Difunctional ultrahigh-nickel ternary positive electrode material and preparation method thereof

Abstract

The invention belongs to the technical field of lithium batteries, and discloses a difunctional ultrahigh-nickel ternary positive electrode material and a preparation method thereof.The preparation method comprises the steps that an ultrahigh-nickel ternary positive electrode material precursor, a lithium source, gallium-indium-tin alloy powder and hydroxyapatite nano powder are mixed to obtain a material, the material is subjected to ball milling and then subjected to primary screening, and a primary screening material is obtained; the preparation method comprises the following steps: mixing the raw materials to obtain a mixed material, sintering the mixed material to obtain a primary sintered product with a composite buffer layer, and carrying out low-temperature heat treatment on the primary sintered product to obtain the difunctional ultrahigh-nickel ternary positive electrode material, the difunctional ultrahigh nickel ternary positive electrode material prepared by the invention has the advantages of good structural stability, low residual alkali and excellent electrochemical performance, and has important technical significance and market value.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a dual-functional ultra-high nickel ternary cathode material and its preparation method. Background Technology

[0002] With the surge in demand for long driving range in electric vehicles, ultra-high nickel ternary cathode materials have become a core candidate material for next-generation high-energy-density lithium-ion batteries due to their advantages in environmental friendliness and cost, such as high energy density and low cobalt content.

[0003] However, due to its high nickel content, this material suffers from two major drawbacks that severely restrict its commercial application. First, its structural stability is poor. During charging and discharging, repeated lithium ion extraction and insertion lead to primary grain boundary slippage, generating significant internal forces and resulting in a secondary particle cracking rate as high as 5-8%. The interfaces exposed by these cracks are prone to side reactions with the infiltrated electrolyte, and the generated gases and byproducts further expand the cracks, causing material pulverization, increased impedance, and rapid capacity decay. Existing doping and coating methods cannot adapt to the dynamic stress of "expansion-contraction," easily leading to accelerated cracking due to stress accumulation in the later stages of cycling. Second, it has high residual alkali on the surface. To compensate for lithium volatilization during high-temperature sintering and to synthesize ordered layered compounds, excessive lithium sources are added during sintering. These readily react with H2O and CO2 in the air to generate residual alkalis LiOH and Li2CO3. Existing methods for reducing residual alkali are mostly water washing or high-temperature decomposition. The water washing process damages the surface structure of the material, causing Li... + The loss and capacity decay, while high-temperature decomposition consumes energy and is prone to lattice mutation.

[0004] The aforementioned cracking and residual alkali problems will worsen with the increase of nickel content, severely restricting the application of ultra-high nickel ternary cathode materials. Summary of the Invention

[0005] The purpose of this invention is to provide a bifunctional ultra-high nickel ternary cathode material and its preparation method, so as to overcome the problems existing in the prior art. The bifunctional ultra-high nickel ternary cathode material prepared by this invention has the advantages of good structural stability, low residual alkali and excellent electrochemical performance, and has important technical significance and market value.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a bifunctional ultra-high nickel ternary cathode material, comprising the following steps: The material is obtained by mixing ultra-high nickel ternary cathode material precursor, lithium source, gallium indium tin alloy powder and hydroxyapatite nanopowder. The material is ball-milled and then sieved once to obtain a mixture. The mixture is sintered to obtain a primary sintered product with a composite buffer layer; The sintered material is subjected to low-temperature heat treatment to obtain a dual-functional ultra-high nickel ternary cathode material.

[0007] In some embodiments, the ultra-high nickel ternary cathode material precursor is Ni x Co y Mn z (OH)2, where x≥0.9, 0≤y≤0.1, 0≤z≤0.1, x+y+z=1.

[0008] In some embodiments, the lithium source is lithium hydroxide; the melting point of the gallium indium tin alloy powder is 25-30 °C; and the particle size of the hydroxyapatite nanoparticles is 5-8 nm.

[0009] In some embodiments, the addition ratio of the ultra-high nickel ternary cathode material precursor, lithium source, gallium indium tin alloy powder and hydroxyapatite nanopowder is 1:1.03-1.09 mol / L:1-3 wt%:0.5-1 wt%.

[0010] In some embodiments, the mass ratio of the material to the balls is 1:0.6; and the ball milling time is 1 hour.

[0011] In some embodiments, the first sieve is 100 mesh.

[0012] In some embodiments, sintering the mixture specifically includes: The mixture is heated to 700-800 ℃ in an oxygen atmosphere at a heating rate of 3-8 ℃ / min, and then held at that temperature for 12 hours.

[0013] In some embodiments, the step of subjecting the primary sintered product to low-temperature heat treatment to obtain a dual-functional ultra-high nickel ternary cathode material specifically includes: The sintered material is subjected to low-temperature heat treatment at 200-400 °C for 2-4 h under an argon atmosphere. After natural cooling to room temperature, it is sieved a second time to obtain a dual-functional ultra-high nickel ternary cathode material.

[0014] In some embodiments, the secondary sieving is 400 mesh.

[0015] Secondly, the present invention provides a dual-functional ultra-high nickel ternary cathode material, which is obtained based on the above-mentioned preparation method of a dual-functional ultra-high nickel ternary cathode material.

[0016] The above technical solution has the following advantages or beneficial effects: Firstly, this invention provides a method for preparing a dual-functional ultra-high nickel ternary cathode material. By introducing gallium indium tin alloy and hydroxyapatite nanoparticles into the ultra-high nickel ternary material, a dual-functional synergistic approach of "phase change buffering" and "residual alkali conversion" is achieved. The gallium indium tin alloy is liquid at room temperature and can absorb stress by flowing with volume changes. When the temperature rises above 30°C, it turns into a solid state, providing rigid support, thereby dynamically adapting to different operating conditions and significantly suppressing secondary spherical cracking, resulting in a cracking rate of less than 2% after 50 cycles. At the same time, the hydroxyapatite nanoparticles can react in situ with residual alkali on the surface to generate a Li3PO4 layer with high ionic conductivity, effectively reducing the residual alkali content while ensuring efficient lithium-ion transport. Finally, a cathode material with stable structure, low residual alkali content, and excellent cycle performance is obtained, which has important application value.

[0017] In some embodiments, this technical solution uses an ultra-high nickel precursor with a nickel content of ≥90%, which significantly improves the specific capacity and upper limit of energy density of the material. Under the synergistic effect of dual functions, the inherent structural instability and surface residual alkali problems of high nickel materials are specifically solved, ensuring that the high nickel component can exert its high capacity advantage while also having excellent cycle stability and safety, thereby breaking through the technical bottleneck of traditional ultra-high nickel materials that are difficult to balance high energy density and long cycle life.

[0018] In some embodiments, lithium hydroxide is selected as a reliable lithium source to ensure full lithiation. Gallium indium tin alloy powder is liquid at room temperature and can flow freely with the particle volume changes caused by lithium ion extraction and insertion, absorbing internal stress. When the battery charging and discharging temperature rises above 30°C (normal operating temperature), the alloy transforms into a solid state, forming rigid support points to suppress excessive particle expansion and achieve dynamic adaptation between flexible buffering at low temperatures and rigid support at high temperatures. The use of 5-8 nm ultrafine hydroxyapatite nanoparticles greatly increases its specific surface area and reactivity, ensuring full and uniform in-situ conversion with residual alkali on the material surface, efficiently generating a Li3PO4 ion conductor layer, and simultaneously achieving residual alkali removal and interface ion transport optimization.

[0019] In some embodiments, this scheme achieves optimal control of material properties by limiting the precise proportions of each key component. A slight excess of lithium source ensures sufficient reaction and compensates for sintering losses; 1-3 wt% of alloy powder provides sufficient liquid / solid medium during phase transition, effectively controlling stress; 0.5-1 wt% of ultrafine hydroxyapatite is sufficient to efficiently convert surface residual alkali; this optimized proportion, while ensuring the core dual functions, maximizes the maintenance of the material's main phase structure and specific capacity, achieving a balance between high capacity, long cycling performance, and low residual alkali.

[0020] In some embodiments, by limiting the mass ratio of materials to balls to 1:0.6 and setting the ball milling time to 1 hour, the present invention can ensure that the precursor, lithium source, alloy and hydroxyapatite nanopowder are fully and uniformly mixed, while effectively avoiding particle morphology damage and secondary agglomeration caused by excessive mechanical force. This lays a key foundation for subsequent uniform sintering and precise functional distribution of alloy and nanopowder, and is an important process guarantee for achieving the synergistic effect of its dual functions of "phase change buffer" and "residual alkali conversion".

[0021] In some embodiments, the present invention limits the use of a 100-mesh sieve for sieving, which can effectively remove trace amounts of large-sized impurities or undispersed lumps that may be introduced into the material during ball milling, ensuring that the mixture has a suitable and uniform particle size, which provides a guarantee for the uniformity of the subsequent sintering reaction and the uniformity of the microstructure of the final product. It is a key process step for achieving stable and repeatable preparation of dual-functional materials of "phase change buffer-residual alkali conversion".

[0022] In some embodiments, the present invention is limited to heating to 700-800°C at a rate of 3-8°C / min in an oxygen atmosphere and holding at that temperature for 12 hours. This gentle heating process is conducive to alloy melting and uniform distribution, and can promote the formation of a complete material lattice. It is a key sintering process for achieving excellent electrochemical performance of the material.

[0023] In some embodiments, the low-temperature heat treatment of the present invention is carried out under argon protection, which can prevent the material from being oxidized during the heat treatment process and at the same time provide a stable environment for the reaction between hydroxyapatite and residual alkali; during the heat treatment process, the hydroxyl groups on the surface of hydroxyapatite react specifically with the residual alkali on the surface of the material (Li2CO3 + Ca). 10 (PO4)6(OH)2→ 2Li3PO4+10CaCO3+ H2O↑), the generated CaCO3 is uniformly deposited at the grain boundaries, further enhancing the structural stability. Li3PO4, as a fast ion conductor, can construct an efficient lithium-ion transport channel, which is an important post-processing process for achieving excellent cycle performance of ultra-high nickel ternary cathode materials.

[0024] In some embodiments, a 400-mesh secondary sieve is used to finely separate and remove trace amounts of ultrafine powder and agglomerates that may be generated during the sintering process, ensuring that the finished cathode material has a uniform particle size distribution that meets battery-grade requirements, thereby improving the uniformity of electrode coating and compaction density, and optimizing the electrochemical performance of the battery.

[0025] Secondly, this invention provides a bifunctional ultra-high nickel ternary cathode material. The prepared bifunctional ultra-high nickel ternary cathode material can achieve a capacity of ≥228 mAh / g at 0.1C under a voltage of 4.3V and an initial efficiency of ≥93%. Its high capacity and high initial efficiency characteristics meet the requirements of high energy density batteries. In addition, the equipment required for the preparation process is simple, the steps are controllable, and it is suitable for large-scale mass production. Its commercial application prospects are broad. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a method for preparing a dual-functional ultra-high nickel ternary cathode material according to some embodiments of this specification. Detailed Implementation

[0027] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] To better meet the high-performance requirements of lithium-ion batteries and improve the core problems of easy cracking and high residual alkali in ultra-high nickel ternary cathode materials, while ensuring their electrochemical performance, this invention provides a dual-functional ultra-high nickel ternary cathode material and its preparation method. While avoiding the cracking of secondary spherical particles and reducing residual alkali in ultra-high nickel ternary cathode materials, it ensures the high ion conductivity and electrochemical performance of the material, making it suitable for the production and application of high-energy-density lithium-ion batteries.

[0031] To address the shortcomings of existing ultra-high nickel ternary cathode materials, such as easy cracking, high residual alkali, and the difficulty of balancing structural stability and electrochemical performance with traditional improvement methods, this invention aims to provide an ultra-high nickel ternary cathode material with dual functions of "phase change buffering and residual alkali conversion" and its preparation method. By introducing gallium indium tin alloy powder, its phase change characteristics are utilized to achieve dynamic stress buffering within the material, improving the problem of easy cracking of secondary spherical particles. Through the in-situ reaction of hydroxyapatite nanopowder with residual alkali, the residual alkali is converted and removed, while generating highly ion-conductive Li3PO4. This reduces residual alkali while ensuring lithium-ion transport efficiency, ultimately resulting in an ultra-high nickel ternary cathode material with stable structure, low residual alkali, and excellent electrochemical performance.

[0032] All experiments used Ni as the precursor for ultra-high nickel ternary cathode materials. x Co y Mn z (OH)2, where x≥0.9, 0≤y≤0.1, 0≤z≤0.1, x+y+z=1; the lithium source is LiOH·H2O.

[0033] Example 1: This embodiment provides a method for preparing a dual-functional ultra-high nickel ternary cathode material. Figure 1 This is a schematic flowchart illustrating a method for preparing a bifunctional ultra-high nickel ternary cathode material according to some embodiments of this specification, including the following steps: Step 1: Mix the ultra-high nickel ternary cathode material precursor, lithium source, gallium indium tin alloy powder, and hydroxyapatite nanoparticles to obtain the material. Then, ball mill the material and sieve it once to obtain the mixture. Ni 0.9 Co 0.05 Mn 0.05 (OH)₂ and LiOH·H₂O are mixed in a molar ratio of 1:1.06, and Ni is added. 0.9 Co 0.05 Mn 0.05 The material was prepared by mixing 2 wt% gallium indium tin alloy powder (melting point 28 ℃) and 0.8 wt% hydroxyapatite nanoparticles (particle size 6 nm) with (OH)2. The material was then mixed in a ball mill for 1 h, with the total weight of the material to the mass ratio of the balls being 1:0.6. After thorough mixing, the material was passed through a 100-mesh sieve to obtain the mixture.

[0034] Step 2: Sinter the mixture to obtain a primary sintered product with a composite buffer layer. The mixture was placed in a crucible and placed in an atmosphere furnace. Under an oxygen atmosphere, the temperature was increased to 750 °C at a heating rate of 5 °C / min and held for 12 h. After sintering, the mixture was passed through a 400-mesh sieve to obtain a primary sintered product with a composite buffer layer.

[0035] Step 3: The sintered product is subjected to low-temperature heat treatment to obtain a dual-functional ultra-high nickel ternary cathode material. The sintered product was placed in another atmosphere furnace, and argon gas was introduced to purge the air. The product was then subjected to low-temperature heat treatment at 300 °C for 3 hours under an argon atmosphere to allow the residual alkali reaction product to be uniformly deposited. After natural cooling to room temperature, the product was passed through a 400-mesh sieve to obtain the dual-functional ultra-high nickel ternary cathode material A.

[0036] Example 2: This embodiment provides a method for preparing a dual-functional ultra-high nickel ternary cathode material. Figure 1 This is a schematic flowchart illustrating a method for preparing a bifunctional ultra-high nickel ternary cathode material according to some embodiments of this specification, including the following steps: Step 1: Mix the ultra-high nickel ternary cathode material precursor, lithium source, gallium indium tin alloy powder, and hydroxyapatite nanoparticles to obtain the material. Then, ball mill the material and sieve it once to obtain the mixture. Ni 0.9 Co 0.05 Mn 0.05 (OH)₂ and LiOH·H₂O are mixed in a molar ratio of 1:1.03, and Ni is added. 0.9 Co 0.05 Mn 0.05 The material was prepared by mixing 1 wt% gallium indium tin alloy powder (melting point 25 ℃) and 0.5 wt% hydroxyapatite nanoparticles (particle size 5 nm) with (OH)2. The material was then mixed in a ball mill for 1 h, with the total weight of the material to the mass ratio of the balls being 1:0.6. After thorough mixing, the material was passed through a 100-mesh sieve to obtain the mixture.

[0037] Step 2: Sinter the mixture to obtain a primary sintered product with a composite buffer layer. The mixture was placed in a crucible and placed in an atmosphere furnace. Under an oxygen atmosphere, the temperature was increased to 750 °C at a heating rate of 5 °C / min and held for 12 h. After sintering, the mixture was passed through a 400-mesh sieve to obtain a primary sintered product with a composite buffer layer.

[0038] Step 3: The sintered product is subjected to low-temperature heat treatment to obtain a dual-functional ultra-high nickel ternary cathode material. The sintered product was placed in another atmosphere furnace, and argon gas was introduced to purge the air. The product was then subjected to low-temperature heat treatment at 300 °C for 3 hours under an argon atmosphere to allow the residual alkali reaction product to be uniformly deposited. After natural cooling to room temperature, the product was passed through a 400-mesh sieve to obtain the bifunctional ultra-high nickel ternary cathode material B.

[0039] Example 3: This embodiment provides a method for preparing a dual-functional ultra-high nickel ternary cathode material. Figure 1 This is a schematic flowchart illustrating a method for preparing a bifunctional ultra-high nickel ternary cathode material according to some embodiments of this specification, including the following steps: Step 1: Mix the ultra-high nickel ternary cathode material precursor, lithium source, gallium indium tin alloy powder, and hydroxyapatite nanoparticles to obtain the material. Then, ball mill the material and sieve it once to obtain the mixture. Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH·H2O are mixed in a molar ratio of 1:1.09, and Ni is added. 0.9 Co 0.05 Mn 0.05 The materials were prepared by mixing 3 wt% gallium indium tin alloy powder (melting point 30 ℃) and 1 wt% hydroxyapatite nanoparticles (particle size 8 nm) with (OH)2. The materials were then mixed in a ball mill for 1 hour, with the total weight of the materials being 1:0.6 of the ball weight. After thorough mixing, the materials were passed through a 100-mesh sieve to obtain the mixture.

[0040] Step 2: Sinter the mixture to obtain a primary sintered product with a composite buffer layer. The mixture was placed in a crucible and placed in an atmosphere furnace. Under an oxygen atmosphere, the temperature was increased to 750 °C at a heating rate of 5 °C / min and held for 12 h. After sintering, the mixture was passed through a 400-mesh sieve to obtain a primary sintered product with a composite buffer layer.

[0041] Step 3: The sintered product is subjected to low-temperature heat treatment to obtain a dual-functional ultra-high nickel ternary cathode material. The sintered product was placed in another atmosphere furnace, and argon gas was introduced to purge the air. The product was then subjected to low-temperature heat treatment at 300 °C for 3 hours under an argon atmosphere to allow the residual alkali reaction product to be uniformly deposited. After natural cooling to room temperature, the product was passed through a 400-mesh sieve to obtain the bifunctional ultra-high nickel ternary cathode material C.

[0042] Example 4: This embodiment provides a method for preparing a dual-functional ultra-high nickel ternary cathode material. Figure 1 This is a schematic flowchart illustrating a method for preparing a bifunctional ultra-high nickel ternary cathode material according to some embodiments of this specification, including the following steps: Step 1: Mix the ultra-high nickel ternary cathode material precursor, lithium source, gallium indium tin alloy powder, and hydroxyapatite nanoparticles to obtain the material. Then, ball mill the material and sieve it once to obtain the mixture. Ni 0.9 Co 0.1 (OH)2 and LiOH·H2O are mixed in a molar ratio of 1:1.09, and Ni is added. 0.9 Co0.1 The material was prepared by mixing 3 wt% gallium indium tin alloy powder (melting point 30 ℃) and 1 wt% hydroxyapatite nanoparticles (particle size 8 nm) with (OH)2. The material was then mixed in a ball mill for 1 h, with the total weight of the material to the mass ratio of the balls being 1:0.6. After thorough mixing, the material was passed through a 100-mesh sieve to obtain the mixture.

[0043] Step 2: Sinter the mixture to obtain a primary sintered product with a composite buffer layer. The mixture was placed in a crucible and then placed in an atmosphere furnace. Under an oxygen atmosphere, the temperature was increased to 700 °C at a rate of 3 °C / min and held for 12 h. After sintering, the mixture was passed through a 400-mesh sieve to obtain a primary sintered product with a composite buffer layer.

[0044] Step 3: The sintered product is subjected to low-temperature heat treatment to obtain a dual-functional ultra-high nickel ternary cathode material. The sintered product was placed in another atmosphere furnace, and after argon gas was introduced to purge the air, it was subjected to low-temperature heat treatment at 400 °C for 2 h under argon atmosphere to allow the product of the residual alkali reaction to be uniformly deposited. After natural cooling to room temperature, it was passed through a 400-mesh sieve to obtain the bifunctional ultra-high nickel ternary cathode material D.

[0045] Example 5: This embodiment provides a method for preparing a dual-functional ultra-high nickel ternary cathode material. Figure 1 This is a schematic flowchart illustrating a method for preparing a bifunctional ultra-high nickel ternary cathode material according to some embodiments of this specification, including the following steps: Step 1: Mix the ultra-high nickel ternary cathode material precursor, lithium source, gallium indium tin alloy powder, and hydroxyapatite nanoparticles to obtain the material. Then, ball mill the material and sieve it once to obtain the mixture. Ni 0.9 Mn 0.1 (OH)₂ and LiOH·H₂O are mixed in a molar ratio of 1:1.03, and Ni is added. 0.9 Mn 0.1 The material was prepared by mixing 1 wt% gallium indium tin alloy powder (melting point 25 ℃) and 0.5 wt% hydroxyapatite nanoparticles (particle size 5 nm) with (OH)2. The material was then mixed in a ball mill for 1 h, with the total weight of the material to the mass ratio of the balls being 1:0.6. After thorough mixing, the material was passed through a 100-mesh sieve to obtain the mixture.

[0046] Step 2: Sinter the mixture to obtain a primary sintered product with a composite buffer layer. The mixture was placed in a crucible and placed in an atmosphere furnace. Under an oxygen atmosphere, the temperature was increased to 800 °C at a heating rate of 8 °C / min and held for 12 h. After sintering, the mixture was passed through a 400-mesh sieve to obtain a primary sintered product with a composite buffer layer.

[0047] Step 3: The sintered product is subjected to low-temperature heat treatment to obtain a dual-functional ultra-high nickel ternary cathode material. The sintered product was placed in another atmosphere furnace, and after purging the air by argon gas, it was subjected to low-temperature heat treatment at 200 °C for 4 h under argon atmosphere to allow the product of the residual alkali reaction to be uniformly deposited. After naturally cooling to room temperature, it was passed through a 400-mesh sieve to obtain the bifunctional ultra-high nickel ternary cathode material E.

[0048] Comparative Example 1: Step 1, Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH·H2O were mixed in a molar ratio of 1:1.06, and 0.8 wt% of hydroxyapatite nanopowder (particle size 6 nm) was added. The total weight of the material and the mass ratio of the nanoparticles were 1:0.6. The mixture was mixed in a ball mill for 1 hour. After thorough mixing, the material was passed through a 100-mesh sieve to obtain the mixture. Step 2: The mixture is placed in a crucible and placed in an atmosphere furnace. Under an oxygen atmosphere, the temperature is raised to 750°C at a heating rate of 5°C / min and held for 12 hours. After sintering, the mixture is passed through a 400-mesh sieve to obtain a primary sintered product with a composite buffer layer. Step 3: Place the sintered product in another atmosphere furnace, introduce argon gas to purge the air, and hold it at 300℃ for 3 hours for low-temperature heat treatment. After naturally cooling to room temperature, pass it through a 400-mesh sieve to obtain the target product F.

[0049] Comparative Example 2: Step 1, Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH·H2O are mixed at a molar ratio of 1:1.06, and 2 wt% of gallium indium tin alloy powder (melting point 28℃) is added. The total weight of the material and the mass ratio of the small balls are 1:0.6. The mixture is mixed in a ball mill for 1 hour. After thorough mixing, the material is passed through a 100-mesh sieve to obtain the mixture. Step 2: The mixture is placed in a crucible and placed in an atmosphere furnace. Under an oxygen atmosphere, the temperature is raised to 750°C at a heating rate of 5°C / min and held for 12 hours. After sintering, the mixture is passed through a 400-mesh sieve to obtain a primary sintered product with a composite buffer layer. Step 3: Place the sintered product in another atmosphere furnace, purge the air with argon gas, and hold it at 300°C for 3 hours for low-temperature heat treatment. After naturally cooling to room temperature, pass it through a 400-mesh sieve to obtain the target product G.

[0050] Comparative Example 3: Step 1, Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and LiOH·H2O were mixed in a molar ratio of 1:1.06. 2 wt% of gallium indium tin alloy powder (melting point 28℃) and 0.8 wt% of hydroxyapatite nanoparticles (particle size 6 nm) were added. The total weight of the materials and the mass ratio of the small balls were 1:0.6. The mixture was mixed in a ball mill for 1 hour. After thorough mixing, the materials were passed through a 100-mesh sieve to obtain the mixture. Step 2: The mixture is placed in a crucible and placed in an atmosphere furnace. Under an oxygen atmosphere, the temperature is increased to 750°C at a heating rate of 5°C / min and held for 12 hours. After sintering, the mixture is passed through a 400-mesh sieve to obtain the target product H.

[0051] Table 1 shows the residual alkali in the powder of the target product GH obtained in Comparative Examples 1-3 and the residual alkali in the powder of the bifunctional ultra-high nickel ternary cathode material AE obtained in Examples 1-5. The residual alkali was measured by acid-base titration, as shown below: Table 1. Powdered residual alkali of Comparative Examples 1-3 and Examples 1-5

[0052] Table 2 shows the coin cell capacity and first-efficiency of the target product GH obtained in Comparative Examples 1-3 and the bifunctional ultra-high nickel ternary cathode material AE obtained in Examples 1-5 at 4.3V, as well as the capacity retention and cracking rate at 4.5V after 50 cycles at 1C. Table 2. Button capacity and cycle data for Comparative Examples 1-3 and Examples 1-5

[0053] The results show that hydroxyapatite nanopowder can effectively react with residual alkali during low-temperature heat treatment, reducing the residual alkali content of the material; the cracking rate of the sample without gallium indium tin alloy is as high as 8.7%, indicating that the phase change buffering effect of gallium indium tin alloy can significantly improve the structural stability of the material; in addition, the formation of Li3PO4 in the examples reduces the interfacial impedance and improves the electrochemical performance, verifying the effectiveness of the dual-function design of "phase change buffering-residual alkali conversion" of the present invention.

[0054] This invention provides a dual-functional ultra-high nickel ternary cathode material and its preparation method. By employing a phase change metal and a hydroxyapatite nanocoating, the structure and surface chemistry of the ultra-high nickel ternary cathode material are dually controlled, with the following significant advantages: First, the structural stability of the material is improved. Gallium indium tin alloy is liquid at room temperature and can flow freely with the changes in particle volume caused by lithium ion extraction and insertion, absorbing internal stress. When the battery charging and discharging temperature rises to above 30°C (normal operating temperature), the alloy transforms into a solid state, forming rigid support points, suppressing excessive particle expansion, and achieving dynamic adaptation between flexible buffering at low temperature and rigid support at high temperature. This reduces the cracking rate of the secondary spheres to below 2% after 50 cycles, which is better than traditional materials.

[0055] Secondly, the in-situ reaction between hydroxyapatite and residual alkali can control the residual alkali content of the material to a CO3 level without water washing. 2- ≤0.09wt%, OH - ≤0.18wt% avoids further reaction between residual alkali and electrolyte, H2O and CO2 in the air, thus improving the storage stability of the material; at the same time, the CaCO3 grain boundary strengthening phase generated by the reaction can further stabilize the structure, and the Li3PO4 fast ion conductor can reduce the interfacial impedance and ensure the lithium ion conduction efficiency.

[0056] Finally, the prepared target product has a capacity of ≥228 mAh / g and an initial efficiency of ≥93% at 0.1C under 4.3V voltage. Its high capacity and high initial efficiency meet the requirements of high energy density batteries. In addition, the equipment required for the preparation process is simple and the steps are controllable, making it suitable for large-scale mass production, and its commercial application prospects are broad.

[0057] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0058] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A preparation method of a bifunctional ultrahigh nickel ternary positive electrode material, characterized in that, The method comprises the following steps: mixing an ultrahigh nickel ternary positive electrode material precursor, a lithium source, a gallium-indium-tin alloy powder and hydroxyapatite nano powder to obtain a material, ball milling the material, and then performing a first screening to obtain a mixture; sintering the mixture to obtain a primary sintering product with a composite buffer layer; performing low-temperature heat treatment on the primary sintering product to obtain a dual-functional ultrahigh nickel ternary positive electrode material.

2. The method according to claim 1, wherein the method comprises the following steps: The ultra-high nickel ternary positive electrode material precursor is Ni x Co y Mn z (OH)2, wherein x≥0.9, 0≤y≤0.1, 0≤z≤0.1, x+y+z=1. ​ 3. The preparation method of the bifunctional ultrahigh nickel ternary positive electrode material according to claim 1, characterized in that, The lithium source is lithium hydroxide; the gallium-indium-tin alloy powder has a melting point of 25-30 ℃; and the hydroxyapatite nano powder has a particle size of 5-8 nm.

4. The preparation method of the bifunctional ultrahigh nickel ternary positive electrode material according to claim 1, characterized in that, The addition amount ratio of the ultrahigh nickel ternary positive electrode material precursor, the lithium source, the gallium-indium-tin alloy powder and the hydroxyapatite nano powder is 1:1.03-1.09 mol / L:1-3 wt%:0.5-1 wt%.

5. The method according to claim 1, wherein the method is characterized by, The mass ratio of the material to the ball is 1:0.6, and the ball milling time is 1 h.

6. The method according to claim 1, wherein the method is characterized by, The first screening is 100 mesh.

7. The method according to claim 1, wherein the method is characterized by, The sintering of the mixture specifically comprises: After the mixture is raised to 700-800 ℃ at a temperature raising rate of 3-8 ℃ / min in an oxygen atmosphere, the mixture is kept at the temperature for 12 h.

8. The method according to claim 1, wherein the method is characterized by, The low-temperature heat treatment of the primary sintering product to obtain the dual-functional ultrahigh nickel ternary positive electrode material specifically comprises: The primary sintering product is subjected to low-temperature heat treatment at 200-400 ℃ for 2-4 h in an argon atmosphere, and then is naturally cooled to room temperature and subjected to a second screening to obtain the dual-functional ultrahigh nickel ternary positive electrode material.

9. The method according to claim 8, wherein the method is characterized by, The second screening is 400 mesh.

10. A bifunctional ultrahigh nickel ternary cathode material, characterized in that, The dual-functional ultrahigh nickel ternary positive electrode material is obtained based on the preparation method of any one of claims 1-9.

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