High-voltage positive electrode material for lithium ion battery based on iron molybdate sol coating and preparation method and application thereof

Abstract

This invention discloses a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating, its preparation method, and its application, belonging to the field of lithium-ion battery technology. It aims to solve the problems of poor structural stability, charge / discharge capacity, and cycle performance of cathode materials under high-voltage conditions. The preparation method provided by this invention involves dissolving an iron source in water, adding citric acid to form a complex solution, and then adding a molybdenum source to obtain a uniform iron molybdate sol. The lithium-ion battery cathode material is dispersed in a dispersion medium, and the sol is added at a specific coating ratio and stirred to form a composite. Subsequent separation, drying, and calcination treatments yield the target material. This invention uses a sol coating method to achieve uniform and dense coating. Iron molybdate exhibits no electrochemical reaction in the 3.2-5V high-voltage range and possesses fast lithium conductivity, which can suppress structural distortion and side reactions of the cathode material, significantly improving its discharge specific capacity, first-cycle coulombic efficiency, and long-term cycle stability, making it suitable for high-voltage lithium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used as energy storage devices due to their advantages such as high energy density, long cycle life, and relatively low self-discharge rate. Driven by the rapid development of the electric vehicle industry, the research and development of high-energy-density lithium-ion batteries has become a key focus for the industry.

[0003] However, under high-voltage conditions, traditional mainstream cathode materials all face severe performance degradation, hindering further breakthroughs in energy density. Lithium cobalt oxide (LCO) possesses excellent theoretical volumetric energy density and is widely used in portable devices. However, due to the limitation of cutoff voltage, the capacity of commercially available LCO is only 150-180 mAh / g, leaving considerable potential for improvement to reach its theoretical specific capacity (274 mAh / g). When the charging voltage of LCO exceeds 4.55V, LCO undergoes a harmful phase transition from the O3 phase to the O1-O3 and H1-3 phases, accompanied by interlayer slip and the collapse of the O3 lattice structure. Simultaneously, surface lattice oxygen is easily oxidized to peroxide O. - And escaped, Co 3+ Oxidized to Co 4+ It also catalyzes electrolyte decomposition, leading to continuous deterioration of the material structure and interface, accelerating battery failure. Spinel-phase lithium manganese oxide (LMO) and lithium nickel manganese oxide (LNMO) also benefit from high operating voltage, high safety, low cost, and three-dimensional Li... + Both have attracted much attention due to their diffusion channels. However, both suffer from surface manganese dissolution and crystal structure degradation during high-pressure cycling, resulting in poor long-term cycling stability.

[0004] To address the structural damage and interfacial side reactions of cathode materials under high voltage, surface coating technology has proven to be an efficient and commonly used modification method. This technology constructs a protective layer on the surface of the cathode material, isolating the material from direct contact with the electrolyte, inhibiting metal ion dissolution and interfacial side reactions, and improving the material's structural stability and high-voltage cycling performance. Currently, mainstream surface coating technologies in the industry include oxide coating, phosphate coating, fluoride coating, and polymer coating. While these can isolate the electrolyte from the cathode material and suppress side reactions to some extent, oxide coating generally suffers from poor coating uniformity due to particle agglomeration, and some materials can hinder Li... +CN112599736A discloses a phosphate coating method, but the phosphate coating layer is brittle and prone to cracking and falling off during cycling. CN109244418B discloses a polymer coating method, which is easily oxidized and degraded under high pressure and has insufficient ion conduction efficiency. These common problems make it difficult for the modified cathode material to meet the application requirements of high-energy-density batteries in terms of charge-discharge capacity and cycle life, and there is an urgent need to develop a better coating system. Summary of the Invention

[0005] Based on the existing problems, the purpose of this invention is to provide a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating, its preparation method and application. By using iron molybdate sol for coating modification, the problem of poor structural stability of current cathode materials under high voltage is solved, thereby improving the structural stability of lithium-ion battery cathode materials and improving their charge-discharge capacity and cycle performance.

[0006] The first aspect of this invention provides a method for preparing a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating, comprising the following steps: S1. Dissolve Fe(NO3)3·9H2O in water, add citric acid solution, and stir at 50-60℃ to form an iron-citric acid complex solution; S2. Add a molybdenum source to the iron-citric acid complex solution obtained in S1, stir continuously and adjust the pH to obtain a uniform Fe2(MoO4)3 sol; S3. Disperse the lithium-ion battery cathode material in ethanol, then add the Fe2(MoO4)3 sol obtained in S2 according to the coating ratio and stir; S4. The mixture obtained in step S3 is filtered and washed, and the washed material is dried, ground, and calcined to obtain a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating.

[0007] Furthermore, the citric acid mentioned in step S1 is citric acid monohydrate, and the ratio of the total molar number of the citric acid monohydrate to the total molar number of molars of molybdenum and iron ions is 1.2-1.5:1.

[0008] Furthermore, in step S2, the molybdenum source is (NH4)6Mo7O 24 ·4H2O and / or Na2MoO4·2H2O, with a molar ratio of molybdenum to iron ranging from 1.5 to 1.9.

[0009] Furthermore, in step S2, ammonia is used to adjust the pH to 2-8.

[0010] Furthermore, the coverage rate in step S3 ranges from 5% to 10%.

[0011] Furthermore, the lithium-ion battery cathode material mentioned in step S3 includes, but is not limited to, single or doped modified high-voltage lithium-ion cathode materials such as lithium cobalt oxide, lithium manganese oxide, and lithium nickel manganese oxide.

[0012] Furthermore, in step S4, the drying temperature is 60-120℃ and the drying time is 8-12h.

[0013] Furthermore, in step S4, the calcination temperature is 450-600℃, the calcination time is 4-6h, the calcination heating rate is 2-5℃ / min, and the calcination atmosphere is an air atmosphere or an oxygen atmosphere.

[0014] A second aspect of the present invention provides a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating obtained according to the above preparation method.

[0015] The third aspect of this invention provides the application of the lithium-ion battery high-voltage cathode material based on iron molybdate sol coating in high-voltage lithium-ion batteries.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. This invention employs a ferric molybdate sol coating method. Leveraging the uniformity and dispersion stability of nanoscale colloidal particles in the sol system, a continuous, dense, and non-porous coating layer is constructed on the surface of the cathode material particles, eliminating side reaction sites. By controlling the amount of ferric molybdate sol added, the coating layer thickness can be quantitatively controlled, allowing for the selection of the optimal thickness to meet the performance requirements of different cathode materials. This avoids insufficient protection due to excessive thinness, while preventing Li-induced defects due to excessive thickness. + Transmission resistance balances protection and transmission performance.

[0017] 2. The iron molybdate used in this invention exhibits no electrochemical reaction within the high voltage range of 3.2-5V, possesses a stable crystal structure, and can maintain the integrity of the coating layer for a long period, forming a physical barrier to suppress surface and interface side reactions at the source. Its crystal structure also possesses good rigidity, which can constrain the cathode material in Li... + Volumetric deformation during the insertion / extraction process suppresses lattice expansion and collapse, reducing the probability of phase transition. Meanwhile, iron molybdate, as a fast lithium-ion conductor, exhibits continuous Li+ ions in its crystal structure. + The transmission channel can construct a continuous mass transfer path, significantly improving the lithium-ion diffusion coefficient and ensuring the quality of Li-ion diffusion during high-rate charge and discharge processes. + Rapid insertion / extraction avoids capacity decay and increased polarization.

[0018] 3. In this invention, the uniform and dense iron molybdate coating layer can reduce the loss of active sites in the cathode material, allowing it to fully utilize its theoretical capacity, while simultaneously reducing irreversible capacity loss caused by electrolyte decomposition and oxygen escape. Combined with the coating layer's effect of reducing interfacial charge transfer impedance, Li +The insertion / extraction process is more reversible, significantly improving the first-cycle coulombic efficiency. In addition, the iron molybdate coating has both structural stability and flexible adaptability, and is not prone to cracking or falling off during long-term high-voltage cycling. It can continuously play a protective and lithium-conducting role, effectively reducing the capacity decay rate and achieving simultaneous improvement in discharge specific capacity, first-cycle coulombic efficiency and cycle stability. Attached Figure Description

[0019] Figure 1 The charge-discharge curves of ferric molybdate are shown in the range of 2.5-5V.

[0020] Figure 2 The CV curves of ferric molybdate at 2.5-5V are shown.

[0021] Figure 3 This is a comparison chart of the cycle performance of Comparative Example 1 and Example 1.

[0022] Figure 4 This is the SEM image of Example 1.

[0023] Figure 5 This is the EDS diagram for Example 1.

[0024] Figure 6 This is the SEM image of Comparative Example 3. Detailed Implementation

[0025] The following specific embodiments further illustrate the technical solution and effects of the present invention. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0026] The equipment used in the preparation method of this invention can all be equipment known in the art. Unless otherwise specified, all raw materials used in this invention are commercially available.

[0027] The first aspect of this invention provides a method for preparing a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating, comprising the following steps: S1. Dissolve Fe(NO3)3·9H2O in water, add citric acid solution, and stir at 50-60℃ to form an iron-citric acid complex solution; S2. Add a molybdenum source to the iron-citric acid complex solution obtained in S1, stir continuously and adjust the pH to obtain a uniform Fe2(MoO4)3 sol; S3. Disperse the lithium-ion battery cathode material in ethanol, then add the Fe2(MoO4)3 sol obtained in S2 according to the coating ratio and stir; S4. The mixture obtained in step S3 is filtered and washed, and the washed material is dried, ground, and calcined to obtain a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating.

[0028] On the one hand, this invention utilizes ferric molybdate, which has stable electrochemical properties under high pressure, as a coating material, such as... Figure 1 As shown, ferric molybdate does not undergo its own redox reaction within the voltage range of 3.2-5V. Figure 2 The electrochemical inertness in the high-voltage range also eliminates the possibility that the coating layer interferes with the main reaction of the cathode material. On the other hand, this invention cleverly utilizes the properties of a sol to make ferric molybdate more uniformly dispersed in colloidal form, resulting in a more uniform coating of the cathode material. At the same time, the sol prevents premature agglomeration of ferric molybdate, and the generated ferric molybdate particles are small, even forming nanoscale ferric molybdate. Moreover, compared to the solution method, when the molybdenum source and iron source are mixed, ferric molybdate exists on the surface of the cathode material in a discontinuous island-like form, rather than a flat and continuous coating layer; at the same time, the solution precipitation method requires long-term heating to form ferric molybdate, and the cathode material will dissolve some metal ions under heating and acidic aqueous solutions.

[0029] Preferably, step S1 includes the following steps: dissolving Fe(NO3)3·9H2O in deionized water; dissolving citric acid monohydrate in deionized water at a molar ratio of 1.2-1.5 to total metal ions; adding the citric acid solution dropwise to the Fe(NO3)3·9H2O solution; and heating and stirring at 50-60°C for 20-30 minutes. Ferric nitrate nonahydrate is chosen as the iron source because of its excellent water solubility, which reduces the introduction of impurity ions and avoids the negative impact of other ions on battery performance. Citric acid mainly acts as a complexing agent, chelating agent, and dispersant, and undergoes thermal decomposition during subsequent heat treatment without affecting subsequent performance. 3+ In aqueous solution, it readily hydrolyzes to form Fe(OH)3 precipitate, leading to uneven dispersion of the iron source and ultimately affecting the uniformity of the ferric molybdate sol. Citric acid reacts with Fe through carboxyl and hydroxyl groups. 3+ MoO4 2- The chelation reaction forms a stable, soluble chelate; the molar ratio is set to 1.2-1.5:1, ensuring an excess of citric acid to achieve Fe... 3+ This ensures complete complexation while avoiding excessive citric acid that could lead to abnormal viscosity in the subsequent sol system, affecting the coating effect, and preventing carbon residue from hindering ion transport. A heating range of 50℃-60℃ is set to allow the complexation reaction to proceed more effectively.

[0030] Preferably, step S2 includes the following steps: adding (NH4)6Mo7O at a molar ratio of 1.5-1.9. 24 One or more molybdenum sources, such as ·4H2O and Na2MoO4·2H2O, are used. The mixture is stirred continuously for 20-30 minutes, and the pH is adjusted to 2-8. These two molybdenum sources are chosen because of their high water solubility and reactivity; both ammonium heptamolybdate tetrahydrate and sodium molybdate dihydrate can rapidly dissociate into MoO4 in water. 2-It can form a complex with Fe in the iron-citric acid compound. 3+ A homogeneous reaction occurs, generating ferric molybdate precursors. Compared to sparingly soluble molybdenum sources such as MoO3, this type of molybdenum source ensures uniform particle size in ferric molybdate colloidal particles; NH4 + During subsequent heat treatment, it decomposes into gas and escapes. The sodium salt byproduct of sodium molybdate can also be removed by washing with water or alcohol, leaving no metal ion residue and effectively ensuring the purity of the ferric molybdate product.

[0031] Preferably, step S3 includes the following steps: adding the cathode material to anhydrous ethanol, sonicating for 2-3 minutes, and slowly adding Fe2(MoO4)3 sol dropwise at a coating rate of 5-10%, while continuously stirring. Slow dropwise addition avoids excessively high local sol concentrations leading to colloidal agglomeration. Continuous stirring ensures that the sol particles are uniformly adsorbed on the surface of the cathode material particles, avoiding the defects of discontinuous coating in existing solution methods. The cathode material includes single or modified high-voltage lithium-ion cathode materials such as lithium cobalt oxide, lithium manganese oxide, and lithium nickel manganese oxide. Ethanol is chosen as the dispersion medium because of its low particle aggregation, allowing for rapid evaporation and removal. The coating rate must balance protection requirements with lithium conduction efficiency. If the coating rate is too low, the iron molybdate coating layer is too thin and cannot completely cover the cathode material surface, resulting in local exposure and potential metal ion dissolution and electrolyte erosion. If the coating rate is too high, the coating layer is too thick, which, even if iron molybdate is a fast lithium-ion conductor, will increase the lithium content of lithium ions. + The length of the transmission path leads to a decrease in lithium conduction efficiency and a deterioration in rate performance; the coating ratio can be adapted according to the characteristics of different cathode materials, and the coating thickness can be quantitatively controlled by controlling the amount of sol added.

[0032] Preferably, step S4 includes the following steps: drying the filtered and washed material in a vacuum drying oven at 60-120℃ for 8-12 hours; and calcining it at 450-600℃ for 4-6 hours in an air or oxygen atmosphere with a heating rate of 2-5℃ / min. Using vacuum drying instead of ordinary forced-air drying avoids oxidation reactions between oxygen in the air and the surface of the cathode material. The calcination temperature of 450-600℃ includes the crystal transformation temperature of ferric molybdate. With a fixed ferric molybdate ratio, as the calcination temperature increases, the Fe2(MoO4)3 obtained is purer, the sample has higher crystallinity, and the impurity content is relatively lower. However, excessively high temperatures can cause structural changes in the cathode material itself, such as the O3 phase transformation of LCO and spinel structure distortion of LMO. It may also lead to excessively large ferric molybdate grains, reducing lithium conductivity. Therefore, the optimal calcination temperature should be between 450-600℃. Slow heating at 2-5℃ / min avoids thermal stress between the coating layer and the cathode material caused by sudden temperature rise, which could lead to cracking and peeling of the coating layer. An air or oxygen atmosphere ensures that Fe and Mo in the iron molybdate remain in a high valence state, maintaining its fast lithium-ion conductor characteristics.

[0033] A second aspect of the present invention provides a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating obtained according to the above preparation method.

[0034] The third aspect of this invention provides the application of the lithium-ion battery high-voltage cathode material based on iron molybdate sol coating in high-voltage lithium-ion batteries.

[0035] Typical but non-limiting embodiments of the present invention are as follows: Example

[0036] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.2 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 89.5 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80℃ for 12 hours, ground, and then calcined in air at 5℃ / min to 550℃ for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating. The SEM image of the obtained product is shown below. Figure 4 See EDS chart Figure 5 .

[0037] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then vacuum-dried at 80°C. The cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2-4.6V and at a current density of 50 mA / g. The test results are shown in Table 1. The cyclic test graph is shown below. Figure 3 As shown. Example

[0038] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.2 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 89.5 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 min to obtain a uniform ferric molybdate sol, and adjust the pH to 7 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0039] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0040] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.2 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 89.5 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 min to obtain a uniform ferric molybdate sol, and adjust the pH to 8 with ammonia; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0041] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0042] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.2 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 89.5 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 min to obtain a uniform ferric molybdate sol, and adjust the pH to 7 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 490°C for 4 hours at a rate of 5°C / min to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0043] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0044] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.2 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 89.5 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 min to obtain a uniform ferric molybdate sol, and adjust the pH to 8 with ammonia; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 490°C for 4 hours at a rate of 5°C / min to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0045] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0046] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.1 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 122.7 mg Na2MoO4·2H2O to the iron-citric acid complex solution obtained in S1, and stir continuously for 30 min to obtain a uniform iron molybdate sol. Adjust the pH to 2 with ammonia. S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0047] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0048] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.1 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 122.7 mg Na2MoO4·2H2O to the iron-citric acid complex solution obtained in S1, and continue stirring for 30 min to obtain a uniform ferric molybdate sol. Adjust the pH to 7 with ammonia. S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0049] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0050] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.1 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 122.7 mg Na2MoO4·2H2O to the iron-citric acid complex solution obtained in S1, and continue stirring for 30 min to obtain a uniform ferric molybdate sol. Adjust the pH to 8 with ammonia. S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0051] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0052] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.2 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 89.5 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 600°C for 5 hours at a rate of 5°C / min to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0053] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0054] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 230.1 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 101.4 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0055] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0056] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 247.3 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 113.4 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0057] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0058] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 267.8 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 113.4 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0059] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0060] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 287.6 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 101.4 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0061] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0062] S1. Dissolve 109.3 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 170.5 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 71.6 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at an 8% coating rate, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0063] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0064] S1. Dissolve 109.3 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 184.7 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 71.6 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at an 8% coating rate, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0065] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0066] S1. Dissolve 68.3 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 106.7 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 44.8 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 5%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0067] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2–4.6 V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0068] S1. Dissolve 68.3 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 133.3 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 44.8 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LCO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 5%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The washed material is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0069] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to form a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C followed by vacuum drying at 80°C, and then rolled and cut into sheets to obtain the cathode sheet. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.2-4.6V and at a current density of 50 mA / g. The test results are shown in Table 1. Example

[0070] S1. Dissolve 136.6 mg Fe(NO3)3·9H2O in 5 ml of deionized water, dissolve 213.2 mg citric acid in 5 ml of deionized water, add the citric acid solution dropwise into the Fe(NO3)3·9H2O solution, stir at 50°C for 20 min until a clear yellow solution is obtained, forming an iron-citric acid complex solution. S2. Slowly add 89.5 mg of (NH4)6Mo7O to the iron-citric acid complex solution obtained in S1. 24 ·4H2O, stir continuously for 30 minutes to obtain a uniform ferric molybdate sol, and adjust the pH to 3 with ammonia water; S3. Disperse 1g LNMO in 10ml anhydrous ethanol by ultrasonic stirring for 3min, and slowly add the ferric molybdate sol obtained in step S2 at a coating rate of 10%, while maintaining vigorous stirring during the process. S4. The mixture obtained in step S3 is filtered and washed. The material obtained after washing is dried at 80°C for 12 hours, ground, and calcined in air at 5°C / min to 550°C for 4 hours to obtain a high-voltage lithium-ion battery cathode material based on iron molybdate sol coating.

[0071] The high-voltage lithium-ion battery cathode material based on iron molybdate sol coating obtained in S4, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil, dried in a forced-air environment at 60°C, and then vacuum-dried at 80°C. The resulting cathode sheet was obtained by roll pressing. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The anode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted in the voltage range of 3.5–4.95 V and at a current density of 50 mA / g. The test results are shown in Table 1.

[0072] Comparative Example 1 LCO, PVDF, and conductive carbon black were added to NMP in an 8:1:1 ratio to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C and then under vacuum at 80°C. The resulting sheets were then rolled and cut to obtain the positive electrode. The electrolyte was a 1 mol / L LiPF6EC / EMC solution (Vol% 3:7). The negative electrode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted at a voltage range of 3.2–4.6 V and a current density of 50 mA / g. The test results are shown in Table 1. The cyclic test graph is shown below. Figure 3 As shown.

[0073] Comparative Example 2 LNMO, PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to prepare a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air environment at 60°C followed by vacuum drying at 80°C. The resulting sheet was then cut into positive electrode plates using a roll press. The electrolyte was a 1 mol / L LiPF6EC / EMC solution (Vol% 3:7). The negative electrode was a lithium sheet, and the cells were assembled into coin cells in a glove box. Cyclic tests were conducted at a voltage range of 3.5–4.95 V and a current density of 50 mA / g. The test results are shown in Table 1. The cyclic test graph is shown below. Figure 3 As shown.

[0074] Comparative Example 3 The coating of ferric molybdate was performed using a solution precipitation method, and the steps are as follows: (1) Dissolve ammonium molybdate in deionized water, add LCO and stir until homogeneous; (2) Add ferric nitrate solution slowly dropwise while heating and stirring, and then boil; (3) After filtration, washing, drying and calcination, the coated and modified cathode material is obtained.

[0075] (4) The modified positive electrode material obtained in step (3), PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to form a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried by forced air at 60°C and then by vacuum drying at 80°C. The positive electrode sheet was obtained by roll pressing and cutting. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The negative electrode was a lithium sheet, which was assembled into a coin cell in a glove box. Cyclic tests were performed in the voltage range of 3.2-4.6V and the current density of 50mA / g. The test results are shown in Table 1.

[0076] Comparative Example 4 The coating of ferric molybdate was performed using a ball milling method, and the steps are as follows: (1) Add LCO and the ferric molybdate synthesized by the above solution precipitation method into a ball mill jar at a ball-to-material ratio of 10:1, add an appropriate amount of alcohol, and ball mill; (2) After drying and calcination, the modified cathode material is obtained.

[0077] (3) The modified positive electrode material obtained in step (2), PVDF, and conductive carbon black were added to NMP at a ratio of 8:1:1 to form a slurry, which was then coated onto carbon-coated aluminum foil. The slurry was dried in a forced-air drying process at 60°C and then in a vacuum drying process at 80°C. The positive electrode sheet was obtained by roll pressing and cutting. The electrolyte was 1 mol / L LiPF6EC / EMC (Vol% 3:7). The negative electrode was a lithium sheet, which was assembled into a coin cell in a glove box. Cyclic tests were performed in the voltage range of 3.2-4.6V and the current density of 50mA / g. The test results are shown in Table 1.

[0078] Table 1 Performance of each embodiment and comparative example

[0079] Based on the comparative analysis of the electrochemical performance data of the examples and comparative examples in Table 1, it can be seen that the iron molybdate sol-gel coating process adopted in this invention can significantly improve the first-cycle discharge specific capacity and first-cycle efficiency of high-voltage lithium cobalt oxide (LCO) and lithium nickel manganese oxide (LNMO) cathode materials. The discharge specific capacity of all examples is significantly higher than that of the uncoated original material, proving that the uniform iron molybdate coating layer effectively improves the interface and structural stability of the material under high voltage of 3.2-5V, thereby releasing higher capacity. Among LCO, Example 1 has the best performance, with a capacity of 218mAh / g. In contrast, the traditional solution precipitation method in Comparative Example 3 caused serious damage to the material due to prolonged heating in acidic aqueous solution, resulting in a significant deterioration in both capacity and first-cycle efficiency. The coating condition is as follows: Figure 6 As shown, the coating exhibits a discontinuous island-like structure. Although the ball milling method in Comparative Example 4 avoided the solution environment problem, the coating uniformity was insufficient, and the capacity was still significantly lower than that of all other examples. In summary, the data in Table 1 fully demonstrate the unique advantages of the sol-gel coating method of this invention in achieving uniform and dense coating, and can effectively improve the electrochemical performance of high-voltage cathode materials.

Claims

1. A method for preparing a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating, characterized in that, Includes the following steps: S1. Dissolve Fe(NO3)3·9H2O in water, add citric acid solution, and stir at 50-60℃ to form an iron-citric acid complex solution; S2. Add a molybdenum source to the iron-citric acid complex solution obtained in S1, stir continuously and adjust the pH to obtain a uniform Fe2(MoO4)3 sol; S3. Disperse the lithium-ion battery cathode material in ethanol, then add the Fe2(MoO4)3 sol obtained in S2 according to the coating ratio and stir; S4. The mixture obtained in step S3 is filtered and washed, and the washed material is dried, ground, and calcined to obtain a high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating.

2. The method for preparing high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating according to claim 1, characterized in that: The citric acid mentioned in step S1 is citric acid monohydrate, and the ratio of the total molar number of the citric acid monohydrate to the total molar number of molars of molybdenum and iron ions is 1.2-1.5:

1.

3. The method for preparing high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating according to claim 1, characterized in that: In step S2, the molybdenum source is (NH4)6Mo7O 24 ·4H2O and / or Na2MoO 4· 2H2O, the molar ratio of molybdenum to iron ranges from 1.5 to 1.

9.

4. The method for preparing the high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating according to claim 1, characterized in that: In step S2, ammonia is used to adjust the pH to 2-8.

5. The method for preparing high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating according to claim 1, characterized in that: The coating rate range mentioned in step S3 is 5-10%.

6. The method for preparing high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating according to claim 1, characterized in that: In step S4, the drying temperature is 60-120℃ and the drying time is 8-12h.

7. The method for preparing high-voltage cathode material for lithium-ion batteries based on iron molybdate sol coating according to claim 1, characterized in that: In step S4, the calcination temperature is 450-600℃, the calcination time is 4-6h, the calcination heating rate is 2-5℃ / min, and the calcination atmosphere is air or oxygen.

8. The lithium-ion battery high-voltage cathode material based on iron molybdate sol coating obtained by the preparation method of the lithium-ion battery high-voltage cathode material based on iron molybdate sol coating according to any one of claims 1-7.

9. The application of the lithium-ion battery high-voltage cathode material based on iron molybdate sol coating as described in claim 8 in high-voltage lithium-ion batteries.

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