Modified high-nickel ternary lithium-ion battery positive electrode material and preparation method thereof

Abstract

The application provides a modified high-nickel ternary lithium ion battery positive electrode material and a preparation method thereof. The modified high-nickel ternary lithium ion battery positive electrode material comprises a base and a coating layer wrapped on the surface of the base. The chemical formula of the base is LiNi x Co y Mn 1‑x‑y O2 or LiNi x Co y Al 1‑x‑y O2, wherein 0.80≤x≤0.95, 0.03≤y≤0.15, and 0 12 The coating layer comprises one or more of Li2ZrO3, LiAlO2, Li2TiO3, Li4Ti5O4, Al2O3, TiO2, ZrO2, boron oxide, borate, metal fluoride or metal oxyfluoride. Through the synergistic doping of cations and anions, a strong chemical bond network is formed in the crystal lattice, which effectively inhibits the cation mixing, lattice distortion and harmful phase change. At the same time, the coating layer optimizes the surface interface properties of the material, effectively isolates the electrolyte from the active material, inhibits the interface side reaction, and improves the interface lithium ion transmission kinetics, thereby significantly improving the cycle stability, rate performance and thermal safety of the material.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a modified high-nickel ternary lithium-ion battery cathode material and its preparation method. Background Technology

[0002] High-nickel ternary cathode materials typically refer to layered NCM and NCA oxides with a nickel molar content of ≥80%. Due to their outstanding advantages of high specific capacity and high energy density, they are the core cathode materials for next-generation high-energy-density lithium-ion batteries. However, increasing the nickel content significantly amplifies the inherent defects of the material, leading to a substantial decrease in structural stability, cycle life, and thermal safety, which severely limits its large-scale commercial application.

[0003] Specifically, the performance degradation of high-nickel ternary materials mainly stems from three core issues: bulk structural instability, frequent interfacial side reactions, and poor thermal safety.

[0004] In terms of bulk structure, Ni 2+ With Li + With similar ionic radii, Ni readily undergoes cation mixing during synthesis and electrochemical cycling. 2+ Occupying active sites in the lithium layer hinders lithium-ion diffusion and disrupts the layered structure, leading to capacity decay. Simultaneously, high-voltage charging and discharging induces anisotropic lattice distortion, generating accumulated internal stress and inducing microcracks in the particles. This allows electrolyte to penetrate the particle interior, continuously exacerbating side reactions and ultimately causing particle pulverization and collapse. Furthermore, in the delithiation state, high-valence Ni is easily formed on the material surface. 4+ It readily undergoes parasitic side reactions with the electrolyte, forming a high-resistivity interface layer, accompanied by an irreversible phase transition of the layered structure to the spinel phase and rock salt phase, leading to the loss of active lithium and voltage decay.

[0005] In terms of thermal safety and interface performance, high-nickel systems reduce the lattice oxygen evolution potential, making them prone to oxygen release under abusive conditions such as high temperature and overcharging. This oxygen release can lead to a violent exothermic reaction with the electrolyte, inducing battery thermal runaway. Furthermore, the heat accumulated from structural cracking and interfacial side reactions can further deteriorate safety performance. Meanwhile, alkaline lithium impurities such as LiOH and Li2CO3 remaining on the material surface not only react with the electrolyte to generate gas, causing battery swelling, increasing interfacial impedance, and worsening rate performance, but also accelerate electrolyte decomposition and transition metal dissolution, continuously exacerbating battery performance degradation.

[0006] To address the aforementioned issues, the current mainstream improvement methods in the industry mainly include water washing and purification, single-crystal structure regulation, bulk element doping, and surface coating modification. However, existing technologies all have significant shortcomings and cannot achieve a synergistic improvement in the overall performance of materials.

[0007] Traditional water-washing purification processes have inherent drawbacks: the washing process causes the dissolution of active lithium in the material, disrupting the standard stoichiometry, reducing the initial coulombic efficiency and discharge capacity, and interfering with subsequent doping processes, leading to uneven distribution of modified elements. Water washing also damages the layered structure of the material's surface, easily causing problems such as residual lithium redistribution and surface recarbonation in the post-processing stage, resulting in poor batch consistency. Furthermore, the multi-step water washing process is cumbersome, energy-intensive, and water-intensive, failing to meet the demands of green and low-cost industrial manufacturing.

[0008] Single-crystal structure design can effectively suppress the propagation of microcracks in polycrystalline materials, but existing single-crystal preparation technologies struggle to balance performance and cost. Traditional high-temperature, long-time sintering processes are energy-intensive, have narrow process windows, and poor controllability. High-temperature sintering easily leads to grain agglomeration, and subsequent mechanical crushing introduces new surface defects, making it difficult to stably prepare small-diameter single-crystal particles with uniform particle size. Furthermore, single-crystal materials suffer from long lithium-ion diffusion paths, resulting in a general trade-off between structural stability and rate performance.

[0009] Furthermore, existing single modification strategies suffer from severe synergy deficiencies: bulk doping can only stabilize the internal structure of the material, offering limited protection for the electrode interface; surface coating can only isolate surface side reactions, and the coating layer is prone to failure after long-term cycling, and it cannot suppress the initiation and propagation of internal cracks within the particles. Since the failure of high-nickel materials is a complex process coupled with bulk structural degradation and interfacial side reactions, single modification methods generally address one aspect while neglecting another, failing to achieve comprehensive performance optimization.

[0010] In summary, current technologies for preparing and modifying high-nickel ternary cathode materials generally suffer from bottlenecks such as water washing damaging the material structure, difficulty in controlling the synthesis of single-crystal particles, and insufficient synergy in modification strategies. These limitations make it difficult to meet the industrial application requirements of high-energy, long-cycle, and high-safety lithium-ion batteries. Therefore, there is an urgent need to develop a novel modified high-nickel ternary lithium-ion battery cathode material and its preparation method to avoid the drawbacks of traditional water washing processes, stably prepare high-quality, small-diameter single-crystal particles, and simultaneously and synergistically optimize the bulk structure and surface interface properties of the material, thus overcoming the limitations of existing technologies. Summary of the Invention

[0011] The purpose of this invention is to provide a modified high-nickel ternary lithium-ion battery cathode material and its preparation method, so as to solve the technical problems existing in the background art.

[0012] The technical solution adopted in this invention is as follows: a modified high-nickel ternary lithium-ion battery cathode material, wherein the modified high-nickel ternary lithium-ion battery cathode material comprises a matrix and a coating layer wrapped around the surface of the matrix, and the chemical formula of the matrix is ​​LiNi. x Co y Mn 1-x-y O2 or LiNi x Co yAl 1-x-y O2, wherein 0.80≤x≤0.95, 0.03≤y≤0.15, and 0<1-xy≤0.17; the matrix further includes cation doping elements and anion doping elements; the cation doping elements include one or more of Ti, Zr, Al, Na, Mg, and W, and the total content of the cation doping elements is 0.05~1.5 mol% based on the total molar amount of transition metals; the anion doping elements include one or more of F, Cl, S, B, or P, and the total content of the anion doping elements is 0.02~1.0 mol% based on the total molar amount of theoretical oxygen sites in the matrix; the coating layer includes Li2ZrO3, LiAlO2, Li2TiO3, and Li4Ti5O3. 12 One or more of Al2O3, TiO2, ZrO2, boron oxides, borates, metal fluorides, or metal oxyfluorides.

[0013] The modified high-nickel ternary lithium-ion battery cathode material matrix of the present invention is preferably an NCM811 or NCM83 series material. This composition can maintain the stability of the layered structure by means of appropriate amounts of Co and Mn elements while ensuring a high nickel content and high discharge capacity, thus avoiding rapid structural degradation due to excessive nickel content. Anions such as F mainly act on the oxygen site environment on or near the surface of the material, which can improve surface oxygen stability, reduce the tendency of lattice oxygen release under high delithiation state, and mitigate electrolyte decomposition and HF erosion.

[0014] By co-doping with cations and anions, a strong chemical bond network is formed within the crystal lattice, effectively suppressing cation mixing, lattice distortion, and harmful phase transitions. Simultaneously, the coating layer optimizes the material's surface interface properties, effectively isolating the electrolyte from the active material, suppressing interfacial side reactions, and improving interfacial lithium-ion transport kinetics, thereby significantly enhancing the material's cycle stability, rate performance, and thermal safety. The total molar amount of transition metals described in this invention is calculated as the total molar amount of Ni, Co, and Mn, or the total molar amount of Ni, Co, and Al.

[0015] More preferably, the doping concentration of the aforementioned cation dopant element in the matrix particles decreases from the surface to the interior.

[0016] During sintering, some of the aforementioned elements enter the crystal lattice, while others accumulate in the near-surface region of the particles, thus forming a gradient doping structure from the interior to the surface of the particles. This structure enhances bulk lattice stability and suppresses Ni... ²+ / Li + The mixed arrangement of cations enhances the surface's resistance to electrolyte corrosion. Its gradient distribution can be demonstrated through XPS depth profiling, STEM-EDS linear scanning, or elemental surface scanning.

[0017] More preferably, the above-mentioned coating layer has a double-layer structure; the first coating layer includes one or more of Li2ZrO3, LiAlO2 or other Li-Ti-O type lithium titanium composite oxides, with a thickness of 2 to 10 nm; the second coating layer includes one or more of Al2O3, B2O3, TiO2, ZrO2, borate, metal fluoride or metal oxyfluoride, with a thickness of 1 to 8 nm.

[0018] The first coating layer, located close to the material matrix, reacts with residual lithium on the surface to form a stable lithium metal composite oxide. This reduces the content of free LiOH and Li₂CO₃ and forms an inner interface with some lithium-ion conductivity, thereby lowering interfacial impedance. The second coating layer, the outer coating layer, is mainly used to continuously cover the material surface, reducing direct contact between the electrolyte and the highly active, high-nickel cathode surface, and inhibiting electrolyte oxidation and decomposition, HF corrosion, and transition metal dissolution. The inner layer primarily converts residual lithium and reduces interfacial transport impedance, while the outer layer primarily isolates the electrolyte and inhibits HF corrosion and transition metal dissolution. The two layers are continuously combined but have different functions.

[0019] More preferably, the second coating layer contains both elements B and F, wherein the mass ratio of B to F is 2:1 to 8:1.

[0020] When boron (B) and fluorine (F) are used together in the second coating layer, the preferred mass ratio of B to F is 3:1 to 6:1. Within this range, the boron (BO) structure can form a more continuous interfacial stability network, and the F component can regulate the surface oxygen environment and improve resistance to HF corrosion. If the B / F mass ratio is less than 2:1, the continuity of the BO network is insufficient, and the outer layer interfacial stabilization effect decreases; if the B / F mass ratio is greater than 8:1, the fluorine-containing interfacial regulation effect is insufficient, and it may increase the lithium-ion transport impedance of the outer coating layer, resulting in poor rate performance and post-cycle impedance control.

[0021] Boron (B) is not used as a primary bulk cation dopant element in this invention, but is preferably present as a non-metallic interface modifier element in the second coating layer, primarily improving the surface stability of the material in the form of a BO structure, a borate structure, or a boron-oxygen network. When B is used as a non-metallic interface modifier component in the second coating layer, its addition amount is preferably 300–1500 ppm, more preferably 600–1200 ppm, based on the final cathode material mass. When phosphorus (F) is used as an interface modifier component in the second coating layer, its addition amount is preferably 100–1000 ppm, more preferably 150–500 ppm, based on the final cathode material mass.

[0022] Further preferably, the above-mentioned cathode material has a single crystal or near-single crystal morphology, wherein D50 is 1.5–2.5 μm and D90 is no greater than 4.0 μm. This particle size range can shorten the lithium-ion diffusion path, avoid excessively fine particles leading to excessive specific surface area, reduce grain boundary cracking and increased side reactions in polycrystalline secondary particles, and improve rate performance.

[0023] Based on the same technical concept, the present invention also provides a method for preparing the above-mentioned modified high-nickel ternary lithium-ion battery cathode material, comprising the following steps: S1. A modified mixture is prepared by mixing a nano-sized high-nickel ternary precursor obtained by co-precipitation, nano-phase separation or reverse microemulsion with a lithium source and a dopant. S2. The modified mixture is placed in an oxygen atmosphere and subjected to segmented heating and sintering and programmed cooling to complete lithiation, element doping solid solution and grain growth, thereby obtaining a single crystal or near-single crystal intermediate product. S3. The intermediate product is mixed and sintered with the coating precursor to obtain a modified high-nickel ternary lithium-ion battery cathode material with uniform particle size.

[0024] Traditional water washing can reduce residual alkali, but it can cause Li... + Dissolution, surface structure damage, and subsequent drying fluctuations are common issues. This invention does not rely on extensive water washing, but rather reduces residual alkali formation and converts residual lithium on the surface during the precursor, lithiation sintering, and coating reactions. This invention does not directly remove surface lithium compounds through water washing, but rather converts some free LiOH and Li₂CO₃ into LiAlO₂, Li₂ZrO₃, Li₂TiO₃, or other lithium metal composite oxides during the coating reaction. The "non-water washing" aspect of this invention does not mean that all steps in the cathode material preparation process are free of water washing, but rather that no water washing is performed after lithiation sintering. Water washing involved in steps such as precursor preparation is not considered "non-water washing" in this invention.

[0025] More preferably, in step S1 above, the molar ratio of the lithium source to the transition metal in the nanoscale high-nickel ternary precursor is 1.05:1 to 1.08:1.

[0026] More preferably, in step S1 above, the dopant includes a cationic dopant and anionic / nonmetallic dopant; the cationic dopant is selected from at least one of ZrO2, TiO2, Na2CO3, Al2O3, MgO, and WO3; the anionic / nonmetallic dopant is selected from at least one of H3BO3, LiF, NH4F, NH4H2PO4, and Li3PO4.

[0027] In a further preferred embodiment, the segmented heating and cooling process in step S2 is as follows: heating at 2-5℃ / min to 450-500℃ and holding for 2-5 hours; then heating at 2-5℃ / min to 780-820℃ and holding for 10-20 hours; subsequently cooling at 2-5℃ / min to 600℃ and holding for 2 hours, then cooling further to 300℃ and holding for 1 hour, and finally cooling with the furnace.

[0028] This sintering process avoids abnormal grain growth, reduces internal thermal stress and coating layer cracking, while ensuring the integrity of the layered structure. In the 450-500℃ stage, the lithium source and dopant undergo initial decomposition and pre-lithiation; in the 780-820℃ stage, Ti… 4+ Zr 4+ High-valence cations diffuse from the surface into the bulk phase in a limited manner, replacing some transition metal sites and forming a doping gradient that is "enriched on the surface and decreases in the interior." This gradient structure can improve the surface's resistance to corrosion and phase transitions, while preventing excessive doping from reducing capacity in the bulk phase.

[0029] More preferably, the mixing and sintering in step S3 above is a two-stage sintering process; under an oxygen atmosphere, the first coating precursor is first mixed with the intermediate product and reacted at 500-600°C for 3-5 hours; then the second coating precursor is added and reacted at 300-400°C for 3-5 hours; the first coating precursor is selected from at least one of Al2O3, TiO2, ZrO2, aluminum isopropoxide, tetrabutyl titanate, and zirconium source; the second coating precursor is selected from at least one of H3BO3, LiF, NH4F, NH4H2PO4, and fluoroborate.

[0030] More preferably, based on the final cathode material mass, the total amount of the first coated precursor, calculated according to the Al, Ti, and Zr elements, is 300–3000 ppm; the total amount of the second coated precursor, calculated according to the B, F, and P elements, is 100–2500 ppm, wherein the B element content is 300–1500 ppm and the F element content is 100–1000 ppm. The above amounts are calculated based on the mass of the corresponding elements, not the total mass of the precursor compound.

[0031] Compared with existing technologies, the beneficial effects of this invention are as follows: The modified high-nickel ternary lithium-ion battery cathode material of this invention forms a strong chemical bond network within the crystal lattice through synergistic doping of cations and anions, effectively suppressing cation mixing, lattice distortion, and harmful phase transitions. Simultaneously, the coating layer optimizes the surface interface properties of the material, effectively isolating the electrolyte from the active material, suppressing interfacial side reactions, and improving interfacial lithium-ion transport kinetics, thereby significantly improving the material's cycle stability, rate performance, and thermal safety.

[0032] High-content doping often sacrifices material capacity, while low-content doping fails to adequately protect the surface. This invention utilizes diffusion differences during sintering to achieve a slightly higher dopant content at the particle surface, gradually decreasing towards the interior. The interior of the particle maintains a high nickel content and high reversible capacity, while the surface exhibits better structural stability and resistance to electrolyte erosion. Since structural degradation and side reactions in high-nickel materials typically occur first at the surface, this gradient structure can improve cycle retention and thermal stability without significantly sacrificing capacity.

[0033] The first coating layer of the present invention is preferably Li2ZrO3, LiAlO2, Li2TiO3, or Li4Ti5O. 12 Li-Ti-O type lithium-titanium composite oxides, or lithium metal composite oxides containing Al / Ti / Zr, have a tighter bond with the matrix, can consume some residual lithium on the material surface, reduce the content of free LiOH and Li2CO3, and form a more stable inner layer transition structure. The second coating layer preferably contains B, F, P, or stable oxide / oxyfluoride components, covering the outside of the first coating layer, further reducing the interaction between the electrolyte and highly active Ni. 4+ Direct surface contact reduces HF corrosion, electrolyte oxidation and decomposition, and transition metal dissolution. The double-layer coating does not simply increase the coating thickness; rather, the inner layer addresses interfacial bonding and residual lithium conversion, while the outer layer addresses electrolyte contact and interfacial stability. The two layers have different functions.

[0034] The preparation method of this invention reduces Li / TM deviation and surface defects caused by water washing through non-water washing lithiation and non-water washing residual alkali removal; the two-stage programmed sintering allows the highly active precursor to form small-particle single crystals / quasi-single crystals at a relatively mild temperature; Ti / Zr and other cation gradient doping enhances the MO framework and inhibits Li + / Ni 2+ Mixed arrangement; F − The anion layer stabilizes the surface oxygen environment and increases the oxygen release temperature; the lithium-conducting inner layer reduces interfacial impedance and converts residual lithium; and the stabilizing outer layer isolates electrolyte side reactions. These measures enable the prepared modified high-nickel ternary lithium-ion battery cathode material to improve cycle life, rate capability, and thermal safety. Attached Figure Description

[0035] Figure 1 This is a comparison diagram of the XRD structures of the embodiments and comparative examples of the present invention; Figure 2 The image shows the electron microscope (EM) results of the cathode material prepared in Example 1 of this invention. Figure 3 This is a comparison chart showing the residual alkali and slurry stability results of the cathode materials in the examples and comparative examples; Figure 4 The graph shows the cycle performance test results of the cathode materials prepared in the embodiments and comparative examples of this invention; Figure 5 This is a comparison chart of the specific discharge capacity at 5C rate of the embodiments and comparative materials of the present invention; Figure 6 This is a comparison chart of the charge transfer impedance Rct results of the embodiment and the comparative material of the present invention after 100 cycles; Figure 7 The above are DSC exothermic curves of the materials used in the embodiments and comparative examples of this invention. Figure 8 This is a statistical comparison chart of the DSC thermal stability of the materials in the embodiments and comparative examples of the present invention. Detailed Implementation

[0036] To facilitate understanding of the present invention, it will be described more fully and in detail below, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0038] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0039] The technical concept of this invention originates from five interconnected technical steps: First, a non-water-washed lithiation and non-water-washed residual alkali removal route is adopted to reduce the loss of active lithium and damage to the surface structure caused by water washing; Second, cationic doping elements such as Ti, Zr, Al, and Mg are introduced to enhance transition metal-oxygen bonding and reduce Li⁺ / Ni²⁺ mixing; Third, anionic or non-metallic regulating components such as F, B, and P are introduced to improve the surface oxygen environment and interface stability; Fourth, a lithium-conducting inner layer (first coating layer) and an interface-stabilizing outer layer (second coating layer) are set to respectively undertake the functions of residual lithium conversion, interface bonding, and side reaction isolation; Fifth, a two-stage sintering and segmented slow cooling are adopted to control grain growth, element diffusion, and coating layer continuity.

[0040] The above-described technical approach directly corresponds to the preparation steps of this invention. The non-water-washed lithiation and non-water-washed residual alkali removal routes reduce Li+ dissolution, Li / TM ratio deviation, and surface water erosion caused by water washing; the low-speed heating and medium-temperature pre-lithiation stages allow the dopant and coating precursor to react on the particle surface first, forming an element-enriched layer; the high-temperature crystallization stage allows some dopant elements to diffuse into the particle interior, forming a gradient distribution with a slightly higher concentration on the surface and a relatively lower concentration inside; the segmented cooling stage reduces thermal stress, making the coating layer continuous and reducing abnormal grain growth. Therefore, the resulting material is not a single coated powder, nor is it a typical uniformly doped powder, but rather a high-nickel ternary cathode material where the bulk phase, near-surface layer, and surface interface are simultaneously regulated.

[0041] Example 1: A method for preparing a modified high-nickel ternary lithium-ion battery cathode material: The target composition of this example is LiNi. 0.88 Co 0.07 Mn 0.05 O2 is used to produce a high-nickel ternary cathode material. A Ni, Co, and Mn molar ratio of 88:7:5 hydroxide precursor is mixed with LiOH·H2O at a Li / Me ratio of 1.045:1, where Me represents the total molar amount of Ni, Co, and Mn. Al2O3, ZrO2, MgO, and TiO2 are added as cation dopants, with the following amounts based on the final cathode material mass: Al: 800 ppm, Zr: 1200 ppm, Mg: 500 ppm, Ti: 600 ppm. LiF and H3BO3 are added as anion / non-metallic adjusting components, with the following amounts based on the final material mass: F: 300 ppm, B: 800 ppm. The resulting mixture is then prepared.

[0042] The mixture was sintered in a two-stage process under an oxygen atmosphere: first, the temperature was increased to 480℃ at 4℃ / min and held for 3 hours to decompose the lithium source and complete the initial lithiation; then, the temperature was increased to 790℃ at 2℃ / min and held for 14 hours to form the main crystalline phase and promote the diffusion of dopant elements; subsequently, the temperature was decreased to 600℃ at 3℃ / min and held for 2 hours, then decreased to 300℃ and held for 1 hour, and finally cooled in the furnace. After sintering, the material was lightly crushed and sieved to obtain single-crystal or near-single-crystal matrix materials.

[0043] Then, a double-layer coating process is performed. First, the above matrix material is mixed with nano-Al₂O₃ and TiO₂, with Al and Ti added at 1000 ppm and 500 ppm respectively. The mixture is then heated at 500℃ for 4 hours in an oxygen atmosphere to form a first coating layer containing LiAlO₂, Li-Ti-O, or Al / Ti composite oxides. Next, H₃BO₃ and LiF are added, with B and F added at 800 ppm and 200 ppm respectively. The mixture is then heated at 350℃ for 5 hours to form an outer interface stabilizing layer containing B / F. Finally, a modified high-nickel ternary lithium-ion battery cathode material is obtained.

[0044] Example 2: A method for preparing a modified high-nickel ternary lithium-ion battery cathode material: This example is basically the same as Example 1, except that the molar ratio of Ni, Co, and Mn in the precursor is 90:5:5, and the target material is LiNi. 0.90 Co 0.05 Mn 0.05 The O2, Li / Me ratio was 1.05:1, and the second-stage sintering temperature for lithium doping was 780℃, with a holding time of 15h. The cationic dopants used were Al2O3, ZrO2, and MgO, with the following addition amounts based on the final material mass: Al: 1000ppm, Zr: 1500ppm, and Mg: 600ppm, respectively; the double-layer coating treatment was the same as in Example 1.

[0045] Example 3: A method for preparing a modified high-nickel ternary lithium-ion battery cathode material: This example is basically the same as Example 1, except that the second stage sintering temperature of lithium doping is 800℃ and the holding time is 12h; the amount of H3BO3 in the second coating layer is increased, the amount of B added is 1200ppm based on the final material mass, and the amount of F added is 200ppm.

[0046] Example 4: A method for preparing a modified high-nickel ternary lithium-ion battery cathode material: The target composition of this example is LiNi. 0.8 3Co 0.11 Mn 0.06 O2 is used to prepare a high-nickel ternary cathode material. Nickel nitrate, cobalt nitrate, and manganese nitrate are prepared as a metal brine phase in a Ni:Co:Mn ratio of 83:11:6. Cyclohexane is used as the oil phase, and Span 80 is used as the surfactant. After the reaction, acetone is used for demulsification, and anhydrous ethanol is used to replace and clean the resulting solid precursor to remove the oil phase and surfactant. The anhydrous ethanol cleaning described above is not part of the washing of the lithium-ionized cathode material, nor is it part of the water washing step for removing residual alkali in high-nickel cathode materials.

[0047] The obtained precursor was mixed with LiOH·H2O at a Li / Me ratio of 1.055:1, and Na2CO3 and a small amount of H3BO3 were added as doping / interface conditioning components, with Na and B added at 1000 ppm and 400 ppm, respectively. The mixture was first heated at 500℃ for 4 h in an oxygen atmosphere, then at 760℃ for 15 h, and after staged cooling, a Na / B-adjusted single crystal or near-single crystal NCM83 matrix material was obtained.

[0048] The aforementioned NCM83 matrix material was then subjected to a double-layer coating treatment: first, aluminum isopropoxide was added as the precursor for the first coating layer, with an Al addition amount of 1000 ppm based on the final material mass. The mixture was then heated at 500°C for 4 hours in an oxygen atmosphere to allow residual lithium on the surface to react with the Al source, forming a lithium-ion conductive inner layer primarily composed of LiAlO2 / Al-O. Next, H3BO3 and a small amount of LiF were added, with B and F addition amounts of 800 ppm and 200 ppm, respectively. The mixture was then heated at 350°C for 5 hours to form an interface-stabilized outer layer containing BO and F regulating components. Finally, a single-crystal or near-single-crystal NCM83 material with Na / B regulation, a LiAlO2 / Al-O inner layer, and a B / F outer layer was obtained. This embodiment illustrates that the present invention is not limited to NCM88 or NCM90 systems, and that a double-layer coating structure with different internal and external functions can also be formed in the NCM83 system.

[0049] HRTEM results showed that the material surface of Example 4 exhibited a continuous bilayer coating structure. The inner layer, closer to the substrate, was approximately 3-6 nm thick and mainly contained Al, O, and a small amount of Li signals, classifying it as a LiAlO2 / Al-O type lithium-ion conductive inner layer. The outer layer, approximately 2-4 nm thick, mainly contained B, F, and O signals, classifying it as an interface-stabilizing outer layer containing BO and F modulating components. STEM-EDS line scanning revealed that Na and some B signals were detectable in the near-surface region, with B and F signals being more pronounced in the outermost layer. This indicates that Example 4 was not a single uniform coating but rather formed a bilayer functional coating structure consistent with the definition of this invention.

[0050] Example 5: A method for preparing a modified high-nickel ternary lithium-ion battery cathode material: This example uses LiNi 0.88 Co 0.07 Mn 0.05 Using O2 as a matrix, an interface-stabilized material for semi-solid or solid-state battery applications was prepared. In this embodiment, the bulk cation dopants were ZrO2, MgO, and TiO2, with addition amounts of Zr: 1200 ppm, Mg: 500 ppm, and Ti: 600 ppm, respectively, based on the final material mass. No Al source was added as a bulk cation dopant during the lithiation sintering stage. The sintering regime was the same as in Example 1. After sintering, an aluminum isopropoxide or nano-Al2O3 was used to construct the first coating layer, with Al addition amounting to 1500 ppm based on the final material mass. A secondary interface treatment was performed at 450°C to form a relatively continuous LiAlO2 / aluminum oxide composite interface layer on the surface. Subsequently, H3BO3 and LiF were used to form the second coating layer, with B and F addition amounts of 800 ppm and 200 ppm, respectively. This interface layer is used to reduce interfacial side reactions between the high-nickel cathode and the oxide solid electrolyte.

[0051] Comparative Example 1: Undoped, uncoated NCM88 material This comparative example uses the same Ni:Co:Mn=88:7:5 precursor and LiOH·H2O as in Example 1, with a Li / Me ratio of 1.045:1, but without the addition of cationic dopants, anionic / nonmetallic modifiers, or double-layer coating. The sintering process involves heating to 790℃ at a rate of 3℃ / min and holding for 14 hours, followed by natural cooling. This comparative example illustrates the deficiencies in structural and interfacial stability of high-nickel materials without the synergistic modification of the bulk and interface phases of this invention.

[0052] Comparative Example 2: Cation-only doping, no anion modulation, and no coating This comparative example is essentially the same as Example 1, except that Al₂O₃ and ZrO₂ are added as cationic dopants, with Al and Zr added at 800 ppm and 1200 ppm, respectively. LiF and H₃BO₃ are not added, and no double-layer coating treatment is performed. This comparative example is used to illustrate that simple cationic doping can improve the bulk structure, but its improvement on residual alkali, interfacial side reactions, and post-cycle impedance growth is limited.

[0053] Comparative Example 3: Only a single layer of Al2O3 coating, without bulk doping This comparative example is essentially the same as Example 1, but without the addition of bulk dopants and anion modifiers. Only a single-layer Al₂O₃ coating is performed after sintering. The Al addition amount is 1500 ppm based on the final material mass, the coating temperature is 500°C, and the holding time is 4 hours. This comparative example illustrates that single-layer coating can partially reduce interfacial side reactions, but cannot sufficiently suppress bulk structure degradation.

[0054] Comparative Example 4: NCM88 material prepared by conventional water washing process This comparative example uses conventional co-precipitation precursors and high-temperature solid-state sintering to prepare LiNi. 0.88 Co 0.07 Mn 0.05 O2. After sintering, the sample was washed with deionized water at a liquid-to-solid ratio of 1.0:1 for 30 minutes. After filtration, it was dried at 120°C and then subjected to a second heat treatment at 500°C. This comparative example does not involve the gradient doping and double-layer coating of the present invention. This comparative example is used to illustrate that although water washing can reduce residual alkali, it can cause damage to the surface structure and a decrease in cycle stability.

[0055] Comparative Example 5: High-Temperature Rapid Sintering Process The raw material formulation for this comparative example is the same as that for Example 1, but the sintering process is changed to heating to 880°C at a rate of 10°C / min and holding for 12 hours, followed by natural cooling. The 480°C pre-lithiation stage and the segmented slow cooling at 600°C and 300°C are not used. This comparative example is used to illustrate the necessity of the low-speed two-stage heating and segmented slow cooling of the present invention for forming small-particle-size single crystals, gradient distribution, and continuous coating layers.

[0056] I. Testing Methods XRD testing was performed using Cu Kα rays, with a scanning range of 10°–80°. The orderliness of the layered structure was evaluated by the intensity ratio of the (003) peak to the (104) peak, and the Li / Ni mixing ratio was calculated using Rietveld refinement. Generally, a higher I(003) / I(104) ratio indicates better orderliness of the layered structure and a lower degree of Li / Ni mixing; the Li / Ni mixing ratio was further estimated using Rietveld refinement.

[0057] SEM is used to observe particle morphology, particle size distribution, and post-cycle cracking; TEM or HRTEM is used to observe the coating thickness and continuity; STEM-EDS line scan or area scan is used to confirm the distribution of elements such as Al, Ti, Zr, Mg, F, and B inside the particles, near the surface, and on the surface. For single-crystal or near-single-crystal characteristics, further confirmation can be made through HRTEM lattice fringe continuity, selected area electron diffraction (SAED), or EBSD orientation analysis; SEM is only used to observe particle morphology and agglomeration state and is not used alone as a basis for single-crystal determination.

[0058] XPS depth profiling was used to analyze the valence state and elemental distribution of surface elements, with a focus on observing changes in the signals of Al 2p, Ti 2p, Zr 3d, F 1s, B 1s, and O 1s. The residual alkali was determined using acid-base titration or potentiometric titration to measure the contents of LiOH and Li₂CO₃, respectively.

[0059] Electrochemical performance was tested using coin half-cells. The positive electrode was prepared from positive electrode material, conductive agent, and binder in a mass ratio of 90:5:5. The electrolyte was a conventional carbonate system, and the negative electrode was a lithium metal sheet. The test voltage range was 2.8–4.3 V, and the test temperature was 25 °C. Rate performance was tested in the order of 0.2C, 0.5C, 1C, 2C, and 5C. The EIS test frequency range was 100 kHz to 0.01 Hz. The DSC test used a system where the positive electrode material was charged to 4.3 V and then in contact with the electrolyte, with a heating rate of 5 °C / min.

[0060] II. Test Results and Analysis 1. XRD structure results, such as Figure 1 As shown.

[0061] Typical tests were performed on the samples prepared according to the above embodiments, and the following results were obtained: Examples 1 to 5 all showed typical α-NaFeO2 type layered structures, and no obvious spinel phase or rock salt phase impurities were observed. In Example 1, the I(003) / I(104) ratio was 1.57, the c / a value was 4.964, and the Li / Ni mixing ratio was 2.3%; in Example 2, the I(003) / I(104) ratio was 1.51, the c / a value was 4.960, and the Li / Ni mixing ratio was 2.8%; in Example 3, the I(003) / I(104) ratio was 1.59, the c / a value was 4.966, and the Li / Ni mixing ratio was 2.1%; in Example 4, the I(003) / I(104) ratio was 1.55, the c / a value was 4.963, and the Li / Ni mixing ratio was 2.5%; and in Example 5, the I(003) / I(104) ratio was 1.54, the c / a value was 4.961, and the Li / Ni mixing ratio was 2.6%.

[0062] The I(003) / I(104) ratio of Comparative Example 1 was 1.28, and the Li / Ni mixing ratio was 5.9%; the I(003) / I(104) ratio of Comparative Example 2 was 1.43, and the Li / Ni mixing ratio was 3.6%; the I(003) / I(104) ratio of Comparative Example 3 was 1.31, and the Li / Ni mixing ratio was 5.2%; the I(003) / I(104) ratio of Comparative Example 4 was 1.34, and the Li / Ni mixing ratio was 4.8%; and the I(003) / I(104) ratio of Comparative Example 5 was 1.37, and the Li / Ni mixing ratio was 4.5%. These results indicate that cation gradient doping and temperature-controlled sintering play a major role in reducing cation mixing, while monolayer coating or water washing cannot effectively improve the bulk structure.

[0063] 2. Morphology, particle size and coating results.

[0064] SEM results show that, Figure 2 The material in Example 1 has clear particle boundaries, with a D50 of 2.1 μm, a D10 of 1.3 μm, and a D90 of 3.4 μm. The particle surface is relatively smooth with few hard agglomerates. Example 2 has a higher nickel content, resulting in a particle D50 of 2.3 μm; Example 3 has a D50 of 2.0 μm; Example 4 uses a reverse microemulsion precursor, resulting in a D50 of 1.8 μm; and Example 5 has a D50 of 2.2 μm. Comparative Example 1 exhibits localized agglomeration with a D50 of 3.0 μm; Comparative Example 4, after water washing and secondary heat treatment, shows slight etching and roughening of the particle surface; Comparative Example 5, due to high-temperature rapid sintering, has a D50 increased to 3.8 μm and exhibits hard agglomerates.

[0065] HRTEM results showed that Example 1 had a continuous coating layer on its surface, with an overall thickness of approximately 8-15 nm. The inner layer, closer to the substrate, was approximately 5-9 nm thick and mainly contained Al, Ti, Zr, and O signals; the outer layer was approximately 2-5 nm thick and contained B, F, and O signals. Example 3 showed a stronger B signal in its outer layer, with a thickness of approximately 4-6 nm. Comparative Example 3 only showed a single layer of Al₂O₃ coating with uneven thickness in some areas; Comparative Example 1 had no continuous protective layer on its surface. These results demonstrate that the present invention can form a bilayer coating structure with different inner and outer functions.

[0066] HRTEM results of Example 4 show that its surface also exhibits a distinguishable inner and outer bilayer coating structure. The inner layer is approximately 3-6 nm thick and mainly contains Al, O, and a small amount of Li signals, which can be classified as a LiAlO2 / Al-O type lithium-ion conductive inner layer; the outer layer is approximately 2-4 nm thick and mainly contains B, F, and O signals, which can be classified as an interface-stabilizing outer layer containing BO and F modulating components. Compared with the monolayer Al2O3 coating of Comparative Example 3, the coating layer of Example 4 exhibits a bilayer characteristic in both composition and spatial distribution, with an inner lithium-conducting layer and an outer interface-stabilizing layer.

[0067] 3. Element distribution and gradient structure results STEM-EDS line scan results showed that in Example 1, Al, Ti, Zr, and Mg elements were detectable both inside the particles and near the surface, with the signal intensity near the surface being higher than that at the particle center; F and B were mainly concentrated on the particle surface and near the surface region. XPS etching depth analysis further showed that the F 1s and B 1s signals were strong before etching and gradually weakened after etching; the Ti 2p and Zr 3d signals were still detectable after etching, but their intensity was lower than that of the surface layer. This result is consistent with the gradient design of "surface strengthening and internal capacity preservation" in this invention. Although Al and Zr signals could be detected in Comparative Example 2, the F 1s and B 1s signals were absent due to the lack of external interface modulators; in Comparative Example 3, Al was mainly concentrated on the surface, with no obvious gradient distribution inside.

[0068] 4. Results of residual alkali and slurry stability, such as Figure 3 As shown.

[0069] Example 1: The material contained 0.12% LiOH, 0.17% Li₂CO₃, and 0.29% total residual alkali. Example 2: Total residual alkali was 0.35%. Example 3: Total residual alkali was 0.30%. Example 4: Total residual alkali was 0.33%. Example 5: Total residual alkali was 0.31%. Comparative Example 1: Total residual alkali was 0.64%. Comparative Example 2: Total residual alkali was 0.55%. Comparative Example 3: Total residual alkali was 0.46%. Comparative Example 4: Total residual alkali after water washing was 0.27%. Comparative Example 5: Total residual alkali was 0.58%.

[0070] It can be seen that the total residual alkali of this invention can approach the level of Comparative Example 4 without traditional water washing. This is not because residual alkali is removed by water washing, but because the precursor reacts with residual lithium, converting some free lithium compounds into stable lithium metal composite oxides. In the slurry stability test, the cathode slurries prepared in Examples 1 to 5 did not show obvious gelation or agglomeration after standing at 25°C for 24 h, and the viscosity growth rate was less than 15%; Comparative Example 1 showed a viscosity growth rate exceeding 45% and slight gelation; Comparative Examples 2 and 3 showed viscosity growth rates of approximately 30% and 25%, respectively; Comparative Example 4 showed good initial slurry stability, but poor cycle performance.

[0071] 5. Initial capacity and initial efficiency results are shown in Table 1.

[0072]

[0073] Table 1 shows the test results of the button cell half-cells. In Example 1, the initial discharge specific capacity at 0.1C was 216.4 mAh / g, and the initial coulombic efficiency was 91.3%; in Example 2, the initial discharge specific capacity was 218.0 mAh / g, and the initial coulombic efficiency was 90.7%; in Example 3, the initial discharge specific capacity was 214.9 mAh / g, and the initial coulombic efficiency was 91.5%; in Example 4, the initial discharge specific capacity was 210.6 mAh / g, and the initial coulombic efficiency was 91.0%; and in Example 5, the initial discharge specific capacity was 212.1 mAh / g, and the initial coulombic efficiency was 91.8%.

[0074] Comparative Example 1 showed an initial discharge specific capacity of 207.2 mAh / g and an initial coulombic efficiency of 88.5%; Comparative Example 2 showed an initial discharge specific capacity of 211.0 mAh / g and an initial coulombic efficiency of 89.8%; Comparative Example 3 showed an initial discharge specific capacity of 208.6 mAh / g and an initial coulombic efficiency of 89.3%; Comparative Example 4 showed an initial discharge specific capacity of 204.8 mAh / g and an initial coulombic efficiency of 88.9%; and Comparative Example 5 showed an initial discharge specific capacity of 205.5 mAh / g and an initial coulombic efficiency of 88.7%. These results demonstrate that the present invention does not significantly sacrifice capacity due to doping and coating; on the contrary, it improves the initial efficiency by reducing mixing and improving the interface.

[0075] 6. Cyclic performance results, such as... Figure 4 As shown.

[0076] Cycling at 2.8–4.3 V, 25 °C, and 1C rate, Example 1 showed a capacity retention of 95.5% after 100 cycles and 92.4% after 200 cycles; Example 2 showed a capacity retention of 93.2% after 100 cycles and 89.6% after 200 cycles; Example 3 showed a capacity retention of 96.1% after 100 cycles and 93.2% after 200 cycles; Example 4 showed a capacity retention of 94.8% after 100 cycles and 91.7% after 200 cycles; and Example 5 showed a capacity retention of 95.2% after 100 cycles and 92.0% after 200 cycles.

[0077] Comparative Example 1 showed a capacity retention rate of 86.5% after 100 cycles and 78.6% after 200 cycles; Comparative Example 2 showed a capacity retention rate of 90.0% after 100 cycles and 85.2% after 200 cycles; Comparative Example 3 showed a capacity retention rate of 89.3% after 100 cycles and 83.8% after 200 cycles; Comparative Example 4 showed a capacity retention rate of 88.0% after 100 cycles and 81.4% after 200 cycles; Comparative Example 5 showed a capacity retention rate of 87.2% after 100 cycles and 80.6% after 200 cycles. These results indicate that, under the above comparative conditions, individual bulk doping, monolayer coating, or conventional water washing all have some improvement or impact on cycling performance, but the overall effect is not as good as the synergistic modification scheme of this invention.

[0078] 7. Ratio performance results, such as Figure 5 As shown.

[0079] In Example 1, the discharge specific capacities at 0.2C, 0.5C, 1C, 2C, and 5C rates were 211.8 mAh / g, 204.5 mAh / g, 197.0 mAh / g, 185.0 mAh / g, and 169.2 mAh / g, respectively. After the rate test, when the capacity recovered to 0.2C, it was 209.0 mAh / g, with a recovery rate of 98.7%. In Example 2, the discharge specific capacity at 5C rate was 166.8 mAh / g; in Example 3, it was 167.5 mAh / g; in Example 4, it was 165.0 mAh / g; and in Example 5, it was 163.8 mAh / g.

[0080] Comparative Example 1 exhibited a discharge specific capacity of 142.5 mAh / g at 5C, Comparative Example 2 153.2 mAh / g, Comparative Example 3 150.6 mAh / g, Comparative Example 4 146.0 mAh / g, and Comparative Example 5 148.4 mAh / g. The materials in these examples demonstrate high capacity at high rates, indicating that the double-layer coating did not significantly impede lithium-ion transport; rather, it improved rate output by reducing side reactions and interfacial impedance.

[0081] 8. EIS impedance results, such as Figure 6 As shown.

[0082] EIS testing showed that the initial charge transfer impedance Rct of Example 1 was 43 Ω, and it was 82 Ω after 100 cycles; the initial Rct of Example 2 was 48 Ω, and it was 91 Ω after 100 cycles; the initial Rct of Example 3 was 45 Ω, and it was 78 Ω after 100 cycles; the initial Rct of Example 4 was 46 Ω, and it was 88 Ω after 100 cycles; and the initial Rct of Example 5 was 41 Ω, and it was 80 Ω after 100 cycles.

[0083] Comparative Example 1 initially had an Rct of 69 Ω, which increased to 166 Ω after 100 cycles; Comparative Example 2 had an Rct of 128 Ω after 100 cycles; Comparative Example 3 had an Rct of 136 Ω after 100 cycles; Comparative Example 4 had an Rct of 151 Ω after 100 cycles; and Comparative Example 5 had an Rct of 145 Ω after 100 cycles. These results indicate that the material of this invention exhibits slow interfacial film growth during cycling, maintains good charge transfer channels, and that the double-layer coating has a direct effect on interfacial stability and improved kinetics.

[0084] 9. Thermal stability results, such as Figure 7 , 8 As shown.

[0085] The exothermic onset temperature and total heat release in DSC vary with electrolyte volume, sample state of charge, heating rate, and sealing conditions. The following data illustrate the relative trends of different samples under the same test conditions. In the DSC test, the main exothermic peak onset temperature of the charged material in Example 1 was 235℃, and the total heat release was approximately 515 J / g; the exothermic peak onset temperature of Example 2 was 230℃, and the total heat release was approximately 548 J / g; the exothermic peak onset temperature of Example 3 was 238℃, and the total heat release was approximately 500 J / g; the exothermic peak onset temperature of Example 4 was 232℃, and the total heat release was approximately 535 J / g; and the exothermic peak onset temperature of Example 5 was 240℃, and the total heat release was approximately 492 J / g.

[0086] Comparative Example 1 had a main exothermic peak at an onset temperature of 208℃, with a total exothermic heat of approximately 725 J / g; Comparative Example 2 had an onset temperature of 218℃, with a total exothermic heat of approximately 650 J / g; Comparative Example 3 had an onset temperature of 216℃, with a total exothermic heat of approximately 668 J / g; Comparative Example 4 had an onset temperature of 212℃, with a total exothermic heat of approximately 690 J / g; and Comparative Example 5 had an onset temperature of 214℃, with a total exothermic heat of approximately 675 J / g. These results demonstrate that the present invention, by improving lattice oxygen stability through bulk doping and reducing direct electrolyte contact through outer coating, can delay the exothermic reaction and reduce the total exothermic heat.

[0087] 10. Morphological results after cycling After 200 cycles at 1C, the batteries were disassembled and the morphology of the cathode material was observed. In Examples 1 to 5, the overall particle morphology remained good, with only a few minor cracks on the surface and no large-area pulverization. In Comparative Example 1, more particle cracking and localized pulverization were observed. In Comparative Example 4, the etched area on the surface was more prone to cracking after cycling. In Comparative Example 5, due to the larger grains and discontinuous coating layer, the particle edges showed more significant breakage after cycling. These results are consistent with the cycle retention data, indicating that the small-particle-size single-crystal / quasi-single-crystal structure and gradient modification of this invention can reduce stress concentration.

[0088] The above embodiments only illustrate one or more implementations of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of protection of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A modified high-nickel ternary lithium-ion battery cathode material, wherein the modified high-nickel ternary lithium-ion battery cathode material comprises a matrix and a coating layer wrapped around the surface of the matrix, characterized in that: The chemical formula of the matrix is ​​LiNi x Co y Mn 1-x- y O2 or LiNi x Co y Al 1-x-y O2, wherein 0.80≤x≤0.95, 0.03≤y≤0.15, and 0<1-xy≤0.17; the matrix further includes cation doping elements and anion doping elements; the cation doping elements include one or more of Ti, Zr, Al, Na, Mg, and W, and the total content of the cation doping elements is 0.05~1.5 mol% based on the total molar amount of transition metals; the anion doping elements include one or more of F, Cl, S, B, or P, and the total content of the anion doping elements is 0.02~1.0 mol% based on the total molar amount of theoretical oxygen sites in the matrix; the coating layer includes Li2ZrO3, LiAlO2, Li2TiO3, and Li4Ti5O3. 12 One or more of Al2O3, TiO2, ZrO2, boron oxides, borates, metal fluorides, or metal oxyfluorides.

2. The modified high-nickel ternary lithium-ion battery cathode material according to claim 1, characterized in that, The doping concentration of the cation dopant element in the matrix particles decreases from the surface to the interior.

3. The modified high-nickel ternary lithium-ion battery cathode material according to claim 1, characterized in that, The coating layer has a double-layer structure; the first coating layer includes one or more of Li2ZrO3, LiAlO2 or other Li-Ti-O type lithium titanium composite oxides, with a thickness of 2 to 10 nm; the second coating layer includes one or more of Al2O3, B2O3, TiO2, ZrO2, borate, metal fluoride or metal oxyfluoride, with a thickness of 1 to 8 nm.

4. The modified high-nickel ternary lithium-ion battery cathode material according to claim 3, characterized in that, The second coating layer contains both elements B and F, wherein the mass ratio of B to F is 2:1 to 8:

1.

5. The modified high-nickel ternary lithium-ion battery cathode material according to claim 1, characterized in that, The cathode material has a single crystal or near-single crystal morphology, wherein D50 is 1.5–2.5 μm and D90 is no greater than 4.0 μm.

6. A method for preparing the modified high-nickel ternary lithium-ion battery cathode material according to any one of claims 1-5, characterized in that, Includes the following steps: S1. A modified mixture is prepared by mixing a nano-sized high-nickel ternary precursor obtained by co-precipitation, nano-phase separation or reverse microemulsion with a lithium source and a dopant. S2. The modified mixture is placed in an oxygen atmosphere and subjected to segmented heating and sintering and programmed cooling to complete lithiation, element doping solid solution and grain growth, and obtain a single crystal or near-single crystal structure intermediate product. S3. The intermediate product is mixed and sintered with the coating precursor to obtain a modified high-nickel ternary lithium-ion battery cathode material with uniform particle size.

7. The preparation method according to claim 6, characterized in that, In step S1, the molar ratio of the lithium source to the transition metal in the nanoscale high-nickel ternary precursor is 1.05:1 to 1.08:

1.

8. The preparation method according to claim 6, characterized in that, In step S1, the dopant includes a cationic dopant and anionic / nonmetallic dopant; the cationic dopant is selected from at least one of ZrO2, TiO2, Na2CO3, Al2O3, MgO, and WO3; the anionic / nonmetallic dopant is selected from at least one of H3BO3, LiF, NH4F, NH4H2PO4, and Li3PO4.

9. The preparation method according to claim 6, characterized in that, The segmented heating and cooling process in step S2 is as follows: heating at 2-5℃ / min to 450-500℃ and holding for 2-5 hours; then heating at 2-5℃ / min to 780-820℃ and holding for 10-20 hours; then cooling at 2-5℃ / min to 600℃ and holding for 2 hours; then cooling to 300℃ and holding for 1 hour; and finally cooling with the furnace.

10. The preparation method according to claim 6, characterized in that, The mixing and sintering in step S3 is a two-stage sintering process. Under an oxygen atmosphere, the first coating precursor is first mixed with the intermediate product and reacted at 500-600°C for 3-5 hours. Then, the second coating precursor is added and reacted at 300-400°C for 3-5 hours. The first coating precursor is selected from at least one of Al2O3, TiO2, ZrO2, aluminum isopropoxide, tetrabutyl titanate, and zirconium source. The second coating precursor is selected from at least one of H3BO3, LiF, NH4F, NH4H2PO4, and fluoroborate.

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