CN118738367A - A method for preparing high-nickel single crystal ternary positive electrode material - Google Patents

Abstract

The invention discloses a preparation method of a high-nickel monocrystal ternary positive electrode material. By adopting a mixed lithium source delayed lithiation technology and a temperature segmentation primary sintering technology, the processes of monocrystal fusion, particle growth, surface repair and lithium nickel rearrangement are respectively completed through sintering at different temperatures in the primary sintering process, and then the high-nickel monocrystal ternary anode material with good crystallinity and excellent electrochemical performance is prepared. Meanwhile, the method has simple process, greatly reduces the process cost and is suitable for large-scale production and application.

Description

A method for preparing high-nickel single crystal ternary positive electrode material

Technical Field

The invention belongs to the technical field of positive electrode materials, and specifically relates to a method for preparing a high-nickel single crystal ternary positive electrode material.

Background Art

With the large-scale application of lithium-ion batteries in energy storage, consumer electronics and electric vehicles, the market demand for high energy density and long cycle performance lithium-ion batteries has become more urgent. As the core component of lithium-ion batteries, positive electrode materials play a decisive role in the overall performance of the entire battery system. At present, the most common positive electrode materials in lithium-ion batteries are lithium iron phosphate and ternary materials. Among them, ternary materials have the advantages of high energy density, good low temperature performance, and strong environmental adaptability. They have become the mainstream solution for high-end consumer electronics and automotive power batteries.

In ternary materials, due to the consideration of high specific capacity and reducing the use of expensive cobalt elements, high nickel materials with a molar content of nickel greater than 80% have gradually become one of the main development directions, and their industrialization process is also accelerating. With the increase of nickel content, the degree to which lithium ions can be deintercalated in ternary materials increases, and the specific capacity is significantly improved. However, studies have found that during deep charging and discharging, the shrinkage and expansion of various anisotropic properties of crystals will also be more intense, which leads to local over-concentration of stress at the grain boundaries in traditional high-nickel polycrystalline ternary materials, which in turn causes microcracks in the particles and electrolyte penetration, ultimately leading to a significant attenuation of cycle and safety performance.

In order to solve this problem of high-nickel polycrystalline ternary materials, the industry usually adopts the method of preparing high-nickel single-crystal ternary positive electrode materials. Compared with polycrystalline materials, single-crystal materials eliminate the grain boundaries between primary particles, and thus have many advantages such as high mechanical strength, small specific surface area, and no volume phase stress concentration. However, single-crystal materials usually require higher sintering temperatures and longer sintering times to achieve fusion between primary particles. For single-crystal ternary positive electrode materials with low nickel content, due to the low content of Ni ³⁺ ions and strong structural stability, the high-temperature and long-term reaction environment has little effect on material performance. However, when the nickel content exceeds 80%, the stable temperature of the ternary material gradually becomes lower than the synthesis temperature required for single crystal fusion. The high-temperature and long-time sintering process will cause the hexagonal layered structure on the surface of the particles to decompose first, resulting in rock salt phase or spinel phase degradation. The volatilization of the lithium source causes the material to be lithium-deficient. At the same time, the cations in the bulk phase will be more easily mixed with lithium ions at high temperatures. These factors lead to a large number of defects on the surface and bulk of the material when preparing high-nickel single crystal ternary positive electrode materials using traditional high-temperature and long-time schemes, which in turn leads to the deterioration of the electrochemical performance.

In order to solve the limitations of such problems, there are currently two main methods for preparing high-nickel single crystal ternary positive electrode materials: one is to use a multi-step sintering method, such as the Chinese invention patent CN114899391A, which uses a solid-phase method of step-by-step calcination combined with a step-by-step lithium supplementation technology to synthesize ultra-high nickel single crystal ternary positive electrode materials. This method solves the surface degradation and bulk lithium-nickel mixing problems in the preparation process of high-nickel single crystal materials to a certain extent through secondary sintering and replenishing lithium sources, but the process requires multiple mixing and sintering, and the synthesis route is complex and time-consuming, which is not conducive to cost reduction; the second is to use a high-temperature molten salt method, such as the Chinese invention patent CN111200129A, which uses two or more molten inorganic salts as mixed molten salts to prepare high-nickel single crystal positive electrode materials. This method is essentially to protect the surface and bulk of the high-nickel single crystal by lowering the sintering temperature of the single crystal by molten salt. Since molten salts are generally halides or sulfates, they cause severe corrosion to equipment during the actual production process, and all of them are by-products after sintering, which are bonded together with the positive electrode material. A large amount of solvent is required for liquid phase separation and environmental protection treatment. These drawbacks increase production costs and have an adverse effect on material properties, limiting the large-scale use of molten salt sintering in industrial production.

Therefore, how to improve the sintering process of high-nickel single crystal materials so that it can maintain the advantages of single crystal materials while reducing the damage to the main body and surface of the material caused by the high-temperature and long-time sintering environment, while taking into account economic benefits, has become an important improvement direction for the preparation of high-nickel single crystal ternary positive electrode materials.

Summary of the invention

The present invention provides a method for preparing a high-nickel single crystal ternary positive electrode material. The delayed lithiation technology of a mixed lithium source and the temperature segmented one-time sintering technology are adopted to achieve the single crystal fusion, particle growth and bulk and surface defect repair respectively through segmented sintering at different temperatures in a one-time sintering process, thereby preparing a high-nickel single crystal ternary positive electrode material with good crystallinity and excellent electrochemical performance. The method introduces two lithium sources (lithium carbonate and lithium hydroxide monohydrate) with different decomposition temperatures and activities to mix with a precursor. During the high-temperature short-time sintering process of the mixed material in the first section, the lithium hydroxide monohydrate with higher activity reacts with the precursor to achieve the fusion growth of the single crystal particle morphology, while the lithium carbonate is decomposed. Then, during the low-temperature long-time sintering process of the mixed material in the second section, the lithium oxide produced after the decomposition of lithium carbonate is used to make the surface rock salt phase or spinel phase impurities react again to form layered oxides, while completing the reduction of the bulk lithium nickel mixing rate.

The method of the present invention has a simple process flow, does not require an additional sintering process, greatly reduces the material manufacturing cost, and is suitable for large-scale production applications.

In order to achieve the above technical objectives, the present invention adopts the following scheme:

The present invention provides a method for preparing a high-nickel single crystal ternary positive electrode material, comprising the following steps:

S1. mixing a high nickel ternary hydroxide precursor material with a mixed lithium source to obtain a mixture A;

S2. In the presence of a protective atmosphere, the mixed material A is sintered once, wherein the first stage sintering process is set as: sintering temperature T ₁ , sintering time t ₁ , and the second stage sintering process is set as: sintering temperature T ₂ , sintering time t ₂ ; cooling, crushing, sieving, and obtaining a high-nickel single crystal ternary positive electrode material.

Furthermore, in step S1, the chemical formula of the high nickel ternary hydroxide precursor material is Ni _x Co _y M _1-xy (OH) ₂ , wherein 0.8≤x<1, 0≤y≤0.2, and the M element is at least one of Mn and Al.

Furthermore, in the step S1, the particle size D ₅₀ of the high nickel ternary hydroxide precursor material is preferably 2 to 8 um, more preferably 3 to 5 um.

Furthermore, the mixed lithium source in step S1 is a mixture of lithium hydroxide monohydrate and lithium carbonate.

Furthermore, in step S1, the molar ratio of the high nickel ternary hydroxide precursor material, lithium hydroxide monohydrate and lithium carbonate is 1:(0.95-1.05):(0.005-0.05).

Furthermore, in step S2, the protective atmosphere is an oxygen-containing atmosphere, wherein the oxygen concentration is preferably greater than 80v%, more preferably greater than 90v%.

Furthermore, in step S2, the sintering is carried out in a tubular furnace, a muffle furnace, a box furnace, a rotary kiln, a pusher kiln or a roller kiln.

Furthermore, the first stage sintering process in step S2 includes the following steps: heating the temperature to a sintering temperature T ₁ at a heating rate of 1-5° C./min, and sintering for a time of t ₁ .

Furthermore, in the first sintering process in step S2, the sintering temperature T ₁ =[(-500x+1290)±5]° C., and the sintering time t ₁ =[(-600x+900)±30] min, wherein x is the molar fraction x of the nickel element in the chemical formula Ni _x Co _y M _1-xy (OH) ₂ of the high-nickel ternary hydroxide precursor material in step S1.

Specifically, the first stage sintering process is characterized by high temperature and short time, wherein the sintering temperature _T1 is slightly higher than the traditional single crystal sintering temperature, which can allow the precursor to react with the highly active lithium hydroxide monohydrate to quickly undergo a single crystal reaction, eliminate the grain boundaries in the bulk phase, fuse the primary particles, and complete the decomposition reaction of lithium carbonate; the shorter sintering time can minimize surface degradation and lithium-nickel mixing, and reduce the lithium deficiency of the material.

Furthermore, the second sintering process in step S2 includes the following steps: cooling the temperature from sintering temperature _T1 to _T2 at a cooling rate of 0.5-2°C/min, and sintering for a time of _t2 .

Furthermore, in the second sintering process in step S2, the sintering temperature T ₂ =[(-600x+1260)±5]°C, and the sintering time t ₂ =[(-600x+1020)±30]min, wherein x is the molar fraction x of the nickel element in the chemical formula Ni _x Co _y M _1-xy (OH) ₂ of the high-nickel ternary hydroxide precursor material in step S1.

Specifically, the second stage sintering process is characterized by low temperature and long time, wherein the sintering temperature _T2 is basically consistent with the sintering temperature of polycrystalline materials with the same nickel content. The lithium oxide produced by the decomposition of lithium carbonate can be used to make the surface rock salt phase or spinel phase impurities re-react to form layered oxides, thereby solving the lithium deficiency problem and surface defects of the material at high temperature. At the same time, suitable sintering experiments and longer calcination time can gradually rearrange the lithium ions and transition metal ions in the bulk phase, thereby reducing the bulk lithium-nickel mixing rate.

Compared with the prior art, the method for preparing the high-nickel single crystal ternary positive electrode material provided by the present invention has the following advantages:

The present invention introduces mixed lithium source and temperature segmented sintering technology, utilizes the different activities and decomposition temperatures of lithium hydroxide monohydrate and lithium carbonate, and reasonably sets the two-stage sintering temperature and time according to the nickel content of the material, and completes the single crystal growth and defect repair process respectively through one-step sintering. Among them, in the high-temperature sintering stage, lithium hydroxide monohydrate and the precursor react at a relatively high temperature to promote the fusion growth of the single crystal, and the decomposition of lithium carbonate is completed at the same time. The shorter sintering time avoids excessive lithium volatilization and surface degradation at high temperature; in the low-temperature sintering stage, the lithium source provided by the decomposition of lithium carbonate is used to repair the surface degradation caused by the high-temperature reaction. At the same time, the low-temperature and long-time sintering strategy can effectively reduce the lithium-nickel mixing rate of the bulk phase, thereby making the high-nickel single crystal ternary positive electrode material prepared by this method have good crystallinity and structural integrity, and excellent electrochemical performance.

In addition, the method of the present invention has a simple process flow, and on the basis of improving the performance of high-nickel single crystal ternary positive electrode materials, it greatly reduces the material manufacturing cost and is suitable for large-scale production applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a SEM image of a high nickel single crystal ternary cathode material prepared in Example 1;

FIG2 is an XRD spectrum of three materials obtained in Example 1, Comparative Example 1 and Comparative Example 3;

FIG3 is a SEM image of the ternary positive electrode material prepared in Comparative Example 2;

FIG4 is a SEM image of a high nickel single crystal ternary positive electrode material prepared in Comparative Example 1;

FIG5 is a SEM image of a high nickel single crystal ternary positive electrode material prepared in Comparative Example 5;

Figure 6 is a SEM image of the high-nickel single crystal ternary positive electrode material prepared in Comparative Example 7.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

The material XRD data was tested by Malvern Aeris desktop XRD tester, and the data was calculated by Highscore Plus software. The SEM results were tested by Phenom Pro desktop electron scanning microscope, and the lithium content ICP data was tested by PEAvio 500.

Embodiment 1:

The method for preparing the high nickel single crystal ternary positive electrode material in this embodiment comprises the following steps:

S1, taking 1 mol of a high nickel ternary hydroxide precursor material Ni _0.83 Co _0.13 Mn _0.04 (OH) ₂ with a D ₅₀ of 4.5 um, and mixing it with a mixed lithium source consisting of 1.04 mol of lithium hydroxide monohydrate and 0.005 mol of lithium carbonate to obtain a mixture A;

S2. The mixed material A obtained in S1 is placed in a tubular furnace, the oxygen concentration in the furnace is controlled to be 92%, and the sintering process is set as follows: heating to T ₁ = 875° C. at a heating rate of 3° C./min, sintering time t ₁ = 400 min, then cooling to T ₂ = 760° C. at a heating rate of 2° C./min, sintering time t ₂ = 520 min, and the material obtained after natural cooling is crushed and sieved to obtain a high-nickel single crystal ternary positive electrode material.

Embodiment 2:

The method for preparing the high nickel single crystal ternary positive electrode material in this embodiment comprises the following steps:

S1. Take 10 mol of a high nickel ternary hydroxide precursor material LiNi _0.9 Co _0.05 Mn _0.05 (OH) ₂ with a D ₅₀ of 4 um and mix it with a mixed lithium source consisting of 10.25 mol of lithium hydroxide monohydrate and 0.1 mol of lithium carbonate to obtain a mixture A;

S2. The mixed material A obtained in S1 is placed in a box furnace, the oxygen concentration in the furnace is controlled to be 94%, and the sintering process is set as follows: heating to T ₁ = 840° C. at a heating rate of 2.5° C./min, sintering time t ₁ = 360 min, then cooling to T ₂ = 720° C. at a heating rate of 1.5° C./min, sintering time t ₂ = 480 min, and the material obtained after natural cooling is crushed and sieved to obtain a high-nickel single crystal ternary positive electrode material.

Embodiment 3:

The method for preparing the high nickel single crystal ternary positive electrode material in this embodiment comprises the following steps:

S1. 10 mol of a high nickel ternary hydroxide precursor material LiNi _0.92 Co _0.04 Mn _0.04 (OH) ₂ with a D ₅₀ of 3.7 um is mixed with a mixed lithium source consisting of 10.1 mol of lithium hydroxide monohydrate and 0.15 mol of lithium carbonate to obtain a mixture A;

S2. The mixed material A obtained in S1 is placed in a box furnace, the oxygen concentration in the furnace is controlled to be 95%, and the sintering process is set as follows: heating to T ₁ = 825° C. at a heating rate of 2° C./min, sintering time t ₁ = 350 min, then cooling to T ₂ = 710° C. at a heating rate of 1.25° C./min, sintering time t ₂ = 465 min, and the material obtained after natural cooling is crushed and sieved to obtain a high-nickel single crystal ternary positive electrode material.

Embodiment 4:

The method for preparing the high nickel single crystal ternary positive electrode material in this embodiment comprises the following steps:

S1, taking 100 mol of a high nickel ternary hydroxide precursor material LiNi _0.95 Co _0.03 Mn _0.02 (OH) ₂ with a D ₅₀ of 3.5 um, and mixing it with a mixed lithium source consisting of 100.5 mol of lithium hydroxide monohydrate and 2 mol of lithium carbonate to obtain a mixture A;

S2. The mixed material A obtained in S1 is divided into four batches and loaded into a sagger and placed into a roller kiln. The oxygen concentration in the kiln is controlled to be 97%. The sintering process is set as follows: heating to T ₁ = 815° C. at a heating rate of 1.5° C./min, sintering time t ₁ = 330 min, then cooling to T ₂ = 690° C. at a heating rate of 0.75° C./min, sintering time t ₂ = 450 min. The material obtained after cooling is crushed and sieved to obtain a high-nickel single crystal ternary positive electrode material.

Comparative Example 1:

The method for preparing the high nickel single crystal ternary positive electrode material in this embodiment comprises the following steps:

S1, taking 1 mol of a high nickel ternary hydroxide precursor material Ni _0.83 Co _0.13 Mn _0.04 (OH) ₂ with a D ₅₀ of 4.5 um, and mixing it with a mixed lithium source consisting of 1.04 mol of lithium hydroxide monohydrate and 0.005 mol of lithium carbonate to obtain a mixture A;

S2. Put the mixed material A obtained in S1 into a tubular furnace, control the oxygen concentration in the furnace to 92%, set the sintering process as follows: increase the temperature to T = 875 ° C at a heating rate of 3 ° C / min, and sinter for t = 400 min. The material obtained after natural cooling is crushed and sieved to obtain the material of comparative example 1.

Comparative Example 2:

The method for preparing the high nickel single crystal ternary positive electrode material in this embodiment comprises the following steps:

S1, taking 1 mol of a high nickel ternary hydroxide precursor material Ni _0.83 Co _0.13 Mn _0.04 (OH) ₂ with a D ₅₀ of 4.5 um, and mixing it with a mixed lithium source consisting of 1.04 mol of lithium hydroxide monohydrate and 0.005 mol of lithium carbonate to obtain a mixture A;

S2. Put the mixed material A obtained in S1 into a tubular furnace, control the oxygen concentration in the furnace to 92%, set the sintering process as follows: increase the temperature to T = 760 ° C at a heating rate of 3 ° C / min, and sinter for t = 520 min. The material obtained after natural cooling is crushed and sieved to obtain the material of comparative example 2.

Comparative Example 3:

The method for preparing the high nickel single crystal ternary positive electrode material in this embodiment comprises the following steps:

S1. Take 1 mol of a high nickel ternary hydroxide precursor material Ni _0.83 Co _0.13 Mn _0.04 (OH) ₂ with a D ₅₀ of 4.5 um and mix it with 1.045 mol of lithium hydroxide monohydrate to obtain a mixture A;

S2. Put the mixed material A obtained in S1 into a tubular furnace, control the oxygen concentration in the furnace to 92%, set the sintering process as follows: increase the temperature to T = 850 ° C at a heating rate of 3 ° C / min, and sinter for t = 900 min. The material obtained after natural cooling is crushed and sieved to obtain the material of comparative example 3.

Comparative Example 4:

The difference between this comparative example and Example 1 is that the lithium source in step S1 is 1.05 mol of lithium hydroxide monohydrate.

Comparative Example 5:

The difference between this comparative example and Example 1 is that the lithium source in step S1 is 0.525 mol of lithium carbonate.

Comparative Example 6:

The difference between this comparative example and Example 1 is that the sintering time _t1 in step S2 is 500 min.

Comparative Example 7:

The difference between this comparative example and Example 1 is that the sintering time _t1 in step S2 is 300 min.

It can be seen from Figure 1 that the single crystal grows well and the particles are distinct, which is basically consistent with the single crystal material obtained by the traditional sintering scheme in Comparative Example 3 (Figure 4), indicating that the method provided by the present invention can obtain a high-nickel single crystal ternary positive electrode material with good morphology.

From Figure 2, it can be seen that the materials obtained in Comparative Examples 1 and 3 have obvious rock salt phase impurity peaks. Among them: the comparison of the results of Example 1 and Comparative Example 1 shows that the second stage of low-temperature long-time sintering adopted by the present invention can effectively restore the surface degradation and structural defects caused by the first stage of high-temperature short-time sintering, proving the rationality of the process; the comparison of the results of Example 1 and Comparative Example 3 shows that compared with the single crystal material obtained by the traditional sintering of Comparative Example 3, the method provided by the present invention can obtain a high-nickel single crystal ternary positive electrode material with better crystallinity and fewer defects.

It can be seen from Figure 3 that no single crystal is generated, but a polycrystalline secondary spherical particle morphology. Compared with Example 1 (Figure 1), it shows that the first stage of high-temperature short-time sintering of the present invention is mainly for the generation of single crystal particle morphology, and the second stage of low-temperature long-time sintering is mainly for repairing structural defects. The organic combination of the two-stage sintering process can obtain a high-nickel single crystal ternary positive electrode material with good morphology.

Table 1 is a performance comparison of the ternary positive electrode materials prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention. From the physicochemical indicators, it can be seen that the material obtained by the method provided by the present invention has a higher I ₍₀₀₃₎ /I ₍₁₀₄₎ value and a lower lithium-nickel mixing rate, which is basically consistent with the polycrystalline material of Comparative Example 2, indicating that it has better crystallinity and the structural integrity can reach the level of polycrystalline materials. From the thermal safety and electrochemical performance, it can be seen that the high-nickel single crystal positive electrode material obtained by the method provided by the present invention has obvious advantages in the first-week discharge capacity and first effect while maintaining a higher DSC exothermic temperature and more stable long-cycle performance.

Table 2 is a comparison of the physicochemical indicators of the ternary positive electrode materials prepared in Example 1, Comparative Example 4 and Comparative Example 5 of the present invention. It can be seen that the I ₍₀₀₃₎ / I ₍₁₀₄₎ value of the material obtained in Comparative Example 4, which only uses lithium hydroxide monohydrate as the lithium source, is low, the lithium-nickel mixing rate is high, and the lithium content in the material is less than 1. This is because the lithium hydroxide monohydrate is highly active, the high temperature section is fully involved in the reaction, and it is easy to volatilize. However, the material will undergo surface degradation and structural defects in the high temperature section, resulting in the lack of active lithium. There is no additional lithium source in the low temperature section for lithium supplementation reaction, which then causes the material to lack lithium and have poor crystallinity. In addition, the lithium content of the material obtained by the comparative example 5 using only lithium carbonate as the lithium source is obviously high. It can be seen from Figure 5 that due to the high decomposition temperature of lithium carbonate, the activity is low, the single crystal size of the material is small, and the dispersibility is poor at the same time, and there is obvious lithium carbonate on the surface that does not participate in the reaction, and the "concave-convex" morphology caused by the residue, the reason for its high lithium content is mainly that the surface residual lithium is more, and it does not enter the interior of the lattice, so it is still poor in crystallinity, such as I ₍₀₀₃₎ / I ₍₁₀₄₎ value is low, and the lithium nickel mixed row rate is high. These two comparative examples prove that only by using mixed lithium sources with different activities and reasonably controlling the use ratio, the technical effect of the present invention can be achieved.

Table 3 is a comparison of the physicochemical indicators of the ternary positive electrode materials prepared in Example 1, Comparative Example 6 and Comparative Example 7 of the present invention. It can be seen that when the sintering time of the high temperature section in Comparative Example 6 is too long, the crystallinity of the material decreases. When the sintering time of the high temperature section in Comparative Example 7 is too short, the crystallinity of the material remains basically unchanged. However, it can be seen from the SEM image of Figure 6 that the single crystal particle size of the material is obviously small and the dispersibility is poor. These two comparative examples prove that only by adopting the reasonable sintering parameters provided by the present invention can the technical effect be achieved.

Table 1 Comparison of performance of ternary positive electrode materials in Example 1 Comparative Examples 1-3

Table 2 Comparison of physical and chemical indicators of ternary positive electrode materials in Example 1, Comparative Examples 4-5

Test items I ₍₀₀₃₎ /I ₍₁₀₄₎ Li-Ni mixing rate (%) Li _(ICP) content (mol%) Example 1 1.490 1.996 1.011 Comparative Example 4 1.446 2.024 0.962 Comparative Example 5 1.423 2.112 1.038

Table 3 Comparison of physicochemical indicators of ternary positive electrode materials in Example 1, Comparative Examples 6-7

Test items I ₍₀₀₃₎ /I ₍₁₀₄₎ Li-Ni mixing rate (%) Example 1 1.490 1.996 Comparative Example 6 1.467 2.011 Comparative Example 7 1.488 1.995

Claims (10)

1. A preparation method of a high-nickel monocrystal ternary positive electrode material comprises the following steps:

s1, mixing a high-nickel ternary hydroxide precursor material with a mixed lithium source to obtain a mixture A;

S2, sintering the mixture A for the first time in the presence of protective atmosphere, wherein the first-stage sintering process is set as follows: sintering temperature T ₁, sintering time T ₁, setting the second stage sintering process as follows: sintering temperature T ₂ and sintering time T ₂; cooling, crushing and sieving to obtain the high-nickel monocrystal ternary anode material.

2. The method of claim 1, wherein the chemical formula of the high nickel ternary hydroxide precursor material in step S1 is Ni _xCo_yM_1-x-y(OH)₂, wherein x is 0.8-1, y is 0-0.2, and m is at least one of Mn or Al.

3. The method according to claim 1 or 2, wherein the particle size D ₅₀ of the high nickel ternary hydroxide precursor material in step S1 is preferably 2-8 um, more preferably 3-5 um.

4. A method according to any one of claims 1 to 3, wherein the mixed lithium source in step S1 is a mixture of lithium hydroxide monohydrate and lithium carbonate.

5. The method according to any one of claims 1 to 4, wherein the molar ratio of the high nickel ternary hydroxide precursor material, lithium hydroxide monohydrate, and lithium carbonate in step S1 is 1 (0.95-1.05): 0.005-0.05.

6. The method according to any one of claims 1 to 5, wherein in the first stage sintering process in step S2, the sintering temperature T ₁ = [ (-500x+1290) ± 5] c and the sintering time T ₁ = [ (-600x+900) ± 30] min, wherein x is the molar component x of the nickel element in the chemical formula Ni _xCo_yM_1-x-y(OH)₂ of the high nickel ternary hydroxide precursor material in step S1.

7. The method according to any one of claims 1 to 6, wherein in the second stage sintering process in step S2, the sintering temperature T ₂ = [ (-600x+1260) ±5] c and the sintering time T ₂ = [ (-600x+1020) ±30] min, wherein x is the molar component x of the nickel element in the high nickel ternary hydroxide precursor material formula Ni _xCo_yM_1-x-y(OH)₂ in step S1.

8. The method according to any one of claims 1 to 7, wherein the protective atmosphere in step S2 is an oxygen-containing atmosphere, wherein the oxygen concentration is preferably greater than 80v%, more preferably greater than 90v%.

9. The method according to any one of claims 1 to 8, wherein the sintering temperature T ₁ is raised at a rate of 1 to 5 ℃/min in the first stage sintering process in step S2.

10. The method according to any one of claims 1 to 9, wherein in the second stage sintering process in step S2, the sintering temperature is reduced from T ₁ to T ₂ at a cooling rate of 0.5 to 2 ℃/min.