A lithium-rich manganese-based cathode material with a gradient dual-channel ion transport network and its preparation method

Abstract

This invention relates to the field of lithium-ion battery technology, and in particular to a lithium-rich manganese-based cathode material with a gradient dual-channel ion transport network and its preparation method. The cathode material has the general chemical formula Li[LiaMnbNicCodM1-a-b-c-d]O2-eFe. Its core feature lies in the construction of a radial "double-shell-core" gradient doping structure: the outermost layer is enriched with high-valence Zr and W elements to suppress surface oxygen evolution, the middle layer is enriched with B elements to stabilize the crystal lattice, and the core maintains a low doping concentration. Internally, a rapid lithium-ion diffusion channel composed of grain boundary oxygen vacancies and an in-situ carbon nanofiber interwoven electron transport network are simultaneously constructed, forming a dual continuous ion / electron transport system. The surface is loaded with an adaptive interface layer containing LiF, Li3PO4, and a boron-containing organic-inorganic hybrid polymer, which can dynamically capture active oxygen and repair interface defects. The preparation method of this invention achieves the above-mentioned structural control through stepwise co-precipitation, spray drying pore-forming, and multi-stage calcination processes.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a lithium-rich manganese-based cathode material with a gradient dual-channel ion transport network and its preparation method. Background Technology

[0002] In recent years, with the urgent need for high-energy-density batteries in electric vehicles, mobile electronic devices, and large-scale energy storage systems, lithium-rich manganese-based layered oxides (... , Due to its unique anionic redox mechanism, lithium-rich materials (such as lithium metal anodes) can provide a specific capacity exceeding 250 mAh / g, making them ideal cathode materials for breaking through the energy density bottleneck of traditional lithium-ion batteries. However, lithium-rich materials still face multiple challenges in practical applications: First, irreversible loss of lattice oxygen during high-voltage charging (>4.5V) leads to low initial coulombic efficiency and capacity decay; second, the migration of transition metal ions triggers the transformation of the layered structure to the spinel phase, causing significant voltage decay; third, interfacial side reactions and the accumulation of interfacial impedance reduce battery kinetic performance. Especially when matched with lithium metal anodes to construct high-energy-density batteries, the high operating voltage accelerates the oxidative decomposition of the electrolyte, making the interfacial stability problem even more prominent.

[0003] In existing technologies, researchers mainly improve the performance of lithium-rich materials through strategies such as bulk doping, surface coating, and morphology control. For example, recently, gradient-doped lithium-rich manganese-based materials have been reported, which effectively suppress surface oxygen evolution and improve structural stability through a gradient distribution of elemental concentration from the surface to the interior. However, these materials still face the problem of insufficient ion / electron transport kinetics during high-rate charge-discharge processes, especially under high areal loading conditions. At the same time, when matched with a lithium metal anode, the by-reaction products of lithium-rich materials under high voltage migrate to the anode, exacerbating lithium dendrite growth and reducing battery cycle life.

[0004] Furthermore, in high-energy-density lithium metal batteries, the oxygen redox reaction of lithium-rich materials and the lithium deposition / stripping process of the lithium metal anode jointly determine battery life. Traditional cathode material designs often neglect compatibility with lithium metal anodes, leading to an underestimation of the irreversible loss of active lithium during battery cycling. Therefore, developing a lithium-rich manganese-based cathode material that can maintain high specific capacity while being well-matched with lithium metal anodes is crucial for achieving lithium metal batteries with energy densities exceeding 600 Wh / kg. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium-rich manganese-based cathode material with a gradient dual-channel ion transport network. Through innovative gradient dual-channel structure design, the bulk phase and interface properties of the material are synergistically optimized, solving key problems such as oxygen evolution, voltage decay, and interface instability faced by lithium-rich materials in high-energy-density lithium metal batteries.

[0006] The core innovations of this invention are: 1) constructing a "double-shell-core" structure with a gradient distribution of elemental concentration from the material surface to the interior, forming a stress buffer and oxygen framework stabilizing layer; 2) designing a dual continuous ion / electron transport network to construct a fast lithium-ion diffusion channel and a highly conductive network; 3) introducing an adaptive interface layer to form a stable artificial CEI film in situ, maintaining interface stability under high voltage.

[0007] According to a first aspect of the present invention, a lithium-rich manganese-based cathode material with a gradient dual-channel ion transport network is provided, wherein the general chemical formula of the cathode material is Li[LiaMnbNicCodM1-abcd]O2-eFe, wherein 0.15≤a≤0.25, 0.45≤b≤0.65, 0.10≤c≤0.25, 0.05≤d≤0.15, and 0.02≤e≤0.10; M is a gradient doping element selected from one or more of the group consisting of Zr, W, B, F, and S; wherein the gradient doping element M has a double-shell-core structure in the radial distribution of the material particles: in the outermost layer of the particles The cathode material is enriched with high-valence elements Zr⁴⁺ and W⁶⁺ (thickness 30-50 nm) at a concentration of 0.05-0.08; B element is enriched in the intermediate layer (thickness 100-150 nm) at a concentration of 0.02-0.04; the M element concentration is reduced to 0.005-0.01 in the core region; a dual continuous ion / electron transport network is constructed inside the cathode material, including: lithium-ion fast diffusion channels composed of grain boundary oxygen vacancies, and electron transport channels composed of an in-situ carbon nanofiber interwoven network; an adaptive interface layer with a thickness of 8-15 nm is loaded on the surface of the cathode material, the adaptive interface layer being composed of LiF, It is composed of boron-containing organic-inorganic hybrid polymers, wherein the boron-containing organic-inorganic hybrid polymers contain BO, BN and BF bonds, which can capture reactive oxygen species and inhibit interfacial side reactions under high voltage.

[0008] In a preferred embodiment, the lithium-rich manganese-based cathode material particles are micron-sized spherical secondary aggregates assembled from primary nanoparticles (200-500 nm) with a diameter of 3-6 μm; the specific surface area is 5-8 m² / g; in the XRD pattern, the I003 / I104 intensity ratio is 1.4-1.9, and the (006) / (012) and (018) / (110) crystal planes are clearly split; the Raman spectrum shows obvious broadening characteristic peaks in the 480-520 cm⁻¹ region, indicating the existence of locally ordered nanodomain structures.

[0009] In another preferred embodiment, in the bicontinuous ion / electron transport network, the concentration of oxygen vacancies at grain boundaries decreases in a gradient from the surface to the core, with a surface concentration of 10¹⁹-10²⁰ cm⁻³ and a core concentration of 10¹⁷-10¹⁸ cm⁻³; the in-situ carbon nanofiber network has a carbon content of 1.5-3.0 wt%, a fiber diameter of 20-50 nm, and a length of 0.5-2 μm, interwoven to form a three-dimensional conductive network.

[0010] In yet another preferred embodiment, LiF in the adaptive interface layer, The mass ratio of the boron-containing organic-inorganic hybrid polymer is (30-40):(20-30):(30-50); the boron-containing organic-inorganic hybrid polymer is prepared by reacting trimethoxysilylphenylboronic acid ester with fluorinated amine compounds, and the molecule contains Si-OB, BN and BF dynamic covalent bonds, which can be reversibly broken and reconstructed during charging and discharging to achieve adaptive adjustment of the interface.

[0011] According to a second aspect of the present invention, a method for preparing the above-mentioned lithium-rich manganese-based cathode material is provided, the method comprising the following steps: S1: Preparation of gradient element distribution precursor: Manganese salt, nickel salt, cobalt salt and gradient doped element salt are dissolved in proportion, and the precipitant flow rate and reaction temperature are controlled by stepwise co-precipitation method to achieve a gradient distribution of element concentration in the radial direction of the particles, and obtain a double shell-core structure precursor. S2: Constructing a dual continuous transport network: The precursor is mixed with a carbon-containing precursor and a pore-forming agent, and microspheres are formed by spray drying. Then, the mixture is heat-treated under a protective atmosphere to form an in-situ carbon nanofiber network and an oxygen vacancy gradient distribution. S3: Lithification and fluorine doping: The product obtained in step S2 is mixed with a lithium source and a fluorine source, and then calcined in multiple stages under an oxygen atmosphere to achieve lithiation and fluorine doping. S4: Constructing an adaptive interface layer: Disperse the material obtained in step S3 in a solution containing fluorine, phosphorus, and boron precursors, and form an adaptive interface layer in situ on the material surface through vapor deposition and sol-gel synergistic process.

[0012] According to a third aspect of the present invention, a lithium metal battery is provided, comprising a positive electrode, an electrolyte, and a lithium metal negative electrode, wherein the positive electrode comprises the aforementioned lithium-rich manganese-based positive electrode material, and the electrolyte is a high-concentration ether electrolyte or a solid electrolyte.

[0013] The technical effects and advantages of this invention are as follows: This invention effectively improves the specific capacity and initial coulombic efficiency of the material through the synergistic effect of gradient doping structure, dual continuous ion / electron transport network and adaptive interface layer, significantly enhances long-cycle stability and rate performance, suppresses structural phase transition and voltage decay under high voltage, improves interfacial compatibility with lithium metal anode, and enhances battery safety. Attached Figure Description

[0014] Figure 1 This is a structural diagram of the lithium-rich manganese-based cathode material of the present invention; Figure 2 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0015] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0016] Example 1: Fluorine-boron co-doped lithium-rich manganese-based cathode material with gradient dual-channel network S1: Preparation of gradient element distribution precursor: ... , , Dissolve in 800 mL of deionized water to form a main metal salt solution A. Prepare aqueous solutions B of ZrO(NO3)2 (0.06 mol) and Na2WO4 (0.04 mol), and aqueous solution C of H3BO3 (0.08 mol). Simultaneously prepare a mixed precipitant D containing NaOH (2.5 mol / L) and NH4HCO3 (1.0 mol / L). Under nitrogen protection, pump solution A into the reactor at a flow rate of 12 mL / min, and simultaneously add precipitant D at a flow rate of 8 mL / min. Control the pH at 10.5 ± 0.2, the temperature at 55 °C, and the stirring speed at 300 rpm. React for 1 hour to obtain the core precipitate. Next, mix solution B with the remaining portion of A and pump into the reactor at a flow rate of 10 mL / min. Simultaneously adjust the flow rate of precipitant D to 15 mL / min, raise the pH to 11.2 ± 0.2, raise the temperature to 60 °C, and continue the reaction for 1.5 hours to form the intermediate layer. Finally, solution C was mixed with the remaining portion of A and pumped in at a flow rate of 8 mL / min. The flow rate of precipitant D was increased to 20 mL / min, the pH was adjusted to 11.8 ± 0.2, and the temperature was maintained at 60 °C for 1.5 hours to form the outer shell layer. The product was washed and vacuum dried at 60 °C for 12 hours to obtain a precursor powder with a gradient elemental distribution. EDS line scan analysis confirmed that the concentrations of Zr and W elements were highest in the outer shell layer (30-50 nm) (0.07) and decreased rapidly inwards; the concentration of B element reached a peak concentration (0.03) in the middle layer (100-150 nm); and the concentration of doped elements in the core region decreased to 0.007.

[0017] S2: Construction of a dual continuous transport network: 10g of the precursor obtained in step S1, 1.5g of polyacrylonitrile (PAN, as a carbon precursor), and 0.8g of citric acid (as a pore-forming and complexing agent) were dissolved in 60mL of N,N-dimethylformamide (DMF) and stirred at 60℃ for 4 hours to form a homogeneous slurry. The slurry was atomized and dried using a spray dryer (inlet temperature 220℃, outlet temperature 95℃, peristaltic pump flow rate 8mL / min) to obtain microsphere powder. The powder was pretreated in an argon atmosphere at 350℃ for 2 hours (to eliminate the volatilization of organic matter), then heated to 750℃ at 1℃ / min and held for 3 hours (to form a carbon nanofiber network), and then naturally cooled to room temperature. TEM and EELS characterization revealed that a three-dimensional conductive network composed of in-situ grown carbon nanofibers (30-45 nm in diameter) was formed inside the material, with a carbon content of 2.3 wt%. At the same time, the oxygen vacancy concentration in the grain boundary region showed a gradient distribution, with the surface concentration (2.5 × 10¹⁹ cm⁻³) being significantly higher than that in the core (3.8 × 10¹⁷ cm⁻³), providing a rapid diffusion channel for lithium ions.

[0018] S3: Lithification and Fluorine Doping: 8g of the product from step S2 was combined with... 0.45 g of NH4F was ball-milled thoroughly for 4 hours. The mixture was then placed in an alumina crucible and calcined in three stages under an oxygen flow (200 mL / min): the first stage was held at 400 °C for 2 hours (to remove residual organic matter), the second stage was held at 750 °C for 4 hours (for initial lithiation), and the third stage was held at 900 °C for 10 hours (to complete crystal growth and fluorine doping), with a heating rate of 3 °C / min for all stages. After natural cooling, a gray-black powder was obtained and named GDLMO-1. ICP-OES analysis determined its composition to be Li[Li0.20Mn0.58Ni0.15Co0.07Zr0.025W0.015B0.02]O1.95F0.05; SEM showed that the particles were spherical secondary aggregates (4-5 μm in diameter), assembled from primary particles of 200-400 nm; the BET specific surface area was 6.8 m² / g.

[0019] S4: Construction of the adaptive interface layer: 5g of GDLMO-1 powder was placed in a CVD reactor, and fluorine-containing gas (C2F6, 50mL / min) and phosphorus-containing gas (PF3, 10mL / min) were introduced. The reaction was carried out at 200℃ for 2 hours to form a LiF and Li3PO4 precursor layer. Subsequently, the powder was dispersed in 50mL of ethanol, and 0.35g of boron-containing precursor (prepared by reacting 3-aminopropyltriethoxysilane and phenylboronic acid at a molar ratio of 1:1.2 at 60℃ for 4 hours) was added, and the mixture was stirred at 60℃ for 12 hours. After washing and drying at 80℃, the product was heat-treated at 250℃ under an argon atmosphere for 2 hours to obtain the final product GDLMO-2, which has a 12nm thick adaptive interface layer on its surface, wherein the mass ratio of LiF, Li3PO4 and boron-containing organic-inorganic hybrid polymer is 35:25:40.

[0020] Battery assembly and testing: GDLMO-2 cathode material, conductive carbon black SuperP, and binder PVDF were mixed at a mass ratio of 80:10:10, and a slurry was prepared using N-methylpyrrolidone (NMP) as a solvent. The slurry was coated onto aluminum foil and vacuum dried at 110°C for 12 hours to obtain a cathode sheet (area loading of approximately 4.5 mAh / cm²). A CR2032 coin cell was assembled using 1.0 M LiTFSI and 0.2 M LiPO2F2 in DME / DOL (1:1, v / v) as the electrolyte, a 50 μm thick lithium metal foil as the anode, and Celgard 2400 as the separator.

[0021] Electrochemical tests were conducted at 25°C: For the first 0.1C (1C=250mA / g) charge-discharge cycle (2.0-4.8V), the initial discharge specific capacity reached 292.5mAh / g, with an initial coulombic efficiency of 93.8%; after 500 cycles at 1C, the capacity retention rate was 88.6%, with a capacity decay rate of only 0.023% / cycle; at a high 5C rate, the reversible capacity reached 220.3mAh / g, with a capacity retention rate of 75.3%; within the 2.0-4.6V voltage range, the voltage decay rate after 1000 cycles was only 0.45mV / cycle, significantly superior to traditional lithium-rich materials. In-situ XRD analysis showed that the change rate of material cell parameters during cycling was less than 1.5%, with no obvious layered-to-spinel phase transition. XPS depth profiling revealed that the adaptive interface layer remained intact after cycling, and the surface oxygen vacancy concentration remained at a low level. TOF-SIMS detection confirmed that the BO and BN bonds in the boron-containing organic-inorganic hybrid polymer effectively captured reactive oxygen species and suppressed interfacial side reactions. After 400 cycles, the lithium anode surface morphology remained smooth in the full cell matched with the lithium metal anode, with no obvious dendrite formation, proving that the adaptive interface layer effectively blocked the migration of cathode byproducts to the anode.

[0022] Example 2: Cobalt-free gradient dual-channel lithium-rich cathode material and its application in pouch lithium metal batteries S1: Preparation of gradient element distribution precursor: ... , Dissolve in 800 mL of deionized water to form main metal salt solution A. Prepare aqueous solutions B of ZrCl4 (0.05 mol), (NH4)2WO4 (0.03 mol), and borax ( A solution of 0.06 mol / L NaOH and 0.8 mol / L Na₂CO₃ was used as precipitant C. Precipitant D was a mixed solution of NaOH (2.2 mol / L) and Na₂CO₃ (0.8 mol / L). The preparation process was similar to Example 1, but the flow rates and pH values ​​at each stage were adjusted: Core stage: Solution A flow rate 15 mL / min, precipitant D flow rate 10 mL / min, pH = 10.2, 50 °C; Intermediate layer stage: Solution B and A mixture flow rate 12 mL / min, precipitant D flow rate 18 mL / min, pH = 11.0, 55 °C; Outer layer stage: Solution C and A mixture flow rate 10 mL / min, precipitant D flow rate 25 mL / min, pH = 11.6, 60 °C. After processing, a cobalt-free gradient precursor was obtained. EDS confirmed that the concentrations of Zr and W in the outer layer reached 0.06, and the concentration of B in the intermediate layer was 0.025.

[0023] S2: Construction of a dual continuous transport network: 10 g of precursor, 2.0 g of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP, as a fluorocarbon precursor), and 1.0 g of oxalic acid (pore-forming agent) were dissolved in 70 mL of acetone / DMF (3:1, v / v) mixed solvent and ultrasonically dispersed for 2 hours. Spray drying conditions: inlet temperature 200℃, outlet temperature 85℃, flow rate 10 mL / min. Heat treatment was carried out in an argon / fluorine (95:5) mixed atmosphere: 300℃ for 2 hours, 700℃ for 4 hours, heating rate 2℃ / min. Characterization showed that fluorine (content 0.15 at%) was introduced into the carbon nanofiber network, enhancing its compatibility with the electrolyte; the oxygen vacancy gradient distribution characteristics were retained, with a surface concentration of 3.2 × 10¹⁹ cm⁻³.

[0024] S3: Lithification and Sulfur Doping: 8g of the product from step S2 was mixed with 3.0g of Li2CO3 and 0.3g of sodium thiosulfate (Na2S2O3) and ball-milled. Four-stage calcination was performed in an oxygen atmosphere: 350℃ / 2h → 600℃ / 3h → 800℃ / 4h → 880℃ / 8h, with a heating rate of 2℃ / min and an oxygen flow rate of 250mL / min. The product was named GDLMO-3, with the composition Li[Li0.22Mn0.62Ni0.16Zr0.022W0.012B0.018]O1.94S0.02F0.04; secondary particle diameter 3-5μm, BET specific surface area 7.2m² / g.

[0025] S4: Constructing an adaptive interface layer: GDLMO-3 was treated in fluorinated phosphoric acid vapor (generated by the pyrolysis of POF3) at 200°C for 1.5 hours, then immersed in a borosilicate solution (prepared by reacting tetraethoxysilane with triphenylboronic acid ester at a molar ratio of 2:1), stirred at 60°C for 10 hours, and heat-treated at 150°C for 3 hours to form a 10 nm thick interface layer with LiF:Li3PO4:boron-containing polymer = 32:28:40.

[0026] Pouch cell fabrication and testing: Positive electrode: GDLMO-3:SuperP:PVDF=85:7:8, areal loading 22mg / cm² (corresponding to areal capacity 5.2mAh / cm²), coated on 15μm aluminum foil; Negative electrode: 50μm lithium metal foil + 10μm Cu current collector; Electrolyte: 1.2M LiFSI + 0.1M LiDFOB in FEC / TEGDME (3:7, v / v), with 2wt% LiPO2F2 added; Separator: Glass fiber membrane (20μm); Assemble a 2Ah soft-pack battery (7cm×5cm) with an electrolyte injection volume of 3g / Ah.

[0027] Test conditions: 0.2C / 0.5C charge / discharge (2.0-4.7V), 25℃. Initial discharge specific capacity: 285.3mAh / g, initial efficiency: 92.5%; capacity retention after 200 cycles: 89.7%, energy density retention: 86.3%; capacity retention after 400 cycles: 83.2%; 5C rate capacity: 210.8mAh / g; 0.2C capacity retention at -20℃: 82.5%. Differential capacitance (dQ / dV) analysis showed that the oxygen redox peak intensity at 4.5V decreased by <10% after 400 cycles, indicating excellent oxygen framework stability. Battery disassembly revealed a uniform lithium metal anode surface with no obvious dendrites or dead lithium formation; XPS analysis of the cathode / electrolyte interface showed a stable LiF peak (685.2eV) intensity in the F1s spectrum, proving that the adaptive interface layer effectively suppressed electrolyte oxidation and decomposition. The battery passed safety tests such as needle penetration and overcharge (5.5V) without catching fire or exploding, demonstrating excellent safety performance.

[0028] Comparative Example 1: Lithium-rich manganese-based cathode material prepared by conventional co-precipitation method Li1.2Mn0.54Ni0.13Co0.13O2 was prepared using conventional methods: , , The precursor was dissolved and co-precipitated with NaOH (2.0 mol / L) and Na₂CO₃ (0.5 mol / L) at a constant flow rate of 10 mL / min (pH = 11.5, 60 °C). The precursor was mixed with Li₂CO₃ (5% excess) and calcined in oxygen at 900 °C for 15 hours. The product consisted of irregular micron-sized particles (D₅₀ = 5.5 μm) with no gradient elemental distribution or special structural design. The specific surface area was 1.5 m² / g, and I₀₀³ / I₁₀₄ = 1.15, indicating a high degree of cation mixing.

[0029] Under the same conditions, the coin cell battery exhibited a capacity of only 228.7 mAh / g at 0.1C initial discharge and an initial efficiency of 76.4%. After 200 cycles at 1C, the capacity retention was 58.3%, and the capacity at 5C was only 125.6 mAh / g. The voltage decay rate reached 1.8 mV / cycle after 100 cycles. The pouch cell (with the same design) retained only 62.8% of its capacity after 200 cycles, and a large number of dendrites and dead lithium were observed on the lithium anode surface. XPS analysis showed that the Mn2+ content on the cathode surface increased by 300% after 50 cycles, indicating severe transition metal dissolution. DSC testing showed that the fully charged material-electrolyte mixture exhibited severe exothermic activity at 245℃, indicating poor thermal stability.

[0030] Conclusion: Through comparison of the above embodiments and comparative examples, the lithium-rich manganese-based cathode material provided by this invention not only achieves a balance between high specific capacity and high initial efficiency, but also makes breakthrough progress in long cycle life, high rate performance, and thermal safety. In particular, for scenarios requiring high areal loading (>5 mAh / cm²) and matching with lithium metal anodes, this material exhibits excellent engineering application potential. Its fabrication process has good scalability and cost control advantages, providing a key material solution and technical path for the practical application of next-generation high-energy-density lithium metal batteries exceeding 600 Wh / kg.

[0031] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples. The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this invention should be included within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A lithium-rich manganese-based cathode material with a gradient dual-channel ion transport network, characterized in that, The general chemical formula of the cathode material is Li[LiaMnbNicCodM1-abcd]O2-eFe, where 0.15≤a≤0.25, 0.45≤b≤0.65, 0.10≤c≤0.25, 0.05≤d≤0.15, and 0.02≤e≤0.10; M is a gradient doping element selected from one or more of the group consisting of Zr, W, B, F, and S; wherein the gradient doping element M exhibits a double-shell-core structure in the radial distribution of the material particles: high-valence elements Zr4+ and W6+ are enriched in the outermost layer of the particles with a thickness of 30-50 nm, and the concentration is [missing value]. The cathode material has a concentration of 0.05-0.08; B element is enriched in the intermediate layer with a thickness of 100-150 nm and a concentration of 0.02-0.04; the M element concentration is reduced to 0.005-0.01 in the core region; a dual continuous ion / electron transport network is constructed inside the cathode material, including: lithium ion fast diffusion channels composed of grain boundary oxygen vacancies, and electron transport channels composed of in-situ carbon nanofiber interwoven networks; the cathode material surface is loaded with an adaptive interface layer with a thickness of 8-15 nm, the adaptive interface layer being composed of LiF, Li3PO4 and boron-containing organic-inorganic hybrid polymer.

2. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The boron-containing organic-inorganic hybrid polymer contains BO, BN, and BF bonds, which can capture reactive oxygen species and suppress interfacial side reactions under high voltage; the concentration of oxygen vacancies at the grain boundaries decreases in a gradient from the surface to the core, with a surface concentration of 10¹⁹-10²⁰ cm⁻³ and a core concentration of 10¹⁷-10¹⁸ cm⁻³; the carbon content in the in-situ carbon nanofiber network is 1.5-3.0 wt%, and the fiber diameter is 20-50 nm.

3. A method for preparing the lithium-rich manganese-based cathode material as described in claim 1 or 2, characterized in that, The method includes the following steps: S1: Preparation of gradient element distribution precursor: Manganese salt, nickel salt, cobalt salt and gradient doped element salt are dissolved in proportion, and the precipitant flow rate and reaction temperature are controlled by stepwise co-precipitation method to achieve a gradient distribution of element concentration in the radial direction of the particles, and obtain a double shell-core structure precursor. S2: Constructing a dual continuous transport network: The precursor is mixed with a carbon-containing precursor and a pore-forming agent, and microspheres are formed by spray drying. Then, the mixture is heat-treated under a protective atmosphere to form an in-situ carbon nanofiber network and an oxygen vacancy gradient distribution. S3: Lithification and fluorine doping: The product obtained in step S2 is mixed with a lithium source and a fluorine source, and then calcined in multiple stages under an oxygen atmosphere to achieve lithiation and fluorine doping. S4: Constructing an adaptive interface layer: Disperse the material obtained in step S3 in a solution containing fluorine, phosphorus, and boron precursors, and form an adaptive interface layer in situ on the material surface through vapor deposition and sol-gel synergistic process.

4. The preparation method according to claim 3, characterized in that, In step S1, the stepwise coprecipitation method is divided into three stages: the first stage controls the pH to 10.0-10.5 and the temperature to 50-55℃ to form the core; the second stage controls the pH to 11.0-11.3 and the temperature to 55-60℃ to form the intermediate layer containing Zr and W elements; the third stage controls the pH to 11.5-11.8 and the temperature to 60-65℃ to form the outer shell layer rich in B elements; the flow rate of the precipitant increases sequentially in each stage, namely 8-10 mL / min, 15-18 mL / min, and 20-25 mL / min.

5. The preparation method according to claim 3 or 4, characterized in that, In step S2, the carbon-containing precursor is polyacrylonitrile, polyvinylidene fluoride, or a copolymer thereof, and the amount added is 10-25% of the precursor mass; the pore-forming agent is citric acid, oxalic acid, or a mixture thereof, and the amount added is 5-15% of the precursor mass; the heat treatment is carried out in an inert or fluorine-containing atmosphere at a temperature of 700-800℃ for 2-5 hours.

6. The preparation method according to any one of claims 3-5, characterized in that, In step S3, the multi-stage calcination includes at least three stages: the first stage is held at 350-450℃ for 1-3 hours, the second stage is held at 700-800℃ for 3-5 hours, and the third stage is held at 850-920℃ for 8-12 hours, with a heating rate of 2-4℃ / min for each stage; the fluorine source is NH4F, polytetrafluoroethylene pyrolysis products, or fluorine-containing gas.

7. The preparation method according to any one of claims 3-6, characterized in that, In step S4, the vapor deposition uses fluorine-containing gas C2F6 or POF3 at a temperature of 180-220°C for 1-3 hours; the boron-containing precursor is prepared by reacting organosilanes with borate esters, and the heat treatment temperature is 150-250°C for 2-4 hours.

8. A lithium metal battery, characterized in that, The device includes a positive electrode, an electrolyte, and a lithium metal negative electrode, wherein the positive electrode comprises a lithium-rich manganese-based positive electrode material as described in claim 1 or 2, the electrolyte is a fluorinated ether electrolyte or a solid electrolyte, and the surface of the lithium metal negative electrode is modified with a boron-containing protective layer.

9. The lithium metal battery according to claim 8, characterized in that, The fluorinated ether electrolyte is 1.0-1.5M lithium salt (LiTFSI, LiFSI or a mixture thereof) in a fluorinated ether solvent (FEC, TFEO, HFE or a mixture thereof), with 0.1-0.5M LiPO2F2 or LiDFOB added as an additive; the positive electrode surface loading is 4.5-6.0 mAh / cm², corresponding to an N / P ratio of 1.1-1.

8.

10. The application of a lithium-rich manganese-based cathode material as described in claim 1 or 2 in high-energy-density lithium metal batteries, electric vehicle power batteries, or large-scale energy storage systems.

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