Coated ternary positive electrode material and preparation method thereof, positive electrode plate and lithium battery

Abstract

The invention discloses a coated ternary positive electrode material and a preparation method thereof, a positive electrode plate and a lithium battery, and relates to the technical field of lithium batteries. The coated ternary positive electrode material provided by the invention has the oxide coating layer containing W, Zr, Mo, Nb and Al, so that the interface stability, the particle mechanical strength and the lithium ion conductivity of the ternary positive electrode material can be remarkably improved, and the rate capability and the high-temperature and high-pressure cycle stability of the single-crystal ternary positive electrode material are finally enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and more particularly, to a coated ternary cathode material, a preparation method thereof, a cathode electrode sheet, and a lithium battery. Background Art

[0002] Under high voltage and high temperature conditions, the surface structural stability of single-crystal ternary cathode material particles will be significantly reduced, which will lead to the failure of battery performance. The dry coating process can improve the surface stability of the material to a certain extent, but the traditional dry coating process is difficult to achieve uniform coating, and the improvement effect on battery performance is limited.

[0003] In addition, the surface coating layer of traditional single-crystal ternary materials is mostly single / double compounds (such as Al2O3, LiAlO2), which cannot simultaneously meet the synergistic requirements of ionic conductivity, interfacial stability, and mechanical strength. Under high voltage (>4.5V), the coating layer is prone to react with the electrolyte and fail, and the difference in thermal expansion coefficient with the single-crystal matrix leads to interfacial peeling after cycling.

[0004] Therefore, there is an urgent need to improve the coating process of single-crystal ternary cathode materials to achieve the purpose of simultaneously improving ionic conductivity, interfacial stability, and mechanical strength, and ultimately enhancing the rate performance and high-temperature and high-pressure cycle stability of single-crystal ternary cathode materials.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a coated ternary cathode material, a preparation method thereof, a cathode electrode sheet, and a lithium battery, aiming to significantly improve the rate performance and high-temperature and high-pressure cycle stability of the ternary cathode material.

[0007] The present invention is implemented as follows:

[0008] In a first aspect, the present invention provides a coated ternary cathode material, including a core layer and an oxide coating layer coated on the core layer;

[0009] Among them, the core layer is a nickel-cobalt-manganese ternary cathode material;

[0010] The oxide coating layer contains W, Zr, Mo, Nb, and Al, and the molar ratio of W, Zr, Mo, Nb, and Al is (0.2-0.4):(0.1-0.3):(0.05-0.20):(0.1-0.3):(0.1-0.3).

[0011] In an optional embodiment, the molar ratio of the total amount of metal elements in the oxide coating layer to the total amount of nickel, cobalt, and manganese in the core layer is (0.5-2.0):100;

[0012] And / or, the chemical formula of the nickel-cobalt-manganese ternary cathode material is LiNi x Co y Mn z O2, where 0.6 < x < 0.7, 0.1 < y < 0.2, and 0.2 < z < 0.3.

[0013] In a second aspect, the present invention provides a method for preparing the coated ternary cathode material of the foregoing embodiment, including: forming an oxide coating layer containing W, Zr, Mo, Nb, and Al on the surface of the nickel-cobalt-manganese ternary cathode material.

[0014] In an optional embodiment, it includes: preparing a raw material solution for forming the oxide coating layer, placing the nickel-cobalt-manganese ternary cathode material in a spray fluidized bed cavity, atomizing the raw material solution and spraying it on the surface of the nickel-cobalt-manganese ternary cathode material, and then calcining.

[0015] In an optional embodiment, the raw material solution includes a first aqueous solution and a second aqueous solution. The first aqueous solution is prepared by dissolving ammonium tungstate pentahydrate, ammonium molybdate tetrahydrate, and ammonium oxalate niobate hydrate in water, and the mass fraction of the first aqueous solution is 40% - 60%;

[0016] The second aqueous solution is prepared by dissolving zirconium nitrate and aluminum nitrate in water, and the mass fraction of the second aqueous solution is 70% - 80%.

[0017] In an optional embodiment, bottom-air inlet type spray fluidized bed is used for coating, controlling the inlet air temperature to be 110°C - 120°C, and the fan frequency to be 40Hz - 60Hz;

[0018] And / or, preheat the nickel-cobalt-manganese ternary cathode material for 10 min - 30 min and then spray the raw material solution. During the spraying of the raw material solution, control the nozzle pressure of the fluidized bed to be 0.1 MPa - 0.3 MPa, and the peristaltic pump frequency to be 5 Hz - 20 Hz.

[0019] In an optional embodiment, control the calcination temperature to be 800°C - 950°C, and the calcination time to be 5 h - 8 h;

[0020] And / or, carry out the calcination in an oxygen atmosphere.

[0021] In an optional embodiment, the preparation process of the nickel-cobalt-manganese ternary cathode material includes: mixing the nickel-cobalt-manganese hydroxide precursor and the lithium source, and in an oxygen-containing atmosphere, first keep it at 500°C - 600°C for 3 h - 7 h, and then keep it at 900°C - 950°C for 8 h - 12 h;

[0022] Preferably, control the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt, and manganese to be (1.03 - 1.06):1.

[0023] In a third aspect, the present invention provides a positive electrode sheet, which includes the coated ternary positive electrode material in any of the foregoing embodiments or the coated ternary positive electrode material prepared by the preparation method in any of the foregoing embodiments.

[0024] In a fourth aspect, the present invention provides a lithium battery, which includes the positive electrode sheet of the foregoing embodiment.

[0025] The present invention has the following beneficial effects: The coated ternary positive electrode material provided by the present invention has an oxide coating layer containing W, Zr, Mo, Nb, and Al, which can significantly improve the interfacial stability, particle mechanical strength, and lithium ion conductivity of the ternary positive electrode material, and ultimately enhance the rate performance and high-temperature and high-pressure cycle stability of the single crystal ternary positive electrode material.

[0026] It should be noted that the coated ternary positive electrode material provided by the present invention contains high-entropy oxides of five elements, W, Zr, Mo, Nb, and Al. The high-entropy compound coating has the following functions:

[0027] (1) Inhibiting electrolyte decomposition: The high-entropy oxide coating layer effectively inhibits the side reactions between the electrode and the electrolyte;

[0028] (2) Improving interfacial stability: Each element has a high binding energy with lattice oxygen, which can significantly inhibit the loss of lattice oxygen on the surface of the single crystal ternary positive electrode material at high voltage or high temperature, and inhibit the irreversible phase change of the surface structure;

[0029] (3) Improving interfacial mechanical strength: By controlling the calcination temperature (800 - 950 °C), a thin heterogeneous structure coexisting with lamellar (R-3m), spinel phase (Fd-3m), and rock salt phase (Fm-3m) is formed from the inside out on the particle surface, enhancing the mechanical stability and surface structure stability of the surface of the single crystal ternary material;

[0030] (4) Improving ionic conductivity: Some high-valent cations are incorporated into the surface lattice, which can broaden the lithium ion transmission channels and induce the formation of some surface lithium ion conductors, thereby enhancing the interfacial kinetics of lithium ions. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 SEM image of the coated ternary positive electrode material prepared in Example 1;

[0033] Figure 2SEM image of the coated ternary cathode material prepared in Example 2;

[0034] Figure 3 SEM image of the coated ternary cathode material prepared in Example 3;

[0035] Figure 4 SEM image of the ternary cathode material prepared in Comparative Example 1. Detailed implementation manners

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0037] The embodiments of the present invention provide a coated ternary cathode material, which includes a core layer and an oxide coating layer coated on the core layer, forming a core-shell structure. Among them, the core layer is a nickel-cobalt-manganese ternary cathode material, and the oxide coating layer contains a high-entropy oxide of five elements including W, Zr, Mo, Nb, and Al.

[0038] In the oxide coating layer, the molar ratio of W, Zr, Mo, Nb, and Al is (0.2 - 0.4):(0.1 - 0.3):(0.05 - 0.20):(0.1 - 0.3):(0.1 - 0.3), such as 0.2:0.1:0.05:0.1:0.1, 0.3:0.2:0.10:0.2:0.2, 0.4:0.3:0.20:0.3:0.3, etc. Through the synergistic cooperation of the above five elements and by regulating the dosage ratio of each element, the purpose of significantly improving the interface stability, particle mechanical strength, and lithium-ion conductivity of the single-crystal ternary cathode material can be achieved, and finally the rate performance and high-temperature high-pressure cycle stability of the single-crystal ternary cathode material are enhanced.

[0039] In some embodiments, the molar ratio of the total amount of metal elements in the oxide coating layer to the total amount of nickel, cobalt, and manganese in the core layer is (0.5 - 2.0):100, such as 0.5:100, 1.0:100, 1.5:100, 2.0:100, etc. The total amount of the five elements in the oxide coating layer is preferably within the above range. Excessive or too little doping amount will affect the electrochemical performance of the cathode material and is not conducive to obtaining excellent rate performance and cycle performance.

[0040] In some embodiments, the chemical formula of the nickel-cobalt-manganese ternary cathode material is LiNi x Co y Mn zO2, where 0.6 < x < 0.7, 0.1 < y < 0.2, 0.2 < z < 0.3. It is advisable that the values of x, y, and z satisfy the above ranges, and all are suitable for forming a coating layer of high-entropy oxide, which can significantly improve the rate performance and cycling performance. Specifically, the chemical formula of the nickel-cobalt-manganese ternary cathode material can be LiNi 0.65 Co 0.10 Mn 0.25 O2, but not limited thereto.

[0041] An embodiment of the present invention provides a method for preparing a coated ternary cathode material, which forms an oxide coating layer containing W, Zr, Mo, Nb, and Al on the surface of the nickel-cobalt-manganese ternary cathode material, which is beneficial to improving the rate performance and high-temperature and high-pressure cycling performance of the cathode material, and the coating method is not limited.

[0042] To improve the uniformity of the coating, the inventor optimized the coating process and used a spray fluidized bed for coating, which can significantly improve the coating uniformity compared with the traditional dry coating process. The steps are as follows:

[0043] S1. Provide a nickel-cobalt-manganese ternary cathode material

[0044] The nickel-cobalt-manganese ternary cathode material can be a commercially available material or can be prepared independently.

[0045] In some embodiments, the preparation process of the nickel-cobalt-manganese ternary cathode material includes: mixing a nickel-cobalt-manganese hydroxide precursor and a lithium source, and sintering in an oxygen-containing atmosphere. The ratio of nickel, cobalt, and manganese is adjusted according to the chemical formula of the ternary cathode material matrix in the target product. The sintering process can adopt a segmented sintering method. First, keep the temperature at 500°C - 600°C for 3h - 7h, then keep the temperature at 900°C - 950°C for 8h - 12h, and then naturally cool and crush the material to obtain the nickel-cobalt-manganese ternary cathode material.

[0046] Specifically, stepwise sintering can be carried out in a muffle furnace. First, raise the temperature at a heating rate of 2°C / min - 4°C / min to the sintering temperature of the first stage (500°C - 600°C), such as 500°C, 550°C, 600°C, etc., and the holding time can be 3h, 4h, 5h, 6h, 7h, etc.; then continue to raise the temperature to the sintering temperature of the second stage (900°C - 950°C), such as 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, etc., and the holding time can be 8h, 9h, 10h, 11h, 12h, etc.

[0047] Further, by controlling the amount of the lithium source, the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt, and manganese is (1.03 - 1.06):1, such as 1.03:1, 1.04:1, 1.05:1, 1.06:1, etc., and it is appropriate that lithium is slightly in excess. Specifically, the lithium source can be lithium hydroxide, but is not limited thereto.

[0048] S2. Prepare the raw material solution for forming the oxide coating layer

[0049] Prepare the raw material solution for forming the oxide coating layer. The raw material solution needs to contain elements such as W, Zr, Mo, Nb, and Al. The raw material solution can be a single solution or 2 - 5 solutions, which can be adjusted according to different raw materials. The molar ratio of each element in the raw material solution meets the preset requirements, that is, the molar ratio of W, Zr, Mo, Nb, and Al is (0.2 - 0.4):(0.1 - 0.3):(0.05 - 0.20):(0.1 - 0.3):(0.1 - 0.3).

[0050] In some embodiments, the raw material solution includes a first aqueous solution and a second aqueous solution. The first aqueous solution is prepared by dissolving ammonium tungstate pentahydrate, ammonium molybdate tetrahydrate, and ammonium oxalate niobate hydrate in water. The mass fraction of the first aqueous solution is 40% - 60%, and this mass fraction refers to the total concentration of the raw materials, which can be 40%, 50%, 60%, etc. The second aqueous solution is prepared by dissolving zirconium nitrate and aluminum nitrate in water. The mass fraction of the second aqueous solution is 70% - 80%, and this mass fraction refers to the total mass fraction of zirconium nitrate and aluminum nitrate, which can be 70%, 75%, 80%, etc. The first aqueous solution is alkaline, and the second aqueous solution should not be premixed with the first aqueous solution to prevent zirconium and aluminum from depositing prematurely and affecting the uniformity of the coating.

[0051] S3. Form the coating using a spray fluidized bed

[0052] Place the nickel - cobalt - manganese ternary cathode material in the spray fluidized bed cavity. After atomizing the raw material solution, spray it on the surface of the nickel - cobalt - manganese ternary cathode material, so that the atomized solution can fully contact with the fluidized single - crystal ternary cathode particles and dry and deposit on the surface. The coating process provided by the embodiments of the present invention is simple and easy to implement, and the coating uniformity is higher.

[0053] In some embodiments, a bottom - inlet spray fluidized bed is used for coating. Control the inlet air temperature to be 110°C - 120°C and the fan frequency to be 40Hz - 60Hz. By adjusting the inlet air temperature and the fan frequency, the water in the solution can be quickly volatilized to form a coating layer. Specifically, the inlet air temperature can be 110°C, 115°C, 120°C, etc.; the fan frequency can be 40Hz, 50Hz, 60Hz, etc.

[0054] Further, the nickel-cobalt-manganese ternary cathode material can be preheated for 10 min - 30 min before spraying the raw material liquid. During the spraying of the raw material liquid, the nozzle pressure of the fluidized bed is controlled to be 0.1 MPa - 0.3 MPa, and the peristaltic pump frequency is 5 Hz - 20 Hz, so that the raw material liquid can be sprayed more evenly onto the nickel-cobalt-manganese ternary cathode material to form a uniform coating. Specifically, the preheating time can be 10 min, 20 min, 30 min, etc.; the nozzle pressure of the fluidized bed can be 0.1 MPa, 0.2 MPa, 0.3 MPa, etc., and the peristaltic pump frequency can be 5 Hz, 10 Hz, 15 Hz, 20 Hz, etc.

[0055] S4. Calcination

[0056] After the spraying in step S3 is completed, the material is collected for calcination, and a high-entropy oxide coating layer is formed after calcination.

[0057] In some embodiments, the calcination is carried out in an oxygen atmosphere, the calcination temperature is controlled to be 800 °C - 950 °C, and the calcination time is 5 h - 8 h. By regulating the calcination temperature and time, a heterogeneous structure with a thin layered (R-3m), spinel phase (Fd-3m), and rock salt phase (Fm-3m) coexisting from the inside to the outside is formed on the particle surface, enhancing the mechanical stability and surface structure stability of the surface of the single-crystal ternary material.

[0058] Specifically, the calcination temperature can be 800 °C, 850 °C, 900 °C, 950 °C, etc., and the calcination time can be 5 h, 6 h, 7 h, 8 h, etc.

[0059] An embodiment of the present invention also provides a positive electrode sheet, including the coated ternary cathode material provided by the embodiment of the present invention. By improving the ternary cathode material, it is beneficial to improve the rate performance and high-temperature and high-pressure cycle stability of the material. Specifically, the positive electrode sheet includes a positive electrode current collector, and a positive electrode active coating is formed on the positive electrode current collector, and the coated ternary cathode material is the main material of the positive electrode active coating.

[0060] An embodiment of the present invention provides a lithium battery, including the positive electrode sheet provided by the embodiment of the present invention, and may also include a negative electrode sheet, an electrode liquid, etc. Due to the improvement of the positive electrode material, this lithium battery has good rate performance and high-temperature and high-pressure cycle stability, and has good market application prospects.

[0061] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.

[0062] Example 1

[0063] This embodiment provides a preparation method of a coated ternary cathode material, and the steps are as follows:

[0064] Put Ni 0.65 Co0.10 Mn 0.25 (OH)2 precursor is mixed with 5% excess LiOH (i.e., the molar ratio of lithium in LiOH to the total amount of nickel, cobalt and manganese is 1.05:1), and is placed in a high-purity oxygen muffle furnace for step sintering: it is heated to 550 °C at a rate of 3 °C / min and held for 5 h, then heated to 930 °C and kept at a constant temperature for 10 h. After cooling, it is crushed to obtain the nickel-cobalt-manganese ternary cathode material. 5 kg of the collected nickel-cobalt-manganese ternary cathode material is placed in a bottom-air inlet fluidized bed cavity, the inlet air temperature is 115 °C, the fan frequency is 50 Hz, and the material is preheated for 15 min.

[0065] Ammonium tungstate pentahydrate, ammonium molybdate tetrahydrate, and ammonium niobium oxalate hydrate in stoichiometric ratio are dissolved in water to prepare solution A with a total mass fraction of 50%, and zirconium nitrate pentahydrate and aluminum nitrate nonahydrate are dissolved in water to prepare solution B with a total mass fraction of 80%. The molar ratio of W, Zr, Mo, Nb, and Al is controlled to be 0.3:0.2:0.1:0.2:0.2, and the total amount of metal elements in solution A and solution B is 0.5 mol% of the total content of Ni, Co, and Mn elements in the nickel-cobalt-manganese ternary cathode material. The nozzle pressure of the fluidized bed is adjusted to 0.2 MPa, the peristaltic pump frequency is 10 Hz, solution A and solution B are simultaneously pumped into the fluidized bed cavity, and the finally collected material is calcined at 880 °C for 6 h in an oxygen atmosphere and naturally cooled to obtain the cathode powder of Example 1.

[0066] The SEM of the powder prepared in Example 1 is as Figure 1 shown. It can be seen that the surface of the particles is relatively smooth.

[0067] Performance test: The cathode material, conductive agent (carbon black), and binder (PVDF) are mixed with N-methylpyrrolidone (NMP) in a ratio of 9:5:5 to make a slurry. After coating on aluminum foil, it is dried and formed and then cut into cathode sheets. Using a lithium sheet as the anode, 1M LiPF6 / EC-EMC-DMC (volume ratio 1:1:1) as the electrolyte to assemble a button cell. Electrochemical test conditions: voltage range of 2.8 - 4.5V, rate performance (25 °C) and cycle stability (45 °C) data are shown in Table 1.

[0068] Example 2

[0069] The difference from Example 1 is only that: the total amount of metal elements in solution A and solution B is 1.0 mol% of the total content of Ni, Co, and Mn elements in the nickel-cobalt-manganese ternary cathode material. The SEM of the powder prepared in Example 2 is as Figure 2 shown. It can be seen that the surface of the particles is still relatively smooth. Performance test: The test method refers to Example 1, and the rate performance (25 °C) and cycle stability (45 °C) data are shown in Table 1.

[0070] Example 3

[0071] The difference from Example 1 is only that: the total amount of metal elements in Solution A and Solution B is 2.0 mol% of the total content of Ni, Co, and Mn elements in the nickel-cobalt-manganese ternary cathode material. The SEM of the powder obtained in Example 3 is as shown in Figure 3 shown. It can be seen that obvious small particles appear on the surface of the particles. Performance test: The test method refers to Example 1, and the rate performance (25 °C) and cycle stability (45 °C) data are shown in Table 1.

[0072] Example 4

[0073] The difference from Example 2 is only that: in Solution A and Solution B, the molar ratio of W, Zr, Mo, Nb, and Al is 0.3:0.2:0.1:0.2:0.2. Performance test: The test method refers to Example 1, and the rate performance (25 °C) and cycle stability (45 °C) data are shown in Table 1.

[0074] Example 5

[0075] The difference from Example 2 is only that: in Solution A and Solution B, the molar ratio of W, Zr, Mo, Nb, and Al is 0.3:0.3:0.1:0.1:0.2. Performance test: The test method refers to Example 1, and the rate performance (25 °C) and cycle stability (45 °C) data are shown in Table 1.

[0076] Example 6

[0077] The difference from Example 2 is only that: in Solution A and Solution B, the molar ratio of W, Zr, Mo, Nb, and Al is 0.2:0.2:0.2:0.2:0.2. Performance test: The test method refers to Example 1, and the rate performance (25 °C) and cycle stability (45 °C) data are shown in Table 1.

[0078] Comparative Example 1

[0079] According to the stoichiometric ratio, mix Ni 0.65 Co 0.10 Mn 0.25 (OH)2 precursor with 5% excess LiOH, and place it in a high-purity oxygen muffle furnace for step sintering: heat it to 550 °C at 3 °C / min and hold for 5 h, then heat it to 930 °C and keep it constant for 10 h. After cooling, crush the matrix material to obtain the cathode material of Comparative Example 1.

[0080] The SEM of the powder obtained in Comparative Example 1 is as shown in Figure 4 shown. It can be seen that the surface of the particles is relatively smooth.

[0081] Performance test: The test method refers to Example 1, and the rate performance (25 °C) and cycle stability (45 °C) data are shown in Table 1.

[0082] Comparative Example 2

[0083] The difference from Example 2 is only that: ammonium niobium oxalate is not contained in Solution A, ammonium niobium oxalate is replaced by ammonium tungstate, and the total molar amount of metals in Solution A and Solution B is controlled to be unchanged. Performance test: The test method refers to Example 1, and the data of rate performance (25 °C) and cycle stability (45 °C) are shown in Table 1.

[0084] Comparative Example 3

[0085] The difference from Example 2 is only that: ammonium molybdate is not contained in Solution A, ammonium molybdate is replaced by ammonium tungstate, and the total molar amount of metals in Solution A and Solution B is controlled to be unchanged. Performance test: The test method refers to Example 1, and the data of rate performance (25 °C) and cycle stability (45 °C) are shown in Table 1.

[0086] Comparative Example 4

[0087] The difference from Example 2 is only that: zirconium nitrate pentahydrate is not contained in Solution B, zirconium nitrate pentahydrate is replaced by aluminum nitrate nonahydrate, and the total molar amount of metals in Solution A and Solution B is controlled to be unchanged. Performance test: The test method refers to Example 1, and the data of rate performance (25 °C) and cycle stability (45 °C) are shown in Table 1.

[0088] Table 1 Electrochemical performance of comparative examples and different examples

[0089]

[0090] As can be seen from Table 1, the coated ternary cathode material provided by the embodiments of the present invention has better rate performance and high-temperature and high-pressure cycle performance.

[0091] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A coated ternary cathode material, characterized in that, It includes a core layer and an oxide coating layer coated on the core layer; Among them, the core layer is a nickel-cobalt-manganese ternary cathode material; The oxide coating layer contains W, Zr, Mo, Nb, and Al, and the molar ratio of W, Zr, Mo, Nb, and Al is (0.2 - 0.4):(0.1 - 0.3):(0.05 - 0.20):(0.1 - 0.3):(0.1 - 0.3).

2. The coated ternary cathode material according to claim 1, wherein The molar ratio of the total amount of metal elements in the oxide coating layer to the total amount of nickel, cobalt, and manganese in the core layer is (0.5 - 2.0):100; And / or, the chemical formula of the nickel-cobalt-manganese ternary cathode material is LiNi x Co y Mn z O2, where 0.6 < x < 0.7, 0.1 < y < 0.2, and 0.2 < z < 0.

3.

3. The preparation method of the coated ternary cathode material according to claim 1 or 2, characterized in that, It includes: Form an oxide coating layer containing W, Zr, Mo, Nb, and Al on the surface of the nickel-cobalt-manganese ternary cathode material.

4. The preparation method according to claim 3, wherein It includes: Configure a raw material solution for forming the oxide coating layer, place the nickel-cobalt-manganese ternary cathode material in a spray fluidized bed cavity, atomize the raw material solution and spray it on the surface of the nickel-cobalt-manganese ternary cathode material, and then calcine.

5. The preparation method according to claim 4, wherein The raw material solution includes a first aqueous solution and a second aqueous solution. The first aqueous solution is prepared by dissolving ammonium tungstate pentahydrate, ammonium molybdate tetrahydrate, and ammonium oxalate niobate hydrate in water, and the mass fraction of the first aqueous solution is 40% - 60%; The second aqueous solution is prepared by dissolving zirconium nitrate and aluminum nitrate in water, and the mass fraction of the second aqueous solution is 70% - 80%.

6. The preparation method according to claim 4, wherein Use a bottom-air inlet type spray fluidized bed for coating, control the inlet air temperature to be 110°C - 120°C, and the fan frequency to be 40Hz - 60Hz; And / or, preheat the nickel-cobalt-manganese ternary cathode material for 10 min - 30 min and then spray the raw material solution. During the spraying of the raw material solution, control the nozzle pressure of the fluidized bed to be 0.1 MPa - 0.3 MPa, and the peristaltic pump frequency to be 5Hz - 20Hz.

7. The preparation method according to claim 4, characterized in that, Control the calcination temperature to be 800°C - 950°C, and the calcination time to be 5h - 8h; And / or, carry out calcination in an oxygen atmosphere.

8. The preparation method according to claim 3, wherein, The preparation process of the nickel-cobalt-manganese ternary cathode material includes: mixing a nickel-cobalt-manganese hydroxide precursor and a lithium source, in an oxygen-containing atmosphere, first keep it at 500°C - 600°C for 3h - 7h, and then keep it at 900°C - 950°C for 8h - 12h; Preferably, control the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt, and manganese to be (1.03 - 1.06):

1.

9. A positive electrode sheet, characterized in that, It includes the coated ternary cathode material described in any one of claims 1 - 2 or the coated ternary cathode material prepared by the preparation method described in any one of claims 3 - 8.

10. A lithium battery, characterized in that, It includes the positive electrode plate described in claim 9.

Images