Positive electrode material, preparation method thereof and application

Abstract

The present invention provides a cathode material, comprising: a cathode material matrix and a shell layer, the shell layer covering the surface of the cathode material matrix, the cathode material matrix comprising a framework and cathode material particles, the cathode material particles being loaded on the framework, the framework comprising a solid electrolyte, and a part of the solid electrolyte being doped into the crystal lattice of the cathode material particles, the chemical formula of the cathode material particles being LiNi<subgt;x< / subgt;Co<subgt;y< / subgt;M<subgt;(1‑x‑y)< / subgt>O<subgt;2< / subgt>, where 0.6 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.2, and M is Mn or / and Al; the shell layer comprises a solid electrolyte. The cathode material has high ionic conductivity, first charge-discharge efficiency, rate performance and cycle performance. At the same time, the battery prepared with this cathode material can reduce the usage amount of the liquid electrolyte, improve the energy density of the battery cell, and thus significantly improve the battery safety performance and reduce the battery production cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of technology, lithium-ion batteries have been widely used in various electronic products due to their many advantages such as high energy density, no memory effect, long cycle life, and environmental friendliness, especially driving the rapid development of electric vehicle technology. Current cathode materials such as ternary 523 materials, lithium iron phosphate, lithium cobaltate, and lithium manganate have more or less defects in terms of material cost, safety, and energy density, and cannot meet the important performance requirements of current fast charging, long endurance, high safety, and high energy density. High-nickel materials have very high specific capacity and excellent cycle performance, and are recognized as the future development mainstream product direction in the current lithium-ion cathode industry. However, a higher nickel content (0.6 ≤ Ni ≤ 1.0) leads to an increase in residual lithium on the cathode surface, which is likely to cause the homogenization failure due to too high viscosity during the electrode manufacturing process, and also leads to the deterioration of the storage performance and gas generation of the battery cell, bringing safety problems, which are the main problems restricting the application of high-nickel materials.

[0003] Therefore, the existing cathode materials need to be improved. Summary of the Invention

[0004] 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 cathode material, a preparation method thereof, and an application thereof. The cathode material has high ionic conductivity, first charge-discharge efficiency, rate performance, and cycle performance. At the same time, the battery prepared with this cathode material can reduce the amount of liquid electrolyte used, improve the energy density of the battery cell, and thus significantly improve the battery safety performance and reduce the battery production cost.

[0005] In one aspect of the present invention, a cathode material is provided. According to an embodiment of the present invention, the cathode material includes: a cathode material matrix, the cathode material matrix includes a framework and cathode material particles, the cathode material particles are loaded on the framework, the framework includes a solid electrolyte, and a part of the solid electrolyte is doped into the lattice of the cathode material particles. The chemical formula of the cathode material particles is LiNi x Co y M (1-x-y) O2, where 0.6 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.2, M is Mn and / or Al; a shell layer, the shell layer is coated on the surface of the cathode material matrix, and the shell layer includes a solid electrolyte.

[0006] The cathode material according to an embodiment of the present invention uses a solid electrolyte network as the skeleton of the cathode material matrix, and cathode material particles are loaded on the skeleton. The skeleton structure supports the cathode material particles, making the cathode material particles more stable, capable of resisting large-scale expansion and contraction of the material volume during charge and discharge, reducing the generation of microcracks, thereby improving the ionic conductivity, rate performance, and cycling performance of the cathode material. At the same time, part of the solid electrolyte is doped into the crystal lattice of the cathode material particles, which can support the layered structure of the cathode material, construct ion channels at the same time, improve the passing efficiency of ions and electrons, can supplement lithium ions during charge and discharge, improve the first charge-discharge efficiency of the cathode material, and increase the capacity. In addition, a shell layer formed by coating the solid electrolyte on the surface of the cathode material matrix, that is, a protective layer is constructed on the surface of the cathode material matrix. This protective layer allows lithium ions to quickly embed and escape, but isolates the direct contact between the electrolyte and the cathode material matrix, thereby reducing the corrosion of the electrolyte to the cathode material, reducing gas generation, and at the same time reducing the interfacial impedance and blocking the dissolution of Ni and Co. And the above shell layer enables the cathode material to withstand charge and discharge cycles at higher voltages, solving the problem of high-voltage fast charging. Thus, the cathode material has high ionic conductivity, first charge-discharge efficiency, rate performance, and cycling performance. At the same time, the battery prepared with this cathode material can reduce the usage amount of the liquid electrolyte, improve the energy density of the battery cell, and thus significantly improve the battery safety performance and reduce the battery production cost.

[0007] In addition, the cathode material according to the above embodiment of the present invention may further have the following additional technical features:

[0008] According to an embodiment of the present invention, the chemical formula of the solid electrolyte is Li 5+a La3Zr a M 2-a O 12 , where 0 ≤ a ≤ 2. Thus, the first charge-discharge efficiency and capacity of the cathode material can be improved.

[0009] According to an embodiment of the present invention, the thickness of the shell layer is 30 - 200 nm. Thus, gas generation can be reduced, thereby improving the safety performance of the cathode material.

[0010] In another aspect of the present invention, the present invention proposes a method for preparing the above cathode material. According to an embodiment of the present invention, the method includes:

[0011] (1) Mix a mixed salt containing nickel, cobalt, and M with a solid electrolyte, a precipitating agent, and a complexing agent for a precipitation reaction to obtain a solid electrolyte in-situ composite precursor;

[0012] (2) Mix the solid electrolyte in-situ composite precursor, a lithium source, and a solid electrolyte and then calcine in an oxygen atmosphere to obtain a cathode material matrix;

[0013] (3) Form a shell layer including the solid electrolyte on the positive electrode material matrix to obtain a positive electrode material.

[0014] According to the method for preparing the above positive electrode material according to the embodiments of the present invention, by mixing a mixed salt containing nickel-cobalt-M with a solid electrolyte, a precipitating agent, and a complexing agent to carry out a precipitation reaction, nickel-cobalt-M ions grow nickel-cobalt-M precipitates with the solid electrolyte as the nucleation and growth point under the action of the precipitating agent and the complexing agent. Then, the obtained in-situ composite precursor of the solid electrolyte, a lithium source, and the solid electrolyte are mixed and calcined in an oxygen atmosphere, and a positive electrode material matrix with a solid electrolyte network as the skeleton and positive electrode particles loaded on the skeleton structure can be obtained. The skeleton structure has a supporting effect on the positive electrode material particles, making the positive electrode material particles more stable, capable of resisting large-scale expansion and contraction of the material volume during charge and discharge, reducing the generation of microcracks, thereby improving the ionic conductivity, rate performance, and cycle performance of the positive electrode material. At the same time, during the calcination process, part of the solid electrolyte is doped into the lattice of the positive electrode material particles, which can support the layered structure of the positive electrode material, construct ion channels at the same time, improve the passing efficiency of ions and electrons, can supplement lithium ions during charge and discharge, improve the first charge-discharge efficiency of the positive electrode material, and increase the capacity. Finally, a shell layer formed by coating the solid electrolyte on the surface of the above positive electrode material matrix, that is, a protective layer is constructed on the surface of the positive electrode material matrix. This protective layer allows lithium ions to quickly embed and escape, but isolates the direct contact between the electrolyte and the positive electrode material matrix, thereby reducing the corrosion of the electrolyte to the positive electrode material, reducing gas generation, reducing the interfacial impedance at the same time, blocking the dissolution of Ni and Co, and the above shell layer enables the positive electrode material to withstand charge and discharge cycles at higher voltages, solving the problem of high-voltage fast charging. Thus, the above positive electrode material with high ionic conductivity, first charge-discharge efficiency, rate performance, and cycle performance can be prepared by using this method. The battery prepared with this positive electrode material can reduce the usage amount of the liquid electrolyte, improve the energy density of the battery cell, and further significantly improve the battery safety performance and reduce the battery production cost.

[0015] In addition, the method for preparing the positive electrode material according to the above embodiments of the present invention may further have the following additional technical features:

[0016] According to the embodiments of the present invention, in step (1), the mass ratio of the mixed salt containing nickel-cobalt-M to the solid electrolyte, the precipitating agent, and the complexing agent is (95% - 99%):(0.5‰ - 12‰):(0.2‰ - 1.2‰):(0.2‰ - 0.6‰). Thus, the positive electrode material has high ionic conductivity, first charge-discharge efficiency, rate performance, and cycle performance.

[0017] According to an embodiment of the present invention, in step (1), the molar ratio of nickel ions, manganese ions, and M ions in the mixed salt containing nickel and cobalt M is (6-9.5):(0.2-2):(0.3-2). Thereby, the positive electrode material has excellent specific capacity and cycling performance.

[0018] According to an embodiment of the present invention, in step (1), the complexing agent includes at least one of ammonia water, ammonium bicarbonate, ammonium sulfate, ammonium chloride, and ammonium nitrate.

[0019] According to an embodiment of the present invention, in step (1), during the precipitation reaction process, a pH regulator is used to control the pH of the mixed solution to be 11.5-12.5, the temperature of the precipitation reaction is 40-60°C, and the time is 6-8 h. Thereby, the ionic conductivity, rate performance, and cycling performance of the positive electrode material can be improved.

[0020] According to an embodiment of the present invention, in step (1), the particle size of the solid electrolyte in-situ composite precursor is 3-20.5 μm. Thereby, the ionic conductivity, rate performance, and cycling performance of the positive electrode material can be improved.

[0021] According to an embodiment of the present invention, in step (2), the solid electrolyte in-situ composite precursor, lithium source, solid electrolyte, and nano metal compound are mixed and then calcined in an oxygen atmosphere.

[0022] According to an embodiment of the present invention, the nano metal compound includes at least one of compounds of Mg, Al, Mo, Ta, Ga, Zr, W, Sr, Sc, and Ce.

[0023] According to an embodiment of the present invention, in step (2), the calcination temperature is 700-950°C, and the time is 12-22 h. Thereby, the ionic conductivity, rate performance, and cycling performance of the positive electrode material can be improved.

[0024] According to an embodiment of the present invention, in step (3), forming a shell layer including the solid electrolyte on the positive electrode material substrate is carried out by the following steps:

[0025] (3-1) Mix the positive electrode material substrate with water and the solid electrolyte and then dry it;

[0026] (3-2) Sinter the dried material obtained in step (3-1) in an oxygen-rich atmosphere to obtain the positive electrode material.

[0027] According to an embodiment of the present invention, in step (3-1), the mass ratio of the positive electrode material matrix to the solid electrolyte is (99.8% to 99.97%):(0.03% to 0.2%). Thus, the safety performance of the positive electrode material can be improved.

[0028] According to an embodiment of the present invention, in step (3-2), the sintering temperature is 500 - 850 °C and the sintering time is 5 - 9 h. Thus, the safety performance of the positive electrode material can be improved.

[0029] In a third aspect of the present invention, the present invention provides a lithium-ion battery. According to an embodiment of the present invention, the lithium-ion battery includes the above positive electrode material or the positive electrode material obtained by the above method. Thus, the lithium-ion battery can achieve fast charging, has a high energy density and good cycling performance. At the same time, the lithium-ion battery can reduce the amount of liquid electrolyte used, thereby significantly improving the battery safety performance and reducing the battery production cost.

[0030] In a fourth aspect of the present invention, the present invention provides a vehicle. According to an embodiment of the present invention, the vehicle includes the above lithium-ion battery. Thus, the vehicle has a high cruising range, fast charging performance and high safety performance.

[0031] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0032] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0033] Figure 1 is a schematic flowchart of a method for preparing a positive electrode material according to an embodiment of the present invention. Detailed Embodiments

[0034] The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0035] In one aspect of the present invention, the present invention provides a positive electrode material. According to an embodiment of the present invention, the positive electrode material includes: a positive electrode material matrix and a shell layer.

[0036] According to an embodiment of the present invention, the positive electrode material matrix includes a framework and positive electrode material particles. The positive electrode material particles are loaded on the framework. The framework includes a solid electrolyte, and part of the solid electrolyte is doped into the lattice of the positive electrode material particles. The chemical formula of the positive electrode material particles is LiNi x Co y M (1-x-y)O2, where 0.6 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.2, M is Mn and / or Al, and the positive electrode material particles are polycrystalline or single-crystalline. The inventors found that by using a solid electrolyte network as the framework of the positive electrode material matrix and loading the positive electrode material particles with the above composition on the framework, the framework structure supports the positive electrode material particles, making the positive electrode material particles more stable and able to resist the large expansion and contraction of the material volume during charge and discharge, reducing the generation of microcracks, thereby improving the ionic conductivity, rate performance, and cycling performance of the positive electrode material. At the same time, part of the solid electrolyte is doped into the lattice of the positive electrode material particles, which can support the layered structure of the positive electrode material, construct ion channels at the same time, improve the passing efficiency of ions and electrons, can supplement lithium ions during charge and discharge, improve the first charge and discharge efficiency of the positive electrode material, and increase the capacity.

[0037] According to an embodiment of the present invention, the shell layer is coated on the surface of the positive electrode material matrix, and the shell layer includes a solid electrolyte. The inventors found that by coating a shell layer of solid electrolyte on the surface of the obtained positive electrode material matrix, that is, constructing a protective layer on the surface of the positive electrode material matrix, this protective layer allows lithium ions to be quickly embedded and extracted, but isolates the direct contact between the electrolyte and the positive electrode material matrix, thereby reducing the corrosion of the electrolyte to the positive electrode material, reducing gas generation, while reducing the interfacial impedance and blocking the dissolution of Ni and Co. And the above shell layer enables the positive electrode material to withstand charge and discharge cycles at higher voltages, solving the problem of high-voltage fast charging. Further, the chemical formula of the above solid electrolyte is Li 5+a La3Zr a M 2-a O 12 , where 0 ≤ a ≤ 2. And the thickness of the shell layer is 30 - 200 nm. Thus, the gas generation of the positive electrode material can be reduced while improving its charge and discharge cycle performance at high voltages.

[0038] Another aspect of the present invention proposes a method for preparing the above positive electrode material. According to an embodiment of the present invention, referring to Figure 1 , the method includes:

[0039] S100: Mix a mixed salt containing nickel, cobalt, and M with a solid electrolyte, a precipitating agent, and a complexing agent to carry out a precipitation reaction

[0040] In this step, under the condition that the rotational speed of the blender is ≥ 1300 rpm, the mixed salts of nickel cobalt M and the solid electrolyte are pre-mixed, and then mixed with the precipitant and complexing agent to undergo a precipitation reaction. Meanwhile, a pH regulator is used to control the pH of the precipitation reaction to be 11.5 - 12.5, and the temperature of the precipitation reaction is controlled to be 40 - 60 °C, and the time is 6 - 8 h. The nickel cobalt M ions grow nickel cobalt M precipitates with the solid electrolyte as the nucleation and growth point under the action of the precipitant and complexing agent. When the crystal grains grow to 3 - 20.5 μm, the crystal grains are separated, and then dried to obtain the in-situ composite precursor of the solid electrolyte, where M is manganese and / or aluminum.

[0041] Furthermore, those skilled in the art can select the type and concentration of the precipitant according to actual needs, as long as the precipitation of the above-mentioned nickel cobalt M ions can be achieved. For example, an alkali solution or soluble carbonate is used, corresponding to the formation of nickel cobalt M hydroxide precipitate or carbonate precipitate. It should be noted that the complexing agent is also a commonly used material in the preparation process of the cathode material, and those skilled in the art can select it according to actual needs. For example, the complexing agent includes at least one of ammonia water, ammonium bicarbonate, ammonium sulfate, ammonium chloride, and ammonium nitrate. And the chemical formula of the solid electrolyte is Li 5+a La3Zr a M 2-a O 12 , where 0 ≤ a ≤ 2, and the above-mentioned mixed salts are soluble salts, such as sulfates.

[0042] According to an embodiment of the present invention, the molar ratio of nickel ions, manganese ions, and M ions in the mixed salts containing nickel cobalt M is (6 - 9.5):(0.2 - 2):(0.3 - 2), and the mass ratio of the mixed salts containing nickel cobalt M to the solid electrolyte, precipitant, and complexing agent is (95% - 99%):(0.5‰ - 12‰):(0.2‰ - 1.2‰):(0.2‰ - 0.6‰). The inventor found that when the addition amount of the solid electrolyte is too low (<0.5‰), it will not significantly improve the material performance, while when it is too high (>12‰), the internal resistance and capacity will decrease significantly, and the addition amounts of the precipitant and complexing agent will directly affect the particle size and crystallization state of the material. Therefore, in this application, the mass ratio of the mixed salts containing nickel cobalt M to the solid electrolyte, precipitant, and complexing agent is (95% - 99%):(0.5‰ - 12‰):(0.2‰ - 1.2‰):(0.2‰ - 0.6‰) for the precipitation reaction, which can improve the material performance.

[0043] S200: Mix the in-situ composite precursor of the solid electrolyte, lithium source, and solid electrolyte and then sinter

[0044] In this step, the above-mentioned solid electrolyte in-situ composite precursor, lithium source and solid electrolyte are added to a high-speed mixer and fully mixed at a speed of 800-1600rpm. After mixing, the mixture is calcined at a high temperature in a positive electrode sintering oxygen atmosphere furnace. The calcination temperature is 700-950℃ and the time is 12-22h. The sintered material is then crushed, ground and sieved to obtain a positive electrode material matrix with a solid electrolyte network as a skeleton and positive electrode particles loaded on the skeleton structure. The skeleton structure has a supporting effect on the positive electrode material particles, making the positive electrode material particles more stable, and can resist the large-scale expansion and contraction of the material volume during the charge and discharge process, reducing the generation of microcracks, thereby improving the ion conductivity, rate performance and cycle performance of the positive electrode material. At the same time, during the calcination process, part of the solid electrolyte is doped into the positive electrode material particle lattice, which can support the positive electrode material layered structure, while constructing ion channels, improving the efficiency of ions and electrons passing through, and replenishing lithium ions during the charge and discharge process, improving the first charge and discharge efficiency of the positive electrode material, and improving the capacity.

[0045] Furthermore, the above-mentioned solid electrolyte in-situ composite precursor, lithium source and solid electrolyte are mixed in a molar ratio of (99.8% to 99.97%): (100% to 112%): (0.03% to 0.2%). The inventors found that solid electrolytes can stabilize the structure of positive electrode materials to a certain extent and have the effect of improving the first effect, but as an additive, they do not provide capacity. Too much addition will lead to a decrease in the overall electrical performance of the material, and the cost will also increase significantly. Therefore, the present application adopts a solid electrolyte in-situ composite precursor, lithium source and solid electrolyte in a molar ratio of (99.8% to 99.97%): (100% to 112%): (0.03% to 0.2%). It can stabilize the material structure while maintaining the overall electrical properties of the material and improve the first effect. It should be noted that those skilled in the art can select the lithium source according to actual needs. For example, the lithium source is at least one of lithium hydroxide monohydrate, lithium carbonate, lithium nitrate and lithium acetate.

[0046] Furthermore, nano metal salts can be added during the mixing process, that is, the in-situ composite precursor of the solid electrolyte, the lithium source, the solid electrolyte, and the nano metal compound are mixed and then calcined in an oxygen atmosphere. Some metal ions enter the lattice of the cathode material through chemical reactions under the action of high temperature. During the process of lithium ion insertion and extraction in the material, it helps to stabilize the layer structure of the material, significantly improving the safety performance and cycling performance of the material. It should be noted that those skilled in the art can select the specific type of nano metal compound according to actual needs. For example, the nano metal compound includes at least one of compounds of Mg, Al, Mo, Ta, Ga, Zr, W, Sr, Sc, and Ce, and the corresponding compound is a metal oxide or a metal hydroxide.

[0047] S300: Form a solid electrolyte shell layer on the cathode material substrate

[0048] In this step, first, the above-obtained cathode material substrate is added with water to prepare a slurry with a solid content of 30 - 50 wt%, the temperature of the slurry is adjusted to 20 - 40 °C, then the solid electrolyte is added and stirred at a rotation speed of 15 - 40 rpm for 20 - 45 min under constant temperature conditions and then vacuum dried. The dried material is placed in an oxygen atmosphere furnace and sintered at a temperature of 500 - 850 °C for 5 - 9 h. At this temperature, the solid electrolyte partially melts on the surface of the cathode material particles to form a uniform and continuous coating shell layer. After sieving, the cathode material with a solid electrolyte shell layer can be obtained. The inventor found that by coating a shell layer of solid electrolyte on the surface of the above cathode material substrate, that is, constructing a protective layer on the surface of the cathode material substrate, this protective layer allows lithium ions to be quickly inserted and extracted, but isolates the direct contact between the electrolyte and the cathode material substrate, thereby reducing the corrosion of the electrolyte to the cathode material, reducing gas generation, and at the same time reducing the interfacial impedance and blocking the dissolution of Ni and Co. And the above shell layer enables the cathode material to withstand charge and discharge cycles at higher voltages, solving the problem of high-voltage fast charging.

[0049] Furthermore, in this step S300, the mass ratio of the cathode material substrate to the solid electrolyte is (99.8% - 99.97%):(0.03% - 0.2%). The inventor found that when constructing a protective shell layer on the particle surface by adding a too high proportion of solid electrolyte, although the safety performance is good, the dense and thick outer shell seriously hinders the channels for lithium ions to enter and exit, resulting in a very obvious reduction in the electrical performance of the material; if the addition ratio of the solid electrolyte is too low, there will be many holes in the protective layer of the material, and the application performance and safety performance of the material will decay rapidly, and the optimization effect is not obvious.

[0050] Thus, by using this method, the above-mentioned cathode material with high ionic conductivity, first charge-discharge efficiency, rate performance, and cycling performance can be prepared. The battery prepared with this cathode material can reduce the amount of liquid electrolyte used, improve the energy density of the battery cell, and thus significantly improve the battery safety performance and reduce the battery production cost.

[0051] It should be noted that the characteristics and advantages described above for the cathode material also apply to the method for preparing this cathode material, and will not be elaborated here.

[0052] In the third aspect of the present invention, the present invention provides a lithium-ion battery. According to an embodiment of the present invention, the lithium-ion battery includes the above-mentioned cathode material or the cathode material obtained by using the above-mentioned method. Thus, the lithium-ion battery can achieve fast charging, has a high energy density and good cycling performance. At the same time, the lithium-ion battery can reduce the amount of liquid electrolyte used, and thus significantly improve the battery safety performance and reduce the battery production cost. It should be noted that the characteristics and advantages described above for the cathode material and its preparation method also apply to the lithium-ion battery, and will not be elaborated here.

[0053] In the fourth aspect of the present invention, the present invention provides a vehicle. According to an embodiment of the present invention, the vehicle includes the above-mentioned lithium-ion battery. Thus, the vehicle has a high cruising range, fast charging performance, and high safety performance. It should be noted that the characteristics and advantages described above for the lithium-ion battery also apply to the vehicle, and will not be elaborated here.

[0054] Next, the present invention will be described with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0055] Example 1

[0056] (1) While stirring (the rotation speed is set at 1500 rpm), 0.1853 g of commercial solid electrolyte LLZMO powder is mixed with 208.2022 g of nickel-cobalt-manganese sulfate. Then, 0.0617 g of a precipitating agent (OH - with a concentration of 6.6 mol / L) and 0.0544 g of ammonia water (with a concentration of 1.2 mol / L) are added to the above-mentioned mixed solution and stirred to cause a precipitation reaction. Among them, the molar ratio of Ni 2+ , Co 2+ , and Mn 2+ in the nickel-cobalt-manganese sulfate mixed solution is 8:1:1. At the same time, the pH of the solution is adjusted to 11.6 with a pH regulator, and the precipitation reaction temperature is controlled at a constant temperature of 52 °C. The precipitation reaction time is 6 h to obtain grains with a particle size of 3.8 μm, which are then separated and dried to obtain a solid electrolyte in-situ composite precursor.

[0057] (2) Weigh 6.795 g of the above-mentioned solid electrolyte in-situ composite precursor, add 0.05 g of LLZMO and mix for 15 minutes, then add 3.186 g of lithium hydroxide powder, mix thoroughly in a high-speed mixer and grind for 30 minutes, then sinter at 845 ° C in a pure oxygen atmosphere for 13 hours, and pass through a 400 mesh sieve after ball milling to obtain the positive electrode material matrix.

[0058] (3) Weigh 6 g of the above-mentioned positive electrode material matrix and add deionized water to prepare a 30 wt% solid content slurry. The slurry temperature is adjusted to 30°C, and then weigh 0.015 g of LLZMO is added thereto and mixed and stirred. After stirring at 30 rpm for 20 min, vacuum drying is carried out. The dried powder is then sintered at 750°C for 6 h in a pure oxygen atmosphere and passed through a 400 mesh sieve to obtain a positive electrode material with a shell thickness of 90 to 150 nm.

[0059] Example 2

[0060] (1) With stirring (the speed was set at 1500 rpm), 208.2022 g of sulfate containing nickel, cobalt and manganese, 0.0617 g of precipitant (OH - The concentration of 6.6 mol / L) and 0.0544 g of ammonia water (concentration of 1.2 mol / L) were mixed and stirred to produce precipitation reaction, wherein Ni in the sulfate mixed solution 2+ 、Co 2+ , Mn 2+ The molar ratio is: 8:1:1, and the pH of the solution is adjusted to 11.6 with a pH regulator, and the precipitation reaction temperature is controlled to be constant at 52°C. The precipitation reaction time is 6 hours to obtain grains with a particle size of 3.8 μm, which are then separated and dried to obtain a solid electrolyte in-situ composite precursor.

[0061] (2) Weigh 6.795 g of the above precursor, add 0.05 g of LLZMO and mix for 15 min, then add 3.186 g of lithium hydroxide powder, mix thoroughly in a high-speed mixer and grind for 30 min, then sinter at 845 ° C in a pure oxygen atmosphere for 13 h, and pass through a 400 mesh sieve after ball milling to obtain the positive electrode material matrix.

[0062] (3) Weigh 6 g of the above-mentioned positive electrode material matrix and add deionized water to prepare a 30 wt% solid content slurry. The slurry temperature is adjusted to 30°C, and then weigh 0.015 g of LLZMO is added thereto and mixed and stirred. After stirring at 30 rpm for 20 min, vacuum drying is carried out. The dried powder is then sintered at 750°C for 6 h in a pure oxygen atmosphere and passed through a 400 mesh sieve to obtain a positive electrode material with a shell thickness of 90 to 150 nm.

[0063] Example 3

[0064] (1) With stirring (rotation speed set at 1500 rpm), 208.2022 g of nickel-cobalt-manganese sulfate, 0.0617 g of a precipitating agent (OH - with a concentration of 6.6 mol / L) and 0.0544 g of ammonia water (concentration of 1.2 mol / L) were mixed and stirred to undergo a precipitation reaction. Among them, in the sulfate mixed solution, the molar ratio of Ni 2+ , Co 2+ , and Mn 2+ was 8:1:1. At the same time, the pH of the solution was adjusted to 11.6 with a pH regulator, and the precipitation reaction temperature was controlled at a constant 52 °C. The precipitation reaction time was 6 h to obtain grains with a particle size of 3.8 μm, which were then separated and dried to obtain a solid electrolyte in-situ composite precursor.

[0065] (2) Weigh 6.795 g of the above precursor, add 3.186 g of lithium hydroxide fine powder, mix well in a high-speed mixer and grind for 30 min, then sinter at 845 °C for 13 h in a pure oxygen atmosphere, and after ball milling, pass through a 400-mesh sieve to obtain the cathode material matrix.

[0066] (3) Weigh 6 g of the above cathode material matrix, add deionized water to prepare a slurry with a solid content of 30 wt%, adjust the slurry temperature to 30 °C, then weigh 0.015 g of LLZMO and add it to mix and stir. After stirring at 30 rpm for 20 min, vacuum dry, and then sinter the dried powder at 750 °C for 6 h in a pure oxygen atmosphere, and pass through a 400-mesh sieve to obtain the cathode material, with a shell thickness of 90 - 150 nm.

[0067] Comparative Example 1

[0068] (1) With stirring (rotation speed set at 1500 rpm), 208.2022 g of nickel-cobalt-manganese sulfate, 0.0617 g of a precipitating agent (OH - with a concentration of 6.6 mol / L) and 0.0544 g of ammonia water (concentration of 1.2 mol / L) were mixed and stirred to undergo a precipitation reaction. Among them, in the sulfate mixed solution, the molar ratio of Ni 2+ , Co 2+ , and Mn 2+ was 8:1:1. At the same time, the pH of the solution was adjusted to 11.6 with a pH regulator, and the precipitation reaction temperature was controlled at a constant 52 °C. The precipitation reaction time was 6 h to obtain grains with a particle size of 3.8 μm, which were then separated and dried to obtain a solid electrolyte in-situ composite precursor.

[0069] (2) Weigh 6.795 g of the above precursor, add 3.186 g of lithium hydroxide fine powder, mix well in a high-speed mixer and grind for 30 min, then sinter at 845 °C for 13 h in a pure oxygen atmosphere, and after ball milling, pass through a 400-mesh sieve to obtain the cathode material matrix.

[0070] (3) Weigh 6 g of the above-mentioned cathode material matrix, add deionized water to prepare a slurry with a solid content of 30 wt%, adjust the temperature of the slurry to 30 °C, mix and stir. After stirring for 20 min at a rotation speed of 30 rpm, conduct vacuum drying. Then, sinter the dried powder in a pure oxygen atmosphere at 750 °C for 6 h, and pass it through a 400-mesh sieve to obtain the cathode material.

[0071] The process for testing the electrochemical performance of the cathode materials prepared in Examples 1-3 and Comparative Example 1 is as follows:

[0072] Respectively, uniformly mix the cathode materials prepared in Examples 1-3 and Comparative Example 1 with the conductive agent acetylene black and the binder PVDF (8% solid content) in a mass ratio of 90:5:5. Then, use NMP (N-methyl-pyrrolidone) to prepare a slurry with a solid content of 48% and moderate viscosity. Uniformly coat the slurry on the aluminum foil, conduct vacuum drying at 80 °C for 8 h, roll and cut it into circular pole pieces with a diameter of 14 mm. Weigh 6 pole pieces with similar masses and conduct vacuum drying for 12 h. In the glove box, use it as the positive electrode piece, use metallic lithium as the negative electrode, use a ceramic diaphragm as the separator, purchase a special electrolyte for high-nickel ternary materials as the electrolyte, assemble 2032 button cells, assemble 6 cells for each sample, and use a Blue CT2001 battery tester to conduct charge and discharge tests. The test temperature is kept constant at 25 °C. The voltage range for the electrochemical test is 3-4.3 V, the rate tests are 0.1C, 0.2C, 0.5C, 1C, 2C, and the cycle test is to test the performance of 1C charge and discharge for 100 cycles.

[0073] The test results of the electrochemical performance of the cathode materials prepared in Examples 1-3 and Comparative Example 1 are shown in Table 1.

[0074] Table 1

[0075]

[0076] 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 contradiction, 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.

[0077] 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 cathode material, characterized in that, Comprising: A cathode material matrix, the cathode material matrix comprising a framework and cathode material particles, the cathode material particles being loaded on the framework, the framework comprising a solid electrolyte, and a part of the solid electrolyte being doped into the lattice of the cathode material particles, the chemical formula of the cathode material particles being LiNi x Co y M (1-x-y) O2, where 0.6 ≤ x ≤ 0.95, 0.05 ≤ y ≤ 0.2, and M is Mn or / and Al; A shell layer, which is coated on the surface of the cathode material matrix, and the shell layer includes a solid electrolyte; The cathode material is prepared by the following method: (1) Mix a mixed salt containing nickel, cobalt, and M with a solid electrolyte, a precipitating agent, and a complexing agent for a precipitation reaction to obtain a solid electrolyte in-situ composite precursor; (2) Mix the solid electrolyte in-situ composite precursor, a lithium source, and a solid electrolyte, and then calcine in an oxygen atmosphere to obtain a cathode material matrix; (3) Form a shell layer including the solid electrolyte on the cathode material matrix to obtain a cathode material.

2. The cathode material according to claim 1, characterized in that, The chemical formula of the solid electrolyte is Li 5+ a La3Zr a M 2-a O 12 , where 0 ≤ a ≤ 2.

3. The cathode material according to claim 2, wherein, The thickness of the shell layer is 30 - 200 nm.

4. The cathode material according to claim 1, characterized in that, In step (1), the mass ratio of the mixed salt containing nickel, cobalt, and M to the solid electrolyte, the precipitating agent, and the complexing agent is (95% - 99%):(0.5‰ - 12‰):(0.2‰ - 1.2‰):(0.2‰ - 0.6‰).

5. The cathode material according to claim 4, characterized in that, The complexing agent includes at least one of ammonia water, ammonium bicarbonate, ammonium sulfate, ammonium chloride, and ammonium nitrate.

6. The cathode material according to claim 4, characterized in that, During the precipitation reaction process, a pH regulator is used to control the pH of the mixed solution to be 11.5 - 12.5, the temperature of the precipitation reaction is 40 - 60 °C, and the time is 6 - 8 h.

7. The cathode material according to claim 4, characterized in that, The particle size of the solid electrolyte in-situ composite precursor is 3 - 20.5 μm.

8. The cathode material according to claim 1, wherein, In step (2), the solid electrolyte in-situ composite precursor, a lithium source, a solid electrolyte, and a nano metal compound are mixed and then calcined in an oxygen atmosphere.

9. The cathode material according to claim 8, characterized in that, The nano metal compound includes at least one of compounds of Mg, compounds of Al, compounds of Mo, compounds of Ta, compounds of Ga, compounds of Zr, compounds of W, compounds of Sr, compounds of Sc, and compounds of Ce.

10. The cathode material according to claim 8, characterized in that, The temperature of the calcination is 700 - 950 °C, and the time is 12 - 22 h.

11. The cathode material according to claim 1, characterized in that, In step (3), forming a shell layer including the solid electrolyte on the cathode material matrix is carried out by the following steps: (3 - 1) Mix the cathode material matrix with water and a solid electrolyte and then dry; (3 - 2) Sinter the dried material obtained in step (3 - 1) in an oxygen-rich atmosphere to obtain a cathode material.

12. The cathode material according to claim 11, characterized in that, In step (3 - 1), the mass ratio of the cathode material matrix to the solid electrolyte is (99.8% - 99.97%):(0.03% - 0.2%).

13. The cathode material according to claim 11, characterized in that, In step (3 - 2), the sintering temperature is 500 - 850 °C, and the sintering time is 5 - 9 h.

14. A lithium-ion battery, characterized in that, Comprising the cathode material according to any one of claims 1 - 13.

15. A vehicle, characterized in that, The vehicle includes the lithium-ion battery according to claim 14.

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