Positive electrode active material, positive electrode sheet, preparation method therefor and use thereof

Abstract

A positive electrode active material, a positive electrode sheet, a preparation method therefor and the use thereof. The positive electrode active material comprises a first positive electrode material and a second positive electrode material; the surface of the first positive electrode material has a first group, and the surface of the second positive electrode material has a second group, wherein the first group and the second group are independently at least one selected from -NH2, -C4H4O2, -COOH and -SH, and the first group and the second group can be bonded together; and the particle size of the first positive electrode material is greater than the particle size of the second positive electrode material.

Description

Cathode active material, cathode electrode sheet and preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202410411783.6, filed on April 7, 2024, and titled "Cathode active material, cathode electrode sheet and preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of batteries, in particular to a cathode active material, a cathode electrode sheet and a preparation method and application thereof. BACKGROUND

[0003] The cathode active material affects the energy density, cycle performance and preparation cost of the battery, and further affects the comprehensive performance of the battery. In the related art, by using cathode active materials of different particle sizes and adjusting the ratio of the cathode active materials of different particle sizes, the compaction density of the cathode electrode sheet can be improved, and the energy density of the battery can be further improved. However, the mixing uniformity between the cathode active materials of different particle sizes is poor, which has an adverse effect on the compaction density and energy efficiency of the cathode electrode sheet. Therefore, there is a need for a cathode active material with good mixing uniformity between different particle sizes. SUMMARY

[0004] In view of this, the present application provides a cathode active material, a cathode electrode sheet and a preparation method and application thereof. The cathode active material has cathode materials of different particle sizes, and the carbon coating layer surfaces of the cathode materials of different particle sizes have different groups. The cathode active material can realize directional mixing of the cathode materials of different particle sizes, improve the filling uniformity of the cathode active material, and improve the compaction density and energy density of the cathode electrode sheet, which is beneficial to the industrial application of the cathode active material.

[0005] In a first aspect, the present application provides a cathode active material, which includes a first cathode material and a second cathode material. The surface of the first cathode material has a first group, and the surface of the second cathode material has a second group. The first group and the second group are independently selected from at least one of -NH2, -C4H4O2, -COOH and -SH. The first group and the second group can be bonded and connected. The particle size of the first cathode material is greater than the particle size of the second cathode material.

[0006] Optionally, the first group and the second group can be bonded and connected by hydrogen bonds and / or chemical bonds.

[0007] Optionally, the particle size D50 of the first cathode material is 0.8 μm-1.5 μm.

[0008] Optionally, the particle size D50 of the second positive electrode material is less than or equal to 0.5 μm.

[0009] Optionally, the mass ratio of the first positive electrode material to the second positive electrode material is (9-7):(3-1).

[0010] Optionally, in the positive electrode active material, the mass percentage of the second positive electrode material is 10%-30%.

[0011] Optionally, in the first positive electrode material, the mass percentage of the first group is 1.1%-1.3%.

[0012] Optionally, in the second positive electrode material, the mass percentage of the second group is 1.1%-1.3%.

[0013] Optionally, the first positive electrode material comprises a first inner core and a first carbon coating layer arranged on the surface of the first inner core, the first carbon coating layer has a first group, and in the first positive electrode material, the mass percentage of the first carbon coating layer is 1.1%-1.3%.

[0014] Optionally, the second positive electrode material comprises a second inner core and a second carbon coating layer arranged on the surface of the second inner core, the second carbon coating layer has a second group, and in the second positive electrode material, the mass percentage of the second carbon coating layer is 1.1%-1.3%.

[0015] Optionally, the material of the first inner core and the second inner core is independently selected from at least one of lithium manganate, lithium cobaltate, lithium iron phosphate and a ternary material.

[0016] The positive electrode active material provided in the present application has positive electrode materials with different particle sizes, the surfaces of the positive electrode materials with different particle sizes have different groups, directional mixing and uniform filling of the positive electrode materials with different particle sizes can be achieved, the compaction density and energy density of the positive electrode sheet are improved, and the application of the positive electrode material is facilitated.

[0017] In a second aspect, the present application provides a preparation method of a positive electrode active material, comprising:

[0018] mixing a first positive electrode material source and a first modifier to form a first mixture, and obtaining a first positive electrode material after first sintering;

[0019] mixing a second positive electrode material source and a second modifier to form a second mixture, and obtaining a second positive electrode material after second sintering;

[0020] mixing the first positive electrode material and the second positive electrode material to obtain a positive electrode active material;

[0021] The positive electrode active material comprises the first positive electrode material and the second positive electrode material, a surface of the first positive electrode material has a first group, a surface of the second positive electrode material has a second group, the first group and the second group are independently selected from at least one of -NH2, -C4H4O2, -COOH and -SH, the first group and the second group can be bonded and connected, and a particle size of the first positive electrode material is greater than a particle size of the second positive electrode material.

[0022] Optionally, the first modifier and the second modifier are independently selected from at least one of CH3CH2COOH, CH3CH2CH2COOH, NH4Cl, (NH4)2SO4, NH4NO3, Na2SO4, H2SO4, CH3C4H4O2, C4H4O2, NH3·H2O and CH3COOH.

[0023] Optionally, the first mixture further comprises a first carbon source, and the second mixture further comprises a second carbon source, and the first carbon source and the second carbon source are independently selected from at least one of glucose, sucrose, citric acid, polyethylene glycol, carbon nanotubes and graphene.

[0024] Optionally, a mass ratio of the first positive electrode material source, the first modifier and the first carbon source is (2.52-2.58):(0.0038-0.0047):(6.5-6.7).

[0025] Optionally, a mass ratio of the second positive electrode material source, the second modifier and the second carbon source is (2.52-2.58):(0.0012-0.0025):(5.1-5.5).

[0026] Optionally, a temperature of the first sintering is 750-800℃, and a time of the first sintering is 15-20h.

[0027] Optionally, a temperature of the second sintering is 700-800℃, and a time of the second sintering is 3-7h.

[0028] The preparation method of the positive electrode active material provided in the application is novel, the preparation process is simple, and the positive electrode active material with high compaction density and excellent energy density can be prepared.

[0029] In a third aspect, the application provides a composite cathode material, the composite active material comprising a first cathode material and a second cathode material, the surface of the first cathode material having a first group, the surface of the second cathode material having a second group, the first group and the second group being independently selected from at least one of -NH2, -C4H4O2, -COOH and -SH, the first group and the second group being connected by a connecting group, the particle size of the first cathode material being larger than the particle size of the second cathode material.

[0030] Optionally, the first group, the connecting group and the second group are connected by hydrogen bonds and / or chemical bonds.

[0031] The composite cathode material provided by the application can connect the first cathode material and the second cathode material through the connecting group, form a conductive network on the surface of the composite cathode material, increase the number of conductive paths of the composite cathode material, reduce the polarization effect of the composite cathode material, improve the energy efficiency of the composite cathode material, and facilitate the wide application of the composite cathode material.

[0032] In a fourth aspect, the application provides a cathode sheet, the cathode sheet comprising a cathode active material layer, the cathode active material layer comprising the cathode active material of the first aspect or the cathode active material prepared by the preparation method of the second aspect or the composite cathode material of the third aspect.

[0033] Optionally, the compaction density of the cathode sheet is 2.6 g / cm 3 -2.7 g / cm 3 .

[0034] The cathode sheet provided by the application has high compaction density, small polarization and excellent comprehensive electrochemical performance, and facilitates the wide application of the cathode sheet.

[0035] In a fifth aspect, the application provides a preparation method of a cathode sheet, comprising:

[0036] mixing the cathode active material of the first aspect or the cathode active material prepared by the preparation method of the second aspect, a guiding agent and a solvent to obtain a cathode slurry;

[0037] coating and drying the cathode slurry to obtain the cathode sheet.

[0038] Optionally, in the cathode slurry, the mass percentage of the guiding agent is 1%-2%.

[0039] Optionally, the guiding agent comprises at least one of an iron-based macromolecular titanium cyanin compound, polyacetylene, polythiophene and polymeric aniline.

[0040] The positive electrode tab provided by the application has simple preparation method, convenient operation, high production efficiency, can realize large-scale production of the positive electrode tab, and is beneficial to use of the positive electrode tab.

[0041] In a sixth aspect, the application provides a battery, which comprises a negative electrode tab and the positive electrode tab provided in the fourth aspect or prepared by the preparation method provided in the fifth aspect.

[0042] The battery provided by the application has high energy density, low preparation cost, short cycle, excellent comprehensive electrical performance, and is beneficial to improve product competitiveness of the battery.

[0043] In a seventh aspect, the application provides a power consumption device, which comprises the battery provided in the sixth aspect.

[0044] The power consumption device provided by the application has excellent comprehensive performance, and is beneficial to wide application of the power consumption device. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. The specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0046] Fig. 1 is a schematic cross-sectional view of a positive electrode active material provided by an embodiment of the application;

[0047] Fig. 2 is a flowchart of a preparation method of the positive electrode active material provided by an embodiment of the application;

[0048] Fig. 3 is a schematic view of a connection mode inside a composite positive electrode material provided by an embodiment of the application;

[0049] Fig. 4 is a schematic cross-sectional view of a positive electrode tab provided by an embodiment of the application;

[0050] Fig. 5 is a flowchart of a preparation method of the positive electrode tab provided by an embodiment of the application.

[0051] Explanation of reference signs: 100-positive electrode active material; 10-first positive electrode material; 20-second positive electrode material; 11-first inner core; 12-first carbon coating layer; 21-second inner core; 22-second carbon coating layer; 13-first group; 23-second group; 30-linking group; 200-positive electrode tab; 40-positive electrode current collector; 50-positive electrode active material layer. DETAILED DESCRIPTION

[0052] In the following, the technical solutions in the embodiments of the present application will be described clearly and completely with the drawings 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. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort fall within the protection scope of the present application.

[0053] The present application provides a positive electrode active material, the positive electrode active material comprises a first positive electrode material and a second positive electrode material, the surface of the first positive electrode material has a first group, the surface of the second positive electrode material has a second group, the first group and the second group are independently selected from at least one of -NH2, -C4H4O2, -COOH and -SH, the first group and the second group can be bonded and connected, the particle size of the first positive electrode material is larger than the particle size of the second positive electrode material. The particle size matching of the first positive electrode material with large particle size and the second positive electrode material with small particle size in the positive electrode active material provided by the present application can improve the compaction density of the positive electrode sheet; the surfaces of the first positive electrode material and the second positive electrode material have different groups, and the small particle size second positive electrode material can be realized by the interaction of the first group and the second group. The surface of the large particle size first positive electrode material is surrounded, so as to realize the directional mixing and uniform filling of positive electrode materials with different particle sizes, which can avoid the problem of poor dispersion of positive electrode materials with different particle sizes caused by directly mixing positive electrode materials with large particle size and small particle size, and cannot effectively improve the compaction density of the positive electrode sheet, which is beneficial to further improve the compaction density and energy density of the positive electrode sheet. Since the positive electrode active material with large particle size will cause the polarization effect of the positive electrode sheet to be enhanced, resulting in the decline of the electrochemical performance of the battery, in the related technology, the polarization effect is reduced and the energy efficiency is improved by doping and coating modification of the positive electrode active material, and the particle size ratio of the positive electrode active material is regulated to improve the compaction density of the positive electrode sheet, but in actual preparation, it is difficult to balance the compaction density and energy efficiency of the positive electrode sheet, and the preparation period is long, which is not conducive to the industrial application of the positive electrode active material. The small particle size positive electrode active material is prone to dropping during coating, which is not conducive to improving the processing cost, and at the same time, the performance of the battery is deteriorated, which may also cause safety problems; the surfaces of the first positive electrode material and the second positive electrode material in the positive electrode active material provided by the present application have different groups, and the different groups can form a conductive network with excellent conductive performance on the surface of the positive electrode active material, which is helpful to improve the kinetic performance of the positive electrode sheet, reduce the positive electrode polarization effect, and improve the energy efficiency of the battery. Therefore, the positive electrode active material of the present application can realize the directional mixing of positive electrode materials with different particle sizes, improve the kinetic performance, compaction density and energy density of the positive electrode sheet, reduce the electrode polarization, and further improve the energy efficiency of the battery.

[0054] Referring to FIG. 1, a cross-sectional schematic diagram of a positive electrode active material according to an embodiment of the present application is provided, the positive electrode active material 100 includes a first positive electrode material 10 and a second positive electrode material 20, the first positive electrode material 10 includes a first inner core 11 and a first carbon coating layer 12 arranged on the surface of the first inner core 11, the first carbon coating layer 12 has a first group; the second positive electrode material 20 includes a second inner core 21 and a second carbon coating layer 22 arranged on the surface of the second inner core 21, the second carbon coating layer 22 has a second group; the first group and the second group are independently selected from at least one of -NH2, -C4H4O2, -COOH and -SH, the first group and the second group can be bonded and connected, the particle size of the first positive electrode material is larger than the particle size of the second positive electrode material. Wherein, the first carbon coating layer and the second carbon coating layer can improve the stability and conductivity of the positive electrode active material.

[0055] In the present application, the first positive electrode material includes a first inner core, which can improve the specific capacity and cycle stability of the positive electrode active material, and is beneficial to improve the energy density of the positive electrode sheet. Specifically, the material of the first inner core can include at least one of lithium manganate, lithium cobaltate, lithium iron phosphate and ternary materials (such as nickel cobalt manganese, nickel cobalt aluminum, etc.). In an embodiment of the present application, the material of the first inner core can be lithium iron phosphate, which can improve the structural stability of the positive electrode active material and reduce the preparation cost and the cost per kilowatt of the positive electrode sheet. In another embodiment of the present application, the material of the first inner core can be lithium cobaltate.

[0056] In an embodiment of the present application, a first carbon coating layer is arranged on the surface of the first inner core, which can improve the conductivity of the positive electrode active material, enhance the electron transport capacity, and at the same time provide a connection site for the first group. In an embodiment of the present application, the mass percentage of the first carbon coating layer in the first positive electrode material is 1.1%-1.3%, which can improve the structural stability of the first positive electrode material. Specifically, the mass percentage of the first carbon coating layer in the first positive electrode material can be 1.1%, 1.12%, 1.14%, 1.15%, 1.18%, 1.2%, 1.22%, 1.25%, 1.28% or 1.3%, etc. In an embodiment of the present application, the mass percentage of the first carbon coating layer in the first positive electrode material can be 1.1%-1.22%. In another embodiment of the present application, the mass percentage of the first carbon coating layer in the first positive electrode material can be 1.2%-1.3%.

[0057] In an embodiment of the present application, the surface of the first carbon coating layer is provided with a first group, the first group can be connected with a second group to realize the directional mixing of the first positive electrode material and the second positive electrode material, promote the uniform filling of the positive electrode active material, and improve the compaction density of the positive electrode sheet. At the same time, a conductive network can also be formed on the surface of the positive electrode active material, increase the conductive path, improve the conductivity and kinetic performance of the positive electrode active material, reduce the polarization of the positive electrode sheet, and improve the electrochemical performance of the battery. Specifically, the first group can be, but is not limited to, at least one of -NH2, -C4H4O2, -COOH and -SH. In an embodiment of the present application, the first group can be -NH2. In another embodiment of the present application, the first group can be -C4H4O2.

[0058] In an embodiment of the present application, the mass percentage of the first group in the first positive electrode material is 1.1%-1.3%. Specifically, the mass percentage of the first group in the first positive electrode material can be 1.1%, 1.12%, 1.14%, 1.15%, 1.18%, 1.2%, 1.22%, 1.25%, 1.28% or 1.3%, etc. In an embodiment of the present application, the mass percentage of the first group in the first positive electrode material can be 1.1%-1.22%. In another embodiment of the present application, the mass percentage of the first group in the first positive electrode material can be 1.2%-1.3%.

[0059] In an embodiment of the present application, the particle size D50 of the first positive electrode material is 0.8-1.5 μm, and the first positive electrode material with larger particle size can improve the tap density of the positive electrode active material, and further improve the compaction density and energy density of the positive electrode sheet. Specifically, the particle size D50 of the first positive electrode material can be, but is not limited to, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm, etc. In an embodiment of the present application, the particle size D50 of the first positive electrode material can be 0.8-1.1 μm. In another embodiment of the present application, the particle size D50 of the first positive electrode material can be 1-1.5 μm.

[0060] In an embodiment of the present application, the mass percentage of the first positive electrode material in the positive electrode active material is 70%-90%, which can improve the tap density of the positive electrode active material, and further improve the compaction density and energy density of the positive electrode sheet. Specifically, the mass percentage of the first positive electrode material can be 70%, 75%, 78%, 80%, 84%, 88% or 90%, etc. In an embodiment of the present application, the mass percentage of the first positive electrode material can be 70%-83%. In another embodiment of the present application, the mass percentage of the first positive electrode material can be 75%-90%.

[0061] In the present application, the second positive electrode material includes a second inner core, which can improve the specific capacity and cycle stability of the positive electrode active material, and is beneficial to improve the energy density of the positive electrode sheet. Specifically, the material of the second inner core can include at least one of lithium manganate, lithium cobaltate, lithium iron phosphate, and ternary materials (such as nickel-cobalt-manganese, nickel-cobalt-aluminum, etc.). In an embodiment of the present application, the material of the second inner core can be lithium iron phosphate, which can improve the structural stability of the positive electrode active material, reduce the preparation cost and the cost per kilowatt-hour of the positive electrode sheet. In another embodiment of the present application, the material of the second inner core can be lithium cobaltate. In some embodiments, the material of the first inner core is the same as that of the second inner core, which can further improve the stability and conductivity of the positive electrode active material, improve the energy density of the positive electrode sheet, and further improve the energy efficiency of the battery.

[0062] In an embodiment of the present application, the surface of the second inner core is provided with a second carbon coating layer, which can improve the conductivity of the positive electrode active material, enhance the electron transport capacity, and provide connection sites for the second group.

[0063] In an embodiment of the present application, the mass percentage of the second carbon coating layer in the second positive electrode material is 1.1%-1.3%, which can improve the structural stability of the second positive electrode material. Specifically, the mass percentage of the second carbon coating layer in the second positive electrode material can be 1.1%, 1.12%, 1.14%, 1.15%, 1.18%, 1.2%, 1.22%, 1.25%, 1.28%, or 1.3%, etc. In an embodiment of the present application, the mass percentage of the second carbon coating layer in the second positive electrode material can be 1.1%-1.22%. In another embodiment of the present application, the mass percentage of the second carbon coating layer in the second positive electrode material can be 1.2%-1.3%.

[0064] In an embodiment of the present application, the surface of the second carbon coating layer is provided with a second group, which can be connected with the first group to realize the directional mixing of the first positive electrode material and the second positive electrode material, promote the uniform filling of the positive electrode active material, and improve the compaction density of the positive electrode sheet. At the same time, it can also form a conductive network on the surface of the positive electrode active material, increase the conductive path, improve the conductivity and kinetic performance of the positive electrode active material, reduce the polarization of the positive electrode sheet, and improve the electrochemical performance of the battery. Specifically, the second group can include at least one of -NH2, -C4H4O2, -COOH, and -SH, but is not limited thereto. In an embodiment of the present application, the second group can be -COOH. In another embodiment of the present application, the second group can be -SH.

[0065] In an embodiment of the present application, the mass percentage of the second group in the second positive electrode material is 1.1% to 1.3%. Specifically, the mass percentage of the second group in the second positive electrode material can be 1.1%, 1.12%, 1.14%, 1.15%, 1.18%, 1.2%, 1.22%, 1.25%, 1.28%, or 1.3%, etc. In an embodiment of the present application, the mass percentage of the second group in the second positive electrode material can be 1.1% to 1.22%. In another embodiment of the present application, the mass percentage of the second group in the second positive electrode material can be 1.2% to 1.3%.

[0066] In an embodiment of the present application, the first group and the second group can be bonded and connected, and the first group and the second group are easy to form a conductive network, increase the conductive path, reduce the polarization effect, and improve the electrochemical performance of the battery. Specifically, the second group can be, but is not limited to, at least one of -NH2, -C4H4O2, -COOH, and -SH. In an embodiment of the present application, the first group is -NH2 or -C4H4O2, and the second group can be -COOH or -SH.

[0067] In an embodiment of the present application, the particle size D50 of the second positive electrode material is less than or equal to 0.5 μm, and the second positive electrode material with small particle size can be filled between the first positive electrode materials, promote the uniform filling of the positive electrode active material, and further improve the compaction density and energy density of the positive electrode sheet. Specifically, the particle size D50 of the second positive electrode material can be, but is not limited to, less than or equal to 0.5 μm, less than or equal to 0.4 μm, less than or equal to 0.3 μm, less than or equal to 0.2 μm, less than or equal to 0.15 μm, or less than or equal to 0.1 μm, etc. In an embodiment of the present application, the particle size D50 of the second positive electrode material can be less than or equal to 0.25 μm. In another embodiment of the present application, the particle size D50 of the second positive electrode material can be less than or equal to 0.1 μm.

[0068] In an embodiment of the present application, the particle size D50 of the first positive electrode material is 0.8-1.5 μm, and the particle size D50 of the second positive electrode material is less than or equal to 0.3 μm, so as to further promote the uniform mixing of the positive electrode active material and improve the compaction density and energy density of the positive electrode sheet. Specifically, the particle size D50 of the first positive electrode material can be, but is not limited to, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm, etc.; and the particle size D50 of the second positive electrode material can be, but is not limited to, less than or equal to 0.3 μm, less than or equal to 0.28 μm, less than or equal to 0.25 μm, less than or equal to 0.2 μm, less than or equal to 0.15 μm, or less than or equal to 0.1 μm, etc. In an embodiment of the present application, the particle size D50 of the first positive electrode material is 0.8-1.5 μm, and the particle size D50 of the second positive electrode material is less than or equal to 0.3 μm.

[0069] The D50 above is the particle size corresponding to the cumulative particle size distribution volume percentage of 50%. The physical meaning is that the volume of particles with a particle size greater than the particle size D50 accounts for 50%, and the volume of particles with a particle size less than the particle size D50 also accounts for 50%. The D50 is also called the median diameter or median particle size.

[0070] When the particle size D50 of the first positive electrode material and / or the second positive electrode material is determined, the test method specifically includes the following steps: a) disassembling the fully discharged battery to obtain a positive electrode sheet, and then cutting any position of the application area by argon ions to obtain a positive electrode sheet cross-section sample; b) placing the positive electrode sheet cross-section sample in a SEM for observation, adjusting the electron microscope voltage and magnification according to the actual needs to ensure that enough particles in the sample can be clearly seen and photographed to obtain a SEM photo; c) the obtained SEM photo can be imported into a gray scale debugging software (such as Geodict) to statistically analyze the particle size, or the particle size can be directly recognized and counted by the naked eye; d) 20-30 experiments are cumulatively performed, and the number of particles counted in each experiment is not less than 500 pcs. After the results are counted, the particle size D50 of the first positive electrode material and / or the second positive electrode material in the positive electrode sheet is obtained.

[0071] In an embodiment of the present application, the mass percentage of the second positive electrode material in the positive electrode active material is 10%-30%, so as to improve the compaction density and energy density of the positive electrode active material. Specifically, the mass percentage of the second positive electrode material can be 10%, 15%, 18%, 20%, 24%, 28% or 30%, etc. In an embodiment of the present application, the mass percentage of the second positive electrode material can be 10%-25%. In another embodiment of the present application, the mass percentage of the second positive electrode material can be 15%-30%.

[0072] The positive electrode active material in the present application can include a plurality of first positive electrode materials and a plurality of second positive electrode materials. In an embodiment of the present application, the mass ratio of the first positive electrode material to the second positive electrode material is (9-7):(3-1), and the mass proportion of the first positive electrode material is high, which can improve the compaction density of the positive electrode sheet. Specifically, the mass ratio of the first positive electrode material to the second positive electrode material can be, but is not limited to, 9:3, 9:1.5, 9:1, 8:1, 8:1.5, 8:3, 7:1, 7:1.5, or 7:3, etc. In an embodiment of the present application, the mass ratio of the first positive electrode material to the second positive electrode material can be (8-7):(2.5-1). In another embodiment of the present application, the mass ratio of the first positive electrode material to the second positive electrode material can be (9-8):(3-2).

[0073] In an embodiment of the present application, the tap density of the positive electrode active material is 0.8 g / cm 3 -1.0 g / cm 3 . In this way, the compaction density of the positive electrode active material can be improved, and the energy density of the positive electrode sheet can be improved. Specifically, the tap density of the positive electrode active material can be, but is not limited to, 0.8 g / cm 3 , 0.82 g / cm 3 , 0.84 g / cm 3 , 0.86 g / cm 3 , 0.88 g / cm 3 , 0.9 g / cm 3 , 0.95 g / cm 3 , 0.98 g / cm 3 , or 1.0 g / cm 3 , etc. In an embodiment of the present application, the tap density of the positive electrode active material can be 0.8 g / cm 3 -0.89 g / cm 3 . In another embodiment of the present application, the tap density of the positive electrode active material can be 0.86 g / cm 3 -1.0 g / cm 3 .

[0074] Please refer to FIG. 2, which is a flow chart of a preparation method of the positive electrode active material provided in an embodiment of the present application, including:

[0075] S101: mixing a first positive electrode material source and a first modifier to form a first mixture, and obtaining a first positive electrode material after first sintering;

[0076] S102: mixing a second positive electrode material source and a second modifier to form a second mixture, and obtaining a second positive electrode material after second sintering;

[0077] S103: mixing the first positive electrode material and the second positive electrode material to obtain a positive electrode active material.

[0078] The preparation method provided in the application is novel, the preparation process is simple, the positive electrode active material with different particle size ratios can be prepared, the positive electrode material with different particle sizes has different groups on the surface, the directional mixing and uniform filling of the positive electrode material with different particle sizes can be realized, and the compaction density and energy density of the positive electrode sheet are improved. The positive electrode active material of any one of the embodiments can be prepared by the preparation method.

[0079] In the application, the first positive electrode material source is used to form the first inner core, the selection of the first positive electrode material source is related to the material of the first inner core, and the first positive electrode material source includes all metal elements in the material of the first inner core. Specifically, the first positive electrode material source can include but is not limited to at least one of a lithium source, a phosphorus source, an iron source, a cobalt source, a nickel source, a manganese source and an aluminum source. In an embodiment of the application, when the material of the first inner core is lithium iron phosphate, the first positive electrode material source includes a lithium source, an iron source and a phosphorus source. In another embodiment of the application, when the material of the first inner core is lithium cobaltate, the first positive electrode material source includes a lithium source and a cobalt source. Specifically, the lithium source can include but is not limited to at least one of Li2CO3, LiOH, CH3COOLi, Li3PO4 and Li2SO4; the iron source can include but is not limited to at least one of FeSO4, FeC2O4, FeCl3, Fe2O3 and Fe3O4; and the phosphorus source can include but is not limited to at least one of H3PO4, NH4H2PO4, (NH4)2HPO4, Na2HPO4 and NaH2PO4. In an embodiment of the application, the lithium source can be Li2CO3, the iron source can be Fe2O3, and the phosphorus source can be NH4H2PO4. In another embodiment of the application, the lithium source can be LiOH, the iron source can be FeC2O4, and the phosphorus source can be NaH2PO4.

[0080] In an embodiment of the application, when the first positive electrode material source includes a phosphorus source, a lithium source and an iron source, the mass ratio of the phosphorus source, the lithium source and the iron source is (0.52-0.58):1:1, so that the positive electrode active material with excellent conductivity can be obtained. Specifically, the mass ratio of the phosphorus source, the lithium source and the iron source can include but is not limited to 0.52:1:1, 0.53:1:1, 0.54:1:1, 0.55:1:1, 0.56:1:1, 0.57:1:1 or 0.58:1:1, etc. In an embodiment of the application, the mass ratio of the phosphorus source, the lithium source and the iron source can be (0.52-0.55):1:1. In another embodiment of the application, the mass ratio of the phosphorus source, the lithium source and the iron source is (0.54-0.58):1:1.

[0081] In the present application, the first modifier grafts the first group on the surface of the first positive electrode material to improve the conductivity of the positive electrode active material, promote the uniformity of the positive electrode active material, improve the compaction density of the positive electrode sheet, and reduce the polarization of the positive electrode sheet. Specifically, the corresponding first modifier can be selected according to the required first group. For example, the first modifier can include, but is not limited to, at least one of NH4Cl, (NH4)2SO4, NH4NO3, CH3C4H4O2, C4H4O2, NH3·H2O, CH3CH2COOH, CH3CH2CH2COOH, Na2SO4, H2SO4, and CH3COOH, and the corresponding modified group is at least one of -NH2, -C4H4O2, -COOH, and -SH. In an embodiment of the present application, the first modifier can be NH4Cl, and the first group is -NH2. In another embodiment of the present application, the first modifier can be C4H4O2, and the first group is -C4H4O2. In some embodiments, the first modifier can be a first carbon layer modifier, which grafts the first group on the surface of the first carbon coating layer, and can further improve the conductivity of the positive electrode active material.

[0082] In an embodiment of the present application, the first mixture further includes a first carbon source for forming a first carbon coating layer to improve the conductivity of the positive electrode active material. In an embodiment of the present application, the first carbon source includes at least one of an organic carbon source and an inorganic carbon source. Specifically, the first carbon source can include, but is not limited to, at least one of glucose, sucrose, citric acid, polyethylene glycol, carbon nanotubes, and graphene. In an embodiment of the present application, the first carbon source can be glucose and sucrose. In another embodiment of the present application, the first carbon source can be carbon nanotubes.

[0083] In an embodiment of the present application, the mass ratio of the first positive electrode material source, the first modifier and the first carbon source is (2.52-2.58):(0.0038-0.0047):(6.5-6.7), so as to ensure that the positive electrode plate has high compaction density and energy efficiency. Specifically, the mass ratio of the first positive electrode material source, the first modifier and the first carbon source can be, but is not limited to, 2.52:0.0038:6.5, 2.53:0.004:6.55, 2.54:0.0042:6.58, 2.55:0.0044:6.6, 2.56:0.0045:6.65, 2.57:0.0047:6.7 or 2.58:0.0047:6.7, etc. In an embodiment of the present application, the mass ratio of the first positive electrode material source, the first modifier and the first carbon source can be (2.52-2.54):(0.0038-0.0042):(6.5-6.68). In another embodiment of the present application, the mass ratio of the first positive electrode material source, the first modifier and the first carbon source can be (2.54-2.58):(0.004-0.0047):(6.65-6.7).

[0084] In an embodiment of the present application, the first mixture further comprises a first doping modifier. The first doping modifier can perform doping modification on the first positive electrode material source, improve the conductivity of the positive electrode active material, and at the same time, the first doping modifier can affect the cell parameter, so as to control the particle size of the first positive electrode material, which is beneficial to reduce the battery impedance. Specifically, the first doping modifier can be, but is not limited to, at least one of tetrabutyl titanate, TiO2, V2O5, MgCl2, MgSO4 and MnSO4. In an embodiment of the present application, the first doping modifier can be TiO2. In another embodiment of the present application, the first doping modifier can be MgCl2.

[0085] In an embodiment of the present application, the mass ratio of the first positive electrode material source, the first modifier, the first doping modifier and the first carbon source is (2.52-2.58):(0.0038-0.0047):(0.0001-0.0005):(6.5-6.7). Specifically, the mass ratio of the first positive electrode material source, the first modifier, the first doping modifier and the first carbon source can be, but is not limited to, 2.52:0.0038:0.0001:6.5, 2.53:0.004:0.0002:6.55, 2.54:0.0042:0.00025:6.58, 2.55:0.0044:0.0003:6.6, 2.56:0.0045:0.00035:6.65, 2.57:0.0047:0.0004:6.7 or 2.58:0.0047:0.0005:6.7, etc. In an embodiment of the present application, the mass ratio of the first positive electrode material source, the first modifier, the first doping modifier and the first carbon source can be (2.52-2.55):(0.0038-0.0042):(0.0001-0.00032):(6.5-6.63). In another embodiment of the present application, the mass ratio of the first positive electrode material source, the first modifier, the first doping modifier and the first carbon source can be (2.54-2.58):(0.0041-0.0047):(0.0003-0.0005):(6.6-6.7).

[0086] In an embodiment of the present application, the temperature of the first sintering is 750-800°C. Specifically, the temperature of the first sintering can be, but is not limited to, 750°C, 760°C, 770°C, 780°C, 790°C or 800°C, etc. In an embodiment of the present application, the temperature of the first sintering can be 750-770°C. In another embodiment of the present application, the temperature of the first sintering can be 760-800°C.

[0087] In an embodiment of the present application, the time of the first sintering is 15-20h. Specifically, the time of the first sintering can be, but is not limited to, 15h, 16h, 16.5h, 17h, 18h, 19h or 20h, etc. In an embodiment of the present application, the time of the first sintering can be 15-18h. In another embodiment of the present application, the time of the first sintering can be 16-20h.

[0088] In an embodiment of the present application, after the first positive electrode material source, the first modifier and the first carbon source are mixed and stirred, the first sintering is performed. Specifically, the time of stirring can be, but is not limited to, 6h, 6.5h, 7h, 7.5h, 8h, 9h or 10h, etc. In an embodiment of the present application, the time of stirring can be 6-8h. In another embodiment of the present application, the time of stirring can be 7-10h.

[0089] In an embodiment of the present application, the preparation method of the first positive electrode material can include, but is not limited to, at least one of a solid phase method, a liquid phase method, a sol-gel method, and a spray drying method. In an embodiment of the present application, the preparation method of the first positive electrode material is a solid phase method, which can obtain the first positive electrode material with a large particle size, and is beneficial to improve the compaction density and energy density of the positive electrode active material. For example, the first positive electrode material source, the first modifier, and the first carbon source are added into a first solvent to mix, stir, and grind to form a first mixture, the first solvent is removed by spray drying, and the first sintering is performed to obtain the first positive electrode material. In some embodiments, the first solvent can be an aqueous solution.

[0090] In the present application, the second positive electrode material source is used to form the second inner core, the selection of the second positive electrode material source is related to the material of the second inner core, and the second positive electrode material source includes all metal elements in the material of the second inner core. Specifically, the second positive electrode material source can include, but is not limited to, at least one of a lithium source, a phosphorus source, an iron source, a cobalt source, a nickel source, a manganese source, and an aluminum source. In an embodiment of the present application, when the material of the second inner core is lithium iron phosphate, the second positive electrode material source includes a lithium source, an iron source, and a phosphorus source. In another embodiment of the present application, when the material of the second inner core is lithium cobaltate, the second positive electrode material source includes a lithium source and a cobalt source.

[0091] In an embodiment of the present application, when the second positive electrode material source includes a phosphorus source, a lithium source, and an iron source, the mass ratio of the phosphorus source, the lithium source, and the iron source is (0.52-0.58):1:1. Specifically, the mass ratio of the phosphorus source, the lithium source, and the iron source can be, but is not limited to, 0.52:1:1, 0.53:1:1, 0.54:1:1, 0.55:1:1, 0.56:1:1, 0.57:1:1, or 0.58:1:1, etc. In an embodiment of the present application, the mass ratio of the phosphorus source, the lithium source, and the iron source can be (0.52-0.55):1:1. In another embodiment of the present application, the mass ratio of the phosphorus source, the lithium source, and the iron source is (0.54-0.58):1:1.

[0092] In the present application, the second modifier grafts the second group on the surface of the second carbon coating layer to improve the conductivity of the positive electrode active material, promote the uniformity of the positive electrode active material, increase the compaction density of the positive electrode sheet, and reduce the polarization of the positive electrode sheet. Since the first group and the second group cannot be the same, the same group cannot form a conductive polymer and cannot form a conductive network, which leads to an increase in the polarization of the positive electrode active material and a decrease in the energy efficiency of the battery. That is, the selection of the second modifier cannot be the same as that of the first modifier. When the first modifier is NH4Cl, (NH4)2SO4, NH4NO3, CH3C4H4O2 (i.e., acetylacetone), C4H4O2 (i.e., methyl methacrylate), NH3·H2O, etc., the second modifier is selected from CH3CH2COOH, CH3CH2CH2COOH, Na2SO4, H2SO4, CH3COOH, etc. Specifically, the corresponding second modifier can be selected according to the required second group. For example, the second modifier can include, but is not limited to, at least one of NH4Cl, (NH4)2SO4, NH4NO3, CH3C4H4O2 (i.e., acetylacetone), C4H4O2 (i.e., methyl methacrylate), NH3·H2O, CH3CH2COOH, CH3CH2CH2COOH, Na2SO4, H2SO4, and CH3COOH. In an embodiment of the present application, the second modifier can be CH3CH2COOH, and the second group is -COOH. In another embodiment of the present application, the second modifier can be Na2SO4, and the second group is -SH. In some embodiments, the second modifier can be a second carbon layer modifier, which grafts the second group on the surface of the second carbon coating layer, and can further improve the conductivity of the positive electrode active material.

[0093] In the present application, the second carbon source is used to form the second carbon coating layer to improve the conductivity of the positive electrode active material. In an embodiment of the present application, the second carbon source includes at least one of an organic carbon source and an inorganic carbon source. Specifically, the second carbon source can include, but is not limited to, at least one of glucose, sucrose, citric acid, polyethylene glycol, carbon nanotubes, and graphene. In an embodiment of the present application, the second carbon source can be glucose. In another embodiment of the present application, the second carbon source can be carbon nanotubes.

[0094] In an embodiment of the present application, the mass ratio of the second positive electrode material source, the second modifier and the second carbon source is (2.52-2.58):(0.0012-0.0025):(5.1-5.5), so as to ensure that the positive electrode plate has high compaction density and energy efficiency. Specifically, the mass ratio of the second positive electrode material source, the second modifier and the second carbon source can be, but is not limited to, 2.52:0.0012:5.1, 2.53:0.0015:5.15, 2.54:0.0016:5.2, 2.55:0.0018:5.3, 2.56:0.002:5.4, 2.57:0.0022:5.45 or 2.58:0.0025:5.5, etc. In an embodiment of the present application, the mass ratio of the second positive electrode material source, the second modifier and the second carbon source can be (2.52-2.54):(0.0012-0.0019):(5.1-5.4). In another embodiment of the present application, the mass ratio of the second positive electrode material source, the second modifier and the second carbon source can be (2.54-2.58):(0.0018-0.0025):(5.2-5.5).

[0095] In an embodiment of the present application, the second mixture further comprises a second doping modifier, which can be used to dope and modify the second inner core, so as to improve the conductivity of the positive electrode active material; and the particle size of the second positive electrode material can be controlled by changing the cell parameters, so as to reduce the battery impedance. Specifically, the second doping modifier can be, but is not limited to, at least one of tetrabutyl titanate, TiO2, V2O5, MgCl2, MgSO4 and MnSO4. In an embodiment of the present application, the second doping modifier can be TiO2. In another embodiment of the present application, the second doping modifier can be MgCl2.

[0096] In an embodiment of the present application, the mass ratio of the second positive electrode material source, the second modifier, the second doping modifier and the second carbon source is (2.52-2.58):(0.0012-0.0025):(0.0001-0.0005):(5.1-5.5). Specifically, the mass ratio of the second positive electrode material source, the second modifier, the second doping modifier and the second carbon source can be, but is not limited to, 2.52:0.0012:0.0001:5.1, 2.53:0.0015:0.0002:5.15, 2.54:0.0018:0.00025:5.2, 2.55:0.0019:0.0003:5.25, 2.56:0.002:0.00035:5.3, 2.57:0.0023:0.0004:5.4 or 2.58:0.0025:0.0005:5.5, etc. In an embodiment of the present application, the mass ratio of the second positive electrode material source, the second modifier, the second doping modifier and the second carbon source can be (2.52-2.55):(0.0012-0.0017):(0.0001-0.00032):(5.1-5.3). In another embodiment of the present application, the mass ratio of the second positive electrode material source, the second modifier, the second doping modifier and the second carbon source can be (2.54-2.58):(0.0015-0.0025):(0.0003-0.0005):(5.25-5.5).

[0097] In an embodiment of the present application, the preparation method of the second positive electrode material can include, but is not limited to, at least one of a solid phase method, a liquid phase method, a sol-gel method and a spray drying method. In an embodiment of the present application, the preparation method of the second positive electrode material is a liquid phase method, which can obtain a second positive electrode material with a smaller particle size, which is beneficial to improve the filling degree and the compaction density of the positive electrode active material. For example, the second positive electrode material source, the second modifier and the second carbon source are added into a second solvent for mixing, and then the mixture is heat treated, washed and dried, and then second sintering is performed to obtain the second positive electrode material. In some embodiments, the second solvent can be an aqueous solution.

[0098] In an embodiment of the present application, the temperature of the second sintering is 700-800°C. Specifically, the temperature of the second sintering can be, but is not limited to, 700°C, 720°C, 740°C, 760°C, 780°C or 800°C, etc. In an embodiment of the present application, the temperature of the second sintering can be 700-770°C. In another embodiment of the present application, the temperature of the second sintering can be 730-800°C.

[0099] In an embodiment of the present application, the second sintering time is 3h-7h. Specifically, the second sintering time can be, but is not limited to, 3h, 3.5h, 4h, 4.5h, 5h, 6h or 7h, etc. In an embodiment of the present application, the second sintering time can be 3h-5.5h. In another embodiment of the present application, the second sintering time can be 4h-7h.

[0100] In an embodiment of the present application, the second sintering further comprises a heat treatment, the heat treatment temperature is 100℃-200℃, and the heat treatment time is 8h-12h, which can promote the synthesis of the second positive electrode material. Specifically, the heat treatment temperature can be, but is not limited to, 100℃, 120℃, 140℃, 160℃, 180℃, 190℃ or 200℃, etc.; and the heat treatment time can be, but is not limited to, 8h, 9h, 10h, 10.5h, 11h, 11.5h or 12h, etc. In an embodiment of the present application, the heat treatment temperature can be 100℃-180℃, and the heat treatment time can be 8h-9h. In another embodiment of the present application, the heat treatment temperature can be 150℃-200℃, and the heat treatment time can be 9h-12h.

[0101] The present application also provides a composite positive electrode material, which comprises a first positive electrode material and a second positive electrode material, the surface of the first positive electrode material has a first group, the surface of the second positive electrode material has a second group, the first group and the second group are independently selected from at least one of -NH2, -C4H4O2, -COOH and -SH, the first group and the second group are connected by a connecting group, and the particle size of the first positive electrode material is larger than the particle size of the second positive electrode material. In the composite positive electrode material provided by the present application, the connecting group can connect the first group and the second group to form a conductive network on the surface of the composite positive electrode material, increase the number of conductive paths of the composite positive electrode material, reduce the polarization effect of the composite positive electrode material, and improve the electrochemical performance of the composite positive electrode material. The different groups on the surfaces of the first positive electrode material and the second positive electrode material with different particle sizes can realize the directional mixing of the composite positive electrode material, improve the compaction density and energy density of the positive electrode sheet, and are beneficial to the wide application of the composite positive electrode material.

[0102] In an embodiment of the present application, the connecting group comprises, but is not limited to, at least one of -C-O-N-H- and -C4H4O2S-. The connecting group is formed by bonding the first group and the second group. For example, -C-O-N-H- bond is formed by dehydrating -NH2 and -COOH, and -C4H4O2S- is formed by bonding -C4H4O2 and -SH.

[0103] Please refer to Fig. 3, which is a schematic diagram of the connection mode inside the composite cathode material provided in an embodiment of the present application. The first group 13 on the surface of the first cathode material 10 is connected to the second group 23 on the surface of the second cathode material 20 through the connecting group 30. In this way, the second cathode material can be arranged around the first cathode material, the directional mixing of the composite cathode material can be realized, the conductive compound containing the conjugated functional groups such as -C-O-N-H- and -C4H4O2S- with electronic conductivity can be formed, thereby forming a conductive network, the number of conductive paths of the composite cathode material is increased, and the compaction density and energy density of the cathode sheet can be improved.

[0104] In the present application, the composite cathode material can include a plurality of first cathode materials and a plurality of second cathode materials, and the plurality of second cathode materials are arranged around the first cathode materials. In an embodiment of the present application, the composite cathode material includes a plurality of composite particles, and each composite particle includes a first cathode material and a plurality of second cathode materials arranged around the first cathode material.

[0105] In an embodiment of the present application, the composite cathode material further includes a directing agent. The connecting group is derived from the directing agent and can be connected to the first group and the second group to form the conductive network. The directing agent that does not form the conductive network with the first group and the second group still exists in the composite cathode material in the form of the directing agent.

[0106] In an embodiment of the present application, the preparation method of the composite cathode material includes mixing the first cathode material, the second cathode material and the directing agent to obtain the composite cathode material. The preparation method provided in the present application is novel and simple in process, and can obtain the composite cathode material with high energy density and good conductive performance. The composite cathode material of any one of the above embodiments can be prepared by the preparation method.

[0107] In an embodiment of the present application, the reaction temperature of the composite cathode material is 80-100℃, and the reaction time is 1-2h. In this way, the composite cathode material with high energy density and excellent conductive performance can be obtained. Specifically, the reaction temperature of the composite cathode material can be but is not limited to 80℃, 85℃, 88℃, 90℃, 92℃, 95℃ or 100℃, etc.; and the reaction time can be but is not limited to 1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2h. In an embodiment of the present application, the reaction temperature of the composite cathode material can be 80-92℃, and the reaction time can be 1-1.6h. In another embodiment of the present application, the reaction temperature of the composite cathode material can be 90-100℃, and the reaction time can be 1.5-2h.

[0108] In an embodiment of the present application, the mass ratio of the first positive electrode material, the second positive electrode material and the guiding agent is (70-90):(10-30):(1-2). Specifically, the mass ratio of the first positive electrode material, the second positive electrode material and the guiding agent can be, but is not limited to, 70:10:1, 72:12:1.2, 78:15:1.3, 80:18:1.4, 82:20:1.6, 86:22:1.7 or 90:30:1, etc. In an embodiment of the present application, the mass ratio of the first positive electrode material, the second positive electrode material and the guiding agent can be (70-83):(10-25):(1-1.7). In another embodiment of the present application, the mass ratio of the first positive electrode material, the second positive electrode material and the guiding agent can be (80-90):(20-30):(1.6-2).

[0109] The present application also provides a positive electrode tab, which comprises a positive electrode active material layer, and the positive electrode active material layer comprises the positive electrode active material of any one of the embodiments described above. Referring to FIG. 4, the cross-sectional schematic diagram of the positive electrode tab provided in an embodiment of the present application, the positive electrode tab 200 comprises a positive electrode current collector 40 and a positive electrode active material layer 50 arranged on the surface of the positive electrode current collector 40. The positive electrode tab provided in the present application has a positive electrode active material with good filling effect and excellent conductivity, thereby improving the compaction density and energy density of the positive electrode tab.

[0110] In an embodiment of the present application, the positive electrode active material layer further comprises a positive electrode conductive agent, which can increase the conductivity of the positive electrode active material and improve the electronic conductivity. Specifically, the positive electrode conductive agent can comprise, but is not limited to, at least one of carbon nanotubes, conductive carbon black, small-particle conductive carbon black, graphite, acetylene black and graphene. In an embodiment of the present application, the positive electrode conductive agent can be graphite. In another embodiment of the present application, the positive electrode conductive agent can be conductive carbon black.

[0111] In an embodiment of the present application, the mass percentage of the conductive agent is 1.5%-1.8%, which can improve the conductivity of the positive electrode tab. Specifically, the mass percentage of the conductive agent can be, but is not limited to, 1.5%, 1.55%, 1.58%, 1.6%, 1.62%, 1.65%, 1.7%, 1.75%, 1.78% or 1.8%, etc. In an embodiment of the present application, the mass percentage of the conductive agent can be 1.5%-1.68%. In another embodiment of the present application, the mass percentage of the conductive agent can be 1.61%-1.8%.

[0112] In an embodiment of the present application, the positive active material layer further comprises a positive electrode binder. The positive electrode binder can improve the binding ability of the components in the positive active material layer and the binding ability between the positive active material layer and the current collector. Specifically, the positive electrode binder can be, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose, and butadiene-styrene latex. In an embodiment of the present application, the positive electrode binder can be polyvinylidene fluoride. In another embodiment of the present application, the positive electrode binder can be sodium carboxymethyl cellulose.

[0113] In an embodiment of the present application, the mass percentage of the positive electrode binder is 2.5%-2.8%, which can improve the binding ability of the positive electrode sheet. Specifically, the mass percentage of the positive electrode binder can be, but is not limited to, 2.5%, 2.55%, 2.58%, 2.6%, 2.62%, 2.65%, 2.7%, 2.75%, 2.78%, or 2.8%, etc. In an embodiment of the present application, the mass percentage of the positive electrode binder can be 2.5%-2.65%. In another embodiment of the present application, the mass percentage of the positive electrode binder can be 2.6%-2.8%.

[0114] In an embodiment of the present application, the compaction density of the positive electrode sheet is 2.6g / cm 3 -2.7g / cm 3 , which can reduce the polarization effect and improve the energy efficiency of the battery. Specifically, the compaction density of the positive electrode sheet can be 2.6g / cm 3 , 2.62g / cm 3 , 2.64g / cm 3 , 2.65g / cm 3 , 2.66g / cm 3 , 2.68g / cm 3 , or 2.7g / cm 3 , etc. In an embodiment of the present application, the compaction density of the positive electrode sheet can be 2.6g / cm 3 -2.67g / cm 3 . In another embodiment of the present application, the compaction density of the positive electrode sheet is 2.62g / cm 3 -2.7g / cm 3 .

[0115] Please refer to FIG. 5, which is a flow chart of the preparation method of the positive electrode sheet provided in an embodiment of the present application, comprising:

[0116] S201: mixing the positive active material, the directing agent, and the solvent in any of the above embodiments to obtain a positive electrode slurry;

[0117] S202: The positive electrode slurry is coated and dried to obtain a positive electrode sheet.

[0118] The present application provides a method for preparing a positive electrode sheet that is simple, easy to operate, and has high production efficiency, and can achieve large-scale production of positive electrode sheets, which is beneficial to the use of positive electrode sheets. The method for preparing a positive electrode sheet provided in the present application can produce a positive electrode sheet according to any of the above embodiments.

[0119] In the present application, the directing agent can promote chemical bonding between the first group and the second group, forming a conductive network on the surface of the positive electrode active material, improving the kinetic performance of the positive electrode sheet, and reducing the polarization effect of the positive electrode sheet. In the positive electrode active material layer, the second positive electrode material surrounds the first positive electrode material, and the first and second groups on the surfaces of the first and second positive electrode materials are connected by the directing agent to form a conductive path. The conductive network formed on the surface of the positive electrode active material improves the kinetic performance of the positive electrode sheet and reduces the polarization effect of the positive electrode sheet; at the same time, directional mixing between the first and second positive electrode materials is achieved, thereby increasing the compaction density of the positive electrode sheet and improving the energy density of the battery.

[0120] In one embodiment of the present application, the directing agent may include, but is not limited to, at least one of an iron-based polymer phthalocyanine compound, polyacetylene, polythiophene, and polymerized aniline. In one embodiment of the present application, the directing agent may be polyacetylene. In another embodiment of the present application, the directing agent may be polythiophene.

[0121] In one embodiment of the present application, the mass percentage of the directing agent in the positive electrode slurry is 1%-2%, which can promote the formation of a conductive network and improve the conductivity of the positive electrode sheet. Specifically, the mass percentage of the directing agent in the positive electrode slurry can be, but is not limited to, 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%. In one embodiment of the present application, the mass percentage of the directing agent in the positive electrode slurry can be 1%-1.7%. In another embodiment of the present application, the mass percentage of the directing agent in the positive electrode slurry can be 1.2%-2%.

[0122] In one embodiment of the present application, the solvent may be N-methylpyrrolidone.

[0123] In one embodiment of the present application, a positive electrode slurry is applied to the surface of a positive electrode current collector and dried to form a positive electrode active material layer, thereby obtaining a positive electrode sheet. Specifically, the positive electrode current collector may include, but is not limited to, at least one of copper, aluminum, nickel, and stainless steel. In one example of the present application, the positive electrode current collector may be aluminum foil.

[0124] In one embodiment of the present application, the coating method may be, but is not limited to, one of spray coating, coating, roller coating, and extrusion coating. In one embodiment of the present application, the coating method may be coating. In another embodiment of the present application, the coating method may be spray coating.

[0125] In an embodiment of the present application, the positive electrode active material, the guiding agent and the solvent are mixed to obtain the positive electrode slurry, and the mixing time of the positive electrode active material, the guiding agent and the solvent is 6h-10h. Specifically, the mixing time of the positive electrode active material, the guiding agent and the solvent can be, but is not limited to, 6h, 7h, 7.5h, 8h, 8.5h, 9h or 10h, etc. In an embodiment of the present application, the mixing time of the positive electrode active material, the guiding agent and the solvent can be 6h-8h. In another embodiment of the present application, the mixing time of the positive electrode active material, the guiding agent and the solvent can be 7.5h-10h.

[0126] In an embodiment of the present application, in the positive electrode slurry, the mass ratio of the first positive electrode material, the second positive electrode material, the guiding agent and the solvent is (70-90):(10-30):(1-2):(60-70), which can improve the energy density of the positive electrode plate and reduce the polarization effect of the positive electrode plate. Specifically, the mass ratio of the first positive electrode material, the second positive electrode material, the guiding agent and the solvent can be, but is not limited to, 70:10:1:60, 75:15:1.2:62, 75:20:1.5:65, 80:18:1.8:68, 85:20:1.9:69 or 90:30:2:70, etc. In an embodiment of the present application, the mass ratio of the first positive electrode material, the second positive electrode material, the guiding agent and the solvent is (70-84):(10-22):(1-1.6):(60-66). In another embodiment of the present application, the mass ratio of the first positive electrode material, the second positive electrode material, the guiding agent and the solvent is (83-90):(20-30):(1.5-2):(65-70).

[0127] In an embodiment of the present application, the positive electrode slurry further comprises a positive electrode conductive agent. The electronic transmission capacity of the positive electrode sheet can be improved, and the conductivity of the positive electrode sheet can be improved. In an embodiment of the present application, in the positive electrode slurry, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode conductive agent, the directing agent and the solvent is (70-90):(10-30):(1.5-1.9):(1-2):(60-70), so that a positive electrode sheet with strong adhesion, good conductivity and high energy density can be obtained. Specifically, in the positive electrode slurry, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode conductive agent, the directing agent and the solvent can be, but is not limited to, 70:30:1.5:1:60, 70:30:1.5:1.2:62, 70:20:30:1.5:1.5:65, 80:20:1.5:1.8:68, 85:15:1.5:1.9:69 or 90:10:1.5:2:70, etc. In an embodiment of the present application, in the positive electrode slurry, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode conductive agent, the directing agent and the solvent can be (70-85):(10-26):(1.5-1.84):(1-1.6):(60-64). In another embodiment of the present application, in the positive electrode slurry, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode conductive agent, the directing agent and the solvent can be (80-90):(20-30):(1.58-1.9):(1.5-2):(63-70).

[0128] In an embodiment of the present application, the positive electrode slurry further comprises a positive electrode binder. The adhesion of the positive electrode active material can be improved, and the structural stability and mechanical properties of the positive electrode sheet can be enhanced. The mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode binder, the directing agent and the solvent is (70-90):(10-30):(2.5-3.0):(1-2):(60-70), so that a positive electrode sheet with strong adhesion and good conductivity can be obtained. Specifically, in the positive electrode slurry, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode binder, the directing agent and the solvent can be, but is not limited to, 70:10:2.5:1:60, 75:15:2.6:1.2:65, 75:20:2.7:1.4:65, 80:18:2.8:1.6:66, 85:20:2.9:1.8:69 or 90:30:2.9:2:70, etc. In an embodiment of the present application, in the positive electrode slurry, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode binder, the directing agent and the solvent can be 90:10:2.9:1:30. In another embodiment of the present application, in the positive electrode slurry, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode conductive agent, the positive electrode binder, the directing agent and the solvent can be 70:30:2.9:1.5:30.

[0129] In an embodiment of the present application, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode conductive agent, the positive electrode binder, the guiding agent and the solvent in the positive electrode slurry is (70-90):(10-30):(1.5-1.9):(2.5-3.0):(1-2):(60-70), so that a positive electrode sheet with strong bonding ability, good conductivity and high energy density can be obtained. Specifically, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode conductive agent, the positive electrode binder, the guiding agent and the solvent in the positive electrode slurry can be, but is not limited to, 70:10:1.5:2.9:1:30, 75:15:1.6:2.9:1.2:30, 75:20:1.7:2.9:1.5:30, 80:18:1.75:2.9:1.7:30, 85:20:1.8:2.9:1.8:30 or 90:30:1.9:2.9:2:30, etc. In an embodiment of the present application, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode conductive agent, the positive electrode binder, the guiding agent and the solvent in the positive electrode slurry can be 90:10:1.5:2.9:1:30. In another embodiment of the present application, the mass ratio of the first positive electrode material, the second positive electrode material, the positive electrode conductive agent, the positive electrode binder, the guiding agent and the solvent in the positive electrode slurry can be 70:30:1.9:2.9:1.6:30.

[0130] The present application also provides a battery comprising the negative electrode sheet and the positive electrode sheet of any one of the embodiments described above. The battery provided by the present application has high energy density, low preparation cost, short cycle, excellent comprehensive electrical performance, and is conducive to improving the product competitiveness of the battery.

[0131] In an embodiment of the present application, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector. Specifically, the negative electrode current collector can include, but is not limited to, at least one of copper, aluminum, nickel and stainless steel. In an embodiment of the present application, the negative electrode current collector can be a copper foil.

[0132] In an embodiment of the present application, the negative electrode active material layer comprises a negative electrode active material, which can include, but is not limited to, at least one of silicon, tin, germanium, lithium and alloys thereof, and carbon materials. The carbon material can include, but is not limited to, at least one of non-graphitized carbon, graphite, pyrolytic carbon, coke and activated carbon. In an embodiment of the present application, the negative electrode active material can be a carbon material. In another embodiment of the present application, the negative electrode active material can be a silicon material.

[0133] In an embodiment of the present application, the negative active material layer further comprises a negative conductive agent. The negative conductive agent can increase the conductivity between the active materials and improve the electronic conductivity. Specifically, the negative conductive agent can include, but is not limited to, at least one of graphite, carbon black, acetylene black and graphene. In an embodiment of the present application, the negative conductive agent can be graphite. In another embodiment of the present application, the negative conductive agent can be carbon black.

[0134] In an embodiment of the present application, the negative active material layer further comprises a negative binder. The negative binder can improve the binding ability of the components in the negative active material layer and improve the binding ability between the negative active material layer and the negative current collector. Specifically, the negative binder can include, but is not limited to, one or more of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose and butadiene-styrene latex. In an embodiment of the present application, the negative binder can be polyvinylidene fluoride.

[0135] In an embodiment of the present application, the battery further comprises a separator disposed between the positive electrode sheet and the negative electrode sheet. Specifically, the separator can include, but is not limited to, a woven film, a non-woven fabric, a microporous film, a composite film, a calendered film or a separator paper. In an embodiment of the present application, the battery further comprises an electrolyte. At least part of the positive electrode sheet and at least part of the negative electrode sheet are soaked in the electrolyte. The electrolyte of the present application is not particularly limited and can include, but is not limited to, substances that can be used as battery electrolytes in the art.

[0136] The present application also provides a power-consuming device comprising the battery of any one of the embodiments described above. The power-consuming device provided by the present application has high energy density, low polarization effect and excellent comprehensive electrochemical performance, and has strong market competitiveness. The power-consuming device includes a mobile phone, a tablet, a watch, a VR glasses, a car and the like. In an embodiment of the present application, the battery can be used in a car, which can reduce the power consumption cost of the car and improve the use rate of the power consumption of the car. In another embodiment of the present application, the battery can also be applied to a mobile phone, which can increase the battery capacity of the mobile phone and improve the service life of the battery.

[0137] The effects of the technical solutions of the present application are further described below through specific examples.

[0138] Example 1

[0139] The first positive electrode material source (lithium source is lithium carbonate, iron source is iron phosphate, phosphorus source is iron phosphate), first carbon source (glucose), first modifier (NH4Cl) and first doping modifier (titanium dioxide) are mixed, stirred for 10 h, and sintered at 780℃ for 10 h to obtain the first positive electrode material.

[0140] The second positive electrode material source (lithium source is lithium carbonate, iron source is iron block, and phosphorus source is ammonium dihydrogen phosphate), the second carbon source (glucose), the second modifier (CH3CH2COOH), and the second doping modifier (titanium dioxide) are mixed, heat treatment temperature is 100 DEG C, heat treatment time is 10h, after filtration and washing, sintering at 750 DEG C for 10h to obtain the second positive electrode material.

[0141] The first positive electrode material (particle size D50 is 1.0 μm), the second positive electrode material (particle size D50 is 0.5 μm), the conductive agent (conductive carbon tube), the binder (polyvinylidene fluoride), the guiding agent, and the solvent (N-methyl pyrrolidone) are mixed, stirred for 1h to obtain a positive electrode slurry, and coated to obtain a positive electrode sheet; wherein the mass ratio of the first positive electrode material and the second positive electrode material is 9:1.

[0142] Example 2

[0143] Different from example 1, the mass ratio of the first positive electrode material and the second positive electrode material is 8:2.

[0144] Example 3

[0145] Different from example 1, the mass ratio of the first positive electrode material and the second positive electrode material is 7:3.

[0146] Example 4

[0147] Different from example 1, the first doping modifier and the second doping modifier are not included in the first positive electrode material and the second positive electrode material.

[0148] Example 5

[0149] Different from example 1, the particle size D50 of the first positive electrode material is 0.8 μm, and the particle size D50 of the second positive electrode material is 0.3 μm.

[0150] Example 6

[0151] Different from example 1, the particle size D50 of the first positive electrode material is 1.5 μm, and the particle size D50 of the second positive electrode material is 0.1 μm.

[0152] Example 7

[0153] Different from example 1, the particle size D50 of the first positive electrode material is 1.5 μm.

[0154] Comparative example 1

[0155] Different from example 1, the particle size D50 of the second positive electrode material is 1 μm.

[0156] Comparative example 2

[0157] The difference from Example 1 is that neither the first nor the second positive electrode material is added with the first modifier and the second modifier.

[0158] Comparative Example 3

[0159] The difference from Example 1 is that the first modifier and the second modifier are the same modifier, and the first group and the second group are the same group.

[0160] Comparative Example 4

[0161] The difference from Example 1 is that the guiding agent is not included in the positive electrode slurry.

[0162] Performance detection

[0163] The positive electrode plates prepared in the above Examples 1-7 and Comparative Examples 1-4 are subjected to compaction density test, and the test conditions are as follows: rolling under the maximum pressure of the rolling machine, measuring the thickness of the positive electrode plate after rolling, and calculating the compaction density by the following formula. Compaction density = positive electrode plate surface density / (positive electrode plate thickness - positive electrode current collector thickness). The results are shown in Table 1.

[0164] The positive electrode plates prepared in the above Examples 1-7 and Comparative Examples 1-4 are assembled with negative electrode plates (graphite) and electrolyte (including 1.0 mol of lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), vinylene carbonate (VC), and fluoroethylene carbonate (FEC)) to prepare batteries by formation, partial capacity. The prepared batteries are subjected to impedance (DCIR) test, and the test conditions are as follows: using Maccro test cabinet for testing, under the condition of 100% SOC of the battery, under the condition of current density 0.5C, charging and discharging for 30s, the standing time between charging and discharging is 30min, the charging and discharging impedance (DCIR) of the test battery is tested, and the results are shown in Table 2.

[0165] The positive electrode plates prepared in the above Examples 1-7 and Comparative Examples 1-4 are assembled with negative electrode plates (graphite) and electrolyte (including 1.0 mol of lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), vinylene carbonate (VC), and fluoroethylene carbonate (FEC), prepared according to the mass percentage of 16:50:30:3:1) to prepare batteries by formation, partial capacity. The batteries prepared are subjected to energy efficiency test, and the test conditions are as follows: using Ruineng test cabinet for testing, under the voltage range of 2.0-3.8V, 0.5CP constant power condition, the batteries are subjected to charging and discharging cycle for 100 times, the ratio of discharge energy and charging energy is calculated, two batteries are tested respectively, and the average value is taken as the energy efficiency of the battery, and the results are shown in Table 2.

[0166] Table 1 Performance test results of positive electrode plate

[0167] Table 2 Performance test results of the batteries

[0168] It can be seen from Examples 1-7 and Comparative Examples 1-4 that the first positive electrode material and the second positive electrode material having the first group and the second group on the surface can enhance the mixing uniformity and the conductivity of the positive electrode active material, and improve the compaction density and the energy efficiency of the positive electrode sheet. It can be seen from Examples 1-3 that the appropriate mass ratio of the first positive electrode material and the second positive electrode material can further improve the compaction density and the energy efficiency of the positive electrode sheet. It can be seen from Examples 5-7 and Comparative Example 1 that the appropriate particle size of the first positive electrode material and the second positive electrode material and the particle size of the first positive electrode material being larger than that of the second positive electrode material can reduce the impedance of the positive electrode sheet and improve the compaction density and the energy efficiency of the positive electrode sheet. It can be seen from Examples 1 and Comparative Examples 2-3 that the first positive electrode material and the second positive electrode material having the first group and the second group on the surface can form a conductive network and enhance the electrochemical performance of the positive electrode sheet, and the appropriate selection of the first group and the second group can further improve the uniform distribution of the positive electrode active material and improve the compaction density and the energy efficiency of the positive electrode sheet. It can be seen from Examples 1 and Comparative Example 4 that the directing agent can connect the first group and the second group and increase the conductive path of the positive electrode active material, and further improve the energy efficiency of the positive electrode sheet. Therefore, the application provides a positive electrode active material with good mixing uniformity between different particle sizes.

[0169] The above is the preferred embodiment of the application, but it cannot be understood as limiting the scope of the application. It should be noted that for ordinary skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, which are also considered to be within the scope of protection of the application.

Claims

1. A positive electrode active material (100), wherein: The positive electrode active material (100) includes a first positive electrode material (10) and a second positive electrode material (20), the surface of the first positive electrode material (10) has a first group (13), the surface of the second positive electrode material (20) has a second group (23), the first group (13) and the second group (23) are independently selected from at least one of -NH2, -C4H4O2, -COOH and -SH, the first group (13) and the second group (23) can be bonded and connected, and the particle size of the first positive electrode material (10) is larger than the particle size of the second positive electrode material (20).

2. The positive electrode active material (100) according to claim 1, wherein The first group (13) and the second group (23) can be connected by hydrogen bonding and / or chemical bonding.

3. The positive electrode active material (100) according to claim 1, wherein The particle size D50 of the first positive electrode material (10) is 0.8 μm-1.5 μm, and the particle size D50 of the second positive electrode material (20) is less than or equal to 0.5 μm.

4. The positive electrode active material (100) according to claim 1, wherein The mass ratio of the first positive electrode material (10) to the second positive electrode material (20) is (9-7):(3-1).

5. The positive electrode active material (100) according to claim 1, wherein In the positive electrode active material (100), the mass percentage of the second positive electrode material (20) is 10%-30%; And / or, in the first cathode material (10), the mass percentage of the first group (13) is 1.1%-1.3%; And / or, in the second positive electrode material (20), the mass percentage of the second group (23) is 1.1%-1.3%.

6. The positive electrode active material (100) according to claim 1, wherein The first positive electrode material (10) comprises a first core (11) and a first carbon coating layer (12) disposed on the surface of the first core (11), wherein the first carbon coating layer (12) has a first group (13); In the first positive electrode material (10), the mass percentage of the first carbon coating layer (12) is 1.1%-1.3%; The second positive electrode material (20) comprises a second core (21) and a second carbon coating layer (22) disposed on the surface of the second core (21), wherein the second carbon coating layer (22) has a second group (23); In the second positive electrode material, the mass percentage of the second carbon coating layer (22) is 1.1%-1.3%.

7. The positive electrode active material (100) according to claim 6, wherein The materials of the first core (11) and the second core (21) are independently selected from at least one of lithium manganese oxide, lithium cobalt oxide, lithium iron phosphate and ternary materials.

8. A method for preparing a positive electrode active material (100), wherein: include: Mixing a first cathode material source and a first modifier to form a first mixture, and performing a first sintering to obtain a first cathode material (10); Mixing a second cathode material source and a second modifier to form a second mixture, and performing a second sintering to obtain a second cathode material (20); The first positive electrode material (10) and the second positive electrode material (20) are mixed to obtain a positive electrode active material (100); the positive electrode active material (100) includes the first positive electrode material (10) and the second positive electrode material (20), the surface of the first positive electrode material (10) has a first group (13), the surface of the second positive electrode material (20) has a second group (23), the first group (13) and the second group (23) are independently selected from at least one of -NH2, -C4H4O2, -COOH and -SH, the first group (13) and the second group (23) can be bonded and connected, and the particle size of the first positive electrode material (10) is larger than the particle size of the second positive electrode material (20).

9. The preparation method according to claim 8, wherein The first modifier and the second modifier are independently selected from CH3CH2COOH, CH3CH2CH2COOH, NH4Cl, (NH4)2SO4, NH4NO3, Na2SO4, H2SO4, CH3C4H4O 2、 At least one of C4H4O2, NH3·H2O and CH3COOH.

10. The preparation method according to claim 8, wherein The first mixture further includes a first carbon source, and the second mixture further includes a second carbon source, wherein the first carbon source and the second carbon source are independently selected from at least one of glucose, sucrose, citric acid, polyethylene glycol, carbon nanotubes and graphene.

11. The preparation method according to claim 10, wherein The mass ratio of the first cathode material source, the first modifier and the first carbon source is (2.52-2.58):(0.0038-0.0047):(6.5-6.7); The mass ratio of the second positive electrode material source, the second modifier and the second carbon source is (2.52-2.58):(0.0012-0.0025):(5.1-5.5).

12. The preparation method according to claim 8, wherein The temperature of the first sintering is 750° C.-800° C., and the time of the first sintering is 15 h-20 h; The temperature of the second sintering is 700° C.-800° C., and the time of the second sintering is 3 hours-7 hours.

13. A composite cathode material, wherein: The composite active material includes a first positive electrode material (10) and a second positive electrode material (20), the surface of the first positive electrode material (10) has a first group (13), the surface of the second positive electrode material (20) has a second group (23), the first group (13) and the second group (23) are independently selected from at least one of -NH2, -C4H4O2, -COOH and -SH, the first group (13) and the second group (23) are connected by a connecting group (30), and the particle size of the first positive electrode material (10) is larger than the particle size of the second positive electrode material (20).

14. The composite cathode material according to claim 13, wherein The first group (13), the linking group (30) and the second group (23) are connected by hydrogen bonds and / or chemical bonds.

15. A positive electrode plate (200), wherein: The positive electrode plate (200) includes a positive electrode active material layer (50), and the positive electrode active material layer (50) includes the positive electrode active material (100) described in any one of claims 1 to 7, or the positive electrode active material (100) prepared by the preparation method described in any one of claims 8 to 12, or the composite positive electrode material described in claim 13 or 14.

16. The positive electrode sheet (200) according to claim 15, wherein: The compaction density of the positive electrode plate (200) is 2.6 g / cm 3 -2.7g / cm 3 .

17. A method for preparing a positive electrode sheet (200), wherein: include: Mixing the positive electrode active material (100) according to any one of claims 1 to 7 or the positive electrode active material (100) prepared by the preparation method according to any one of claims 8 to 12, a directing agent, and a solvent to obtain a positive electrode slurry; The positive electrode slurry is coated and dried to obtain a positive electrode sheet.

18. The preparation method according to claim 17, wherein In the positive electrode slurry, the mass percentage of the directing agent is 1%-2%; The directing agent includes at least one of an iron-based polymer phthalocyanine compound, polyacetylene, polythiophene and polymeric aniline.

19. A battery, wherein: The battery comprises a negative electrode sheet and a positive electrode sheet (200) according to claim 15 or 16 or a positive electrode sheet (200) prepared by the preparation method according to claim 17 or 18.

20. An electrical device, wherein: The electric device comprises the battery according to claim 19.

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