Preparation method of high cycle life lithium ion battery surface modified electrode material

Abstract

The application belongs to the technical field of lithium ion battery electrode material preparation, and particularly relates to a preparation method of a high-cycle-life lithium ion battery surface modified electrode material, comprising the following steps: S1. electrode substrate pretreatment; S2. modification liquid preparation; S3. surface coating modification; S4. post-treatment; and S5. modification verification. The application forms a uniform, dense and stable coating layer on the surface of the electrode material by pretreating the electrode substrate, preparing a composite modification liquid with a specific composition, adopting ultrasonic-stirring cooperative coating combined with post-treatment, effectively inhibiting the side reaction of the electrode and the electrolyte, relieving the volume expansion, improving the cycle stability of the electrode material, and simultaneously, the method is simple in process, strong in controllability and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrode material preparation technology, specifically relating to a method for preparing a surface-modified electrode material for high cycle life lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, with their superior performance such as high energy density, long cycle life, and low self-discharge rate, have been widely used in portable electronic devices, electric vehicles, energy storage systems, and many other fields. Electrode materials, as a core component of lithium-ion batteries, directly determine the battery's key performance indicators such as energy density, cycle stability, and safety.

[0003] However, traditional lithium-ion battery electrode materials are prone to a series of problems during long-term charge-discharge cycles: On the one hand, side reactions can occur between the electrode material and the electrolyte, forming an unstable interfacial film that leads to continuous electrolyte decomposition and reduces battery cycle life; on the other hand, some electrode materials experience significant volume expansion and contraction during lithium-ion insertion / extraction, causing electrode material particles to break and pulverize, damaging the integrity of the electrode structure and further exacerbating battery performance degradation. Furthermore, impurities and functional groups such as hydroxyl groups on the electrode material surface can also affect lithium-ion transport rates and interfacial stability, hindering improvements in battery performance.

[0004] To address these issues, researchers have proposed surface modification techniques for electrode materials. By coating the electrode material surface with a stable modified layer, side reactions between the electrode and electrolyte are suppressed, volume expansion is mitigated, and interfacial stability is improved. Currently reported surface modification methods include sol-gel methods, chemical vapor deposition (CVD), hydrothermal methods, and mechanical ball milling. However, these methods generally have some drawbacks: for example, the gelation time is difficult to control during the sol-gel process, easily leading to uneven coating thickness; CVD equipment is expensive and the process is complex, making large-scale production difficult; hydrothermal methods require harsh reaction conditions and have high energy consumption; and mechanical ball milling can easily damage the crystal structure of the electrode material, affecting its electrochemical performance.

[0005] Therefore, developing a surface modification preparation method that is simple, low-cost, and has good coating uniformity, and can significantly improve the cycle life of lithium-ion battery electrode materials, has important practical significance and application value. Summary of the Invention

[0006] To address the problems of insufficient cycle life of lithium-ion battery electrode materials and defects in surface modification methods in existing technologies, this invention provides a method for preparing surface-modified electrode materials for lithium-ion batteries with high cycle life.

[0007] Based on this, one of the objectives of this invention is to provide a method for preparing modified electrode materials. This method involves systematically pretreating the electrode substrate, preparing a composite modification liquid with a specific composition, and using an ultrasonic-stirring synergistic coating combined with post-treatment process to form a uniform, dense, and stable coating layer on the surface of the electrode material. This effectively suppresses side reactions between the electrode and the electrolyte, alleviates volume expansion, and improves the cycle stability of the electrode material. At the same time, this method is simple, highly controllable, and suitable for large-scale production.

[0008] The specific technical solution adopted by this invention is as follows:

[0009] A method for preparing a modified electrode material includes the following steps:

[0010] Step S1. Coat the pretreated electrode substrate with a modified liquid to obtain a coating intermediate;

[0011] Step S2. The coating intermediate is calcined under a protective gas atmosphere to obtain a modified electrode material coated on the surface of the electrode substrate.

[0012] Furthermore, the modified liquid includes a phosphorus-containing compound, a metal oxide, a dispersant, and a solvent; based on the total mass of the modified liquid, the mass fraction of the dispersant is 5-20%, and the mass fraction of the phosphorus-containing compound and the metal oxide is 0.5-5 wt%, wherein the mass ratio of the phosphorus-containing compound to the metal oxide is 1:0.5-3.

[0013] Furthermore, the phosphorus-containing compound is at least one of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphorous acid, and pyrophosphate; the metal oxide is at least one of Al2O3, TiO2, ZrO2, MgO, and LiPO3, and the particle size of the metal oxide is 10-100 nm.

[0014] Furthermore, the dispersant is at least one of polyvinylpyrrolidone, polyethylene glycol, and sodium dodecylbenzenesulfonate; the solvent is one or more of deionized water, ethanol, or N-methylpyrrolidone.

[0015] Furthermore, the coating conditions in step S1 are: irradiation at a temperature of 30-80°C with the aid of 200-300nm ultraviolet light; wherein the irradiation power is 50-150W and the irradiation time is 30-90min.

[0016] Furthermore, the calcination conditions in step S2 are: calcining at 300-600℃ for 1-4 hours with a heating rate of 2-10℃ / min;

[0017] The protective gas atmosphere is any one of nitrogen, argon, and helium.

[0018] Furthermore, in step 1, the purity of the electrode substrate is ≥99.5%, and the particle size is 1-10 μm;

[0019] The electrode substrate includes a positive electrode substrate and a negative electrode substrate.

[0020] Furthermore, the positive electrode substrate includes at least one of LiCoO2, LiFePO4, LiNi1 / 3Co1 / 3Mn1 / 3O2, LiNi0.8Co0.1Mn0.1O2, and LiMn2O4;

[0021] The negative electrode substrate includes at least one of natural graphite, artificial graphite, hard carbon, soft carbon, and silicon-based materials.

[0022] A second objective of this invention is to provide a modified electrode material, which is prepared by the preparation method described in one objective.

[0023] Furthermore, the thickness of the modified electrode material is 5-50 nm.

[0024] The technical effects achieved by this invention are as follows:

[0025] This invention employs a systematic pretreatment process for the electrode substrate, including airflow pulverization, grading and sieving, ultrasonic washing, and vacuum drying. This effectively removes oil, residual impurities, and surface hydroxyl groups from the substrate surface, ensuring high purity and uniform particle size distribution, thus laying a solid foundation for subsequent uniform coating. Simultaneously, by controlling the pulverization pressure and sieving standards, the particle size of the substrate is precisely controlled within the range of 1-10 μm. This particle size range ensures a large specific surface area to improve lithium-ion insertion / extraction efficiency while avoiding agglomeration caused by excessively small particles.

[0026] This invention employs a composite modifier of phosphorus-containing compounds and metal oxides, whose synergistic effect significantly improves the performance of the coating layer: the phosphorus-containing compounds form a stable phosphate passivation layer on the electrode surface, which can effectively inhibit electrolyte decomposition and electrode material dissolution; the metal oxides improve the mechanical strength and ion conduction performance of the coating layer, and alleviate the volume expansion and contraction of the electrode material during charging and discharging. The mass ratio of the two is controlled at 1:0.5-3, which can achieve the optimal balance between the protective performance and ion transport performance of the coating layer.

[0027] This invention employs a gradient stirring and dispersion method combined with nitrogen protection during the preparation of the modified liquid. It first performs initial dispersion at low speed and then refines the dispersion at high speed, which effectively prevents the agglomeration of modifier particles and ensures the uniformity and stability of the modified liquid. At the same time, impurity particles are further removed by filtration through a filter membrane, which avoids defects in the subsequent coating layer and improves the coating quality.

[0028] This invention employs a coating method that combines ultrasonic dispersion and mechanical stirring, along with an ultrasonic-stirring cycle, to ensure that the modifier is uniformly adsorbed and deposited on the substrate surface, forming a uniform and dense coating layer. Simultaneously, ultraviolet-assisted irradiation promotes the activation of the modifier molecules, enhances the bonding force between the modifier and the substrate surface, and ensures a strong bond between the coating layer and the substrate, further improving the cycle stability of the electrode material.

[0029] The post-processing technology of this invention is scientific and reasonable. Step-by-step washing can thoroughly remove residual impurities and solvents. Precisely controlled drying and calcination parameters prevent cracking of the coating intermediate and oxidation of the coating layer. High-temperature calcination causes the coating layer to crystallize, further improving the density and stability of the coating layer. Cooling in the furnace after calcination prevents the coating layer from falling off due to thermal stress, ensuring the structural integrity of the modified electrode material.

[0030] This invention adds a modification verification step, which ensures that the modification effect meets the design requirements through multi-dimensional detection. For unqualified products, parameters can be adjusted and reprocessed, thereby improving the product qualification rate. At the same time, the preparation method is simple, highly controllable, energy-efficient, and low-cost, making it suitable for large-scale industrial production.

[0031] The surface-modified electrode material prepared by the method of this invention exhibits excellent cycle stability when applied to lithium-ion batteries. At a 1C charge-discharge rate, the capacity retention rate after 1000 cycles can reach more than 85%, which is significantly better than that of traditional unmodified electrode materials. At the same time, it can also improve the rate performance and safety of the battery, and has broad application prospects. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a method for preparing a surface-modified electrode material for a high cycle life lithium-ion battery according to the present invention;

[0033] Figure 2 This is a capacity retention rate versus cycle number relationship graph of Example 1 of the preparation method of a surface-modified electrode material for a high cycle life lithium-ion battery according to the present invention;

[0034] Figure 3 This is a capacity retention rate versus cycle number relationship graph from Example 2 of the preparation method of a surface-modified electrode material for a high cycle life lithium-ion battery according to the present invention.

[0035] Figure 4 This is a capacity retention rate versus cycle number graph of Example 3 of the preparation method of a surface-modified electrode material for a high cycle life lithium-ion battery according to the present invention. Detailed Implementation

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] However, this application may be exemplified in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete and will fully convey the scope of this application to those skilled in the art.

[0038] An embodiment of the first aspect of the present invention provides a method for preparing a modified electrode material, the method comprising the following steps:

[0039] S1. Electrode substrate pretreatment: Select lithium-ion battery positive electrode substrate or negative electrode substrate, and sequentially perform air jet milling, 200-400 mesh sieving, ultrasonic washing with a mixed solution of anhydrous ethanol and deionized water, and drying treatment to obtain a pretreated substrate with a purity ≥99.5% and a particle size of 1-10μm with uniform distribution.

[0040] S2. Preparation of modified solution: A composite modifier, dispersant, and solvent, consisting of a phosphorus-containing compound and a metal oxide at a mass ratio of 1:0.5-3, are mixed and dispersed uniformly by gradient stirring under nitrogen protection. The mixture is then filtered under pressure through a 0.22-0.45μm filter membrane to obtain the modified solution. The mass fraction of the modifier in the modified solution is 0.5-5wt%, and the amount of dispersant added is 5-20% of the mass of the modifier.

[0041] S3. Surface coating modification: The pretreated substrate is added to the modification solution at a solid-liquid ratio of 1:5-1:20 g / mL. After ultrasonic-stirring cycle treatment for 3-6 times, ultrasonic dispersion and mechanical stirring are carried out simultaneously for 1-3 hours. During the coating reaction, 200-300nm ultraviolet light is applied and the reaction temperature is 30-80℃ to obtain the coating intermediate.

[0042] S4. Post-processing: The coated intermediate is sequentially vacuum filtered, washed stepwise with deionized water and anhydrous ethanol, dried, and calcined at 300-600℃ under inert gas protection. After calcination, it is cooled to room temperature in the furnace to obtain the surface-modified electrode material.

[0043] S5. Modification Verification: Inspect the surface morphology, 5-50nm coating thickness, and elemental composition of the surface-modified electrode material. A qualified product is one where the deviation of characteristic element content is ≤±5% and the coating has no obvious defects. If the product is unqualified, adjust the parameters and re-prepare.

[0044] In a preferred embodiment, the positive electrode substrate is one or more of LiCoO2, LiFePO4, LiNi1 / 3Co1 / 3Mn1 / 3O2, LiNi0.8Co0.1Mn0.1O2, or LiMn2O4; and the negative electrode substrate is one or more of natural graphite, artificial graphite, hard carbon, soft carbon, or silicon-based materials.

[0045] In a preferred embodiment, the phosphorus-containing compound is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphorous acid, or pyrophosphoric acid; the metal oxide is one or more of Al2O3, TiO2, ZrO2, MgO, or LiPO3, and the particle size of the metal oxide is 10-100 nm.

[0046] In a preferred embodiment, the dispersant is one or more of polyvinylpyrrolidone, polyethylene glycol, or sodium dodecylbenzenesulfonate; and the solvent is one or more of deionized water, ethanol, or N-methylpyrrolidone.

[0047] In a preferred embodiment, in step S3, the ultrasonic power is 100-300W, the stirring speed is 300-800r / min, the ultraviolet irradiation power is 50-150W, and the irradiation time is 30-90min.

[0048] In a preferred embodiment, in step S4, the drying temperature is 60-100℃, the calcination heating rate is 2-10℃ / min, and the calcination time is 1-4h; the inert gas is one of nitrogen, argon, or helium.

[0049] In a preferred embodiment, in step S5, a scanning electron microscope is used to detect the surface morphology, a transmission electron microscope is used to detect the coating thickness, and an X-ray photoelectron spectroscopy is used to detect the elemental composition.

[0050] In a preferred embodiment, in step S5, the surface morphology detection is performed using a scanning electron microscope with a magnification of 5000-50000x, preferably 10000-30000x. At least five different detection areas are selected during the detection to ensure the representativeness of the results. The morphology of the coating layer and the particle dispersion state on the substrate surface can be clearly observed through the SEM image. The coating layer thickness detection is performed using a transmission electron microscope, and the sample is prepared into an ultrathin section with a section thickness of 50-100nm. The elemental composition detection is performed using an X-ray photoelectron spectroscopy with a detection range of 0-1000eV and a detection resolution of 0.1eV.

[0051] In a preferred embodiment, the ultrasonic cleaning uses an ultrasonic power of 80-200W, preferably 120-180W, and an ultrasonic frequency of 25-60kHz. Appropriate ultrasonic power and frequency can efficiently remove impurities from the substrate surface without damaging the substrate particles. In the mixed solution of anhydrous ethanol and deionized water, the volume ratio of anhydrous ethanol to deionized water is 1:1-1:5, preferably 1:2-1:3. This ratio of mixed solution has good dissolving ability for both oil stains and water-soluble impurities on the substrate surface. Drying is performed using a vacuum drying method with a vacuum degree of -0.06 to -0.1MPa, preferably -0.08 to -0.1MPa. After drying, the particle size distribution of the pretreated substrate is detected to ensure that the particle size distribution span is ≤2.

[0052] In a preferred embodiment, in step S2, after the modified liquid is prepared, it is filtered through a 0.22-0.45μm filter membrane, preferably a 0.3μm filter membrane. The filtration is performed under pressure at a pressure of 0.1-0.3MPa. Filtration removes incompletely dispersed impurity particles and modifier agglomerates from the modified liquid, preventing defects in the coating layer caused by such particles during subsequent coating processes. In step S3, ultraviolet (UV) assisted irradiation is also required during the coating reaction. The UV wavelength is 200-300nm, preferably 250-280nm, the irradiation power is 50-150W, preferably 80-120W, and the irradiation time is 30-90min, preferably 45-60min. During UV irradiation, the distance between the irradiation source and the reaction system is maintained at 10-20cm, and the reaction system is continuously stirred to ensure that all substrate particles receive uniform UV irradiation.

[0053] An embodiment of the second aspect of the present invention provides a modified electrode material obtained based on the preparation method of the embodiment of the first aspect.

[0054] In a preferred embodiment, the thickness of the modified electrode material located on the electrode substrate is 5-50 nm.

[0055] The technical solution of the present invention will be further described below through specific embodiments.

[0056] Example

[0057] Example 1

[0058] A method for preparing a surface-modified electrode material for high cycle life lithium-ion batteries includes the following steps:

[0059] S1. Electrode substrate pretreatment: Select lithium-ion battery positive electrode substrate or negative electrode substrate, and sequentially perform air jet milling, 200-400 mesh sieving, ultrasonic washing with a mixed solution of anhydrous ethanol and deionized water, and drying treatment to obtain a pretreated substrate with a purity ≥99.5% and a particle size of 1-10μm with uniform distribution.

[0060] S2. Preparation of modified solution: A composite modifier, dispersant, and solvent, consisting of a phosphorus-containing compound and a metal oxide at a mass ratio of 1:0.5-3, are mixed and dispersed uniformly by gradient stirring under nitrogen protection. The mixture is then filtered under pressure through a 0.22-0.45μm filter membrane to obtain the modified solution. The mass fraction of the modifier in the modified solution is 0.5-5wt%, and the amount of dispersant added is 5-20% of the mass of the modifier.

[0061] S3. Surface coating modification: The pretreated substrate is added to the modification solution at a solid-liquid ratio of 1:5-1:20 g / mL. After ultrasonic-stirring cycle treatment for 3-6 times, ultrasonic dispersion and mechanical stirring are carried out simultaneously for 1-3 hours. During the coating reaction, 200-300nm ultraviolet light is applied and the reaction temperature is 30-80℃ to obtain the coating intermediate.

[0062] S4. Post-processing: The coated intermediate is sequentially vacuum filtered, washed stepwise with deionized water and anhydrous ethanol, dried, and calcined at 300-600℃ under inert gas protection. After calcination, it is cooled to room temperature in the furnace to obtain the surface-modified electrode material.

[0063] S5. Modification Verification: Inspect the surface morphology, 5-50nm coating thickness, and elemental composition of the surface-modified electrode material. A qualified product is one where the deviation of characteristic element content is ≤±5% and the coating has no obvious defects. If the product is unqualified, adjust the parameters and re-prepare.

[0064] The surface-modified electrode material prepared in this embodiment was used to make a positive electrode sheet, which was then assembled with a natural graphite negative electrode, electrolyte, and separator to form a CR2032 coin cell. Cyclic performance was tested at a 1C charge-discharge rate, and the capacity retention rate after 1000 cycles was 88.5%.

[0065] Example 2

[0066] A method for preparing a surface-modified electrode material for high cycle life lithium-ion batteries includes the following steps:

[0067] S1. Electrode Substrate Pretreatment: Nano-silicon powder was selected as the negative electrode substrate and underwent crushing, sieving, washing, and drying processes sequentially. Crushing was performed using airflow pulverization, with the nozzle orifice diameter adjusted to 0.8 mm and the pulverization pressure controlled at 0.4 MPa to achieve a substrate particle size of 1-5 μm. Sieving was conducted using a 200-400 mesh standard sieve, first removing large particles through a 200 mesh sieve, then collecting particles from the 400 mesh sieve. Washing involved ultrasonic washing four times with a mixed solution of anhydrous ethanol and deionized water, each wash lasting 15 minutes, with an ultrasonic power of 120 W and an ultrasonic frequency of 30 kHz. Drying was performed using a vacuum drying method at 90℃ for 5 hours, with a vacuum degree of -0.08 MPa. Ventilation was conducted every hour during the drying process to obtain a pretreated substrate with a purity ≥99.5% and a particle size distribution range ≤2.

[0068] S2. Preparation of modified solution: Phosphoric acid and anatase TiO2 are mixed at a mass ratio of 1:2 as the modifier, polyethylene glycol is used as the dispersant, and the amount of dispersant added is 15% of the mass of the modifier. Ethanol and N-methylpyrrolidone are used as the mixed solvent. The modifier, dispersant and solvent are mixed, and the mass fraction of the modifier in the modified solution is 3wt%. Gradient stirring and dispersion are carried out under a nitrogen protective atmosphere. First, the stirring speed is 250 r / min for 20 min, and then the stirring speed is 700 r / min for 30 min. The nitrogen gas introduction rate is 0.2 L / min. After stirring, the mixture is allowed to stand for 20 min. No precipitation or stratification is observed. Then, the mixture is filtered under pressure through a 0.3 μm filter membrane to obtain the modified solution.

[0069] S3. Surface Coating Modification: The pretreated substrate obtained in step S1 was added to the modified solution prepared in step S2 at a solid-liquid ratio of 1:10 g / mL. The mixture was first ultrasonically dispersed for 5 min, then mechanically stirred for 10 min. This ultrasonic-stirring cycle was repeated 5 times. After the cycle, ultrasonic dispersion and mechanical stirring were performed simultaneously for 1.5 h. The ultrasonic power was 150 W, the stirring speed was 600 r / min, and the reaction temperature was 45 °C. During the coating reaction, ultraviolet light was used for assisted irradiation. The ultraviolet wavelength was 270 nm, the irradiation power was 80 W, and the irradiation time was 60 min. The distance between the irradiation source and the reaction system was kept at 12 cm, and the reaction system was continuously stirred. After the reaction, the coated intermediate was obtained.

[0070] S4. Post-processing: The coated intermediate obtained in step S3 was filtered by vacuum filtration; first, it was washed with deionized water at a rate of 60 mL / g of substrate, and filtered after each wash until the pH of the washing solution was 6.8; then it was washed once with anhydrous ethanol at a rate of 40 mL / g of substrate; after washing, it was vacuum dried at a temperature of 75℃ for 5 hours, a vacuum degree of -0.09 MPa, and a heating rate of 2℃ / min; after drying, it was calcined under an argon protective atmosphere with an argon purity of ≥99.99%, an argon flow rate of 0.4 L / min, a calcination temperature of 400℃, a heating rate of 4℃ / min, and a calcination time of 3 hours; after calcination, it was cooled to room temperature in the furnace to obtain the surface-modified electrode material.

[0071] S5. Modification Verification: The surface morphology was examined using a scanning electron microscope, and it was observed that the coating layer uniformly covered the substrate surface without defects, cracks, or agglomeration. The thickness of the coating layer was examined using a transmission electron microscope, and the thickness was measured to be 18 nm. The elemental composition was examined using an X-ray photoelectron spectroscopy instrument, and it was confirmed that phosphorus and titanium elements had been successfully deposited on the substrate surface with an elemental content deviation of ±1.5%, which was deemed as a qualified product.

[0072] The surface-modified electrode material prepared in this embodiment was used to make a negative electrode sheet, which was then assembled with a LiCoO2 positive electrode, electrolyte, and separator to form a CR2032 coin cell. Cyclic performance was tested at a 1C charge-discharge rate, and the capacity retention rate after 1000 cycles was 86.2%.

[0073] Example 3

[0074] A method for preparing a surface-modified electrode material for high cycle life lithium-ion batteries includes the following steps:

[0075] S1. Electrode Substrate Pretreatment: LiFePO4 was selected as the positive electrode substrate and subjected to crushing, sieving, washing, and drying processes in sequence. Crushing was performed using airflow pulverization, with the nozzle orifice diameter adjusted to 1.5 mm and the pulverization pressure controlled at 0.6 MPa to achieve a substrate particle size of 1-5 μm. Sieving was conducted using a 200-400 mesh standard sieve, first removing large particles through a 200 mesh sieve, then collecting particles from the 400 mesh sieve. Washing involved ultrasonic washing twice with a mixed solution of anhydrous ethanol and deionized water, each wash lasting 30 minutes, with an ultrasonic power of 180 W and an ultrasonic frequency of 50 kHz. Drying was performed under vacuum at 110℃ for 4 hours, with a vacuum degree of -0.1 MPa. Ventilation was conducted every hour during the drying process to obtain a pretreated substrate with a purity ≥99.5% and a particle size distribution range ≤2.

[0076] S2. Preparation of modified solution: Pyrophosphate and monoclinic ZrO2 were mixed at a mass ratio of 1:0.8 as the modifier, sodium dodecylbenzenesulfonate was used as the dispersant, and the amount of dispersant added was 8% of the mass of the modifier. Deionized water was used as the solvent. The modifier, dispersant and solvent were mixed, and the mass fraction of the modifier in the modified solution was 1 wt%. Gradient stirring and dispersion were carried out under a nitrogen protective atmosphere. First, the mixture was stirred at a speed of 350 r / min for 12 min, and then stirred at a speed of 500 r / min for 60 min. The nitrogen gas introduction rate was 0.3 L / min. After stirring, the mixture was allowed to stand for 10 min. No precipitation or stratification was observed. The mixture was then filtered under pressure through a 0.22 μm filter membrane to obtain the modified solution.

[0077] S3. Surface Coating Modification: The pretreated substrate obtained in step S1 was added to the modified solution prepared in step S2 at a solid-liquid ratio of 1:15 g / mL. The mixture was first ultrasonically dispersed for 3 min, then mechanically stirred for 15 min. This ultrasonic-stirring cycle was repeated 3 times. After the cycle, ultrasonic dispersion and mechanical stirring were performed simultaneously for 3 h. The ultrasonic power was 250 W, the stirring speed was 400 r / min, and the reaction temperature was 55 °C. During the coating reaction, ultraviolet light was used for assisted irradiation. The ultraviolet wavelength was 250 nm, the irradiation power was 120 W, and the irradiation time was 45 min. The distance between the irradiation source and the reaction system was kept at 18 cm, and the reaction system was continuously stirred. After the reaction, the coated intermediate was obtained.

[0078] S4. Post-processing: The coated intermediate obtained in step S3 was filtered by vacuum filtration; first, it was washed with deionized water at a rate of 100 mL / g of substrate, and filtered after each wash until the pH of the washing solution was 7.2; then, it was washed twice with anhydrous ethanol at a rate of 25 mL / g of substrate; after washing, it was dried by forced air at a temperature of 90℃ for 3 hours at a heating rate of 5℃ / min; after drying, it was calcined under a nitrogen protective atmosphere with a nitrogen purity ≥99.99%, a nitrogen flow rate of 0.6 L / min, a calcination temperature of 500℃, a heating rate of 6℃ / min, and a calcination time of 2 hours; after calcination, it was cooled to room temperature in the furnace to obtain the surface-modified electrode material.

[0079] S5. Modification Verification: The surface morphology was examined using a scanning electron microscope (15,000x magnification, 5 detection areas selected). It was observed that the coating layer uniformly covered the substrate surface without defects, cracks, or agglomeration. The coating layer thickness was measured to be 35 nm using a transmission electron microscope. The elemental composition was analyzed using X-ray photoelectron spectroscopy, confirming that phosphorus and zirconium elements had been successfully deposited on the substrate surface. The elemental content deviation was ±3%, and the product was deemed qualified.

[0080] The surface-modified electrode material prepared in this embodiment was used to make a positive electrode sheet, which was then assembled with an artificial graphite negative electrode, electrolyte, and separator to form a CR2032 coin cell. Cyclic performance was tested at a 1C charge-discharge rate, and the capacity retention rate after 1000 cycles was 87.8%.

[0081] In this invention, a systematic pretreatment of the electrode substrate, including airflow pulverization, grading and sieving, ultrasonic washing, and vacuum drying, effectively removes oil, residual impurities, and surface hydroxyl groups from the substrate surface, ensuring high purity and uniform particle size distribution, laying a solid foundation for subsequent uniform coating. Simultaneously, by controlling the pulverization pressure and sieving standards, the particle size of the substrate is precisely controlled within 1-10 μm. This particle size range ensures a large specific surface area to improve lithium-ion insertion / extraction efficiency while avoiding agglomeration caused by excessively small particles. A composite modifier of phosphorus-containing compounds and metal oxides is used, and their synergistic effect significantly improves the performance of the coating layer: the phosphorus-containing compounds form a stable phosphate passivation layer on the electrode surface, effectively inhibiting electrolyte decomposition and electrode material dissolution; the metal oxides enhance the mechanical strength and ion conductivity of the coating layer, mitigating the volume expansion and contraction of the electrode material during charging and discharging. With a mass ratio of 1:0.5-3, the optimal balance between the protective performance and ion transport performance of the coating layer is achieved.

[0082] In the preparation of the modified solution, a gradient stirring dispersion combined with nitrogen protection is adopted. Initial dispersion is carried out at low speed, followed by fine dispersion at high speed, which effectively prevents the agglomeration of modifier particles and ensures the uniformity and stability of the modified solution. At the same time, impurity particles are further removed by membrane filtration, avoiding defects in the subsequent coating layer and improving the coating quality. The coating method of ultrasonic dispersion and mechanical stirring working together, combined with ultrasonic-stirring cycle operation, allows the modifier to be uniformly adsorbed and deposited on the substrate surface, forming a uniform and dense coating layer. Meanwhile, ultraviolet-assisted irradiation promotes the activation of modifier molecules, enhances the bonding force between the modifier and the substrate surface, and forms a firm bond between the coating layer and the substrate, further improving the cycle stability of the electrode material.

[0083] The post-processing technology is scientifically sound and reasonable. Step-by-step washing thoroughly removes residual impurities and solvents. Precisely controlled drying and calcination parameters prevent cracking of the coating intermediate and oxidation of the coating layer. High-temperature calcination causes crystallization of the coating layer, further improving its density and stability. Cooling in the furnace after calcination prevents coating layer detachment due to thermal stress, ensuring the structural integrity of the modified electrode material. An added modification verification step ensures the modification effect meets design requirements through multi-dimensional testing. Unqualified products can be reprocessed by adjusting parameters, improving the product yield. Furthermore, this preparation method is simple, highly controllable, energy-efficient, and cost-effective, making it suitable for large-scale industrial production. Surface-modified electrode materials prepared using this method exhibit excellent cycle stability in lithium-ion batteries. At a 1C charge-discharge rate, the capacity retention rate after 1000 cycles can reach over 85%, significantly better than traditional unmodified electrode materials. It also improves the battery's rate performance and safety, demonstrating broad application prospects.

[0084] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A method for preparing a surface-modified electrode material for a high cycle life lithium-ion battery, characterized in that: Includes the following steps: Step S1. Coat the pretreated electrode substrate with a modified liquid to obtain a coating intermediate; Step S2. The coating intermediate is calcined under a protective gas atmosphere to obtain a modified electrode material coated on the surface of the electrode substrate.

2. The preparation method according to claim 1, characterized in that, The modified liquid comprises a phosphorus-containing compound, a metal oxide, a dispersant, and a solvent; based on the total mass of the modified liquid, the mass fraction of the dispersant is 5-20%, and the mass fraction of the phosphorus-containing compound and the metal oxide is 0.5-5 wt%, wherein the mass ratio of the phosphorus-containing compound to the metal oxide is 1:0.5-3.

3. The preparation method according to claim 2, characterized in that, The phosphorus-containing compound is at least one of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, phosphorous acid, and pyrophosphoric acid; the metal oxide is at least one of Al2O3, TiO2, ZrO2, MgO, and LiPO3, and the particle size of the metal oxide is 10-100 nm.

4. The preparation method according to claim 2, characterized in that, The dispersant is at least one of polyvinylpyrrolidone, polyethylene glycol, and sodium dodecylbenzenesulfonate; the solvent is one or more of deionized water, ethanol, or N-methylpyrrolidone.

5. The preparation method according to claim 1, characterized in that, The coating conditions in step S1 are: irradiation at a temperature of 30-80℃ with 200-300nm ultraviolet light; wherein the irradiation power is 50-150W and the irradiation time is 30-90min.

6. The preparation method according to claim 1, characterized in that, The calcination conditions in step S2 are: calcining at 300-600℃ for 1-4 hours with a heating rate of 2-10℃ / min; The protective gas atmosphere is any one of nitrogen, argon, and helium.

7. The preparation method according to claim 1, characterized in that, In step 1, the purity of the electrode substrate is ≥99.5%, and the particle size is 1-10μm; The electrode substrate includes a positive electrode substrate and a negative electrode substrate.

8. The preparation method according to claim 7, characterized in that, The positive electrode substrate includes at least one of LiCoO2, LiFePO4, LiNi1 / 3Co1 / 3Mn1 / 3O2, LiNi0.8Co0.1Mn0.1O2, and LiMn2O4; The negative electrode substrate includes at least one of natural graphite, artificial graphite, hard carbon, soft carbon, and silicon-based materials.

9. The modified electrode material obtained by the preparation method according to any one of claims 1 to 8.

10. The modified electrode material according to claim 9, characterized in that, The thickness of the modified electrode material is 5-50 nm.

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