An electrode assembly and its preparation method, and a battery

Abstract

This invention provides an electrode assembly and its preparation method, as well as a battery, including a positive electrode, a negative electrode, and a separator. The positive electrode includes a positive current collector and a positive active material layer. The positive active material layer includes a first region and a second region. The first region is located on the inner winding of the positive electrode, and the second region is located on the outer winding of the positive electrode. The first region of the positive active material layer has multiple etching lines. The second region of the positive electrode has multiple embossing patterns. In this invention, etching is performed in the first region, and the grooves of the etching lines can increase the electrolyte retention capacity, while also increasing the N / P value of the core and the CB value of the arc region, thus preventing lithium plating on the electrode. Embossing is performed in the second region, which can effectively improve the thickness and density of the positive active material layer of the positive electrode. Embossing can improve the specific capacity of the positive electrode under high surface density, store more electrolyte, increase more contact area and lithium removal channels, effectively improve the discharge capability and dynamic performance, and improve the battery's first-time efficiency.

Description

Technical Field

[0001] This invention relates to the field of high energy density battery technology, specifically to an electrode assembly and its preparation method, and a battery. Background Technology

[0002] With increasing consumer demand for energy density, silicon-carbon materials are currently the mainstream development material. However, the design and development of high energy density requires higher silicon doping levels and greater areal density in the cathode coating. Higher areal density means thicker electrode sheets, which increases lithium-ion charge transfer resistance, increases lithium-ion transport paths, and significantly deteriorates system kinetics. During fast charging tests, fast charging can cause localized potential imbalances and lithium enrichment, leading to lithium plating. Therefore, it is necessary to reduce the polarization of high-energy-density cells in fast charging modes, requiring improvements in cathode kinetics. Simultaneously, the liquid retention capacity of the cathode in high-energy-density systems has consistently been low, causing rapid degradation over long cycles. The liquid retention performance of the cell also needs improvement. Therefore, overcoming these technical problems and defects has become a key issue that needs to be addressed. Summary of the Invention

[0003] To address the problems of increased lithium-ion charge transfer resistance, significant deterioration of system kinetics, lithium plating due to local potential imbalance, and low liquid retention capacity in the positive electrode of current high-energy-density batteries, this invention provides an electrode assembly, its preparation method, and a battery.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0005] The first aspect of the present invention provides an electrode assembly, including a positive electrode, a negative electrode, and a separator, wherein the positive electrode, the separator, and the negative electrode are stacked and wound to form the electrode assembly;

[0006] The positive electrode sheet includes a positive current collector and a positive active material layer coated on at least one side of the surface of the positive current collector, wherein the one-sided density of the positive active material layer is 120 g / m². 2 ~300g / m 2 ;

[0007] The positive electrode active material layer includes a first region and a second region. The first region is located in the inner winding of the positive electrode sheet, and the second region is located in the outer winding of the positive electrode sheet. Along the thickness direction of the positive electrode sheet, the first region of the positive electrode active material layer is provided with multiple etching lines, and the second region of the positive electrode sheet is provided with multiple embossing patterns.

[0008] Optionally, the number of folds in the first region is 1 / 4 to 1 / 2 of the total number of folds in the positive electrode winding.

[0009] Optionally, the total volume of the etched regions of all the etched lines is 1%-2% of the volume of the positive electrode active material layer.

[0010] Optionally, the depth of the etching line is 25% to 40% of the thickness of the positive electrode active material layer; the spacing between two adjacent etching lines is 0.5 mm to 1.5 mm; and the width of the etching line is 60 μm to 105 μm.

[0011] Optionally, the depth of the etching line is 30% to 35% of the thickness of the positive electrode active material layer; the spacing between two adjacent etching lines is 0.8 mm to 1.2 mm; and the width of the etching line is 75 μm to 90 μm.

[0012] Optionally, the number of folds in the second region is 1 / 2 to 3 / 4 of the total number of folds in the positive electrode winding.

[0013] Optionally, the total volume of all the embossed regions is 1.5%-7% of the volume of the positive electrode active material layer.

[0014] Optionally, the area of ​​the embossed pattern accounts for 10% to 50% of the area of ​​the second region.

[0015] Optionally, along the direction parallel to the thickness of the positive electrode sheet, the depth of the embossing is 2%-10% of the thickness of the positive electrode active material layer.

[0016] Optionally, the single-sided density of the positive electrode active material layer is 200 g / m². 2 ~300g / m 2 ;

[0017] The negative electrode precursor includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material and CMC;

[0018] The negative electrode precursor is subjected to high-temperature treatment to obtain the negative electrode, thereby carbonizing the CMC in the negative electrode active material layer to form conductive carbon black.

[0019] Optionally, the high-temperature treatment temperature of the negative electrode precursor is 200℃~300℃, and the high-temperature treatment time of the negative electrode precursor is 3-7h.

[0020] Optionally, the negative electrode active material includes silicon-carbon material, wherein the silicon content accounts for 3-15% of the mass of the silicon-carbon material.

[0021] A second aspect of the present invention provides a method for preparing an electrode assembly, comprising the following steps:

[0022] S1. Obtain the positive electrode, negative electrode, and separator;

[0023] S2. Etch multiple etching lines in the first region of the positive electrode active material layer of the positive electrode sheet, and press embossing in the second region of the positive electrode active material layer of the positive electrode sheet;

[0024] S3. The positive electrode, the separator, and the negative electrode are sequentially stacked and wound to form an electrode assembly, such that the first region is located in the inner winding of the positive electrode and the second region is located in the outer winding of the positive electrode.

[0025] A third aspect of the present invention provides a battery, including a battery casing, an electrolyte, and an electrode assembly as described above, or an electrode assembly prepared by the method described above for preparing the electrode assembly.

[0026] According to the electrode assembly provided by the present invention, by etching and scribing the first region of the positive electrode active material layer of the inner ring of the core, the grooves of the etched lines can increase the electrolyte retention and increase the N / P value of the core, compensating for the N / P value loss of the inner ring of the core. At the same time, it can significantly increase the CB value of the arc region of the positive electrode sheet, avoiding lithium plating problems caused by low CB value of the electrode sheet. Moreover, the increased electrolyte retention by the grooves of the etched lines can improve the lithium plating problem in the arc region of the core. By embossing the second region of the positive electrode active material layer of the outer ring of the core, embossing can effectively improve the thickness and density of the positive electrode active material layer of the positive electrode sheet. Embossing can improve the specific capacity of the positive electrode under high area density. Embossing can store more electrolyte, increase more contact area, increase delithiation channels, effectively improve the discharge capability and dynamic performance of the core, and improve the first efficiency of the battery. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic cross-sectional view of a positive electrode sheet provided in an embodiment of the present invention;

[0029] Figure 2 This is a top view schematic diagram of a positive electrode sheet provided in an embodiment of the present invention;

[0030] Figure 3 This is a schematic cross-sectional view of the negative electrode precursor provided in an embodiment of the present invention;

[0031] Figure 4 This is a cross-sectional schematic diagram of a negative electrode sheet provided in an embodiment of the present invention;

[0032] Figure 5 This is a cross-sectional schematic diagram of an electrode assembly provided in an embodiment of the present invention;

[0033] The reference numerals in the accompanying drawings are as follows:

[0034] 100-Electrode assembly; 1-Positive electrode sheet; 11-Positive current collector; 12-Positive active material layer; 121-First region; 1211-Etching line; 122-Second region; 1221-Embossing; 2-Negative electrode sheet; 21-Negative current collector; 22-Negative active material layer; 221-CMC; 3-Separator. Detailed Implementation

[0035] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] To make the technical problems solved, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0040] like Figures 1-2 As shown, in one embodiment, the first aspect of the present invention provides an electrode assembly 100, including a positive electrode 1, a negative electrode 2 and a separator 3, wherein the positive electrode 1, the separator 3 and the negative electrode 2 are stacked and wound to form the electrode assembly 100;

[0041] The positive electrode 1 includes a positive current collector 11 and a positive active material layer 12 coated on at least one side of the surface of the positive current collector 11, wherein the one-sided density of the positive active material layer 12 is 120 g / m². 2 ~300g / m 2 ;

[0042] The positive electrode active material layer 12 includes a first region 121 and a second region 122. The first region 121 is located in the inner winding of the positive electrode sheet 1, and the second region 122 is located in the outer winding of the positive electrode sheet 1. Along the thickness direction parallel to the positive electrode sheet 1, the first region 121 of the positive electrode active material layer 12 is provided with multiple etching lines 1211; the second region 122 of the positive electrode sheet 1 is provided with multiple embossing patterns 1221.

[0043] In conventional wound cores, the current density in the inner ring of the core is relatively high, resulting in greater polarization. At the same time, the winding tension in the inner ring is also relatively high, which can easily lead to a low N / P value. Furthermore, the curvature of the arc region of the positive electrode 1 is large, causing the CB value to be low at this time.

[0044] In one embodiment, the present invention performs etching and scribing on the first region 121 of the positive electrode active material layer 12 of the inner ring of the core. The grooves of the etching lines 1211 can increase the liquid retention and increase the N / P value of the core, compensating for the N / P value loss of the inner ring of the core. At the same time, it can significantly increase the CB value of the arc region of the positive electrode 1, avoiding lithium plating problems caused by low CB value of the electrode. Moreover, the increased liquid retention by the grooves of the etching lines 1211 can improve the lithium plating problem in the arc region of the core.

[0045] Furthermore, the length of the etching line 1211 is the same as the width of the first region 121, or the length of the etching line 1211 is slightly smaller than the width of the first region 121, thereby facilitating an increase in the liquid retention capacity of the groove of the etching line 1211.

[0046] In one embodiment, the present invention performs embossing 1221 on the second region 122 of the positive active material layer 12 on the outer ring of the core. Embossing 1221 can effectively improve the thickness and density of the positive active material layer 12 of the positive electrode sheet 1. Embossing 1221 can improve the specific capacity of the positive electrode under large area density. Embossing 1221 can store more electrolyte, increase more contact area, increase delithiation channels, effectively improve the multiple discharge capability and dynamic performance of the core, and improve the first efficiency of the battery.

[0047] Specifically, the embossing 1221 is formed by rolling an embossing roller on the second region 122 of the positive electrode active material layer 12. The shape of the embossing 1221 is any one of the following: circular, square, rhomboid, triangular, hexagonal, trapezoidal or elliptical; in a preferred embodiment, the shape of the embossing 1221 is circular.

[0048] like Figures 1-2 As shown, in one embodiment, the number of folds in the first region 121 is 1 / 4 to 1 / 2 of the total number of folds in the positive electrode 1.

[0049] Specifically, the number of folds in the first region 121 is any one of the following values, or any two of the following values, which are 1 / 4, 3 / 10, 7 / 20, 2 / 5, 9 / 20 or 1 / 2 of the total number of folds in the positive electrode 1: in a preferred embodiment, the number of folds in the first region 121 is 3 / 10 to 9 / 20 of the total number of folds in the positive electrode 1.

[0050] When the number of folds in the first region 121 is 1 / 4 to 1 / 2 of the total number of folds in the positive electrode 1, the high capacity of the core can be maintained while taking into account the long cycle performance of the core, which can effectively improve the lithium plating problem in the arc region of the positive electrode 1. When the number of folds in the first region 121 is less than 1 / 4 of the total number of folds in the positive electrode 1, the CB value of the arc region of the positive electrode 1 does not change significantly, and the improvement of lithium plating in the arc region is not significant. When the number of folds in the first region 121 is greater than 1 / 2 of the total number of folds in the positive electrode 1, it will cause the CB value of the arc region of the positive electrode 1 to be too large, resulting in a large loss of core capacity.

[0051] like Figures 1-2 As shown, in one embodiment, the total volume of the etched regions of all etch lines 1211 is 1%-2% of the volume of the positive electrode active material layer 12.

[0052] Specifically, the total volume of the etched regions of all etch lines 1211 is a value within a range of any one of the following percentages of the volume of the positive electrode active material layer 12: 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%. In a preferred embodiment, the total volume of the etched regions of all etch lines 1211 is 1.2%-1.8% of the volume of the positive electrode active material layer 12.

[0053] Specifically, when the total volume of the etched areas of all etched lines 1211 is 1%-2% of the volume of the positive electrode active material layer 12, the high capacity of the core can be maintained while taking into account the long cycle performance of the core, which can effectively improve the lithium plating problem in the arc region of the positive electrode sheet 1; when the total volume of the etched areas of all etched lines 1211 is less than 1% of the volume of the positive electrode active material layer 12, the CB value of the arc region of the positive electrode sheet 1 does not change significantly, and the improvement of lithium plating in the arc region is not significant; when the total volume of the etched areas of all etched lines 1211 is greater than 2% of the volume of the positive electrode active material layer 12, it will cause the CB value of the arc region of the positive electrode sheet 1 to be too large, resulting in a large loss of core capacity.

[0054] like Figures 1-2 As shown, in one embodiment, the depth of the etching line 1211 is 25% to 40% of the thickness of the positive electrode active material layer 12; the spacing between two adjacent etching lines 1211 is 0.5 mm to 1.5 mm; and the width of the etching line 1211 is 60 μm to 105 μm.

[0055] Specifically, the depth of all etched lines 1211 is any one of the following values ​​or any two of the following values: 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40% of the thickness of the positive electrode active material layer 12.

[0056] Specifically, when the depth of the etching line 1211 is 25% to 40% of the thickness of the positive electrode active material layer 12, it can maintain the high capacity of the core while taking into account the long cycle performance of the core, and can effectively improve the lithium plating problem in the arc area of ​​the positive electrode sheet 1; when the depth of the etching line 1211 is less than 25% of the thickness of the positive electrode active material layer 12, the current density of the inner ring of the core is too large, the polarization is large, and the winding tension of the inner ring of the core is too large, which can easily cause the core N / P value to be low; when the depth of the etching line 1211 is greater than 40% of the thickness of the positive electrode active material layer 12, the core N / P value increases, but it will lead to the deterioration of the high temperature performance of the core, and the capacity loss of the core is obvious.

[0057] Specifically, the spacing between two adjacent etching lines 1211 is any one value or any two values ​​from 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm or 1.5mm.

[0058] Specifically, when the spacing between two adjacent etching lines 1211 is 0.5mm to 1.5mm, the high capacity of the core can be maintained while taking into account its long cycle performance, effectively improving the lithium plating problem in the negative electrode arc region corresponding to the positive electrode sheet 1. When the spacing between two adjacent etching lines 1211 is less than 0.5mm, the N / P value of the core increases, but this leads to a deterioration in the high-temperature performance of the core, and a significant loss in the core's capacity. When the spacing between two adjacent etching lines 1211 is greater than 1.5mm, the N / P value of the inner core changes less, and the improvement on the negative electrode arc region corresponding to the positive electrode sheet 1 is not significant, while also resulting in a loss of capacity.

[0059] Specifically, the width of the etching line 1211 is any one value or any two values ​​from 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm or 105μm.

[0060] Specifically, when the width of the etching line 1211 is 60μm~105μm, it can maintain the high capacity of the core while taking into account the long cycle performance of the core, and can effectively improve the lithium plating problem in the arc region of the positive electrode 1. When the width of the etching line 1211 is less than 60μm, the CB value of the arc region of the negative electrode corresponding to the positive electrode 1 does not change significantly, and the improvement of lithium plating in the arc region is not significant. When the width of the etching line 1211 is greater than 105μm, it will cause the CB value of the arc region of the negative electrode corresponding to the positive electrode 1 to be too large, resulting in a large loss of core capacity and a deterioration of high-temperature cycle retention.

[0061] like Figures 1-2 As shown, in a preferred embodiment, the depth of the etching line 1211 is 30% to 35% of the thickness of the positive electrode active material layer 12; the spacing between two adjacent etching lines 1211 is 0.8 mm to 1.2 mm; and the width of the etching line 1211 is 75 μm to 90 μm.

[0062] like Figures 1-2 As shown, in one embodiment, the number of folds in the second region 122 is 1 / 2 to 3 / 4 of the total number of folds in the positive electrode 1.

[0063] Specifically, the number of folds in the second region 122 is any one of the following values, or a range of any two values, which is 1 / 2, 11 / 20, 3 / 5, 13 / 20, 7 / 10, or 3 / 4 of the total number of folds in the positive electrode 1; in a preferred embodiment, the number of folds in the second region 122 is 11 / 20-7 / 10 of the total number of folds in the positive electrode 1.

[0064] When the number of folds in the second region 122 is 1 / 2 to 3 / 4 of the total number of folds in the positive electrode 1, the high capacity of the core can be maintained while taking into account the long cycle performance of the core, which can effectively improve the lithium plating problem in the arc region of the positive electrode 1. When the number of folds in the second region 122 is less than 1 / 2 of the total number of folds in the positive electrode 1, the CB value in the arc region of the positive electrode 1 will be too large, resulting in a large loss of core capacity. When the number of folds in the second region 122 is greater than 3 / 4 of the total number of folds in the positive electrode 1, the CB value in the arc region of the positive electrode 1 does not change significantly, and the improvement of lithium plating in the arc region is not significant.

[0065] like Figures 1-2 As shown, in one embodiment, the total volume of all embossed regions 1221 is 1.5%-7% of the volume of the positive electrode active material layer 12.

[0066] Specifically, the total volume of all embossed regions 1221 is any one of the following values, or a range of any two values, representing 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or 7% of the volume of the positive electrode active material layer 12; in a preferred embodiment, the total volume of all embossed regions 1221 is 3%-5% of the volume of the positive electrode active material layer 12.

[0067] Specifically, when the total volume of all embossed areas 1221 is 1.5%-7% of the volume of the positive electrode active material layer 12, it can effectively improve the thickness and density of the positive electrode active material layer 12 of the positive electrode sheet 1. Embossing 1221 can improve the specific capacity of the positive electrode under high surface density. At the same time, embossing can reduce the initial thickness of the cell, improve the volumetric energy density, store more electrolyte, increase the contact area, increase the delithiation channels, effectively improve the discharge capability and dynamic performance of the core, and increase the first-time efficiency of the battery; when all embossed areas 1221 When the total volume of the regions is less than 1.5% of the volume of the positive electrode active material layer 12, the positive electrode 1 cannot effectively improve the electrolyte storage performance and improve the problem of lithium plating at the arc. When the total volume of all the embossed regions 1221 is greater than 7% of the volume of the positive electrode active material layer 12, the positive electrode is prone to over-pressure in the embossed region. The electrode is prone to breakage due to excessive embossing torque. At the same time, the specific capacity of the over-pressure part is low. For 9μm aluminum foil, the electrode will break if the torque exceeds 300N. If the embossing is too deep, it means that the electrode needs higher torque to press the electrode down, which can easily cause the aluminum foil to break.

[0068] like Figures 1-2 As shown, in one embodiment, the area of ​​embossed 1221 accounts for 10% to 50% of the area of ​​the second region 122.

[0069] Specifically, the area of ​​embossed 1221 accounts for any one or any two values ​​of 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50% of the area of ​​the second region 122; in a preferred embodiment, the area of ​​embossed 1221 accounts for 20%-40% of the area of ​​the second region 122.

[0070] Specifically, when the area of ​​embossing 1221 accounts for 10% to 50% of the area of ​​the second region 122, it can effectively improve the thickness and density of the positive electrode active material layer 12 of the positive electrode sheet 1. Embossing 1221 can improve the specific capacity of the positive electrode under high surface density, store more electrolyte, increase the contact area, increase the delithiation channels, effectively improve the discharge capacity and dynamic performance of the core, and improve the first-time efficiency of the battery. When the area of ​​embossing 1221 is less than 10% of the area of ​​the second region 122, the positive electrode sheet 1 cannot effectively improve the electrolyte storage performance and improve the problem of arc lithium plating. When the area of ​​embossing 1221 is greater than 50% of the area of ​​the second region 122, the pressure area of ​​the electrode sheet increases. Aluminum foil may break during cycling, affecting the cycle retention rate.

[0071] like Figures 1-2 As shown, in one embodiment, the depth of the embossing 1221 along the parallel thickness direction of the positive electrode sheet 1 is 2%-10% of the thickness of the positive electrode active material layer 12.

[0072] Specifically, the depth of embossing 1221 is any one value or a range of any two values ​​from 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% of the thickness of the positive electrode active material layer 12; in a preferred embodiment, the depth of embossing 1221 is 4%-8% of the thickness of the positive electrode active material layer 12.

[0073] Specifically, when the depth of embossing 1221 is 2%-10% of the thickness of the positive electrode active material layer 12, it can effectively improve the thickness and density of the positive electrode active material layer 12 of the positive electrode sheet 1. Embossing 1221 can improve the specific capacity of the positive electrode under high surface density, store more electrolyte, increase the contact area, increase the delithiation channel, effectively improve the discharge capacity and dynamic performance of the core, and improve the first-time efficiency of the battery. When the depth of embossing 1221 is less than that of the positive electrode active material layer 12, it can effectively improve the specific capacity and dynamic performance of the core, and improve the first-time efficiency of the battery. When the thickness of the active material layer 12 is 2%, the positive electrode 1 cannot effectively improve the storage performance of the electrolyte and improve the lithium plating problem. When the depth of the embossing 1221 is greater than 10% of the thickness of the positive electrode active material layer 12, the positive electrode is prone to over-pressure in the embossed area. The electrode is prone to breakage due to excessive embossing torque. At the same time, the specific capacity of the over-pressure part is low. When the embossing torque exceeds 300N, the electrode will break. If the embossing is too deep, it means that the electrode needs higher torque to press the electrode down, which can easily cause the aluminum foil to break.

[0074] like Figures 3-4 As shown, in one embodiment, the one-sided density of the positive electrode active material layer 12 is 200 g / m². 2 ~300g / m 2 ;

[0075] The negative electrode sheet 2 precursor includes a negative electrode current collector 21 and a negative electrode active material layer 22 coated on at least one side of the surface of the negative electrode current collector 21. The negative electrode active material layer 22 includes a negative electrode active material and CMC.

[0076] The negative electrode 2 precursor is processed at high temperature to obtain the negative electrode 2, which causes the CMC in the negative electrode active material layer 22 to carbonize and form conductive carbon black.

[0077] When the one-sided density of the positive electrode active material layer 12 is 200 g / m² 2 The above results show a significant deterioration in the system dynamics, necessitating a substantial improvement in the system's charge and discharge capabilities.

[0078] Specifically, this invention introduces a vacuum baking process into the negative electrode active material, where the CMC in the negative electrode is vacuum baked. The CMC undergoes high-temperature treatment and carbonization into conductive carbon black, enhancing the conductive network. Simultaneously, the carbonized CMC on the electrode surface forms numerous micropores, effectively storing electrolyte, improving low-temperature charge / discharge capability, and preventing lithium plating. However, a drawback is that the electrode thickens after high-temperature vacuum baking. During winding, this increases the core width, making the cell prone to corner breakage. Therefore, the baking time should not be too long, ideally controlled within 5 hours. Excessive baking time will cause the electrode to thicken and break.

[0079] like Figures 1-2 As shown, in one embodiment, the high-temperature treatment temperature of the negative electrode 2 precursor is 200℃~300℃, and the high-temperature treatment time of the negative electrode 2 precursor is 3-7h.

[0080] Specifically, the high-temperature treatment temperature of the negative electrode 2 precursor is any one value or a range of any two values ​​selected from 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃ or 300℃; in a preferred embodiment, the high-temperature treatment temperature of the negative electrode 2 precursor is 22℃~280℃.

[0081] Specifically, the high-temperature treatment time of the precursor of the negative electrode 2 is any one value or any two values ​​from 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h or 7h; in a preferred embodiment, the high-temperature treatment time of the precursor of the negative electrode 2 is 4-6h.

[0082] Specifically, when the high temperature of the negative electrode 2 precursor is 200℃~300℃ and the high temperature treatment time is 3-7h, the CMC is carbonized into conductive carbon black after high temperature treatment, which improves the conductive network. At the same time, the CMC in the carbonized area on the electrode surface will form a large number of micropores, which can effectively store electrolyte, improve low temperature charge and discharge capability, and avoid lithium plating.

[0083] When the high-temperature treatment temperature of the negative electrode precursor 2 is below 200℃, CMC cannot be carbonized into conductive carbon black. When the high-temperature treatment temperature of the negative electrode precursor 2 is above 300℃, it will lead to the loss of some active material, resulting in low capacity. At the same time, excessive baking temperature will cause the electrode to expand and thicken, resulting in an increase in winding width and causing cell corner breakage after cycling. When the high-temperature treatment time of the negative electrode precursor 2 is less than 3 hours, the baking effect will be poor, and the improvement of the electrode kinetics will not be obvious. When the high-temperature treatment time of the negative electrode precursor 2 is more than 7 hours, it will lead to excessive loss of negative electrode areal density, significant capacity reduction, and long-term treatment will increase the thickness of the negative electrode, causing cell corner breakage during cycling. In addition, the electrode may crack, and the capacity retention rate will drop rapidly. The optimal high-temperature treatment temperature is 350℃ for 5 hours.

[0084] like Figures 1-2 As shown, in one embodiment, the negative electrode active material includes silicon-carbon material, wherein the silicon content accounts for 3-15% of the mass of the silicon-carbon material.

[0085] Specifically, the silicon content is any one or any two values ​​from the following ranges: 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15% of the mass of the silicon-carbon material; in a preferred embodiment, the silicon content is 5%-10% of the mass of the silicon-carbon material.

[0086] When the silicon content accounts for 3-15% of the mass of silicon-carbon material, it has the effects of high capacity, long cycle life, low expansion, and non-lithium plating at the negative electrode with a circular arc. When the silicon content accounts for less than 3% of the mass of silicon-carbon material, the improvement effect is not obvious. Since the kinetics of low silicon doping is close to those of the graphite system, the kinetics are excellent, and the addition of new processes has no significant effect on improving its performance. When the silicon content accounts for more than 15% of the mass of silicon-carbon material, it has the problems of large cycle expansion, easy failure of the cell over long cycles, and obvious lithium plating at the negative electrode with a circular arc. The performance deteriorates significantly and is not easy to improve.

[0087] A second aspect of the present invention provides a method for preparing an electrode assembly 100, comprising the following steps:

[0088] S1. Obtain positive electrode 1, negative electrode 2 and separator 3;

[0089] S2. Multiple etching lines 1211 are etched in the first region 121 of the positive electrode active material layer 12 of the positive electrode sheet 1, and embossing 1221 is pressed in the second region 122 of the positive electrode active material layer 12 of the positive electrode sheet 1.

[0090] S3. The positive electrode 1, the separator 3 and the negative electrode 2 are sequentially stacked and wound to form an electrode assembly 100; such that the first region 121 is located in the inner winding of the positive electrode 1 and the second region 122 is located in the outer winding of the positive electrode 1.

[0091] Specifically, in step S1, the positive electrode sheet 1 includes a positive current collector 11 and a positive active material layer 12 coated on at least one side of the surface of the positive current collector 11. The positive active material layer includes a positive active material, a conductive agent, and a binder.

[0092] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide (N... x M y C z (x+y+z=1), nickel-cobalt-aluminum ternary materials (NCA), lithium iron manganese phosphate (LiFe) x Mn y One or more of the following: lithium iron phosphate (LiFePO4), lithium manganese oxide (LiMn2O4), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium-rich manganese-based, lithium nickel manganese oxide (LMNO), and lithium vanadium oxide phosphate (Li3V2(PO4)3,LiVOPO4).

[0093] In some embodiments, the positive electrode conductive agent includes one or more of graphite, superconducting carbon, acetylene black, carbon black, carbon nanotubes, graphene, carbon nanofibers, metal powder, metal fibers, and polyphenylene derivatives.

[0094] In some embodiments, the positive electrode binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0095] In some embodiments, the mass percentage of each component in the positive electrode active material layer is: 95-99 wt% positive electrode active material, 0.3-1.4 wt% conductive agent, and 0.8-1.4 wt% binder.

[0096] When the mass percentage of the positive electrode active material in the positive electrode active material layer is within the above range, the positive electrode sheet can have a higher lithium delithiation and lithium insertion capacity, thus enabling the battery to have a higher capacity.

[0097] The positive current collector 11 is selected from a metallic material that can conduct electrons. Preferably, the positive current collector 11 includes one or more of nickel, tin, copper, and carbon materials. In a more preferred embodiment, the positive current collector 11 is selected from aluminum foil.

[0098] The positive electrode sheet can be prepared according to conventional methods in the art. For example, the positive electrode active material layer is typically formed by coating a positive electrode slurry, consisting of a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and any other components, onto the positive electrode current collector 11, followed by drying and cold pressing. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0099] In some embodiments, the negative electrode sheet 2 includes a negative electrode current collector 21 and a negative electrode active material layer coated on one or both sides of the negative electrode current collector 21. The negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0100] In one embodiment, the negative electrode active material includes lithium metal and lithium metal alloys, lithium-free negative electrodes, etc.

[0101] In some embodiments, the negative electrode conductive agent includes one or more of graphite, superconducting carbon, acetylene black, carbon black, carbon nanotubes, graphene, carbon nanofibers, metal powder, metal fibers, and polyphenylene derivatives.

[0102] In some embodiments, the negative electrode binder includes one or more of CMC, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, and polymethacrylic acid.

[0103] In some embodiments, the mass percentage of each component in the negative electrode active material layer is: 96%-97% negative electrode active material, 0.05%-0.5% conductive agent, and 1.5%-3.5% binder.

[0104] The negative electrode current collector 21 is selected from a metallic material that can conduct electrons. Preferably, the negative electrode current collector 21 includes one or more of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector 21 is selected from copper foil.

[0105] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative electrode active material layer is typically prepared by coating a negative electrode slurry, consisting of a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and any other components, onto the negative electrode current collector 21, followed by high-temperature treatment to obtain the negative electrode sheet 2. The solvent can be an aqueous solvent, but is not limited to it.

[0106] In some embodiments, the diaphragm 3 includes a base membrane and a coating layer. The base membrane is a porous PP layer, which reduces the probability of pore blockage caused by high silicon side reactions. It has strong adhesion and the electrode is firmly adhered. The coating layer is an oily diaphragm coating layer. At the same time, a ceramic layer is added to the coating layer to improve the liquid retention performance and safety performance, and improve long-cycle performance.

[0107] A third aspect of the present invention provides a battery, including a battery casing, an electrolyte, and an electrode assembly 100 as described above, or an electrode assembly 100 prepared by the method described above for preparing the electrode assembly 100.

[0108] In one embodiment, the electrolyte includes a lithium salt, a solvent, and additives;

[0109] In some embodiments, the lithium salt may be selected from one or more of lithium hexafluorophosphate LiPF6, lithium perchlorate LiClO4, lithium tetrafluoroborate LiBF4, lithium hexafluoroarsenate LiAsF6, and other organic lithium salts (such as lithium trifluoromethanesulfonate LiCF3SO, lithium bis(trifluoromethanesulfonyl)imide LiTFSI, lithium bisfluorosulfonylimide LiFSI, lithium trifluoromethanesulfonyl-perfluorobutylsulfonylimide LiTNFSI, lithium fluorosulfonyl-perfluorobutylsulfonylimide LiFNFSI, lithium bis(oxalatoborate)borate LiBOB, LiN(CF3SO2)2, and LiC(SO2CF3)3).

[0110] Lithium salts are Li in electrolytes + The source of lithium salts is to provide free-moving ions for the battery and to play a role in transporting ions inside the battery. In addition, lithium salts can also form a protective layer on the surface of electrode materials, which has an important impact on the battery's capacity, cycle performance, power density, energy density and other performance characteristics.

[0111] In some embodiments, the solvent may be selected from one or more of ethylene carbonate EC, propylene carbonate PC, butene carbonate BC, dimethyl carbonate DMC, diethyl carbonate DEC, methyl ethyl carbonate EMC, and β-butyrolactone BL; the ether compounds include one or more of tetrahydrofuran THF, 2-methyl-tetrahydrofuran 2-Me-THF, dimethoxydimethyl ether DMM, and 1,2-dimethoxyethane DME.

[0112] In some embodiments, the additive may include film-forming additives, conductive additives, flame-retardant additives, overcharge protection additives, additives that control the water and HF content in the electrolyte, general-purpose additives that improve low-temperature performance, or additives that improve the stability of the electrode-electrolyte interface, such as fluoroethylene carbonate (FEC).

[0113] In a preferred embodiment, the battery is manufactured by comprising the following steps:

[0114] The electrode assembly 100 is placed in the pre-formed battery casing, and the electrolyte prepared above is injected into the electrode assembly 100. After vacuum sealing, settling, formation and other processes, a metal battery is obtained.

[0115] The beneficial effects of the present invention will be further illustrated below with reference to the embodiments.

[0116] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described in detail below with reference to embodiments. However, it should be understood that the embodiments of this invention are merely for illustrative purposes and not for limiting the invention, and the embodiments are not limited to those given in the specification. Unless otherwise specified, specific experimental or operational conditions in the embodiments were prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0117] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0118] In the following embodiments, the reagents, materials and instruments used, unless otherwise specified, are commercially available or can be obtained through synthesis methods known in the art.

[0119] Table 1. Design of electrode assemblies for Examples 1-11 and Comparative Examples 1-6;

[0120]

[0121] Example 1

[0122] This embodiment illustrates the electrode assembly and battery disclosed in this invention; it includes the following operational steps:

[0123] Production of positive electrode plates:

[0124] Lithium cobalt oxide (CNT), CNT, SP, and PVDF (PVDF) are mixed in a mass ratio of 98.2:0.3:0.6:0.9. The mixture is thoroughly stirred in NMP solvent to form a homogeneous positive electrode slurry. The viscosity of the positive electrode slurry is 3500-5500 mPas. This slurry is then coated onto at least one side of an aluminum foil current collector, and after drying, rolling, and die-cutting, a suitable positive electrode sheet is obtained.

[0125] The single-sided density of the positive electrode active material layer of the positive electrode sheet is 120 g / m². 2The first region has 1 / 4 of the total number of folds in the positive electrode winding; multiple etching lines are etched in the first region, and the total volume of the etched areas of all etching lines is 1.2% of the volume of the positive electrode active material layer; the depth of the etching lines is 30% of the thickness of the positive electrode active material layer; the spacing between two adjacent etching lines is 1.5 mm; the width of the etching lines is 75 μm; the second region has 3 / 4 of the total number of folds in the positive electrode winding; embossing is performed in the second region, and the total volume of all embossed areas is 1.5% of the volume of the positive electrode active material layer; the embossed area accounts for 10% of the area of ​​the second region; the embossing depth is 2% of the thickness of the positive electrode active material layer.

[0126] Production of negative electrode plates:

[0127] Graphite (negative electrode active material), silicon-carbon negative electrode (negative electrode active material), CNT (conductive agent), SP (conductive agent), PAA (binder), SBR (binder), and CMC-Li (binder) were mixed in a mass ratio of 87.5:8.7:0.1:0.2:1.7:1.3:0.9. The mixture was thoroughly stirred in a deionized water solvent to form a homogeneous negative electrode slurry. This slurry was coated onto at least one side of a copper foil current collector and baked at 300°C for 5 hours to obtain the negative electrode sheet.

[0128] Diaphragm fabrication:

[0129] It includes a base membrane and a coating layer. A porous PP layer is used as the base membrane, and an oily diaphragm coating layer and a ceramic layer are set on the surface of the base membrane.

[0130] Electrolyte preparation:

[0131] The electrolyte includes lithium salt, solvent, and additives; the lithium salt can be selected from lithium hexafluorophosphate (LiPF6), the solvent is carbonate and carboxylic acid ester, and the additives are film-forming additives, vinylene carbonate (VC), acrylate nitrile, and fluoroethylene carbonate (FEC).

[0132] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Then, one end of the positive electrode, separator, and negative electrode are wound to form an electrode assembly, such that the first region is located on the inner winding of the positive electrode and the second region is located on the outer winding of the positive electrode.

[0133] Then, the rolled electrode assembly is placed in the battery casing, and the electrolyte prepared above is injected into the baked and dried battery cell. After vacuum sealing, standing, formation and other processes, the battery is obtained.

[0134] Example 2-11

[0135] Examples 2-11 illustrate the electrode assembly disclosed in this invention, including most of the operating steps in Example 1, with the following differences:

[0136] The various components, parameters, and contents of the electrode assembly shown in Table 1 were used.

[0137] Comparative Examples 1-6

[0138] Comparative Examples 1-6 are used to illustrate the electrode assembly disclosed in this invention, including most of the operating steps in Example 1, the difference being:

[0139] The various components, parameters, and contents of the electrode assembly shown in Table 1 were used.

[0140] Performance testing

[0141] The following performance tests were performed on the batteries prepared in Examples 1-11 and Comparative Examples 1-6:

[0142] (a) Amplification capability test:

[0143] Tested at 25±2℃, discharged at 0.2C to 3.0V, and left to stand for 10 minutes.

[0144] Charge to 4.53V at 0.8C, cut off current at 0.05C, and let stand for 10 minutes.

[0145] Discharge to 3V at 0.2C, let stand for 10 minutes, and record the corresponding initial capacity C0.

[0146] Fully charge at 0.8C, cut-off current 0.05C, and let stand for 10 minutes.

[0147] Discharge to 3V at 0.5C, let stand for 10 minutes, and record the corresponding capacity C1.

[0148] The 0.5C discharge capability is C1 / C0.

[0149] (ii) Battery first-time performance test: First discharge capacity / First charge capacity.

[0150] (III) Low-temperature discharge test of battery:

[0151] (1) Tested at 25±2℃, discharged to 3.0V at 0.2C, and left to stand for 10min.

[0152] (2) Charge to 4.53V at 0.8C, cut off current at 0.05C, and let stand for 10 minutes.

[0153] (3) Discharge to 3V at 0.2C, let stand for 10 minutes, and record the corresponding initial capacity C0.

[0154] (4) At 25℃, it is fully charged to 4.53V at 0.8C, and the cutoff current is 0.05C.

[0155] (5) Let it stand at 0℃ for 3 hours, then discharge it at 0.2C to 3V, and record the discharge capacity C2.

[0156] (6) Discharge C2 / C0 at 0℃.

[0157] (iv) High-temperature cycle test of battery

[0158] (1): At room temperature, record the initial voltage, thickness, and internal resistance.

[0159] (2): Let stand at 45℃ for 2 hours

[0160] (3): Constant current and constant voltage at 0.5C to 4.53V, cutoff current 0.05C, let stand for 10min.

[0161] (4): Discharge to 3V at 0.5C and let stand for 10 minutes.

[0162] (5): Repeat steps 3 and 4 for 500 times, and record the discharge data and the voltage, internal resistance and thickness for 50 / 100 / 200 / 300 / 400 / 500 cycles.

[0163] The test results are shown in Table 2.

[0164] Table 2 Battery Electrochemical Performance

[0165]

[0166] As shown in Tables 1 and 2, comparing Examples 1-11 and Comparative Examples 1-2, when the number of folds in the first region is 1 / 4 to 1 / 2 of the total number of folds in the positive electrode winding, or when the total volume of the etched areas of all etched lines is 1% to 2% of the volume of the positive electrode active material layer, or when the depth of the etched lines is 25% to 40% of the thickness of the positive electrode active material layer, or when the spacing between two adjacent etched lines is 0.5 mm to 1.5 mm, or when the width of the etched lines is 60 μm to 105 μm, or when the total volume of all embossed areas is 1.5% to 7% of the volume of the positive electrode active material layer, or when the embossed area accounts for 10% to 50% of the area of ​​the second region, or when the embossed depth is 2% to 10% of the thickness of the positive electrode active material layer, the high capacity of the core can be maintained while taking into account the long cycle performance of the core, effectively improving the lithium plating problem in the arc region of the positive electrode.

[0167] When at least one of the above conditions is not met, the N / P value of the inner core will be lower, resulting in little improvement to the negative arc region corresponding to the positive electrode sheet, and a loss of capacity; or it may cause the CB value of the negative arc region corresponding to the positive electrode sheet to be too large, resulting in a large loss of core capacity and a deterioration of high-temperature cycle retention rate.

[0168] Comparing Examples 1-11 with Comparative Examples 3-6, it can be seen that when the temperature of the negative electrode precursor high-temperature treatment is 200℃~300℃ and the high-temperature treatment time is 3-7h, the CMC is carbonized into conductive carbon black after high-temperature treatment, which improves the conductive network. At the same time, the CMC in the carbonized area on the electrode surface will form a large number of micropores, which can effectively store electrolyte, improve low-temperature charge and discharge capability, and avoid lithium plating.

[0169] When the temperature of the high-temperature treatment of the negative electrode precursor is below 200℃, CMC cannot be carbonized into conductive carbon black. When the temperature of the high-temperature treatment of the negative electrode precursor is above 300℃, it will lead to the loss of some active material, resulting in low capacity. At the same time, if the baking temperature is too high, the electrode is prone to expansion and thickening, which will increase the winding width and cause the cell to break after cycling.

[0170] When the high-temperature treatment time of the negative electrode precursor is less than 3 hours, the baking effect will be poor and the electrode will not have an obvious effect on the improvement of kinetics. When the high-temperature treatment time of the negative electrode precursor is greater than 7 hours, the negative electrode surface density will be lost too much, the capacity will decrease significantly, and the thickness of the negative electrode will increase over time, resulting in cell cycle breakage. At the same time, the electrode will crack, and the capacity retention rate will drop rapidly.

[0171] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrode assembly, characterized in that: The electrode assembly includes a positive electrode, a negative electrode, and a separator, wherein the positive electrode, the separator, and the negative electrode are stacked and wound together to form the electrode assembly. The positive electrode sheet includes a positive current collector and a positive active material layer coated on at least one side of the surface of the positive current collector, wherein the one-sided density of the positive active material layer is 120 g / m². 2 ~300g / m 2 ; The positive electrode active material layer includes a first region and a second region. The first region is located in the inner winding of the positive electrode sheet, and the second region is located in the outer winding of the positive electrode sheet. Along the thickness direction of the positive electrode sheet, the first region of the positive electrode active material layer is provided with multiple etching lines, and the second region of the positive electrode sheet is provided with multiple embossing patterns.

2. The electrode assembly according to claim 1, characterized in that: The number of folds in the first region is 1 / 4 to 1 / 2 of the total number of folds in the positive electrode winding.

3. The electrode assembly according to claim 1, characterized in that: The total volume of the etched regions of all the etched lines is 1%-2% of the volume of the positive electrode active material layer.

4. The electrode assembly according to claim 3, characterized in that: The depth of the etching line is 25% to 40% of the thickness of the positive electrode active material layer; the spacing between two adjacent etching lines is 0.5 mm to 1.5 mm; and the width of the etching line is 60 μm to 105 μm.

5. The electrode assembly according to claim 4, characterized in that: The depth of the etching line is 30% to 35% of the thickness of the positive electrode active material layer; the spacing between two adjacent etching lines is 0.8 mm to 1.2 mm; and the width of the etching line is 75 μm to 90 μm.

6. The electrode assembly according to claim 1, characterized in that: The number of folds in the second region is 1 / 2 to 3 / 4 of the total number of folds in the positive electrode winding.

7. The electrode assembly according to claim 1, characterized in that: The total volume of all the embossed regions is 1.5%-7% of the volume of the positive electrode active material layer.

8. The electrode assembly according to claim 1, characterized in that: The area of ​​the embossed pattern occupies 10% to 50% of the area of ​​the second region.

9. The electrode assembly according to claim 1, characterized in that: Along the direction parallel to the thickness of the positive electrode sheet, the depth of the embossing is 2%-10% of the thickness of the positive electrode active material layer.

10. The electrode assembly according to claim 1, characterized in that: The single-sided density of the positive electrode active material layer is 200 g / m². 2 ~300g / m 2 ; The negative electrode precursor includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material and CMC; The negative electrode precursor is subjected to high-temperature treatment to obtain the negative electrode, thereby carbonizing the CMC in the negative electrode active material layer to form conductive carbon black.

11. The electrode assembly according to claim 10, characterized in that: The high-temperature treatment of the negative electrode precursor is performed at a temperature of 200℃~300℃ for a duration of 3-7 hours.

12. The electrode assembly according to claim 10, characterized in that: The negative electrode active material includes silicon-carbon material, wherein the silicon content accounts for 3-15% of the mass of the silicon-carbon material.

13. The method for preparing the electrode assembly according to any one of claims 1-11, characterized in that: Includes the following steps: S1. Obtain the positive electrode, negative electrode, and separator; S2. Etch multiple etching lines in the first region of the positive electrode active material layer of the positive electrode sheet, and press embossing in the second region of the positive electrode active material layer of the positive electrode sheet; S3. The positive electrode, the separator, and the negative electrode are sequentially stacked and wound to form an electrode assembly, such that the first region is located in the inner winding of the positive electrode and the second region is located in the outer winding of the positive electrode.

14. A battery, characterized in that: It includes a battery casing, an electrolyte, and an electrode assembly as described in any one of claims 1-12, or an electrode assembly prepared by the method for preparing the electrode assembly as described in claim 13.

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