A fluorocarbon doped modified lithium ion battery ternary cathode material, a preparation method thereof and a battery

Abstract

The application discloses fluorocarbon doped modified lithium ion battery ternary positive electrode material and a preparation method and a battery thereof. 0.838 Co 0.114 Mn 0.048 (OH)2 and LiOH·H2O are mixed and ground, sintering is carried out to obtain high-nickel positive electrode material NCM; the high-nickel positive electrode material is mixed with polyvinylidene fluoride and then is dissolved in anhydrous ethanol, water bath heating and stirring are carried out to obtain a gel-like material; the gel-like material is vacuum dried, is ground to obtain a solid powder, and then is subjected to second sintering in an inert gas atmosphere to obtain the fluorocarbon doped modified lithium ion battery ternary positive electrode material. The application adopts a double-modification method of doping and coating, and uses a high-temperature solid phase method to prepare the fluorocarbon doped modified ternary positive electrode material; under high cut-off voltage, F doping can form TM-F bonds with higher bond energy, has the advantages of improving the cycle performance and rate performance of the NCM material, and improves the structural stability and electrochemical performance of the high-nickel positive electrode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology. More specifically, this invention relates to a fluorine-carbon doped modified ternary cathode material for lithium-ion batteries, its preparation method, and the battery itself. Background Technology

[0002] The core components of a lithium-ion battery mainly include the positive electrode, negative electrode active materials, electrolyte, ion-conducting membrane, and safety protection circuit. The positive electrode materials for lithium-ion batteries mostly use lithium metal oxides (such as LiCoO2, LiMn2O4) or nickel-cobalt-manganese ternary composite materials (LiNi). x Co y Mn z O2). The negative electrode is a graphitized carbon-based lithium intercalation compound (Li). x C6). The electrolyte is typically composed of dissolved lithium salt (LiPF6) in a non-protic organic solvent system (such as carbonates), forming an ion-conducting network. The separator is mainly a polyethylene / polypropylene composite separator with ion-conducting and electronic insulation properties, where the multilayer composite structure effectively counteracts both the thermal pore effect and the mechanical strength. A safety protection circuit constantly monitors voltage and temperature to prevent overvoltage or overheating, which could lead to thermal runaway. Through these components, lithium ions can reversibly insert and extract into the electrolyte. The working principle of a lithium-ion battery is based on lithium ions (Li...). + The lithium ions move back and forth between the positive and negative electrodes. The carbon layer at the negative electrode has a layered structure with many micropores. Lithium ions that reach the negative electrode embed themselves in these micropores; the more lithium ions embedded, the higher the charging capacity. Similarly, when the battery is discharged (i.e., when we use the battery), the lithium ions embedded in the carbon layer at the negative electrode are released and move back to the positive electrode. The more lithium ions that return to the positive electrode, the higher the discharge capacity.

[0003] Cathode materials are a core component of lithium-ion batteries, significantly influencing their core performance indicators. The energy density of the cathode material directly affects battery performance; both capacity and voltage jointly determine the energy density. Currently, the main structures of developed lithium-ion battery cathode materials include spinel-structured transition metal compounds, olivine-structured polyanionic compounds, and ternary layered transition metal compounds. Among these, layered materials primarily refer to lithium-containing layered oxides dominated by transition metals such as Ni, Co, and Mn. The preparation methods for ternary high-nickel cathode materials mainly include co-precipitation, high-temperature solid-state methods, hydrothermal methods, and sol-gel methods.

[0004] In nickel-cobalt-manganese ternary compound materials, Ni exhibits a mixed valence state of +2 and +3. If some trivalent Ni positions are occupied by divalent Ni, some divalent Ni will occupy some Li+ positions in the crystal lattice to balance the charge. Because Ni... 2+The ionic radius (0.068 nm) and Li + The similarity in size (0.076nm) between the lithium and nickel ions reduces the interplanar spacing, leading to lithium-nickel mixing. Furthermore, during charging, divalent nickel is oxidized to trivalent or tetravalent nickel. As nickel ions lose electrons, their ionic radius decreases, further reducing the interplanar spacing and causing lattice collapse, resulting in lattice defects. During discharge, the released lithium ions cannot fully occupy their original lattice sites, affecting the battery's cycle performance. This cation migration can occur during synthesis or charge-discharge cycling, ultimately leading to poor thermal stability and rate performance.

[0005] In the preparation of layered oxide cathodes based on nickel-cobalt-manganese layers, an excess lithium source strategy is often employed to offset the thermal loss of Li+ during high-temperature solid-state sintering. This stoichiometric control effectively suppresses the disordered cation occupancy between transition metal layers. However, a large amount of residual lithium adheres to the surface of the ternary cathode material. This residual lithium reacts with CO2 and H2O in the air to form surface residual alkaline compounds, primarily composed of LiOH and Li2CO3. These surface residual alkaline components have multiple effects on the electrochemical degradation mechanism of layered cathode materials: the presence of alkaline substances (such as Li2CO3 / LiOH) accelerates lithium-ion transport kinetics and induces the reduction of nickel oxidation state (Ni...). 3+ →Ni 2+ This exacerbates the disordered cation occupancy of the transition metal and lithium layers. During high-potential cycling, LiOH reacts with LiPF6 in the electrolyte to generate corrosive HF. This acidic medium not only reacts with Li2CO3 to release CO2, leading to deterioration of cycle stability, but also triggers irreversible dissolution of transition metals (Ni / Co / Mn). Furthermore, these residual alkaline compounds increase the alkalinity of the material and cause gelation of the slurry. The above synergistic effects lead to problems such as layered structure degradation, increased interfacial impedance, and rapid capacity decay. Simultaneously, an electrolyte interphase (SEI) film forms on the surface of the high-nickel ternary cathode material during charge and discharge. However, the SEI layer may become unstable under high voltage and cycling, easily dissolving, cracking, or recombining, thus affecting lithium-ion migration and charge transfer. The SEI layer mainly forms during the first charge of the battery and is a product of the side reaction between the electrolyte and the cathode material. It is mainly composed of inorganic salts (such as Li2CO3) and organic decomposition products, and its purpose is to protect the electrode material and prevent further side reactions. Under high voltage conditions, the electrolyte decomposition reaction accelerates, generating more corrosive byproducts. These byproducts erode the SEI layer, causing some components in the SEI layer, such as lithium carbonate (Li2CO3), to dissolve or decompose, making the SEI layer porous and uneven, thereby weakening its protective effect on the cathode material.

[0006] LiNi0.8 Co 0.1 Mn 0.1 The high nickel content in O2 material enables the transition metal layer Li⁺ / Ni 2+ Increased site disorder leads to kinetic barriers in the Ni3+ / Ni4+ redox reaction during delithiation, resulting in insufficient charge compensation and irreversible capacity loss. Secondly, surface Ni2+ enrichment forms a rock-salt passivation layer, significantly inhibiting lithium-ion diffusion kinetics and exacerbating electrochemical polarization. Furthermore, the synergistic effect of layered-spinel phase transition induced by lattice oxygen release under high charge states and anisotropic volumetric strain triggers microcrack propagation and structural collapse within the particles. Simultaneously, intensified interfacial side reactions under high voltage easily form an unstable solid electrolyte interphase (SEI) layer, further reducing battery cycle life and performance. These factors collectively contribute to the low initial coulombic efficiency, rapid capacity decay rate, and deteriorated rate performance of this layered oxide system. Under high-voltage cycling conditions, lattice stress accumulation further amplifies cation mixing and structural degradation effects. To address the challenges of high-nickel ternary cathode materials under high voltage, numerous studies have proposed various modification methods, such as doping, surface coating, electrolyte optimization, and composite modification.

[0007] Among various cathode materials, high-nickel ternary cathode materials have become a key choice for achieving breakthroughs in battery energy density due to their high specific capacity (>200mAh / g) and high operating voltage (>3.8V). However, structural instability and severe interfacial side reactions lead to insufficient kinetic performance of high-nickel ternary cathode materials. Furthermore, under high cutoff voltages, high-nickel ternary cathode materials experience capacity decay due to lattice oxygen precipitation and layered structure collapse. Simultaneously, the electrolyte readily undergoes oxidation reactions on the cathode surface, generating corrosive products such as HF and CO2. The thick and uneven cathode-electrolyte interface (CEI) layer (reaching 15-20nm in thickness) formed by these side reactions significantly increases interfacial impedance, hindering lithium-ion transport. In addition, high-nickel ternary cathode materials exhibit significantly lower thermal runaway initiation temperatures under high voltages, exacerbating the risk of battery thermal runaway. Summary of the Invention

[0008] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0009] To achieve these and other advantages according to the present invention, the present invention provides a method for preparing a fluorine-carbon doped modified ternary cathode material for lithium-ion batteries, comprising the following steps:

[0010] Step 1: Using Ni 0.838 Co 0.114 Mn 0.048 (OH)2 and LiOH·H2O were mixed, ground, and sintered to obtain a high-nickel cathode material;

[0011] Step 2: Grind and mix the high-nickel cathode material with polyvinylidene fluoride, then dissolve it in anhydrous ethanol, heat in a water bath, and stir to obtain a gel-like material; vacuum dry the gel-like material and grind it to obtain a solid powder, then sinter it a second time under an inert gas atmosphere to obtain a fluorine-carbon doped modified lithium-ion battery ternary cathode material.

[0012] Preferably, in step one, Ni 0.838 Co 0.114 Mn 0.048 The molar ratio of (OH)2 to LiOH·H2O is 1:1~1.1.

[0013] Preferably, in step one, the sintering atmosphere is an oxygen atmosphere, and the sintering heating program is as follows: heating from 25°C to 150°C at a heating rate of 5°C / min, holding for 40-50 min; then heating to 500°C at a heating rate of 2°C / min, holding for 300 min; heating to 850°C at a heating rate of 4°C / min, holding for 300 min; then cooling to 780°C at a cooling rate of 2°C / min, holding for 600 min; and finally cooling to room temperature at a cooling rate of 5°C / min.

[0014] Preferably, in step two, polyvinylidene fluoride accounts for 1 wt% to 3 wt% of the mass of the high-nickel cathode material.

[0015] Preferably, in step two, the water bath heating temperature is 70~90℃ and the vacuum drying time is 10~16h.

[0016] Preferably, in step one, the sintering atmosphere is an oxygen atmosphere, and the sintering heating program is as follows: heating from 25°C to 150°C at a heating rate of 2-5°C / min, holding for 40-50 min; then heating to 500°C at a heating rate of 2-5°C / min, holding for 300 min; heating to 850°C at a heating rate of 2-5°C / min, holding for 300 min; then cooling to 780°C at a cooling rate of 2°C / min, holding for 600 min; and finally cooling to room temperature at a cooling rate of 2-5°C / min.

[0017] Preferably, the fluorine-carbon doped modified lithium-ion battery ternary cathode material is internally doped with fluorine and has a fluorine-carbon coating on its surface.

[0018] Preferably, step two further includes coating the fluorocarbon-doped modified lithium-ion battery ternary cathode material with a double layer of aluminum oxide and magnesium oxide, and the fluorocarbon-doped modified lithium-ion battery ternary cathode material is designated as NCM-FC. The specific method includes:

[0019] S21. Dissolve aluminum isopropoxide in anhydrous ethanol, stir in a water bath at 50-60°C for 10-30 min, add acetylacetone; adjust the pH of the solution to 3.0-4.0 by adding 0.1M nitric acid dropwise, stirring to obtain a transparent sol; disperse NCM-FC in anhydrous ethanol, add the transparent sol dropwise, and stir at 500-600 rpm for 20-30 min after the addition is complete; heat in a water bath at 50-70°C for 2-6 h; allow to stand and age at room temperature for 12-24 h, evaporate to remove ethanol, and vacuum dry at 80-90°C for 2-12 h to obtain an aluminum oxide coating layer on the surface of NCM-FC, thus obtaining Al2O3@NCM-FC;

[0020] S22. Place Al2O3@NCM-FC in an oxygen plasma reactor and set the vacuum level to ≤1.2×10⁻⁶. -5 Under a pressure of 150-200 W and an oxygen flow rate of 30-50 sccm, oxygen plasma was applied to the alumina coating layer on the surface of Al2O3@NCM-FC for 5-10 min to activate the alumina coating layer. The activated Al2O3@NCM-FC was then immersed in a lithium dihydrogen phosphate solution, and a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer was added. After holding at 25°C for 30 min, the pressure was increased to 1.5 MPa and the temperature was raised to 80°C for 1-2 h. Then, the temperature was raised to 120°C and held for 1 h. The mixture was then cooled to room temperature. The mixture was then heat-treated at 300°C for 1 h in a tube furnace under a nitrogen atmosphere. After cooling, Li3PO4 nanopillar-embedded Al2O3@NCM-FC was obtained.

[0021] S23. Magnesium nitrate hexahydrate was dissolved in deionized water, citric acid and ethylene glycol were added, and trimethyl borate was used as a stabilizer. The mixture was stirred at 60°C to obtain a viscous sol. Al2O3@NCM-FC embedded with Li3PO4 nanopillars was immersed in the sol and dispersed by ultrasonication at 50kHz for 20 min. The temperature was then raised to 60~90°C and held for 2 h. After cooling to room temperature, the mixture was allowed to stand for 12 h. After solid-liquid separation, washing and drying were performed. The solid was placed in a tube furnace and heated to 350°C under a nitrogen atmosphere for 2 h. The temperature was then raised to 500°C and held for 30 min. After cooling, the solid was removed to obtain MgO@Al2O3@NCM-FC with a double layer of alumina and magnesium oxide.

[0022] Preferably, in step S21, the ratio of aluminum isopropoxide, anhydrous ethanol, and acetylacetone is 2-5g:100-200mL:0.2-0.5g; and the ratio of NCM-FC, anhydrous ethanol, and transparent sol is 1-2g:10-20mL:10-20mL.

[0023] In S22, the ratio of activated Al2O3@NCM-FC, lithium dihydrogen phosphate solution, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is 5~10g:50~200mL:0.5~1g;

[0024] In S23, the ratio of magnesium nitrate hexahydrate, deionized water, citric acid, ethylene glycol, trimethyl borate, and Li3PO4 nanopillar-embedded Al2O3@NCM-FC is 1~3g:50~100mL:1~2g:3~5mL:1~3mL:5~10g.

[0025] A battery is prepared by the above-mentioned method for preparing fluorine-carbon doped modified lithium-ion battery ternary cathode material.

[0026] The present invention has at least the following beneficial effects: The present invention adopts a dual modification method of doping and coating, and uses a high-temperature solid-state method to prepare fluorocarbon doped modified ternary cathode materials. Under high cutoff voltage, F doping will form TM-F bonds with higher bond energy, which has the advantages of improving the cycle performance and rate performance of NCM materials, and improving the structural stability and electrochemical performance of high nickel cathode materials.

[0027] This invention, based on fluorocarbon doping modification and fluorocarbon coating of high-nickel cathode materials, further applies a double-layer coating of alumina and magnesium oxide to prepare a fluorocarbon-doped modified ternary cathode material for lithium-ion batteries with a more stable structure and superior charge-discharge specific capacity and electrochemical performance. Specifically, Li3PO4 nanopillars, formed by a template agent (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer), are embedded in the Al2O3 coating layer between the alumina and magnesium oxide coating layers. The Li3PO4 nanopillar structure can construct continuous lithium-ion transport channels within the Al2O3 layer, significantly reducing the lithium ion transport capacity. + Diffusion resistance in the coating layer. This structure allows for more Li + It can efficiently migrate to the NCM-FC bulk to participate in the insertion / extraction reaction, directly improving the charge / discharge specific capacity; at the same time, the continuous ion channels accelerate the Li + The conductivity rate is increased, enhancing the ionic conductivity of the material. Oxygen plasma, acting on the Al2O3 coating surface, introduces oxygen vacancies and surface defects through high-energy particle interaction, increasing the surface activity and lithium-ion affinity of the Al2O3 layer. These active sites promote the interfacial bonding between the Li3PO4 nanopillars and the Al2O3 layer, reducing interfacial resistance; simultaneously, the defect sites on the Al2O3 surface provide Li... + Provides more migration paths and reduces Li + The migration energy barrier at the interface between the Al2O3 layer and the NCM-FC matrix. This not only enhances the Li +The Al2O3 layer not only improves the utilization rate (increasing the specific capacity of charge and discharge) but also reduces energy loss during charge transfer and enhances conductivity. It also provides initial isolation between the electrolyte and the NCM-FC bulk, inhibiting the dissolution of transition metals (Ni, Co, Mn) and the corrosion and decomposition of the cathode material by the electrolyte. The MgO outer coating further enhances the barrier effect against the electrolyte, while its weak alkalinity neutralizes any HF that may be generated in the electrolyte, reducing corrosion of the cathode material and thus improving the cycle performance and rate performance of the cathode material.

[0028] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0029] Figure 1 XRD patterns of NCM-FC0%, NCM-FC1%, NCM-FC2% and NCM-FC3% prepared in Examples 1-3;

[0030] Figure 2 SEM image of NCM-FC0% prepared in Example 1;

[0031] Figure 3 SEM image of NCM-FC2% prepared in Example 2;

[0032] Figure 4 Charge-discharge curves at 0.1C for NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% prepared in Examples 1-3;

[0033] Figure 5 Rate curves for NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% prepared in Examples 1-3;

[0034] Figure 6 The capacity retention of NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% prepared in Examples 1-3 after 100 cycles at 1C and within the range of 2.7V to 4.3V;

[0035] Figure 7 CV curves of NCM-FC0% prepared in Example 1 after 2 and 3 cycles;

[0036] Figure 8 CV curves of NCM-FC2% prepared in Example 2 after 2 and 3 cycles;

[0037] Figure 9AC impedance diagrams of NCM-FC0%, NCM-FC1%, NCM-FC2% and NCM-FC3% prepared in Examples 1-3;

[0038] Figure 10 The ω-FCs prepared in Examples 1-3 were 0% NCM-FC, 1% NCM-FC, 2% NCM-FC, and 3% NCM-FC. -1 / 2 The fitted curve of -Z';

[0039] Figure 11 Charge-discharge curves of NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% prepared in Examples 1-3 in the range of 0.1C and 2.7V~4.5V;

[0040] Figure 12 Rate performance of NCM-FC0%, NCM-FC1%, NCM-FC2% and NCM-FC3% prepared in Examples 1-3 in the range of 2.7V to 4.5V;

[0041] Figure 13 The capacity retention of NCM-FC0%, NCM-FC1%, NCM-FC2% and NCM-FC3% prepared in Examples 1-3 after 100 cycles at 1C and within the range of 2.7V to 4.5V;

[0042] Figure 14 The first three CV curves of NCM-FC0% prepared in Example 1;

[0043] Figure 15 The first three CV curves of NCM-FC2% prepared in Example 2;

[0044] Figure 16 AC impedance diagrams of NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% prepared in Examples 1-3 in the range of 2.7V to 4.5V;

[0045] Figure 17 The NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% prepared in Examples 1-3 have ω values ​​in the range of 2.7V to 4.5V. -1 / 2 The fitted curve of -Z'. Detailed Implementation

[0046] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0047] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0048] Example 1

[0049] A method for preparing a fluorine-carbon doped modified ternary cathode material for lithium-ion batteries includes the following steps:

[0050] Step 1: Weigh 5.0000g of Ni using an electronic balance. 0.838 Co 0.114 Mn 0.048 (OH)₂ (analytical grade, purchased from Guangdong Zhuguang New Energy Technology Co., Ltd.), according to Ni 0.838 Co 0.114 Mn 0.048 Weigh out LiOH·H2O with a molar ratio of (OH)2 to LiOH·H2O of 1:1.05, and add Ni 0.838 Co 0.114 Mn 0.048 (OH)₂ and LiOH·H₂O were ground in an agate mortar for 30 min, and then placed in a tube furnace under an oxygen atmosphere for sintering according to the following program: the temperature was increased from 25℃ to 150℃ at a heating rate of 3℃ / min and held for 45 min; then the temperature was increased to 500℃ at a heating rate of 2℃ / min and held for 300 min; then the temperature was increased to 850℃ at a heating rate of 4℃ / min and held for 300 min; then the temperature was decreased to 780℃ at a cooling rate of 2℃ / min and held for 600 min; finally, the temperature was decreased to room temperature at a cooling rate of 5℃ / min. The high-nickel cathode material was obtained by sintering and was designated as NCM-FC0%.

[0051] Step 2: Grind the high-nickel cathode material (NCM-FC0%) and 1 wt% polyvinylidene fluoride (PVDF) in an agate mortar for 30 min. After grinding and mixing, dissolve the mixture in 200 mL of anhydrous ethanol. Heat the mixture in a water bath to 80 °C and stir until the solution becomes gel-like. Vacuum dry the gel-like material for 12 h and grind it to obtain a uniformly mixed solid powder. Under a nitrogen atmosphere, the sintering temperature program is as follows: heat the material from 25 °C to 150 °C at a heating rate of 3 °C / min and hold for 30 min; then heat the material to 450 °C at a heating rate of 2 °C / min and hold for 3 h; finally, cool the material to room temperature at a cooling rate of 5 °C / min to obtain the fluorine-carbon doped modified lithium-ion battery ternary cathode material, denoted as NCM-FC1.

[0052] Example 2

[0053] A method for preparing a fluorocarbon-doped modified ternary cathode material for lithium-ion batteries, which differs from Example 1 in that the amount of polyvinylidene fluoride used in this example is 2 wt% of the mass of the high-nickel cathode material, and the process parameters of the remaining steps in this example are the same as those in Example 1; the fluorocarbon-doped modified ternary cathode material for lithium-ion batteries obtained in this example is referred to as NCM-FC2.

[0054] Example 3

[0055] A method for preparing a fluorocarbon-doped modified ternary cathode material for lithium-ion batteries, which differs from Example 1 in that the amount of polyvinylidene fluoride used in this example is 3 wt% of the mass of the high-nickel cathode material. The process parameters of the remaining steps in this example are the same as those in Example 1. The fluorocarbon-doped modified ternary cathode material for lithium-ion batteries obtained in this example is referred to as NCM-FC3.

[0056] Example 4

[0057] A method for preparing a fluorocarbon-doped modified ternary cathode material for lithium-ion batteries, which differs from Example 2 in that the NCM-FC2% is coated with a double layer of aluminum oxide and magnesium oxide, specifically including:

[0058] S21. Dissolve 5g of aluminum isopropoxide in 150mL of anhydrous ethanol, stir in a water bath at 60℃ for 20min, add 0.3g of acetylacetone; adjust the pH of the solution to 3.0 by adding 0.1M nitric acid dropwise, stirring to obtain a transparent sol; disperse 10g of NCM-FC2% in 100mL of anhydrous ethanol, add 100mL of the transparent sol dropwise, and stir at 600rpm for 0min after the addition is complete; heat in a water bath at 55℃ for 3h; allow to stand and age at room temperature for 12h, evaporate to remove ethanol, and vacuum dry at 80℃ for 3h to obtain an aluminum oxide coating layer on the surface of NCM-FC, i.e., Al2O3@NCM-FC2%;

[0059] S22. Place Al2O3@NCM-FC2% in an oxygen plasma reactor and set the vacuum level to 1.2 × 10⁻⁶. -5At a power of 150W and an oxygen flow rate of 30sccm, oxygen plasma was applied to the alumina coating layer on the surface of Al2O3@NCM-FC for 5 minutes to activate the alumina coating layer. 10g of the activated Al2O3@NCM-FC2% was immersed in 150mL of 5wt% lithium dihydrogen phosphate solution (containing 1g of lithium acetylacetone), and 0.5g of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer was added as a template agent. After holding at 25℃ for 30 minutes, the pressure was increased to 1.5MPa and the temperature was raised to 80℃ and held for 2 hours. Then, the temperature was raised to 120℃ and held for 1 hour, followed by cooling to room temperature. The mixture was then heat-treated at 300℃ for 1 hour in a tube furnace under a nitrogen atmosphere. After cooling, Li3PO4 nanopillar-embedded Al2O3@NCM-FC2% was obtained.

[0060] S23. Dissolve 1.5g magnesium nitrate hexahydrate in 50mL deionized water, add 2g citric acid and 3mL ethylene glycol, and 2mL trimethyl borate as a stabilizer. Stir at 60℃ to obtain a viscous sol. Immerse 10g of Li3PO4 nanopillars embedded with Al2O3@NCM-FC2% into the sol. After ultrasonic dispersion at 50kHz for 20min, heat to 80℃ and hold for 2h. After cooling to room temperature, let stand for 12h. After solid-liquid separation, wash and dry, place the solid in a tube furnace, heat to 350℃ under nitrogen atmosphere and hold for 2h. Then heat to 500℃ and hold for 30min. After cooling, take out to obtain MgO@Al2O3@NCM-FC2% with alumina and magnesium oxide double coating.

[0061] The process parameters for the remaining steps in this embodiment are the same as those in Embodiment 2.

[0062] Example 5

[0063] A method for preparing a fluorocarbon-doped modified ternary cathode material for lithium-ion batteries, which differs from Example 2 in that the NCM-FC2% is coated with a double layer of aluminum oxide and magnesium oxide, specifically including:

[0064] S21. Dissolve 5g of aluminum isopropoxide in 150mL of anhydrous ethanol, stir in a water bath at 60℃ for 20min, add 0.3g of acetylacetone; adjust the pH of the solution to 3.0 by adding 0.1M nitric acid dropwise, stirring to obtain a transparent sol; disperse 10g of NCM-FC2% in 100mL of anhydrous ethanol, add 120mL of the transparent sol dropwise, and stir at 600rpm for 0min after the addition is complete; heat in a water bath at 55℃ for 3h; allow to stand and age at room temperature for 12h, evaporate to remove ethanol, and vacuum dry at 80℃ for 3h to obtain an aluminum oxide coating layer on the surface of NCM-FC2%, thus obtaining Al2O3@NCM-FC2%;

[0065] S22. Place Al2O3@NCM-FC2% in an oxygen plasma reactor and set the vacuum level to 1.2 × 10⁻⁶. -5 At a power of 150W and an oxygen flow rate of 30sccm, oxygen plasma was applied to the alumina coating layer on the surface of Al2O3@NCM-FC2% for 5 minutes to activate the alumina coating layer. 10g of the activated Al2O3@NCM-FC2% was then immersed in 100mL of a 5wt% lithium dihydrogen phosphate solution (containing 0.3g of lithium acetylacetone). 0.5g of a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer was added as a template agent. The mixture was held at 25℃ for 30 minutes, then pressurized to 1.5MPa and heated to 80℃ for 2 hours. The temperature was then increased to 120℃ and held for 1 hour, followed by cooling to room temperature. The mixture was then heat-treated at 300℃ for 1 hour in a tube furnace under a nitrogen atmosphere. After cooling, Li3PO4 nanopillars embedded in Al2O3@NCM-FC2% were obtained.

[0066] S23. Dissolve 1.5g magnesium nitrate hexahydrate in 80mL deionized water, add 2g citric acid and 3mL ethylene glycol, and 3mL trimethyl borate as a stabilizer. Stir at 60℃ to obtain a viscous sol. Immerse 10g of Li3PO4 nanopillar-embedded Al2O3@NCM-FC2% into the sol. After ultrasonic dispersion at 50kHz for 20min, heat to 90℃ and hold for 2h. After cooling to room temperature, let stand for 12h. After solid-liquid separation, wash and dry, place the solid in a tube furnace, heat to 350℃ under nitrogen atmosphere and hold for 2h. Then heat to 500℃ and hold for 30min. After cooling, take out to obtain MgO@Al2O3@NCM-FC2% double-layer coated with alumina and magnesium oxide.

[0067] The process parameters for the remaining steps in this embodiment are the same as those in Embodiment 2.

[0068] Comparative Example 1

[0069] A method for preparing a fluorocarbon-doped modified ternary cathode material for lithium-ion batteries, which differs from Example 2 in that the NCM-FC2% is coated with a double layer of aluminum oxide and magnesium oxide, specifically including:

[0070] S21. Dissolve 5g of aluminum isopropoxide in 150mL of anhydrous ethanol, stir in a water bath at 60℃ for 20min, add 0.3g of acetylacetone; adjust the pH of the solution to 3.0 dropwise by adding 0.1M nitric acid, stirring to obtain a transparent sol; disperse 10g of NCM-FC2% in 100mL of anhydrous ethanol, add 100mL of the transparent sol dropwise, and stir at 600rpm for 0min after the addition is complete; heat in a water bath at 55℃ for 3h; allow to stand and age at room temperature for 12h, evaporate to remove ethanol, and vacuum dry at 80℃ for 3h to obtain an aluminum oxide coating layer on the surface of NCM-FC2%, i.e., Al2O3@NCM-FC2%;

[0071] S22. Dissolve 1.5g magnesium nitrate hexahydrate in 50mL deionized water, add 2g citric acid and 3mL ethylene glycol, and 2mL trimethyl borate as a stabilizer. Stir at 60℃ to obtain a viscous sol. Immerse 10g Al2O3@NCM-FC2% into the sol, disperse by ultrasonication at 50kHz for 20min, then heat to 90℃ and hold for 2h. After cooling to room temperature, let stand for 12h. After solid-liquid separation, wash and dry, place the solid in a tube furnace, heat to 350℃ under a nitrogen atmosphere and hold for 2h, then heat to 500℃ and hold for 30min. After cooling, take out to obtain MgO@Al2O3@NCM-FC2% double-layer coated with alumina and magnesium oxide.

[0072] The process parameters for the remaining steps in this comparative example are the same as those in Example 2.

[0073] Comparative Example 2

[0074] A method for preparing a fluorine-carbon doped modified ternary cathode material for lithium-ion batteries, which differs from Example 2 in that the NCM-FC2% is coated with magnesium oxide, and the specific method includes:

[0075] 1.5 g of magnesium nitrate hexahydrate was dissolved in 50 mL of deionized water. 2 g of citric acid and 3 mL of ethylene glycol were added, along with 2 mL of trimethyl borate as a stabilizer. The mixture was stirred at 60 °C to obtain a viscous sol. 10 g of NCM-FC2% was immersed in the sol and ultrasonically dispersed at 50 kHz for 20 min. The mixture was then heated to 90 °C and held for 2 h. After cooling to room temperature, it was allowed to stand for 12 h. After solid-liquid separation, washing and drying were performed. The solid was placed in a tube furnace and heated to 350 °C under a nitrogen atmosphere for 2 h. The temperature was then increased to 500 °C and held for 30 min. After cooling, the solid was removed to obtain magnesium oxide-coated MgO@NCM-FC2%.

[0076] The process parameters for the remaining steps in this comparative example are the same as those in Example 2.

[0077] The fluorocarbon-doped modified lithium-ion battery ternary cathode materials prepared in the above embodiments and comparative examples were used to make motors and assembled into batteries. Specifically, 0.8000 g of fluorocarbon-doped modified lithium-ion battery ternary cathode material, 0.1000 g of conductive carbon black (baked in a vacuum oven for 2 h before use), and 2.0000 g of adhesive solution were weighed into a mixing bottle. Then, 1000 μL of N-methylpyrrolidone (NMP) was added to the mixture using a pipette. The mixture was then placed on a magnetic stirrer and stirred at 500 r / min for 12 h. Afterward, lithium-ion separators of appropriate size were cut, placed between folded pieces of clean paper, and pressed out using a tablet press. The separators that were flat, smooth, and free of marks and impurities were selected using tweezers. Cut 12 cm long, crease-free aluminum foil. Open the coating machine, place the cut aluminum foil on it, wipe the surface clean with alcohol-soaked paper, turn on the suction switch, place the 200 μm scraper in front of the stop bar, pour the prepared slurry onto the aluminum foil, start the instrument, and wait for coating to complete. After coating, place it in a 105℃ vacuum oven and dry for 6 hours. After drying, slice the aluminum foil using a sheet press, weigh it, select uniform, impurity-free electrode sheets, place them on the positive electrode shell, and dry them in a 105℃ vacuum oven for 2 hours. Then remove them and place them in the transition chamber of the glove box. Finally, assemble the CR2025 model battery in the glove box. The assembly sequence is: positive electrode shell, positive electrode sheet, electrolyte, separator, electrolyte, lithium sheet, gasket, spring sheet, and negative electrode shell.

[0078] like Figure 1 As shown, the results indicate that the peak positions of (003), (101), (104), and (018 / 110) are consistent with the characteristic peaks of the layered structure, and no obvious impurity peaks are observed. This indicates that the main phase structure -α-NaFeO2 structure of all samples was successfully maintained, with a space group of R-3m, and no significant impurities were introduced after doping. The (003) peak corresponds to the interplanar spacing along the c-axis of the layered structure. As the F / C doping concentration increases (0%→3%), this peak shifts to a lower angle, indicating c-axis expansion (increased cell volume), which may be due to F. - (Ionic radius 1.33 Å) Partially substituted O 2- (1.40 Å) or C doping causes lattice distortion. The degree of splitting of the (104) peak reflects cation mixing (Ni 2+ The peaks are sharper and split less after doping (occupying the Li layer), indicating that F / C doping suppresses cation mixing and improves structural order. The two pairs of peaks (006) / (012) and (018) / (110) are clearly split, indicating that the F-doped high-nickel cathode material synthesized by this method has a better layered structure.

[0079] Figure 2 This is a SEM image of NCM-FC0% material. The particles are evenly distributed, but the connections between the particles are relatively tight, indicating that the material may have a high density and low porosity. Figure 3 The image shows the SEM morphology of NCM-FC2% material. Compared with NCM-FC0%, the agglomeration phenomenon of NCM-FC2% doped with fluorine carbon is significantly reduced, and different particle distributions are shown. The connection between particles is looser, indicating that the material has higher porosity.

[0080] Depend on Figure 2 It can be seen that NCM-FC0% particles have a relatively regular shape and a relatively smooth surface. Figure 3 The particle shape and surface properties of fluorocarbon doped materials differ from those of undoped materials, exhibiting a rougher surface and more pores between particles. This surface roughness may be due to the FC doping, potentially resulting in more active sites. The pores between particles may be formed by the high-temperature decomposition of PVDF and the release of gases, which can enhance electrolyte permeability and ion transport rates, thereby improving the material's electrochemical performance.

[0081] Figure 4 These are the charge-discharge curves of three cathode materials with different doping contents at 0.1C. The discharge specific capacities of NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% are 191.09 mAh g⁻¹. -1 176.72mAh g -1 207.69mAh g -1 and 140.87mAh g -1 The initial capacity of NCM-FC2% was significantly higher than that of other samples, indicating that appropriate F doping can enhance the Li content in the material. + The mobility of fluorine improves the electrochemical performance of materials, while excessive fluorine doping leads to a large amount of lithium. + / Ni 2+ When mixed, the electrochemical performance of the material actually decreases. Figure 5 The rate capacity of NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% at different current densities from 0.1C to 5C within the range of 2.7V to 4.3V is shown. The discharge specific capacity decreases with increasing rate; at 5C, the discharge specific capacity of NCM-FC2% is 101.36 mAh g. -1 The discharge specific capacities of NCM-FC0%, NCM-FC1%, and NCM-FC3% are 46.96 mAh g, respectively. -1 50.42mAh g -1 and 0.53mAh g -1 This indicates that fluorine doping in the material affects the diffusion rate of lithium ions. One possible reason is that fluorine doping can affect the diffusion rate of lithium ions. + More space allows Li +Diffusion is easier; on the other hand, the surface of the cathode material and the electrolyte may be more thoroughly wetted, Li + The shortened migration distance consequently affects the rate performance of NCM-FC (0%~3%). High-nickel ternary cathode materials with appropriate F doping exhibit greater discharge specific capacity and better rate performance at higher current rates. When the current density recovers to 0.1C, the maximum discharge specific capacity of NCM-FC at 2% reaches 183.49 mAh g⁻¹. -1 This indicates that the modified NCM-FC2% has excellent reversible cycling structure. Figure 6 Cycling curves for NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% are shown at an upper cutoff voltage of 4.3V. The discharge specific capacity of NCM-FC2% during the first cycle is 210.10 mAh g. -1 The performance was higher than other samples, and the retention rate was the best after 100 cycles. Appropriate F doping in the high-nickel ternary cathode material forms metal-fluorine (TM-F) bonds. The TM-F bonds are stronger than the TM-O bonds, resulting in a thinner transition metal layer, while Li... + The layers were expanded, Li + The migration of nitrogen becomes easier, resulting in better cycle performance. However, excessive F doping leads to a large amount of Li / Ni mixing in high-nickel ternary cathode materials, without improving cycle performance.

[0082] The discharge specific capacities of Al2O3@NCM-FC2% prepared in Example 2, Example 4, Example 5, Comparative Example 1, Comparative Example 2, and the Al2O3@NCM-FC2% embedded with Li3PO4 nanopillars prepared in step 21 of Example 4, and the Al2O3@NCM-FC2% prepared in step S22 of Example 4 are compared in the table below:

[0083] Table 1. Discharge specific capacity of each sample at different discharge rates

[0084]

[0085] As can be seen from the table above, the MgO@Al2O3@NCM-FC2% prepared in Example 4 and Example 4 both have higher discharge specific capacity under 0.1C and 5C rate conditions.

[0086] Cyclic voltammetry tests were performed on NCM-FC0%-NCM-FC3% materials, and the results are as follows: Figure 7 , Figure 8As shown, redox peaks for NCM-FC0% and NCM-FC2% are clearly observed within the voltage range of 2.7V to 4.3V. In the second cycle, the oxidation peak of NCM-FC0% appears around 4.0V, and the reduction peak appears around 3.5V. This indicates that the material underwent an electrochemical reaction and lithium-ion insertion / extraction process. Compared to the second cycle, the position and shape of the redox peaks in the third cycle are basically the same, but the peak intensity is lower than that of the first cycle. This may be because a solid electrolyte interphase (SEI) film forms on the surface of the material during charge and discharge, leading to a decrease in the activity of the electrochemical reaction in subsequent cycles. Compared to NCM-FC0%, the redox peaks of NCM-FC2% are more obvious and sharper, and there are three pairs of redox peaks. Furthermore, compared to the second and third cycles, the intensity and shape of the redox peaks remain relatively stable, with less attenuation. This indicates that the modified material has good cycle stability and electrochemical activity. This demonstrates that fluorine doping can improve the electronic conductivity and lithium-ion diffusion performance of the material, and enhance the reversibility of the electrochemical reaction. Meanwhile, fluorocarbon coating can form a protective layer on the material surface, reducing direct contact between the material and the electrolyte, inhibiting side reactions, and improving the material's cycle stability and electrochemical performance.

[0087] The AC impedance of the first cycle was measured and fitted for NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% materials. The results are as follows: Figure 9 , Figure 10 Table 2 shows the results. From the first high-frequency region results, it can be seen that the charge transfer impedance Rct of NCM-FC0% material is the smallest, indicating easier electrochemical reactions. The Rct values ​​of NCM-FC1% and NCM-FC2% are not significantly different, but both are smaller than those of NCM-FC3%, suggesting that excessive doping content is detrimental to reducing the charge transfer impedance. The slope of the curve in the low-frequency region is related to the diffusion process of the material. Calculations show that the lithium-ion diffusion coefficient D of NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% are... Li+ They are 4.51×10 -11 cm 2 s -1 3.99×10 -11 cm 2 s -1 5.72×10 -11 cm 2 s -1 and 2.29×10 -11 cm 2 s -1 The higher lithium-ion diffusion rate of NCM-FC2% is likely due to the strong Li-F layer formed after fluorine doping, which helps to widen the lithium-ion interlayer spacing, thereby enhancing the diffusion ability of lithium ions.

[0088] Table 2 Impedance fitting data for each sample

[0089]

[0090] As can be seen from the table above, the MgO@Al2O3@NCM-FC2% prepared in Examples 4 and 5 both exhibit superior electrical properties, significantly reduced impedance, increased lithium-ion diffusion rate, and stronger lithium-ion diffusion capability.

[0091] Figure 11 These are the charge-discharge curves of three cathode materials with different doping ratios at a cutoff voltage of 2.7V to 4.5V and a discharge rate of 0.1C. The discharge specific capacities of NCM-FC from 0% to 3% are 204.78 mAh g. -1 168.42mAh g -1 213.05mAh g -1 and 142.30mAh g -1 The specific capacity at 4.3V was increased, indicating that increasing the charge / discharge cutoff voltage has an impact on improving the capacity of the material, allowing more active lithium ions to participate in the electrochemical reaction and improving the charge / discharge capacity. Figure 12 The rate capacity of all samples is shown at different current densities from 0.1C to 5C within the range of 2.7V to 4.5V. The discharge specific capacity decreases with increasing rate; at 5C, the discharge specific capacity of NCM-FC2% is 65.22 mAh g⁻¹. -1 The discharge specific capacities of NCM-FC1% and NCM-FC3% are 58.88 mA hg, respectively. -1 and 42.75mAh g -1 It can be seen that the unmodified NCM-FC0% exhibits significant capacity decay at high rates, indicating impaired ion / electron transport kinetics. When the rate recovers to 0.1C, the maximum discharge specific capacity of NCM-FC2% reaches 154.24 mAh g⁻¹. -1 This indicates that the modified NCM-FC2% exhibits good reversibility of its cycling structure even at high cutoff voltages. However, the specific capacities of NCM-FC1% and NCM-FC3% are lower than those of the NCM-FC1% sample, suggesting that both insufficient and excessive doping can obstruct ion transport pathways. Figure 13Cycling curves for all samples are shown under an upper cutoff voltage of 4.5V. After 100 cycles, NCM-FC2% exhibits the best cycling performance and stability. Unmodified NCM-FC0% shows rapid capacity decay at high cutoff voltages, indicating lattice oxygen precipitation, transition metal dissolution leading to structural collapse, and interfacial side reactions. NCM-FC1% also decays relatively quickly, possibly due to insufficient F doping or a thin C coating layer, resulting in incomplete suppression of interfacial side reactions. NCM-FC3% may have excessive doping, introducing lattice stress or interfacial impedance.

[0092] Figure 14 , Figure 15 The figures show the CV curves for the first three cycles of NCM-FC0% and NCM-FC2%, respectively. All materials exhibit typical CV curves for high-nickel cathode materials, displaying three pairs of oxidation and reduction peaks. The potential difference between the redox peaks in NCM-FC2% increases continuously with increasing cycle number. This is because F doping leads to a broader Li... + The insertion / extraction channel shortens the Li + The transport path reduces the polarization of the material.

[0093] The AC impedance of NCM-FC0%-NCM-FC3% materials in the first cycle at 2.7V~4.5V was measured and fitted. The results are as follows: Figure 16 , Figure 17 As shown in Table 2, the test results at 4.5 V and 4.3 V are not significantly different. The lithium-ion diffusion coefficient D of NCM-FC0%-NCM-FC3% is... Li + They are 3.87×10 -11 cm 2 s -1 4.22×10 -11 cm 2 s -1 6.17×10 -11 cm 2 s -1 and 4.32×10 -11 cm 2 s -1 NCM-FC2% D Li + Higher values ​​are beneficial for improving the rate performance and electrochemical activity of materials.

[0094] In summary, the NCM-FC2% obtained by mixing NCM811 with 2% PVDF and sintering at 450℃ in a N2 atmosphere exhibits a well-developed layered structure, uniform particle distribution, weak agglomeration, and a rougher surface. Its discharge specific capacity is optimal in both the 2.7-4.3V and 2.7-4.5V ranges. Specifically, the discharge specific capacity of NCM-FC2% reaches 207.69 mAh g⁻¹ in the 2.7V~4.3V range. -1 The discharge specific capacities of NCM-FC0%, NCM-FC1%, and NCM-FC3% are 191.09 mA hg, respectively. -1 176.72mAh g -1 and 140.87mAh g -1 The discharge specific capacity is 1.09 times higher than that of NCM-FC0%. At higher cutoff voltages (2.7V~4.5V), the discharge specific capacity of NCM-FC2% reaches 223.79 mAh g⁻¹. -1 The discharge specific capacities of NCM-FC0%, NCM-FC1%, and NCM-FC3% are 204.78 mA hg, respectively. -1 168.42mAh g -1 and 142.30 mAh g -1 Meanwhile, NCM-FC2% exhibited superior lithium-ion diffusion rates at both 2.7–4.3 V and 2.7 V–4.5 V. The lithium-ion diffusion coefficients D of NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% were also observed at 2.7 V–4.3 V. Li + They are 4.51×10 -11 cm 2 s -1 3.99×10 - 11 cm 2 s -1 5.72×10 -11 cm 2 s -1 and 2.29×10 -11 cm 2 s -1 At 2.7V~4.5V, the lithium-ion diffusion coefficients of NCM-FC0%, NCM-FC1%, NCM-FC2%, and NCM-FC3% are 3.87×10⁻⁶. -11 cm 2 s -1 4.22×10 -11 cm 2 s -1 6.17×10 -11 cm2 s -1 and 4.32×10 -11 cm 2 s -1 This is because F doping creates Li vacancies at the O sites, providing Li... + It provides a wider insertion / extraction channel, leading to an increase in the lithium-ion diffusion coefficient. With appropriate F doping, high-nickel ternary cathode materials exhibit greater discharge specific capacity at higher cutoff voltages and higher current rates, demonstrating better rate performance.

[0095] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0096] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a fluorine-carbon doped modified ternary cathode material for lithium-ion batteries, characterized in that, Includes the following steps: Step 1: Using Ni 0.838 Co 0.114 Mn 0.048 (OH)2 and LiOH·H2O were mixed, ground, and sintered to obtain a high-nickel cathode material; Step 2: The high-nickel cathode material is ground and mixed with polyvinylidene fluoride (PVDF) and then dissolved in anhydrous ethanol. The mixture is heated in a water bath and stirred to obtain a gel-like material. The gel-like material is then vacuum-dried and ground to obtain a solid powder. This powder is then sintered a second time under an inert atmosphere to obtain a fluorocarbon-doped modified lithium-ion battery ternary cathode material. The fluorocarbon-doped modified lithium-ion battery ternary cathode material is then coated with a double layer of alumina and magnesium oxide. This fluorocarbon-doped modified lithium-ion battery ternary cathode material is designated NCM-FC. Specific methods include: S21. Using a sol-gel coating method, aluminum isopropoxide is coated on the surface of NCM-FC to obtain an aluminum oxide coating layer, i.e., Al2O3@NCM-FC; S22. Place Al2O3@NCM-FC in an oxygen plasma reactor and set the vacuum level to ≤1.2×10⁻⁶. -5 Under a pressure of 150-200 W and an oxygen flow rate of 30-50 sccm, oxygen plasma was applied to the alumina coating layer on the surface of Al2O3@NCM-FC for 5-10 min to activate the alumina coating layer. The activated Al2O3@NCM-FC was then immersed in a lithium dihydrogen phosphate solution, and a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer was added. After holding at 25°C for 30 min, the pressure was increased to 1.5-2 MPa and the temperature was raised to 80°C for 1-2 h. Then, the temperature was raised to 120°C and held for 1 h. The mixture was then cooled to room temperature. The mixture was then heat-treated at 300°C for 1 h in a tube furnace under a nitrogen atmosphere. After cooling, Al2O3@NCM-FC with Li3PO4 nanopillars embedded was obtained. S23. Using magnesium nitrate hexahydrate as raw material, the Al2O3@NCM-FC embedded in Li3PO4 nanopillars was coated by sol-gel coating method to obtain MgO@Al2O3@NCM-FC with a double layer of aluminum oxide and magnesium oxide coating.

2. The method for preparing the fluorine-carbon doped modified ternary cathode material for lithium-ion batteries as described in claim 1, characterized in that, In step one, Ni 0.838 Co 0.114 Mn 0.048 The molar ratio of (OH)2 to LiOH·H2O is 1:1~1.

1.

3. The method for preparing the fluorine-carbon doped modified ternary cathode material for lithium-ion batteries as described in claim 1, characterized in that, In step one, the sintering atmosphere is an oxygen atmosphere, and the sintering heating program is as follows: the temperature is increased from 25°C to 150°C at a heating rate of 2~5°C / min, and held for 40~50 min; then the temperature is increased to 500°C at a heating rate of 2~5°C / min, and held for 300 min; the temperature is increased to 850°C at a heating rate of 2~5°C / min, and held for 300 min; then the temperature is decreased to 780°C at a cooling rate of 2°C / min, and held for 600 min; finally, the temperature is decreased to room temperature at a cooling rate of 2~5°C / min.

4. The method for preparing the fluorine-carbon doped modified ternary cathode material for lithium-ion batteries as described in claim 1, characterized in that, In step two, polyvinylidene fluoride accounts for 1 wt% to 3 wt% of the mass of the high-nickel cathode material.

5. The method for preparing the fluorine-carbon doped modified ternary cathode material for lithium-ion batteries as described in claim 1, characterized in that, In step two, the water bath heating temperature is 70~90℃, and the vacuum drying time is 10~16h.

6. The method for preparing the fluorine-carbon doped modified ternary cathode material for lithium-ion batteries as described in claim 1, characterized in that, In step two, the inert atmosphere is a nitrogen atmosphere, and the sintering heating program is as follows: heat from 25°C to 150°C at a heating rate of 3°C / min, hold for 30 min; then heat to 400-500°C at a heating rate of 1-3°C / min, hold for 2-4 h; finally cool to room temperature at a cooling rate of 5°C / min.

7. The method for preparing the fluorine-carbon doped modified ternary cathode material for lithium-ion batteries as described in claim 1, characterized in that, The fluorine-carbon doped modified lithium-ion battery ternary cathode material is doped with fluorine and coated with a fluorine-carbon layer on its surface.

8. The method for preparing the fluorine-carbon doped modified ternary cathode material for lithium-ion batteries as described in claim 1, characterized in that, In S22, the ratio of activated Al2O3@NCM-FC, lithium dihydrogen phosphate solution, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is 5~10g:50~200mL:0.5~1g.

9. A battery, characterized in that, The positive electrode material of the battery is prepared by the method for preparing fluorocarbon-doped modified lithium-ion battery ternary positive electrode material according to any one of claims 1-8.

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