs in the development and innovation of the production materials that make up the battery. Relevant companies are committed to improving the cycle life and safety performance of lithium-ion batteries by optimizing the battery structure. In the battery production process, positive and negative electrodes, as well as separators that separate the positive and negative electrodes are required. The separator needs to completely cover the negative electrode, and the negative electrode needs to completely cover the positive electrode. However, when inserting the electrode, the electrode is prone to slipping, resulting in poor coverage of the positive and negative electrode separators, and even causing the electrode to fold, affecting the cycle life and safety of the battery.

[0004] Therefore, there is an urgent need to solve the technical problem that the pole pieces are prone to slipping, resulting in poor coverage of the positive and negative electrode diaphragms. Summary of the invention

[0005] The present invention provides a battery cell and a battery, which are used to solve the technical problem that the electrode piece is easy to slide, resulting in poor coverage of the positive and negative electrode diaphragms.

[0006] In order to achieve the above object, the present invention provides a battery cell, comprising a first pole piece, a second pole piece and a diaphragm which are stacked and wound, wherein the diaphragm is spaced between the first pole piece and the second pole piece;

[0007] The first pole piece includes a first current collector and a first active material layer disposed on the first current collector, a pole tab groove is provided in the first active material layer, the first current collector is exposed from the pole tab groove, and a pole tab is connected to the pole tab groove;

[0008] The first pole piece includes a first straight section located at the innermost circle of the battery cell, the first pole piece is provided with a concave-convex structure, the concave-convex structure includes a plurality of protrusions arranged at intervals and pits arranged opposite to the protrusions, and at least part of the protrusions and the pits are located in the first straight section;

[0009] The second pole piece includes a second current collector and a second active material layer disposed on the second current collector, the second active material layer is provided with a plurality of grooves, and the surface where the pits of the first pole piece are located and the surface where the grooves are located are arranged opposite to each other;

[0010] The ratio of the area S1 of the concavo-convex structure to the area S2 of the first straight section is: 20%≤S1 / S2≤60%.

[0011] The present invention provides a battery cell, in which a concave-convex structure is provided on the first pole piece, wherein the concave-convex structure includes a plurality of protrusions arranged at intervals and pits arranged opposite to the protrusions, and at least some of the protrusions and the pits are located in the first straight section, which can effectively improve the plane roughness of the first straight section. During battery production, the contact area between the first straight section and other components is increased, and the friction force on the surface of the first straight section of the inner circle of the battery cell is improved, which prevents the first pole piece from sliding, wrinkling and folding when entering the sheet, thereby improving the safety of the battery. At the same time, it also allows the first straight section to better fit the diaphragm, increases the contact area, reduces the possibility of sliding, prevents the first straight section of the first pole piece from being subjected to excessive stress during the winding process, and effectively disperses the stress of the first straight section.

[0012] The second active material layer of the second pole piece is provided with a plurality of grooves, and the surface where the pits of the first pole piece are located and the surface where the grooves are located are arranged opposite to each other, that is, the grooves of the second pole piece can be located in the innermost circle of the battery cell, and the grooves are opposite to the pits of the first pole piece, thereby increasing the friction force of the head of the second pole piece, so that the second pole piece can better fit the diaphragm and increase the contact area. When the positive pole piece, the diaphragm and the negative pole piece are wound into sheets, the three can be effectively bonded together and wound to improve the winding efficiency. At the same time, the positive pole piece and the diaphragm are better fitted, and it can also prevent the diaphragm located at the head of the innermost circle of the battery cell from moving when the winding needle fixing the diaphragm is pulled out after the winding is completed.

[0013] In addition, in the present application, the ratio of the area S1 of the concave-convex structure 30 to the area S2 of the first straight section is: 20%≤S1 / S2≤60%. If the ratio S1 / S2 is too small, the friction force on the surface of the first straight section and the effect of improving the support of the first pole piece will not be obvious; on the contrary, if the ratio S1 / S2 is too large, the concave-convex structure will occupy too large an area of ​​the first pole piece, which may cause the first active material layer on the first pole piece to fall off during the processing of the concave-convex structure, that is, the problem of powder falling off. The falling first active material layer may easily cause the problem of short circuit of the battery cell, which is not conducive to ensuring the safety of the battery.

[0014] In one possible implementation, the first pole piece includes a double-sided coating area where the first active material layer is disposed on both sides of the first current collector, the first straight section is located in the double-sided coating area, and the protrusion protrudes from the surface of the double-sided coating area.

[0015] In a possible implementation, at least a portion of the openings of the recesses are oriented toward the center of the battery cell.

[0016] In one possible implementation, a height H1 of the concave-convex structure protruding from the first active material layer, a thickness H2 of the first active material layer located in the double-sided coating area, and a thickness H3 of the first current collector satisfy: 0.1×H2-0.8×H3≤H1≤0.8×H2-0.8×H3.

[0017] In a possible implementation, along the length direction of the first pole piece:

[0018] The length L1 of the first straight section satisfies: 4mm≤L1≤100mm; and / or,

[0019] The first straight section has a first side, and a distance L2 between the concave-convex structure and the first side satisfies 1mm≤L2≤5mm.

[0020] In a possible implementation, along the width direction of the first pole piece:

[0021] The distance between the concavo-convex structure and the edge of the first active material layer is T1, and the width of the first active material layer is T2, wherein 5% T2≤T1≤45% T2.

[0022] In a possible implementation, the double-sided coating area further includes a first bent section and a second straight section, and the first straight section, the first bent section and the second straight section are sequentially connected along the length direction of the first pole piece;

[0023] An end of the concave-convex structure away from the first side is a cut-off end, and the cut-off end is located in the first straight section or the first bent section or the second straight section.

[0024] In a possible implementation, the protrusion is rhombus-shaped; and / or,

[0025] The angle θ between two adjacent sides of the rhombus satisfies 20°<θ<90°; and / or,

[0026] The side length a of the rhombus satisfies 2mm≤a≤8mm; and / or,

[0027] The distance b between two adjacent protrusions satisfies 0.5 mm ≤ b ≤ 3 mm.

[0028] In a possible implementation, the protrusion is circular, and a diameter D of a circumscribed circle of the protrusion satisfies 0.3 mm ≤ D ≤ 8 mm, and / or projections of two adjacent protrusions on the plane where the first pole piece is located do not overlap.

[0029] In a possible implementation, a distance c between the centers of a circumscribed circle of two adjacent protrusions on a plane where the first pole piece is located satisfies 1 mm ≤ c ≤ 6 mm.

[0030] In a possible implementation, the protrusion is linear;

[0031] The width e of the protrusion satisfies 1mm≤e≤8mm; and / or,

[0032] The distance f between two adjacent protrusions satisfies 2mm≤f≤10mm.

[0033] In a possible implementation manner, a height H1 of the concavo-convex structure protruding from the first active material layer satisfies: 2 μm≤H1≤80 μm.

[0034] In one possible implementation, the first pole piece also includes a single-sided coating area with the first active material layer provided on one side, and an empty foil area without the first active material layer provided on both sides. Along the length direction of the first pole piece, the double-sided coating area, the single-sided coating area and the empty foil area are connected in sequence.

[0035] In a possible implementation, in the thickness direction of the battery cell, the concave-convex structure at least partially overlaps with a projection of the electrode tab.

[0036] The present invention also provides a battery, comprising the above-mentioned battery cell.

[0037] In the present invention, the first pole piece is a positive pole piece, and the second pole piece is a negative pole piece. By providing a concave-convex structure on the first pole piece, the surface roughness of the positive pole piece can be effectively increased, the anti-slip performance of the positive pole piece can be improved, and the problem of easy sliding and folding of the positive pole piece in the battery cell can be improved.

[0038] The present invention provides a battery cell and a battery. By controlling the height H1 of the concave-convex structure protruding from the first active material layer, the thickness H2 of the first active material layer located in the double-sided coating area, and the thickness H3 of the first current collector, the three satisfying: 0.1×H2-0.8×H3≤H1≤0.8×H2-0.8×H3, the height H1 of the concave-convex structure protruding from the first active material layer can be effectively controlled to match the thickness of the protrusion, the thickness of the first current collector and the thickness of the first active material layer, thereby preventing H1 from being too large and causing the corresponding position of the positive electrode sheet to be crushed when processing the concave-convex structure, thereby preventing safety problems such as positive electrode sheet breakage and short circuit.

[0039] The battery cell and battery provided by the present invention can prevent the problem of powder falling off at the edge of the positive electrode sheet when processing the concave-convex structure by providing a certain distance between the edge of the concave-convex structure and the edge of the double-sided coating area.

[0040] In addition to the technical problems solved by the embodiments of the present invention described above, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of the technical solutions, other technical problems that can be solved by a battery cell and a battery provided by the embodiments of the present invention, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention 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 invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 A schematic diagram of the structure of a battery cell provided in an embodiment of the present invention;

[0043] Figure 2 A schematic diagram of the structure of a first pole piece of a battery cell provided in an embodiment of the present invention;

[0044] Figure 3 A cross-sectional view of the concave-convex structure of the first pole piece of the battery cell provided by an embodiment of the present invention;

[0045] Figure 4 A top view of a first pole piece of a battery cell provided in an embodiment of the present invention;

[0046] Figure 5 A bottom view of a first pole piece of a battery cell provided in an embodiment of the present invention;

[0047] Figure 6 A top view of another first pole piece of the battery cell provided in an embodiment of the present invention;

[0048] Figure 7 A bottom view of another first pole piece of the battery cell provided in an embodiment of the present invention;

[0049] Figure 8 for Figure 7 A magnified view of the local structure;

[0050] Fig. 9 A top view of another first pole piece of the battery cell provided in an embodiment of the present invention;

[0051] Fig.10 A bottom view of another first pole piece of the battery cell provided in an embodiment of the present invention.

[0052] Description of reference numerals:

[0053] 10- first current collector;

[0054] 11- Single-sided coating area;

[0055] 12-empty foil area;

[0056] 20-first active material layer;

[0057] 30-concave-convex structure;

[0058] 31- convex;

[0059] 311-pit;

[0060] 32-cutoff end;

[0061] 40-double-sided coating area;

[0062] 41- first straight section;

[0063] 411-first side;

[0064] 42-first bending section;

[0065] 43- the second straight section;

[0066] 44-ear slot;

[0067] 50-first pole piece;

[0068] 60- second pole piece;

[0069] 70 - diaphragm;

[0070] 80-Pole ear. DETAILED DESCRIPTION

[0071] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0072] In the roll core structure of a wound lithium-ion battery, the positive electrode sheet usually has a double-sided coating area, a single-sided coating area and a blank foil area. The double-sided coating area is on the inner side of the roll core, and the first end of the double-sided coating area is the end where the roll core starts to be wound, that is, the starting end where the positive electrode sheet is inserted.

[0073] The pole piece used in the core is usually a long sheet structure. The longer the pole piece is, the more active material can be coated on the surface, which can increase the capacity of the battery cell. The longer pole piece can also prevent the problem of excessive cycle expansion and capacity attenuation caused by excessive rebound of the pole piece. When the pole piece forms a core, the double-sided coating area in the positive pole piece is stacked together with the diaphragm and the negative pole piece at the beginning of the core winding to form the starting end of the core winding. After the pole piece is wound, it is bent, and along the thickness direction of the core, multiple straight sections are arranged roughly in parallel.

[0074] During the processing of the positive electrode sheet, after the surface is coated with the positive electrode active material layer slurry, it is dried and rolled, and the surface of the positive electrode sheet is relatively smooth. In the process of forming the core, the first straight section located at the innermost circle of the core is subjected to bending and extrusion force, and the electrode sheet is prone to sliding and wrinkling, resulting in poor coverage of the positive and negative electrode separators, and easy contact between the positive and negative electrodes and thus short circuits. In addition, the positive electrode sheet is relatively hard and has poor toughness. When the positive electrode sheet is inserted, it is easy to be squeezed, folded, and broken, resulting in abnormal gaps between the electrode sheets, which in turn causes the contact interface of the electrode sheets to deteriorate and black spots and even lithium precipitation to appear on the interface after cycling, affecting the safety of the battery.

[0075] The following describes a cell and a battery provided by an embodiment of the present invention with reference to the accompanying drawings.

[0076] refer to Figure 1 and Figure 2 As shown, the present invention provides a battery cell, comprising a first pole sheet 50, a second pole sheet 60 and a separator 70 which are stacked and wound, wherein the separator 70 is arranged between the first pole sheet 50 and the second pole sheet 60; the first pole sheet 50 comprises a first current collector 10 and a first active material layer 20 arranged on the first current collector 10, wherein a pole lug groove 44 is opened in the first active material layer 20, the first current collector 10 is exposed from the pole lug groove 44, and a pole lug 80 is connected to the pole lug groove 44.

[0077] The first pole piece 50 includes a first straight section 41 located at the innermost circle of the battery cell. The first pole piece 50 is provided with a concave-convex structure 30. Figure 3 and Figure 4 As shown, the concave-convex structure 30 includes a plurality of protrusions 31 arranged at intervals and concave pits 311 arranged opposite to the protrusions 31 , and at least part of the protrusions 31 and the concave pits 311 are located in the first straight section 41 .

[0078] The second pole piece 60 includes a second current collector and a second active material layer disposed on the second current collector. The second active material layer is provided with a plurality of grooves. The surface where the pits 311 of the first pole piece 50 are located and the surface where the grooves are located are disposed opposite to each other.

[0079] The present invention provides a battery cell, wherein a first pole piece 50 is provided with a concave-convex structure 30, the first pole piece 50 may be a positive pole piece, the second pole piece 60 may be a negative pole piece, at least part of the concave-convex structure 30 is located in a first straight section 41, and the ratio of the area S1 of the concave-convex structure 30 to the area S2 of the first straight section 41 is: 20%≤S1 / S2≤60%, which can effectively improve the plane roughness of the first straight section 41, and improve the friction force on the surface of the first straight section 41 during battery production, so as to prevent the positive pole piece from being inserted into the battery. It can produce sliding, wrinkling and folding effects, thereby reducing the problems of contact interface deterioration and lithium deposition caused by abnormal gaps between the pole pieces, and also help to ensure that the diaphragm 70 completely covers the negative electrode sheet, and the negative electrode sheet completely covers the positive electrode sheet, thereby improving the safety of the battery. At the same time, it also allows the first straight section 41 to better fit the diaphragm, increase the contact area, and reduce the possibility of sliding. It can prevent the first straight section 41 of the positive electrode sheet from being subjected to excessive stress during the winding process, and effectively disperse the stress of the first straight section 41.

[0080] The second active material layer of the second pole piece 60 is provided with a plurality of grooves, and the surface where the pits 311 of the first pole piece 50 are located is arranged opposite to the surface where the grooves are located, that is, the grooves of the second pole piece can be located in the innermost circle of the battery cell, and the grooves and the pits 311 of the first pole piece are arranged opposite to each other, thereby increasing the friction force of the head of the negative pole piece, so that the second pole piece can better fit the diaphragm and increase the contact area. When the positive pole piece, diaphragm and negative pole piece are wound, the three can be effectively wound together to improve the winding efficiency. At the same time, the positive pole piece and the diaphragm are better fitted, and it can also prevent the diaphragm at the head from moving when the winding needle fixing the diaphragm is pulled out after the winding is completed.

[0081] The ratio of the area S1 of the concavo-convex structure 30 to the area S2 of the first straight section 41 is: 20%≤S1 / S2≤60%. If the ratio S1 / S2 is too small, the friction force on the surface of the first straight section 41 and the supporting effect of the first pole piece 50 will not be obvious; on the contrary, if the ratio S1 / S2 is too large, the concavo-convex structure 30 will occupy too large an area of ​​the first pole piece 50, which may cause the first active material layer 20 on the first pole piece 50 to fall off during the processing of the concavo-convex structure 30, that is, the problem of powder falling off may occur. The falling first active material layer 20 may easily cause the problem of short circuit of the battery cell, which is not conducive to ensuring the safety of the battery.

[0082] In a possible implementation, the ratio of the area S1 of the concavo-convex structure 30 to the area S2 of the first straight section 41 is S1 / S2, where S1 / S2 can be 20%, 25%, 30%, 36%, 40%, 43%, 50%, 57% or 60%. This can effectively increase the friction force on the surface of the first straight section 41 and improve the lamination effect of the first pole piece 50, and also leave a certain space between the edge of the first pole piece 50 and the edge of the concavo-convex structure 30 to prevent powder from falling off at the edge of the first pole piece 50.

[0083] In a possible implementation, the concave-convex structure 30 includes, but is not limited to, a diamond shape, a circle, a waist shape, an ellipse shape, etc., and may also be a pattern shape, etc.

[0084] In a possible implementation, the first pole piece 50 includes a double-sided coating area 40 in which the first active material layer 20 is provided on both sides of the first current collector 10, the first straight section 41 is located in the double-sided coating area 40, and the concave-convex structure 30 is formed in the double-sided coating area 40. The double-layer first active material layer can effectively improve the overall energy density, and at the same time, the first straight section with the first active material layer on both sides can evenly disperse the pressure of the roller during embossing, so that the force on both sides is uniform.

[0085] In one possible implementation, the protrusion 31 protrudes from the surface of the double-sided coating area 40, and the pit 311 is formed in the protrusion 31. The opening of the pit 311 is opposite to the protruding direction of the protrusion 31, and the concave-convex structure 30 can be a pattern structure formed by rolling.

[0086] Since the protrusions 31 protrude from the surface of the double-sided coating area 40, the position where the concave-convex structure 30 is arranged in the double-sided coating area 40 is no longer a smooth plane, thereby increasing the anti-slip friction of the first pole piece 50 and preventing the positive pole piece from sliding, wrinkling and folding when being inserted.

[0087] In a possible implementation, the plurality of protrusions 31 may be arranged in a plurality of rows and a plurality of columns, and the plurality of protrusions 31 may also be arranged in a circular ring shape.

[0088] In one possible implementation, in the concave-convex structure 30, all protrusions 31 may have the same protrusion direction, or a portion of the multiple protrusions 31 may have the same protrusion direction and the other portion of the protrusions 31 may have the opposite protrusion direction, which is not specifically limited here.

[0089] In a possible implementation, when preparing the winding core, the openings of the pits 311 are all facing away from the center of the winding core, which can also prevent the positive electrode sheet from sliding, wrinkling and folding when it is inserted.

[0090] In a possible implementation, at least part of the openings of the recesses 311 face the center of the core. With this structure, since the recesses 311 can accommodate and store some electrolyte, more electrolyte can be stored inside the core, which helps to improve the efficiency of the battery and ensure the normal circulation of the battery cell.

[0091] In a possible implementation, when preparing the winding core, the openings of all the recesses 311 face the center of the winding core, so as to maximize the amount of electrolyte that can be stored in the recesses 311 and improve the efficiency of the battery.

[0092] In one possible implementation, reference Figure 3 As shown, the height H1 of the concavo-convex structure 30 protruding from the first active material layer 20, the thickness H2 of the first active material layer 20 located in the double-sided coating area 40, and the thickness H3 of the first current collector 10 all satisfy: 0.1×H2-0.8×H3≤H1≤0.8×H2-0.8×H3. The purpose is to make the thickness of the protrusion, the thickness of the first current collector and the thickness of the first active material layer match each other under the premise of improving the easy sliding and wrinkling of the pole piece in the battery cell, and to prevent the pole piece from being crushed when processing the concavo-convex structure, so as to avoid causing new problems to the pole piece, such as causing pole piece breakage, lithium precipitation, short circuit and other safety problems.

[0093] In one possible implementation, H1 can be, for example: 0.1×H2-0.8×H3, or 0.2×H2-0.8×H3, or 0.3×H2-0.8×H3, or 0.4×H2-0.8×H3, or 0.5×H2-0.8×H3, or 0.6×H2-0.8×H3, or 0.7×H2-0.8×H3, or 0.8×H2-0.8×H3.

[0094] If H1>0.8×H2-0.8×H3, it means that the height of the concave-convex structure 30 protruding from the first active material layer 20 is too high, which may easily cause the corresponding position of the positive electrode sheet to be crushed when processing the concave-convex structure, thereby causing the electrode sheet to be damaged, broken or lithium deposited, affecting the safety of use; if H1<0.1×H2-0.8×H3, it means that the height of the concave-convex structure 30 protruding from the first active material layer 20 is too small, which will make the improvement of the anti-slip effect of the double-sided coating area 40 not obvious.

[0095] When processing the concave-convex structure 30, the first current collector 10 and the first active material layer 20 are deformed together. Therefore, the protrusion height H1 of the concave-convex structure 30 protruding from the first active material layer 20 will be affected by the thickness H2 of the first active material layer 20 located in the double-sided coating area 40 and the thickness H3 of the first current collector 10. Through the above relationship, the three are matched with each other, which can prevent the electrode from being crushed when processing the concave-convex structure, avoiding new problems for the electrode, such as causing safety problems such as electrode breakage, lithium deposition, and short circuit.

[0096] In one possible implementation, reference Figure 3 As shown, the height H1 of the concavo-convex structure 30 protruding from the first active material layer 20 satisfies: 2 μm≤H1≤80 μm, which helps to stabilize the distance between the first straight section 41 of the first pole piece 50 and other adjacent components.

[0097] In a possible implementation, a height H1 of the concavo-convex structure 30 protruding from the first active material layer 20 may be, for example, 2 μm, 10 μm, 20 μm, 30 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm or 80 μm.

[0098] In one possible implementation, reference Figure 4 As shown, along the length direction of the first pole piece 50: the length L1 of the first straight section 41 satisfies: 4mm≤L1≤100mm. This facilitates reducing the thickness of the winding core when the first pole piece 50 is processed into a winding core, thereby reducing the thickness of the battery, so that the battery can be applied to some lightweight products and expand the application range of the battery; at the same time, it is ensured that the concave-convex structure on the first straight section has sufficient size to ensure its friction.

[0099] In one possible implementation, along the length direction of the first pole piece 50, the length L1 of the first straight section 41 may be, for example, 4 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm or 100 mm.

[0100] In one possible implementation, reference Figure 4 As shown, along the length direction of the first pole piece 50: the first straight section 41 has a first edge 411, and the spacing L2 between the concave-convex structure 30 and the first edge 411 satisfies 1mm≤L2≤5mm. The first edge 411 is located at one end of the length direction of the double-sided coating area 40, and the first edge 411 is the starting position of winding when the first pole piece 50 is processed into a winding core.

[0101] In a possible implementation, along the length direction of the first pole piece 50 , the spacing L2 between the concave-convex structure 30 and the first edge 411 may be, for example, 1 mm, 1.5 mm, 2 mm, 2.2 mm, 2.6 mm, 3 mm, 4 mm or 5 mm.

[0102] This is because it is necessary to apply a certain pressure to the first pole piece 50 when processing the concave-convex structure 30. If the spacing L2 is too small, it means that the distance between the concave-convex structure 30 and the first edge 411 is relatively close. When processing the concave-convex structure 30, after applying a certain pressure to the first pole piece 50, the first active material layer 20 is likely to fall off near the first edge 411, i.e., powdering problem occurs. On the contrary, if the spacing L2 is too large, it means that the distance between the concave-convex structure 30 and the first edge 411 is relatively far, which will reduce the arrangement area of ​​the concave-convex structure 30, which is not conducive to improving the anti-slip performance of the first pole piece 50.

[0103] In the present application, the spacing L2 satisfies 1mm≤L2≤5mm, so that there is a sufficient spacing between the concavo-convex structure 30 and the first edge 411, thereby avoiding the problem of the first active material layer 20 falling off near the first edge 411 when processing the concavo-convex structure 30. In addition, the area of ​​the concavo-convex structure 30 is not too small, thereby ensuring a significant improvement in the anti-slip performance.

[0104] In one possible implementation, reference Figure 5 As shown, along the width direction of the first pole piece 50: the spacing between the concavo-convex structure 30 and the edge of the first active material layer 20 is T1, and the width of the first active material layer 20 is T2, wherein 5% T2≤T1≤45% T2. Such a structure allows a certain spacing T1 between the edge of the concavo-convex structure 30 and the edge of the first active material layer 20, in order to prevent the spacing T1 from being too small, resulting in the problem of powder falling off the edge of the first pole piece 50 when processing the concavo-convex structure 30, and also to prevent the spacing T1 from being too large, resulting in the area of ​​the concavo-convex structure 30 being insufficient to significantly improve the anti-slip effect of the first straight section 41, so that the first pole piece 50 has better comprehensive performance.

[0105] In one possible implementation, T1 may be, for example, 5% T2, 10% T2, 15% T2, 20% T2, 25% T2, 30% T2, 34% T2, 40% T2, or 45% T2.

[0106] In one possible implementation, reference Figure 4As shown, the double-sided coating area 40 also includes a first bending section 42 and a second straight section 43, and the first straight section 41, the first bending section 42 and the second straight section 43 are connected in sequence along the length direction of the first pole piece 50; the end of the concave-convex structure 30 away from the first edge 411 is the cut-off end 32, and the cut-off end 32 is located in the first straight section 41 or the first bending section 42 or the second straight section 43.

[0107] The position of the cut-off end 32 is not specifically limited here. The cut-off end 32 may be coincident with the end of the first straight section 41 away from the first edge 411, or the cut-off end 32 may be spaced greater than 1 mm from the end of the first straight section 41 away from the first edge 411. For example, the cut-off end 32 is located at the first bending section 42 or the second straight section 43. In the embodiment where the cut-off end 32 is located at the first bending section 42, that is, the concave-convex structure is also on the first bending section 42, it is understandable that the first bending section 42 is subjected to excessive bending stress compared with the first straight section 41 or the second straight section 43, and the concave-convex structure can effectively improve the deformation ability of the pole piece, thereby preventing the first bending section 42 from breaking due to excessive force.

[0108] In a possible implementation, when the pole piece is processed into a winding core, multiple straight sections are arranged roughly in parallel along the thickness direction of the winding core. Exemplarily, when the pole piece is processed into a winding core, the double-sided coating area 40 may also include a third straight section, a fourth straight section...the Nth straight section, etc., wherein N is a natural number, and every two adjacent straight sections are connected by a bending section, and the straight section located at the most central position of the winding core is the first straight section 41, wherein the first straight section 41, the second straight section 43, the third straight section, the fourth straight section...the Nth straight section are roughly parallel.

[0109] In one possible implementation, reference Figure 6 , Figure 7 and Figure 8 As shown, the protrusion 31 is in a rhombus shape, the angle θ between two adjacent sides of the rhombus satisfies 20°<θ<90°, the side length a of the rhombus satisfies 2mm≤a≤8mm, and the spacing b between two adjacent protrusions 31 satisfies 0.5mm≤b≤3mm. Such a structure makes the protrusion 31 in the concavo-convex structure 30 have better stability and support when it is in a rhombus shape.

[0110] When the spacing b between two adjacent protrusions 31 is less than 0.5, the spacing between two adjacent diamond-shaped protrusions 31 is too small, and the protrusions 31 are easily overlapped during the processing of the protrusions 31, or the local force on the double-sided coating area 40 is too large, resulting in damage to the first pole piece 50; when the spacing between two adjacent diamond-shaped protrusions 31 is greater than 3mm, the span between the two adjacent diamond-shaped protrusions 31 is too large, which cannot effectively improve the roughness of the double-sided coating area 40, and it is difficult to effectively improve the problem of easy sliding of the double-sided coating area 40 of the first pole piece 50.

[0111] Therefore, in the present application, by satisfying the spacing b between two adjacent protrusions 31 of 0.5mm≤b≤3mm, it is possible to prevent the overlap of the two adjacent protrusions 31 and the damage of the first pole piece 50 caused by excessive local force in the double-sided coating area 40. It can also effectively improve the problem of easy sliding of the double-sided coating area 40 of the first pole piece 50, thereby helping to ensure that the positive and negative pole pieces are in the correct positions during the preparation of the winding core.

[0112] Two adjacent angles in a rhombus are complementary, that is, the sum of two adjacent angles in a rhombus is 180°.

[0113] If the angle θ between two adjacent sides in the rhombus is too small, the edge of the protrusion 31 will be too sharp. In the present application, the angle θ between two adjacent sides in the rhombus satisfies 20°<θ<90°, which can avoid the edge of the protrusion 31 being too sharp, thereby avoiding piercing the first pole piece 50 and affecting the service life of the first pole piece 50.

[0114] In one possible implementation, the angle between two adjacent sides in the rhombus is rounded rather than sharp, to prevent damage to the first active material layer 20 or piercing of the first current collector 10 due to an excessively hard and sharp angle, thereby preventing damage to the first pole piece 50. In the present application, the angle between two adjacent sides in the rhombus protrusion 31 is rounded, and the radius of the rounded corner is 1 mm. The purpose is to prevent the angle between the two adjacent sides from being too sharp, which is beneficial to avoid damaging the first active material layer 20 or piercing the first current collector 10, thereby ensuring the service life of the first pole piece 50.

[0115] In a possible implementation, the angle θ between two adjacent sides of the rhombus may be, for example, 25°, 30°, 45°, 60°, 75°, 80°, etc.

[0116] In a possible implementation, the side length a of the rhombus may be, for example, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 5.5 mm, 6 mm, 7 mm, or 8 mm.

[0117] In a possible implementation, the interval b between two adjacent protrusions 31 may be, for example, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm.

[0118] In one possible implementation, reference Figure 4 and Figure 5 As shown, the protrusion 31 is circular, the diameter D of the circumscribed circle of the protrusion 31 satisfies 0.3mm≤D≤8mm, the projections of two adjacent protrusions 31 on the plane where the first pole piece 50 is located do not overlap, and the distance c between the centers of the circumscribed circles of two adjacent protrusions 31 on the plane where the first pole piece 50 is located satisfies 1mm≤c≤6mm. Such a structure makes the protrusion 31 in the concave-convex structure 30 have better stability and support when it is circular, avoiding the problem of collapse of the protrusion 31 and affecting the storage of electrolyte in the pit 311.

[0119] When the diameter D of the circumscribed circle is too small, it is easy to cause the tip effect, resulting in damage to the first pole piece 50. When the diameter D of the circumscribed circle is too large, the edge span of the protrusion 31 is too large, which is not conducive to playing an effective supporting role between the positive and negative pole pieces. The protrusion 31 is prone to collapse, affecting the improvement of the anti-slip performance of the pole piece. In this application, by controlling 0.3mm≤D≤8mm, the protrusion 31 has better support, which also helps to prevent the problem of pole piece damage caused by the tip effect, thereby improving the safety of battery use.

[0120] When the distance c between the centers of the circumscribed circles of the plane where the first pole piece 50 is located is too small, it is easy to cause the two adjacent protrusions 31 to overlap and cause the first pole piece 50 to be damaged; when the distance c between the centers of the circumscribed circles of the plane where the first pole piece 50 is located is too large, the two adjacent protrusions 31 cannot provide stable support, and it is not conducive to significantly improving the anti-skid effect of the double-sided coating area 40. The present application can effectively reduce the problem of the first pole piece 50 being damaged due to the overlap of the two adjacent protrusions 31 and significantly improve the anti-skid effect of the double-sided coating area 40 by controlling 1mm≤c≤6mm.

[0121] In a possible implementation, the diameter D of the circumscribed circle of the protrusion 31 may be, for example, 1 mm≤D≤3 mm.

[0122] In one possible implementation, the diameter D of the circumscribed circle of the protrusion 31 may be, for example, 0.3 mm, 1 mm, 1.3 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 5.5 mm, 6 mm, 7 mm or 8 mm.

[0123] In a possible implementation, a distance c between the centers of the circumscribed circle of two adjacent protrusions 31 on the plane where the first pole piece 50 is located may be, for example, 1.5 mm≤c≤4 mm.

[0124] In a possible implementation, a distance c between the centers of a circumscribed circle of two adjacent protrusions 31 on the plane where the first pole piece 50 is located may be, for example, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 5.5 mm or 6 mm.

[0125] In one possible implementation, reference Fig. 9 and Fig.10 As shown, the protrusion 31 is linear, the width e of the protrusion 31 satisfies 1mm≤e≤8mm, and the spacing f between two adjacent protrusions 31 satisfies 2mm≤f≤10mm.

[0126] In this example, when the width e of the protrusion 31 is less than 1 mm, not only will the processing difficulty of the protrusion 31 be increased, but it will also easily cause the first pole piece 50 to be damaged. When the width e of the protrusion 31 is greater than 8 mm, it will affect the support strength of the protrusion 31 itself, and the protrusion 31 will easily collapse, which is not conducive to providing a stable anti-slip effect. Therefore, in this application, the width e of the protrusion 31 satisfies 1mm≤e≤8mm, which can not only reduce the problem of damage to the first pole piece 50, but also ensure the support strength of the protrusion 31 itself.

[0127] When the spacing f is less than 2mm, the spacing f between two adjacent protrusions 31 is too small, and the two adjacent protrusions 31 are easily overlapped during the production process, or the local force is too large to cause the first pole piece 50 to be damaged. When the spacing f is greater than 10mm, the span between two adjacent protrusions 31 is too large to play an effective role in manufacturing roughness, so it is difficult to effectively improve the problem of easy sliding of the double-sided coating area 40 of the first pole piece 50. The present application can effectively reduce the problem of damage to the first pole piece 50 and effectively improve the problem of easy sliding of the double-sided coating area 40 of the first pole piece 50 by controlling the spacing f between two adjacent protrusions 31 to meet 2mm≤f≤10mm.

[0128] In one possible implementation, the protrusion 31 is in the shape of a straight line, and the extension direction of the straight line is parallel to the width direction of the first pole piece 50, or the angle between the straight line and the width direction of the first pole piece 50 is an acute angle, for example, the angle between the extension direction of the straight line and the width direction of the first pole piece 50 is 2°, 5°, 8° or 10°, etc.

[0129] In one possible implementation, the protrusion 31 is curved, such as a wavy line, and the extension direction of the center line of the wavy line can be parallel to the width direction of the first pole piece 50, or the angle between the center line and the width direction of the first pole piece 50 is an acute angle.

[0130] In a possible implementation, the protrusion 31 is linear, the width e of the protrusion 31 satisfies 3mm≤e≤6mm, and the distance f between two adjacent protrusions 31 satisfies 3mm≤f≤7mm.

[0131] In a possible implementation, the width e of the protrusion 31 may be, for example, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 5.5 mm, 6 mm, 7 mm or 8 mm.

[0132] In a possible implementation, the distance f between two adjacent protrusions 31 may be, for example, 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, 5.5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm.

[0133] In one possible implementation, reference Fig. 9 and Fig.10 As shown, the first pole piece 50 also includes a single-sided coating area 11 with a first active material layer 20 on a single side, and an empty foil area 12 without a first active material layer 20 on both sides. Along the length direction of the first pole piece 50, the double-sided coating area 40, the single-sided coating area 11 and the empty foil area 12 are connected in sequence.

[0134] One end of the pole tab 80 may be welded in the pole tab groove 44 , and the other end of the pole tab 80 extends to the outside of the battery cell. The first active material layer 20 is not disposed in the pole tab groove 44 .

[0135] In the present invention, the first electrode sheet 50 may be a positive electrode sheet, wherein the first current collector 10 may be an aluminum foil, and the active material in the first active material layer 20 may include materials such as lithium cobalt oxide, lithium iron phosphate, and lithium manganese oxide.

[0136] In a possible implementation, the first electrode 50 is a positive electrode, and the second electrode 60 is a negative electrode. The separator 70 can prevent the positive electrode and the negative electrode from contacting and short-circuiting, and the separator 70 also has the function of allowing electrolyte ions in the electrolyte to pass through.

[0137] In one possible implementation, in the thickness direction of the battery cell, the concave-convex structure at least partially overlaps with the projection of the pole lug; since the thickness of the pole lug is relatively thick and the concave-convex structure of the first straight section has a strong deformation ability, when the two concave-convex structures 30 at least partially overlap with the projection of the pole lug 80 in the thickness direction of the battery cell, the thickness of the battery cell at the position of the pole lug 80 can be effectively reduced, the thickness consistency can be improved, and the energy density can be improved.

[0138] In one possible implementation, the diaphragm 70 may include a substrate and a coating layer, wherein the substrate may be a polyethylene (polythene, abbreviated as PE) single-layer film, a polypropylene (polypropylene, abbreviated as PP) single-layer film or a polypropylene-polyethylene-polypropylene three-layer composite film, and the coating layer may be at least one of porous silica, alumina, titanium dioxide and zirconium dioxide.

[0139] A battery cell provided by the present invention is a coil core, wherein the materials of the current collectors in the positive electrode sheet and the negative electrode sheet can be set according to actual needs, and no further limitation is made here. The second electrode sheet 60 is a negative electrode sheet, and the second electrode sheet 60 includes a second current collector and a second active material layer arranged on the surface of the second current collector, and the second current collector can be a copper foil. The active material in the second active material layer in the negative electrode sheet may include materials such as graphite, hard carbon, silicon, silicon oxide, or silicon carbon or silicon oxygen. The multiple grooves provided on the negative electrode sheet can effectively improve the wetting effect of the electrolyte on the negative electrode sheet. The multiple grooves provided on the negative electrode sheet can be achieved, for example, by laser wire drawing, negative electrode embossing or laser drilling. The types and proportions of active materials in the active material layers in the positive and negative electrode sheets can also be set according to actual needs, and no further limitation is made here.

[0140] The present invention also provides a battery, comprising the above-mentioned battery cell.

[0141] The battery provided by the embodiment of the present invention further includes a shell, the battery cell is located in the shell, and the electrolyte is injected into the shell so that the battery cell is immersed in the electrolyte.

[0142] In the battery provided by the embodiment of the present invention, the number of battery cells can be 1, 2, 3 or more, which is not specifically limited here.

[0143] A battery provided by the present invention may be a soft-pack battery or an aluminum shell battery.

[0144] In order to verify that the improvement of this application can effectively solve the problem that the electrode sheet is prone to slippage, resulting in poor coverage of the positive and negative electrode diaphragms, and even causing the electrode sheet to fold, so as to improve the cycle life and safety of the battery, the following experiments are conducted to verify. The following is the test data of the specific embodiment:

[0145] Embodiment 1

[0146] Preparation of positive electrode sheet: The first electrode sheet 50 is the positive electrode sheet. The positive electrode active material layer slurry is coated on the surface of the first current collector 10 by a coating machine. The first current collector 10 is an aluminum foil current collector to form a first active material layer 20. The first current collector 10 is an aluminum foil current collector to form an initial positive electrode sheet. The initial positive electrode sheet is cut according to actual needs. The concave-convex structure 30 is processed on the first straight section 41 of the cut positive electrode sheet to prepare the positive electrode sheet.

[0147] Preparation of negative electrode sheet: The second electrode sheet 60 is a negative electrode sheet. The negative electrode active material layer slurry is coated on the surface of the second current collector by a coating machine to form a second active material layer. The second current collector is copper foil. The second current collector is dried at 100°C to obtain an initial negative electrode sheet. The initial negative electrode sheet is cut according to actual needs to obtain a negative electrode sheet.

[0148] Assembling the battery cell: stack the positive electrode sheet, negative electrode sheet and separator 70 together, and then wind them to form a core, bake to remove moisture, inject electrolyte, adopt hot pressing process, stand and form to obtain the battery cell.

[0149] In the first embodiment, the protrusions 31 in the concavo-convex structure 30 are linear, the distance between the concavo-convex structure 30 and the edge of the first active material layer 20 is T1, and the width of the first active material layer 20 is T2, wherein T1=8 mm; T2=80 mm.

[0150] The ratio of the area S1 of the concave-convex structure 30 processed on the first straight section 41 of the positive electrode sheet to the area S2 of the first straight section 41 is S1 / S2=20%, the width e of the protrusion 31 is 1mm, the spacing f between two adjacent protrusions 31 is 4mm, the length L1 of the first straight section is 100mm, and the height H1 of the concave-convex structure 30 protruding from the first active material layer 20 is 2μm.

[0151] Embodiment 2

[0152] The difference between the second embodiment and the first embodiment is that the ratio S1 / S2 of the area S1 of the concave-convex structure 30 processed on the first straight section 41 of the positive electrode sheet to the area S2 of the first straight section 41 is 40%, the width e of the protrusion 31 is 5 mm, the height H1 of the concave-convex structure 30 protruding from the first active material layer 20 is 50 μm, and the other parameters of the battery cell are the same as those in the first embodiment.

[0153] Embodiment 3

[0154] The difference between the third embodiment and the first embodiment is that the ratio S1 / S2 of the area S1 of the concave-convex structure 30 processed on the first straight section 41 of the positive electrode sheet to the area S2 of the first straight section 41 is 60%, the width e of the protrusion 31 is 8 mm, the height H1 of the concave-convex structure 30 protruding from the first active material layer 20 is 80 μm, and the other parameters of the battery cell are the same as those in the first embodiment.

[0155] Embodiment 4

[0156] In the fourth embodiment, the protrusions 31 in the concavo-convex structure 30 are rhombus-shaped, the distance between the concavo-convex structure 30 and the edge of the first active material layer 20 is T1, and the width of the first active material layer 20 is T2, wherein T1=8 mm; T2=80 mm.

[0157] The ratio of the area S1 of the concave-convex structure 30 processed on the first straight section 41 of the positive electrode sheet to the area S2 of the first straight section 41 is S1 / S2=60%, the angle θ between two adjacent side edges in the rhombus is 60°, the side length a of the rhombus is 2.5 mm, the spacing b between two adjacent protrusions 31 is 1.2 mm, the length L1 of the first straight section is 100 mm, and the height H1 of the concave-convex structure 30 protruding from the first active material layer 20 is 20 μm.

[0158] Embodiment 5

[0159] The difference between the fifth embodiment and the fourth embodiment is that the ratio of the area S1 of the concavo-convex structure 30 processed on the first straight section 41 of the positive electrode sheet to the area S2 of the first straight section 41 is S1 / S2=40%, the side length a of the rhombus is 8 mm, the spacing b between two adjacent protrusions 31 is 3 mm; the length L1 of the first straight section is 100 mm, and the height H1 of the concavo-convex structure 30 protruding from the first active material layer 20 is 62 μm. The other parameters of the battery cell are the same as those of the fourth embodiment.

[0160] Embodiment 6

[0161] In the sixth embodiment, the protrusions 31 in the concavo-convex structure 30 are circular, the distance between the concavo-convex structure 30 and the edge of the first active material layer 20 is T1, and the width of the first active material layer 20 is T2, wherein T1=8 mm; T2=80 mm.

[0162] The ratio of the area S1 of the concavo-convex structure 30 processed on the first straight section 41 of the positive electrode sheet to the area S2 of the first straight section 41 is S1 / S2=40%, the diameter D of the circumscribed circle of the protrusion 31 is 0.3 mm, the distance c between the centers of the circumscribed circles of two adjacent protrusions 31 on the plane where the first electrode sheet 50 is located is 1 mm, the length L1 of the first straight section is 100 mm, and the height H1 of the concavo-convex structure 30 protruding from the first active material layer 20 is 30 μm. The remaining parameters of the battery cell are the same as those in Example 1.

[0163] Embodiment 7

[0164] The difference between the seventh embodiment and the sixth embodiment is that the ratio of the area S1 of the concavo-convex structure 30 processed on the first straight section 41 of the positive electrode sheet to the area S2 of the first straight section 41 is S1 / S2=60%, the diameter D of the circumscribed circle of the protrusion 31 is 5 mm, the distance c between the centers of the circumscribed circles of two adjacent protrusions 31 on the plane where the first electrode sheet 50 is located is 6 mm, the length L1 of the first straight section is 100 mm, and the height H1 of the concavo-convex structure 30 protruding from the first active material layer 20 is 60 μm. The remaining parameters of the battery cell are the same as those of the sixth embodiment.

[0165] Comparative Example 1:

[0166] In comparative example 1, the positive electrode sheet adopts the existing conventional positive electrode sheet, and the negative electrode sheet adopts the existing conventional negative electrode sheet, and batteries with the same specifications are prepared in the same way.

[0167] The test method is as follows:

[0168] 1. Capacity retention rate

[0169] The batteries obtained in the above embodiments and comparative examples were respectively charged at 25° C. with a constant current of 1.2C to 4.3V, charged at 0.7C to 4.45V, then charged at a constant voltage of 0.05C, left standing for 10 min, discharged at 0.5C to 3V, left standing for 10 min, discharged at 0.5C to 3V, left standing for 10 min, and cycled tested 800 times with this charge and discharge procedure to determine the initial capacity at the first cycle and the capacity after the cycle at the 800th cycle.

[0170] Capacity retention rate = initial capacity / capacity after cycle × 100%.

[0171] 2. Lithium deposition of battery cells

[0172] After the capacity retention rate test was performed on the batteries obtained in the above embodiment and the comparative example, the batteries obtained in the above embodiment and the comparative example were fully charged, and the batteries were disassembled in a dry room environment to observe the lithium deposition of the positive electrode sheet.

[0173] 3. Liquid retention detection

[0174] The liquid retention volume is the amount of electrolyte that is ultimately retained in the battery. In order to ensure the consumption of electrolyte during battery formation, a certain amount of electrolyte is usually injected. After formation, the excess electrolyte is extracted and measured by weighing. The liquid retention volume is the weight difference between the electrolyte injected into the battery and the excess electrolyte extracted.

[0175] The experimental results are shown in the following table:

[0176] Table 1

[0177]

[0178]

[0179] Table 2

[0180]

[0181] Table 3

[0182]

[0183] By comparing the test results, it can be learned that the present application provides a concave-convex structure 30 on the first electrode sheet 50, at least part of the concave-convex structure 30 is located in the first straight section 41, which can effectively solve the problem that the electrode sheet is prone to sliding, resulting in poor coverage of the positive and negative electrode diaphragms, and even causing the electrode sheet to fold and lithium deposition; at the same time, it can also effectively increase the liquid retention amount of the innermost layer of the battery cell, improve the problem of lithium deposition on the edge of the negative electrode sheet due to insufficient electrolyte in the innermost layer of the battery cell, thereby improving the cycle performance and safety of the battery cell.

[0184] It should be noted here that the numerical values ​​and numerical ranges involved in this application are approximate values. Due to the influence of the manufacturing process, there may be a certain range of errors, which can be considered negligible by those skilled in the art.

[0185] In the description of the present invention, it is necessary to understand that the terms used such as “center”, “length”, “width”, “thickness”, “top”, “bottom”, “up”, “down”, “left”, “right”, “front”, “back”, “vertical”, “horizontal”, “inside”, “outside”, “axial”, “circumferential”, etc. to indicate directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred position or component must have a specific direction, a specific structure and operation, and therefore cannot be understood as limiting the present invention.

[0186] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0187] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, they can be fixedly connected, detachably connected, or integrated; they can be mechanically connected, electrically connected, or can communicate with each other; they can be directly connected, or indirectly connected through an intermediate medium, so that the internal communication of two elements or the interaction relationship between two elements can be achieved. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0188] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0189] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery cell, characterized in that: It comprises a first pole piece (50), a second pole piece (60) and a diaphragm (70) which are stacked and wound, and the diaphragm (70) is arranged between the first pole piece (50) and the second pole piece (60); The first pole piece (50) comprises a first current collector (10) and a first active material layer (20) disposed on the first current collector (10); a pole tab groove (44) is provided in the first active material layer (20); the first current collector (10) is exposed from the pole tab groove (44); and a pole tab (80) is connected to the pole tab groove (44); The first pole piece (50) comprises a first straight section (41) located at the innermost circle of the battery cell, the first pole piece (50) is provided with a concave-convex structure (30), the concave-convex structure (30) comprises a plurality of protrusions (31) arranged at intervals and concave pits (311) arranged opposite to the protrusions (31), and at least part of the protrusions (31) and the concave pits (311) are located in the first straight section (41); The second pole piece (60) comprises a second current collector and a second active material layer disposed on the second current collector, the second active material layer is provided with a plurality of grooves, and the surface where the pit (311) of the first pole piece (50) is located and the surface where the grooves are located are arranged opposite to each other; The ratio of the area S1 of the concavo-convex structure (30) to the area S2 of the first straight section (41) is: 20%≤S1 / S2≤60%.

2. The battery cell according to claim 1, characterized in that: The first pole piece (50) includes a double-sided coating area (40) on both sides of the first current collector (10) provided with the first active material layer (20), the first straight section (41) is located in the double-sided coating area (40), and the protrusion (31) protrudes from the surface of the double-sided coating area (40).

3. The battery cell according to claim 1, characterized in that: At least part of the opening of the recess (311) faces the center of the battery core.

4. The battery cell according to claim 2, characterized in that: The height H1 of the concavo-convex structure (30) protruding from the first active material layer (20), the thickness H2 of the first active material layer (20) located in the double-sided coating area (40), and the thickness H3 of the first current collector (10) all satisfy the following conditions: 0.1×H2-0.8×H3≤H1≤0.8×H2-0.8×H3.

5. The battery cell according to claim 2, characterized in that: Along the length direction of the first pole piece (50): The length L1 of the first straight section (41) satisfies: 4mm≤L1≤100mm; and / or, The first straight section (41) has a first edge (411), and a distance L2 between the concave-convex structure (30) and the first edge (411) satisfies 1 mm ≤ L2 ≤ 5 mm.

6. The battery cell according to any one of claims 1 to 5, characterized in that: Along the width direction of the first pole piece (50): The distance between the concavo-convex structure (30) and the edge of the first active material layer (20) is T1, and the width of the first active material layer (20) is T2, wherein 5% T2≤T1≤45% T2.

7. The battery cell according to claim 5, characterized in that: The double-sided coating area (40) further comprises a first bent section (42) and a second straight section (43), and the first straight section (41), the first bent section (42) and the second straight section (43) are sequentially connected along the length direction of the first pole piece (50); The end of the concave-convex structure (30) away from the first edge (411) is a cut-off end (32), and the cut-off end (32) is located in the first straight section (41) or the first bent section (42) or the second straight section (43).

8. The battery cell according to claim 1, characterized in that: The protrusion (31) is rhombus-shaped; and / or, The angle θ between two adjacent sides of the rhombus satisfies 20°<θ<90°; and / or, The side length a of the rhombus satisfies 2mm≤a≤8mm; and / or, The distance b between two adjacent protrusions (31) satisfies 0.5 mm ≤ b ≤ 3 mm.

9. The battery cell according to claim 1, characterized in that: The protrusion (31) is circular, and the diameter D of the circumscribed circle of the protrusion (31) satisfies 0.3 mm ≤ D ≤ 8 mm, and / or the projections of two adjacent protrusions (31) on the plane where the first pole piece (50) is located do not overlap.

10. The battery cell according to claim 9, characterized in that: A distance c between the centers of the circumscribed circles of two adjacent protrusions (31) on the plane where the first pole piece (50) is located satisfies 1 mm ≤ c ≤ 6 mm.

11. The battery cell according to claim 1, characterized in that: The protrusion (31) is linear; The width e of the protrusion (31) satisfies 1mm≤e≤8mm; and / or, The spacing f between two adjacent protrusions (31) satisfies 2mm≤f≤10mm.

12. The battery cell according to claim 2, characterized in that: A height H1 of the concavo-convex structure (30) protruding from the first active material layer (20) satisfies: 2 μm≤H1≤80 μm.

13. The battery cell according to claim 2, characterized in that: The first pole piece (50) further comprises a single-sided coating area (11) on which the first active material layer (20) is provided on one side, and a hollow foil area (12) on which the first active material layer (20) is not provided on both sides, and along the length direction of the first pole piece (50), the double-sided coating area (40), the single-sided coating area (11) and the hollow foil area (12) are connected in sequence.

14. The battery cell according to claim 1, characterized in that: In the thickness direction of the battery core, the projections of the concave-convex structure (30) and the pole tab (80) at least partially overlap.

15. A battery, characterized in that: A battery cell comprising any one of claims 1 to 14.

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