A method for producing a high-density layered metal lithium compound

Abstract

This invention provides a method for preparing a high-pressure, layered lithium metallic compound, belonging to the technical field of lithium-ion secondary battery materials. The high-pressure, layered lithium metallic compound obtained by this invention has the expression F1. x F2 y The particle size distribution exhibits a bimodal pattern, with F1 corresponding to the small particle size peak and F2 corresponding to the large particle size peak. First, precursors P1 and P2 for F1 and F2 were prepared via a batch method, with a particle size distribution of 0.1 ≤ (D90-D10) / D50 ≤ 0.8 and D100 ≤ 0.50. P1 ≤D0 P2 Then, P1 and P2 were pretreated to prepare intermediates M1 and M2, 1m 2 / g≤SSA≤5m 2 / g and 0.8≤SSA M1 / SSA M2 ≤1.2; Finally, M1, M2 and the N-containing compound are mixed and simultaneously doped and sintered under the same sintering regime. This preparation method is simple, low-cost, and has a large production capacity, making it suitable for large-scale industrial production. The prepared high-compact layered lithium metal compounds have good uniformity, low residual alkali, and advantages such as high compaction, high energy density, and long cycle life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion secondary battery materials technology, specifically to a method for preparing a high-pressure, layered metallic lithium compound. Background Technology

[0002] In terms of lithium battery applications in my country, the rapid development of industries such as power, energy storage, and 3C (computers, communications, and consumer electronics) has become the main driving force for the development of the lithium-ion battery industry, and the demand for lithium batteries in the power and energy storage sectors is accelerating. As the driving range requirements of pure electric vehicles continue to increase, power battery manufacturers are increasingly demanding higher energy density from lithium batteries.

[0003] Increasing the relative nickel content in materials to improve compaction density is key to increasing battery energy density. However, higher nickel content leads to poorer cycle stability, and single-component materials do not possess high compaction advantages. Therefore, simply pursuing higher nickel content is not the preferred solution for high-energy-density battery materials.

[0004] As a solution to the above problem, a technology has been proposed to use two or more high-nickel matrix materials with different median particle sizes (D50) as cathode materials. Currently, this is achieved through two methods: finished product mixing or precursor mixing and sintering. The former requires the separate preparation of high-nickel matrix materials with different median particle sizes (D50), which is complex and costly. The latter simplifies the preparation method, but the sintering process cannot adequately accommodate different high-nickel substrates, resulting in poor material uniformity and limiting performance.

[0005] To overcome the problems existing in the prior art, the inventors, through continuous experimental research, discovered that only when the D50 of the two high-nickel substrates and Ni... 2+ The ratio of the product of the total Ni content must meet certain conditions to achieve the optimal sintering regime for both substrates. Furthermore, it was found that by controlling the specific surface area, structural characteristics, and lithium hydroxide content of the intermediate, the material uniformity can be improved, and the production capacity can be further increased to obtain high-performance high-density lithium metal compounds, thus completing this invention. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing high-compact layered lithium metal compounds. This method is simple, low-cost, and produces high-compact layered lithium metal compounds with good uniformity and excellent performance.

[0007] To achieve the above objectives, the present invention provides a method for preparing high-density layered lithium metal compounds, employing the following technical solution:

[0008] A method for preparing a high-compaction layered lithium metal compound, wherein the high-compaction layered lithium metal compound comprises layered lithium metal compound F1 and layered lithium metal compound F2, and the molecular formula of the high-compaction layered lithium metal compound is F1. x F2 y Where x + y = 1; the general formula for the layered lithium metal compound F1 and layered lithium metal compound F2 is Li(Ni 2+ m1 Ni 3+ n1 ) a M b N c O2, where m1+n1=1, Ni in layered lithium metal compounds F1 and F2 2+ The proportion of Ni in the total Ni satisfies condition 1 < m1 F1 / m1 F2 ≤2, 0.04≤m1 F1 / n1 F1 ≤2 and 0.02≤m1 F2 / n1 F2 ≤1;

[0009] Includes the following steps:

[0010] Step 1: Screen precursors P1 and P2, ensuring particle size meets the conditions 0.1 ≤ (D90 - D10) / D50 ≤ 0.8 and D100. P1 ≤D0 P2 and 1≤(D50) P2 *m1 F2 ) / (D50 P1 *m1 F1 )≤4;

[0011] Step 2: Pretreatment of precursors P1 and P2 to prepare intermediates M1 and M2, with a specific surface area meeting the condition of 1m². 2 / g≤SSA≤5m 2 / g and 0.8≤SSA M1 / SSA M2 ≤1.2; Characteristic peaks appear in the XRD patterns near 2θ = 18.6°, 36.5°, 38.0°, 44.3°, and 64.5°, respectively. The characteristic peaks near 38.0° and 64.5° are single peaks. The interplanar spacings d corresponding to the five characteristic peaks are respectively... and The ratio of the peak intensity of the first characteristic peak to the fourth characteristic peak, I1 / I4, is 0.5-1.5, and the ratio of the peak intensity of the second characteristic peak to the third characteristic peak, I2 / I3, is 0.5-1.5.

[0012] Step 3: Mix intermediate M1, intermediate M2 and N-containing compound, and perform doping sintering, pulverize, to obtain a high-density layered lithium metal compound with a bimodal particle size distribution.

[0013] Furthermore, the M and N elements are both at least one of the elements Co, Mn, B, F, Mg, S, K, Na, Al, Ti, Cr, Ga, Zr, Nb, Mo, Ru, Sn, and W, wherein the M element contains at least one element with a valence greater than 3.

[0014] Furthermore, 0.6 < a ≤ 1, 0 < b ≤ 0.4, 0 ≤ c ≤ 0.05, and a + b = 1.

[0015] Furthermore, in step 1, the precursors P1 and P2 are prepared by co-precipitation reaction of Ni salt and M compound in a mixed salt solution, wherein the Ni salt is at least one of nickel sulfate, nickel chloride, nickel nitrate, nickel oxalate, and nickel acetate, and the M compound is at least one of sulfate, nitrate, oxalate, or sodium M compound containing the M element.

[0016] Furthermore, in step 2, the preprocessing method is as follows:

[0017] The precursors P1 and P2 were respectively mixed with lithium salt and sintered under negative pressure in an atmosphere with an oxygen concentration greater than 20%.

[0018] Alternatively, the precursors P1 and P2 and the lithium salt are mixed and sintered under negative pressure in an atmosphere with an oxygen concentration greater than 20%.

[0019] As can be seen from the above technical solutions, intermediates M1 and M2 can be prepared by either mixing precursors P1 and P2 with lithium salt separately and then sintering under negative pressure, or by mixing precursors P1, P2 and lithium salt together and then sintering under negative pressure.

[0020] Furthermore, in step 2, the lithium hydroxide content of intermediates M1 and M2 is 5000-100000ppm.

[0021] Furthermore, in step 2, the molar ratio of precursor P1 and precursor P2 to lithium salt is 1.02 to 1.10, and the lithium salt particle size is 100-2000 μm.

[0022] Furthermore, in step 2, the negative pressure is (-1) Pa to (-20) Pa, the sintering temperature is 300-700℃, and the sintering time is 2-8 h.

[0023] Furthermore, in step 3, the sintering temperature is 600-1000℃ and the sintering time is 6-30h.

[0024] The above-described technical solution of the present invention has at least the following beneficial effects:

[0025] 1. The present invention provides a method for preparing a high-compaction layered lithium metal compound. Starting from product design, by selecting a suitable precursor and precisely controlling the physical properties of the intermediate, a layered lithium metal compound with good uniformity, high compaction, high energy density and long cycle life is prepared.

[0026] 2. This invention is quantifiable. By limiting the quantitative relationship between the precursors and intermediates of different particle sizes, the optimal sintering process can simultaneously satisfy the requirements of two substrates.

[0027] 3. This invention obtains a layered structure framework by pre-treating the precursor, and then further refines and perfects the structure by doping and sintering. This avoids the phenomenon that the crystal structure of the material obtained by direct sintering is not perfect due to the higher the nickel content and the more intense the high-temperature solid-state reaction.

[0028] 4. For precursors with significant differences, this invention proposes a method to pretreat the two precursors separately and then dope and sinter them together. This method not only meets the different requirements of different precursor compositions for the ideal lithium ratio and pretreatment regime, but also ensures that the prepared material has good uniformity. The preparation method is simple.

[0029] 5. The pretreatment process of this invention uses coarse-particle lithium salt as the lithium source and air as the pretreatment atmosphere, which reduces production costs. At the same time, the negative pressure sintering method used in the pretreatment process effectively solves the problem of high residual alkali in high-nickel materials, and breaks through the limitation of the amount of high-nickel materials in the pot, thereby increasing production capacity. Attached Figure Description

[0030] Figure 1 SEM image of the positive electrode material prepared in Example 1 of this invention;

[0031] Figure 2 SEM image of the cathode material prepared in Comparative Example 1 of this invention;

[0032] Figure 3 The results show the comparison of the capacity performance of the cathode materials in Examples 1-2 and Comparative Examples 1-2 of this invention;

[0033] Figure 4 The results show the comparison of the cycle performance of the cathode materials in Examples 1-2 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be described in conjunction with the accompanying drawings of the embodiments of the present invention. Figure 1-4The technical solutions of the embodiments of the present invention will be clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0035] Example 1

[0036] This embodiment of a high-density layered lithium metal compound includes a layered lithium metal compound Li(Ni). 2+ 0.145 Ni 3 + 0.855 ) 0.83 Co 0.11 Mn 0.06 Al 0.02 O2 and layered lithium metal compounds Li(Ni) 2+ 0.111 Ni 3+ 0.889 ) 0.90 Co 0.06 Mn 0.04 Al 0.02 O2, the specific preparation method is as follows:

[0037] (1) Select a precursor P1 with a suitable particle size: Ni 0.83 Co 0.11 Mn 0.06 (OH)2 and precursor P2: Ni 0.90 Co 0.06 Mn 0.04 (OH)2; In this invention, D0, D10, D50, D90, and D100 are particle size results measured using a Mastersizer 3000 with a light-blocking degree of 9–11%, representing the particle size corresponding to when the particle size distribution number reaches 0%, 10%, 50%, 90%, and 100%, respectively. The precursor particle sizes selected for the embodiments and comparative examples in this invention are shown in Table 1.

[0038] (2) Pretreatment of precursors P1 and P2 was performed to prepare intermediates M1 and M2. The specific operations are as follows:

[0039] Preparation of intermediate M1: Ni 0.83 Co 0.11 Mn 0.06 (OH)₂ was mixed with coarse-grained lithium salt at a molar ratio of 1.045, and then sintered at 600°C for 6 hours under an atmosphere of 21% oxygen concentration, with the negative pressure controlled at -8 Pa. The resulting material had an SSA of 2.95 m. 2 / g; The XRD pattern showed 5 characteristic peaks, corresponding to interplanar spacings d as follows: The peak intensity ratio of the first characteristic peak to the fourth characteristic peak, I1 / I4, is 1.08, and the peak intensity ratio of the second characteristic peak to the third characteristic peak, I2 / I3, is 1.25; the lithium hydroxide content is 33000 ppm.

[0040] Preparation of intermediate M2: Ni 0.90 Co 0.06 Mn 0.04 (OH)₂ was mixed with coarse-grained lithium salt at a molar ratio of 1.04, and then sintered at 580°C for 5 hours under an atmosphere of 21% oxygen concentration, with the negative pressure controlled at -5 Pa. The resulting material had an SSA of 3.70 m. 2 / g; The XRD pattern showed 5 characteristic peaks, corresponding to interplanar spacings d as follows: The peak intensity ratio of the first characteristic peak to the fourth characteristic peak, I1 / I4, is 0.93, and the peak intensity ratio of the second characteristic peak to the third characteristic peak, I2 / I3, is 0.82; the lithium hydroxide content is 42000 ppm.

[0041] (3) Mix intermediates M1 and M2 obtained in the above steps in proportion, and add Al2O3 powder at a molar ratio of Al to precursor of 0.02:1. Mix at 300 rpm for 3 min in a high-speed mixer, and then mix at 600 rpm for 10 min to ensure that the material is fully mixed and uniform. Sinter the mixture at 780℃ for 10 h. Crush the sintered material to obtain a layered lithium metal compound with a bimodal particle size distribution.

[0042] The compaction density of the high-compact layered lithium metal compound prepared in Example 1 was 3.85 g / cm³. 3 The lithium hydroxide has a concentration of 4100 ppm, a discharge specific capacity of 216.2 mAh / g at 0.2C, and retains 94.5% of its capacity after 50 cycles.

[0043] Example 2

[0044] This embodiment of a high-density layered lithium metal compound includes a layered lithium metal compound Li(Ni). 2+ 0.071 Ni 3 + 0.929 ) 0.90 Co 0.06 Mn 0.04 Zr 0.006 O2 and layered lithium metal compounds Li(Ni) 2+ 0.046 Ni 3+ 0.954 ) 0.96 Co 0.02 Mn 0.02 Zr0.006 O2, the specific preparation method is as follows:

[0045] (1) Select a precursor P1 with a suitable particle size: Ni 0.90 Co 0.06 Mn 0.04 (OH)2 and precursor P2: Ni 0.96 Co 0.02 Mn 0.02 (OH)2;

[0046] (2) Pretreatment of precursors P1 and P2 was performed to prepare intermediates M1 and M2. The specific operations are as follows:

[0047] Preparation of intermediate M1: Ni 0.90 Co 0.06 Mn 0.04 (OH)₂ was mixed with coarse-grained lithium salt at a molar ratio of 1.035, and then sintered at 580°C for 5 hours under an atmosphere of 21% oxygen concentration, with the negative pressure controlled at -7 Pa. The resulting material had an SSA of 3.80 m. 2 / g; The XRD pattern showed 5 characteristic peaks, corresponding to interplanar spacings d as follows: The peak intensity ratio of the first characteristic peak to the fourth characteristic peak (I1 / I4) is 0.95, and the peak intensity ratio of the second characteristic peak to the third characteristic peak (I2 / I3) is 0.90; the lithium hydroxide content is 41000 ppm.

[0048] Preparation of intermediate M2: Ni 0.96 Co 0.02 Mn 0.02 (OH)₂ was mixed with coarse-grained lithium salt at a molar ratio of 1.04, and then sintered at 550°C for 5 hours under an atmosphere of 21% oxygen concentration, with the negative pressure controlled at -7 Pa. The resulting material had an SSA of 4.70 m. 2 / g; The XRD pattern showed 5 characteristic peaks, corresponding to interplanar spacings d as follows: The peak intensity ratio of the first characteristic peak to the fourth characteristic peak, I1 / I4, is 0.63, and the peak intensity ratio of the second characteristic peak to the third characteristic peak, I2 / I3, is 0.69; the lithium hydroxide content is 46000 ppm.

[0049] (3) Mix intermediates M1 and M2 obtained in the above steps in proportion, and add ZrO2 powder at a molar ratio of Zr to precursor of 0.006:1. Mix at 300 rpm for 3 min in a high-speed mixer, and then mix at 600 rpm for 10 min to ensure that the material is fully mixed and uniform. Sinter the mixture at 730℃ for 10 h. Crush the sintered material to obtain a layered lithium metal compound with a bimodal particle size distribution.

[0050] The compaction density of the high-compact layered lithium metal compound prepared in Example 2 was 3.87 g / cm³. 3 The lithium hydroxide has a concentration of 4500ppm, a discharge specific capacity of 220.5mAh / g at 0.2C, and retains a capacity of 92.8% after 50 cycles.

[0051] Comparative Example 1

[0052] This comparative example includes a high-density layered lithium metal compound comprising a layered lithium metal compound Li(Ni). 2+ 0.145 Ni 3 + 0.855 ) 0.83 Co 0.11 Mn 0.06 Al 0.02 O2 and layered lithium metal compounds Li(Ni) 2+ 0.111 Ni 3+ 0.889 ) 0.90 Co 0.06 Mn 0.04 Al 0.02 O2, the specific preparation method is as follows:

[0053] (1) Select a precursor P1 with a suitable particle size: Ni 0.83 Co 0.11 Mn 0.06 (OH)2 and precursor P2: Ni 0.90 Co 0.06 Mn 0.04 (OH)2;

[0054] (2) Pretreatment of precursors P1 and P2 was performed to prepare intermediates M1 and M2. The specific operations are as follows:

[0055] Preparation of intermediate M1: Ni 0.83 Co 0.11 Mn 0.06 (OH)₂ was mixed with coarse-grained lithium salt at a molar ratio of 1.045, and then sintered at 600°C for 5 hours under an atmosphere of 21% oxygen concentration. The resulting material had an SSA of 3.55 μm. 2 / g; The XRD pattern showed 5 characteristic peaks, corresponding to interplanar spacings d as follows: The peak intensity ratio of the first characteristic peak to the fourth characteristic peak (I1 / I4) is 0.73, and the peak intensity ratio of the second characteristic peak to the third characteristic peak (I2 / I3) is 0.68; the lithium hydroxide content is 61000 ppm.

[0056] Preparation of intermediate M2: Ni 0.90 Co 0.06 Mn 0.04 (OH)₂ was mixed with coarse-grained lithium salt at a molar ratio of 1.04, and then sintered at 550°C for 5 hours under an oxygen concentration of 21%. The resulting material had an SSA content of 5.90 μm. 2 / g; The XRD pattern showed 5 characteristic peaks, corresponding to interplanar spacings d as follows: The peak intensity ratio of the first characteristic peak to the fourth characteristic peak, I1 / I4, is 0.43, and the peak intensity ratio of the second characteristic peak to the third characteristic peak, I2 / I3, is 0.62; the lithium hydroxide content is 113,000 ppm.

[0057] (3) Mix intermediates M1 and M2 obtained in the above steps in proportion, and add Al2O3 powder at a molar ratio of Al to precursor of 0.02:1. Mix at 300 rpm for 3 min in a high-speed mixer, and then mix at 600 rpm for 10 min to ensure that the material is fully mixed and uniform. Sinter the mixture at 780℃ for 10 h. Crush the sintered material to obtain a layered lithium metal compound with a bimodal particle size distribution.

[0058] The compaction density of the high-compact layered lithium metallic compound prepared in Comparative Example 1 was 3.74 g / cm³. 3 The lithium hydroxide has a concentration of 7700ppm, a discharge specific capacity of 210.1mAh / g at 0.2C, and retains 90.1% of its capacity after 50 cycles.

[0059] Comparative Example 2

[0060] This comparative example includes a high-density layered lithium metal compound comprising a layered lithium metal compound Li(Ni). 2+ 0.071 Ni 3 + 0.929 ) 0.90 Co 0.06 Mn 0.04 Zr 0.006 O2 and layered lithium metal compounds Li(Ni) 2+ 0.046 Ni 3+ 0.954 ) 0.96 Co 0.02 Mn 0.02 Zr 0.006 O2, the specific preparation method is as follows:

[0061] (1) Select a precursor P1 with a suitable particle size: Ni 0.90 Co 0.06 Mn0.04 (OH)2 and precursor P2: Ni 0.96 Co 0.02 Mn 0.02 (OH)2;

[0062] (2) Pretreatment of precursors P1 and P2 was performed to prepare intermediates M1 and M2. The specific operations are as follows:

[0063] Preparation of intermediate M1: Ni 0.90 Co 0.06 Mn 0.04 (OH)₂ was mixed with coarse-grained lithium salt at a molar ratio of 1.035, and then sintered at 550°C for 5 hours under an atmosphere of 21% oxygen concentration. The resulting material had an SSA content of 4.20 m. 2 / g; The XRD pattern showed 5 characteristic peaks, corresponding to interplanar spacings d as follows: The peak intensity ratio of the first characteristic peak to the fourth characteristic peak, I1 / I4, is 1.08, and the peak intensity ratio of the second characteristic peak to the third characteristic peak, I2 / I3, is 0.97; the lithium hydroxide content is 106000 ppm.

[0064] Preparation of intermediate M2: Ni 0.96 Co 0.02 Mn 0.02 (OH)₂ was mixed with coarse-grained lithium salt at a molar ratio of 1.04, and then sintered at 560°C for 5 hours under an oxygen concentration of 21%. The resulting material had an SSA of 6.30 μm. 2 / g; The XRD pattern showed 5 characteristic peaks, corresponding to interplanar spacings d as follows: The peak intensity ratio of the first characteristic peak to the fourth characteristic peak, I1 / I4, is 0.86, and the peak intensity ratio of the second characteristic peak to the third characteristic peak, I2 / I3, is 0.75; the lithium hydroxide content is 125,000 ppm.

[0065] (3) Intermediate M1 and intermediate M2 obtained in the above steps were mixed in proportion, and ZrO2 powder was added at a Zr to precursor molar ratio of 0.006:1. The mixture was first mixed at 300 rpm for 3 min in a high-speed mixer, and then at 600 rpm for 10 min to ensure thorough and uniform mixing. The mixture was then sintered at 730℃ for 10 h. The sintered material was then pulverized to obtain a layered lithium metal compound with a bimodal particle size distribution. The compaction density of the high-compact layered lithium metal compound prepared in Comparative Example 2 was 3.57 g / cm³. 3 The lithium hydroxide has a concentration of 8500ppm, a discharge specific capacity of 213.5mAh / g at 0.2C, and retains 88.8% of its capacity after 50 cycles.

[0066] Table 1. Precursor particle size used in Examples 1-2 and Comparative Examples 1-2 / unit, μm

[0067]

[0068] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-density layered lithium metal compound, characterized in that, The high-pressure, layered lithium metal compound includes layered lithium metal compound F1 and layered lithium metal compound F2, and the molecular formula of the high-pressure, layered lithium metal compound is F1. x F2 y Where x + y = 1; the general formula for the layered lithium metal compound F1 and layered lithium metal compound F2 is Li(Ni 2+ m1 Ni 3+ n1 ) a M b N c O2, where m1+n1=1, Ni in layered lithium metal compounds F1 and F2 2+ The proportion of Ni in the total Ni satisfies condition 1 < m1 F1 / m1 F2 ≤2, 0.04≤m1 F1 / n1 F1 ≤2 and 0.02≤m1 F2 / n1 F2 ≤1; Includes the following steps: Step 1: Screen precursors P1 and P2, ensuring particle size meets the conditions 0.1 ≤ (D90 - D10) / D50 ≤ 0.8 and D100. P1 ≤D0 P2 and 1≤(D50) P2 *m1 F2 ) / (D50 P1 *m1 F1 )≤4; Step 2: Pretreatment of precursors P1 and P2 to prepare intermediates M1 and M2, with a specific surface area meeting the condition of 1m². 2 / g≤SSA≤5m 2 / g and 0.8≤SSA M1 / SSA M2 ≤1.2; Characteristic peaks appear in the XRD patterns near 2θ = 18.6°, 36.5°, 38.0°, 44.3°, and 64.5°, respectively. The characteristic peaks near 38.0° and 64.5° are single peaks. The interplanar spacings d corresponding to the five characteristic peaks are respectively... and The ratio of the peak intensity of the first characteristic peak to the fourth characteristic peak, I1 / I4, is 0.5-1.5, and the ratio of the peak intensity of the second characteristic peak to the third characteristic peak, I2 / I3, is 0.5-1.

5. Step 3: Mix intermediate M1, intermediate M2 and N-containing compound, and perform doping sintering, pulverize, to obtain a high-density layered lithium metal compound with a bimodal particle size distribution.

2. The method for preparing high-compact layered lithium metal compounds according to claim 1, characterized in that, The elements M and N are both at least one of the elements Co, Mn, B, F, Mg, S, K, Na, Al, Ti, Cr, Ga, Zr, Nb, Mo, Ru, Sn, and W, wherein element M contains at least one element with a valence greater than 3.

3. The method for preparing high-density layered lithium metal compound according to claim 1, characterized in that, 0.6 < a ≤ 1, 0 < b ≤ 0.4, 0 ≤ c ≤ 0.05 and a + b = 1.

4. The method for preparing high-compact layered lithium metal compound according to claim 1, characterized in that, In step 1, the precursors P1 and P2 are prepared by co-precipitation reaction of Ni salt and M compound in a mixed salt solution. The Ni salt is at least one of nickel sulfate, nickel chloride, nickel nitrate, nickel oxalate, and nickel acetate, and the M compound is at least one of sulfate, nitrate, oxalate, or sodium M compound containing the element M.

5. The method for preparing high-compact layered lithium metal compound according to claim 1, characterized in that, In step 2, the preprocessing method is as follows: The precursors P1 and P2 were respectively mixed with lithium salt and sintered under negative pressure in an atmosphere with an oxygen concentration greater than 20%. Alternatively, the precursors P1 and P2 and the lithium salt are mixed and sintered under negative pressure in an atmosphere with an oxygen concentration greater than 20%.

6. The method for preparing high-density layered lithium metal compound according to claim 5, characterized in that, In step 2, the lithium hydroxide content of intermediates M1 and M2 is 5000-100000ppm.

7. The method for preparing high-compact layered lithium metal compound according to claim 5, characterized in that, In step 2, the molar ratio of precursor P1 and precursor P2 to lithium salt is 1.02 to 1.10, and the lithium salt particle size is 100-2000 μm.

8. The method for preparing high-density layered lithium metal compound according to claim 5, characterized in that, In step 2, the negative pressure is (-1) Pa to (-20) Pa, the sintering temperature is 300-700℃, and the sintering time is 2-8 h.

9. The method for preparing high-density layered lithium metal compound according to claim 1, characterized in that, In step 3, the sintering temperature is 600-1000℃ and the sintering time is 6-30h.

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