Positive electrode active material, preparation method thereof, positive electrode sheet, battery and electrical equipment

Abstract

The present invention discloses a positive electrode active material, a preparation method thereof, a positive electrode sheet, a battery and an electrical device. The positive electrode active material is a secondary particle, and the equivalent number of sheet layers R of the (003) crystal plane of the positive electrode active material (003) and the equivalent number of sheet layers R of the (104) crystal plane (104) satisfy: R (104) / R (003) is 1.4 - 1.8, where A (003) is the average thickness in the direction perpendicular to the (003) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm, and B (003) is the crystal plane spacing of the (003) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm, A (104) is the average thickness in the direction perpendicular to the (104) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm, and B (104) is the crystal plane spacing of the (104) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm. Thus, using this positive electrode active material can enable the battery containing it to have excellent cycle performance.

Description

Technical Field

[0001] The present invention belongs to the field of batteries, and particularly relates to a positive electrode active material, a preparation method thereof, a positive electrode sheet, a battery and an electrical device. Background Art

[0002] Lithium-ion batteries are widely used in various consumer electronic products and electric vehicles due to their outstanding characteristics such as light weight, pollution-free, and no memory effect. During the charge-discharge cycle process, as lithium ions in the positive electrode active material are deintercalated and intercalated, the positive electrode active material undergoes contraction and expansion, resulting in the easy generation of cracks in the positive electrode active material, reducing the structural stability of the material, and thus leading to lower battery cycle performance. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, an object of the present invention is to provide a positive electrode active material, a preparation method thereof, a positive electrode sheet, a battery and an electrical device. Using this positive electrode active material, the battery containing it can have excellent cycle performance.

[0004] In one aspect of the present invention, a positive electrode active material is provided. According to an embodiment of the present invention, the positive electrode active material is a secondary particle, and the equivalent number of sheet layers R of the (003) crystal plane of the positive electrode active material (003) and the equivalent number of sheet layers R of the (104) crystal plane (104) satisfy: R (104) / R (003) is 1.4 - 1.8, where A (003) is the average thickness perpendicular to the (003) crystal plane direction in the microcrystal of the positive electrode active material, with the unit of nm, B (003) is the crystal plane spacing of the (003) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm, A (104) is the average thickness perpendicular to the (104) crystal plane direction in the microcrystal of the positive electrode active material, with the unit of nm, B (104) is the crystal plane spacing of the (104) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm.

[0005] For the positive electrode active material according to the embodiment of the present invention, the equivalent number of sheet layers R of its (003) crystal plane (003) and the equivalent number of sheet layers R of the (104) crystal plane (104) satisfy: R (104) / R (003)is 1.4 - 1.8, which can cause the primary particles in the positive electrode active material to be arranged in a divergent manner, and have regular grain boundaries and a small grain surface density. During charge and discharge, the primary particles contract and expand in the c-axis direction and align with the grain boundary lines, which can not only effectively release the expansion stress generated during charge and discharge, but also prevent microcracks from occurring between interfaces, significantly improving the stability of the positive electrode active material. Therefore, using the positive electrode active material of the present invention can make the battery containing it have excellent cycle performance.

[0006] In addition, the positive electrode active material according to the above embodiments of the present invention may further have the following additional technical features:

[0007] In some embodiments of the present invention, R (104) / R (003) is 1.55 - 1.75. Thus, the cycle performance of the battery can be further improved.

[0008] In some embodiments of the present invention, the equivalent number of crystal plane sheets R of the positive electrode active material (003) (003) is 80 - 130, preferably 90 - 120.

[0009] In some embodiments of the present invention, the equivalent number of crystal plane sheets R of the positive electrode active material (104) (104) is 140 - 210, preferably 150 - 200.

[0010] In some embodiments of the present invention, where K is the Scherrer constant 0.89, λ is the wavelength of the test X-ray, β1 is the full width at half maximum of the diffraction peak of the (003) crystal plane in the microcrystals of the positive electrode active material, and θ1 is the Bragg diffraction angle of the (003) crystal plane in the microcrystals of the positive electrode active material.

[0011] In some embodiments of the present invention,

[0012] In some embodiments of the present invention, the average thickness A in the direction perpendicular to the (003) crystal plane in the microcrystals of the positive electrode active material (003) is 35nm - 55nm, preferably 40nm - 55nm.

[0013] In some embodiments of the present invention, the crystal plane spacing B of the (003) crystal plane of the positive electrode active material (003) is 0.4730nm - 0.4760nm, preferably 0.4735nm - 0.4750nm.

[0014] In some embodiments of the present invention, Where K is the Scherrer constant 0.89, λ is the wavelength of the X-ray used for testing, β2 is the full width at half maximum of the diffraction peak of the (104) crystal plane in the microcrystals of the positive electrode active material, and θ2 is the Bragg diffraction angle of the (104) crystal plane in the microcrystals of the positive electrode active material.

[0015] In some embodiments of the present invention,

[0016] In some embodiments of the present invention, the average thickness A of the microcrystals of the positive electrode active material in the direction perpendicular to the (104) crystal plane (104) is 25 nm - 55 nm, preferably 30 nm - 50 nm.

[0017] In some embodiments of the present invention, the interplanar spacing B of the (104) crystal plane of the positive electrode active material (104) is 0.2030 nm - 0.2040 nm, preferably 0.2035 nm - 0.2040 nm.

[0018] In some embodiments of the present invention, the aspect ratio of the primary particles of the positive electrode active material is 2 - 5:1, preferably 2 - 4:1. Thereby, the cycle performance of the battery can be further improved.

[0019] In some embodiments of the present invention, the sectional porosity of the positive electrode active material is 2% - 10%, preferably 3% - 8%. Thereby, the cycle performance of the battery can be further improved.

[0020] In some embodiments of the present invention, the BET specific surface area of the positive electrode active material is 0.4 m 2 / g - 0.9 m 2 / g, preferably 0.5 m 2 / g - 0.8 m 2 / g. Thereby, the cycle performance of the battery can be further improved.

[0021] In some embodiments of the present invention, the positive electrode active material includes a matrix, and the matrix includes Li 1+ a Ni x Co y Mn z M m O2, -0.05 ≤ a ≤ 0.3, 0.8 ≤ x ≤ 1, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.2, 0.002 ≤ m ≤ 0.01, and M includes at least one of Sn, W, V, Mo, P, and B. Thereby, the cycle performance of the battery can be further improved.

[0022] In some embodiments of the present invention, M further includes at least one of Sb, Nb, Mg, La, Ti, Al, Sr, Ba, Y, Zr, Ca, Fe, S, Zn, and Ta.

[0023] In some embodiments of the present invention, the positive electrode active material further includes a coating layer formed on at least a part of the surface of the substrate. The coating layer contains element J, and element J includes at least one of Al, Zr, Ti, F, B, Cl, Br, I, S, W, Co, Sn, and Mo. Thereby, the cycle performance of the battery can be further improved.

[0024] In a second aspect of the present invention, the present invention provides a method for preparing the above positive electrode active material, including:

[0025] Providing a positive electrode active material precursor;

[0026] Performing a first mixed sintering on the positive electrode active material precursor, a lithium source, and a dopant containing element M to obtain a first sintered material of the positive electrode active material.

[0027] Thereby, the above positive electrode active material can be prepared by using this method, so that the battery containing the same has excellent cycle performance.

[0028] In some embodiments of the present invention, the positive electrode active material precursor is prepared by the following method: The positive electrode active material precursor is prepared by the following method: mixing a nickel salt, a cobalt salt, a manganese salt, a precipitating agent, and a complexing agent to perform a coprecipitation reaction to obtain a positive electrode active material precursor, wherein the temperature of the coprecipitation reaction is 50°C - 80°C, preferably 55°C - 75°C; the ammonia content during the coprecipitation reaction is 2 g / L - 8 g / L, preferably 3 g / L - 7 g / L.

[0029] In some embodiments of the present invention, the positive electrode active material precursor satisfies at least one of the following conditions:

[0030] The Dv50 of the positive electrode active material precursor is 9 μm - 20 μm;

[0031] The equivalent number of laminar slices R of the (101) crystal plane of the positive electrode active material precursor (101) and the equivalent number of laminar slices R of the (001) crystal plane of the positive electrode active material precursor (001) satisfy: R (101) / R (001) is 2.0 - 3.0;

[0032] The peak intensity ratio I of the positive electrode active material precursor (101) / I (001) is 0.7 - 1.4, preferably 0.8 - 1.2.

[0033] Thereby, the cycle performance of the battery can be further improved.

[0034] In some embodiments of the present invention, the temperature of the first mixed sintering is 650°C - 900°C, and the time is 4h - 15h.

[0035] In some embodiments of the present invention, the method further includes second mixed sintering of the first sintered material of the positive electrode active material and a coating agent containing element J, so as to form a coating layer containing element J on at least part of the surface of the first sintered material of the positive electrode active material. Thereby, the cycle performance of the battery can be further improved.

[0036] In some embodiments of the present invention, the temperature of the second mixed sintering is 200°C - 700°C, and the time is 3h - 10h.

[0037] In the third aspect of the present invention, a positive electrode plate is proposed, which includes the positive electrode active material described in the first aspect of the present invention or the positive electrode active material obtained by the method described in the second aspect of the present invention. Thereby, the battery containing it has excellent cycle performance.

[0038] In the fourth aspect of the present invention, a battery is proposed, which includes the positive electrode plate described in the third aspect of the present invention. Thereby, the battery has excellent cycle performance.

[0039] In the fifth aspect of the present invention, an electrical device is proposed, which includes the battery described in the fourth aspect of the present invention.

[0040] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Detailed Description of Specific Embodiments

[0041] The embodiments of the present invention will be described in detail below, which are intended to explain the present invention and should not be construed as a limitation to the present invention.

[0042] In the ranges disclosed herein, the endpoints and any values are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0043] In one aspect of the present invention, a positive electrode active material is proposed. According to the embodiments of the present invention, the positive electrode active material is a secondary particle, and the equivalent number of crystal plane sheets R of the positive electrode active material (003) (003)The number of equivalent sheet layers R of the (104) crystal plane (104) Satisfies: R (104) / R (003) Is 1.4 - 1.8, Where A (003) Is the average thickness perpendicular to the (003) crystal plane direction in the microcrystals of the positive electrode active material, with the unit of nm, and B (003) Is the (003) crystal plane spacing in the microcrystals of the positive electrode active material, with the unit of nm, and A (104) Is the average thickness perpendicular to the (104) crystal plane direction in the microcrystals of the positive electrode active material, with the unit of nm, and B (104) Is the (104) crystal plane spacing in the microcrystals of the positive electrode active material, with the unit of nm.

[0044] The inventors found that the number of equivalent sheet layers of the crystal plane of the positive electrode active material with a layered structure represents the framework size of the R-3m structure. For the positive electrode active material with a layered structure, the statistical stacking number in a certain direction can reflect the average number of lattice sites in that direction. For the positive electrode active material with a layered structure, the number of equivalent sheet layers in each direction can truly reflect the number of active lithium sites that a single microcrystal can accommodate, which will affect the capacity, lithium ion transmission channels, and overall structural stability. During the charge and discharge process, the positive electrode active material with a layered structure usually undergoes obvious shrinkage and expansion in the c-axis and a-axis directions in layers, and the shrinkage and expansion of the overall microcrystal size is the sum of the structural change degrees within each layer. Therefore, the number of crystal layers is crucial for the structural changes and expansion stress within the microcrystal due to the layered lattice, and has a decisive impact on the structural stability of the material. The material R (104) / R (003) Can represent the ratio of the number of sheet layers in the a-axis direction to the number of sheet layers in the c-axis direction. The c-axis is arranged parallel to the direction from the center to the surface of the secondary particle, and the a-axis extends in the direction from the center to the surface of the secondary particle. Further, the inventors found that the number of equivalent sheet layers R of the (003) crystal plane of the positive electrode active material (003) And the number of equivalent sheet layers R of the (104) crystal plane (104) Satisfies: R (104) / R (003) Is 1.4 - 1.8, which can cause the primary particles in the positive electrode active material to be arranged in a divergent shape, and have regular grain boundaries and less crystal plane density. During the charge and discharge process, the primary particles shrink and expand in the c-axis direction and align with the grain boundary lines, which can not only effectively release the expansion stress generated during the charge and discharge process, but also prevent the generation of microcracks between the interfaces, significantly improving the stability of the positive electrode active material. Thus, using the positive electrode active material of the present invention can make the battery containing it have excellent cycle performance.

[0045] According to the embodiments of the present invention, the number of equivalent sheet layers R of the (003) crystal plane of the above positive electrode active material (003)The number of equivalent sheet layers R of the (104) crystal plane (104) Satisfy R (104) / R (003) Is 1.4 - 1.8, for example, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, etc. According to specific embodiments of the present invention, R (104) / R (003) Is 1.55 - 1.75. Thus, the stability of the positive electrode active material can be further improved, thereby improving the cycle performance of the battery.

[0046] According to an embodiment of the present invention, the number of equivalent sheet layers R of the (003) crystal plane of the positive electrode active material (003) Is 80 - 130, for example, 80, 90, 100, 110, 120, 130, etc. Further, the number of equivalent sheet layers R of the (003) crystal plane of the positive electrode active material (003) Is 90 - 120; the number of equivalent sheet layers R of the (104) crystal plane of the positive electrode active material (104) Is 140 - 210, for example, 140, 150, 160, 170, 180, 190, 200, 210, etc. Further, the number of equivalent sheet layers R of the (104) crystal plane of the positive electrode active material (104) Is 150 - 200.

[0047] The inventors found that when the number of equivalent sheet layers of the (003) crystal plane of the positive electrode active material is within the above range, on the one hand, it ensures that there are enough lithium sites in the overall layered framework to provide an accommodation space for active lithium and obtain the maximum reversible specific capacity; on the other hand, it has a stabilizing effect on the expansion and contraction of the c-axis during charge and discharge, can alleviate the structural distortion and collapse of the material, and endow the material with excellent cycle stability. The number of equivalent sheet layers of the (104) crystal plane of the positive electrode active material can indirectly reflect the stacking number in the a-axis direction, represents the size of the flat layer, determines the number of lithium-ion sites that can be accommodated in each flat layer, and the length of the solid-phase migration path when lithium ions are inserted and extracted within the layer. When the number of equivalent sheet layers of the (104) crystal plane of the positive electrode active material is within the above range, it can endow the material with the maximum reversible capacity and high-rate performance. Thus, the present invention controls the R (003) and R (104) within the above range, which can further improve the energy density, cycle performance, rate performance and safety performance of the battery.

[0048] Specifically, by performing calculations using the Scherrer formula and the Bragg formula on the XRD test results of the positive electrode active material, the average microcrystalline thickness A hkl of the material along a certain crystal plane and the crystal plane spacing B hkl of the material along a certain crystal plane can be obtained respectively. Taking R hkl = A hkl / Bhkl Calculating the number of equivalent plane layers of microcrystals in a material along a specific crystal plane, for example

[0049] As an example, the above where K is the Scherrer constant 0.89, λ is the wavelength of the X-ray used for testing, β1 is the full width at half maximum of the diffraction peak of the (003) crystal plane in the microcrystals of the positive electrode active material, and θ1 is the Bragg diffraction angle of the (003) crystal plane in the microcrystals of the positive electrode active material; The above where K is the Scherrer constant 0.89, λ is the wavelength of the X-ray used for testing, β2 is the full width at half maximum of the diffraction peak of the (104) crystal plane in the microcrystals of the positive electrode active material, and θ2 is the Bragg diffraction angle of the (104) crystal plane in the microcrystals of the positive electrode active material; Specifically, 2θ1 of the XRD diffraction characteristic peak corresponding to the (003) crystal plane is between 18.5° and 19.5°, and 2θ2 of the (104) crystal plane is between 44.0° and 44.5°.

[0050] According to an embodiment of the present invention, the average thickness A of the microcrystals of the positive electrode active material in the direction perpendicular to the (003) crystal plane (003) is 35 nm - 55 nm, such as 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, etc. Further, the average thickness A of the microcrystals of the positive electrode active material in the direction perpendicular to the (003) crystal plane (003) is 40 nm - 55 nm. Thus, when the average thickness A of the microcrystals of the positive electrode active material in the direction perpendicular to the (003) crystal plane (003) satisfies the above range, the material has a suitable microcrystal size in the c-axis direction, which can not only ensure the normal reversible capacity release but also have a certain stabilizing effect during the expansion and contraction in the c-axis, endowing the material with the best comprehensive performance in terms of capacity and cycle life.

[0051] According to an embodiment of the present invention, the interplanar spacing B of the (003) crystal plane of the positive electrode active material (003) is 0.4730 nm - 0.4760 nm, such as 0.4730 nm, 0.4735 nm, 0.4740 nm, 0.4745 nm, 0.4750 nm, 0.4755 nm, 0.4760 nm, etc. Further, the interplanar spacing B of the (003) crystal plane of the positive electrode active material (003) is 0.4735 nm - 0.4750 nm. Thus, when the interplanar spacing B of the (003) crystal plane of the positive electrode active material (003) satisfies the above range, on the one hand, it is beneficial to the rapid insertion and extraction of lithium ions, improving the rate performance of the material; on the other hand, it can provide a certain space for the contraction and expansion of the unit cell in the c-axis direction, reducing the lattice distortion and microcrystal microstress, and improving the stability of the material.

[0052] According to an embodiment of the present invention, the average thickness A of the microcrystals of the positive electrode active material in the direction perpendicular to the (104) crystal plane (104) is 25 nm - 55 nm, such as 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, etc. Further, the average thickness A of the microcrystals of the positive electrode active material in the direction perpendicular to the (104) crystal plane (104) is 30 nm - 50 nm. Thus, when the average thickness A of the microcrystals of the positive electrode active material in the direction perpendicular to the (104) crystal plane (104) meets the above range, the material has a suitable microcrystal size in the a-axis direction, a suitable active structure and lithium-ion migration channels, ensuring that the material has high capacity and good rate performance.

[0053] According to an embodiment of the present invention, the (104) crystal plane spacing B of the positive electrode active material (104) is 0.2030 nm - 0.2040 nm, such as 0.2030 nm, 0.2032 nm, 0.2035 nm, 0.2037 nm, 0.2039 nm, 0.2040 nm, etc. Further, the (104) crystal plane spacing B of the positive electrode active material (104) is 0.2035 nm - 0.2040 nm. Thus, when the (104) crystal plane spacing B of the positive electrode active material (104) meets the above range, it is beneficial for the rapid insertion and extraction of lithium ions, and can also relieve the cell contraction in the a-axis direction, improving the rate performance and cycle stability of the material.

[0054] According to an embodiment of the present invention, the aspect ratio of the primary particles of the positive electrode active material is 2 - 5:1, such as 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc. Further, the aspect ratio of the primary particles of the positive electrode active material is 2 - 4:1.

[0055] According to an embodiment of the present invention, the sectional porosity of the positive electrode active material is 2% - 10%, such as 2%, 5%, 7%, 9%, 10%, etc. Further, the sectional porosity of the positive electrode active material is 3% - 8%.

[0056] According to an embodiment of the present invention, the BET specific surface area of the positive electrode active material is 0.4 m 2 / g - 0.9 m 2 / g, such as 0.4 m 2 / g, 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, etc. Further, the BET specific surface area of the positive electrode active material is 0.5 m 2 / g - 0.8 m 2 / g.

[0057] Under the aspect ratio of the primary particles as described above, the primary particles exhibit a more slender morphology, the a-axis is highly consistent with the direction radiating from the center of the secondary particles, more voids are formed between the primary particles, and the material has a larger specific surface area. The above-mentioned secondary particle morphology and structure not only alleviate particle swelling and minimize crack generation, but also prevent side reactions of the electrolyte inside the secondary particles, thereby improving the stability of the positive electrode active material.

[0058] In this application, the method for testing the aspect ratio of the primary particles of the positive electrode active material includes: obtaining a surface electron microscope image under SEM, using software to identify the major and minor axes of the primary particles in the secondary particle sphere, and obtaining the average aspect ratio of the particles.

[0059] In this application, the method for testing the sectional porosity of the positive electrode active material includes: after performing a sectional treatment on the positive electrode active material, obtaining a sectional electron microscope image under SEM. Using software to identify the contrast of the image, obtaining the pore area and the total area, where the ratio of the pore area to the total area is the sectional porosity.

[0060] In this application, the BET specific surface area of the positive electrode active material can be measured using instruments and methods well-known in the art. For example, it can be obtained by referring to the following method: using the Micromeritics Gemini VII 2390 multi-station automatic specific surface area and pore size analyzer in the United States, taking about 7 g of the sample and placing it in a 9 cc long tube with a bulb, degassing at 200 °C for 2 h, and then placing it in the main unit for testing to obtain the BET specific surface area data of the positive electrode active material.

[0061] According to an embodiment of the present invention, the positive electrode active material includes a matrix, Li 1+a Ni x Co y Mn z M m O2, -0.05 ≤ a ≤ 0.3, 0.8 ≤ x ≤ 1, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.2, 0.002 ≤ m ≤ 0.01, M includes at least one of Sn, W, V, Mo, P, and B. Thus, by doping the above M element in the positive electrode active material, the equivalent number of crystal plane layers of the positive electrode active material can be regulated, thereby improving the cycling performance of the battery.

[0062] According to some embodiments of the present invention, the Li 1+a Ni x Co y Mnz M m In M O₂, a satisfies -0.05 ≤ a ≤ 0.3. For example, a can be -0.05, -0.02, 0, 0.02, 0.05, 0.1, 0.2, 0.3, etc. Thus, the inclusion of such an amount of lithium ions in the matrix can increase the specific capacity of the cathode active material, thereby enabling the battery to have a higher energy density.

[0063] According to some embodiments of the present invention, the Li 1+a Ni x Co y Mn z M m In M O₂, x, y, z, and m satisfy 0.8 ≤ x ≤ 1, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.2, 0.002 ≤ m ≤ 0.01. For example, x can be 0.8, 0.85, 0.9, 0.95, 1, etc.; y can be 0, 0.1, 0.15, 0.2, etc.; z can be 0, 0.1, 0.15, 0.2, etc.; m can be 0.002, 0.005, 0.007, 0.01, etc.

[0064] According to some embodiments of the present invention, the Li 1+a Ni x Co y Mn z M m In M O₂, M may further include at least one of Sb, Nb, Mg, La, Ti, Al, Sr, Ba, Y, Zr, Ca, Fe, S, Zn, and Ta. Thus, the stability of the cathode active material can be further improved, and the cycle performance of the battery can be enhanced.

[0065] According to an embodiment of the present invention, the cathode active material further includes a coating layer formed on at least a part of the surface of the matrix. The coating layer contains element J, and element J includes at least one of Al, Zr, Ti, F, B, Cl, Br, I, S, W, Co, Sn, and Mo. Thus, by forming a coating layer containing element J on the outer surface of the matrix, it can reduce the side reaction between the core of the cathode active material and the electrolyte, thereby improving the cycle stability of the cathode active material.

[0066] It should be noted that the form of the existence of element J in the above coating layer may include oxides and / or lithium oxides, which can be selected by those skilled in the art according to actual needs and will not be elaborated here.

[0067] In the second aspect of the present invention, the present invention provides a method for preparing the above-mentioned cathode active material. According to an embodiment of the present invention, the method includes:

[0068] S100: Providing a cathode active material precursor

[0069] According to an embodiment of the present invention, the precursor of the positive electrode active material can be a commercially available product or prepared by the following steps:

[0070] Specifically, a nickel salt solution, a cobalt salt solution, and a manganese salt solution are mixed according to a molar ratio of nickel element, cobalt element, and manganese element of x:y:z, and then a precipitant (such as sodium hydroxide solution) and a complexing agent (such as ammonia water) are added, and co-precipitation reaction is carried out to obtain the precursor of the positive electrode active material, wherein the temperature of the co-precipitation reaction is 50°C - 80°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc. Further, the temperature of the co-precipitation reaction is 55°C - 75°C; the ammonia content in the co-precipitation reaction is 2 g / L - 8 g / L, such as 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L. Further, the ammonia content is 3 g / L - 7 g / L.

[0071] It should be noted that the "ammonia content in the co-precipitation reaction" can be understood as the content of ammonia water in the reaction system when ammonia water is used as the complexing agent for the co-precipitation reaction.

[0072] Thus, by controlling the above co-precipitation temperature and ammonia content, a precursor with a specific number of equivalent lamellae on the crystal plane can be synthesized.

[0073] According to an embodiment of the present invention, the Dv50 of the precursor of the positive electrode active material is 9 μm - 20 μm, such as 9 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc.

[0074] In the present invention, Dv50 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%, and is measured using a laser particle size analyzer (such as MalverR Master Size 3000) with reference to the standard GB / T19077 - 2016.

[0075] According to an embodiment of the present invention, the number of equivalent lamellae R on the (101) crystal plane of the precursor of the positive electrode active material (101) and the number of equivalent lamellae R on the (001) crystal plane of the precursor of the positive electrode active material (001) satisfy: R (101) / R (001) is 2.0 - 3.0, such as 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, etc. Thus, when the number of equivalent lamellae R on the (101) crystal plane of the precursor of the positive electrode active material (101) and the number of equivalent lamellae R on the (001) crystal plane of the precursor of the positive electrode active material (001)Meeting the above range, the precursor is easy to obtain a higher crystallinity and exhibits a more regular radial arrangement, and is easily lithiated and reorganized during the subsequent pyrometallurgical sintering process to form a suitable number of crystal layers and a regularly arranged cathode active material in terms of structure.

[0076] It should be noted that the equivalent number of crystal layers R of the crystal plane of the cathode active material precursor (101) (101) and the equivalent number of crystal layers R of the crystal plane of the cathode active material precursor (001) (001) The test of R for the above-mentioned cathode active material (003) and R (104) is similar to the test, for example where A (101) is the average thickness perpendicular to the (101) crystal plane direction in the microcrystal of the cathode active material precursor, with the unit of nm, and B (101) is the crystal plane spacing of the (101) crystal plane in the microcrystal of the cathode active material precursor, with the unit of nm; A (001) is the average thickness perpendicular to the (001) crystal plane direction in the microcrystal of the cathode active material precursor, with the unit of nm, and B (001) is the crystal plane spacing of the (001) crystal plane in the microcrystal of the cathode active material precursor, with the unit of nm.

[0077] As an example, the above where K is the Scherrer constant 0.89, λ is the wavelength of the test X-ray, β3 is the full width at half maximum of the diffraction peak of the (101) crystal plane in the microcrystal of the cathode active material precursor, and θ3 is the Bragg diffraction angle of the (101) crystal plane in the microcrystal of the cathode active material precursor; The above <9000350>where K is the Scherrer constant 0.89, λ is the wavelength of the test X-ray, β4 is the full width at half maximum of the diffraction peak of the (001) crystal plane in the microcrystal of the cathode active material, and θ4 is the Bragg diffraction angle of the (104) crystal plane in the microcrystal of the cathode active material,

[0078] According to the embodiment of the present invention, the peak intensity ratio I of the cathode active material precursor (101) / I (001) is 0.7 - 1.4, such as 0.7, 0.8, 1, 1.2, 1.4, etc. Further, the peak intensity ratio I of the cathode active material precursor (101) / I (001) is 0.8 - 1.2. Thus, the peak intensity ratio of the cathode active material precursor meets the above range, enabling the precursor itself to have a high crystallinity, thereby improving the stability of the cathode active material.

[0079] In this application, the peak intensity I of the cathode active material precursor (101)Refers to the peak intensity of the characteristic peak of the (101) crystal plane in its XRD pattern, I (001) Refers to the peak intensity of the characteristic peak of the (001) crystal plane in its XRD pattern.

[0080] S200: First, mix and sinter the precursor of the cathode active material with a lithium source and a dopant containing element M

[0081] According to an embodiment of the present invention, the precursor of the cathode active material obtained in the above steps is mixed and sintered with a lithium source and a dopant containing element M in an oxygen-containing atmosphere. Among them, the temperature of the first mixing and sintering is 650°C - 900°C, for example, the sintering temperature is 650°C, 680°C, 700°C, 720°C, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C, 900°C, and the time is 4h - 15h, for example, 4h, 6h, 8h, 10h, 12h, 15h, etc. Then, it is naturally cooled to make the sintered compound drop to room temperature. After crushing, sieving, and iron removal, the first-burned cathode active material is obtained. Thus, by selecting a specific doping element M, it can regulate the growth of the microcrystals of the cathode active material during the lithiation stage, and combined with the above sintering conditions, it can achieve the control of the equivalent number of crystal plane sheets and the crystal plane spacing of the cathode active material.

[0082] As an example, the above nickel salt, cobalt salt, and manganese salt can be the corresponding chlorides, carbonates, and sulfates of each element, and the lithium source and the dopant containing element M can be at least one of the corresponding chlorides, carbonates, sulfates, and oxides.

[0083] Thus, by using this method, the above cathode active material can be prepared, thereby improving the cycle performance of the battery.

[0084] According to an embodiment of the present invention, the method for preparing the cathode active material further includes:

[0085] S300: The first-burned cathode active material obtained in step S200 is mixed and sintered with a coating agent containing element J in an oxygen-containing atmosphere. The temperature of the second mixing and sintering is 200°C - 700°C, for example, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, etc., and the time is 3h - 10h, for example, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc., so as to form a coating layer containing element J on at least part of the surface of the first-burned cathode active material. Then, it is naturally cooled, crushed, sieved, and iron removed to obtain the cathode active material. Thus, by forming a coating layer containing element J on the outer surface of the cathode active material, it can reduce the side reaction between the core of the cathode active material and the electrolyte, thereby improving the cycle stability of the cathode active material.

[0086] It should be noted that the features and advantages described above for the positive electrode active material also apply to the method for preparing the positive electrode active material, and will not be elaborated here.

[0087] In the third aspect of the present invention, the present invention provides a positive electrode plate. According to an embodiment of the present invention, the positive electrode plate includes the positive electrode active material described in the first aspect of the present invention or the positive electrode active material obtained by the method described in the second aspect of the present invention.

[0088] According to an embodiment of the present invention, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer includes the above positive electrode active material. The positive electrode current collector may be a metal foil or a composite current collector (a composite current collector can be formed by disposing a metal material on a polymer substrate). For example, the positive electrode current collector may be an aluminum foil.

[0089] According to some embodiments of the present invention, the positive electrode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVBF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorinated acrylate resin.

[0090] According to some embodiments of the present invention, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0091] According to some embodiments of the present invention, the positive electrode plate can be prepared in the following manner: dispersing the above components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0092] It should be noted that the features and advantages described above for the positive electrode active material and its preparation method also apply to the positive electrode plate, and will not be elaborated here.

[0093] In the fourth aspect of the present invention, the present invention provides a battery. According to an embodiment of the present invention, the battery includes the above positive electrode plate.

[0094] As an example, the battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. The separator is located between the positive electrode plate and the negative electrode plate. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0095] According to an embodiment of the present invention, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, wherein the negative electrode current collector can be a metal foil or a composite current collector (a composite current collector can be formed by disposing a metal material on a polymer substrate). For example, the positive electrode current collector can be a copper foil.

[0096] According to some embodiments of the present invention, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc.

[0097] According to some embodiments of the present invention, the negative electrode active material layer may optionally further include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0098] According to some embodiments of the present invention, the negative electrode active material layer may optionally further include other additives, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Ra)), etc.

[0099] According to some embodiments of the present invention, the negative electrode plate can be prepared in the following manner: the components for preparing the negative electrode plate described above, such as the negative electrode active material, the conductive agent, and the binder, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0100] According to still some other embodiments of the present invention, the negative electrode plate may include a lithium metal sheet or a lithium alloy, etc., such as a lithium indium alloy.

[0101] According to yet some other embodiments of the present invention, the type of the separator is not particularly limited, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected. As an example, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0102] According to still other embodiments of the present invention, there is no specific limitation on the type of electrolyte, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel or all-solid-state. According to some specific embodiments of the present invention, the electrolyte adopts an electrolytic solution, and the electrolytic solution includes a lithium salt and a solvent.

[0103] According to some specific embodiments of the present invention, the lithium salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate or lithium tetrafluoro(oxalato)phosphate.

[0104] According to some specific embodiments of the present invention, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone or diethyl sulfone.

[0105] In some embodiments of the present application, the electrolytic solution may further optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0106] It should be noted that the features and advantages described above for the positive electrode sheet also apply to this solid-state battery and will not be elaborated here.

[0107] In the fifth aspect of the present invention, the present invention provides an electrical device. According to the embodiments of the present invention, the electrical device includes the above battery. According to the embodiments of the present invention, the electrical device may include, but is not limited to, mobile phones, laptop computers, electric vehicles, etc.

[0108] It should be noted that the features and advantages described above for the battery also apply to this electrical device and will not be elaborated here.

[0109] Hereinafter, embodiments of the present invention will be described. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention. For technologies or conditions not specified in the embodiments, they shall be carried out according to the technologies or conditions described in the literature in the art or according to the product specifications. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0110] Example 1

[0111] (1) Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in pure water according to a molar ratio of nickel element, cobalt element, and manganese element of 84:10:6 to obtain a mixed salt solution with a concentration of 2 mol / L. Prepare a sodium hydroxide solution with a concentration of 8 mol / L as a precipitant solution, and prepare an ammonia water solution with a concentration of 6 mol / L as a complexing agent solution. Purge nitrogen into the reaction kettle for protection, control the temperature of the reaction system at 60 °C, add the mixed salt solution, sodium hydroxide solution, and ammonia water into the reaction kettle through the inlet pipelines respectively, keep the stirring speed at 500 rpm, control the inlet volume of the mixed salt solution at 500 mL / h, control the ammonia content in the co-precipitation reaction system at 4.5 g / L, age for 1 h, separate, wash, and dry to obtain the precursor of the positive electrode active material;

[0112] (2) Weigh the above precursor, lithium hydroxide, tin oxide, and ammonium dihydrogen phosphate according to a molar ratio of the sum of nickel, cobalt, and manganese elements, lithium element, tin element, and phosphorus element in the precursor of 1:1.03:0.004:0.003 respectively, mix them evenly in a mixer, and sinter them at a constant temperature in an oxygen furnace. The oxygen concentration in the oxygen-containing gas in the oxygen furnace is greater than 95 vol%, the heating rate is 5 °C / min, the sintering temperature is 810 °C, and the sintering time is 10 h. After naturally cooling to room temperature, crush, screen, and remove iron to obtain the first-fired material of the positive electrode active material;

[0113] (3) Mix the first-fired material of the positive electrode active material and boric acid evenly in a high-speed mixer according to a molar ratio of the sum of transition metal elements in the first-fired material of the positive electrode active material to boron element of 1:0.001, sinter them at a constant temperature of 350 °C in an oxygen furnace. The oxygen concentration in the oxygen-containing gas in the oxygen furnace is greater than 90 vol%, the sintering time is 10 h. After cooling, screening, and removing iron, obtain the positive electrode active material Li 1.03 Ni 0.813 Co 0.100 Mn 0.060 Nb 0.004 P 0.003 O2@B. In the chemical formula of the positive electrode active material, the part before @ is the matrix component, and the main element in the coating layer is after @.

[0114] Examples 2 - 8 and Comparative Examples 1 - 4

[0115] Prepare the positive electrode active material according to the method of Example 1. The differences in the material composition and specific process conditions are shown in Table 1.

[0116] In Example 2, the dopant is tungsten trioxide and ammonium dihydrogen phosphate, and the coating agent is boric acid.

[0117] In Example 3, the dopant is vanadium trioxide and ammonium dihydrogen phosphate, and the coating agent is boric acid.

[0118] In Example 4, molybdenum oxide and boric acid are used as dopants, and tungsten trioxide is used as the coating agent.

[0119] In Example 5, tin oxide and boric acid are used as dopants, and tungsten trioxide is used as the coating agent.

[0120] In Example 6, boric acid is used as the dopant, and boric acid is used as the coating agent.

[0121] In Example 7, niobium pentoxide and boric acid are used as dopants, and boric acid is used as the coating agent.

[0122] In Example 8, tin oxide and ammonium dihydrogen phosphate are used as dopants, and no coating agent is used.

[0123] In Comparative Example 1, aluminum oxide is used as the dopant, and boric acid is used as the coating agent.

[0124] In Comparative Example 2, boric acid and ammonium dihydrogen phosphate are used as dopants, and no coating agent is used.

[0125] In Comparative Example 3, niobium pentoxide and ammonium dihydrogen phosphate are used as dopants, and boric acid is used as the coating agent.

[0126] In Comparative Example 4, niobium pentoxide and ammonium dihydrogen phosphate are used as dopants, and boric acid is used as the coating agent.

[0127] Table 1

[0128]

[0129]

[0130] Note: In Table 1, in Example 1, when the doping elements include Sn and P, the molar ratio of the precursor, lithium source, and dopant in terms of (Ni + Co + Mn) element, lithium element, and M element should be understood as the molar ratio of the precursor, lithium source, and dopant in terms of (Ni + Co + Mn) element, lithium element, Sn element, and P element. The same applies to other examples and comparative examples.

[0131] The precursors R (101) / R (001) and I (101) / I (001) obtained from Examples 2 - 8 and Comparative Examples 1 - 4, and the cathode active materials are shown in Table 2.

[0132] Table 2

[0133]

[0134]

[0135]

[0136] The average thickness A in the direction perpendicular to the (003) crystal plane in the microcrystals of the positive electrode active material obtained in Examples 2-8 and Comparative Examples 1-4 (003) , the (003) crystal plane spacing B in the microcrystals of the positive electrode active material (003) , the average thickness A in the direction perpendicular to the (104) crystal plane in the microcrystals of the positive electrode active material (104) , the (104) crystal plane spacing B in the microcrystals of the positive electrode active material (104) , the equivalent number of crystal plane sheets R of the positive electrode active material (003) and the equivalent number of crystal plane sheets R of the positive electrode active material (104) (104) as well as R (104) / R (003) As shown in Table 3

[0137] Table 3

[0138]

[0139] The positive electrode active materials obtained in Examples 1-8 and Comparative Examples 1-4 were assembled into 2025-type button cells, and the first-cycle Coulombic efficiency, cycling performance, rate performance, and lithium-ion diffusion coefficient of the cells were characterized. The characterization results are shown in Table 4

[0140] The preparation process of the 2025-type button cell is as follows

[0141] Preparation of the positive electrode sheet: The positive electrode active material, acetylene black, and polyvinylidene fluoride (PVDF) were thoroughly mixed in a mass ratio of 95:3:2 with an appropriate amount of N-methylpyrrolidone (NMP) to form a uniform slurry. The slurry was coated on both surfaces of the aluminum foil and dried at 120°C for 12 h, and then stamped into a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm under a pressure of 100 MPa. Among them, the loading amount of the positive electrode active material on the aluminum foil was 15-16 mg / cm 2 ;

[0142] Battery assembly: Inside a glove box filled with argon with a water content and an oxygen content both less than 5 ppm, the positive electrode sheet, separator, negative electrode sheet, and electrolyte were assembled into a 2025-type button cell and then left standing for 6 h. Among them, the negative electrode sheet used a metallic lithium sheet with a diameter of 17 mm and a thickness of 1 mm; the separator used a polyethylene porous membrane (Celgard 2325) with a thickness of 25 μm; the electrolyte included a lithium salt LiPF6 and a solvent (ethylene carbonate (EC) and diethyl carbonate (DEC) with a volume ratio of 1:1), and the concentration of LiPF6 in the electrolyte was 1 mol / L

[0143] First-cycle Coulombic efficiency test

[0144] At 25 °C, the battery is charged at a constant current of 0.1C to 4.4V, and then charged at a constant voltage to 0.02C to obtain the initial charging specific capacity C0 of the battery. Then, it is discharged at a constant current of 0.1C to 3.0V to obtain the initial discharging specific capacity C1 of the battery. The initial coulombic efficiency of the battery = C1 / C0 × 100%.

[0145] The charge-discharge voltage range is controlled to be 3.0 - 4.3V. At room temperature, the coin cell is subjected to charge-discharge tests at 0.1C to evaluate the electrochemical performance of the multi-component cathode material.

[0146] Cycling performance test: At 45 °C, the battery is charged at a constant current of 1C to 4.3V to obtain the initial charging specific capacity C2 of the battery. Then, it is discharged at a constant current of 1C to 3.0V, and then charged and discharged cyclically at a constant current of 1C for 80 cycles. Take the discharging specific capacity C 80 . The initial coulombic efficiency of the battery = C 80 / C2 × 100%.

[0147] Rate performance test: The charge-discharge voltage range is controlled to be 3.0 - 4.3V. At room temperature, the coin cell is charged and discharged cyclically 2 times at 0.1C, and then charged and discharged cyclically 1 time at 0.2C, 0.33C, 0.5C, and 1C respectively. The rate performance of the battery is characterized by the ratio of the initial discharging specific capacity at 0.1C to the discharging specific capacity at 1C. Among them, the initial discharging specific capacity at 0.1C is the discharging specific capacity of the coin cell in the 1st week cycle, and the discharging specific capacity at 1C is the discharging specific capacity of the coin cell in the 6th week cycle.

[0148] Diffusion coefficient test: EIS test and analysis are adopted. The battery is charged at a constant current of 0.1C to 4.3V, charged at a constant voltage for 30 min, and then discharged at a constant current of 0.1C to 3.0V; then it is charged at a constant current of 0.1C to 4.3V again. The fully charged half-cell is taken off, and EIS test is carried out in the frequency range of (100)kHz - 0.01Hz with an amplitude of 10mV. According to the following formula, the slope σ of the fitting line of Z re and ω -1 / 2 can be obtained:

[0149] Z re = R s + R ct + σω -1 / 2

[0150] ω = 2πf

[0151] Among them, Z re is the real part of the measured impedance spectrum, R s is the solution resistance, R ct is the charge transfer resistance, ω is the angular frequency, f is the test frequency, and σ is the Warburg factor.

[0152] According to the calculation formula of lithium ion diffusion coefficient, the bulk phase Li of the material is obtained + diffusion coefficient D Li + :

[0153] D Li + = R 2 T 2 / (2A 2 n 4 F 4 C 2 σ 2 )

[0154] Among them, R is the ideal gas constant, T is the absolute temperature, A is the cross-sectional area of the electrode, n is the number of electron transfers, F is the Faraday constant, and C is the lithium ion concentration in the electrode.

[0155] Table 4

[0156]

[0157] As can be seen from Table 3, the R of the positive electrode active material in Examples 1-8 (104) / R (003) is 1.4 - 1.8, while the R of the positive electrode active material in Comparative Examples 1-4 (104) / R (003) is not within the range of 1.4 - 1.8. As can be seen from Table 4, the first cycle Coulomb efficiency, rate performance, and capacity retention rate of the batteries in Examples 1-8 are significantly higher than those of the batteries in Comparative Examples 1-4. At the same time, the charge specific capacity, discharge specific capacity, and lithium ion diffusion coefficient can also be maintained within a suitable range. This shows that using a positive electrode active material with R (104) / R (003) of 1.4 - 1.8 can make the rate performance and cycle performance of the battery loaded with it excellent without sacrificing the capacity, initial efficiency, and lithium ion diffusion coefficient.

[0158] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0159] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material is a secondary particle, and the equivalent number of sheet layers R of the (003) crystal plane of the positive electrode active material (003) (003) and the equivalent number of sheet layers R of the (104) crystal plane (104) satisfy: R (104) / R (003) is 1.4 - 1.8, , , where A （003） is the average thickness in the direction perpendicular to the (003) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm, and B （003） is the crystal plane spacing of the (003) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm, and A （104） is the average thickness in the direction perpendicular to the (104) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm, and B （104） is the crystal plane spacing of the (104) crystal plane in the microcrystal of the positive electrode active material, with the unit of nm; The equivalent number of crystal plane sheet layers R of the positive electrode active material (003) (003) is 80 - 130; the equivalent number of crystal plane sheet layers R of the positive electrode active material (104) (104) is 150 - 200; The average thickness A in the direction perpendicular to the (003) crystal plane in the microcrystals of the positive electrode active material (003) is 35 nm to 55 nm; The positive electrode active material includes a matrix, and the matrix includes Li 1+a Ni x Co y Mn z M m O2, -0.05 ≤ a ≤ 0.3, 0.8 ≤ x < 1, 0 < y ≤ 0.2, 0 < z ≤ 0.2, 0.002 ≤ m ≤ 0.01, and M includes at least one of Sn, W, V, Mo, P, and B; The positive electrode active material further includes a coating layer formed on at least a part of the surface of the substrate; The method for preparing the positive electrode active material includes: providing a positive electrode active material precursor; performing a first mixed sintering on the positive electrode active material precursor, a lithium source, and a dopant containing element M to obtain a first-fired material of the positive electrode active material; performing a second mixed sintering on the first-fired material of the positive electrode active material and a coating agent containing element J to form a coating layer containing element J on at least a part of the surface of the first-fired material of the positive electrode active material, where the element J includes B or W.

2. The positive electrode active material according to claim 1, characterized in that, R (104) / R (003) is 1.55 - 1.

75.

3. The positive electrode active material according to claim 1 or 2, characterized in that, The equivalent number of crystal plane sheets R of the positive electrode active material (003) (003) is 90 - 120.

4. The positive electrode active material according to claim 1, wherein The average thickness A of the microcrystal of the positive electrode active material in the direction perpendicular to the (003) crystal plane (003) is 40 nm - 55 nm.

5. The positive electrode active material according to claim 1 or 2, characterized in that, The (003) crystal plane spacing B of the positive electrode active material (003) is 0.4730 nm - 0.4760 nm.

6. The positive electrode active material according to claim 5, characterized in that, The (003) crystal plane spacing B of the positive electrode active material (003) is 0.4735 nm - 0.4750 nm.

7. The cathode active material according to claim 5, characterized in that The average thickness A of the microcrystals of the positive electrode active material in the direction perpendicular to the (104) crystal plane (104) is 25 nm to 55 nm.

8. The positive electrode active material according to claim 7, wherein, The average thickness A in the direction perpendicular to the (104) crystal plane of the microcrystals of the positive electrode active material (104) is 30 nm to 50 nm.

9. The positive electrode active material according to claim 5, wherein The interplanar spacing B of the (104) crystal plane of the positive electrode active material (104) is 0.2030 nm to 0.2040 nm.

10. The cathode active material according to claim 9, characterized in that, The interplanar spacing B of the (104) crystal plane of the positive electrode active material (104) is 0.2035 nm - 0.2040 nm.

11. The positive electrode active material according to claim 1, wherein, The aspect ratio of the primary particles of the positive electrode active material is 2-5:

1.

12. The positive electrode active material according to claim 11, characterized in that, The aspect ratio of the primary particles of the positive electrode active material is 2-4:

1.

13. The cathode active material according to claim 11, wherein The sectional porosity of the positive electrode active material is 2%-10%.

14. The positive electrode active material according to claim 13, wherein The sectional porosity of the positive electrode active material is 3%-8%.

15. The positive electrode active material according to claim 11, wherein The BET specific surface area of the positive electrode active material is 0.4 m 2 / g - 0.9 m 2 / g.

16. The positive electrode active material according to claim 15, characterized in that, The BET specific surface area of the positive electrode active material is 0.5 m 2 / g - 0.8 m 2 / g.

17. A method for preparing the cathode active material according to any one of claims 1-16, characterized in that, including: providing a positive electrode active material precursor; performing a first mixed sintering on the positive electrode active material precursor, a lithium source, and a dopant containing element M to obtain a first-fired material of the positive electrode active material; performing a second mixed sintering on the first-fired material of the positive electrode active material and a coating agent containing element J to form a coating layer containing element J on at least a part of the surface of the first-fired material of the positive electrode active material.

18. The method according to claim 17, wherein The positive electrode active material precursor is prepared by the following method: mixing a nickel salt, a cobalt salt, a manganese salt, a precipitating agent, and ammonia water to perform a coprecipitation reaction to obtain the positive electrode active material precursor, wherein the temperature of the coprecipitation reaction is 50°C-80°C; the ammonia content during the coprecipitation reaction is 2 g / L-8 g / L.

19. The method according to claim 18, wherein The temperature of the coprecipitation reaction is 55°C-75°C; the ammonia content during the coprecipitation reaction is 3 g / L-7 g / L.

20. The method according to any one of claims 17 to 19, characterized in that, The positive electrode active material precursor satisfies at least one of the following conditions: The Dv50 of the positive electrode active material precursor is 9 μm-20 μm; The equivalent number of sheet layers R of the crystal plane of the positive electrode active material precursor (101) (101) and the equivalent number of sheet layers R of the (001) plane crystal plane of the positive electrode active material precursor (001) satisfy: R (101) / R (001) is 2.0 - 3.0; The peak intensity ratio I of the positive electrode active material precursor (101) / I (001) is 0.7 - 1.

4.

21. The method according to claim 20, wherein The peak intensity ratio I of the positive electrode active material precursor (101) / I (001) is 0.8 - 1.

2.

22. The method according to claim 17, wherein The temperature of the first mixed sintering is 650°C-900°C, and the time is 4 h-15 h.

23. The method according to claim 17, characterized in that The temperature of the second mixed sintering is 200°C-700°C, and the time is 3 h-10 h.

24. A positive electrode sheet, characterized in that, including the positive electrode active material according to any one of claims 1-16.

25. A battery, characterized in that, including the positive electrode sheet according to claim 24.

26. An electrical device, characterized in that, including the battery according to claim 25.

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