Preparation method of high-initial-efficiency small-particle single-crystal ultra-high-nickel ternary positive electrode material

Abstract

This invention belongs to the field of lithium-ion battery material technology and discloses a method for preparing a high-efficiency, small-particle, single-crystal, ultra-high-nickel ternary cathode material. The method involves first uniformly mixing an ultra-high-nickel ternary precursor with a lithium source and a tungsten source, then mechanically densifying and pressing it into a block solid, followed by four-stage temperature-controlled calcination to obtain the target material. Mechanical densification reduces the interfacial fusion resistance during single-crystal growth; tungsten partially forms a Li2WO4 coating layer and partially substitutes for Ni with dopant phases. 2+ This invention not only inhibits grain growth but also stabilizes the crystal structure and improves initial efficiency; the four-stage temperature-controlled calcination allows for precise regulation of the material's microstructure. Through a synergistic strategy of coating-doping-single crystallization, this invention significantly enhances the electrochemical performance of materials in liquid and sulfide-based all-solid-state batteries. The process is controllable and has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, and in particular relates to a method for preparing a high-efficiency small-particle single-crystal ultra-high nickel ternary cathode material. Background Technology

[0002] With the acceleration of global energy transition and the intelligent upgrading of electronic devices, lithium-ion batteries, with their advantages of high energy density and long cycle life, have become the core power source for new energy vehicles and portable electronic terminals (smartphones, laptops, etc.), and have been widely used in large-scale energy storage power stations and distributed energy systems. As the core carrier for energy storage and release in lithium-ion batteries, the performance of the cathode material directly determines the battery's energy density, cycle stability, safety performance, and rate capability, making it a key bottleneck restricting the iterative upgrading of battery technology.

[0003] To meet the development demands of high-energy-density batteries, the nickel content of ternary (nickel-cobalt-manganese, NCM) cathode materials has been continuously increased. When the nickel content exceeds 90%, ultra-high-nickel ternary cathode materials are formed, with a theoretical specific capacity significantly higher than that of traditional low- and medium-nickel ternary materials, making them a core candidate material for next-generation high-energy-density batteries. However, the significant increase in nickel content has triggered a series of key technical challenges: nickel (especially Ni...) 2+ ) and lithium (Li + With similar ionic radii, lithium-nickel mixing is very likely to occur during material preparation and electrochemical cycling, which damages the layered crystal structure of the material and obstructs the lithium-ion insertion / extraction channels. This not only significantly reduces the actual discharge capacity of the material, but also exacerbates the structural decay during cycling, seriously affecting the long-term performance of the battery. This problem is particularly prominent in ultra-high nickel systems with a nickel content of ≥90%.

[0004] To improve the structural stability of high-nickel materials, single-crystalization technology has been widely researched and applied. Compared with traditional polycrystalline high-nickel ternary materials, single-crystal high-nickel ternary materials have no obvious grain boundaries, possess higher structural strength, and can effectively avoid structural damage caused by grain boundary slip during electrode cold pressing, while reducing the risk of particle breakage and pulverization during cycling. Currently, several technologies related to single-crystal ternary cathode materials have been disclosed, such as the ternary lithium battery material and its preparation method disclosed by Sandon New Energy Technology Co., Ltd. (CN109216688A), the preparation method of single-crystal ternary cathode material disclosed by Zhongwei New Materials Co., Ltd. (CN109279659A), and the preparation method of modified single-crystal ternary cathode material for lithium-ion batteries disclosed by Central South University (CN109841822A). However, existing technologies still have significant limitations: First, the prepared single-crystal particles generally have large grain sizes (2-5μm), and the excessively long lithium-ion transport paths result in poor rate performance, making it difficult to meet the requirements of scenarios such as fast charging of new energy vehicles and high power output of energy storage systems; Second, large-size single crystals still experience significant volume expansion and contraction during charge-discharge cycles, and are prone to structural cracking and breakage after long-term cycling, leading to continuous degradation of electrochemical performance. This problem is more prominent in solid-state battery systems (solid electrolyte and electrode interface compatibility requirements are higher, and particle breakage can easily cause interface contact failure); Third, the initial coulombic efficiency (first efficiency) of existing single-crystal ultra-high nickel cathode materials is generally only 86%-90%, and a large number of lithium ions are irreversibly consumed during the first charge-discharge process due to interface side reactions, structural defects, etc., making it difficult to fully utilize the high theoretical capacity of the material, which seriously restricts the improvement of battery energy density.

[0005] In summary, existing ultra-high nickel ternary cathode materials still face technical bottlenecks in areas such as "suppression of lithium-nickel mixing, particle size control, and improvement of first-time efficiency." Developing single-crystal ultra-high nickel cathode materials that combine small particle characteristics, high first-time efficiency, and excellent cycle stability is a key requirement for promoting the development of lithium-ion battery technology towards higher energy density and longer lifespan. Summary of the Invention

[0006] The core objective of this invention is to address the key technical problems of existing ultra-high nickel ternary cathode materials, such as severe lithium-nickel mixing, excessively large single-crystal particle size, low initial coulombic efficiency, and insufficient cycle stability. This invention provides a method for preparing a high-efficiency, small-particle, single-crystal ultra-high nickel ternary cathode material, combining high initial efficiency, small particle size, and excellent electrochemical performance. Specifically, by coating the surface of lithium nickel cobalt manganese oxide material with a Li₂WO₄ layer, the interfacial side reactions between the small single-crystal particles and the electrolyte are suppressed. Simultaneously, some W elements are incorporated into the bulk phase of the material. The high-valence W atoms enhance structural stability and prevent transition metal layer collapse, thereby improving the initial coulombic efficiency. Furthermore, the introduction of W elements also raises the crystal growth barrier, effectively inhibiting single-crystal particle growth and enhancing cycle performance through the small-sized single-crystal structure. In addition, mechanically pressing a dense precursor reduces the interfacial fusion resistance during material growth, reduces high-temperature calcination time to alleviate lithium-nickel mixing, and combined with four-stage programmed temperature-controlled calcination, eliminates oxygen vacancies and lattice distortion, further improving the orderliness of the layered structure.

[0007] To achieve its objectives, the present invention employs the following technical solution:

[0008] A method for preparing a high-efficiency, small-particle, single-crystal, ultra-high-nickel ternary cathode material includes the following steps:

[0009] Step 1: First, prepare the ultra-high nickel ternary precursor Ni x Co y Mn 1-x-y (OH)2 (x≥0.9, y≥0, 1-xy>0) is ground and mixed evenly with a lithium source, and then a tungsten source is added and ball-milled and mixed evenly to obtain a precursor powder; the precursor powder is pressed into a dense disc-shaped solid as a calcination precursor.

[0010] Step 2: The calcination precursor is subjected to four-stage temperature-controlled calcination in an oxygen atmosphere: First, the temperature is increased to 420–480°C and held for 4–8 hours at a heating rate of 1–5°C / min; then, the temperature is increased to 750–810°C and held for 4–8 hours; next, the temperature is increased to 880–920°C and held for 4–8 hours; finally, the temperature is decreased to 750–810°C and held for 4–8 hours at a cooling rate of 1–5°C / min. After the calcined product is naturally cooled to room temperature, it is lightly ground to obtain a small-particle single-crystal ultra-high nickel ternary cathode material with a surface coating of Li₂WO₄ and bulk doping with W. The general chemical formula of the ultra-high nickel ternary cathode material is LiNi. x Co y Mn 1-x-y With O2 (x≥0.9, y≥0, 1-xy>0), the average particle size of the resulting cathode material is 0.4-1μm.

[0011] Further, in step 1: the molar ratio of the ultra-high nickel ternary precursor to the lithium source is 1:1.05, the molar ratio of the ultra-high nickel ternary precursor to the tungsten source is 1:0.002-0.01, the lithium source is at least one of lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate, and the tungsten source is at least one of tungstic acid, tungsten oxide, and lithium tungstate.

[0012] Compared with existing technologies, this invention achieves several outstanding and beneficial effects through a combined technical solution of "mechanical pressing densification + four-stage programmed temperature-controlled calcination + tungsten source coating - doping synergistic modification":

[0013] First, mechanical pressing enables the precursor to form a dense structure, which significantly reduces the fusion resistance of the particle interface during subsequent calcination. This not only lowers the calcination temperature required for single crystal growth but also significantly reduces the "lithium-nickel mixing" phenomenon caused by high temperature, ensuring the integrity of the material's layered structure. At the same time, the dense precursor is conducive to the uniform reaction of each component, laying the foundation for the formation of small-sized single crystals.

[0014] Secondly, the introduction of the tungsten source achieves a triple effect of "coating-doping-grain control": the Li2WO4 coating layer formed on the surface can effectively isolate the cathode material and the electrolyte, suppress interfacial side reactions and dissolution of transition metal ions, and improve interfacial stability; the high-valence W atoms in the bulk phase can strengthen the rigidity of the crystal structure, avoid the collapse of the transition metal layer, and significantly improve the first coulombic efficiency; at the same time, the W element will increase the crystal growth barrier, effectively suppress the excessive growth of single crystal particles, obtain a small-size single crystal structure, shorten the lithium-ion transport path, and take into account both high rate performance and cycle stability, solving the problems of poor rate performance and easy breakage of traditional large-size single crystals.

[0015] Furthermore, the four-stage temperature-controlled calcination process, through precise control of gradient heating and cooling, can gradually complete moisture removal, lithiation reaction and single crystal crystallization, and effectively eliminate oxygen vacancies and lattice distortions generated by high-temperature calcination, further enhancing the orderliness of the layered structure, thereby significantly improving the material's cycle capacity and long-term cycle retention rate.

[0016] In summary, the single-crystal ultra-high nickel ternary cathode material prepared by this invention has the characteristics of small particles, high initial efficiency, high rate performance and excellent cycle stability. Its comprehensive electrochemical performance far exceeds that of the existing technology. Moreover, the preparation process is simple, controllable and highly reproducible, and it is suitable for liquid and solid-state battery systems, and has good prospects for large-scale application. Attached Figure Description

[0017] Figure 1 These are scanning electron microscope (SEM) images of the cathode materials prepared in Comparative Example 1 and Examples 1-4 of this invention. Figure 1 (ae) in the figure corresponds to the products obtained in Example 1 and Examples 1-4, respectively;

[0018] Figure 2 The image shows a refined Rietveld X-ray diffraction (XRD) pattern of the cathode material prepared in Example 1 of this invention.

[0019] Figure 3 The image shows a Rietveld refinement of the X-ray diffraction (XRD) pattern of the cathode material prepared in Comparative Example 1 of this invention.

[0020] Figure 4 Transmission electron microscope (TEM) image of the cathode material prepared in Example 2 of this invention ( Figure 4 a) and single-crystal electron diffraction pattern ( Figure 4 (b)

[0021] Figure 5 Here is a high-resolution transmission electron microscope (HRTEM) image of the cathode material prepared in Example 1 of this invention, wherein, Figure 5 a is the HRTEM image of the material surface interface area. Figure 5 b is Figure 5 a) Enlarged HRTEM image of the area within the dashed box (with interplanar spacing marked);

[0022] Figure 6 This is a comparison chart of the cycle performance of liquid coin cells corresponding to Example 1 and Comparative Example 1 of the present invention at a 1C rate.

[0023] Figure 7 This is a comparison chart of the long-cycle performance of the sulfide-based all-solid-state batteries corresponding to Example 1 and Comparative Example 1 of the present invention at a rate of 0.5C.

[0024] Figure 2 and Figure 3 Chinese: R P R is the spectral factor; wp R is the weighted spectral factor; exp Chi2 is the expectation factor; Chi2 is the chi-square value; the red curve Y obs The observed raw XRD intensity curve; black curve Y calc The XRD intensity curves are calculated based on the crystal structure model; the blue curve represents the Y-axis. obs -Y calc The difference between the observed and calculated curves; the green vertical line (Bragg position) corresponds to the Bragg diffraction peak position of the crystal structure; Li / Ni represents the ratio of lithium to nickel mixture in the material (i.e., Ni...). 2+ (The percentage of Li sites occupied); these labels are the standard way to present XRD Rietveld refinement results, used to illustrate the fit quality of the spectrum and the crystal structure characteristics of the material. Detailed Implementation

[0025] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0026] Example 1

[0027] This embodiment describes the preparation of small-particle single-crystal ultra-high nickel ternary cathode material LiNi. 0.9 Co 0.05 Mn 0.05 O2, the specific steps are as follows:

[0028] Step 1: Take 1g of ultra-high nickel ternary precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)₂ and 0.476g of lithium source LiOH·H₂O were thoroughly ground and mixed evenly. Then, 0.01g of tungstic acid was added to the mixture, and the mixture was placed in a ball mill jar and ball-milled at 300r / min for 30 minutes to ensure uniform dispersion of each component, thereby obtaining precursor powder. The precursor powder was transferred to a pressure mold and pressed into a dense, round cake-shaped solid under a pressure of 2MPa, which served as the calcination precursor.

[0029] Step 2: The calcination precursor was subjected to four-stage temperature-controlled calcination in an oxygen atmosphere: The temperature was increased to 450℃ at a rate of 3℃ / min and held for 5 hours; then increased to 800℃ and held for 7.5 hours; then increased to 900℃ and held for 7.5 hours; finally, the temperature was decreased to 800℃ at a rate of 3℃ / min and held for 7.5 hours. After the calcined product cooled naturally to room temperature, it was lightly ground to obtain small-particle single-crystal ultra-high nickel ternary cathode material LiNi with Li₂WO₄ surface coating and W element doping in the bulk phase. 0.9 Co 0.05 Mn 0.05 O2.

[0030] Example 2

[0031] This embodiment describes the preparation of small-particle single-crystal ultra-high nickel ternary cathode material LiNi. 0.9 Co 0.05 Mn 0.05 O2, the specific steps are as follows:

[0032] Step 1: Take 1g of ultra-high nickel ternary precursor Ni 0.9 Co 0.05 Mn 0.05(OH)₂ and 0.476g of lithium source LiOH·H₂O were thoroughly ground and mixed evenly. Then, 0.02g of tungstic acid was added to the mixture, and the mixture was placed in a ball mill jar and ball-milled at 300r / min for 30 minutes to ensure uniform dispersion of each component, thereby obtaining precursor powder. The precursor powder was transferred to a pressure mold and pressed into a dense, round cake-shaped solid under a pressure of 2MPa, which served as the calcination precursor.

[0033] Step 2: The calcination precursor was subjected to four-stage temperature-controlled calcination in an oxygen atmosphere: The temperature was increased to 450℃ at a rate of 3℃ / min and held for 5 hours; then increased to 800℃ and held for 7.5 hours; then increased to 900℃ and held for 7.5 hours; finally, the temperature was decreased to 800℃ at a rate of 3℃ / min and held for 7.5 hours. After the calcined product cooled naturally to room temperature, it was lightly ground to obtain small-particle single-crystal ultra-high nickel ternary cathode material LiNi with Li₂WO₄ surface coating and W element doping in the bulk phase. 0.9 Co 0.05 Mn 0.05 O2.

[0034] Example 3

[0035] This embodiment describes the preparation of small-particle single-crystal ultra-high nickel ternary cathode material LiNi. 0.9 Co 0.05 Mn 0.05 O2, the specific steps are as follows:

[0036] Step 1: Take 1g of ultra-high nickel ternary precursor Ni 0.9 Co y0.05 Mn 0.05 (OH)₂ and 0.476g of lithium source LiOH·H₂O were thoroughly ground and mixed evenly. Then, 0.005g of tungstic acid was added to the mixture, and the mixture was placed in a ball mill jar and ball-milled at 300r / min for 30 minutes to ensure uniform dispersion of each component, thereby obtaining precursor powder. The precursor powder was transferred to a pressure mold and pressed into a dense, round cake-shaped solid under a pressure of 2MPa, which served as the calcination precursor.

[0037] Step 2: The calcination precursor was subjected to four-stage temperature-controlled calcination in an oxygen atmosphere: The temperature was increased to 450℃ at a rate of 3℃ / min and held for 5 hours; then increased to 800℃ and held for 7.5 hours; then increased to 900℃ and held for 7.5 hours; finally, the temperature was decreased to 800℃ at a rate of 3℃ / min and held for 7.5 hours. After the calcined product cooled naturally to room temperature, it was lightly ground to obtain small-particle single-crystal ultra-high nickel ternary cathode material LiNi with Li₂WO₄ surface coating and W element doping in the bulk phase. 0.9 Co 0.05 Mn 0.05O2.

[0038] Example 4

[0039] This embodiment prepares a single-crystal ultra-high nickel ternary cathode material, LiNi, which does not contain W. 0.9 Co 0.05 Mn 0.05 O2, the specific steps are as follows:

[0040] Step 1: Take 1g of ultra-high nickel ternary precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and 0.476g of lithium source LiOH·H2O were thoroughly ground and mixed to obtain a precursor powder. The precursor powder was transferred to a pressure mold and pressed into a dense, round cake-shaped solid under a pressure of 2MPa, which served as the calcination precursor.

[0041] Step 2: The calcination precursor was subjected to four-stage temperature-controlled calcination in an oxygen atmosphere: The temperature was increased to 450℃ at a rate of 3℃ / min and held for 5 hours; then increased to 800℃ and held for 7.5 hours; next, increased to 900℃ and held for 7.5 hours; finally, the temperature was decreased to 800℃ at a rate of 3℃ / min and held for 7.5 hours. After the calcined product cooled naturally to room temperature, it was lightly ground to obtain a W-free single-crystal ultra-high nickel ternary cathode material, LiNi. 0.9 Co 0.05 Mn 0.05 O2.

[0042] Comparative Example 1

[0043] This comparative example uses the currently mainstream two-stage calcination method to prepare single-crystal ultra-high nickel ternary cathode material.

[0044] Step 1: Add 1g of ultra-high nickel ternary precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2 and 0.476g of lithium source LiOH·H2O are thoroughly ground and mixed to obtain a mixed powder.

[0045] Step 2: Calcine the mixed powder under controlled temperature in an oxygen atmosphere: First, heat to 500℃ and hold for 5 hours at a heating rate of 3℃ / min, then heat to 900℃ and hold for 10 hours. After the calcined product cools naturally to room temperature, it is lightly ground to obtain large-particle single-crystal ultra-high nickel ternary cathode material LiNi. 0.9 Co 0.05 Mn 0.05 O2.

[0046] The LiNi obtained in each embodiment 0.9 Co 0.05 Mn0.05 The O2 (hereinafter referred to as Ni90 single crystal) product was characterized and its performance was tested as follows:

[0047] I. Material Characterization Results

[0048] Figure 1 (ae) are SEM images of the products obtained in Comparative Example 1 and Examples 1-4, respectively: In Comparative Example 1 (without W element introduction + two-stage calcination), the Ni90 single crystal particle size is 3-6 μm, and the distribution is relatively uniform. Figure 1 a); After the introduction of W, the single crystal particle size of Examples 1-3 was significantly reduced to 0.4-1 μm, exhibiting small particle characteristics ( Figure 1 bd); The particle size of Example 4 (without the introduction of W element, using four-stage calcination) is between the two ( Figure 1 e).

[0049] Figure 2 , Figure 3 The XRD Rietveld refinement images of the products obtained in Example 1 and Comparative Example 1 are shown respectively: The lithium-nickel mixing degree in Example 1 is only 1.4%, while that in Comparative Example 1 is 4.9%, indicating that bulk doping of W can effectively suppress Li / Ni mixing and improve the stability of the crystal structure.

[0050] Figure 4 The TEM and single-crystal electron diffraction patterns of the product obtained in Example 1 are shown below. The product has a single-crystal structure with a grain diameter of about 1.5 μm. The particles have an irregular shape but clear grain boundaries, which further verifies the single-crystal characteristics.

[0051] Figure 5 The HRTEM image of the product obtained in Example 1 shows that there is an obvious coating layer on the surface of the material, and the interplanar spacing matches the (108) crystal plane of Li2WO4, indicating that W element achieves synergistic modification of "bulk doping + surface Li2WO4 coating" during calcination.

[0052] II. Electrochemical Performance Testing

[0053] (1) Liquid coin cell battery test

[0054] The active material (the product obtained in each example and Comparative Example 1), conductive agent acetylene black, and binder polytetrafluoroethylene were mixed and ground evenly at a mass ratio of 8:1:1, coated onto aluminum foil, dried at 80°C for 4 h, and then cut into circular electrode sheets with a diameter of 12 mm using a stamping machine. These were then vacuum dried at 80°C for 12 h. A complete CR2032 button cell was assembled using a polypropylene membrane (Celgard 2400) as the separator, a lithium metal sheet as the counter electrode, and a 1 mol / L lithium hexafluorophosphate solution of ethylene carbonate, dimethyl carbonate, and diethyl carbonate (volume ratio 1:1:1) as the electrolyte. The electrochemical performance of the assembled button cell was tested using a Newway battery testing system. The test conditions were: voltage range 2.8~4.3 V; initial charge / discharge test at 0.1C (1C=180 mAh / g); subsequent activation at 0.1C for 3 cycles, followed by continued cycling at 1C; and the ambient temperature was 25°C. The test results are shown in Table 1 and Figure 6 As shown.

[0055] Table 1. Electrochemical performance of liquid coin cells in Examples 1-4 and Comparative Example 1

[0056]

[0057] Analysis of Table 1 shows that at a 0.1C rate, Examples 1-3, which introduced W, significantly outperformed Examples 4 and Comparative Example 1 (without W) in terms of first-cycle charge-discharge specific capacity and first-cycle coulombic efficiency. Among them, Example 2 achieved the highest first-cycle discharge specific capacity (234.1 mAh / g) and first-cycle efficiency (94.1%) within the group, demonstrating the role of W in suppressing lithium-nickel mixing and reducing irreversible lithium-ion loss. Meanwhile, Example 1 had the best 1C cycle retention rate (89.4%) within the group, while Example 2, due to its high W content, had a 1C retention rate of only 71.5%. Example 4 (without W) had a 1C retention rate (77.1%) that was better than Comparative Example 1 but weaker than the group containing W, indicating that the amount of W added needs to be appropriate, and that the four-stage calcination itself can also improve stability to a certain extent.

[0058] Combination Figure 6 (Test results after 3 cycles at 0.1C followed by 1C) Example 1 achieved an initial discharge specific capacity of 202 mAh / g at 1C, which is close to 89.5% of its 0.1C capacity, demonstrating good rate adaptability. After 100 cycles, the remaining capacity was 181 mAh / g, with a capacity retention rate of 89.4%. Comparative Example 1 had an initial discharge specific capacity of 188 mAh / g at 1C, and only 124 mAh / g remained after 100 cycles, showing significantly faster capacity decay. This further confirms that the W element modification and four-stage calcination in Example 1 synergistically improved the high-rate cycling stability of the material, while the structural instability problem of Comparative Example 1 without W at high rates was amplified.

[0059] (2) Testing of sulfide-based all-solid-state batteries

[0060] The products obtained in Example 1 and Comparative Example 1 were uniformly mixed with Li3InCl6 and carbon nanotubes (VGCF) in a mixer at a mass ratio of 70:29:1 to form the positive electrode, and lithium indium alloy was used as the negative electrode. Li6PS5Cl solid electrolyte was used, and Li3InCl6 electrolyte was added to the positive electrode side as a sandwich layer. Solid-state batteries were assembled under a pressure of 40 tons. The test voltage range was 2.18-3.68V, the temperature was 25℃, the positive electrode loading was 8.6 mg, and 1C=180 mAh / g.

[0061] Figure 7 The following are the cycling performance curves of the cathode materials in Example 1 and Comparative Example 1 of the present invention at a current density of 0.5C: At 0.5C, the initial discharge capacity of Example 1 is 166 mAh / g, and the capacity retention rate is still 78.4% after 780 cycles; the initial discharge capacity of Comparative Example 1 is 125 mAh / g, and the cycling performance is significantly worse than that of Example 1, proving that the material of the present invention also has excellent long-term cycling stability in solid-state battery systems.

[0062] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-efficiency, small-particle, single-crystal, ultra-high-nickel ternary cathode material, characterized in that, Includes the following steps: Step 1: First, prepare the ultra-high nickel ternary precursor Ni x Co y Mn 1-x-y (OH)2 is ground and mixed evenly with lithium source, then tungsten source is added and ball-milled and mixed evenly to obtain precursor powder; the precursor powder is pressed into a dense disc-shaped solid as a calcination precursor; wherein, the molar ratio of ultra-high nickel ternary precursor to tungsten source is 1:0.002-0.

01. Step 2: The calcination precursor is subjected to four-stage temperature-controlled calcination in an oxygen atmosphere: First, the temperature is increased to 420–480°C and held for 4–8 hours at a heating rate of 1–5°C / min; then, the temperature is increased to 750–810°C and held for 4–8 hours; next, the temperature is increased to 880–920°C and held for 4–8 hours; finally, the temperature is decreased to 750–810°C and held for 4–8 hours at a cooling rate of 1–5°C / min. After the calcined product is naturally cooled to room temperature, it is ground to obtain a small-particle single-crystal ultra-high nickel ternary cathode material with a surface coating of Li₂WO₄ and a bulk doped W element. The general chemical formula of the ultra-high nickel ternary cathode material is LiNi. x Co y Mn 1-x-y O2, where x≥0.9, y≥0, and 1-xy>0.

2. The preparation method according to claim 1, characterized in that: In step 1, the molar ratio of the ultra-high nickel ternary precursor to the lithium source is 1:1.

05.

3. The preparation method according to claim 1, characterized in that: In step 1, the lithium source is at least one of lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate.

4. The preparation method according to claim 1, characterized in that: In step 1, the tungsten source is at least one of tungstic acid, tungsten oxide, and lithium tungstate.

5. A small-particle single-crystal ultra-high nickel ternary cathode material prepared by the preparation method according to any one of claims 1 to 4.

6. The small-particle single-crystal ultra-high nickel ternary cathode material according to claim 5, characterized in that: The average particle size of the small-particle single-crystal ultra-high nickel ternary cathode material is 0.4-1 μm.

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