Preparation method of solid electrolyte homogeneous-phase coated positive electrode material

Abstract

The invention relates to a preparation method of a solid electrolyte homogeneous-phase coated positive electrode material, and belongs to the technical field of lithium battery positive electrode materials, in the grinding process, a mechanical ball milling medium can peel off an oxide layer on the surface of a raw material, and the problem that the surface activity of the material is reduced in the storage process after independent ore grinding is effectively avoided. The microwave heating can realize uniform heating in the whole reaction system, so that the reaction uniformity is ensured, and local overheating or non-uniform temperature is avoided; secondly, the raw materials are in multi-surface high-frequency contact under high-speed ball milling, the reaction rate and efficiency can be remarkably improved at high temperature, in addition, the dislocation density can be increased through high-strength mechanical grinding, so that the activation energy of chemical reaction is reduced, the activation energy and excitation provided by heat energy supplement each other to jointly promote reduction of a reaction energy barrier, and the reaction efficiency is improved. And the interface bonding strength and uniformity of the coating layer and the precursor are obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery cathode material technology, and relates to a method for preparing a solid electrolyte homogeneous coated cathode material. Background Technology

[0002] Constructing a uniform coating layer on the surface of lithium-ion battery cathode materials is an effective means to solve side reactions and improve cycle life. The core technology lies in how to form a stable and uniformly mixed coating layer on the surface of the cathode material precursor. The conventional liquid-phase method involves dissolving the coating source in water or an organic solvent and mixing it uniformly, then adding the precursor and stirring and drying to obtain the desired ternary cathode precursor material. However, during the stirring process, the material and solvent are prone to react with moisture and air in the air, and the drying process is relatively long. The mixed material is also prone to redeposition, which affects the formation of a uniform coating material on the precursor surface and further affects the electrochemical performance of the cathode coating material.

[0003] Chinese invention patent CN119542393B discloses a lanthanide perovskite oxide-coated high-nickel ternary cathode material and its preparation method. The preparation method includes the following steps: 1) Adding lanthanum, calcium, and cobalt sources to a solvent and ultrasonically dispersing them to obtain a mixed solution of metal ions; adding a complexing agent to the solvent and ultrasonically dispersing it to obtain a complexing agent solution; 2) Adding the complexing agent solution obtained in step 1) dropwise to the mixed solution of metal ions obtained in step 1), or adding the mixed solution of metal ions obtained in step 1) dropwise to the complexing agent solution obtained in step 1), performing a single stirring reaction, heating, performing a second stirring reaction, drying, ball milling, sintering under an oxidizing atmosphere, and cooling to room temperature to obtain a lanthanide perovskite oxide; by selecting a suitable La... z Ca 1-z CoO3 coating enhances the interfacial and structural stability of the material, effectively suppressing electrolyte erosion, phase transitions, and lattice oxygen release. It also reduces the dissolution of transition metals in the active material, decreases electrode polarization and side reactions during cycling, and reduces gas generation. Consequently, it significantly improves the cycling performance, rate performance, reversible capacity, and initial coulombic efficiency of high-nickel ternary cathode materials, exhibiting excellent electrochemical performance.

[0004] Chinese invention patent CN114853089B discloses a method for preparing magnesium borate-coated high-nickel ternary cathode materials. The specific steps include: first, thoroughly mixing a lithium source and a ternary precursor; sintering the mixture at high temperature in an oxygen atmosphere; then cooling to room temperature; and finally pulverizing and sieving the sintered product to obtain a primary sintered powder. Next, uniformly mixing this sintered powder with magnesium borate; coating and sintering the mixture at high temperature; and finally cooling to room temperature to obtain the final magnesium borate-coated high-nickel ternary cathode material. The advantage of this method is that it can significantly reduce the residual alkali content in the material, thereby reducing the powder resistance and improving its conductivity. Furthermore, the magnesium borate coating can effectively improve the cycle stability and rate performance of the high-nickel ternary cathode material, thus extending the battery's lifespan and enhancing its fast charge / discharge capability.

[0005] However, during the coating process, the cathode precursor and coating material are prone to react with oxygen and moisture in the environment to generate high-valence oxides of transition metals such as Ni2O3, MnO2, and Fe2O3. These oxidation products are unevenly attached to the surface of the raw materials in a localized agglomerate state, which will prevent the effective contact between the coating material and the precursor, increase the mass transfer resistance of the reaction, and reduce the electrochemical reaction efficiency of the battery charge and discharge. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a homogeneous coating of a solid electrolyte cathode material. The method involves vacuum drying under a protective atmosphere followed by high-temperature ball milling to achieve uniform mixing of the raw materials, effectively removing oxidation products and solving the problems of low reaction rate, poor efficiency, and high activation energy of the chemical reaction.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing a homogeneous solid electrolyte coated cathode material includes the following steps: Step 1: Weigh the precursor and coating material according to the stoichiometric ratio, and perform vacuum drying to obtain the pretreated material.

[0008] Step 2: Mix the pretreated materials evenly and transfer them to a microwave high-temperature ball mill. Keep the mixture at 150°C for 20 minutes under a protective atmosphere. Heat the ball mill jar to the first stage temperature and perform preliminary ball milling. Then heat it to the second stage temperature and perform the second ball milling. Transfer the mixture to a pressure relief container and depressurize it to atmospheric pressure to obtain a solid electrolyte homogeneous coated cathode material.

[0009] Furthermore, the precursor is one or more of the following: nickel-manganese-based or nickel-iron-based binary precursor, nickel-cobalt-manganese hydroxide or nickel-cobalt-aluminum hydroxide ternary precursor, cobalt tetroxide, manganese-iron phosphate, and manganese dioxide.

[0010] Furthermore, the coating material is one or more of oxide solid electrolytes, sulfide solid electrolytes, polymer solid electrolytes, and borate solid electrolytes.

[0011] Furthermore, the protective atmosphere is one or more of argon, nitrogen, helium, argon hydrogen, and carbon dioxide.

[0012] Furthermore, the vacuum drying temperature is 100-120℃, and the time is 6-12 hours.

[0013] Furthermore, the mass ratio of the precursor to the coating material is 100:0.7-3.0.

[0014] Furthermore, the temperature in the first stage is 180-200℃, and the initial ball milling time is 2 hours.

[0015] Furthermore, the second stage temperature is 650-850℃, and the second ball milling time is 8-10 hours.

[0016] Furthermore, the pretreatment materials also include phase dopant Al(NO3)3·9H2O and coating layer co-dopant Mg(NO3)2·6H2O.

[0017] Furthermore, the mass ratio of the precursor, coating material, phase dopant, and coating co-dopant is 100:0.7-3.0:0.1-0.2:0.04-0.06.

[0018] The beneficial effects of this invention are: 1. In the grinding process of this invention, the mechanical ball milling media can peel off the oxide layer on the surface of the raw material, effectively avoiding the problem of decreased surface activity of the material during storage after individual grinding. Microwave heating can achieve uniform heating throughout the entire reaction system, ensuring the uniformity of the reaction and avoiding local overheating or uneven temperature. Secondly, the high-frequency contact of multiple surfaces of the raw material under high-speed ball milling can significantly improve the reaction rate and efficiency at high temperatures. In addition, high-intensity mechanical grinding can increase dislocation density, thereby reducing the activation energy of the chemical reaction. This, combined with the excitation provided by thermal energy, promotes the reduction of the reaction energy barrier and significantly improves the interfacial bonding strength and uniformity between the coating layer and the precursor.

[0019] 2. This invention introduces a dual-doping system by combining the phase dopant Al(NO3)3·9H2O and the co-doperant Mg(NO3)2·6H2O in the coating layer. This achieves synergistic modification of the bulk phase and interface of the cathode material. Aluminum ions can embed into the precursor lattice, suppressing the mixing of nickel and lithium ions, reducing the release of lattice oxygen and lattice distortion during cycling, and improving the structural stability of the cathode material. Magnesium ions can replace some metal ions in the coating layer, increasing lithium ion vacancies, improving the ionic conductivity of the oxide solid electrolyte coating layer, and reducing the interfacial charge transfer resistance. The synergistic effect of the dual-doping system and the homogeneous coating layer significantly improves the lithium-ion diffusion coefficient and electrochemical reaction reversibility of the cathode material, effectively improving the rate performance and cycle stability of the material.

[0020] 3. The preparation process of this invention has strong compatibility. The precursor can be adapted to various cathode material systems such as nickel-manganese-based / nickel-iron-based binary precursors and nickel-cobalt-manganese / nickel-cobalt-aluminum ternary precursors. The coating material can also be flexibly selected from solid electrolytes such as oxides, sulfides, polymers, and borates. Moreover, the material ratio is set within a reasonable range to adapt to the material performance requirements of different application scenarios. The coating reaction is directly completed through the synergistic effect of microwave and ball milling, which reduces energy consumption and simplifies the steps. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the preparation method of the solid electrolyte homogeneous coated cathode material in Embodiment 1 of the present invention; Figure 2 This is a scanning electron microscope image of the homogeneous solid electrolyte-coated cathode material in Example 1 of the present invention; Figure 3 This is the XPS electron spectrum of the homogeneous coating of the solid electrolyte with positive electrode material after ball milling in Example 1 of the present invention. Detailed Implementation

[0022] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0023] Example 1: This example provides a method for preparing a homogeneous solid electrolyte coated cathode material, using a NASICON-type oxide solid electrolyte Li... 1.3 Ga 0.3 Ti 1.7 (PO4)3-coated precursor Ni 0.83 Co 0.11 Mn 0.06 Taking (OH)2 as an example, the steps are as follows: S1: Weigh 10g of precursor Ni into a glove box filled with argon atmosphere (water and oxygen content less than or equal to 0.1ppm).0.8 Co 0.1 Mn 0.1 (OH)2, along with 0.15g of LiNO3, Ga(NO3)3, (NH4)H2PO4, Ti(C4H9O)4 coating material, 0.02g of phase dopant Al(NO3)3·9H2O, and 0.005g of coating co-doperant Mg(NO3)2·6H2O, were transferred to a vacuum drying oven and dried at 100℃ for 12h to obtain the pretreated material.

[0024] S2: Mix the pretreated materials evenly and transfer them to a sealable microwave high-temperature ball mill. Add zirconia balls with a particle size of 0.5 mm at a ball-to-material ratio of 15:1. Inject argon gas into the ball mill jar at a flow rate of 100 mL / min until the pressure inside the jar is 0.12 MPa. Maintain the temperature at 150°C for 20 min.

[0025] S3: Microwave heat the grinding jar to the first stage temperature of 200℃ and maintain the temperature. At the same time, start the ball mill for preliminary ball milling for 2 hours at a speed of 400 r / min. Heat the grinding jar to the second stage temperature of 750℃ and maintain it. Continue to start the ball mill for the second step of ball milling for 8 hours at a speed of 700 r / min. Transfer the ball-milled material to a pressure relief container and slowly depressurize it to atmospheric pressure at a rate of ≤0.01 MPa. Take out the material to obtain a solid electrolyte homogeneous coated positive electrode material.

[0026] The solid electrolyte homogeneous coated cathode material prepared in this embodiment, after calcination, produces an X-ray photoelectron spectroscopy (XPS) image as shown below. Figure 2 As shown.

[0027] Example 2: This example provides a method for preparing a homogeneous solid electrolyte coated cathode material, using a NASICON-type oxide solid electrolyte Li... 1.3 Ga 0.3 Ti 1.7 (PO4)3-coated Ni 0.90 Co 0.05 Mn 0.05 Taking (OH)2 as an example, the steps are as follows: S1: Weigh 10g of precursor Ni into a glove box filled with argon atmosphere (water and oxygen content less than or equal to 0.1ppm). 0.90 Co 0.05 Mn 0.05(OH)2, along with 0.1g of LiNO3, Ga(NO3)3, (NH4)H2PO4, Ti(C4H9O)4 coating material, 0.015g of phase dopant Al(NO3)3·9H2O, and 0.005g of coating co-doperant Mg(NO3)2·6H2O, were transferred to a vacuum drying oven and dried at 100℃ for 8 hours to obtain the pretreated material.

[0028] S2: Mix the pretreated materials evenly and transfer them to a sealable microwave high-temperature ball mill. Add zirconia balls with a particle size of 0.5 mm at a ball-to-material ratio of 15:1. Inject argon gas into the ball mill jar at a flow rate of 100 mL / min until the pressure inside the jar is 0.12 MPa. Maintain the temperature at 150°C for 20 min.

[0029] S3: Microwave heat the grinding jar to the first stage temperature of 200℃ and maintain the temperature. At the same time, start the ball mill for preliminary ball milling for 2 hours at a speed of 400 r / min. Heat the grinding jar to the second stage temperature of 750℃ and maintain it. Continue to start the ball mill for the second step of ball milling for 8 hours at a speed of 700 r / min. Transfer the ball-milled material to a pressure relief container and slowly depressurize it to atmospheric pressure at a rate of ≤0.01 MPa. Take out the material to obtain a solid electrolyte homogeneous coated positive electrode material.

[0030] Example 3: This example provides a method for preparing a homogeneous solid electrolyte coated cathode material, using a NASICON-type oxide solid electrolyte Li... 1.3 Ga 0.3 Ti 1.7 (PO4)3-coated precursor Ni 0.90 Co 0.05 Mn 0.05 Taking (OH)2 as an example, the steps are as follows: S1: Weigh 10g of precursor Ni into a glove box filled with argon atmosphere (water and oxygen content less than or equal to 0.1ppm). 0.90 Co 0.05 Mn 0.05 (OH)2, along with 0.15g of LiNO3, Ga(NO3)3, (NH4)H2PO4, Ti(C4H9O)4 coating material, 0.01g of phase dopant Al(NO3)3·9H2O, and 0.004g of coating co-doperant Mg(NO3)2·6H2O, were transferred to a vacuum drying oven and dried at 100℃ for 8 hours to obtain the pretreated material.

[0031] S2: Mix the pretreated materials evenly and transfer them to a sealable microwave high-temperature ball mill. Add zirconia balls with a particle size of 0.5 mm at a ball-to-material ratio of 15:1. Inject argon gas into the ball mill jar at a flow rate of 100 mL / min until the pressure inside the jar is 0.12 MPa. Maintain the temperature at 150°C for 20 min.

[0032] S3: Microwave heat the grinding jar to the first stage temperature of 200℃ and maintain the temperature. At the same time, start the ball mill for preliminary ball milling for 2 hours at a speed of 400 r / min. Heat the grinding jar to the second stage temperature of 750℃ and maintain it. Continue to start the ball mill for the second step of ball milling for 8 hours at a speed of 700 r / min. Transfer the ball-milled material to a pressure relief container and slowly depressurize it to atmospheric pressure at a rate of ≤0.01 MPa. Take out the material to obtain a solid electrolyte homogeneous coated positive electrode material.

[0033] Example 4: This example provides a method for preparing a homogeneous solid electrolyte coated cathode material, using a NASICON-type oxide solid electrolyte Li7La3Zr2O. 12 Coated precursor Ni 0.90 Co 0.05 Mn 0.05 Taking (OH)2 as an example, the steps are as follows: S1: Weigh 10g of precursor Ni into a glove box filled with argon atmosphere (water and oxygen content less than or equal to 0.1ppm). 0.90 Co 0.05 Mn 0.05 The (OH)2 and 0.15g of LiNO3, La(NO3)3·6H2O and ZrO(NO3)2 coating materials were transferred to a vacuum drying oven and dried at 120℃ for 8h to obtain the pretreated material.

[0034] S2: Mix the pretreated materials evenly and transfer them to a sealable microwave high-temperature ball mill. Add zirconia balls with a particle size of 0.5 mm at a ball-to-material ratio of 15:1. Inject argon gas into the ball mill jar at a flow rate of 100 mL / min until the pressure inside the jar is 0.12 MPa. Maintain the temperature at 150°C for 20 min.

[0035] S3: Microwave heat the grinding jar to the first stage temperature of 180℃ and maintain the temperature. At the same time, start the ball mill for preliminary ball milling for 2 hours at a speed of 400 r / min. Heat the grinding jar to the second stage temperature of 820℃ and maintain the temperature. Continue to start the ball mill for the second step of ball milling for 8 hours at a speed of 700 r / min. Transfer the ball-milled material to a pressure relief container and slowly depressurize it to atmospheric pressure at a rate of ≤0.01 MPa. Take out the material to obtain a solid electrolyte homogeneous coated positive electrode material.

[0036] Example 5: This example provides a method for preparing a homogeneous solid electrolyte coated cathode material, using a NASICON-type oxide solid electrolyte Li... 1.3 Ga 0.3 Ti 1.7 (PO4)3-coated precursor Ni 0.83 Co 0.11 Mn 0.06 Taking (OH)2 as an example, the steps are as follows: S1: Weigh 10g of precursor Ni into a glove box filled with argon atmosphere (water and oxygen content less than or equal to 0.1ppm). 0.8 Co 0.1 Mn 0.1 (OH)2, along with 0.3g of LiNO3, Ga(NO3)3, (NH4)H2PO4, Ti(C4H9O)4 coating material, 0.01g of phase dopant Al(NO3)3·9H2O, and 0.006g of coating co-doperant Mg(NO3)2·6H2O, were transferred to a vacuum drying oven and dried at 120℃ for 6 hours to obtain the pretreated material.

[0037] S2: Mix the pretreated materials evenly and transfer them to a sealable microwave high-temperature ball mill. Add zirconia balls with a particle size of 0.5 mm at a ball-to-material ratio of 15:1. Inject argon gas into the ball mill jar at a flow rate of 100 mL / min until the pressure inside the jar is 0.12 MPa. Maintain the temperature at 150°C for 20 min.

[0038] S3: Microwave heat the grinding jar to the first stage temperature of 200℃ and maintain the temperature. At the same time, start the ball mill for preliminary ball milling for 2 hours at a speed of 400 r / min. Heat the grinding jar to the second stage temperature of 850℃ and maintain the temperature. Continue to start the ball mill for the second step of ball milling for 8 hours at a speed of 700 r / min. Transfer the ball-milled material to a pressure relief container and slowly depressurize it to atmospheric pressure at a rate of ≤0.01 MPa. Take out the material to obtain a solid electrolyte homogeneous coated positive electrode material.

[0039] Example 6: This example provides a method for preparing a homogeneous solid electrolyte coated cathode material, using a NASICON-type oxide solid electrolyte Li7La3Zr2O. 12 Coated precursor Ni 0.83 Co 0.11 Mn 0.05 Taking (OH)2 as an example, the steps are as follows: S1: Weigh 10g of precursor Ni into a glove box filled with argon atmosphere (water and oxygen content less than or equal to 0.1ppm). 0.8 Co 0.1 Mn 0.1The (OH)2 and 0.15g of LiNO3, La(NO3)3·6H2O and ZrO(NO3)2 coating materials were transferred to a vacuum drying oven and dried at 120℃ for 6h to obtain the pretreated material.

[0040] S2: Mix the pretreated materials evenly and transfer them to a sealable microwave high-temperature ball mill. Add zirconia balls with a particle size of 0.5 mm at a ball-to-material ratio of 15:1. Inject argon gas into the ball mill jar at a flow rate of 100 mL / min until the pressure inside the jar is 0.12 MPa. Maintain the temperature at 150°C for 20 min.

[0041] S3: Microwave heat the grinding jar to the first stage temperature of 200℃ and maintain the temperature. At the same time, start the ball mill for preliminary ball milling for 2 hours at a speed of 400 r / min. Heat the grinding jar to the second stage temperature of 650℃ and maintain it. Continue to start the ball mill for the second step of ball milling for 10 hours at a speed of 700 r / min. Transfer the ball-milled material to a pressure relief container and slowly depressurize it to atmospheric pressure at a rate of ≤0.01 MPa. Take out the material to obtain a solid electrolyte homogeneous coated cathode material.

[0042] Example 7: This example provides a method for preparing a homogeneous solid electrolyte coated cathode material, using a NASICON-type oxide solid electrolyte Li7La3Zr2O. 12 Coated precursor Ni 0.90 Co 0.05 Mn 0.05 Taking (OH)2 as an example, the steps are as follows: S1: Weigh 10g of precursor Ni into a glove box filled with argon atmosphere (water and oxygen content less than or equal to 0.1ppm). 0.90 Co 0.05 Mn 0.05 The (OH)2 and 0.07g of LiNO3, La(NO3)3·6H2O and ZrO(NO3)2 coating materials were transferred to a vacuum drying oven and dried at 120℃ for 6h to obtain the pretreated material.

[0043] S2: Mix the pretreated materials evenly and transfer them to a sealable microwave high-temperature ball mill. Add zirconia balls with a particle size of 0.5 mm at a ball-to-material ratio of 15:1. Inject argon gas into the ball mill jar at a flow rate of 100 mL / min until the pressure inside the jar is 0.12 MPa. Maintain the temperature at 150°C for 20 min.

[0044] S3: Microwave heat the grinding jar to the first stage temperature of 200℃ and maintain the temperature. At the same time, start the ball mill for preliminary ball milling for 2 hours at a speed of 400 r / min. Heat the grinding jar to the second stage temperature of 750℃ and maintain it. Continue to start the ball mill for the second step of ball milling for 8 hours at a speed of 700 r / min. Transfer the ball-milled material to a pressure relief container and slowly depressurize it to atmospheric pressure at a rate of ≤0.01 MPa. Take out the material to obtain a solid electrolyte homogeneous coated positive electrode material.

[0045] Comparative Example 1: This comparative example provides a method for preparing a homogeneous solid electrolyte coated cathode material, comprising the following steps: S1: Add 0.15g of LiNO3, Ga(NO3)3, (NH4)H2PO4, Ti(C4H9O)4 coating material and 20mL of N-methylpyrrolidone (NMP) to the reaction vessel and stir magnetically for 30min until completely dissolved to obtain the coating solution.

[0046] S2: Add 10g of precursor Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 and coating solution are mixed and stirred at 30°C for 2 hours to fully disperse the precursor and adsorb the coating solute. The mixture is then dried at 80°C for 12 hours to remove the solvent and obtain the precursor powder.

[0047] S3: The precursor powder was placed in a tube furnace and heated to 750°C at a heating rate of 5°C / min under an argon atmosphere. It was then held at that temperature for 8 hours and sintered. After cooling to room temperature, it was ground and passed through a 200-mesh sieve to obtain a solid electrolyte homogeneous coated cathode material.

[0048] Batteries were fabricated using solid electrolyte homogeneous coating of cathode materials prepared in Examples 1-7 and Comparative Example 1, and their performance was tested. Solid electrolyte homogeneous coating of positive electrode material, conductive agent (Super P), and PVDF were weighed at a mass ratio of 8:1:1, ground and mixed evenly. N-methylpyrrolidone (NMP) was then added as a dispersant and stirred until the slurry reached a viscous state. The prepared positive electrode slurry was uniformly coated onto aluminum foil and placed in a vacuum drying oven at 80°C for 12 hours to ensure complete evaporation of NMP. Afterward, the dried electrode sheet was rolled to achieve the designed thickness and ensure good contact between the active material and the current collector. Finally, the electrode sheet was punched into 12mm circular positive electrode sheets for subsequent battery assembly.

[0049] The prepared electrode was used as the positive electrode, and the lithium metal sheet was used as the negative electrode. A 1.0 mol·L⁻¹ solution was applied. -1LiPF6-EC+DEC (volume ratio 1:1) high-voltage electrolyte. CR2032 button cells were assembled in an argon glove box, sealed, and left to stand for 12 hours before electrochemical testing.

[0050] Cyclic voltammetry (CV) is an important technique for characterizing electrochemical reaction kinetics and electrode processes. By applying a scanning periodic voltage to the electrode, CV can plot the relationship between current and voltage, thus obtaining detailed information about the electrochemical performance of the material. The CV test voltage range is 2.7–4.3 V, and the scan rate is 0.1 mV·s. -1 .

[0051] Constant temperature and constant voltage charge-discharge test: within a voltage range of 2.7-4.3V (vs. Li + Constant current and constant voltage model charge-discharge tests were conducted on the new Wilton multichannel battery test system (Li). All electrochemical tests were performed at room temperature.

[0052] Intermittent galvanostatic titration (GITT): A constant current is applied at set time intervals and voltage changes are recorded to measure battery capacity loss and electrochemical impedance.

[0053] Alternating current impedance spectroscopy (EIS): The frequency range for EIS testing is 10... -2 -10 5 Hz, amplitude 0.1mV·s -1 .

[0054] The test results are shown in the table below: Table 1 Performance Test Overview As shown in Table 1, the rate performance of Examples 1-7 is better than that of Comparative Example 1. This may be because the dry coating process of vacuum drying and microwave high-temperature segmented ball milling is completed in an argon protective atmosphere, which effectively avoids the oxidation reaction of the precursor when it comes into contact with air and moisture, and reduces the blockage of the lithium-ion transport channel by oxidation products. At the same time, the synergistic effect of microwave uniform heating combined with mechanical ball milling makes the oxide solid electrolyte coating layer uniformly adhere to the surface of the precursor, forming a continuous and stable lithium-ion transport interface, reducing the charge transfer resistance. Meanwhile, the doping amounts of phase dopant Al(NO3)3·9H2O and coating layer co-dopant Mg(NO3)2·6H2O are exactly matched to the dual requirements of lattice stability and ion conduction. In contrast, Comparative Example 1, which uses traditional liquid phase coating and high-temperature sintering process, is prone to uneven coating layer deposition and local agglomeration, which blocks the lithium-ion diffusion channel and significantly reduces the ion transport efficiency at high rates.

[0055] As shown in Table 1, the cycling performance of Examples 1-7 is better than that of Comparative Example 1. This may be because the microwave high-temperature segmented ball milling process is completed under an inert atmosphere, which effectively suppresses the oxidation of the precursor surface and the dissolution of transition metals. In addition, the uniform oxide solid electrolyte coating layer forms a physical barrier, reducing the interfacial side reactions between the electrolyte and the cathode material, reducing the release of lattice oxygen during cycling, and the dual doping of aluminum and magnesium ions can improve structural stability, suppress lattice distortion and coating layer shedding during cycling, resulting in higher cycling efficiency.

[0056] The peak potential difference in Examples 1-7 is smaller than that in Comparative Example 1, possibly because the dry microwave ball milling process ensures that the coating layer uniformly covers the surface of the precursor, and no oxidation products are generated throughout the process, which reduces the polarization of the electrochemical reaction. Uniform microwave heating avoids the reaction kinetic differences caused by local overheating, while mechanical ball milling reduces the activation energy of the reaction, making the redox reaction more reversible. Aluminum ion doping suppresses lattice distortion and reduces the resistance to ion transport, while magnesium ion doping increases the ionic conductivity of the coating layer and accelerates the interfacial charge transfer. The two work together to reduce the polarization of the redox reaction.

[0057] The lithium-ion diffusion coefficients of Examples 1-7 are higher than those of Comparative Example 1, possibly because the phase dopant and the co-dopant of the coating layer jointly expand the lattice spacing of the material, thereby widening the internal channels for lithium-ion migration. At the same time, the microwave high-temperature ball milling process enables the homogeneous adhesion of the oxide solid electrolyte coating layer on the precursor surface, forming a continuous and uninterrupted lithium-ion transport interface. In addition, the absence of oxidation products blocking the channels under the inert atmosphere enhances the lithium-ion migration rate.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a solid electrolyte homogeneously coated cathode material, characterized in that, Includes the following steps: Step 1: Weigh the precursor and coating material according to the stoichiometric ratio, and vacuum dry them to obtain the pretreated material; Step 2: Mix the pretreated materials evenly and transfer them to a microwave high-temperature ball mill. Keep the mixture at 150°C for 20 minutes under a protective atmosphere. Heat the ball mill jar to the first stage temperature and perform preliminary ball milling. Then heat it to the second stage temperature and perform the second ball milling. Transfer the mixture to a pressure relief container and depressurize it to atmospheric pressure to obtain a solid electrolyte homogeneous coated cathode material.

2. The method for preparing a homogeneous solid electrolyte coated cathode material according to claim 1, characterized in that, The precursor is one or more of the following: nickel-manganese-based or nickel-iron-based binary precursor, nickel-cobalt-manganese hydroxide or nickel-cobalt-aluminum hydroxide ternary precursor, cobalt tetroxide, manganese-iron phosphate, and manganese dioxide.

3. The method for preparing a homogeneous coated positive electrode material for a solid electrolyte according to claim 1, characterized in that, The coating material is one or more of oxide solid electrolytes, sulfide solid electrolytes, polymer solid electrolytes, and borate solid electrolytes.

4. The method for preparing a homogeneous coated positive electrode material for a solid electrolyte according to claim 1, characterized in that, The protective atmosphere is one or more of argon, nitrogen, helium, argon hydrogen, and carbon dioxide.

5. The method for preparing a homogeneous coated positive electrode material for a solid electrolyte according to claim 1, characterized in that, The vacuum drying temperature in step one is 100-120℃, and the time is 6-12h.

6. The method for preparing a homogeneous coated positive electrode material for a solid electrolyte according to claim 1, characterized in that, The mass ratio of the precursor to the coating material is 100:0.7-3.

0.

7. The method for preparing a homogeneous coated positive electrode material for a solid electrolyte according to claim 1, characterized in that, In step two, the temperature of the first stage is 180-200℃, and the initial ball milling time is 2 hours.

8. The method for preparing a homogeneous solid electrolyte coated cathode material according to claim 1, characterized in that, In step two, the temperature of the second stage is 650-850℃, and the ball milling time is 8-10 hours.

9. The method for preparing a homogeneous coated positive electrode material for a solid electrolyte according to claim 1, characterized in that, The pretreatment materials mentioned in step one also include phase dopant Al(NO3)3·9H2O and coating layer co-dopant Mg(NO3)2·6H2O.

10. The method for preparing a homogeneous coated positive electrode material for a solid electrolyte according to claim 9, characterized in that, The mass ratio of the precursor, coating material, phase dopant and coating co-dopant in step one is 100:0.7-3.0:0.1-0.2:0.04-0.06.

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