High-nickel positive electrode material, preparation method thereof, positive electrode sheet and solid-state lithium ion battery

Abstract

This invention relates to the field of battery material technology, and particularly to high-nickel cathode materials and their preparation methods, cathode sheets, and solid-state lithium-ion batteries. The preparation method includes weighing nickel salt, cobalt salt, and manganese salt, adding them to deionized water to prepare a metal salt solution; pumping the metal salt solution and ammonia solution together into a reaction vessel, controlling the reaction temperature at 45–55°C, adding an alkaline solution to adjust the pH of the reaction system to 11.00–11.80, stirring and reacting continuously for 35–45 hours; filtering, washing, and vacuum drying the resulting reaction product to obtain a precursor; mixing and grinding the precursor with LiOH·H2O, followed by calcination, to obtain the high-nickel cathode material, namely Li[Ni x Co y Mn z O2. The high-nickel cathode material of this invention combines high specific capacity with excellent long-cycle stability, effectively solving the problems of easy structural degradation and short cycle life of high-nickel materials under traditional processes, and has important industrial application value.

Description

Technical Field

[0001] This invention relates to the field of battery preparation materials technology, and in particular to high-nickel cathode materials and their preparation methods, cathode sheets and solid-state lithium-ion batteries. Background Technology

[0002] With the rapid development of mobile devices, electric vehicles, and grid energy storage, higher demands are being placed on the energy density, safety, and cycle life of lithium-ion batteries. While traditional liquid lithium-ion batteries have achieved widespread application, their energy density improvement faces bottlenecks, and organic electrolytes pose safety hazards such as leakage and flammability. Solid-state lithium-ion batteries, which use solid electrolytes instead of liquid electrolytes, hold the promise of fundamentally solving the safety issues of liquid lithium-ion batteries and further improving battery performance by being compatible with high-energy-density electrode materials (such as lithium metal anodes). Therefore, they have become a research hotspot for next-generation energy storage technologies.

[0003] Cathode materials are a key component determining the energy density, power density, and cycle stability of solid-state batteries. High-nickel layered oxide cathodes (such as LiNi) x Co y Mn z O2 (x>0.8) is considered a strong candidate for realizing high-energy-density solid-state batteries due to its advantages of high specific capacity (>200 mAh / g) and relatively low cost. However, in solid-state battery systems, the cathode material needs to be closely combined with the solid electrolyte to form a composite cathode, and its preparation process still faces many challenges such as interface contact problems and material structure stability. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a high-nickel cathode material and its preparation method, a cathode sheet and a solid-state lithium-ion battery. The prepared high-nickel cathode material exhibits a lower residual lithium content and demonstrates good discharge specific capacity and excellent cycle stability in solid-state batteries.

[0005] The following is a summary of this disclosure to provide a basic understanding of some aspects. This summary is not intended to identify key or important elements, nor is it intended to limit the implementation or any aspects of the claims. Furthermore, this summary provides a simplified overview of some aspects that can be described in more detail in other parts of this disclosure.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] In a first aspect, embodiments of the present invention provide a method for preparing a high-nickel cathode material, comprising the following steps:

[0008] According to the chemical formula Li[Ni x Co y Mnz O2, where 0.8≤x≤0.95, 0.025≤y≤0.1, 0.025≤z≤0.1, weigh out nickel salt, cobalt salt and manganese salt, add to deionized water to prepare metal salt solution;

[0009] A metal salt solution and an ammonia solution were pumped together into a reaction vessel, and the reaction temperature was controlled at 45–55 °C. An alkaline solution was added to adjust the pH of the reaction system to 11.00–11.80. The mixture was stirred and reacted continuously for 35–45 h. The resulting reaction product was filtered, washed, and vacuum dried to obtain the precursor [Ni]. x Co y Mn z (OH)2;

[0010] The precursor was mixed with LiOH·H2O, ground, and then calcined to obtain a high-nickel cathode material, namely Li[Ni]. x Co y Mn z O2.

[0011] In conjunction with the first aspect, in some embodiments, the nickel salt is NiSO4·6H2O, the cobalt salt is CoSO4·7H2O, the manganese salt is MnSO4·H2O, the molar ratio of the nickel salt, cobalt salt, and manganese salt is 0.90:0.05:0.05, and the precursor is [Ni 0.90 Co 0.05 Mn 0.05 ](OH)2.

[0012] In conjunction with the first aspect, in some embodiments, the concentration of the ammonia solution is 0.8–4.0 mol / L; and / or,

[0013] The alkaline solution is a sodium hydroxide solution with a concentration of 4 mol / L; and / or,

[0014] The precursor and LiOH·H2O are mixed in a molar ratio of TM:Li = 1:(1.02~1.05).

[0015] In conjunction with the first aspect, in some embodiments, the calcination includes a first calcination and a second calcination performed sequentially, wherein the first calcination is carried out at 450–500°C for 4–6 hours, and the second calcination is carried out at 740–800°C for 12–18 hours.

[0016] In conjunction with the first aspect, in some embodiments, the total concentration of metal ions in the metal salt solution is 1.5 to 2.0 mol / L, and the metal salt solution also contains 0.05 to 0.1 mol / L of an auxiliary complexing agent, which is at least one of citric acid, ethylenediamine, and tartaric acid.

[0017] The above technical solution involves compounding a trace amount of organic auxiliary complexing agent in ammonia water to construct an ammonia-organic dual complexing system. This dual complexing buffer precisely controls the release rate of metal ions, preparing a high-density, high-sphericity, and monodisperse precursor. It also inhibits abnormal grain growth, reduces precursor porosity, and improves the compaction density of the cathode material.

[0018] In conjunction with the first aspect, in some embodiments, the reaction product is prepared as follows:

[0019] During the nucleation stage, the metal salt solution and ammonia solution are pumped into the reaction vessel at a feed rate of 1.2–1.5 mL / min using a dual peristaltic pump. The pH of the reaction system is controlled at 11.70–11.80, and the stirring speed is 600–650 rpm. The nucleation stage is when the total amount of metal salt solution and ammonia solution fed is 15–25%.

[0020] During the growth stage, metal salt solution and ammonia solution are pumped into the reaction vessel at a feed rate of 1.8–2.0 mL / min using a dual peristaltic pump. The pH of the reaction system is controlled at 11.40–11.50, and the stirring speed is 700–750 rpm. After the feed is completed, the mixture is stirred and reacted continuously for 35–45 h to obtain the reaction solution.

[0021] The above technical solution employs a gradient pumping process involving low-speed nucleation followed by high-speed growth, synchronized with segmented stirring speeds and segmented pH gradient control. On one hand, it solves the problems of wide particle size distribution and mixed particles of different sizes in traditional constant-rate feeding, achieving a narrower particle size distribution coefficient and significantly improving the electrochemical consistency of the material. On the other hand, the high pH enables rapid and uniform nucleation, while the low pH allows for slow crystal growth, realizing a core-shell hierarchical precursor structure, optimizing lattice stress, and improving cycle stability and thermal stability.

[0022] In conjunction with the first aspect, in some embodiments, the vacuum drying is a gradient temperature vacuum drying, comprising: vacuum drying at 35–45°C for 1–2 hours, followed by vacuum drying at 55–65°C for 2.5–3.5 hours, and finally vacuum drying at 75–85°C for 7–10 hours. Gradient temperature vacuum drying avoids hard agglomeration of the precursor, regulates the morphology of secondary particles, and improves the processing performance of the cathode material.

[0023] Secondly, embodiments of the present invention provide a high-nickel cathode material, wherein the chemical formula of the high-nickel cathode material is Li[Ni] x Co y Mn z O2, wherein 0.8≤x≤0.95, 0.025≤y≤0.1, 0.025≤z≤0.1; the high-nickel cathode material is prepared by the preparation method described in the first aspect.

[0024] Thirdly, embodiments of the present invention provide a positive electrode sheet, wherein the raw materials for preparing the positive electrode sheet include the high-nickel positive electrode material as described in the second aspect.

[0025] Fourthly, embodiments of the present invention provide a solid-state lithium-ion battery, the solid-state lithium-ion battery comprising a positive electrode as described in the third aspect.

[0026] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0027] The preparation method of the high-nickel cathode material of the present invention, through hydroxide co-precipitation, can precisely control the thickness of the primary precursor particles. The main principle is that in the reaction system, transition metal ions first react with NH4+. 4+ Complexation forms a complex [TM(NH3)] n ] 2+ High ammonia concentrations will promote complexation reactions and inhibit rapid nucleation. In the precursor crystal structure, the (001) facet is polar, while the (100) and (010) faces are nonpolar. [TM(NH3)] n ] 2+ It tends to adsorb on the (001) crystal plane and undergo precipitation reaction, thereby promoting the growth of the precursor primary particles along the

[001] direction. Therefore, precursors of different thicknesses can be obtained by controlling the ammonia concentration in the reaction system. High-nickel cathode materials with different primary particle sizes are obtained after lithium mixing and calcination. The entire preparation process is simple, easy to control, and easy to operate.

[0028] The high-nickel cathode material of this invention has a moderate particle thickness, which effectively balances the problems of smaller primary particles leading to more grain boundaries and thus easier crack formation, and larger primary particles leading to excessively long transport paths. It also reduces residual lithium content, resulting in higher energy density and cycle stability in solid-state battery applications. This high-nickel cathode material combines high specific capacity with excellent long-term cycle stability, effectively solving the problems of easy structural degradation and short cycle life of high-nickel materials under traditional processes, and has significant industrial application value. Attached Figure Description

[0029] Figure 1 Here is a SEM image of the precursor prepared in Example 1;

[0030] Figure 2 The image shows a SEM image of the precursor prepared in Comparative Example 1.

[0031] Figure 3 The image shows a SEM image of the precursor prepared in Comparative Example 2.

[0032] Figure 4These are XRD patterns of the precursors prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0033] Figure 5 These are SEM images of the high-nickel cathode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2;

[0034] Figure 6 The graph shows the electrochemical performance test results of batteries containing high-nickel cathode materials prepared in Examples 1, 1, and 2. Detailed Implementation

[0035] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0036] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0037] Example 1

[0038] The high-nickel cathode material in this embodiment is prepared using the following specific method:

[0039] Weigh 2401g of NiSO4·6H2O, 141g of CoSO4·7H2O and 85g of MnSO4·H2O, disperse them in deionized water and stir to dissolve. After complete dissolution, add deionized water to make up to 5L. Add 0.40mol of citric acid and stir evenly to obtain a metal salt solution with a total metal ion concentration of 2.0mol / L.

[0040] Dilute 1130 mL of ammonia water with deionized water and bring the volume to 5 L. Stir well to obtain a 3.2 mol / L ammonia solution.

[0041] Disperse 816g of NaOH in deionized water and stir to dissolve. After complete dissolution and cooling to room temperature, add deionized water to make up to 5L. Stir well to obtain a 4mol / L alkaline solution.

[0042] Metal salt solution and ammonia solution were continuously pumped into a stainless steel reactor using a dual peristaltic pump. During the nucleation stage, the feed rate of the metal salt solution and ammonia solution was 1.3 mL / min, the pH of the reaction system was controlled at 11.75, and the stirring speed was 620 rpm, completing 20% ​​of the total feed. During the growth stage, the feed rate of the metal salt solution and ammonia solution was 1.9 mL / min, the pH of the reaction system was controlled at 11.45, and the stirring speed was 720 rpm. After all feed was completed, the mixture was stirred and reacted continuously for 40 h to obtain the reaction solution. The reaction solid was obtained by vacuum filtration, washed with deionized water, and then vacuum dried at 40℃ for 1.5 h, followed by vacuum drying at 60℃ for 3.0 h, and finally vacuum drying at 80℃ for 8 h to obtain the precursor [Ni]. 0.90 Co 0.05 Mn 0.05 ](OH)2.

[0043] Weigh 1g of the dried precursor and 0.4708g of LiOH·H2O, grind them thoroughly, and then calcine them at 480℃ for 5h in an oxygen atmosphere, followed by calcine at 760℃ for 15h to finally obtain the high-nickel cathode material.

[0044] Example 2

[0045] The high-nickel cathode material in this embodiment is prepared using the following specific method:

[0046] Weigh 2401g of NiSO4·6H2O, 141g of CoSO4·7H2O and 85g of MnSO4·H2O, disperse them in deionized water and stir to dissolve. After complete dissolution, add deionized water to make up to 5L. Add 0.50mol of ethylenediamine and stir evenly to obtain a metal salt solution with a total metal ion concentration of 2.0mol / L.

[0047] Dilute 1130 mL of ammonia water with deionized water and bring the volume to 5 L. Stir well to obtain a 3.2 mol / L ammonia solution.

[0048] Disperse 816g of NaOH in deionized water and stir to dissolve. After complete dissolution and cooling to room temperature, add deionized water to make up to 5L. Stir well to obtain a 4mol / L alkaline solution.

[0049] Metal salt solution and ammonia solution were continuously pumped into a stainless steel reactor using a dual peristaltic pump. During the nucleation stage, the feed rate of the metal salt solution and ammonia solution was 1.2 mL / min, the pH of the reaction system was controlled at 11.70, and the stirring speed was 600 rpm, completing 15% of the total feed. During the growth stage, the feed rate of the metal salt solution and ammonia solution was 1.8 mL / min, the pH of the reaction system was controlled at 11.40, and the stirring speed was 700 rpm. After all feed was completed, the mixture was stirred and reacted continuously for 35 h to obtain the reaction solution. The reaction solid was obtained by vacuum filtration, washed with deionized water, and then vacuum dried at 35℃ for 1.0 h, followed by vacuum drying at 55℃ for 2.5 h, and finally vacuum drying at 75℃ for 7 h to obtain the precursor [Ni]. 0.90 Co 0.05 Mn 0.05 ](OH)2.

[0050] Weigh 1g of the dried precursor and 0.4708g of LiOH·H2O, grind them thoroughly, and calcine them at 450℃ for 4h in an oxygen atmosphere, followed by calcine at 760℃ for 12h to finally obtain the high-nickel cathode material.

[0051] Example 3

[0052] The high-nickel cathode material in this embodiment is prepared using the following specific method:

[0053] Weigh 1080g of NiSO4·6H2O, 141g of CoSO4·7H2O and 85g of MnSO4·H2O, disperse them in deionized water and stir to dissolve. After complete dissolution, add deionized water to make up to 3.5L. Add a mixture of 0.175mol citric acid and tartaric acid (mass ratio 1:1) and stir evenly to obtain a metal salt solution with a total metal ion concentration of 1.5mol / L.

[0054] Dilute 590 mL of ammonia water with deionized water and bring the volume to 9.8 L. Stir well to obtain a 0.8 mol / L ammonia solution.

[0055] Disperse 816g of NaOH in deionized water and stir to dissolve. After complete dissolution and cooling to room temperature, add deionized water to make up to 5L. Stir well to obtain a 4.0mol / L alkaline solution.

[0056] Metal salt solution and ammonia solution were continuously pumped into a stainless steel reactor using a dual peristaltic pump. During the nucleation stage, the feed rate of the metal salt solution and ammonia solution was 1.5 mL / min, the pH of the reaction system was controlled at 11.80, and the stirring speed was 650 rpm, completing 16% of the total feed. During the growth stage, the feed rate of the metal salt solution and ammonia solution was 2.0 mL / min, the pH of the reaction system was controlled at 11.50, and the stirring speed was 750 rpm. After all feed was completed, the mixture was stirred and reacted continuously for 40 h to obtain the reaction solution. The reaction solid was obtained by vacuum filtration, washed with deionized water, and then vacuum dried at 45℃ for 2.0 h, followed by vacuum drying at 65℃ for 3.5 h, and finally vacuum drying at 85℃ for 10 h to obtain the precursor [Ni]. 0.80 Co 0.10 Mn 0.10 ](OH)2.

[0057] Weigh 1g of the dried precursor and 0.4708gg of LiOH·H2O, grind them thoroughly, and then calcine them at 480℃ for 5h in an oxygen atmosphere, followed by calcine at 800℃ for 16h to finally obtain the high-nickel cathode material.

[0058] Example 4

[0059] The high-nickel cathode material in this embodiment is prepared using the following specific method:

[0060] Weigh out 4930g of NiSO4·6H2O, 141g of CoSO4·7H2O and 85g of MnSO4·H2O, disperse them in deionized water and stir to dissolve. After complete dissolution, add deionized water to make up to 12.4L, add 1.0mol of ethylenediamine, stir evenly, and you will get a metal salt solution with a total metal ion concentration of 1.6mol / L.

[0061] Dilute 2707 mL of ammonia water with deionized water and bring the volume to 9.0 L. Stir well to obtain a 4.0 mol / L ammonia solution.

[0062] Disperse 816g of NaOH in deionized water and stir to dissolve. After complete dissolution and cooling to room temperature, add deionized water to make up to 5L. Stir well to obtain a 4mol / L alkaline solution.

[0063] Metal salt solution and ammonia solution were continuously pumped into a stainless steel reactor using a dual peristaltic pump. During the nucleation stage, the feed rate of the metal salt solution and ammonia solution was 1.4 mL / min, the pH of the reaction system was controlled at 11.75, and the stirring speed was 620 rpm, completing 25% of the total feed. During the growth stage, the feed rate of the metal salt solution and ammonia solution was 2.0 mL / min, the pH of the reaction system was controlled at 11.50, and the stirring speed was 750 rpm. After all feed was completed, the mixture was stirred and reacted continuously for 45 h to obtain the reaction solution. The reaction solid was obtained by vacuum filtration, washed with deionized water, and then vacuum dried at 45℃ for 2.0 h, followed by vacuum drying at 65℃ for 3.5 h, and finally vacuum drying at 85℃ for 10 h to obtain the precursor [Ni]. 0.95 Co 0.025 Mn 0.025 ](OH)2.

[0064] Weigh 1g of the dried precursor and 0.4708g of LiOH·H2O, grind them thoroughly, and calcine them at 500℃ for 6h in an oxygen atmosphere, followed by calcine at 740℃ for 18h to finally obtain the high-nickel cathode material.

[0065] Comparative Example 1

[0066] The cathode material for this comparative example was prepared as follows:

[0067] Disperse 2401g of NiSO4·6H2O, 141g of CoSO4·7H2O and 85g of MnSO4·H2O in deionized water and stir to dissolve. After complete dissolution, add 5L of deionized water to make up the volume and stir evenly to obtain a 2mol / L metal salt solution.

[0068] Dilute 1412 mL of ammonia water with deionized water and bring the volume to 5 L. Stir well to obtain a 4.0 mol / L ammonia solution.

[0069] Disperse 816g of NaOH in deionized water and stir to dissolve. After complete dissolution and cooling to room temperature, add deionized water to make up to 5L. Stir well to obtain a 4mol / L NaOH solution.

[0070] The metal salt solution and ammonia solution were continuously pumped into a 20L stainless steel reactor at a feed rate of 1.7 mL / min, and the reaction temperature was controlled at 50°C using a water bath. o C. Simultaneously, the pH value inside the reactor was adjusted to 11.80±0.01 by feeding NaOH solution, and the stirring speed was controlled at 700 rpm for continuous reaction for 40 hours.

[0071] After the reaction was completed, the reaction product was filtered under vacuum, washed, and then placed at 80°C. o[Ni] was obtained by drying in an oven at C for 12 hours. 0.90 Co 0.05 Mn 0.05 (OH)2 precursor.

[0072] Weigh 1g of the dried precursor and 0.4708g of LiOH·H2O, grind them thoroughly, and then heat them at 480°C in an oxygen atmosphere. o Calcination at C for 5 hours, followed by 760 °C o After calcining at C for 15 hours, the high-nickel cathode material corresponding to Comparative Example 1 was finally obtained.

[0073] Comparative Example 2

[0074] The cathode material for this comparative example was prepared as follows:

[0075] Disperse 2401g of NiSO4·6H2O, 141g of CoSO4·7H2O and 85g of MnSO4·H2O in deionized water and stir to dissolve. After complete dissolution, add 5L of deionized water to make up the volume and stir evenly to obtain a 2mol / L metal salt solution.

[0076] Dilute 282 mL of ammonia water with deionized water and bring the volume to 5 L. Stir well to obtain a 0.8 mol / L ammonia solution.

[0077] Disperse 816g of NaOH in deionized water and stir to dissolve. After complete dissolution and cooling to room temperature, add deionized water to make up to 5L. Stir well to obtain a 4mol / L NaOH solution.

[0078] The metal salt solution and ammonia solution were continuously pumped into a 20L stainless steel reactor at a feed rate of 1.7 mL / min, and the reaction temperature was controlled at 50°C using a water bath. o C. Simultaneously, the pH value inside the reactor was adjusted to 11.00±0.01 by feeding NaOH solution, and the stirring speed was controlled at 700 rpm for continuous reaction for 40 hours.

[0079] After the reaction was completed, the reaction product was filtered under vacuum, washed, and then placed at 80°C. o [Ni] was obtained by drying in an oven at C for 12 hours. 0.90 Co 0.05 Mn 0.05 (OH)2 precursor.

[0080] Weigh 1g of the dried precursor and 0.4708g of LiOH·H2O, grind them thoroughly, and then heat them at 480°C in an oxygen atmosphere. o Calcination at C for 5 hours, followed by 760 °C o After calcining at C for 15 hours, the high-nickel cathode material corresponding to Comparative Example 2 was finally obtained.

[0081] Performance testing:

[0082] (1) Using the precursors prepared in Example 1, Comparative Example 1, and Comparative Example 2 as samples, the SEM images of the precursors prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown below. Figure 1-3 As shown.

[0083] from Figure 1-3 As can be seen, the secondary particles of the high-nickel precursor prepared in Example 1 of this invention are regularly spherical, with uniform primary grain size and dense, orderly arrangement. The sphericity and density are significantly better than those of Comparative Examples 1 and 2. This indicates that by using a citric acid-ammonia dual-complexation system, combined with segmented pH and feed rate control during the nucleation and growth stages, the growth process of the precursor grains can be effectively regulated, abnormal grain growth and disordered accumulation can be suppressed, and precursor particles with a dense structure and uniform morphology can be formed. During subsequent calcination, this precursor structure can more stably transform into a layered high-nickel cathode material, reducing the generation of microcracks and lithium-nickel mixing, thereby significantly improving the material's compaction density, cycle stability, and rate performance.

[0084] (2) The XRD patterns of the precursors prepared in Example 1, Comparative Example 1 and Comparative Example 2 are shown below. Figure 4 As shown.

[0085] from Figure 4 As can be seen, the high-nickel precursor prepared in Example 1 of this invention exhibits typical hexagonal hydroxide diffraction peaks. All crystal planes have sharp peaks, high intensity, and good symmetry, with no impurity peaks or broadening, indicating high crystallinity, ordered crystal structure, and complete layered structure development. In contrast, the precursor in Comparative Example 1 shows reduced intensity and broadened peaks in high-angle diffraction, indicating a decrease in crystallinity; the precursor in Comparative Example 2 shows almost no high-angle diffraction peaks, indicating poor crystallinity and low structural order. This demonstrates that using a citric acid-ammonia dual-complexation system, combined with segmented pH and feed rate control during the nucleation and growth stages, can significantly improve the crystallinity and ordered crystal structure of the precursor, reduce lattice defects, and lay a good structural foundation for subsequent calcination to form a high-performance high-nickel cathode material.

[0086] (3) The grain size was calculated using the Scherrer formula. The results of the

[001] direction grain size calculation of the precursors prepared in Example 1, Comparative Example 1 and Comparative Example 2 are shown in Table 1.

[0087] Table 1

[001] Calculation Results of Directional Grain Size

[0088]

[0089] As can be seen from the data in Table 1, the

[001] crystal grain size of the high-nickel precursor prepared in Example 1 of this invention, calculated using the Scherrer formula, is 16.93 Å. The grain size is moderate and narrowly distributed, with no abnormal growth or poor development. In contrast, the precursor of Comparative Example 1 has abnormally large grains (19.78 Å), uneven size, and loose arrangement; the precursor of Comparative Example 2 has poor crystallinity, poor grain development (16.27 Å), and a loose and porous structure.

[0090] (4) The high-nickel cathode materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 were used as samples for residual lithium titration tests to characterize the content of unreacted free lithium salts (such as LiOH and Li2CO3) on the material surface. This is a key indicator for evaluating the performance and process quality of high-nickel materials. The test structure is shown in Table 2.

[0091] Table 2 Results of residual lithium titration test

[0092]

[0093] The data in Table 2 show that the residual lithium mass fraction of the high-nickel cathode material prepared in Example 1 of this invention is 1.09%, significantly lower than that of Comparative Example 1 (1.23%) and Comparative Example 2 (1.26%). The lower residual lithium content indicates that the precursor in Example 1 underwent a more complete lithiation reaction during calcination, and the material surface structure was more stable, effectively suppressing the formation of free lithium salts. This is closely related to the dense and ordered microstructure and highly crystalline crystal structure of the precursor stage. The lower residual lithium content can significantly reduce the risk of gas generation during battery formation, reduce interfacial side reactions, lower battery impedance, and improve the rate performance and cycle stability of the material.

[0094] (5) Using the high-nickel cathode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 as samples, the SEM images of the high-nickel cathode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown below. Figure 5 As shown.

[0095] from Figure 1-3 and Figure 5 As can be seen, Example 1 of this invention achieves precise control over precursor grain growth, producing precursor particles with uniform grain size and dense, orderly arrangement. This precursor can stably transform into structurally complete, crack-free spherical high-nickel cathode materials during calcination. In contrast, the precursor grains in Comparative Example 1 are uneven, exhibiting potential microcracks after calcination; the precursor structure in Comparative Example 2 is loose, resulting in particle breakage and agglomeration after calcination. These results demonstrate that the process of this invention can effectively optimize the microstructure of the precursor and cathode materials, significantly improving the compaction density and structural stability of the materials, providing a crucial guarantee for the preparation of high-performance high-nickel cathode materials.

[0096] (6) The high-nickel cathode material prepared in Example 1, Comparative Example 1, and Comparative Example 2, acetylene black, lithium lanthanum zirconium tantalum oxide, polyvinylidene fluoride (PVDF), and lithium bis(trifluoromethanesulfonyl)imide were mixed in a ratio of 80:8:2:9.9:0.1 to form a slurry, which was then uniformly coated onto aluminum foil. At 120°C... o After drying in an oven at room temperature for 12 hours, the electrodes were punched into 12mm diameter sheets, which were used as the positive electrode. A lithium sheet was used as the negative electrode. The solid electrolyte was prepared from polyvinylidene fluoride, lithium lanthanum zirconium tantalum oxide, and lithium difluorosulfonyl imide in a ratio of 54:14:32. After assembling into coin cells in an argon-atmosphere glove box, constant current charge-discharge tests were performed on a Newway battery testing system (CT3008-W). The voltage range was 2.8-4.3V, and the room temperature was kept constant for 30 minutes. o C. The final electrochemical performance test results are shown in the figure below. Figure 6 As shown.

[0097] Figure 6 Data shows that the high-nickel cathode material prepared in Example 1 of this invention has an initial discharge specific capacity of 208 mAh·g. - ¹ The initial coulombic efficiency was 85.73%, and the capacity retention after 100 cycles was as high as 95.26%, significantly better than Comparative Example 1 (86.57%) and Comparative Example 2 (77.68%). Combined with the previous SEM and XRD characterization results, it can be seen that the excellent cycling stability of Example 1 stems from its dense and ordered microstructure: the precursor prepared by the dual-complexation and segmented process forms a crack-free, low-defect layered oxide structure after calcination, effectively suppressing phase transitions, microcrack formation, and electrolyte erosion during cycling, thereby significantly improving the structural stability and cycle life of the material. In contrast, the uneven grain size of Comparative Example 1 and the loose structure of Comparative Example 2 lead to structural degradation and rapid capacity decay during cycling. The above results fully demonstrate the significant advantages of the process of this invention in improving the long-cycle performance of high-nickel cathode materials.

[0098] In summary, the high-nickel cathode material of this invention combines high specific capacity with excellent long-cycle stability, effectively solving the problems of easy structural degradation and short cycle life of high-nickel materials under traditional processes, and has significant industrial application value. Therefore, the high-nickel cathode material of this invention can be used to prepare cathode sheets, and these cathode sheets can be used to prepare and assemble solid-state lithium-ion batteries.

[0099] The foregoing description includes examples from this specification. Of course, for the purposes of describing this specification, it is impossible to describe every conceivable combination of components or methods; however, those skilled in the art will understand that many other combinations and arrangements are possible. Therefore, this specification is intended to cover all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, with regard to the use of the term "comprising" in the detailed description or claims, the term is intended to be inclusive in a manner similar to the term "including," as interpreted when "comprising" is used as a transitional word in the claims.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing high-nickel cathode material, characterized in that, Includes the following steps: According to the chemical formula Li[Ni x Co y Mn z O2, where 0.8≤x≤0.95, 0.025≤y≤0.1, 0.025≤z≤0.1, weigh out nickel salt, cobalt salt and manganese salt, add to deionized water to prepare metal salt solution; A metal salt solution and an ammonia solution were pumped together into a reaction vessel, and the reaction temperature was controlled at 45–55 °C. An alkaline solution was added to adjust the pH of the reaction system to 11.00–11.

80. The mixture was stirred and reacted continuously for 35–45 h. The resulting reaction product was filtered, washed, and vacuum dried to obtain the precursor [Ni]. x Co y Mn z (OH)2; The precursor was mixed with LiOH·H2O, ground, and then calcined to obtain a high-nickel cathode material, namely Li[Ni]. x Co y Mn z O2.

2. The preparation method according to claim 1, characterized in that, The nickel salt is NiSO4·6H2O, the cobalt salt is CoSO4·7H2O, and the manganese salt is MnSO4·H2O. The molar ratio of the nickel salt, cobalt salt, and manganese salt is 0.90:0.05:0.

05. The precursor is [Ni 0.90 Co 0.05 Mn 0.05 ](OH)2.

3. The preparation method according to claim 1, characterized in that, The concentration of the ammonia solution is 0.8–4.0 mol / L; and / or, The alkaline solution is a sodium hydroxide solution with a concentration of 4 mol / L; and / or, The precursor and LiOH·H2O are mixed in a molar ratio of TM:Li = 1:(1.02~1.05).

4. The preparation method according to claim 1, characterized in that, The calcination includes a first calcination and a second calcination, which are carried out sequentially. The first calcination is carried out at 450-500℃ for 4-6 hours, and the second calcination is carried out at 740-800℃ for 12-18 hours.

5. The preparation method according to claim 1, characterized in that, The total concentration of metal ions in the metal salt solution is 1.5–2.0 mol / L, and the metal salt solution also contains 0.05–0.1 mol / L of an auxiliary complexing agent, which is at least one of citric acid, ethylenediamine, and tartaric acid.

6. The preparation method according to claim 1, characterized in that, The reaction product is prepared as follows: During the nucleation stage, the metal salt solution and ammonia solution are pumped into the reaction vessel at a feed rate of 1.2–1.5 mL / min using a dual peristaltic pump. The pH of the reaction system is controlled at 11.70–11.80, and the stirring speed is 600–650 rpm. The nucleation stage is when the total amount of metal salt solution and ammonia solution fed is 15–25%. During the growth stage, metal salt solution and ammonia solution are pumped into the reaction vessel at a feed rate of 1.8–2.0 mL / min using a dual peristaltic pump. The pH of the reaction system is controlled at 11.40–11.50, and the stirring speed is 700–750 rpm. After the feed is completed, the mixture is stirred and reacted continuously for 35–45 h to obtain the reaction solution.

7. The preparation method according to claim 1, characterized in that, The vacuum drying is a gradient temperature vacuum drying, including: vacuum drying at 35-45℃ for 1-2 hours, then vacuum drying at 55-65℃ for 2.5-3.5 hours, and finally vacuum drying at 75-85℃ for 7-10 hours.

8. A high-nickel cathode material, characterized in that, The chemical formula of the high-nickel cathode material is Li[Ni] x Co y Mn z O2, wherein 0.8≤x≤0.95, 0.025≤y≤0.1, 0.025≤z≤0.1; the high-nickel cathode material is prepared by the preparation method described in any one of claims 1-7.

9. A positive electrode sheet, characterized in that, The raw materials for preparing the positive electrode sheet include the high-nickel positive electrode material as described in claim 8.

10. A solid-state lithium-ion battery, characterized in that, The solid-state lithium-ion battery includes the positive electrode as described in claim 9.

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