Method for preparing fast ionic conductor-coated lithium-rich manganese-based layered oxide and application thereof
By using a co-precipitation method guided by density functional theory and a high-temperature sintering preparation method, zirconium dioxide was precipitated by tantalum carbide-driven zirconium, which solved the problem of uneven LLZTO coating, achieved efficient lithium-ion transport and structural stability, and improved the cycle life and electrochemical performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 深圳市速方新能源科技有限公司
- Filing Date
- 2026-05-09
- Publication Date
- 2026-07-31
AI Technical Summary
In the existing technology, the traditional oxide preparation method lacks precise control over the ZrO2 modification process, resulting in uneven coating of the fast ion conductor LLZTO, which cannot completely solve the problems of voltage decay and lithium dendrite growth in lithium-rich manganese-based base oxides.
The distribution characteristics of zirconium and lanthanum were guided by density functional theory calculations. A combination of co-precipitation and high-temperature sintering was used, with tantalum carbide as an inducer to drive zirconium to precipitate in the form of zirconium dioxide at the grain boundaries of the coating layer, forming a composite structure and optimizing the uniformity and performance of the coating layer.
The coating achieves uniformity and density, improves the mechanical strength and lithium-ion transport performance of the material, significantly inhibits the migration of transition metal ions and oxygen release, and improves the cycle life and electrochemical performance of lithium-ion batteries.
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Figure CN122482503A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery material technology, and more specifically, it relates to the preparation method and application of fast ion conductor coated lithium-rich manganese-based crystalline oxide. Background Technology
[0002] The general chemical formula for lithium-rich manganese-based layered oxide cathode materials is: M typically represents one or more transition metal ions, such as Ni, Co, and Mn, with x ≤ 0.5 indicating excess lithium and manganese content. Due to its high specific capacity exceeding 250 mAh / g and low cost, it is a strong candidate for next-generation high-energy-density lithium-ion batteries. However, this material suffers from rapid capacity decay, significant voltage drop, oxygen release, and transition metal dissolution during cycling, severely limiting its commercial application.
[0003] In existing technologies, surface coating modification can partially improve performance. While traditional coatings such as Al₂O₃ or MgO can suppress interfacial side reactions, these materials have low ionic conductivity, which may hinder lithium-ion transport and lead to a decrease in rate performance. Fast ion conductors LLZTO (Li₂O₃) 6.5 La3Zr 1.5 Ta 0.5 O 12 It has a high ionic conductivity of approximately 0.6-0.8 mS / cm. -1 With its good chemical stability, LLZTO is expected to promote lithium-ion migration while protecting the interface. However, the high electronic conductivity of pure LLZTO coatings easily leads to lithium dendrite growth and interface degradation, and its voltage decay rate remains high, failing to completely solve the polarization problem.
[0004] Recent studies have shown that modifying LLZTO grain boundaries with zirconium dioxide (ZrO2) can effectively suppress electron leakage (the ZrO2 surface band gap reaches 3.47 eV, far higher than LLZTO's 2.69 eV) and improve mechanical strength. However, existing methods for preparing LLZTO-coated lithium-rich manganese-based materials are still imperfect, lacking precise control over the ZrO2 modification process, resulting in uneven coating layers and limited performance improvement. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a method and application for preparing lithium-rich manganese-based substrate oxides coated with fast ion conductors. This addresses the technical issue in the prior art where traditional oxide preparation methods lack control over the ZrO2 modification process, resulting in uneven coating layers and limited performance improvement.
[0006] The preparation method of fast ion conductor coated lithium-rich manganese-based layered oxide, the purpose and effect of its application are achieved by the following specific technical means: A method for preparing fast-ion conductor-coated lithium-rich manganese-based substrate oxides includes the following steps: S1: Density functional theory calculations were used to verify the distribution characteristics of zirconium and lanthanum in lithium-rich manganese-based matrix oxides, guiding zirconium dioxide modification and coating strategies. S2: Lithium-rich manganese-based matrix oxide precursors were prepared by co-precipitation and high-temperature sintering; S3: The LLZTO precursor solution is coated onto the surface of the precursor by impregnation or spraying. The LLZTO precursor solution contains tantalum carbide as an inducer for zirconium dioxide formation. Zirconium is precipitated in the form of zirconium dioxide through element substitution reaction in the subsequent sintering process. S4: Sintering at high temperature decomposes tantalum carbide, and tantalum replaces zirconium in the LLZTO lattice, driving zirconium to precipitate as zirconium dioxide at the grain boundaries of the cladding layer, forming a composite structure and obtaining the final oxide.
[0007] In a preferred embodiment, in step S1, density functional theory is used to calculate and analyze the relative energies of zirconium and lanthanum between different layers to determine that zirconium tends to be doped near the surface and lanthanum tends to be enriched on the surface, thereby optimizing the distribution of zirconium dioxide.
[0008] In a preferred embodiment, in step S2, the preparation of the lithium-rich manganese-based matrix oxide precursor includes: co-precipitating nickel salt, cobalt salt, and aluminum salt in a molar ratio of Ni:Co:Al=0.8:0.15:0.05, then ball-milling with lithium salt and flux KCl, pre-calcining at 500°C for 6 hours, main calcining at 800°C for 15 hours, and annealing at 600°C for 3 hours.
[0009] In a preferred embodiment, lithium salt, lanthanum salt, and zirconium salt are dissolved in a mixed solvent, and a complexing agent is added to form solution A; tantalum salt is dissolved in an organic solvent to form a solution, preferably with tantalum carbide added as an inducer B for zirconium dioxide formation; solution B is added dropwise to solution A under low temperature conditions, the pH is adjusted, and the solution is aged to obtain LLZTO precursor sol.
[0010] In a preferred embodiment, the lithium salt is one or a mixture of lithium nitrate, lithium carbonate, and lithium hydroxide; the lanthanum salt is one or a mixture of lanthanum nitrate and lanthanum chloride; the zirconium salt is one or a mixture of zirconium oxychloride and zirconium nitrate; the tantalum salt is one or a mixture of tantalum ethoxide and tantalum chloride; the mixed solvent is a mixture of deionized water and anhydrous ethanol in a volume ratio of 1:1; the complexing agent is citric acid, and the molar ratio of citric acid to total metal ions is 1.5-2.0:1; the amount of lithium salt fed is 10%-20% excess relative to the stoichiometric ratio of LLZTO to compensate for lithium volatilization during the heat treatment process; the preparation of solution B is carried out in an inert atmosphere glove box.
[0011] In a preferred embodiment, in step S3, the molar ratio of lithium, lanthanum, zirconium, and tantalum in the LLZTO precursor solution is 7:3:2:0.1-0.5, and tantalum carbide is added so that the final zirconium dioxide content accounts for 1-10 wt% of the coating layer. The solvent is ethanol or deionized water; the impregnation time is 10-60 min, and the spray rate is 0.1-1.0 mL / min.
[0012] In a preferred embodiment, lithium-rich manganese-based basal oxide powder is pretreated and dispersed in a solvent to obtain a suspension; LLZTO precursor sol is added dropwise to the suspension under stirring, and after heating reaction and dispersion treatment, a coated precursor is formed; The pretreatment of lithium-rich manganese-based basal oxide powder includes vacuum drying at 120℃ for 12 hours; the dispersion process adopts ultrasonic dispersion or ball milling dispersion, with ultrasonic power of 200-300W and ball milling speed of 200-400rpm; the time for adding LLZTO precursor sol is controlled within 1 hour, and the reaction temperature is 60-80℃.
[0013] In a preferred embodiment, in step S4, the sintering process is heated to 600-800℃ at a rate of 1-5℃ / min and held for 2-6 hours to achieve LLZTO crystallization and element diffusion; The coating precursor was subjected to preliminary drying, pre-calcination and annealing, and then cooled to obtain the lithium-rich manganese-based base oxide coated with the fast ion conductor. Preliminary drying includes rotary evaporation and vacuum drying at temperatures of 60℃ and 80℃, respectively. Pre-firing is carried out in an air atmosphere, with the temperature increased at 2℃ / min to 350-450℃ and held for 4-6 hours. Annealing is carried out in an oxygen or air atmosphere, with the temperature increased at 3-5℃ / min to 800-950℃ and held for 6-10 hours. After cooling to room temperature, a lithium-rich manganese-based matrix oxide composite material coated with LLZTO (a fast ion conductor) modified with zirconium dioxide is obtained. The sintering process drives the decomposition of tantalum carbide, which replaces zirconium in the LLZTO lattice, causing zirconium to precipitate as zirconium dioxide, forming a coating layer with a thickness of 5-50 nm and a coating amount of 1-10 wt%.
[0014] In a preferred embodiment, the oxide material comprises a lithium-rich manganese-based basal oxide core and a zirconium dioxide-modified LLZTO coating layer, wherein the core has the chemical formula Li[Li] x Mn 2x M 1-x O2, where M is one or more of Ni, Co, and Mn, x≤0.5, the thickness of the LLZTO coating layer is 10-50nm, and the coating amount is 1-10wt%.
[0015] Application of a fast ion conductor coated lithium-rich manganese-based layered oxide preparation method, wherein the oxide is used as the positive electrode of a lithium-ion battery, and under a high voltage of 2.0-4.8V, the capacity retention rate is ≥95% after 200 cycles, the voltage drop is ≤1mV / cycle, and the 1C discharge specific capacity is ≥260mAh / g; The lithium-ion battery prepared from the positive electrode material has a voltage drop of 0.95mV / cycle in the first 200 cycles and a 1C capacity of 264mAh / g.
[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Zirconia-modified fast ion conductor LLZTO-coated lithium-rich manganese-based layered oxide materials optimize the interfacial electronic structure and lithium-ion transport path by constructing a surface fast ion conductor network and introducing near-surface Zr / Ta element doping. This effectively suppresses transition metal ion migration, oxygen release, and structural phase transition, thereby improving the structural stability and electrolyte corrosion resistance of lithium-rich layered cathodes. It can achieve stable performance with high capacity and low voltage drop, and solves the ion blockage problem of traditional coating layers.
[0017] 2. A solution coating method combined with heat treatment is adopted. In-situ precipitation of ZrO2 is achieved by adding tantalum carbide. The coating thickness can be precisely controlled within 10-50nm with good uniformity. The method has high repeatability, does not require complex equipment, and is conducive to large-scale production. At the same time, the dense porosity of the coating layer (2-5%) enhances the mechanical strength and crack resistance of the material.
[0018] 3. The lithium-ion battery prepared by coating lithium-rich manganese-based morphological oxide material with LLZTO (a fast ion conductor modified with zirconium dioxide) has a discharge specific capacity of no less than 260 mAh / g at 1C rate. After 200 cycles, the capacity retention rate is as high as 99% or more, and the voltage decay rate is only 0.9 mV / cycle. It has better electrochemical performance than traditional lithium-rich manganese-based cathode materials, thus improving the cycle life and efficiency of lithium-ion batteries. Attached Figure Description
[0019] Figure 1 SEM image of the fast ion conductor coated with lithium-rich manganese-based matrix oxide in this invention; Figure 2 Cyclic stability curves of fast ion conductors coated with lithium-rich manganese-based base oxides in this invention; Figure 3 Voltage drop decay curve of fast ion conductor coated with lithium-rich manganese base oxide in this invention; Figure 4 The flowchart of the preparation method of fast ion conductor coated with lithium-rich manganese base oxide in this invention. Detailed Implementation
[0020] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the technical solutions of the present invention, but should not be used to limit the scope of protection of the present invention.
[0021] Example 1:
[0022] As attached Figures 1 to 4 As shown: This invention provides a method for preparing a fast-ion conductor coated with a lithium-rich manganese-based substrate oxide, the chemical formula of which is Li{Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 The ZrO2 nanoparticles are distributed at the LLZTO grain boundaries, with a coating amount of 3 wt% and a thickness of approximately 10 nm. This composite material significantly improves the interfacial ionic conductivity and electronic insulation.
[0023] The preparation steps for fast ion conductor-coated lithium-rich manganese-based substrate oxides are as follows: 1. Weigh out excess 15% of LiNO3, La(NO3)3·6H2O, and ZrOCl2·8H2O, dissolve them in 20 mL of a deionized water / ethanol mixture (1:1), add citric acid (molar ratio 1.8:1), and stir to obtain solution A. In an inert atmosphere glove box, dissolve tantalum ethoxide (Ta(OC2H5)5) in anhydrous ethanol to form solution B (add tantalum carbide (TaC) as a ZrO2 source, corresponding to a final ZrO2 content of 3wt%). Under ice-water bath conditions (0-5℃), slowly add solution B dropwise to solution A, controlling the dropping rate to avoid local precipitation. Then adjust the pH to 3.5 and age for 3 hours to obtain a ZrO2-modified LLZTO precursor sol. This step ensures the homogeneity of the sol, laying the foundation for in-situ precipitation of ZrO2 during subsequent sintering.
[0024] 2. 5g of lithium-rich manganese-based powder (dried at 120℃ for 12 hours) was dispersed in 30mL of ethanol and sonicated (300W power); LLZTO sol was added dropwise under stirring (completed within 1 hour), and the mixture was reacted in an oil bath at 60℃ for 5 hours. Mid-term ultrasonic dispersion for 3 minutes was then performed to break potential agglomeration and form the coated precursor. This process optimized the interfacial bonding between the coating layer and the core.
[0025] 3. The coating precursor was removed by rotary evaporation at 60℃ to remove the solvent, followed by vacuum drying at 80℃ for 12 hours to obtain a dry powder. Under air atmosphere, it was heated to 400℃ at a heating rate of 2℃ / min and held for 5 hours to remove organic residues and initially stabilize the coating structure. Under oxygen atmosphere, it was heated to 900℃ at a heating rate of 4℃ / min and held for 8 hours to promote LLZTO crystallization and in-situ precipitation of ZrO2 (tantalum carbide decomposition drives tantalum substitution of zirconium, with zirconium distributed as ZrO2 at grain boundaries). After furnace cooling to room temperature, it was passed through a 400-mesh sieve to obtain the final composite material. This heat treatment process ensured the compactness (porosity ≤5%) and chemical stability of the coating layer.
[0026] The fast-ion coated lithium-rich manganese-based base oxide prepared in this manner can be used to prepare cathode materials for lithium-ion batteries.
[0027] Example 2:
[0028] This embodiment discloses a lithium-rich manganese-based substrate oxide composite material coated with a fast ion conductor, wherein the core chemical formula is Li{Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 The O2 and LLZTO coating layer has a coating amount of 5wt% and a thickness of approximately 25nm.
[0029] The preparation steps of the fast ion conductor coated with lithium-rich manganese-based substrate oxide are as follows: 1. Weigh out excess 15% of LiNO3, La(NO3)3·6H2O, and ZrOCl2·8H2O, dissolve them in 20 mL of a deionized water / ethanol mixture (1:1), add citric acid (molar ratio 1.8:1), and stir to obtain solution A. In an inert atmosphere glove box, dissolve tantalum ethoxide (Ta(OC2H5)5) in anhydrous ethanol to form solution B (add tantalum carbide (TaC) as a ZrO2 source, corresponding to a final ZrO2 content of 3wt%). Under ice-water bath conditions (0-5℃), slowly add solution B dropwise to solution A, controlling the dropping rate to avoid local precipitation. Then adjust the pH to 3.8 and age for 4 hours to obtain a ZrO2-modified LLZTO precursor sol. This step ensures the homogeneity of the sol, laying the foundation for in-situ precipitation of ZrO2 during subsequent sintering.
[0030] 2. 5g of lithium-rich manganese-based powder (dried at 120℃ for 12 hours) was dispersed in 30mL of ethanol and sonicated (300W power); LLZTO sol was added dropwise under stirring (completed within 1.5 hours), and the mixture was reacted in an oil bath at 70℃ for 5 hours. Mid-term ultrasonic dispersion for 3 minutes was then performed to break potential agglomeration and form the coated precursor. This process optimized the interfacial bonding between the coating layer and the core.
[0031] 3. The coating precursor was first removed by rotary evaporation at 60℃ to remove the solvent, and then vacuum dried at 80℃ for 12 hours to obtain a dry powder. Under air atmosphere, it was heated to 420℃ at a heating rate of 2℃ / min and held for 5.5 hours to remove organic residues and initially stabilize the coating structure. Under oxygen atmosphere, it was heated to 900℃ at a heating rate of 4℃ / min and held for 8 hours to promote LLZTO crystallization and in-situ precipitation of ZrO2 (tantalum carbide decomposition drives tantalum substitution of zirconium, with zirconium distributed as ZrO2 at grain boundaries). After furnace cooling to room temperature, it was passed through a 400-mesh sieve to obtain the final composite material. This heat treatment regime ensured the compactness (porosity ≤5%) and chemical stability of the coating layer.
[0032] The fast-ion coated lithium-rich manganese-based base oxide prepared in this manner can be used to prepare cathode materials for lithium-ion batteries.
[0033] Example 3:
[0034] This embodiment discloses a lithium-rich manganese-based substrate oxide composite material coated with a fast ion conductor, wherein the core chemical formula is Li{Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 The O2 and LLZTO coating layer has a coating amount of 10wt% and a thickness of approximately 50nm.
[0035] The preparation steps of the fast ion conductor coated with lithium-rich manganese-based substrate oxide are as follows: 1. Weigh out 20% excess LiNO3, La(NO3)3·6H2O, and ZrOCl2·8H2O, dissolve them in 20 mL of a deionized water / ethanol mixture (1:1), add citric acid (molar ratio 2.2:1), and stir to obtain solution A. In an inert atmosphere glove box, dissolve tantalum ethoxide (Ta(OC2H5)5) in anhydrous ethanol to form solution B (add tantalum carbide (TaC) as a ZrO2 source, corresponding to a final ZrO2 content of 10 wt%). Under ice-water bath conditions (0-5℃), slowly add solution B dropwise to solution A, controlling the dropping rate to avoid local precipitation. Then adjust the pH to 3.8 and age for 5 hours to obtain a ZrO2-modified LLZTO precursor sol. This step ensures the homogeneity of the sol, laying the foundation for in-situ precipitation of ZrO2 during subsequent sintering.
[0036] 2. 5g of lithium-rich manganese-based powder (dried at 120℃ for 12 hours) was dispersed in 40mL of ethanol and sonicated (300W power); LLZTO sol was added dropwise under stirring (completed within 1.5 hours), and the mixture was reacted in an oil bath at 70℃ for 5 hours. Mid-term ultrasonic dispersion for 3 minutes was then performed to break potential agglomeration and form the coated precursor. This process optimized the interfacial bonding between the coating layer and the core.
[0037] 3. The coating precursor was first removed by rotary evaporation at 60℃ to remove the solvent, and then vacuum dried at 80℃ for 12 hours to obtain a dry powder. Under air atmosphere, it was heated to 450℃ at a heating rate of 1.5℃ / min and held for 6 hours to remove organic residues and initially stabilize the coating structure. Under oxygen atmosphere, it was heated to 950℃ at a heating rate of 3℃ / min and held for 10 hours to promote LLZTO crystallization and in-situ precipitation of ZrO2 (tantalum carbide decomposition drives tantalum substitution of zirconium, with zirconium distributed as ZrO2 at grain boundaries). After furnace cooling to room temperature, it was passed through a 400-mesh sieve to obtain the final composite material. This heat treatment process ensured the compactness (porosity ≤5%) and chemical stability of the coating layer.
[0038] The fast-ion coated lithium-rich manganese-based base oxide prepared in this manner can be used to prepare cathode materials for lithium-ion batteries.
[0039] Experimental examples and electrochemical performance tests Fabrication and electrical performance testing of button cell half-cells: Lithium-ion button-type half-cells (CR2032 type) were assembled, and the electrochemical performance of the LLZTO-coated lithium-rich manganese-based basal oxide composite materials prepared in each example as positive electrode active materials was tested. The prepared electrode sheets were cut into 14 mm diameter circular sheets and used directly as working electrodes, with a lithium metal sheet as the counter electrode. Celgard 2500 was used as the separator, and the electrolyte was a 1 mol / L LiPF6 carbonate solution (solvent: ethylene carbonate EC / dimethyl carbonate DMC, volume ratio 1:1). Battery assembly was carried out in a glove box filled with high-purity argon gas, with water and oxygen concentrations both below 1 ppm. Charge-discharge tests were conducted using a Newway battery testing system, with a test voltage range of 2.0-4.8 V and a rate of 1C. The morphology and structure of the zirconium dioxide-modified fast ion conductor LLZTO-coated lithium-rich manganese-based basal oxide composite material prepared in Example 1 were observed using scanning electron microscopy (SEM). SEM results showed that the LLZTO coating layer uniformly covered the surface of the lithium-rich manganese-based particles without obvious cracks or peeling, indicating that the solution coating process effectively achieved the construction of a dense and continuous coating layer. The composite material obtained in Example 1 was used to prepare a positive electrode sheet and assembled into a battery. The specific preparation method of the positive electrode sheet was as follows: LLZTO-coated lithium-rich manganese-based morphological oxide composite material was used as the active material, acetylene black was used as the conductive agent, and polyvinylidene fluoride (PVDF) was used as the binder. The materials were weighed in a mortar at a mass ratio of 8:1:1 and uniformly ground and mixed for 30 minutes. Then, an appropriate amount of N-methylpyrrolidone (NMP) was added as a solvent, and grinding was continued for another 30 minutes to obtain a uniform slurry. The slurry was coated onto an aluminum foil current collector using an automatic coating machine, controlling the coating thickness to 100 μm, and then dried in a vacuum drying oven at 120℃ for 12 hours. The dried electrode sheet was rolled to compaction using an automatic roller press and finally punched into circular electrode sheets with a diameter of 14 mm to obtain the positive electrode sheet. Electrochemical performance tests of the battery showed that LLZTO coating significantly improved the cycle stability and voltage stability of the material. At 1C rate, the initial discharge specific capacity reached 265 mAh / g, and after 200 cycles, the discharge specific capacity remained at 264 mAh / g, with a capacity retention rate as high as 99%. Simultaneously, voltage drop tests showed that within the 2.0-4.8V voltage range, after 200 cycles, the average voltage decay rate was only 0.95 mV / cycle, far lower than that of the uncoated material (typically exceeding 1.0 mV / cycle). Cycling performance curves showed that the capacity decay of the coated material was slow, and the coulombic efficiency remained above 99%, demonstrating excellent reversibility. The fast-ion conductor LLZTO-coated lithium-rich manganese-based layered oxide composite material prepared in this invention significantly suppressed oxygen release and phase transitions during cycling and improved interfacial stability through the synergistic effect of surface coating and near-surface doping.Its porous core-shell structure not only provides a high specific surface area to enhance reactivity, but also optimizes the lithium-ion transport path through a fast-ion conductor layer, thus achieving a balance between high capacity, low voltage drop, and long cycle life. This material offers a new approach for the development of cathode materials for high-energy-density lithium-ion batteries and has significant prospects for industrial application.
[0040] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.
Claims
1. A method for preparing lithium-rich manganese-based substrate oxide coated with fast ion conductors, characterized in that: It includes the following steps: S1: Density functional theory calculations were used to verify the distribution characteristics of zirconium and lanthanum in lithium-rich manganese-based matrix oxides, guiding zirconium dioxide modification and coating strategies. S2: Lithium-rich manganese-based matrix oxide precursors were prepared by co-precipitation and high-temperature sintering; S3: The LLZTO precursor solution is coated onto the surface of the precursor by impregnation or spraying. The LLZTO precursor solution contains tantalum carbide as an inducer for zirconium dioxide formation. Zirconium is precipitated in the form of zirconium dioxide through element substitution reaction in the subsequent sintering process. S4: Sintering at high temperature decomposes tantalum carbide, and tantalum replaces zirconium in the LLZTO lattice, driving zirconium to precipitate as zirconium dioxide at the grain boundaries of the cladding layer, forming a composite structure and obtaining the final oxide.
2. The method for preparing a fast-ion conductor coated with a lithium-rich manganese-based substrate oxide according to claim 1, characterized in that: In step S1, density functional theory is used to calculate and analyze the relative energies of zirconium and lanthanum between different layers, determining that zirconium tends to be doped near the surface and lanthanum tends to be enriched on the surface, thereby optimizing the distribution of zirconium dioxide.
3. The method for preparing a fast-ion conductor coated with a lithium-rich manganese-based substrate oxide according to claim 1, characterized in that: In step S2, the preparation of the lithium-rich manganese-based basal oxide precursor includes: co-precipitating nickel salt, cobalt salt, and aluminum salt in a molar ratio of Ni:Co:Al=0.8:0.15:0.05, then ball-milling with lithium salt and flux KCl, pre-calcining at 500℃ for 6h, main calcining at 800℃ for 15h, and annealing at 600℃ for 3h.
4. The method for preparing fast ion conductor coated lithium-rich manganese-based substrate oxide according to claim 3, characterized in that: Lithium salt, lanthanum salt, and zirconium salt are dissolved in a mixed solvent, and a complexing agent is added to form solution A; tantalum salt is dissolved in an organic solvent to form a solution, preferably with tantalum carbide added as an inducer B for zirconium dioxide formation; solution B is added dropwise to solution A under low temperature conditions, the pH is adjusted, and the solution is aged to obtain LLZTO precursor sol.
5. The method for preparing a fast-ion conductor coated with a lithium-rich manganese-based substrate oxide according to claim 4, characterized in that: The lithium salt is one or a mixture of lithium nitrate, lithium carbonate, and lithium hydroxide; the lanthanum salt is one or a mixture of lanthanum nitrate and lanthanum chloride; the zirconium salt is one or a mixture of zirconium oxychloride and zirconium nitrate; the tantalum salt is one or a mixture of tantalum ethoxide and tantalum chloride; the mixed solvent is a mixture of deionized water and anhydrous ethanol in a volume ratio of 1:1; the complexing agent is citric acid, and the molar ratio of citric acid to total metal ions is 1.5-2.0:1; the amount of lithium salt fed is 10%-20% in excess relative to the stoichiometric ratio of LLZTO to compensate for lithium volatilization during the heat treatment process; the preparation of solution B is carried out in an inert atmosphere glove box.
6. The method for preparing a fast-ion conductor coated with a lithium-rich manganese-based substrate oxide according to claim 1, characterized in that: In step S3, the molar ratio of lithium, lanthanum, zirconium, and tantalum in the LLZTO precursor solution is 7:3:2:0.1-0.5, and tantalum carbide is added to make the final zirconium dioxide content account for 1-10 wt% of the coating layer. The solvent is ethanol or deionized water. The impregnation time is 10-60 min, and the spray rate is 0.1-1.0 mL / min.
7. The method for preparing a fast-ion conductor coated with a lithium-rich manganese-based substrate oxide according to claim 6, characterized in that: After pretreatment, lithium-rich manganese-based basal oxide powder is dispersed in a solvent to obtain a suspension; LLZTO precursor sol was added dropwise to the suspension under stirring, and after heating and dispersion treatment, a coated precursor was formed. The pretreatment of lithium-rich manganese-based basal oxide powder includes vacuum drying at 120℃ for 12 hours; the dispersion process adopts ultrasonic dispersion or ball milling dispersion, with ultrasonic power of 200-300W and ball milling speed of 200-400rpm; the time for adding LLZTO precursor sol is controlled within 1 hour, and the reaction temperature is 60-80℃.
8. The method for preparing a fast-ion conductor coated with a lithium-rich manganese-based substrate oxide according to claim 1, characterized in that: In step S4, the sintering process involves heating to 600-800℃ at a rate of 1-5℃ / min and holding for 2-6 hours to achieve LLZTO crystallization and element diffusion. The coating precursor was subjected to preliminary drying, pre-calcination and annealing, and then cooled to obtain the lithium-rich manganese-based base oxide coated with the fast ion conductor. Preliminary drying includes rotary evaporation and vacuum drying at temperatures of 60℃ and 80℃, respectively. Pre-firing is carried out in an air atmosphere, with the temperature increased at 2℃ / min to 350-450℃ and held for 4-6 hours. Annealing is carried out in an oxygen or air atmosphere, with the temperature increased at 3-5℃ / min to 800-950℃ and held for 6-10 hours. After cooling to room temperature, a lithium-rich manganese-based matrix oxide composite material coated with LLZTO (a fast ion conductor) modified with zirconium dioxide is obtained. The sintering process drives the decomposition of tantalum carbide, which replaces zirconium in the LLZTO lattice, causing zirconium to precipitate as zirconium dioxide, forming a coating layer with a thickness of 5-50 nm and a coating amount of 1-10 wt%.
9. The method for preparing a fast-ion conductor coated with a lithium-rich manganese-based substrate oxide according to claim 1, characterized in that: The oxide material consists of a lithium-rich manganese-based lattice oxide core and a zirconium dioxide-modified LLZTO coating layer. The core has the chemical formula Li[Li] x Mn 2x M 1-x O2, where M is one or more of Ni, Co, and Mn, x≤0.5, the thickness of the LLZTO coating layer is 10-50nm, and the coating amount is 1-10wt%.
10. An application of the method for preparing a fast-ion conductor coated with a lithium-rich manganese-based substrate oxide as described in claim 1, characterized in that, The oxide is used in the positive electrode of lithium-ion batteries. Under a high voltage of 2.0-4.8V, the capacity retention rate is ≥95% after 200 cycles, the voltage drop is ≤1mV / cycle, and the 1C discharge specific capacity is ≥260mAh / g. The lithium-ion battery prepared from the positive electrode material has a voltage drop of 0.95mV / cycle in the first 200 cycles and a 1C capacity of 264mAh / g.