A ternary cathode material, its preparation method and application

Abstract

This invention relates to the field of lithium-ion battery materials technology, and discloses a ternary cathode material, its preparation method, and its application. The preparation method of the ternary cathode material provided by this invention includes the following steps: S1 step: a first mixing of a ternary cathode material precursor, a lithium source, and an M element source, followed by a first sintering, to obtain a core; S2 step: dispersing the core in a solvent, and performing a second mixing with a first lithium supplement agent and a second lithium supplement agent to obtain an intermediate product; S3 step: mixing the intermediate product with a fast ion conductor precursor and performing a second sintering, to obtain the ternary cathode material. This invention, through synergistic modification of the cathode material by element doping, dual lithium supplementation, and fast ion conductor coating, maintains lattice structure stability, suppresses microcracks and metal dissolution, reduces lithium loss and interfacial side reactions, and possesses both excellent structural stability and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, specifically to a ternary cathode material, its preparation method, and its application. Background Technology

[0002] Low- and medium-nickel ternary cathode materials have broad application prospects in power batteries and energy storage due to their high specific capacity and good safety. According to the energy density formula E=QU, increasing the charging voltage U can significantly improve the energy density. Related studies show that the specific capacity and energy density of the low- and medium-nickel ternary cathode material NCM622 at a charging cutoff voltage of 4.5V are basically equivalent to those of the high-nickel ternary cathode material NCM811 at 4.3V. At the same energy density, the high-voltage technology is lower in cost and safer than higher nickel materials.

[0003] However, under high-voltage deep delithiation, low- and medium-nickel materials experience significant lattice stress due to anisotropic lattice contraction and expansion. In particular, the lattice stress mismatch between the (003) and (104) crystal planes easily leads to microcracks along grain boundaries in primary particles. These microcracks not only disrupt the integrity of the crystal structure but also provide channels for electrolyte penetration, thereby exacerbating subsequent side reactions. At the same time, high voltage also tends to result in short battery cycle life, leading to poor cycle stability under high voltage.

[0004] To address the aforementioned issues, current solutions include bulk doping and surface coating. While bulk doping can stabilize the structure, it cannot effectively solve the lattice stress mismatch problem. Traditional surface coatings, such as direct coating with metal oxides like Al₂O₃ and ZrO₂, can physically isolate the electrolyte, but these materials themselves are lithium-ion insulators, severely degrading the material's rate performance. Another approach is direct coating with fast-ion conductors, but this faces problems such as uneven coating, weak adhesion to the substrate, and easy detachment during cycling, leading to poor cycle performance. Therefore, developing a ternary cathode material that can simultaneously solve both lattice stress mismatch and cycle stability is of great significance. Summary of the Invention

[0005] This invention provides a ternary cathode material, its preparation method, and its application, in order to solve the problem that existing ternary cathode materials are prone to lattice stress mismatch under high pressure, resulting in poor structural stability and poor cycle performance.

[0006] In a first aspect, the present invention provides a method for preparing a ternary cathode material, comprising the following steps: Step S1: The ternary cathode material precursor, lithium source and M element source are first mixed, and then first sintered to obtain the core; the M element includes at least one of Zr, Al, Ti, Mg and W; Step S2: The kernel is dispersed in a solvent and mixed with a first lithium supplement and a second lithium supplement to obtain an intermediate product; the first lithium supplement includes Li2S and / or Li3N; the second lithium supplement includes lithium and a first metal element; the first metal element includes Al and / or Cu; Step S3: Mix the intermediate product and the fast ion conductor precursor and perform a second sintering to obtain the ternary cathode material.

[0007] In one optional implementation, in step S1, the chemical formula of the ternary cathode material precursor is Ni. x Co y Mn 1-x-y (OH)₂, where 0.5≤x≤0.8, 0.1≤y≤0.3, 0 <x+y<1。

[0008] In one alternative embodiment, the lithium source includes lithium hydroxide and / or lithium carbonate.

[0009] In one optional embodiment, the source of element M includes at least one of ZrO2, Al2O3, TiO2, MgO, and WO3.

[0010] In one optional embodiment, in step S1, the ratio of the total number of moles of nickel, cobalt, and manganese elements in the ternary cathode material to the number of moles of M element in the M element source is 1:0.0005-0.02.

[0011] In one optional embodiment, the ratio of the total molar number of nickel, cobalt, and manganese elements in the ternary cathode material precursor to the molar number of lithium elements in the lithium source is 1:1.01-1.05.

[0012] In one alternative embodiment, the first mixing speed is 200-400 rpm and the time is 20-40 min.

[0013] In one optional embodiment, the first sintering operation includes heating to 950-1050°C at a rate of 1-3°C / min and holding for 8-15 hours in an oxygen atmosphere; or heating from room temperature to 600-700°C at a rate of 2-5°C / min and holding for 2-4 hours in an oxygen atmosphere, and then heating to 950-1050°C at a rate of 1-3°C / min and holding for 8-15 hours.

[0014] In one alternative embodiment, the first sintering is followed by a step of cooling to room temperature at a rate of 0.5-1 °C / min.

[0015] In an optional embodiment, in step S2, the solvent includes ethanol and / or N-methylpyrrolidone.

[0016] In one alternative embodiment, the mass ratio of the core to the volume ratio of the solvent is 1 g: 3-5 mL.

[0017] In one alternative embodiment, the second lithium supplement includes LiAlO2 or Li2CuO2.

[0018] In one optional embodiment, the mass ratio of the first lithium supplement to the second lithium supplement is 2-5:1.

[0019] In one alternative implementation, the mass ratio of the core to the total mass of the first and second lithium supplements is 1:0.002-0.02.

[0020] In one alternative embodiment, the reaction is carried out at a speed of 200-400 rpm for 2-6 hours.

[0021] In one alternative embodiment, the reaction is further followed by a spray drying or vacuum drying step.

[0022] In one optional embodiment, the atomization pressure of the spray dryer is 0.4-0.8 MPa, the feed temperature is 55-75°C, and the feed rate is 8-12 mL / min.

[0023] In an optional implementation, in step S3, the chemical formula of the fast ion conductor precursor includes Li α 1N β1 (PO4) γ1 and / or Li α2 N β2 (SiO3) γ2 Wherein, N includes at least one of Fe, V, Mn, and Ti, and α1, β1, γ1, α2, β2, and γ2 are each positive integers that satisfy valence balance.

[0024] In one alternative embodiment, the mass ratio of the intermediate product to the fast ion conductor precursor is 60-100:1.

[0025] In one alternative implementation, the mixing linear velocity is 10-20 m / s, and the time is 10-30 min.

[0026] In one alternative embodiment, the second sintering temperature is 400-700°C and the time is 5-12 hours.

[0027] In one optional embodiment, the atmosphere for the second sintering is an oxygen-containing atmosphere; preferably, it is a mixed atmosphere containing inert gas and oxygen.

[0028] In one alternative embodiment, the fast ion conductor precursor is further doped with Nb.

[0029] In one optional embodiment, the oxygen-containing atmosphere is a mixture of inert gas and oxygen.

[0030] In one optional embodiment, the oxygen volume fraction of the oxygen-containing atmosphere is 5%-20%.

[0031] Secondly, the present invention provides a ternary cathode material prepared by the above-mentioned method for preparing ternary cathode materials.

[0032] Thirdly, the present invention provides a positive electrode sheet, comprising: Positive current collector, and A positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprising the aforementioned ternary positive electrode material.

[0033] Fourthly, the present invention provides a secondary battery comprising the aforementioned positive electrode sheet. Fifthly, the present invention provides an electrical device comprising the aforementioned secondary battery.

[0034] The technical solution of this invention has the following advantages: 1. The present invention provides a method for preparing a ternary cathode material, comprising the following steps: S1 step: mixing a ternary cathode material precursor, a lithium source, and a M element source in a first mixing, and then performing a first sintering to obtain a core; wherein the M element includes at least one of Zr, Al, Ti, Mg, and W; S2 step: dispersing the core in a solvent and mixing it in a second mixing with a first lithium supplementer and a second lithium supplementer to obtain an intermediate product; wherein the first lithium supplementer includes Li2S and / or Li3N; the second lithium supplementer includes lithium and a first metal element; wherein the first metal element includes Al and / or Cu; S3 step: mixing the intermediate product and a fast ion conductor precursor and performing a second sintering to obtain the ternary cathode material. The core is prepared by mixing a ternary cathode material precursor, a lithium source, and an M element source and then performing a first sintering. The M element can be at least one of Zr, Al, Ti, Mg, and W. Since these elements have stable valence states and moderate ionic radii, their uniform distribution in the lattice can strengthen the lattice structure, slow down lattice collapse during cycling, and achieve precise control of the lattice stress of the (003) and (104) crystal planes, thereby improving the structural stability of the material. Furthermore, the inner layer is replenished by using a first lithium replenishing agent including Li2S and / or Li3N and a second lithium replenishing agent including Al and / or Cu and lithium. This can continuously compensate for the loss of interfacial lithium and form a stable cathode electrolyte interfacial film during cycling. After lithium replenishment, the outer layer is coated by using a fast ion conductor precursor to achieve outer layer conduction, providing a high-speed lithium ion transport channel and constructing a stable, dense interfacial protective layer with high ionic conductivity, effectively protecting the internal material from electrolyte corrosion. The synergistic effect of inner-layer lithium replenishment and outer-layer conduction gives the resulting cathode material good structural and cycle stability. The process is simple and controllable, making it suitable for large-scale industrial production.

[0035] 2. The present invention provides a method for preparing a ternary cathode material. The first sintering operation involves heating from room temperature to 600-700℃ at a rate of 2-5℃ / min under an oxygen atmosphere, holding at that temperature for 2-4 hours, and then heating to 950-1050℃ at a rate of 1-3℃ / min, holding at that temperature for 8-15 hours. After the first sintering, a cooling process to room temperature at a rate of 0.5-1℃ / min is also included. Through the above-mentioned two-stage holding process (holding at 600-700℃ first and then at 950-1050℃) combined with a slow cooling rate (0.5-1℃ / min), the material can effectively suppress microcracks caused by anisotropic volume changes during high-pressure cycling, significantly improving structural stability.

[0036] 3. The present invention provides a ternary cathode material, which is prepared by the above-mentioned method for preparing ternary cathode materials. This material has a stable crystal structure, which can effectively suppress microcracks in particles and dissolution of metal ions, significantly reduce lithium element loss, and at the same time significantly alleviate interfacial side reactions. It has both excellent structural stability and cycle performance, and is suitable for the application requirements of high-performance batteries. Detailed Implementation

[0037] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0038] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0039] Example 1 This embodiment provides a method for preparing a ternary cathode material, including the following steps: (1) Take the nickel-cobalt-manganese hydroxide precursor Ni according to the ratio of total moles of nickel, cobalt, and manganese, moles of lithium, and moles of zirconium of 1:1.03:0.001. 0.6 Co 0.2 Mn 0.2 (OH)2, LiOH•H2O and ZrO2 were placed in a high-speed mixer and mixed at 300 rpm for 30 min. The mixture was then placed in an atmosphere furnace and sintered under an oxygen flow. The sintering program was as follows: the temperature was increased from room temperature to 650℃ at a rate of 3℃ / min and held for 3 h; then the temperature was increased to 980℃ at a rate of 2℃ / min and held for 12 h; finally, the temperature was decreased to room temperature at a rate of 0.8℃ / min to obtain the core. (2) Take 100g of the kernel obtained in step (1) and disperse it in 300mL of anhydrous ethanol. Add 0.2g of Li2S (first lithium supplement) and 0.08g of LiAlO2 (second lithium supplement). Stir and disperse at 300rpm for 4h. Then spray dry it. Set the atomization pressure to 0.6MPa, the feed temperature to 65℃, and the feed rate to 10mL / min. After drying, the intermediate product is obtained. (3) Take 40g of the intermediate product obtained in step (2) and add it together with 0.5g of Li3V2(PO4)3 into a high-speed mixer and mix at a linear speed of 15m / s for 20min; then carry out the second sintering at 550℃ for 8h in a mixed atmosphere of oxygen and argon (oxygen volume fraction of 10%) to obtain ternary cathode material.

[0040] Example 2 This embodiment provides a method for preparing a ternary cathode material, including the following steps: (1) Take the nickel-cobalt-manganese hydroxide precursor Ni according to the ratio of total moles of nickel, cobalt, and manganese, moles of lithium, and moles of zirconium of 1:1.01:0.0005. 0.6 Co 0.2 Mn 0.2 (OH)2, LiOH•H2O and ZrO2 were placed in a high-speed mixer and mixed at 200 rpm for 40 min. The mixture was then placed in an atmosphere furnace and sintered under an oxygen flow. The sintering program was as follows: the temperature was increased from room temperature to 600℃ at a rate of 2℃ / min and held for 4 h; then the temperature was increased to 950℃ at a rate of 1℃ / min and held for 15 h; finally, the temperature was decreased to room temperature at a rate of 0.6℃ / min to obtain the core. (2) Take 100g of the kernel obtained in step (1) and disperse it in 400mL of anhydrous ethanol. Add 0.3g of Li2S (first lithium supplement) and 0.1g of LiAlO2 (second lithium supplement). Stir and disperse at 400rpm for 2h. Then spray dry it. Set the atomization pressure to 0.4MPa, the feed temperature to 75℃, and the feed rate to 8mL / min. After drying, the intermediate product is obtained. (3) Take 30g of the intermediate product obtained in step (2) and add it together with 0.5g of Li3V2(PO4)3 into a high-speed mixer and mix at a linear speed of 10m / s for 30min; then carry out the second sintering at 600℃ for 5h in a mixed atmosphere of oxygen and argon (oxygen volume fraction of 20%) to obtain ternary cathode material.

[0041] Example 3 This embodiment provides a method for preparing a ternary cathode material, including the following steps: (1) Take the nickel-cobalt-manganese hydroxide precursor Ni according to the ratio of total moles of nickel, cobalt, and manganese, moles of lithium, and moles of aluminum of 1:1.03:0.002. 0.6 Co 0.2 Mn 0.2 (OH)2, LiOH•H2O and Al2O3 were placed in a high-speed mixer and mixed at 400 rpm for 20 min. The mixture was then placed in an atmosphere furnace and sintered under an oxygen flow. The sintering program was as follows: the temperature was increased from room temperature to 700℃ at a rate of 5℃ / min and held for 2 h; then the temperature was increased to 1050℃ at a rate of 3℃ / min and held for 8 h; finally, the temperature was decreased to room temperature at a rate of 1℃ / min to obtain the core. (2) Take 100g of the kernel obtained in step (1) and disperse it in 500mL of anhydrous ethanol. Add 0.4g of Li3N (first lithium supplement) and 0.1g of Li2CuO2 (second lithium supplement). Stir and disperse at 200rpm for 6h. Then spray dry it. Set the atomization pressure to 0.8MPa, the feed temperature to 55℃, and the feed rate to 12mL / min. After drying, the intermediate product is obtained. (3) Take 50g of the intermediate product obtained in step (2) and add it together with 0.5g of Li3V2(PO4)3 into a high-speed mixer and mix at a linear speed of 20m / s for 10min; then carry out the second sintering at 500℃ for 12h in a mixed atmosphere of oxygen and argon (oxygen volume fraction of 5%) to obtain ternary cathode material.

[0042] Example 4 (1) Take the nickel-cobalt-manganese hydroxide precursor Ni according to the ratio of total moles of nickel, cobalt, and manganese, moles of lithium, and moles of zirconium of 1:1.03:0.001. 0.6 Co 0.2 Mn 0.2 (OH)2, LiOH•H2O and ZrO2 were placed in a high-speed mixer and mixed at 300 rpm for 30 min. The mixture was then placed in an atmosphere furnace and sintered under an oxygen flow. The sintering program was as follows: the temperature was increased from room temperature to 650℃ at a rate of 4℃ / min and held for 3 h; then the temperature was increased to 1020℃ at a rate of 2℃ / min and held for 12 h; finally, the temperature was decreased to room temperature at a rate of 0.5℃ / min to obtain the core. (2) Take 100g of the kernel obtained in step (1) and disperse it in 300mL of anhydrous ethanol. Add 0.8g of Li2S (first lithium supplement) and 0.2g of LiAlO2 (second lithium supplement). Stir and disperse at 300rpm for 4h. Then spray dry it. Set the atomization pressure to 0.6MPa, the feed temperature to 65℃, and the feed rate to 10mL / min. After drying, the intermediate product is obtained. (3) Take 40g of the intermediate product obtained in step (2) and add it together with 0.5g of Li3V2(PO4)3 into a high-speed mixer and mix at a linear speed of 15m / s for 20min; then carry out the second sintering at 650℃ for 8h in a mixed atmosphere of oxygen and argon (oxygen volume fraction of 10%) to obtain ternary cathode material.

[0043] Example 5 (1) Take the nickel-cobalt-manganese hydroxide precursor Ni according to the ratio of the total moles of nickel, cobalt, and manganese, the moles of lithium, and the total moles of titanium and tungsten as 1:1.03:0.0015. 0.6 Co 0.2 Mn 0.2(OH)2, LiOH•H2O, and a mixture of TiO2 and WO3 (where the molar ratio of TiO2 to WO3 is 1:1) were placed in a high-speed mixer and mixed at 300 rpm for 30 min. The mixture was then placed in an atmosphere furnace and subjected to a first sintering under an oxygen flow. The sintering program was as follows: the temperature was increased from room temperature to 650℃ at a rate of 4℃ / min and held for 3 h; then the temperature was increased to 980℃ at a rate of 2℃ / min and held for 12 h; finally, the temperature was decreased to room temperature at a rate of 0.7℃ / min to obtain the core. (2) Take 100g of the kernel obtained in step (1) and disperse it in 300mL of anhydrous ethanol. Add 1.6g of Li2S (first lithium supplement) and 0.4g of LiAlO2 (second lithium supplement). Stir and disperse at 300rpm for 4h. Then spray dry it. Set the atomization pressure to 0.6MPa, the feed temperature to 65℃, and the feed rate to 10mL / min. After drying, the intermediate product is obtained. (3) Take 40g of the intermediate product obtained in step (2) and 0.5g of Nb-doped LiFePO4 (where the mass fraction of Nb is 0.1%) and add them into a high-speed mixer. Mix at a linear speed of 15m / s for 20min. Then, in a mixed atmosphere of oxygen and argon (the volume fraction of oxygen is 10%), keep at 700℃ for 10h for the second sintering to obtain the ternary cathode material.

[0044] Example 6 This embodiment provides a method for preparing a ternary cathode material, which is basically the same as that in Embodiment 1. The only difference is that the sintering procedure in step (1) is replaced by heating to 980°C at 3°C / min and then holding at 980°C for 12 hours and then naturally cooling to room temperature.

[0045] Comparative Example 1 This comparative example provides a method for preparing a ternary cathode material, including the following steps: taking nickel-cobalt-manganese hydroxide precursor Ni according to a ratio of total molar amount of nickel, cobalt, and manganese to molar amount of lithium of 1:1.03. 0.6 Co 0.2 Mn 0.2 After mixing (OH)2 and LiOH•H2O, the mixture is heated to 950℃ at 3℃ / min under an oxygen atmosphere and held for 12h. After natural cooling, it is pulverized and sieved to obtain the ternary cathode material.

[0046] Comparative Example 2 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1. The only difference is that the step of adding Li3V2(PO4)3 in step (3) is omitted, and the intermediate product obtained in step (2) is directly subjected to a second sintering.

[0047] Comparative Example 3 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1, except that step (2) is omitted and the intermediate product in step (3) is replaced with a core of equal mass for subsequent steps.

[0048] Comparative Example 4 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1, except that the addition of Li2S in step (2) is omitted and the amount of LiAlO2 is adjusted to 0.28g.

[0049] Comparative Example 5 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1, except that the addition of LiAlO2 in step (2) is omitted and the amount of Li2S is adjusted to 0.28g.

[0050] Comparative Example 6 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1, except that the ZrO2 in step (1) is replaced with an equimolar amount of La2O3.

[0051] Experimental Example 1 1. The positive electrode materials obtained in each embodiment and comparative example are assembled into coin cells. The preparation method of the coin cells is as follows: (1) Preparation of positive electrode sheet: The positive electrode material, conductive carbon black, and polyvinylidene fluoride obtained in each example and comparative example were mixed in a mass ratio of 8:1:1 and stirred in a vacuum mixer for 8 hours to form a uniform and viscous slurry. The slurry was uniformly coated onto an aluminum foil current collector with a thickness of 15 μm using an automatic coating machine. The coated electrode sheet was then placed in a vacuum oven at 80°C and dried for 10 hours. After that, it was compacted with a roller press and cut into round sheets with a diameter of 12 mm. The mass loading of the positive electrode material on each electrode sheet was precisely controlled to be 2.5 mg / cm². 2 ; (2) Button cell assembly: All battery assembly steps were carried out in a glove box filled with high-purity argon (H2O<0.1ppm, O2<0.1ppm). The negative electrode was a lithium metal sheet, the separator was Celgard 2400, and the electrolyte was 1M LiPF6 (the solvent was ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1). The negative electrode shell, negative electrode sheet (lithium sheet), electrolyte were added, separator was laid, positive electrode sheet was added, electrolyte was added, positive electrode shell was covered, and the sealing machine was used to press and seal the battery to obtain a button cell. The assembled battery was tested after standing for 6 hours.

[0052] 2. Perform performance tests on the button cells prepared above. 1) Charge and discharge test: Under 25℃ conditions, the coin cell is charged at 0.1C and discharged at 0.1C, with a voltage range of 3.0V-4.4V, to obtain the first charge capacity and the first discharge capacity. Then, the first coulombic efficiency is calculated according to (first discharge capacity / first charge capacity) × 100%.

[0053] 2) Cyclic performance test: Under 25℃ conditions, the button cell is first activated at 0.1C and 0.5C for two cycles each (i.e., two charge-discharge cycles), and then cycled at 1.0C for 100 cycles, with a voltage range of 3.0V-4.4V; Capacity retention rate after 100 cycles at 1C = (Discharge specific capacity at 100th cycle at 1C / Discharge specific capacity at 1st cycle at 1C) × 100%.

[0054] 3. X-ray diffraction (XRD) analysis was performed on the ternary cathode materials prepared in each embodiment and comparative example. The specific method is as follows: The ternary cathode materials prepared in each embodiment and comparative example were ground in an agate mortar until the particle size was within the range of 1-10 micrometers. 0.3g of the sample was uniformly filled into the standard sample cell of an X-ray diffractometer, and a glass slide was used to flatten it so that its surface was consistent with the plane of the sample cell. X-ray diffraction was performed using a Cu Kα ray source (λ=0.15406 nm), with the tube voltage set to 40kV, the tube current set to 40mA, the scanning angle 2θ ranging from 10° to 80°, the scanning speed at 2° / min, the step size at 0.02°, and the counting time per step at 2 seconds. The obtained XRD data were imported into analysis software such as GSAS, and peak shape fitting was performed after background subtraction. The interplanar spacing d of the (003) and (104) crystal planes was calculated using the Bragg equation 2d sinθ=nλ. Then, it was substituted into the lattice stress calculation formula σ=E·(d-d0) / d0, where E is the elastic modulus of the material, d is the measured interplanar spacing of the test sample, and d0 is the interplanar spacing of the stress-free standard sample (corresponding to the standard value of a ternary cathode material of the same composition after full annealing). This yielded σ. 003 Lattice stress and σ 104 Lattice stress.

[0055] 4. Test Results Table 1 Electrochemical performance test results

[0056] Table 2 X-ray diffraction test results

[0057] As shown in Tables 1 and 2, in terms of lattice stress control, the ternary cathode materials prepared in Examples 1-6 of this invention, due to the doping of specific elements, have their (003) and (104) crystal plane lattice stresses controlled within the optimized range, and the lattice stress matching degree is significantly improved. In contrast, Comparative Examples 1 and 6, due to the lack of doping or the doping of other elements, have lattice stress mismatches on the crystal planes, and the structural stability of the materials is not as good as that of the Examples. In terms of electrochemical performance, the first discharge capacity, first coulombic efficiency, and capacity retention rate of Examples 1-6 under high voltage conditions are significantly better than those of Comparative Examples 1-6. This indicates that the present invention effectively improves the cycling stability of the cathode material under high voltage through the synergistic effect between the inner layer dual lithium replenishment and the outer layer fast ion conductor conduction.

[0058] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a ternary cathode material, characterized in that, Includes the following steps: Step S1: The ternary cathode material precursor, lithium source and M element source are first mixed, and then first sintered to obtain the core; the M element includes at least one of Zr, Al, Ti, Mg and W; Step S2: The kernel is dispersed in a solvent and mixed with the first lithium supplement and the second lithium supplement to obtain an intermediate product; The first lithium replenishing agent includes Li2S and / or Li3N; the second lithium replenishing agent includes lithium and a first metal element; the first metal element includes Al and / or Cu; Step S3: Mix the intermediate product and the fast ion conductor precursor and perform a second sintering to obtain the ternary cathode material.

2. The method for preparing the ternary cathode material according to claim 1, characterized in that, In step S1, the chemical formula of the ternary cathode material precursor is Ni. x Co y Mn 1-x-y (OH)₂, where 0.5≤x≤0.8, 0.1≤y≤0.3, 0 <x+y<1; And / or, the lithium source includes lithium hydroxide and / or lithium carbonate; And / or, the source of element M includes at least one of ZrO2, Al2O3, TiO2, MgO, and WO3.

3. The method for preparing the ternary cathode material according to claim 1 or 2, characterized in that, In step S1, the ratio of the total number of moles of nickel, cobalt, and manganese in the ternary cathode material to the number of moles of M element in the M element source is 1:0.0005-0.

02. And / or, the ratio of the total molar number of nickel, cobalt, and manganese elements in the ternary cathode material precursor to the molar number of lithium elements in the lithium source is 1:1.01-1.05; And / or, the first mixing speed is 200-400 rpm and the time is 20-40 min; And / or, the first sintering operation includes heating to 950-1050°C at a rate of 1-3°C / min and holding for 8-15 hours in an oxygen atmosphere; or, heating from room temperature to 600-700°C at a rate of 2-5°C / min and holding for 2-4 hours in an oxygen atmosphere, and then heating to 950-1050°C at a rate of 1-3°C / min and holding for 8-15 hours. And / or, after the first sintering, the process further includes a step of cooling to room temperature at a rate of 0.5-1 °C / min.

4. The method for preparing the ternary cathode material according to claim 1, characterized in that, In step S2, the solvent includes ethanol and / or N-methylpyrrolidone; And / or, the mass ratio of the core to the volume ratio of the solvent is 1g:3-5mL; And / or, the second lithium supplement includes LiAlO2 or Li2CuO2; And / or, the mass ratio of the first lithium replenishing agent to the second lithium replenishing agent is 2-5:1; And / or, the mass ratio of the core to the total mass of the first and second lithium supplementers is 1:0.002-0.02; And / or, the reaction is carried out at a speed of 200-400 rpm for a time of 2-6 h; And / or, the reaction may be followed by a spray drying or vacuum drying step; Optionally, the atomization pressure of the spray dryer is 0.4-0.8 MPa, the feed temperature is 55-75℃, and the feed rate is 8-12 mL / min.

5. The method for preparing the ternary cathode material according to claim 1, characterized in that, In step S3, the chemical formula of the fast ion conductor precursor includes Li α1 N β1 (PO4) γ1 and / or Li α2 N β2 (SiO3) γ2 Wherein, N includes at least one of Fe, V, Mn, and Ti, and α1, β1, γ1, α2, β2, and γ2 are each positive integers that satisfy valence balance; And / or, the mass ratio of the intermediate product to the fast ion conductor precursor is 60-100:1; And / or, the linear velocity of the mixture is 10-20 m / s, and the time is 10-30 min; And / or, the second sintering temperature is 400-700℃, and the time is 5-12h; And / or, the atmosphere for the second sintering is an oxygen-containing atmosphere; preferably, it is a mixed atmosphere containing inert gas and oxygen.

6. The method for preparing the ternary cathode material according to claim 5, characterized in that, The fast ion conductor precursor is also doped with Nb. And / or, the oxygen-containing atmosphere is a mixed atmosphere containing inert gas and oxygen; And / or, the oxygen volume fraction of the oxygen-containing atmosphere is 5%-20%.

7. The ternary cathode material prepared by the method of any one of claims 1-6.

8. A positive electrode sheet, characterized in that, include: Positive current collector, and A positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprising the ternary positive electrode material as described in claim 7.

9. A secondary battery, characterized in that, Includes the positive electrode sheet as described in claim 8.

10. An electrical device, characterized in that, Includes the secondary battery as described in claim 9.

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