Pattern positive pole piece of winding type square-shell battery cell, preparation method of pattern positive pole piece, winding type square-shell battery cell and secondary battery

Abstract

The invention relates to the technical field of secondary batteries, in particular to a patterned positive pole piece of a winding type square-shell battery cell, a preparation method of the patterned positive pole piece, the winding type square-shell battery cell and a secondary battery. Patterned surfaces are formed on a semicircle of an R angle of the winding type square-shell battery cell and a large surface of the winding type square-shell battery cell of the positive pole piece; and in the length direction of the positive pole piece, the width D2 of a pattern surface formed on the large surface of the winding type square shell battery cell by the positive pole piece is 3-50mm. According to the positive pole piece provided by the invention, the pattern surfaces are formed on the semicircle of the R angle of the winding type square-shell battery cell and the large surface of the winding type square-shell battery cell, and the width D2 of the pattern surface formed on the large surface of the winding type square-shell battery cell of the positive pole piece is 3-50mm, so that the cycle life of the lithium ion battery can be prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of secondary batteries, and in particular to a patterned positive electrode sheet of a wound square shell battery cell and a preparation method thereof, a wound square shell battery cell and a secondary battery. Background Art

[0002] In order to improve the consistency of the thickness of the positive electrode sheet and increase the expansion space of the battery cell in the wound structure lithium-ion battery, the positive electrode sheet is sometimes rolled using a patterned roller (P roller) during winding. The rolling pattern is added to increase the expansion space of the battery cell and improve the battery cell performance.

[0003] In the prior art, the P roller usually rolls the positive electrode sheet uniformly and fully. Although this method is simple in process and increases the expansion space of the entire battery cell as a whole, for the wound square shell battery cell, the concentrated force degree of each part of the core is actually different, especially the R corner where the force is the most serious. The battery cell obtained by the rolling method of the prior art will still start to fail first at the R corner during long-term use, resulting in a shorter cycle life of the lithium-ion battery.

[0004] Therefore, how to improve the cycle life of wound square-shell lithium-ion batteries is a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a patterned positive electrode sheet of a wound square shell battery cell, a preparation method thereof, a wound square shell battery cell and a secondary battery, wherein the positive electrode sheet is provided with a patterned surface on the semicircle of the R angle of the wound square shell battery cell and on the large surface of the wound square shell battery cell, and the width D2 of the patterned surface formed by the positive electrode sheet on the large surface of the wound square shell battery cell is 3 to 50 mm, thereby improving the cycle life of the lithium-ion battery.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a patterned positive electrode plate of a wound square shell battery cell, wherein the positive electrode plate has a patterned surface formed on the semicircle of the R angle of the wound square shell battery cell and on the large surface of the wound square shell battery cell, and in the length direction of the positive electrode plate, a width D2 of the patterned surface formed by the positive electrode plate on the large surface of the wound square shell battery cell is 3 to 50 mm.

[0008] The positive electrode plate provided by the present invention has a patterned surface formed on the semicircle of the R angle of the wound square shell battery cell and on the large surface of the wound square shell battery cell, and the width D2 of the patterned surface formed by the positive electrode plate on the large surface of the wound square shell battery cell is 3 to 50 mm, which can improve the cycle life of the lithium ion battery.

[0009] Furthermore, in the length direction of the positive electrode sheet, the width D3 of the pattern surface formed by different turns of the positive electrode sheet on the semicircle of the R angle of the wound square shell battery cell is the same;

[0010] And / or, in the length direction of the positive electrode sheet, the width D2 of the pattern surface formed by different turns of the positive electrode sheet on the large surface of the wound square shell battery cell is the same;

[0011] And / or, the R angle centers of different layers of the wound square shell battery core are in the same plane.

[0012] Furthermore, the wound square shell battery cell includes the patterned positive electrode sheet, the negative electrode sheet and the separator, and the distance from the center position of the R angle of the wound square shell battery cell to the top position of the semicircle of the R angle is D1, D1 = (a+b+c+d)*X*π / 2, wherein a is the thickness of the positive electrode sheet, b is the thickness of the negative electrode sheet, c is the thickness of the separator, d is the air gap value, and X is the number of winding turns.

[0013] Furthermore, the d is 0 to 20 μm and is not 0;

[0014] And / or, in the length direction of the positive electrode sheet, the width of the pattern surface formed by the positive electrode sheet on the semicircle of the R angle of the wound square shell battery cell is D3, and the D3 satisfies: in the first to third turns, 0≤D3≤D1; when the number of turns is not less than 4 turns, 0<D3≤D1;

[0015] And / or, the ratio of D3 to D1 in different circles is equal.

[0016] Furthermore, a full-coverage patterned surface is formed on the positive electrode sheet, and the full-coverage patterned surface fully covers the side of the positive electrode sheet where the patterned surface is formed on the semicircle of the R corner of the wound square shell battery cell and on the large surface of the wound square shell battery cell.

[0017] Furthermore, the shape of the pattern includes but is not limited to at least one of a circular hole, a triangle, and a square;

[0018] And / or, the pattern is in the shape of concave and evenly distributed circular holes, the diameter of the circular holes is 1-5 mm, and the depth is 1-15 μm.

[0019] In a second aspect, the present invention provides a method for preparing a patterned positive electrode sheet of a wound square shell battery cell as described in the first aspect, the preparation method comprising the following steps:

[0020] When the positive electrode sheet body is wound, the positive electrode sheet body is embossed on the semicircle of the R angle and the large surface of the wound square shell battery cell, so that a patterned surface is formed on the positive electrode sheet body.

[0021] Furthermore, after the embossing treatment, the patterned positive electrode plate is subjected to an additional embossing treatment as a whole to form the fully covered patterned surface;

[0022] and / or, using a P roller to perform embossing on the positive electrode plate body;

[0023] And / or, the positive electrode plate body includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is coated on the surface of the positive electrode current collector, wherein the active material of the positive electrode active material layer includes at least one of lithium iron phosphate, ternary material, lithium cobalt oxide, and lithium nickel oxide.

[0024] In a third aspect, the present invention provides a wound square shell battery cell, which comprises the patterned positive electrode sheet described in the first aspect, or the patterned positive electrode sheet prepared by the preparation method described in the second aspect.

[0025] In a fourth aspect, the present invention provides a secondary battery, wherein the secondary battery comprises the wound square shell battery cell described in the third aspect.

[0026] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0027] (1) The positive electrode plate provided by the present invention has a patterned surface formed on the semicircle of the R angle of the wound square shell battery cell and on the large surface of the wound square shell battery cell, and the width D2 of the patterned surface formed by the positive electrode plate on the large surface of the wound square shell battery cell is 3 to 50 mm, which can improve the cycle life of the lithium-ion battery.

[0028] (2) The positive electrode plate provided by the present invention can improve the problem of severe high local force on the top of the R corner of the wound square shell battery cell, thereby reducing the risk of expansion and deformation of the battery cell.

[0029] (3) The positive electrode plate provided by the present invention can improve the performance of the output battery, leave more space for the local positions that are easily subjected to stress, avoid the electrolyte from being squeezed out during the cycle, and improve the consistency and cycle performance of the battery.

[0030] (4) Combined with the conventional P-roll process, the range of the expandable space is increased, and different tension and expansion force requirements can be taken into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a schematic structural diagram of the patterned positive electrode sheet of the wound square shell battery cell provided by the present invention in an unfolded state;

[0033] Figure 2 It is a schematic structural diagram of the patterned positive electrode sheet of the wound square shell battery cell provided by the present invention in a wound state;

[0034] Figure 3 The capacity attenuation trend diagram of the lithium-ion battery prepared by the wound square shell battery cell provided in the embodiments of the present invention and the comparative example at 1C. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0036] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0037] First, as Figure 1 and Figure 2 As shown, the present invention provides a patterned positive electrode sheet of a wound square shell battery cell, wherein the positive electrode sheet is formed with a patterned surface on the semicircle of the R angle of the wound square shell battery cell and on the large surface of the wound square shell battery cell, and in the length direction of the positive electrode sheet, a width D2 of the patterned surface formed by the positive electrode sheet on the large surface of the wound square shell battery cell is 3 to 50 mm, for example, 3 mm, 10 mm, 20 mm, 30 mm, 40 mm or 50 mm.

[0038] Here, the surface with the largest area of ​​the wound square shell battery cell is defined as the battery cell large surface.

[0039] The positive electrode plate provided by the present invention forms a patterned surface on the semicircle of the R angle of the wound square shell battery cell and on the large surface of the wound square shell battery cell, and the width D2 of the patterned surface formed by the positive electrode plate on the large surface of the wound square shell battery cell is 3 to 50 mm, which can improve the problem of severe high local force on the top of the R angle of the wound battery cell, reduce the risk of expansion and deformation of the battery cell, and thus improve the cycle life of the lithium ion battery.

[0040] In the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional implementation, in the length direction of the positive electrode sheet, the width D3 of the patterned surface formed by different turns of the positive electrode sheet on the semicircle of the R angle of the wound square shell battery cell is the same.

[0041] In the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional implementation, in the length direction of the positive electrode sheet, the width D2 of the patterned surface formed by different turns of the positive electrode sheet on the large surface of the wound square shell battery cell is the same.

[0042] In the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional implementation, the center positions of the R angles of different layers of the wound square shell battery cell are in the same plane.

[0043] In the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional implementation, the wound square shell battery cell includes the patterned positive electrode sheet, the negative electrode sheet and the separator, and the distance from the center position of the R angle of the wound square shell battery cell to the top position of the semicircle of the R angle is D1, D1 = (a+b+c+d)*X*π / 2, wherein a is the thickness of the positive electrode sheet, b is the thickness of the negative electrode sheet, c is the thickness of the separator, d is the air gap value, and X is the number of winding turns.

[0044] In the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional implementation, the d is 0 to 20 μm and is not 0, for example, it can be 1 μm, 3 μm, 5 μm, 10 μm, 15 μm or 20 μm.

[0045] In the patterned positive electrode plate of the above-mentioned wound square shell battery cell, as an optional implementation mode, in the length direction of the positive electrode plate, the width of the patterned surface formed by the positive electrode plate on the semicircle of the R angle of the wound square shell battery cell is D3, and the D3 satisfies: in the first to third turns, 0≤D3≤D1; when the number of turns is not less than 4 turns, 0<D3≤D1, that is, in the first three turns (including the third turn), 0≤D3≤D1, and starting from the fourth turn, 0<D3≤D1.

[0046] In the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional implementation, the ratio of the D3 to the D1 in different turns is equal.

[0047] In the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional embodiment, a fully covered patterned surface is also formed on the positive electrode sheet, and the fully covered patterned surface fully covers the positive electrode sheet on the semicircle of the R angle of the wound square shell battery cell and the side of the patterned surface formed on the large surface of the wound square shell battery cell. It is equivalent to using a P roller to roll the pattern at a local key position, and then rolling the entire electrode sheet with a P roller to ensure that there is more expansion space at the R angle position. The embodiment of the present invention can not only provide sufficient expansion space for the entire core, but also ensure that the local force problem is solved.

[0048] In the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional implementation, the shape of the pattern includes but is not limited to at least one of a circular hole shape, a triangle shape, and a square shape.

[0049] In the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional embodiment, the shape of the pattern is a concave, evenly distributed circular hole shape, the diameter of the circular hole is 1-5mm (for example, it can be 1mm, 2mm, 3mm, 4mm, 5mm), and the depth is 1-15μm (for example, it can be 1μm, 3μm, 5μm, 7μm, 11μm, 13μm or 15μm).

[0050] In a second aspect, the present invention provides a method for preparing a patterned positive electrode sheet of a wound square shell battery cell as described in the first aspect, the preparation method comprising the following steps:

[0051] When the positive electrode sheet body is wound, the positive electrode sheet body is embossed on the semicircle of the R angle and the large surface of the wound square shell battery cell, so that a patterned surface is formed on the positive electrode sheet body.

[0052] In the method for preparing the patterned positive electrode sheet of the above-mentioned wound square shell battery cell, as an optional implementation, after the embossing treatment, the patterned positive electrode sheet is subjected to an additional embossing treatment as a whole to form the fully covered patterned surface.

[0053] In the above-mentioned method for preparing the positive electrode sheet, as an optional implementation, a P roller is used to perform embossing treatment on the positive electrode sheet body.

[0054] In the above-mentioned method for preparing the positive electrode sheet, as an optional implementation, the positive electrode sheet body includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is coated on the surface of the positive electrode current collector.

[0055] In the above-mentioned method for preparing the positive electrode plate, as an optional implementation, the active material of the positive electrode active material layer includes at least one of lithium iron phosphate, ternary material, lithium cobalt oxide, and lithium nickel oxide.

[0056] Here, the preparation method of the positive electrode sheet body is a conventional preparation method, specifically: the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and the positive electrode sheet body is obtained after baking, cold pressing and cutting.

[0057] In a third aspect, the present invention provides a wound square shell battery cell, which comprises the patterned positive electrode sheet described in the first aspect, or the patterned positive electrode sheet prepared by the preparation method described in the second aspect.

[0058] In the above-mentioned wound square shell battery cell, as an optional implementation, the wound square shell battery cell also includes a negative electrode sheet and a separator, and the wound square shell battery cell is made by winding the positive electrode sheet, the negative electrode sheet and the separator.

[0059] In the above-mentioned wound square shell battery cell, as an optional implementation manner, the center positions of R angles of different layers of the wound square shell battery cell are in the same plane.

[0060] In the above-mentioned wound square shell battery cell, as an optional implementation manner, the distance from the center position of the R angle of the wound square shell battery cell to the top position of the semicircle of the R angle is D1, D1 = (a+b+c+d)*X*π / 2, wherein a is the thickness of the positive electrode sheet, b is the thickness of the negative electrode sheet, c is the thickness of the diaphragm, d is the air gap value, and X is the number of winding turns.

[0061] In the above-mentioned wound square shell battery cell, as an optional implementation, the d is 0 to 20 μm, for example, it can be 1 μm, 3 μm, 5 μm, 10 μm, 15 μm or 20 μm.

[0062] In a fourth aspect, the present invention provides a secondary battery, wherein the secondary battery comprises the wound square shell battery cell described in the third aspect.

[0063] Specifically, the battery may be a lithium-ion battery.

[0064] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0065] The active material of the positive electrode plate is lithium iron phosphate, the active material of the negative electrode plate is graphite, and the separator is 9μm PE+2μm PVDF+2μm Al2O3.

[0066] The distance from the center position of the R angle of the wound square shell battery cell to the top position of the semicircle of the R angle is D1, D1 = (a+b+c+d)*X*π / 2, wherein a is the thickness of the positive electrode sheet, b is the thickness of the negative electrode sheet, c is the thickness of the diaphragm, d is the air gap value, X is the number of winding turns, and d is 0 to 20 μm and is not 0.

[0067] Example 1

[0068] This embodiment provides a wound square shell battery cell, the wound square shell battery cell includes a patterned positive electrode sheet, a negative electrode sheet and a separator, the patterned positive electrode sheet is formed with a patterned surface on the semicircle of the R angle of the wound square shell battery cell and on the large surface of the wound square shell battery cell, the wound square shell battery cell has two large surfaces, and the shape of the pattern is a circular pit with a diameter of 2mm and a depth of 8μm. In the length direction of the patterned positive electrode sheet, the width of the patterned surface formed by the positive electrode sheet on the large surface of the wound square shell battery cell is D2, and the width of the patterned surface formed by the patterned positive electrode sheet on the semicircle of the R angle of the wound square shell battery cell is D3, and the D3 of different circles is 5mm (especially when the inner circle D1 area is less than 5mm, D3=D1), and the D2 of different circles is 30mm. The patterned positive electrode sheet is wound around the winding center axis 30 times, with a total of 60 layers. The width of the wound square shell battery cell (generally refers to the maximum width in the industry, including the R corner, that is, the center distance between the R corners at both ends) is 210 mm, and the thickness of the wound square shell battery cell is 20 mm. The center positions of the R corners of different layers are in the same plane.

[0069] The method for preparing a wound square shell battery cell provided in this embodiment comprises the following steps: preparing the wound square shell battery cell by winding the negative electrode sheet, the patterned positive electrode sheet and the separator, wherein the method for preparing the patterned positive electrode sheet comprises: when winding the positive electrode sheet body, Figure 1 The positive electrode sheet body is embossed on the semicircle of the R angle of the wound square shell battery cell and on the large surface of the battery cell using a P roller (the shaded area is the P roller rolling area), so that a patterned surface is formed on the positive electrode sheet body, and the pressure of the P roller is 0.3 MPa. The positive electrode sheet body includes an aluminum foil and a positive active material layer, and the positive active material layer is coated on the surface of the aluminum foil.

[0070] Example 2

[0071] The wound square shell battery cell provided in this embodiment is basically the same as that in Embodiment 1, except that a full-coverage patterned surface is also formed on the patterned positive electrode plate, and the full-coverage patterned surface fully covers the side of the positive electrode plate on which the patterned surface is formed on the semicircle of the R corner of the wound square shell battery cell and on the large surface of the wound square shell battery cell.

[0072] The preparation method of the wound square shell battery cell provided in this embodiment is basically the same as that of Example 1, except that, in the preparation process of the patterned positive electrode plate, after the positive electrode plate body on the semicircle of the R angle of the wound square shell battery cell and the large surface of the battery cell is embossed with a P roller, the patterned positive electrode plate as a whole is subjected to an additional P roller rolling to form the fully covered patterned surface. The design pressure of the P roller is 0.3Mpa, and the circular pits formed by rolling have a diameter of 2mm and a depth of 8μm.

[0073] Example 3

[0074] The wound square shell battery cell provided in this embodiment is basically the same as that in Embodiment 1, except that the ratio of the D3 to the D1 in different turns is 1:3.

[0075] The wound square shell battery cell provided in this embodiment is prepared by referring to the preparation method of the wound square shell battery cell provided in Example 1.

[0076] Example 4

[0077] The wound square shell battery cell provided in this embodiment is basically the same as that in Embodiment 1, except that the ratio of the D3 to the D1 in different turns is 1:1.

[0078] The wound square shell battery cell provided in this embodiment is prepared by referring to the preparation method of the wound square shell battery cell provided in Example 1.

[0079] Example 5

[0080] The wound square shell battery cell provided in this embodiment is basically the same as that in Embodiment 1, except that D2 is 10 mm.

[0081] The wound square shell battery cell provided in this embodiment is prepared by referring to the preparation method of the wound square shell battery cell provided in Example 1.

[0082] Example 6

[0083] The wound square shell battery cell provided in this embodiment is basically the same as that in Embodiment 1, except that D2 is 50 mm.

[0084] The wound square shell battery cell provided in this embodiment is prepared by referring to the preparation method of the wound square shell battery cell provided in Example 1.

[0085] Comparative Example 1

[0086] The present comparative example provides a method for preparing a wound square shell battery cell, which comprises the following steps: preparing a negative electrode sheet, a patterned positive electrode sheet and a separator into the wound square shell battery cell by winding, wherein the method for preparing the patterned positive electrode sheet comprises: when winding the positive electrode sheet body, embossing the positive electrode sheet body as a whole with a P roller in accordance with the conventional method in the industry, so that a patterned surface is formed on the positive electrode sheet body, the pressure of the P roller is 0.3Mpa, the positive electrode sheet body comprises an aluminum foil and a positive electrode active material layer, the positive electrode active material layer is coated on the surface of the aluminum foil, the shape of the pattern is a circular pit with a diameter of 2mm and a depth of 8μm, the number of turns of the patterned positive electrode sheet around the winding center axis is 30, with a total of 60 layers, the width of the wound square shell battery cell is 210mm, the thickness of the wound square shell battery cell is 20mm, and the center positions of the R angles of different layers are in the same plane.

[0087] Comparative Example 2

[0088] The wound square shell battery cell provided in this embodiment is basically the same as that in Embodiment 1, except that D2 is 80 mm.

[0089] The wound square shell battery cell provided in this embodiment is prepared by referring to the preparation method of the wound square shell battery cell provided in Example 1.

[0090] Performance Testing

[0091] The wound square shell cells provided in the embodiment and the comparative example were respectively assembled into lithium ion batteries according to conventional methods, and then the cycle performance of the lithium ion batteries was tested. The test process is as follows:

[0092] 1) Place in a 45℃ constant temperature box for 5 hours to reach thermal equilibrium;

[0093] 2) 1C constant current and constant voltage charging to 3.65V, cut-off current 0.05C (1C = 1 times the rated capacity current);

[0094] 3) Let stand for 60 minutes;

[0095] 4) 1C constant current discharge to 2.5V;

[0096] 5) standing for 60 minutes; 6) repeating steps 2)-5) until the 1C capacity retention rate is less than 80%.

[0097] Draw a capacity decay trend graph based on the relationship between the number of cycles and the 1C capacity retention rate, such as Figure 3 shown.

[0098] Depend on Figure 3 At least the following points can be seen:

[0099] (1) The comparison results of the above embodiment and comparative example 1 show that the present invention can significantly improve the lithium plating and cycle water diving caused by excessive expansion force at the local position of the R corner in the late cycle, and has a significant effect on improving the cycle life and safety performance of the wound square shell battery cell.

[0100] (2) By comparing Example 1 with Comparative Examples 1-2, it can be seen that if D2 is too large, it is impossible to improve the lithium deposition and cycle water drop caused by excessive expansion force at the local position of the R corner in the late cycle.

[0101] 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 patterned positive electrode sheet for a wound square shell battery cell, characterized in that: The positive electrode sheet is formed with a patterned surface on the semicircle of the R angle of the wound square shell battery cell and on the large surface of the wound square shell battery cell. In the length direction of the positive electrode sheet, the width D2 of the patterned surface formed by the positive electrode sheet on the large surface of the wound square shell battery cell is 3 to 50 mm.

2. The patterned positive electrode sheet of the wound square shell battery cell according to claim 1, characterized in that: In the length direction of the positive electrode sheet, the width D3 of the pattern surface formed by different turns of the positive electrode sheet on the semicircle of the R angle of the wound square shell battery cell is the same; And / or, in the length direction of the positive electrode sheet, the width D2 of the pattern surface formed by different turns of the positive electrode sheet on the large surface of the wound square shell battery cell is the same; And / or, the R angle centers of different layers of the wound square shell battery core are in the same plane.

3. The patterned positive electrode sheet of the wound square shell battery cell according to claim 1, characterized in that: The wound square shell battery cell includes the patterned positive electrode sheet, the negative electrode sheet and the separator. The distance from the center position of the R angle of the wound square shell battery cell to the top position of the semicircle of the R angle is D1, D1=(a+b+c+d)*X*π / 2, wherein a is the thickness of the positive electrode sheet, b is the thickness of the negative electrode sheet, c is the thickness of the separator, d is the air gap value, and X is the number of winding turns.

4. The patterned positive electrode sheet of the wound square shell battery cell according to claim 3, characterized in that: The d is 0 to 20 μm and is not 0; And / or, in the length direction of the positive electrode sheet, the width of the pattern surface formed by the positive electrode sheet on the semicircle of the R angle of the wound square shell battery cell is D3, and the D3 satisfies: in the first to third turns, 0≤D3≤D1; when the number of turns is not less than 4 turns, 0<D3≤D1; And / or, the ratio of D3 to D1 in different circles is equal.

5. The patterned positive electrode sheet of the wound square shell battery cell according to claim 1, characterized in that: The positive electrode sheet is also provided with a fully covered patterned surface, and the fully covered patterned surface fully covers the positive electrode sheet on the semicircle of the R corner of the wound square shell battery cell and on the large surface of the wound square shell battery cell.

6. The patterned positive electrode sheet of the wound square shell battery cell according to claim 1, characterized in that: The shape of the pattern is not limited to at least one of a circular hole, a triangle, and a square; And / or, the pattern is in the shape of concave and evenly distributed circular holes, the diameter of the circular holes is 1-5 mm, and the depth is 1-15 μm.

7. A method for preparing a patterned positive electrode sheet of a wound square shell battery cell as claimed in any one of claims 1 to 6, characterized in that: The preparation method The following steps are involved: When the positive electrode sheet body is wound, the positive electrode sheet body is embossed on the semicircle of the R angle and the large surface of the wound square shell battery cell, so that a patterned surface is formed on the positive electrode sheet body.

8. The method for preparing the patterned positive electrode sheet of the wound square shell battery cell according to claim 7, characterized in that: After the embossing treatment, an additional embossing treatment is performed on the entire patterned positive electrode plate to form the fully covered patterned surface; and / or, using a P roller to perform embossing on the positive electrode plate body; And / or, the positive electrode plate body includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is coated on the surface of the positive electrode current collector, wherein the active material of the positive electrode active material layer includes at least one of lithium iron phosphate, ternary material, lithium cobalt oxide, and lithium nickel oxide.

9. A wound square shell battery cell, characterized in that: The wound square shell battery cell comprises the patterned positive electrode sheet according to any one of claims 1 to 6, or the patterned positive electrode sheet prepared by the preparation method according to claim 7 or 8. 10 . A secondary battery, comprising the wound square-shell battery cell according to claim 9 .

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