Positive electrode sheet, secondary battery and electronic apparatus

Abstract

The present application provides a positive electrode sheet, a secondary battery and an electronic apparatus. The positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer; in the width direction of the positive electrode sheet, the positive electrode current collector comprises a first edge and a second edge which are opposite to each other. From the first edge to the second edge, the positive electrode material layer successively comprises an edge region and a main body region, the width of the edge region being W1 mm, the thickness of the edge region being T1 μm, the width of the main body region being W2 mm, and the thickness of the main body region being T2 μm, wherein W1 / W2≤8%, 90%≤T1 / T2≤100%, 18≤T1≤300, and 20≤T2≤300. The positive electrode material layer comprises an organic silicon and polyether-modified ester polymer. The positive electrode sheet satisfies the described characteristics, thus ameliorating the processing problem of edge shrinkage or edge bulging of positive electrode sheets during a coating process.

Description

Positive electrode sheet, secondary battery and electronic device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on March 26, 2024, with application number 202410353874.9 and invention name “A positive electrode plate, secondary battery and electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of electrochemical technology, and in particular to a positive electrode sheet, a secondary battery, and an electronic device. Background Art

[0003] When preparing the positive electrode sheets of lithium-ion batteries at present, the edges of the positive electrode sheets may shrink or bulge after coating. The shrinkage of the positive electrode sheet edges will affect the measurement of the positive electrode sheet size parameters, resulting in a decrease in the quality rate, and will also cause the positive and negative electrode sheets to be misaligned, leading to safety problems in the lithium-ion battery. The bulging edge of the positive electrode sheet will cause the appearance of the positive electrode sheet to be abnormal, which will cause the lithium-ion battery to be too thick; in addition, when the bulging edge is cold-pressed, it will cause the positive electrode sheet to be over-pressurized, resulting in a significant decrease in the ionic conductivity at the over-pressurized area, the kinetic performance of the positive electrode sheet at the over-pressurized area will deteriorate, and the risk of lithium plating will increase; in addition, the bulging edge will also cause the ratio of the local negative electrode capacity to the positive electrode capacity (NP ratio) to decrease. When the NP ratio is less than 1, lithium plating will occur in the lithium-ion battery.

[0004] Therefore, there is an urgent need to provide a positive electrode plate that can improve the processing problems of edge shrinkage or edge bulging that occur during the coating process of the positive electrode plate. Summary of the Invention

[0005] The purpose of this application is to provide a positive electrode sheet, a secondary battery, and an electronic device to improve the processing problems of edge shrinkage or edge bulging that occur during the coating process of the positive electrode sheet. The specific technical solution is as follows:

[0006] The first aspect of the present application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. Along the width direction of the positive electrode sheet, the positive electrode current collector comprises a first edge and a second edge facing each other. From the first edge to the second edge, the positive electrode material layer comprises, in sequence, an edge region and a main region. The edge region has a width of W1 mm ​​and a thickness of T1 μm. The main region has a width of W2 mm and a thickness of T2 μm. W1 / W2 ≤ 8%, 90% ≤ T1 / T2 ≤ 100%, 18 ≤ T1 ≤ 300, and 20 ≤ T2 ≤ 300. The positive electrode material layer comprises an ester polymer modified with silicone and a polyether. When the positive electrode material layer includes an edge region and a main region, the ratio of the width of the edge region to the width of the main region, the thickness of the edge region, the thickness of the main region, and the ratio of the thickness of the edge region to the thickness of the main region are within the scope of this application. The positive electrode material layer includes the above-mentioned substances, which can improve the wetting performance between the positive electrode slurry and the positive electrode collector, and reduce the contact angle between the positive electrode slurry and the positive electrode collector, thereby improving the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0007] In one embodiment of the present application, the organosilicon comprises at least one of trisiloxane, polydimethylsiloxane, polyoxyethylene ether trisiloxane, or vinyl trimethoxysilane. In one embodiment of the present application, the polyether comprises at least one of monoallyl polyether, allyl alcohol polyether, methallyl alcohol polyoxyethylene ether, or lauryl alcohol polyether. In one embodiment of the present application, the main polymer in the ester polymer comprises at least one of polybutyl acrylate, polymethyl acrylate, polycarbonate, polyvinyl acetate, or polyarylate.

[0008] In one embodiment of the present application, based on the mass of the positive electrode material layer, the mass percentage of the ester polymer is w1%, 0.05≤w1≤1. By regulating the mass percentage of the ester polymer within the scope of the present application, the ester polymer has an appropriate mass percentage, which can effectively improve the wetting performance between the positive electrode slurry and the positive electrode current collector, effectively reduce the contact angle between the positive electrode slurry and the positive electrode current collector, and effectively improve the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process. At the same time, it can also make the mass percentage of the positive electrode active material relatively high, thereby enabling the secondary battery to have a higher energy density.

[0009] In one embodiment of the present application, the positive electrode material layer is separated from the positive electrode current collector to obtain positive electrode material layer powder, which is then dissolved in N-methylpyrrolidone (NMP) to obtain a positive electrode slurry having a solid content of 60% to 80%. The surface tension of the positive electrode slurry is γN / m; the surface tension of the positive electrode current collector is Ddyn / cm, and the angle of the edge region is θ, where 0≤D-γ×cosθ≤15. The positive electrode material layer is separated from the positive electrode current collector to obtain positive electrode material layer powder, which is then dissolved in N-methylpyrrolidone to obtain a positive electrode slurry having a solid content of 60% to 80%. The surface tension of the positive electrode slurry, the surface tension of the positive electrode current collector, and the angle of the edge area prepared above satisfy the above relationship, so that the surface tension of the positive electrode slurry matches the surface tension of the positive electrode current collector, which facilitates the wetting and spreading of the positive electrode slurry on the positive electrode current collector. The wetting performance between the positive electrode slurry and the positive electrode current collector is good, and the contact angle between the positive electrode slurry and the positive electrode current collector is small, which effectively improves the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0010] In one embodiment of the present application, the positive electrode plate satisfies at least one of the following characteristics: (1) 26≤D≤39; (2) 30≤γ≤45; (3) 5°≤θ≤75°.

[0011] The positive electrode sheet meets the above characteristics and can improve the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0012] In one embodiment of the present application, the mass percentage of the organosilicon is 10% to 25%, and the mass percentage of the polyether is 20% to 30%, based on the mass of the ester polymer. By regulating the mass percentage of the organosilicon and the mass percentage of the polyether within the scope of this application, the ester polymer can have an appropriate content of NMP-phobic groups and NMP-philic groups, which are arranged more stably at the interface between the solvent NMP and air, further improving the wetting performance between the positive electrode slurry and the positive electrode current collector, further reducing the contact angle between the positive electrode slurry and the positive electrode current collector, and thus further improving the processing problems of edge shrinkage or edge bulging that occur during the coating process of the positive electrode sheet.

[0013] In one embodiment of the present application, the weight-average molecular weight Mw of the ester polymer is 10,000 to 200,000. By regulating the weight-average molecular weight of the ester polymer within the range of the present application, the chain segments of the ester polymer are facilitated to extend into NMP, which is beneficial to the dispersion of the ester polymer itself and the auxiliary dispersion of the positive electrode slurry, and can further improve the wetting performance between the positive electrode slurry and the positive electrode current collector, further reduce the contact angle between the positive electrode slurry and the positive electrode current collector, and thus further improve the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0014] In one embodiment of the present application, the positive electrode material layer satisfies at least one of the following characteristics: (1) the coating weight of the positive electrode material layer is CW, 100 mg / 1540.25 mm 2 ≤CW≤500mg / 1540.25mm 2 ; (2) The compaction density of the positive electrode material layer is PD g / cc, 2.0≤PD≤4.0.

[0015] In one embodiment of the present application, the positive electrode sheet has a bulge value of G μm and G / T2 ≤ 5%. When the G / T2 value is within the above range, the ratio of the bulge value of the positive electrode sheet to the thickness of the main body is relatively small, which can reduce the breakage of the positive electrode sheet during the coating and cold pressing processes, improve the processing performance of the positive electrode sheet, and reduce the overpressure at the edge of the positive electrode sheet during the cold pressing process, so that the edge of the positive electrode sheet also has good ionic conductivity, thereby improving the dynamic performance of the secondary battery and reducing lithium plating in the secondary battery.

[0016] The second aspect of the present application provides a secondary battery, which includes the positive electrode sheet according to any of the aforementioned embodiments. Therefore, the secondary battery provided by the present application has good safety performance and dynamic performance.

[0017] The third aspect of the present application provides an electronic device, which includes the secondary battery in any of the aforementioned embodiments. Therefore, the electronic device provided by the present application has good performance.

[0018] Beneficial effects of this application:

[0019] The present application provides a positive electrode plate, a secondary battery, and an electronic device. The positive electrode plate includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. Along the width direction of the positive electrode plate, the positive electrode current collector includes a first edge and a second edge that are opposite to each other. From the first edge to the second edge, the positive electrode material layer includes an edge region and a main region, wherein the width of the edge region is W1 mm, the thickness of the edge region is T1 μm, the width of the main region is W2 mm, the thickness of the main region is T2 μm, W1 / W2 ≤ 8%, 90% ≤ T1 / T2 ≤ 100%, 18 ≤ T1 ≤ 300, and 20 ≤ T2 ≤ 300. The positive electrode material layer includes an ester polymer modified with silicone and a polyether. The positive electrode plate meets the above characteristics and can improve the processing problems of edge shrinkage or edge bulging that occur during the coating process of the positive electrode plate.

[0020] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0022] FIG1 is a schematic structural diagram of a positive electrode sheet in width and length directions according to an embodiment of the present application;

[0023] FIG2 is a schematic diagram of a partial structure of an edge region of a positive electrode material layer according to an embodiment of the present application;

[0024] FIG3 is a schematic structural diagram of a positive electrode sheet in the width direction and thickness direction according to an embodiment of the present application;

[0025] FIG4 is an appearance diagram of the edge area of ​​the positive electrode sheet of Examples 1-12 of the present application;

[0026] FIG5 is an appearance diagram of the edge area of ​​the positive electrode sheet of Examples 1-11 of the present application;

[0027] FIG6 is an appearance diagram of the edge area of ​​the positive electrode sheet of Examples 1-13 of the present application;

[0028] FIG7 is an appearance diagram of the edge area of ​​the positive electrode plate of Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0029] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0030] It should be noted that, in the specific embodiments of the present application, lithium-ion batteries are used as an example of secondary batteries to explain the present application, but the secondary batteries of the present application are not limited to lithium-ion batteries.

[0031] The present application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. Along the width direction of the positive electrode sheet, the positive electrode current collector comprises a first edge and a second edge facing each other. From the first edge to the second edge, the positive electrode material layer comprises, in sequence, an edge region and a main region. For ease of understanding, a three-dimensional rectangular coordinate system is established with the width direction of the positive electrode sheet as the Y direction, the length direction of the positive electrode sheet as the X direction, and the thickness direction of the positive electrode sheet as the Z direction. It is understood that the dimension of the edge region along the Y direction is the width of the edge region, and the dimension of the edge region along the Z direction is the thickness of the edge region; the dimension of the main region along the Y direction is the width of the main region, and the dimension of the main region along the Z direction is the thickness of the main region. As shown in FIG1 , a positive electrode sheet 10 comprises a positive electrode current collector 100 and a positive electrode material layer 200 disposed on one surface of the positive electrode current collector 100. Along the width direction of the positive electrode sheet 10, i.e., the Y direction, the positive electrode current collector 100 comprises a first edge 110 and a second edge 120 facing each other. From the first edge 110 to the second edge 120, the positive electrode material layer 200 includes an edge region 210 and a main region 220. The width of the edge region is W1 mm, the thickness of the edge region is T1 μm, the width of the main region is W2 mm, the thickness of the main region is T2 μm, W1 / W2 ≤ 8%, and illustratively, the value of W1 / W2 can be 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or a range consisting of any two of the above values. 90%≤T1 / T2≤100%, illustratively, the value of T1 / T2 can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or a range consisting of any two of the above values. 18≤T1≤300, illustratively, the value of T1 can be 18, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, or a range consisting of any two of the above values. 20≤T2≤300, illustratively, the value of T2 can be 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, or a range consisting of any two of the above values. In the present application, the width of the edge area is W1 mm, W1≤22; the width of the main area is W2 mm, 40≤W2≤310.The phrase "a positive electrode material layer disposed on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be disposed on one surface of the positive electrode current collector along its thickness direction, or on both surfaces of the positive electrode current collector along its thickness direction. It should be noted that the "surface" herein can refer to the entire area of ​​the positive electrode current collector or a portion of the positive electrode current collector. This is not particularly limited in this application, as long as the objectives of this application can be achieved.

[0032] The positive electrode material layer includes an ester polymer modified with silicone and polyether. The inventors have found that when the positive electrode material layer includes an edge region and a main region, the ratio of the width of the edge region to the width of the main region, the thickness of the edge region, the thickness of the main region, and the ratio of the thickness of the edge region to the thickness of the main region are within the scope of this application. When preparing the positive electrode slurry, silicone and polyether-modified ester polymers are added. Since the silicone and polyether-modified ester polymers include NMP-phobic groups and NMP-philic groups, the NMP-phobic groups refer to hydroxyl groups, carboxyl groups, and polyether polar groups, and the NMP-philic groups refer to silicone and carbon-oxygen organic chain segments, the above-mentioned ester polymers can be arranged at the interface between the solvent NMP and the air, improve the wetting performance between the positive electrode slurry and the positive electrode current collector, and reduce the contact angle between the positive electrode slurry and the positive electrode current collector, thereby improving the edge shrinkage or edge bulging processing problems of the positive electrode sheet during the coating process. In this application, "ester polymer" refers to "ester polymer modified with silicone and polyether".

[0033] In one embodiment of the present application, the organosilicon includes at least one of trisiloxane, polydimethylsiloxane, polyoxyethylene ether trisiloxane or vinyl trimethoxysilane. In one embodiment of the present application, the polyether includes at least one of monoallyl polyether, allyl alcohol polyether, methylallyl alcohol polyoxyethylene ether or lauryl alcohol polyether. In one embodiment of the present application, the polymer main body in the ester polymer includes at least one of polybutyl acrylate, polymethyl acrylate, polycarbonate, polyvinyl acetate or polyarylate. In the present application, the above-mentioned "trisiloxane" may refer to octamethyl trisiloxane, whose chemical formula is C8H 24 O2Si3, which has not been modified. The above-mentioned "polyoxyethylene ether trisiloxane" refers to a polyether-modified trisiloxane. The chemical formula of the above-mentioned "monoallyl polyether" can be CH2=CHCH2O(CH2CH2O) n H, 10<n<100. The chemical formula of the above-mentioned "propylene alcohol polyether" can be H2C=CHCH2O(C2H4O)a(C3H6O)bH, 5<a<50, 5<b<50. The above-mentioned "lauryl alcohol polyether" can refer to sodium laureth sulfate.

[0034] In one embodiment of the present application, based on the mass of the positive electrode material layer, the mass percentage of the ester polymer is w1%, 0.05≤w1≤1. Exemplarily, the value of w1 can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range consisting of any two of the above values. By regulating the mass percentage of the ester polymer within the scope of this application, the ester polymer has a suitable mass percentage, which can effectively improve the wetting performance between the positive electrode slurry and the positive electrode current collector, effectively reduce the contact angle between the positive electrode slurry and the positive electrode current collector, and effectively improve the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process. At the same time, it can also make the mass percentage of the positive electrode active material relatively high, so that the secondary battery has a higher energy density.

[0035] In one embodiment of the present application, the positive electrode material layer is separated from the positive electrode current collector to obtain a positive electrode material layer powder. The positive electrode material layer powder is dissolved in N-methylpyrrolidone to obtain a positive electrode slurry with a solid content of 60% to 80%. The surface tension of the positive electrode slurry is γN / m; the surface tension of the positive electrode current collector is Ddyn / cm, and the angle of the edge region is θ, where 0≤D-γ×cosθ≤15. For example, the value of D-γ×cosθ can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two of the above values. To facilitate understanding of the angle of the edge region, FIG2 shows a schematic diagram of a partial structure of the edge region of the positive electrode material layer. As shown in FIG2, the angle θ of the edge region refers to the angle between the contact interface between the positive electrode current collector 100 and the edge region 210 and the contact interface between the edge region 210 and the air. The positive electrode material layer is separated from the positive electrode current collector to obtain a positive electrode material layer powder, which is then dissolved in N-methylpyrrolidone to obtain a positive electrode slurry having a solid content of 60% to 80%. The surface tension of the positive electrode slurry, the surface tension of the positive electrode current collector, and the angle of the edge region satisfy the aforementioned relationship, so that the surface tension of the positive electrode slurry matches the surface tension of the positive electrode current collector, facilitating the wetting and spreading of the positive electrode slurry on the positive electrode current collector. The wetting performance between the positive electrode slurry and the positive electrode current collector is good, and the contact angle between the positive electrode slurry and the positive electrode current collector is small, effectively improving the processing problems of edge shrinkage or edge bulging that occur during the coating process of the positive electrode sheet.

[0036] In one embodiment of the present application, the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes lithium iron phosphate, the positive electrode material layer is separated from the positive electrode current collector to obtain a positive electrode material layer powder, and the positive electrode material layer powder is dissolved in N-methylpyrrolidone to obtain a positive electrode slurry with a solid content of 60% to 70%, and the surface tension of the positive electrode slurry is γN / m; the surface tension of the positive electrode current collector is D dyn / cm, and the angle of the edge region is θ, 0≤D-γ×cosθ≤15. Exemplarily, the value of D-γ×cosθ can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two of the above values. The positive electrode active material in the positive electrode material layer includes lithium iron phosphate, and the positive electrode slurry is prepared according to the above method. The surface tension of the prepared positive electrode slurry, the surface tension of the positive electrode current collector, and the angle of the edge area satisfy the above relationship, so that the surface tension of the positive electrode slurry matches the surface tension of the positive electrode current collector, which facilitates the wetting and spreading of the positive electrode slurry on the positive electrode current collector. The wetting performance between the positive electrode slurry and the positive electrode current collector is good, and the contact angle between the positive electrode slurry and the positive electrode current collector is small, which effectively improves the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0037] In one embodiment of the present application, the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes a nickel-cobalt-manganese ternary material, and the nickel-cobalt-manganese ternary material includes LiNi 0.9 Co 0.05 Mn 0.05 O2(Ni90),LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523) or LiNi 1 / 3 Co 1 / 3 Mn1 / 3At least one of O2 (NCM111). The positive electrode material layer is separated from the positive electrode current collector to obtain a positive electrode material layer powder, which is dissolved in N-methylpyrrolidone to obtain a positive electrode slurry with a solid content of 68% to 78%. The surface tension of the positive electrode slurry is γN / m; the surface tension of the positive electrode current collector is D dyn / cm, and the angle of the edge region is θ, where 0 ≤ D-γ × cosθ ≤ 15. Exemplarily, the value of D-γ × cosθ can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two of the foregoing values. The positive electrode active material in the positive electrode material layer includes a nickel-cobalt-manganese ternary material, and the positive electrode slurry is prepared according to the above method. The surface tension of the prepared positive electrode slurry, the surface tension of the positive electrode current collector, and the angle of the edge zone satisfy the above relationship, so that the surface tension of the positive electrode slurry matches the surface tension of the positive electrode current collector, which facilitates the wetting and spreading of the positive electrode slurry on the positive electrode current collector. The wetting performance between the positive electrode slurry and the positive electrode current collector is good, and the contact angle between the positive electrode slurry and the positive electrode current collector is small, which effectively improves the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0038] In one embodiment of the present application, the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes lithium manganate, the positive electrode material layer is separated from the positive electrode current collector to obtain a positive electrode material layer powder, and the positive electrode material layer powder is dissolved in N-methylpyrrolidone to obtain a positive electrode slurry with a solid content of 65% to 75%, and the surface tension of the positive electrode slurry is γN / m; the surface tension of the positive electrode current collector is D dyn / cm, and the angle of the edge region is θ, 0≤D-γ×cosθ≤15. Exemplarily, the value of D-γ×cosθ can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two of the above values. The positive electrode active material in the positive electrode material layer includes lithium manganese oxide, and the positive electrode slurry is prepared according to the above method. The surface tension of the prepared positive electrode slurry, the surface tension of the positive electrode current collector, and the angle of the edge area satisfy the above relationship, so that the surface tension of the positive electrode slurry matches the surface tension of the positive electrode current collector, which facilitates the wetting and spreading of the positive electrode slurry on the positive electrode current collector. The wetting performance between the positive electrode slurry and the positive electrode current collector is good, and the contact angle between the positive electrode slurry and the positive electrode current collector is small, which effectively improves the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0039] In one embodiment of the present application, the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes lithium cobalt oxide, the positive electrode material layer is separated from the positive electrode current collector to obtain a positive electrode material layer powder, and the positive electrode material layer powder is dissolved in N-methylpyrrolidone to obtain a positive electrode slurry with a solid content of 70% to 80%, and the surface tension of the positive electrode slurry is γN / m; the surface tension of the positive electrode current collector is D dyn / cm, and the angle of the edge region is θ, 0≤D-γ×cosθ≤15. Exemplarily, the value of D-γ×cosθ can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two of the above values. The positive electrode active material in the positive electrode material layer includes lithium cobalt oxide, and the positive electrode slurry is prepared according to the above method. The surface tension of the prepared positive electrode slurry, the surface tension of the positive electrode current collector, and the angle of the edge zone satisfy the above relationship, so that the surface tension of the positive electrode slurry matches the surface tension of the positive electrode current collector, which facilitates the wetting and spreading of the positive electrode slurry on the positive electrode current collector. The wetting performance between the positive electrode slurry and the positive electrode current collector is good, and the contact angle between the positive electrode slurry and the positive electrode current collector is small, which effectively improves the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0040] In one embodiment of the present application, 26≤D≤39, preferably, 29≤D≤33. For example, the value of D can be 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or a range consisting of any two of the above values. By regulating the value of D within the scope of this application, the positive electrode collector has a suitable surface tension. On the one hand, the positive electrode collector has less residual oil. When the positive electrode active material is lithium iron phosphate, the water-based gravure coating method is used to coat the conductive slurry on the surface of the positive electrode collector to achieve a better coverage effect, which can improve the adhesion between the positive electrode material layer and the positive electrode collector. When the positive electrode active material is nickel-cobalt-manganese ternary material, lithium manganate or lithium cobaltate, the shrinkage of the positive electrode sheet can be reduced, the possibility of misalignment between the positive electrode sheet and the negative electrode sheet can be reduced, and the safety performance of the secondary battery can be further improved. On the other hand, the surface treatment steps of the positive electrode collector can be reduced, such as reducing the corona or water washing steps, thereby reducing the production cost of the secondary battery. In addition, it can also effectively improve the wetting performance between the positive electrode slurry and the positive electrode collector, effectively reduce the contact angle between the positive electrode slurry and the positive electrode collector, and effectively improve the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0041] In one embodiment of the present application, 30≤γ≤45. For example, the value of γ can be 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, or a range consisting of any two of the above values. The mass percentage of the ester polymer affects the surface tension of the positive electrode slurry. When the surface tension of the positive electrode slurry is within the above range, the wettability between the positive electrode slurry and the positive electrode current collector is good, and the contact angle between the positive electrode slurry and the positive electrode current collector is small, which effectively improves the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0042] In one embodiment of the present application, 5°≤θ≤75°. For example, θ can be 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, or a range consisting of any two of the above angles. The positive electrode material layer includes an ester polymer modified with silicone and a polyether. During the coating process, the wettability between the positive electrode slurry and the positive electrode current collector is good. The angle of the edge area is within the above range, which effectively improves the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0043] In one embodiment of the present application, based on the mass of the ester polymer, the mass percentage of silicone is 10% to 25%. Exemplarily, the mass percentage of silicone can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or a range consisting of any two of the above values; the mass percentage of polyether is 20% to 30%. Exemplarily, the mass percentage of polyether can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or a range consisting of any two of the above values. By regulating the mass percentage of silicone and the mass percentage of polyether within the scope of this application, the ester polymer can have an appropriate content of NMP-phobic groups and NMP-philic groups, which are more stably arranged at the interface between the solvent NMP and the air, and can further improve the wetting performance between the positive electrode slurry and the positive electrode current collector, further reduce the contact angle between the positive electrode slurry and the positive electrode current collector, thereby further improving the processing problems of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0044] In one embodiment of the present application, the weight average molecular weight Mw of the ester polymer is 10,000 to 200,000. For example, the value of Mw can be 10,000, 20,000, 40,000, 60,000, 80,000, 100,000, 120,000, 140,000, 160,000, 180,000, 200,000 or a range consisting of any two of the above values. By regulating the weight average molecular weight of the ester polymer within the scope of the present application, it is beneficial for the chain segments of the ester polymer to extend into NMP, which is beneficial to the dispersion of the ester polymer itself and the auxiliary dispersion of the positive electrode slurry, and can further improve the wetting performance between the positive electrode slurry and the positive electrode current collector, further reduce the contact angle between the positive electrode slurry and the positive electrode current collector, thereby further improving the processing problem of edge shrinkage or edge bulging of the positive electrode sheet during the coating process.

[0045] In one embodiment of the present application, the coating weight of the positive electrode material layer is CW, 100 mg / 1540.25 mm 2 ≤CW≤500mg / 1540.25mm 2 For example, CW can be 100mg / 1540.25mm 2 、150mg / 1540.25mm 2 , 200mg / 1540.25mm 2 、250mg / 1540.25mm 2 、300mg / 1540.25mm 2 、350mg / 1540.25mm 2 , 400mg / 1540.25mm 2 、450mg / 1540.25mm 2 、500mg / 1540.25mm 2 Or a range consisting of any two of the above values. By regulating the coating weight of the positive electrode material layer within the range of this application, cracking of the positive electrode material layer during processing can be reduced; it can also ensure that lithium ions have a suitable transmission distance and that the positive electrode sheet is well wetted, thereby providing the secondary battery with better cycle performance and rate performance; at the same time, it can meet the equipment capacity and ensure that the positive electrode sheet has a high rate of application during the coating process.

[0046] In one embodiment of the present application, the compaction density of the positive electrode material layer is PD g / cc, 2.0≤PD≤4.0. For example, the value of PD can be 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0 or a range consisting of any two of the above values. By regulating the compaction density of the positive electrode material layer within the scope of the present application, on the one hand, when the positive electrode active material adopts lithium iron phosphate, the embrittlement and powdering of the positive electrode material layer can be reduced; when the positive electrode active material adopts nickel-cobalt-manganese ternary material, lithium manganate or lithium cobaltate, the integrity of the positive electrode active material particles can be better maintained, the occurrence of side reactions can be reduced, and the cycle performance of the secondary battery can be improved; on the other hand, it can also make the positive electrode active material particles and the conductive agent have a suitable contact area, the contact impedance is small, and the rate performance and cycle performance of the secondary battery are improved.

[0047] In one embodiment of the present application, the bulge value of the positive electrode sheet is Gμm, G / T2≤5%, preferably, G / T2≤3%. Exemplarily, the value of G / T2 can be 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range consisting of any two of the above values. In order to facilitate understanding of the bulge value of the positive electrode sheet, Figure 3 shows a schematic structural diagram of the width direction and thickness direction of the positive electrode sheet. As shown in Figure 3, along the Z direction, the distance between the highest point of the edge area 210 and the highest point of the main area 220 is the bulge value G of the positive electrode sheet. When the value of G / T2 is within the above range, the ratio of the bulge value of the positive electrode sheet to the thickness of the main area is relatively small, which can reduce the breakage of the positive electrode sheet during the coating process and the cold pressing process, improve the processing performance of the positive electrode sheet, and reduce the overpressure at the edge of the positive electrode sheet during the cold pressing process, so that the edge of the positive electrode sheet also has better ion conductivity, thereby improving the kinetic performance of the secondary battery and reducing lithium plating of the secondary battery.

[0048] The present application has no particular restrictions on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it can include aluminum foil, aluminum alloy foil, or a composite current collector (such as an aluminum-carbon composite current collector). The present application has no particular restrictions on the thickness of the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 8μm to 20μm.

[0049] The positive electrode material layer of the present application also includes a positive electrode active material, a binder and a conductive agent. The present application has no particular restrictions on the positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include but is not limited to at least one of lithium iron phosphate, nickel cobalt manganese ternary material, lithium manganate, lithium cobaltate, lithium nickel cobalt aluminum oxide, lithium manganese iron phosphate or lithium titanate. The present application has no particular restrictions on the binder, as long as the purpose of the present application can be achieved. For example, the binder may include but is not limited to polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, sodium carboxymethyl cellulose, polyimide, polyamide-imide, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene or potassium carboxymethyl cellulose. The present application has no particular restrictions on the conductive agent, as long as the purpose of the present application can be achieved. For example, the conductive agent may include but is not limited to at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fiber, flake graphite, graphene, metal materials or conductive polymers. The above-mentioned conductive carbon black may include but is not limited to acetylene black and / or Ketjen black. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powder and / or metal fibers. Specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. The present application does not particularly limit the mass percentages of the positive electrode active material, binder and conductive agent in the positive electrode material layer. Those skilled in the art may select according to actual needs as long as the purpose of the present application can be achieved. For example, based on the mass of the positive electrode material layer, the mass percentage of the positive electrode active material is w2%, the mass percentage of the binder is w3%, the mass percentage of the conductive agent is w4%, 90≤w2≤98.95, 0.5≤w3≤5, and 0.5≤w4≤5.

[0050] This application does not specifically limit the preparation method of the organosilicon-polyether-modified ester polymer, as long as the objectives of this application can be achieved. For example, the preparation method of the organosilicon-polyether-modified ester polymer includes, but is not limited to, the following steps: placing a polyether, a polymer body, and a catalyst in a reactor, reacting at 180°C to 240°C for 6 to 8 hours, obtaining a reaction product A after post-treatment such as filtration and distillation, and placing the reaction product A with the organosilicon and catalyst in a reactor, and reacting at 75°C to 95°C for 2 to 6 hours to obtain the organosilicon-polyether-modified ester polymer. This application does not specifically limit the catalyst, as long as the objectives of this application can be achieved. For example, the catalyst may include, but is not limited to, an organic acid catalyst or titanium tetrachloride. The organic acid catalyst may include, but is not limited to, benzenesulfonic acid, p-toluenesulfonic acid, or phosphoric acid. In this application, commercially available organosilicon-polyether-modified ester polymers may also be used. This application does not specifically limit the catalyst, as long as the objectives of this application can be achieved.

[0051] This application does not impose any particular restrictions on the preparation method of the positive electrode sheet, as long as the purpose of this application can be achieved. For example, the preparation method of the positive electrode sheet includes but is not limited to the following steps: uniformly mixing the positive electrode active material, the conductive agent, the binder, the silicone and the polyether-modified ester polymer, adding a solvent to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on one surface of the positive electrode current collector and dried to obtain a positive electrode sheet coated with a positive electrode material layer on one side, and then the above steps are repeated on the other surface of the positive electrode current collector to obtain a positive electrode sheet coated with a positive electrode material layer on both sides.

[0052] In the present application, the positive electrode slurry prepared by the method of "separating the positive electrode material layer from the positive electrode current collector to obtain positive electrode material layer powder, dissolving the positive electrode material layer powder in N-methylpyrrolidone to obtain a positive electrode slurry with a solid content of 60% to 80%" has the same surface tension test results as the positive electrode slurry obtained in the above-mentioned process of preparing the positive electrode sheet.

[0053] The present application has no particular limitation on the manner in which the weight percentage of the ester polymer is controlled, as long as the purpose of the present application can be achieved. For example, the weight percentage of the ester polymer can be controlled by controlling the weight percentage of the added ester polymer.

[0054] This application does not specifically limit the method for regulating the surface tension of the positive electrode current collector, as long as the purpose of this application can be achieved. For example, commercially available positive electrode current collectors with different surface tensions can be selected and tested in combination with the test method "Surface Tension Test of Positive Electrode Current Collectors" in this application to select a positive electrode current collector with the desired surface tension.

[0055] The present application does not particularly limit the method for regulating the surface tension of the positive electrode slurry, as long as the purpose of the present application can be achieved. For example, the surface tension of the positive electrode slurry can be regulated by regulating the mass percentage of the ester polymer. For example, when the mass percentage of the ester polymer is within a certain range, increasing the mass percentage of the ester polymer decreases the surface tension of the positive electrode slurry; decreasing the mass percentage of the ester polymer increases the surface tension of the positive electrode slurry.

[0056] The present application does not particularly limit the method for controlling the weight percentage of the organosilicon, as long as the purpose of the present application can be achieved. For example, when the total mass of the reactants remains unchanged, the weight percentage of the organosilicon can be controlled by controlling the amount of organosilicon added.

[0057] The present application has no particular limitation on the method for controlling the weight percentage of the polyether, as long as the purpose of the present application can be achieved. For example, when the total mass of the reactants remains unchanged, the weight percentage of the polyether can be controlled by controlling the amount of polyether added.

[0058] The present application does not particularly limit the method for controlling the weight-average molecular weight of the ester polymer, so long as the objectives of the present application can be achieved. For example, commercially available ester polymers of varying weight-average molecular weights can be selected and tested for their weight-average molecular weight using the test method described in "Weight-average Molecular Weight of Ester Polymers" herein, ultimately selecting an ester polymer having the desired weight-average molecular weight.

[0059] In the present application, the coating weight of the positive electrode material layer can be controlled by methods known to those skilled in the art. For example, when the positive electrode slurry is coated on the surface of the positive electrode current collector, the coating amount of the positive electrode slurry can be increased based on a certain solid content of the positive electrode slurry to increase the coating weight of the positive electrode material layer. This application is not particularly limited, as long as the purpose of this application can be achieved.

[0060] In the present application, the compaction density of the positive electrode material layer can be controlled by methods known to those skilled in the art. For example, the compaction density of the positive electrode material layer can be controlled by controlling the cold pressing pressure during the cold pressing process. For example, when other conditions remain unchanged, increasing the cold pressing pressure increases the compaction density of the positive electrode material layer; decreasing the cold pressing pressure decreases the compaction density of the positive electrode material layer.

[0061] The second aspect of the present application provides a secondary battery, which includes the positive electrode sheet according to any of the aforementioned embodiments. Therefore, the secondary battery provided by the present application has good safety performance and dynamic performance.

[0062] In the present application, the secondary battery also includes a negative electrode plate, and the negative electrode plate includes a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer arranged on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be arranged on one surface of the negative electrode current collector along the thickness direction of itself, or on two surfaces of the negative electrode current collector along the thickness direction of itself. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or a partial area of ​​the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the negative electrode current collector, as long as the purpose of this application can be achieved. For example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper or composite current collector (such as lithium copper composite current collector, carbon copper composite current collector, nickel copper composite current collector, titanium copper composite current collector, etc.).

[0063] The negative electrode material layer of the present application includes a negative electrode active material. The present application has no particular limitation on the negative electrode active material, as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0.5<x<1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel structure lithium titanate Li4Ti5O 12 , Li-Al alloy or metallic lithium. The negative electrode material layer of the present application also includes a binder and a conductive agent. The present application has no special restrictions on the binder and the conductive agent in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the binder in the negative electrode material layer can be at least one of the above-mentioned binders, and the conductive agent in the negative electrode material layer can be at least one of the above-mentioned conductive agents. The present application has no special restrictions on the mass ratio of the negative electrode active material, the binder and the conductive agent in the negative electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved.

[0064] The present application does not particularly limit the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm. The present application does not particularly limit the thickness of the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the single-sided negative electrode material layer is 30 μm to 250 μm.

[0065] In the present application, the secondary battery also includes an electrolyte. The electrolyte includes a lithium salt. The present application does not particularly limit the type of lithium salt, and lithium salts known in the art can be used. For example, the lithium salt can include but is not limited to at least one of lithium hexafluorophosphate (LiPF6), lithium bistrifluoromethanesulfonyl imide (LiN(CF3SO2)2, LiTFSI), lithium bis(fluorosulfonyl)imide (Li(N(SO2F)2), LiFSI), lithium difluorophosphate (LiPO2F2), lithium bisoxalatoborate (LiB(C2O4)2, LiBOB) or lithium difluorooxalatoborate (LiBF2(C2O4), LiDFOB). The present application does not particularly limit the mass percentage of the lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. The electrolyte includes a non-aqueous organic solvent. The present application does not particularly limit the non-aqueous organic solvent, as long as the purpose of the present application can be achieved. For example, the non-aqueous organic solvent can include at least one of a carbonate compound, a carboxylate compound, an ether compound or other organic solvents. Above-mentioned carbonate compound can include but not limited to at least one in linear carbonate compound, cyclic carbonate compound or fluorinated carbonate compound.Above-mentioned linear carbonate compound can include but not limited to at least one in dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC) or ethyl methyl carbonate (EMC).Above-mentioned cyclic carbonate compound can include but not limited to at least one in ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The above-mentioned fluorinated carbonate compound may include but is not limited to fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate or at least one of trifluoromethylethylene carbonate. The above-mentioned carboxylate compound may include but is not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate or propyl propionate. The above-mentioned ether compound may include but is not limited to at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphate ester.The present application has no particular limitation on the mass percentage of the non-aqueous organic solvent in the electrolyte, as long as the purpose of the present application can be achieved.

[0066] In the present application, the secondary battery also includes a diaphragm. The diaphragm is used to separate the positive electrode plate and the negative electrode plate, prevent internal short circuit of the secondary battery, allow electrolyte ions to pass freely, and do not affect the electrochemical charge and discharge process. The present application has no special restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm may include but is not limited to polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of diaphragm may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane.

[0067] In the present application, the diaphragm may include a base film and a surface treatment layer. The base film may be a non-woven fabric or a composite film having a porous structure, and the material of the base film may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the base film, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic material. For example, the inorganic layer includes inorganic particles and a binder for the diaphragm. The present application does not particularly limit the above-mentioned inorganic particles, and for example, it may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The present application does not particularly limit the above-mentioned binder for the diaphragm, and for example, it may be at least one of the aforementioned binders. The polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0068] The secondary battery of this application also includes a packaging bag for containing the positive electrode sheet, separator, negative electrode sheet, and electrolyte, as well as other components of the secondary battery known in the art. This application does not limit these other components. This application does not specifically limit the packaging bag and can be any packaging bag known in the art, as long as it can achieve the purpose of this application. For example, an aluminum-plastic film packaging bag can be used.

[0069] The secondary battery of the present application is not particularly limited and may include any device that generates an electrochemical reaction. In one embodiment of the present application, the secondary battery may include but is not limited to: a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery or a lithium ion polymer secondary battery, etc.

[0070] The preparation process of the secondary battery of the present application is well known to those skilled in the art, and is not particularly limited in the present application. For example, it may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly with a wound structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly with a stacked structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, overcurrent protection elements, guide plates, etc. may also be placed in the packaging bag as needed to prevent the pressure inside the secondary battery from rising and overcharging and discharging. Among them, the packaging bag is a packaging bag known in the art, and the present application does not limit this.

[0071] The third aspect of the present application provides an electronic device, which includes the secondary battery in any of the aforementioned embodiments. Therefore, the electronic device provided by the present application has good performance.

[0072] The present application does not particularly limit the type of electronic device, and the electronic device may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0073] Example

[0074] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0075] Test methods and equipment:

[0076] Surface tension test of positive electrode current collector:

[0077] Use a dyne pen (manufacturer: ACCU) with different dyne values ​​to draw lines along the surface of the positive current collector and perpendicular to it. If the line does not shrink within 3 seconds, the specified dyne value is reached. Use a dyne pen with the same dyne value three times. If the line does not shrink within 3 seconds each time, the specified dyne value is the surface tension of the positive current collector. For lithium-ion batteries, since the positive current collector at the tab is relatively flat, the lithium-ion battery can be disassembled, the welded tab removed, and the positive current collector at the tab removed for testing.

[0078] Surface tension test of positive electrode slurry:

[0079] Disassemble the lithium-ion battery, remove the positive electrode sheet, wash the electrolyte off the positive electrode sheet with a DMC solution, air-dry the positive electrode sheet, and then scrape the positive electrode material layer powder with a knife. Scan the positive electrode material layer powder using a scanning electron microscope (SEM) with an energy dispersive spectrometer to determine the type of positive electrode active material. Based on the solid content specified above (if the positive electrode active material is lithium iron phosphate, the solid content of the positive electrode slurry is 60% to 70%; if the positive electrode active material is a nickel-cobalt-manganese ternary material, the solid content of the positive electrode slurry is 68% to 78%; if the positive electrode active material is lithium manganate, the solid content of the positive electrode slurry is 65% to 75%; if the positive electrode active material is lithium cobaltate, the solid content of the positive electrode slurry is 70% to 80%), the positive electrode material layer powder is evenly dispersed in NMP to obtain a positive electrode slurry. The surface tension of the positive electrode slurry is then measured using a contact angle meter (model: JC2000CS). Clean the injector and rinse it with the positive electrode slurry to be tested three times. Then absorb the positive electrode slurry and drop the sample on the contact angle meter for testing. Use the hanging drop method and select the photo before dropping for "image analysis" to obtain the surface tension of the positive electrode slurry. Each group of positive electrode slurry samples is tested 5 times and the average value is taken.

[0080] Angle test of edge area:

[0081] Disassemble the lithium-ion battery, remove the positive electrode sheet, and air dry the positive electrode sheet. Then, use a slitting knife to cut 5 cm from the first edge of the positive current collector along the Y direction to obtain a sample of the edge section. Use a charge-coupled device (CCD) detector to measure the angle of the edge area. First, focus, twist the fine-tuning nut, adjust the image to a clear state, take a photo, and then use the "angle measurement tool" to measure the angle of the edge area. As shown in Figure 2, the angle θ of the edge area refers to the angle between the contact interface between the positive current collector and the edge area and the contact interface between the edge area and the air.

[0082] Test of mass percentage of silicone and polyether:

[0083] Disassemble the lithium-ion battery, remove the positive electrode, and use DMC solution to wash away the electrolyte on the positive electrode. Dry the positive electrode, then scrape off the positive electrode material layer powder with a knife. Centrifuge to remove the positive electrode active material and conductive agent, and then distill to obtain an ester polymer sample. Infrared spectroscopy is used to utilize the absorption peak generated by the ester polymer sample when absorbing infrared light of a specific wavelength (organic silicon characteristic peak and wave number range: carbon-hydrogen bond stretching vibration peak is 2000cm -1 to 2200cm -1 , the carbon-silicon bond stretching vibration peak is 1000cm -1 Up to 1300cm -1 ; Polyether characteristic peak and wavenumber range: CO is 800cm -1 Up to 1000cm -1 , OH is 3200cm -1 to 3600cm -1 and C=O at 1850cm -1 to 1600cm -1 ), combined with the standard curve and the concentration calculation formula (the standard curve can be obtained by Lambert-Beer law, and the concentration can be obtained according to the standard curve and Y (concentration) = aX (absorbance) + b; where a and b can be obtained from the standard curve), the mass percentage of silicone and polyether can be obtained. The test wave number range of infrared spectroscopy is: 4000cm -1 Up to 400cm -1 .

[0084] Weight average molecular weight test of ester polymers:

[0085] Disassemble the lithium-ion battery, remove the positive electrode sheet, use DMC solution to wash away the electrolyte on the positive electrode sheet, dry the positive electrode sheet, then scrape the positive electrode material layer powder with a knife, remove the positive electrode active material and conductive agent by centrifugation, and then distill to obtain an ester polymer. Use gel chromatography to test the weight average molecular weight of the ester polymer. Dissolve 0.01g of ester polymer in 5mL of solvent (N-methylpyrrolidone) to obtain a solution. After the solution is completely dissolved, filter out impurities in the solution with a filter head, and then use a gel chromatography instrument (model PL-GPC220) to test the weight average molecular weight of the ester polymer.

[0086] Coating weight test of positive electrode material layer:

[0087] Disassemble the lithium-ion battery, remove the positive electrode sheet, clean the positive electrode sheet with DMC, and dry the positive electrode sheet. Select the area on the positive electrode sheet including the double-sided positive electrode material layer, and cut 10 pieces with an area of ​​1540.25mm using a cutting machine. 2The positive electrode material layer on the ten small discs is wiped off and weighed to obtain the average value M. The positive electrode material layer coating weight CW = (Mm) / (2×1540.25) is then wiped off and weighed to obtain the average value m.

[0088] Compaction density test of positive electrode material layer:

[0089] Disassemble the lithium-ion battery, remove the positive electrode sheet, clean the positive electrode sheet with DMC, and dry the positive electrode sheet. Select the area on the positive electrode sheet including the double-sided positive electrode material layer, and cut 10 pieces with an area of ​​1540.25mm using a cutting machine. 2 Weigh the small discs and take the average value M. Then use a caliper to measure the thickness of the small discs and take the average value H. Then wipe off the positive electrode material layer from 10 small discs, weigh them, and take the average value m. Then use a caliper to measure the thickness of the positive electrode current collector and take the average value h. The compacted density of the positive electrode material layer, PD, = (Mm) / [1540.25 × (Hh)].

[0090] Drum edge value test of positive electrode:

[0091] Disassemble the lithium-ion battery, remove the positive electrode sheet, and dry the positive electrode sheet. Then, use a slitting knife to cut 5 cm from the first edge of the positive electrode current collector along the Y direction to obtain an edge section sample. Use a charge-coupled device (CCD) detector to test the drum edge value of the positive electrode sheet. First, focus, twist the fine-tuning nut, adjust the image to a clear state, take a photo, and then use the "parallel line measurement tool" to measure the drum edge value of the positive electrode sheet. As shown in Figure 3, along the Z direction, the distance between the highest point of the edge area and the highest point of the main area is the drum edge value G of the positive electrode sheet.

[0092] Example 1-1

[0093] <Preparation of positive electrode sheet>

[0094] The positive electrode active material nickel cobalt manganese ternary material (LiNi 0.8 Co 0.1 Mn 0.1 O2), conductive agent acetylene black, binder polyvinylidene fluoride (PVDF), silicone and polyether modified ester polymer are mixed in a weight ratio of 90:4.5:4.5:1, NMP is added as a solvent, and a slurry with a solid content of 68wt% is prepared. After vacuum stirring, a positive electrode slurry is obtained. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm and dried at 120°C to obtain a positive electrode sheet with a single-sided positive electrode material layer; wherein the coating weight CW of the positive electrode material layer is 485mg / 1540.25mm 2The above steps were then repeated on the other surface of the aluminum foil to obtain a double-sided positive electrode sheet coated with a positive electrode material layer. After cold pressing, sheet cutting, and tab welding, the sheet was vacuum dried at 85°C for 4 hours to obtain a positive electrode sheet with a positive electrode material layer measuring 84 mm x 867 mm. The compacted density (PD) of the cold-pressed positive electrode material layer was 2.1 g / cc.

[0095] Among them, in the silicone-and-polyether-modified ester polymer, the silicone is trisiloxane, the polyether is lauryl alcohol polyether, and the polymer main body is polymethyl acrylate; based on the mass of the ester polymer, the mass percentage of the silicone is 15%, and the mass percentage of the polyether is 25%; the weight-average molecular weight Mw of the ester polymer is 100,000.

[0096] The structure of the prepared positive electrode plate is shown in Figure 1. From the first edge to the second edge, the positive electrode material layer includes an edge area and a main area in sequence. The width W1 of the edge area is 4 mm, and the width W2 of the main area is 80 mm; the thickness T1 of the edge area is 140 μm, and the thickness T2 of the main area is 150 μm. W1 / W2 is 5%, and T1 / T2 is 93%.

[0097] <Preparation of negative electrode sheet>

[0098] The negative electrode active material, artificial graphite, the conductive agent, acetylene black, the binder, styrene-butadiene rubber (SBR), and the thickener, sodium carboxymethyl cellulose, were mixed in a mass ratio of 95:2:2:1. Deionized water was added and the mixture was stirred thoroughly in a vacuum mixer to obtain a negative electrode slurry with a solid content of 75 wt%. The negative electrode slurry was evenly coated on one surface of a 12 μm thick negative electrode current collector copper foil and dried at 120°C to obtain a negative electrode sheet coated on one side with a negative electrode material layer. The above steps were repeated on the other surface of the copper foil to obtain a negative electrode sheet coated on both sides with a negative electrode material layer. The sheet was dried under vacuum at 120°C for 1 hour. After cold pressing, cutting, and slitting, a negative electrode sheet with a negative electrode active material layer measuring 88 mm x 875 mm was obtained.

[0099] <Preparation of Electrolyte>

[0100] In an argon atmosphere glove box with a water content of less than 10 ppm, the non-aqueous organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were mixed in a weight ratio of 1:1:1. The lithium salt lithium hexafluorophosphate (LiPF6) was then added and mixed thoroughly to form an electrolyte. The mass percentage of the lithium salt LiPF6, based on the mass of the electrolyte, was 12.5%.

[0101] <Isolation Film>

[0102] A porous polyethylene film with a thickness of 7 μm (provided by Celgard) was used as the separator.

[0103] <Preparation of lithium-ion batteries>

[0104] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to provide insulation. The electrodes are then wound to form an electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag, dried, and then filled with electrolyte. The lithium-ion battery is then produced through vacuum packaging, resting, formation, degassing, and trimming.

[0105] Example 1-2 to Example 1-20

[0106] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0107] Example 2-1

[0108] Except for adjusting the coating width so that the width of the edge area and the width of the main area are as shown in Table 2, adjusting the surface tension of the positive electrode current collector to 32 dyn / cm, and adjusting the relevant preparation parameters according to Table 2, the rest is the same as Example 1-1.

[0109] Example 2-2 to Example 2-4

[0110] Except that the coating weight was adjusted so that the thickness of the edge area and the thickness of the main area were as shown in Table 2, the rest was the same as Example 2-1.

[0111] Example 2-5 to Example 2-7

[0112] Except for adjusting the relevant preparation parameters according to Table 2, the rest is the same as Example 2-1.

[0113] Example 3-1

[0114] Except for adjusting the relevant preparation parameters according to Table 3, the rest is the same as Example 1-1.

[0115] Example 3-2 to Example 3-5

[0116] Except for adjusting the amount of organic silicon added so that the mass percentage of organic silicon is as shown in Table 3, the rest is the same as Example 3-1.

[0117] Example 3-6 to Example 3-9

[0118] Except for adjusting the amount of polyether added so that the mass percentage of polyether is as shown in Table 3, the rest is the same as Example 3-1.

[0119] Example 3-10 to Example 3-13

[0120] Except for adjusting the relevant preparation parameters according to Table 3, the rest is the same as Example 3-1.

[0121] Example 3-14 to Example 3-15

[0122] Except for adjusting the coating amount of the positive electrode slurry so that the coating weight of the positive electrode material layer is as shown in Table 3, the rest is the same as Example 3-1.

[0123] Example 3-16 to Example 3-17

[0124] Except that the cold pressing pressure in the cold pressing process was adjusted so that the compaction density of the positive electrode material layer was as shown in Table 3, the rest was the same as Example 3-1.

[0125] Comparative Example 1

[0126] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0127] Comparative Example 2

[0128] Except that polyvinyl pyrrolidone (PVP) was added instead of silicone and polyether-modified ester polymer in the preparation of the positive electrode sheet, the rest was the same as in Example 2-1.

[0129] The preparation parameters and electrode performance parameters of each embodiment and comparative example are shown in Tables 1 to 3.

[0130] Table 1 Note: In Table 1, the order of "positive electrode edge shrinkage or edge bulging degree" from small to large is: mild < general < medium < severe, among which "mild" means that the degree of positive electrode edge shrinkage or edge bulging is relatively light, and the processing performance is good; "severe" means that the degree of positive electrode edge shrinkage or edge bulging is relatively heavy, and the processing performance is poor. The same applies to other embodiments.

[0131] Table 2

[0132] As can be seen from Examples 1-1 to 1-20, Examples 2-1 to 2-7, and Comparative Examples 1 to 2, the positive electrode material layer includes an edge region and a main region, and the ratio of the width of the edge region to the width of the main region, the thickness of the edge region, the thickness of the main region, and the ratio of the thickness of the edge region to the thickness of the main region are within the range of this application. Furthermore, the positive electrode material layer includes silicone and polyether-modified ester polymers, and the silicone, polyether, and polymer main body of this application are selected. The angle of the edge region of the positive electrode plate is smaller, the G / T2 value is smaller, and the D-γ×cosθ value is smaller. The degree of edge shrinkage or edge bulging of the positive electrode plate is relatively mild, which can effectively improve the processing problem of edge shrinkage or edge bulging of the positive electrode plate during the coating process. In Comparative Example 1, however, the positive electrode material layer does not include silicone and polyether-modified ester polymers. The angle of the edge region of the positive electrode plate is larger, the G / T2 value is larger, and the D-γ×cosθ value is larger. The processing problem of edge shrinkage or edge bulging of the positive electrode plate during the coating process is more serious. It can be seen from Comparative Example 2 and Example 2-1 that the positive electrode material layer of Comparative Example 2 includes PVP, the angle of the edge area of ​​the positive electrode plate is larger, the value of G / T2 is larger, and the value of D-γ×cosθ is larger, indicating that the addition of silicone and polyether-modified ester polymers to the positive electrode material layer can more effectively improve the processing problems of edge shrinkage or edge bulging of the positive electrode plate during the coating process.

[0133] The mass percentage of ester polymers will affect the degree of edge shrinkage or edge bulging of the positive electrode plate during the coating process. From Examples 1-1 to 1-13, and 1-18 to 1-20, it can be seen that by regulating the mass percentage of ester polymers within the scope of this application, the angle of the edge area of ​​the positive electrode plate is smaller, the value of G / T2 is smaller, and the value of D-γ×cosθ is smaller, the degree of edge shrinkage or edge bulging of the positive electrode plate is relatively mild, and the processing problem of edge shrinkage or edge bulging of the positive electrode plate during the coating process can be effectively improved. The mass percentage of ester polymer in Example 1-19 is low, and the effect of improving the edge shrinkage or edge bulging of the positive electrode plate during the coating process is poor. The amount of ester polymer added and the improvement effect show an exponential distribution. The amount of ester polymer added in the early stage is small. As the amount added increases, the improvement effect is significantly improved. When the amount added continues to increase, the growth rate of the improvement effect will decrease. The ester polymer of Example 1-20 has a higher mass percentage, and is better in improving the edge shrinkage or edge bulging of the positive electrode during the coating process. However, compared with Examples 1-1 to 1-13 and 1-18, the improvement effect is not significant; and, if the mass percentage of the ester polymer is too high, it will affect the energy density of the lithium-ion battery.

[0134] The surface tension of the positive electrode current collector affects the degree of edge shrinkage or edge bulging that occurs during the coating process of the positive electrode sheet. As can be seen from Examples 1-11, 1-14, and 1-17, by regulating the surface tension of the positive electrode current collector within the scope of this application, the angle of the edge region of the positive electrode sheet is smaller, the value of G / T2 is smaller, and the value of D-γ×cosθ is smaller, resulting in relatively less edge shrinkage or edge bulging of the positive electrode sheet, which can effectively improve the processing issues of edge shrinkage or edge bulging that occur during the coating process of the positive electrode sheet.

[0135] The mass percentage of the ester polymer affects the surface tension of the positive electrode slurry. As can be seen from Examples 1-1 to 1-13, and 1-18 to 1-20, the mass percentage of the ester polymer is within the range of this application, and thus the surface tension of the positive electrode slurry is within this range. The angle of the edge of the positive electrode sheet is smaller, the G / T2 value is smaller, and the D-γ×cosθ value is smaller. The degree of edge shrinkage or edge bulging of the positive electrode sheet is relatively mild, which can effectively improve the processing issues of edge shrinkage or edge bulging that occur during the coating process of the positive electrode sheet.

[0136] As can be seen from FIG4 and FIG7 , compared with Comparative Example 1, the edge shrinkage of the positive electrode sheets of Examples 1-12 during the coating process is slight.

[0137] As can be seen from FIG5 and FIG7, compared with Comparative Example 1, the edge shrinkage of the positive electrode sheets of Examples 1-11 during the coating process is slight.

[0138] As can be seen from FIG6 and FIG7, compared with Comparative Example 1, the edge shrinkage of the positive electrode sheets of Examples 1-13 during the coating process is slight.

[0139] As can be seen from FIG7 and FIG4 , FIG5 , and FIG6 , compared with Examples 1-12, 1-11, and 1-13, the edge shrinkage of the positive electrode sheet of Comparative Example 1 during the coating process is more serious.

[0140] Table 3 Note: In Table 3, in Examples 3-5, the "degree of positive electrode sheet edge shrinkage or edge bulging" is "medium (edge ​​shrinkage)". The above "medium (edge ​​shrinkage)" means that the degree of positive electrode sheet edge shrinkage is medium and the degree of positive electrode sheet edge bulging is slight. The same applies to other examples.

[0141] The mass percentage of silicone and polyether affects the dispersibility of the ester polymer, thereby affecting the degree of edge shrinkage or bulging that occurs during the coating process of the positive electrode. As shown in Examples 3-1 to 3-9, by adjusting the mass percentage of silicone and polyether within the range of this application, the angle of the edge area of ​​the positive electrode plate is smaller, the G / T2 value is smaller, and the D-γ×cosθ value is smaller, resulting in relatively less edge shrinkage or bulging of the positive electrode plate, effectively improving the processing issues of edge shrinkage or bulging that occur during the coating process of the positive electrode plate.

[0142] The weight-average molecular weight of the ester polymer affects the degree of edge shrinkage or bulging that occurs during the coating process of the positive electrode sheet. As shown in Examples 3-1, 3-10, and 3-13, by adjusting the weight-average molecular weight of the ester polymer within the range of this application, the angle of the edge region of the positive electrode sheet is smaller, the G / T2 value is smaller, and the D-γ×cosθ value is smaller. This results in relatively less edge shrinkage or bulging of the positive electrode sheet, effectively improving the processing issues of edge shrinkage or bulging that occur during the coating process of the positive electrode sheet.

[0143] The coating weight of the positive electrode material layer affects the processing performance of the positive electrode sheet, the cycling performance, and the rate performance of the lithium-ion battery. As shown in Examples 3-1, 3-14, and 3-15, by adjusting the coating weight of the positive electrode material layer within the range of this application, the angle of the edge area of ​​the positive electrode sheet is smaller, the G / T2 value is smaller, and the D-γ×cosθ value is smaller, resulting in relatively less edge shrinkage or bulging of the positive electrode sheet.

[0144] The compaction density of the positive electrode material layer affects the processing performance of the positive electrode sheet, the cycling performance, and the rate performance of the lithium-ion battery. As shown in Examples 3-1, 3-16, and 3-17, by adjusting the compaction density of the positive electrode material layer within the scope of this application, the angle of the edge area of ​​the positive electrode sheet is smaller, the G / T2 value is smaller, and the D-γ×cosθ value is smaller, resulting in relatively less shrinkage or bulging of the edge of the positive electrode sheet.

[0145] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article comprising a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, or article.

[0146] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0147] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A positive electrode sheet comprising a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode current collector comprises a first edge and a second edge opposite to each other along the width direction of the positive electrode sheet. From the first edge to the second edge, the positive electrode material layer includes an edge region and a main region in sequence, the width of the edge region is W1 mm, the thickness of the edge region is T1 μm, the width of the main region is W2 mm, the thickness of the main region is T2 μm, W1 / W2≤8%, 90%≤T1 / T2≤100%, 18≤T1≤300, and 20≤T2≤300; The positive electrode material layer includes organic silicon and polyether-modified ester polymer.

2. The positive electrode sheet according to claim 1, wherein: The positive electrode sheet satisfies at least one of the following characteristics: (1) The organosilicon includes at least one of trisiloxane, polydimethylsiloxane, polyoxyethylene ether trisiloxane or vinyl trimethoxysilane; (2) the polyether comprises at least one of monoallyl polyether, allyl alcohol polyether, methyl allyl alcohol polyoxyethylene ether or lauryl alcohol polyether; (3) The polymer main body of the ester polymer includes at least one of polybutyl acrylate, polymethyl acrylate, polycarbonate, polyvinyl acetate or polyarylate; (4) Based on the mass of the positive electrode material layer, the mass percentage of the ester polymer is w1%, 0.05≤w1≤1.

3. The positive electrode sheet according to claim 1, wherein: Separating the positive electrode material layer from the positive electrode current collector to obtain positive electrode material layer powder, dissolving the positive electrode material layer powder in N-methylpyrrolidone to obtain a positive electrode slurry with a solid content of 60% to 80%, wherein the surface tension of the positive electrode slurry is γN / m; The surface tension of the positive electrode current collector is D dyn / cm, the angle of the edge region is θ, and 0≤D-γ×cosθ≤15.

4. The positive electrode sheet according to claim 3, wherein the positive electrode sheet satisfies at least one of the following characteristics: (1)26≤D≤39； (2)30≤γ≤45; (3)5°≤θ≤75°.

5. The positive electrode sheet according to claim 1, wherein: Based on the mass of the ester polymer, the mass percentage of the silicone is 10% to 25%, and the mass percentage of the polyether is 20% to 30%.

6. The positive electrode sheet according to claim 1, wherein: The weight average molecular weight Mw of the ester polymer is 10,000 to 200,000.

7. The positive electrode sheet according to claim 1, wherein: The positive electrode material layer satisfies at least one of the following characteristics: (1) The coating weight of the positive electrode material layer is CW, 100 mg / 1540.25 mm 2 ≤CW≤500mg / 1540.25mm 2 ; (2) The compaction density of the positive electrode material layer is PD g / cc, 2.0≤PD≤4.

0.

8. The positive electrode sheet according to claim 1, wherein: The bulge value of the positive electrode plate is G μm, and G / T2≤5%. 9 . A secondary battery comprising the positive electrode sheet according to claim 1 . 10 . An electronic device comprising the secondary battery according to claim 9 .

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