A cathode lithium supplement and its precursor, preparation method and application

Abstract

The present disclosure relates to a cathode lithium supplement agent, its precursor, preparation method and application, belonging to the technical field of lithium supplement agents. The precursor of the cathode lithium supplement agent includes a core material and a shell material coated on the surface of the core material; the core material is a porous spherical material composed of nanosheets, and the core material contains Ni(OH)2; the shell material contains at least one of an oxide of element M and a hydroxide of element M, and M includes at least one of Mn, Co, Cu, Mg, Ca, Fe, Sr, Al and Ti. The shell material of the precursor adsorbs on the core material, can react with a lithium source at a low temperature to generate a lithium-containing metal oxide to wrap on the surface of the core material, and promotes the reaction of the lithium source with Ni(OH)2 to form a good solid solution, thereby playing a role in reducing the sintering temperature and being beneficial to obtaining a high-purity lithium supplement agent material. The cathode lithium supplement agent prepared from this precursor has low hygroscopicity and high stability.

Description

Technical Field

[0001] The present disclosure relates to the technical field of lithium supplement agents, and more particularly, to a cathode lithium supplement agent, its precursor, preparation method and application. Background Art

[0002] Currently, new energy vehicles have increasingly higher requirements for the cruising range of power batteries, which puts forward higher requirements for the cycle capacity of power battery materials. During the charge and discharge process of lithium-ion batteries, a CEI film (surface electrolyte interface film) will be formed on the surface of the cathode material and an SEI film (solid electrolyte interface film) will be formed on the surface of the anode material. These two processes will cause the consumption of active lithium in the original material, and this consumption is irreversible, which will reduce the charge and discharge efficiency of the battery and cause a loss of battery capacity.

[0003] Cathode lithium supplement agents such as lithium-rich nickel oxides are relatively safe and reliable, with relatively low costs. They can release a large amount of lithium ions during the first charge, and the products after releasing lithium ions have extremely low activity and will not undergo re-insertion or dissolution of lithium, which can significantly improve the cycle efficiency and energy density of lithium-ion batteries. However, in the current preparation process of cathode lithium supplement agents, the precursor and lithium source need to be subjected to high-temperature and long-time solid-phase sintering, the conditions are relatively strict, and the corresponding cathode lithium supplement agent has poor stability. After being prepared into a battery, the performance of the battery such as charging capacity and initial charging efficiency is poor.

[0004] In view of this, the present disclosure is particularly proposed. Summary of the Invention

[0005] The purpose of the present disclosure includes providing a cathode lithium supplement agent, its precursor, preparation method and application to solve or improve at least one of the above technical problems.

[0006] The present disclosure can be realized as follows:

[0007] In a first aspect, the present disclosure provides a precursor of a cathode lithium supplement agent, which includes a core material and a shell material coated on the surface of the core material; wherein, the core material is a porous spherical material composed of nanosheets, and the core material contains Ni(OH)₂; the shell material contains at least one of an oxide of element M and a hydroxide of element M, and element M includes at least one of Mn, Co, Cu, Mg, Ca, Fe, Sr, Al and Ti.

[0008] In an optional embodiment, the core material has at least one of the following characteristics:

[0009] Characteristic One: The D of the core material 50 is 1 μm - 3 μm;

[0010] Characteristic Two: The specific surface area of the core material is 40 m 2 / g-70m 2 / g;

[0011] Feature three: The porosity of the core material is 30%-60%;

[0012] Feature four: The core material has a flower-like morphology;

[0013] Feature five: The core material is a porous spherical material composed of Ni(OH)2 nanosheets.

[0014] In an alternative embodiment, the thickness of the shell material is 50 nm - 300 nm; and / or, the shell material is formed of at least one of an oxide of element M and a hydroxide of element M.

[0015] In an alternative embodiment, the mass ratio of the core material to the shell material is (100:1)-(100:5).

[0016] In an alternative embodiment, the D of the cathode lithium supplement precursor 50 ≤4 μm; and / or, the specific surface area of the cathode lithium supplement precursor is 30 m 2 / g - 60 m 2 / g.

[0017] In a second aspect, the present disclosure provides a method for preparing a cathode lithium supplement precursor according to any one of the foregoing embodiments, comprising the following steps: preparing a shell material on the surface of the core material.

[0018] In an alternative embodiment, the preparation of the core material includes: mixing a nickel salt solution with a first precipitant to carry out a precipitation reaction to form Ni(OH)2.

[0019] In an alternative embodiment, the nickel salt solution includes at least one of nickel acetate, nickel nitrate, nickel chloride, nickel sulfate, or nickel oxalate.

[0020] In an alternative embodiment, the first precipitant includes at least one of a urea solution, ammonia water, and a sodium hydroxide solution.

[0021] In an alternative embodiment, the concentration of the first precipitant is 10 wt% - 25 wt%, and the molar ratio of the first precipitant to the nickel element in the nickel salt solution is (2.0:1)-(5.0:1).

[0022] In an alternative embodiment, the pH value of the precipitation reaction is 7 - 11; and / or, the time of the precipitation reaction is 3 h - 8 h.

[0023] In an alternative embodiment, the preparation of the shell material includes: mixing the core material with an oxide of element M in the shell material to obtain a mixed solution; subjecting the mixed solution to a heating and pressurizing reaction to form a shell material on the surface of the core material.

[0024] In an alternative embodiment, the mass ratio of the oxide formed by element M in the core material to the oxide formed by element M in the shell material is (100:1)-(100:5).

[0025] In an alternative embodiment, the heat and pressure reaction includes at least one of the following features:

[0026] Feature 1: The temperature of the heat and pressure reaction is 60°C - 200°C;

[0027] Feature 2: The pressure of the heat and pressure reaction is 1 MPa - 14 MPa;

[0028] Feature 3: The time of the heat and pressure reaction is 6 h - 10 h.

[0029] In an alternative embodiment, the preparation of the shell material includes: mixing the soluble salt solution of element M in the core material and the shell material with a second precipitating agent for coprecipitation reaction to form the shell material on the surface of the core material.

[0030] In an alternative embodiment, the second precipitating agent includes at least one of urea solution, ammonia water, and sodium hydroxide solution; and / or, the concentration of the second precipitating agent is 10 wt% - 25 wt%, and the molar ratio of the second precipitating agent to element M in the soluble salt solution of M is (2.0:1)-(2.5:1).

[0031] In an alternative embodiment, the mass ratio of the hydroxide formed by element M in the core material to the hydroxide formed by element M in the shell material is (100:1)-(100:5).

[0032] In an alternative embodiment, the pH value of the coprecipitation reaction is 7 - 11, and / or, the time of the coprecipitation reaction is 3 h - 8 h.

[0033] In a third aspect, the present disclosure provides a cathode lithium supplement agent, and the precursor of the cathode lithium supplement agent is the cathode lithium supplement agent precursor of any one of the foregoing embodiments.

[0034] In an alternative embodiment, the cathode lithium supplement agent includes primary particles containing Li2NiO2 formed by reacting the cathode lithium supplement agent precursor with a lithium source, and a carbon coating layer coated on the surface of the primary particles.

[0035] In an alternative embodiment, the particle size D of the primary particles 50 ≤10 μm; and / or, the mass ratio of the carbon coating layer to the primary particles is (1:100)-(5:100).

[0036] Fourthly, the present disclosure provides a method for preparing a cathode lithium supplement as described in any one of the foregoing embodiments, comprising the following steps: mixing a cathode lithium supplement precursor with a lithium source and then performing a first sintering.

[0037] In an optional embodiment, the molar ratio of the metal element in the cathode lithium supplement precursor to the lithium in the lithium source is (1:2)-(1:2.5).

[0038] In an optional embodiment, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium oxide, lithium oxalate, and lithium nitrate.

[0039] In an optional embodiment, the first sintering includes at least one of the following features:

[0040] Feature 1: The temperature of the first sintering is 450°C - 650°C;

[0041] Feature 2: The time of the first sintering is 10h - 20h;

[0042] Feature 3: The first sintering is carried out in an inert atmosphere.

[0043] In an optional embodiment, it further includes: crushing the first sintered material obtained from the first sintering, then mixing it with a carbon source, and performing a second sintering.

[0044] In an optional embodiment, the D of the crushed first sintered material 50 is 1.0μm - 5.0μm, and the D 99 is 10μm - 20μm.

[0045] In an optional embodiment, the carbon source is an organic carbon source.

[0046] In an optional embodiment, the organic carbon source includes at least one of phenolic resin, epoxy resin, glucose, sucrose, polyaniline, polypyrrole, polyacetylene, polythiophene, and polydopamine.

[0047] In an optional embodiment, the second sintering includes at least one of the following features:

[0048] Feature 1: The temperature of the second sintering is 100°C - 500°C;

[0049] Feature 2: The time of the second sintering is 4h - 15h;

[0050] Feature 3: The second sintering is carried out in an inert atmosphere;

[0051] Feature 4: The second sintering is dynamic sintering.

[0052] Fifth aspect, the present disclosure provides an application of a cathode lithium supplement agent as described in any one of the foregoing embodiments, for example, for preparing a lithium-ion battery.

[0053] Sixth aspect, the present disclosure provides a lithium-ion battery, and its preparation raw materials include the cathode lithium supplement agent as described in any one of the foregoing embodiments.

[0054] The beneficial effects of the present disclosure include:

[0055] The cathode lithium supplement agent precursor provided by the present disclosure has a core-shell structure. A solid solution can be formed between the core and the shell. Moreover, the shell material can form a lithium-containing metal oxide with a lithium source at low temperature. The formed lithium-containing metal oxide can act as a catalyst, promoting the lithium source to continue to react with the internal core material, reducing the energy barrier of the reaction, and ultimately enabling the sintering reaction between the precursor and the lithium source to proceed at a relatively low temperature (for example, not exceeding 650 °C). The lithium supplement agent material further prepared from this precursor has a relatively high purity and good stability, which is beneficial for preparing a lithium-ion battery with better charge capacity and first charge efficiency. Description of the Drawings

[0056] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present disclosure, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can also be obtained based on these drawings without creative efforts.

[0057] Figure 1 SEM image of the core material Ni(OH)2 of Example 1 of the present disclosure;

[0058] Figure 2 SEM image of the cathode lithium supplement agent precursor of Example 1 of the present disclosure;

[0059] Figure 3 Schematic structural diagram of the cathode lithium supplement agent precursor of Example 1 of the present disclosure;

[0060] Figure 4 SEM image of the cathode lithium supplement agent of Example 1 of the present disclosure;

[0061] Figure 5 SEM image of the commercially available Ni(OH)2 of Comparative Example 1 of the present disclosure;

[0062] Figure 6 SEM image of the cathode lithium supplement agent of Comparative Example 1 of the present disclosure;

[0063] Figure 7 XRD patterns of the cathode lithium supplement agents of Example 1, Comparative Example 1, and Comparative Example 2 of the present disclosure;

[0064] Figure 8 Charge curves of the positive electrode lithium supplement agents of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the present disclosure;

[0065] Figure 9 Hygroscopicity rate curves of the positive electrode lithium supplement agents of Example 1, Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 9 of the present disclosure. Detailed implementation manners

[0066] To make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0067] The positive electrode lithium supplement agent, its precursor and the preparation method provided by the present disclosure will be specifically described below.

[0068] The present disclosure provides a positive electrode lithium supplement agent precursor, which includes a core material and a shell material coated on the surface of the core material.

[0069] The positive electrode lithium supplement agent precursor has a core-shell structure. A solid solution can be formed between the core and the shell. Moreover, the shell material can form a lithium-containing metal oxide with a lithium source at low temperature. The formed lithium-containing metal oxide can act as a catalyst to promote the lithium source to continue to react with the internal core material, reduce the energy barrier of the reaction, and finally enable the sintering reaction between the precursor and the lithium source to be carried out at a lower temperature (for example, not exceeding 650 °C), playing a role in reducing the temperature of the sintering reaction between the precursor and the lithium source, and enabling a high-purity lithium supplement agent material to be obtained under low-temperature conditions, thereby reducing the processing cost.

[0070] In the present disclosure, the above-mentioned core material is a porous spherical material composed of nanosheets and has strong adsorption ability. The core material contains Ni(OH)2. In some embodiments, the core material is a porous spherical material composed of Ni(OH)2 nanosheets.

[0071] By reference, the above-mentioned core material has a flower-like morphology, and its D 50 can be 1 μm - 3 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm, etc., or any other value within the range of 1 μm - 3 μm.

[0072] The specific surface area of the core material can be 40 m 2 / g - 70 m 2 / g, such as 40 m 2 / g, 45 m 2 / g, 50 m2 / g, 55 m 2 / g, 60 m 2 / g, 65 m 2 / g or 70 m 2 / g, etc., or it can also be 40 m 2 / g - 70 m 2 Any other arbitrary value within the range of / g.

[0073] The porosity of the core material can be 30% - 60%, such as 30%, 35%, 40%, 45%, 50%, 55% or 60%, etc., or it can also be any other arbitrary value within the range of 30% - 60%.

[0074] The core material with the above particle size range, specific surface area and porosity is beneficial to reducing the sintering temperature of the reaction between the precursor and the lithium source. If the D of the core material 50 < 1 μm, it is likely to cause incomplete coating of the core material in the shell material; if the D of the core material 50 > 3 μm, it is likely to cause an excessive thickness of the shell material. If the specific surface area of the core material is greater than 70 m 2 / g and the porosity of the core material is greater than 60%, it is likely to cause incomplete coating of the core material in the shell material.

[0075] The shell material contains at least one of the oxide of element M and the hydroxide of element M. Element M can exemplarily but non - restrictively include at least one of Mn, Co, Cu, Mg, Ca, Fe, Sr, Al and Ti. In some embodiments, the shell material is formed by at least one of the oxide of element M and the hydroxide of element M.

[0076] As a reference, the thickness of the shell material can be 50 nm - 300 nm, such as 50 nm, 100 nm, 150 nm, 200 nm, 250 nm or 300 nm, etc., or it can also be any other arbitrary value within the range of 50 nm - 300 nm.

[0077] If the thickness of the shell material is less than 50 nm, it is not conducive to the exertion of the catalytic performance of the shell material; if the thickness of the shell material is greater than 300 nm, it is not conducive to the improvement of the overall capacity of the finished material, nor is it conducive to the improvement of the overall purity of the sample.

[0078] In some alternative embodiments, the mass ratio of the core material to the shell material can be (100:1) - (100:5), such as 100:1, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5 or 100:5, etc., or it can also be any other arbitrary value within the range of (100:1) - (100:5).

[0079] If the mass ratio of the core material to the shell material is less than 100:1, such as 100:0.5, it is not conducive to the exertion of the catalytic performance of the shell material; if the mass ratio of the core material to the shell material is greater than 100:5, such as 100:8, it is not conducive to the improvement of the overall capacity of the finished material, nor is it conducive to the improvement of the overall purity of the sample.

[0080] In the present disclosure, the D of the cathode lithium supplement precursor 50 ≤ 4 μm. The specific surface area of the cathode lithium supplement precursor is 30 m 2 / g - 60 m 2 / g.

[0081] The above-mentioned cathode lithium supplement precursor has a relatively high specific surface area and high reaction activity, which can ensure sufficient surface contact between the precursor and the lithium source during the mixing process, and thus can increase the reaction sites between the precursor and the lithium source during the sintering reaction.

[0082] Correspondingly, the present disclosure also provides a preparation method of the above-mentioned cathode lithium supplement precursor, which may include the following steps: preparing a shell material on the surface of the core material.

[0083] As a reference, the preparation of the core material may include: mixing a nickel salt solution with a first precipitating agent to carry out a precipitation reaction to form Ni(OH)2.

[0084] Among them, the nickel salt solution may exemplarily but non-limitingly include at least one of nickel acetate, nickel nitrate, nickel chloride, nickel sulfate or nickel oxalate.

[0085] The first precipitating agent includes at least one of a urea solution, ammonia water and a sodium hydroxide solution. The concentration of the first precipitating agent can be 10 wt% - 25 wt%, such as 10 wt%, 15 wt%, 20 wt% or 25 wt% etc., and can also be any other value within the range of 10 wt% - 25 wt%. The molar ratio of the first precipitating agent to the nickel element in the nickel salt solution can be (2.0:1) - (5.0:1), such as (2.0:1), (2.5:1), (3.0:1), (3.5:1), (4.0:1), (4.5:1) or (5.0:1) etc.

[0086] The pH value of the above-mentioned precipitation reaction can be 7 - 11, such as 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5 or 11 etc., and can also be any other value within the range of 7 - 11. The time of the precipitation reaction can be 3 h - 8 h, such as 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h or 8 h etc., and can also be any other value within the range of 3 h - 8 h.

[0087] In some embodiments, the preparation of the shell material may include: mixing the core material with the oxide of element M in the shell material to obtain a mixed solution; subjecting the mixed solution to a heating and pressurizing reaction to form the shell material on the surface of the core material.

[0088] The mass ratio of the above-mentioned core material to the oxide formed by element M in the shell material may be (100:1)-(100:5), such as 100:1, 100:2, 100:3, 100:4 or 100:5, etc.

[0089] For reference, the temperature of the heating and pressurizing reaction may be 60°C - 200°C, such as 60°C, 80°C, 100°C, 120°C, 150°C, 180°C or 200°C, etc., and may also be any other value within the range of 60°C - 200°C.

[0090] The pressure of the heating and pressurizing reaction may be 1MPa - 14MPa, such as 1MPa, 2MPa, 5MPa, 8MPa, 10MPa, 12MPa or 14MPa, etc., and may also be any other value within the range of 1MPa - 14MPa.

[0091] The time of the heating and pressurizing reaction may be 6h - 10h, such as 6h, 7h, 8h, 9h or 10h, etc., and may also be any other value within the range of 6h - 10h.

[0092] By carrying out the heating and pressurizing reaction under the above conditions, the oxide of element M can be uniformly coated on the surface of the core material, which is more conducive to improving the reaction activity of the precursor material, so as to obtain a high-purity cathode lithium supplementing agent material by low-temperature sintering of the precursor and the lithium source.

[0093] If the temperature of the heating and pressurizing reaction is lower than 60°C, it is not conducive to the uniform coating of the oxide of element M on the surface of the core material; if the temperature of the heating and pressurizing reaction is higher than 200°C, it is not conducive to the stability of the core-shell structure of the material; if the pressure of the heating and pressurizing reaction is less than 1MPa, it is not conducive to the uniformity of oxide coating; if the pressure of the heating and pressurizing reaction is higher than 14MPa, it is not conducive to the uniform coating of the oxide of element M on the surface of the core material. If the time of the heating and pressurizing reaction is shorter than 6h, it is not conducive to the uniformity of oxide coating; if the time of the heating and pressurizing reaction is longer than 10h, it is not conducive to the stability of the core-shell structure of the material.

[0094] Furthermore, after the heating and pressurizing reaction, the obtained material can also be subjected to post-treatments such as dehydration, washing and drying.

[0095] In some other embodiments, the preparation of the shell material may include: the preparation of the shell material includes: mixing the core material with the soluble salt solution of element M in the shell material and a second precipitating agent for coprecipitation reaction to form the shell material on the surface of the core material.

[0096] The mass ratio of the hydroxide formed by the M element in the above nuclear material and the shell material can be (100:1)-(100:5), such as 100:1, 100:2, 100:3, 100:4 or 100:5, etc.

[0097] Among them, the second precipitant may include at least one of urea solution, ammonia water and sodium hydroxide solution. The concentration of the second precipitant can also be 10wt%-25wt%. The molar ratio of the second precipitant to the M element in the soluble salt solution of M can be (2.0:1)-(2.5:1), such as 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1, etc.

[0098] Similarly, the pH value of the coprecipitation reaction can also be 7-11, such as 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5 or 11, etc. The time of the coprecipitation reaction can also be 3h-8h, such as 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h, etc.

[0099] Furthermore, after the coprecipitation reaction, the obtained material can also be subjected to post-treatments such as dehydration, washing and drying.

[0100] As mentioned above, the preparation method of the cathode lithium supplement precursor provided by the present disclosure is simple, easy to operate and has a low cost.

[0101] In addition, the present disclosure also provides a cathode lithium supplement, and the precursor used therein is the above-mentioned cathode lithium supplement precursor.

[0102] In the present disclosure, the cathode lithium supplement includes primary particles containing Li2NiO2 formed by the reaction of the cathode lithium supplement precursor and a lithium source, and a carbon coating layer coated on the surface of the primary particles.

[0103] For reference, the particle size D of the primary particles 50 ≤10μm. For example, the particle size of the primary particles can be 10μm, 9μm, 8μm, 7μm, 6μm, 5μm, 4μm, 3μm, 2μm or 1μm, etc., or any other value within the range of ≤10μm.

[0104] If the particle size of the primary particles exceeds 10μm, it is not conducive to the capacity of the finished material to be exerted.

[0105] The mass ratio of the carbon coating layer to the primary particles can be (1:100)-(5:100), such as 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100 or 5:100, etc., and can also be any other value within the range of (1:100)-(5:100).

[0106] If the mass ratio of the carbon coating layer to the primary particles is less than 1:100, such as 0.5:100, it is not conducive to improving the conductivity and stability of the material; if the mass ratio of the carbon coating layer to the primary particles is greater than 5:100, such as 10:100, it is not conducive to reducing the polarization of the material during the charging process of the finished material.

[0107] By coating the carbon coating layer on the surface of the primary particles, the stability and conductivity of the lithium supplement agent can be further improved. For example, the carbon coating layer can provide a good protection barrier for the lithium supplement agent to avoid direct contact between the lithium supplement agent and moisture and carbon dioxide in the air, thereby effectively improving the stability of the lithium supplement agent. Moreover, the carbon material used in the coating layer itself can become a part of the conductive material in the battery cell, which is conducive to improving the conductivity.

[0108] Correspondingly, the present disclosure also provides a preparation method of the above-mentioned cathode lithium supplement agent, which may include the following steps: mixing the cathode lithium supplement agent precursor with a lithium source and then performing the first sintering.

[0109] Among them, the molar ratio of the metal element in the cathode lithium supplement agent precursor to the lithium in the lithium source can be (1:2)-(1:2.5), such as 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4 or 1:2.5, etc., and can also be any other value within the range of (1:2)-(1:2.5).

[0110] The lithium source can exemplarily but non-exclusively include at least one of lithium hydroxide, lithium carbonate, lithium oxide, lithium oxalate and lithium nitrate.

[0111] As a reference, the temperature of the first sintering can be 450°C - 650°C, such as 450°C, 480°C, 500°C, 520°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C or 650°C, etc., and can also be any other value within the range of 450°C - 650°C.

[0112] The time of the first sintering can be 10h - 20h, such as 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h, etc., and can also be any other value within the range of 10h - 20h.

[0113] It should be noted that in the preparation process of the current cathode material lithium supplement agent, the precursor and the lithium source usually need to be subjected to high-temperature long-term solid-phase sintering for 10h - 15h under the condition of 750°C - 850°C. However, in the present disclosure, by adopting a specific lithium supplement agent precursor, the sintering temperature of the precursor and the lithium source can be effectively reduced, which is not only more conducive to industrial production, but also can improve the purity of the lithium supplement agent and avoid the generation of impurity phases.

[0114] The first sintering can be carried out in an inert atmosphere, and the gas used can be at least one of nitrogen, argon, helium and neon.

[0115] Furthermore, the first sintered material obtained from the first sintering is crushed, and then mixed with a carbon source for the second sintering.

[0116] For reference, the D 50 of the crushed first sintered material can be 1.0μm - 5.0μm, and the D 99 can be 10μm - 20μm.

[0117] In some alternative embodiments, the carbon source is an organic carbon source, which can include at least one of phenolic resin, epoxy resin, glucose, sucrose, polyaniline, polypyrrole, polyacetylene, polythiophene and polydopamine.

[0118] In the present disclosure, the second sintering can be dynamic low-temperature sintering, and this process can be carried out in a rotary kiln.

[0119] For reference, the temperature of the second sintering can be 100°C - 500°C, such as 100°C, 120°C, 150°C, 180°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C or 500°C, etc., or any other value within the range of 100°C - 500°C.

[0120] The time of the second sintering can be 4h - 15h, such as 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h, etc., or any other value within the range of 4h - 15h.

[0121] The second sintering can also be carried out in an inert atmosphere, and the gas used can be at least one of nitrogen, argon, helium and neon.

[0122] The rotation speed of the rotary kiln can be 1rpm - 3rpm. By adopting the dynamic sintering method, it is beneficial to make the molten carbon source fully contact with the crushed material.

[0123] The present disclosure mixes the crushed first sintered material with an organic carbon source under the protection of an inert atmosphere and performs dynamic solid-phase high-temperature sintering using a rotary kiln, so as to form a dense nano-coated carbon layer on the surface of the first sintered material. And under the above conditions provided by the present disclosure, a better coating effect can be obtained, and the thickness of the coating layer is controllable, which is beneficial to further improving the stability and electrical conductivity of the material.

[0124] Continuing from the above, the present disclosure prepares a lithium supplement precursor with a core-shell structure and a high specific surface area. The shell material of the precursor adsorbs on the core material, can react with a lithium source at a low temperature to generate a lithium-containing metal oxide wrapped on the surface of the core material, and promotes the reaction of the lithium source with Ni(OH)2 to form a good solid solution, thereby playing a role in reducing the sintering temperature and being beneficial to obtaining a high-purity lithium supplement material. By further performing carbon coating, a good protection barrier can be provided for the material to avoid direct contact between the material and moisture and carbon dioxide in the air, thereby improving the stability of the material. Moreover, the carbon coating can also provide the electrical conductivity of the lithium supplement.

[0125] In addition, the present disclosure also provides an application of the above-mentioned cathode lithium supplement, for example, it can be used to prepare a lithium-ion battery.

[0126] Correspondingly, the present disclosure also provides a lithium-ion battery, and its preparation raw materials include the above-mentioned cathode lithium supplement. This lithium-ion battery can have a high charging capacity and a high initial charging efficiency.

[0127] The features and properties of the present disclosure are further described in detail below in conjunction with examples.

[0128] Example 1

[0129] In this example, a cathode lithium supplement was prepared, with the chemical formula Li2NiO2@C, which included primary particles containing Li2NiO2 and a carbon coating layer coated on the surface of the primary particles. The mass ratio of the carbon coating layer to the primary particles was 1:100, and the particle size D of the primary particles 50 ≤10 μm.

[0130] The preparation process of this cathode lithium supplement included:

[0131] Step (1): Add commercial NiCl2·6H2O to deionized water, and obtain a nickel salt solution through stirring and ultrasonic dispersion.

[0132] Step (2): Drop ammonia water (concentration 10%) into the nickel salt solution, the molar ratio of ammonia water to Ni 2+ was 5:1. During the dropping process of ammonia water, stirring and ultrasonic dispersion were maintained, and the pH value of the solution was maintained at 7.5 - 8.5. Then, after aging for 4 h in the container, the core material Ni(OH)2 was obtained through filtration, washing, and drying.

[0133] The D of the core material Ni(OH)2 is 50 2.0 μm, the specific surface area is 48 m 2 / g, and the porosity is 39%.

[0134] Step (3): Add the obtained core material Ni(OH)2 and CuO to water to obtain a mixed solution. The mass ratio of CuO to the core material Ni(OH)2 is 2:100.

[0135] Step (4): Place the mixed solution in step (3) in a high-pressure reactor and react at 120 °C and 10 MPa for 10 h. After the reaction, dehydrate, wash, and dry to obtain the precursor of the cathode lithium supplement agent.

[0136] In the precursor of the cathode lithium supplement agent, the thickness of the shell material is 60 nm. The D of the precursor of the cathode lithium supplement agent is 50 2.2 μm, and the specific surface area is 31 m 2 / g.

[0137] Step (5): Mix the above precursor of the cathode lithium supplement agent and the mixed lithium salt in a molar ratio of Li:Ni = 2.1:1 to obtain a mixture. The mixed lithium salt is composed of lithium hydroxide and lithium oxide in a molar ratio of 5:2.5.

[0138] Step (6): Perform a solid-phase reaction on the mixture obtained in step (5) under a nitrogen atmosphere. Specifically, heat it at a heating rate of 2 °C / min to 450 °C and hold for 4 h, then heat it at a heating rate of 2 °C / min to 600 °C and hold for 10 h, and then naturally cool to room temperature with the furnace temperature to obtain the first sintered material; crush the first sintered material with a jet mill to obtain the first crushed material, and the D of the first crushed material is 50 5 μm, and D 99 is 19 μm.

[0139] Step (7): Mix the phenolic resin and the first crushed material evenly with a high-speed mixer to obtain a mixed material. The addition amount of the phenolic resin is 1 wt% of the first crushed material.

[0140] Step (8): Perform a dynamic high-temperature sintering reaction on the mixed material obtained in step (7) under a nitrogen atmosphere. Specifically, set the rotation rate of the rotary kiln to 1 rpm and heat it at a heating rate of 1 °C / min to 100 °C and hold for 5 h. This process can ensure sufficient contact between the molten carbon source and the first crushed material, and then heat it at a heating rate of 1 °C / min to 350 °C and hold for 5 h to completely carbonize the phenolic resin. After the sintering reaction, naturally cool to room temperature with the furnace temperature to obtain the second sintered material. Crush the second sintered material with a mechanical mill to obtain the final cathode lithium supplement agent, and the D of the cathode lithium supplement agent is50 is 9 μm.

[0141] The SEM of the core material Ni(OH)2 obtained in step (2) of this embodiment is as Figure 1 shown. It can be seen from this figure that the obtained core material Ni(OH)2 has a flower-like morphology.

[0142] The SEM of the cathode lithium supplement precursor obtained in step (4) of this embodiment is as Figure 2 shown, and the structural schematic diagram is as Figure 3 shown. From Figure 2 it can be seen that after the outer surface of the core material Ni(OH)2 is coated, the flower-like morphology of the material is filled with CuO.

[0143] The SEM of the cathode lithium supplement obtained in step (8) of this embodiment is as Figure 4 shown. From Figure 4 it can be seen that the material shows regularly shaped particles and the surface of the sample is clean and smooth.

[0144] Example 2

[0145] This embodiment provides a cathode lithium supplement, and its preparation method includes:

[0146] Steps (1) and (2) are the same as those in Example 1.

[0147] Step (3): Add the core material Ni(OH)2 obtained in step (2) and CuSO4·5H2O to deionized water to obtain a mixed solution. The mass ratio of CuSO4·5H2O to the core material Ni(OH)2 is 5:100.

[0148] Step (4): Add a 10% sodium hydroxide solution dropwise to the mixed solution obtained in step (3). The molar ratio of sodium hydroxide to Cu 2+ is 2.2:1. During the dropping of the sodium hydroxide solution, keep stirring and ultrasonic dispersion, and maintain the pH value of the solution at 7.5 - 8.5, and react for 4 h. After the reaction, filter, wash, and dry to obtain the cathode lithium supplement precursor.

[0149] In this cathode lithium supplement precursor, the thickness of the shell material is 65 nm. The D 50 of this cathode lithium supplement precursor is 2.2 μm, and the specific surface area is 30 m 2 / g.

[0150] Step (5): Mix the above-mentioned cathode lithium supplement precursor and the mixed lithium salt in a molar ratio of Li:Ni = 2.1:1 to obtain a mixture. The mixed lithium salt is composed of lithium hydroxide and lithium oxide in a molar ratio of 6:2.

[0151] Step (6) is the same as that in Example 1.

[0152] Step (7): Mix glucose and the first crushed material evenly with a high-speed mixer to obtain a mixed material. The addition amount of glucose is 1 wt% of the first crushed material.

[0153] Step (8): The same as that in Example 1.

[0154] Example 3

[0155] This example provides a cathode lithium supplement agent, and its preparation method includes:

[0156] Step (1): Add commercial NiSO4·7H2O to deionized water, and obtain a nickel salt solution through stirring and ultrasonic dispersion.

[0157] Step (2): Dropwise add ammonia water (concentration is 10%) into the nickel salt solution, the molar ratio of ammonia water to Ni 2+ is 4:1. During the process of dropping ammonia water, keep stirring and ultrasonic dispersion, and maintain the pH value of the solution at 10.5 - 11. Then, after aging for 4 h in the container, filter, wash, and dry to obtain the core material Ni(OH)2.

[0158] The D of this core material Ni(OH)2 50 is 1.5 nm, the specific surface area is 56 m 2 / g, and the porosity is 45%.

[0159] Step (3): Add the obtained core material Ni(OH)2 and MgO into water to obtain a mixed solution. The mass ratio of MgO to the core material Ni(OH)2 is 2:100.

[0160] Step (4): Place the mixed solution in step (3) into a high-pressure reactor, react at 120 °C and 10 MPa for 10 h. After the reaction, dehydrate, wash, and dry to obtain the precursor of the cathode lithium supplement agent.

[0161] In this precursor of the cathode lithium supplement agent, the thickness of the shell material is 60 nm. The D of this precursor of the cathode lithium supplement agent 50 is 1.6 μm, and the specific surface area is 34 m 2 / g.

[0162] Step (5): Mix the above precursor of the cathode lithium supplement agent and the mixed lithium salt according to the molar ratio of Li:Ni = 2.1:1 to obtain a mixture. The mixed lithium salt is composed of lithium hydroxide and lithium oxide according to the molar ratio of 6:2.

[0163] Step (6): The same as that in Example 1.

[0164] Step (7): Mix glucose and the first crushed material evenly in a high-speed mixer to obtain a mixed material. The addition amount of glucose is 1 wt% of the first crushed material.

[0165] Step (8): The same as in Example 1.

[0166] Example 4

[0167] In this example, a cathode lithium supplement agent was prepared. The difference in its preparation method from that of Example 1 lies in:

[0168] In step (3), the metal oxide is TiO2; in step (5), the molar ratio of lithium hydroxide to lithium oxide in the mixed lithium salts is 4:3.

[0169] Example 5

[0170] In this example, a cathode lithium supplement agent was prepared. The difference in its preparation method from that of Example 1 lies in:

[0171] In step (7), glucose is used instead of phenolic resin as the organic carbon source.

[0172] Example 6

[0173] In this example, a cathode lithium supplement agent was prepared. The difference in its preparation method from that of Example 2 lies in:

[0174] In step (3), MgSO4·H2O is used instead of CuSO4·5H2O.

[0175] Example 7

[0176] In this example, a cathode lithium supplement agent was prepared. The difference in its preparation method from that of Example 1 lies in:

[0177] In step (2), the D of the core material Ni(OH)2 50 is 3.0 μm, the specific surface area is 40 m 2 / g, and the porosity is 30%.

[0178] In step (4), the D of the cathode lithium supplement agent precursor 50 is 3.1 μm, and the specific surface area is 30 m 2 / g.

[0179] Example 8

[0180] In this example, a cathode lithium supplement agent was prepared. The difference in its preparation method from that of Example 1 lies in:

[0181] In step (2), the D of the core material Ni(OH)2 50 is 1 μm, the specific surface area is 56 m 2 / g, and the porosity is 55%.

[0182] In step (4), the D of the positive electrode lithium supplement precursor 50 is 1.1 μm, and the specific surface area is 30 m 2 / g.

[0183] Example 9

[0184] In this example, a positive electrode lithium supplement was prepared. The difference in its preparation method from that of Example 1 is that:

[0185] In step (3), the mass ratio of CuO to the core material Ni(OH)2 is 5:100.

[0186] In step (4), in the positive electrode lithium supplement precursor, the thickness of the shell material is 250 nm. The D of the positive electrode lithium supplement precursor 50 is 2.5 μm, and the specific surface area is 30 m 2 / g.

[0187] Example 10

[0188] In this example, a positive electrode lithium supplement was prepared. The difference in its preparation method from that of Example 1 is that:

[0189] In step (6), the mixture obtained in step (5) was subjected to a solid-phase reaction under a nitrogen atmosphere. Specifically, it was heated to 450 °C at a heating rate of 2 °C / min and held for 4 h, and then heated to 650 °C at a heating rate of 2 °C / min and held for 10 h, and then naturally cooled to room temperature with the furnace temperature to obtain a first sintered material; the first sintered material was pulverized with a jet mill to obtain a first pulverized material, and the D of the first pulverized material 50 is 5 μm, and D 99 is 19 μm.

[0190] Comparative Example 1

[0191] This comparative example provides a positive electrode lithium supplement, which directly uses commercially available Ni(OH)2 as the positive electrode lithium supplement precursor to carry out steps (5) to (8) in Example 1.

[0192] The SEM of the commercially available Ni(OH)2 in this comparative example is as Figure 5 shown.

[0193] The SEM of the positive electrode lithium supplement obtained in this comparative example is as Figure 6 shown.

[0194] From Figure 5 and Figure 6It can be seen that the commercially available Ni(OH)₂ has spherical particles with a dense surface. Compared with the Ni(OH)₂ precursor with a core-shell structure provided in Example 1 of the present disclosure, its reaction activity is lower, and there is no outer shell material as a catalyst. Therefore, its reaction with the lithium source at 600 °C (lower than 650 °C) is relatively incomplete, with a relatively large amount of residual nickel oxide, and the reaction effect is relatively poor.

[0195] However, for the self-prepared Ni(OH)₂ precursor with a core-shell structure provided in Example 1 of the present disclosure, the shell material therein can form a lithium-containing metal oxide with the lithium source at low temperature, and the formed lithium-containing metal oxide can act as a catalyst, promoting the lithium source to continue to react with the internal core material, reducing the energy barrier of the reaction, and ultimately enabling the entire reaction to proceed at 600 °C.

[0196] Comparative Example 2

[0197] This comparative example provides a cathode lithium supplement agent, which is different from Comparative Example 1 in that: a mixture of commercially available Ni(OH)₂ and mixed lithium salts is subjected to a high-temperature solid-phase reaction under a nitrogen atmosphere, heated to 450 °C at a heating rate of 2 °C / min and held for 4 h, and then heated to 750 °C at a heating rate of 2 °C / min, and after holding for 10 h, it is naturally cooled to room temperature with the furnace temperature to obtain the first sintered material.

[0198] All other operations and conditions are the same.

[0199] Comparative Example 3

[0200] This comparative example provides a cathode lithium supplement agent with the chemical formula Li₂NiO₂ and no carbon coating layer.

[0201] The difference in the preparation process of this cathode lithium supplement agent from that of Example 1 lies in: the steps related to carbon-free coating (steps (7) and (8)).

[0202] Comparative Example 4

[0203] This comparative example provides a cathode lithium supplement agent with the chemical formula Li₂NiO₂ and no carbon coating layer.

[0204] The difference in the preparation process of this cathode lithium supplement agent from that of Comparative Example 1 lies in: the steps related to carbon-free coating.

[0205] Comparative Example 5

[0206] This comparative example prepared a cathode lithium supplement agent, and the difference in its preparation method from that of Example 1 lies in:

[0207] In step (3), the mass ratio of CuO to the core material Ni(OH)₂ is 10:100.

[0208] In step (4), in the cathode lithium supplement precursor, the thickness of the shell material is 500 nm. The D of the cathode lithium supplement precursor 50 is 4 μm, and the specific surface area is 20 m 2 / g.

[0209] Comparative Example 6

[0210] In this comparative example, a cathode lithium supplement was prepared. The difference in its preparation method from that of Example 1 lies in:

[0211] In step (4), the mixed solution from step (3) was placed in a high-pressure reactor and reacted at 250 °C and 20 MPa for 15 h. After the reaction, dehydration, washing, and drying were carried out to obtain the cathode lithium supplement precursor.

[0212] In the cathode lithium supplement precursor, the thickness of the shell material is 500 nm. The D of the cathode lithium supplement precursor 50 is 3 μm, and the specific surface area is 20 m 2 / g.

[0213] Comparative Example 7

[0214] In this comparative example, a cathode lithium supplement was prepared. The difference in its preparation method from that of Example 1 lies in:

[0215] In step (6), the first sintered material was pulverized with a jet mill to obtain the first pulverized material. The D of the first pulverized material 50 is 15 μm, and the D 99 is 25 μm.

[0216] In step (8), the second sintered material was pulverized with a mechanical mill to obtain the final cathode lithium supplement. The D of the cathode lithium supplement 50 is 16 μm.

[0217] Comparative Example 8

[0218] In this comparative example, a cathode lithium supplement was prepared. The difference in its preparation method from that of Example 1 lies in:

[0219] In step (7), phenolic resin and the first pulverized material were mixed evenly with a high-speed mixer to obtain a mixed material. The addition amount of phenolic resin is 10 wt% of the first pulverized material.

[0220] Comparative Example 9

[0221] In this comparative example, a cathode lithium supplement was prepared. The difference in its preparation method from that of Example 1 lies in:

[0222] In step (8), the mixed material obtained in step (7) is subjected to a static high-temperature sintering reaction in a box furnace under a nitrogen atmosphere. Specifically, it is heated to 100°C at a heating rate of 1°C / min and held for 5 h, and then heated to 350°C at a heating rate of 1°C / min and held for 5 h to completely carbonize the phenolic resin. After the sintering reaction, it is naturally cooled to room temperature with the furnace temperature to obtain a second sintered material. The second sintered material is pulverized with a mechanical grinder to obtain the final cathode lithium supplement agent, and the D of the cathode lithium supplement agent 50 is 9 μm.

[0223] In this comparative example, the cathode lithium supplement agent uses a static coating method. The moisture absorption rate of the finally obtained material is higher than that of the material after dynamic coating, but lower than that of the uncoated material, further proving that dynamic carbon coating can improve the coating uniformity of the material and thus improve the air stability of the material.

[0224] Test Example

[0225] (1) Structure comparison

[0226] The cathode lithium supplement agents of Example 1, Comparative Example 1 and Comparative Example 2 were characterized by XRD, and the results are as Figure 7 shown.

[0227] It can be seen from Figure 7 the XRD results corresponding to Comparative Example 2 that the peak intensity of nickel oxide is reduced relative to Comparative Example 1, but not as good as that of Example 1, indicating that commercial Ni(OH)2 can only approach the low-temperature sintering effect of the self-made Ni(OH)2 precursor provided in Example 1 of the present disclosure when reacting at a high temperature (750°C).

[0228] (2) Electrochemical performance

[0229] The cathode lithium supplement agents provided in Examples 1-10 and Comparative Examples 1-9 were respectively made into coin cells according to the following method:

[0230] ① Prepare the slurry: Weigh 3.6 g of the cathode lithium supplement agent, conductive agent, and binder and mix them. The mass ratio of the cathode lithium supplement agent, conductive agent, and binder is 90:5:5. The binder used is PVDF, and the conductive agent is conductive carbon;

[0231] ② Coating: Use a scraper to coat on the aluminum foil;

[0232] ③ Drying: Dry the coated electrode sheet in a vacuum drying oven at a drying temperature of 110°C for 2 h;

[0233] ④ Pressing: Press the dried electrode sheet with a pair-roll press;

[0234] ⑤ Assemble the battery components such as the positive electrode plate, negative electrode plate (lithium metal sheet with a diameter of 16 mm), separator (polypropylene microporous separator), and electrolyte (1 mol / L LiPF6 solution, the solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1) into a button cell.

[0235] Test the charging capacity and initial efficiency of the obtained button cell under the conditions of a charging voltage of 4.25 V and a charging rate of 0.1 C. The results are shown in Table 1 and Figure 8 as follows.

[0236] Table 1 Test Results

[0237] Charge capacity (mAh / g) Initial charge efficiency (%) Example 1 392.0 33.0 Example 2 390.0 32.8 Example 3 387.1 32.3 Example 4 392.2 32.8 Example 5 395.0 32.3 Example 6 396.0 32.6 Example 7 391.6 32.9 Example 8 389.9 32.4 Example 9 393.5 32.5 Example 10 395.0 33.0 Comparative Example 1 285.8 31.9 Comparative Example 2 380.2 31.1 Comparative Example 3 385.0 31.0 Comparative Example 4 376.0 31.1 Comparative Example 5 385.0 27.9 Comparative Example 6 369.5 32.1 Comparative Example 7 361.0 31.4 Comparative Example 8 363.7 31.7 Comparative Example 9 380.0 31.8

[0238] From Table 1 and Figure 8 it can be seen that: The batteries provided by Example 1 and Example 2 of the present disclosure obtained from the self-made Ni(OH)2 precursor are superior in terms of charging capacity and initial charging efficiency to the batteries obtained from commercially available Ni(OH)2.

[0239] Combining Example 1, Example 2, Comparative Example 1, and Comparative Example 2 shows that only by reacting the commercially available Ni(OH)2 precursor with a lithium source at a high temperature (750 °C) can the effect of low-temperature sintering of the self-made Ni(OH)2 precursor with a core-shell structure and the lithium source in Example 1 be approximated. Furthermore, it is proved that the specific Ni(OH)2 precursor in the present disclosure can effectively reduce the temperature required for sintering with the lithium source.

[0240] (3) Air stability

[0241] Conduct a moisture absorption rate experiment on the positive electrode lithium supplement agents provided by Example 1, Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 9 to characterize the air stability of different carbon-coated materials.

[0242] The specific steps are as follows: ① Weigh 5 g of the lithium-ion battery positive electrode prelithiation agent materials of Example 1, Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 9 respectively, and place them in a petri dish with a diameter of 90 mm; ② Place them in a thermostatic and humidistatic chamber, adjust the temperature to 25 °C, and adjust the humidity to 30%; ③ Place them in the thermostatic and humidistatic chamber for 2 hours. During this process, record the material mass every 30 minutes; ④ Calculate the moisture absorption rate of each material and compare them. The moisture absorption rate curves are as Figure 9 follows.

[0243] From Figure 9 it can be seen that: The moisture absorption rate of the carbon-coated positive electrode lithium supplement material is lower than that of the uncoated lithium supplement agent material, and the moisture absorption rate of the material after dynamic coating is lower than that of the material after static coating, which also indicates that carbon coating can improve the stability of the material.

[0244] In summary, the core-shell structure of the positive electrode lithium supplement precursor provided by the present disclosure enables the formation of a solid solution between the core and the shell. Moreover, the shell material can form a lithium-containing metal oxide with the lithium source at low temperatures, and the formed lithium-containing metal oxide can act as a catalyst to promote the continuous reaction between the lithium source and the internal core material, reducing the energy barrier of the reaction. Eventually, the sintering reaction between the precursor and the lithium source can be carried out at a relatively low temperature (e.g., not exceeding 650 °C). The lithium supplement material further prepared from this precursor has a high purity and good stability, which is beneficial for the preparation of lithium-ion batteries with both good charge capacity and first charge efficiency.

[0245] Industrial Applicability

[0246] The specific positive electrode lithium supplement precursor provided by the present disclosure can sinter with the lithium source under low-temperature conditions to obtain a lithium supplement material with high purity, which is beneficial for reducing production costs and energy consumption and is suitable for industrial production. The lithium supplement material with a carbon coating layer provided by the present disclosure has good stability and electrochemical performance, which is beneficial for the preparation of lithium-ion batteries with both good charge capacity and first charge efficiency.

Claims

1. A precursor of a cathode lithium supplement agent, characterized in that, The positive electrode lithium supplement precursor includes a core material and a shell material coated on the surface of the core material; wherein, the core material is a porous spherical material composed of nanosheets, and the core material contains Ni(OH)2; the shell material contains at least one of an oxide of element M and a hydroxide of element M, and the element M includes at least one of Mn, Co, Cu, Mg, Ca, Fe, Sr, Al, and Ti; The preparation of the positive electrode lithium supplement precursor includes the following steps: preparing the shell material on the surface of the core material; the preparation of the shell material includes: mixing the core material with an oxide of element M in the shell material to obtain a mixed solution; performing a heating and pressurizing reaction on the mixed solution to form a shell material on the surface of the core material.

2. The precursor for cathode lithium supplement agent according to claim 1, wherein The core material has at least one of the following characteristics: Feature 1: The D of the nuclear material 50 is 1 μm - 3 μm; Feature 2: The specific surface area of the nuclear material is 40 m 2 / g - 70 m 2 / g; Characteristic three: The porosity of the core material is 30%-60%; Characteristic four: The core material has a flower-like morphology; Characteristic five: The core material is a porous spherical material composed of Ni(OH)2 nanosheets.

3. The precursor for cathode lithium supplement agent according to claim 1, characterized in that, The thickness of the shell material is 50nm-300nm; and / or, the shell material is formed by at least one of an oxide of element M and a hydroxide of element M.

4. The precursor of the cathode lithium supplement agent according to any one of claims 1-3, characterized in that, The mass ratio of the core material to the shell material is (100:1)-(100:5).

5. The precursor of the cathode lithium supplement agent according to claim 1, characterized in that, The D of the positive electrode lithium supplement precursor 50 ≤ 4 μm; and / or, the specific surface area of the positive electrode lithium supplement precursor is 30 m 2 / g - 60 m 2 / g.

6. A preparation method of a cathode lithium supplement precursor as described in any one of claims 1-5, characterized in that, Including the following steps: Preparing the shell material on the surface of the core material; The preparation of the shell material includes: mixing the core material with an oxide of element M in the shell material to obtain a mixed solution; Performing a heating and pressurizing reaction on the mixed solution to form a shell material on the surface of the core material.

7. The preparation method according to claim 6, wherein The preparation of the core material includes: mixing a nickel salt solution with a first precipitant to perform a precipitation reaction and form Ni(OH)2.

8. The preparation method according to claim 7, wherein The nickel salt solution includes at least one of nickel acetate, nickel nitrate, nickel chloride, nickel sulfate, or nickel oxalate.

9. The preparation method according to claim 7 or 8, characterized in that, The first precipitant includes at least one of a urea solution, ammonia water, and a sodium hydroxide solution.

10. The preparation method according to claim 7 or 8, characterized in that, The concentration of the first precipitant is 10wt%-25wt%, and the molar ratio of the first precipitant to the nickel element in the nickel salt solution is (2.0:1)-(5.0:1).

11. The preparation method according to claim 7 or 8, characterized in that, The pH value of the precipitation reaction is 7-11; and / or, the time of the precipitation reaction is 3h-8h.

12. The preparation method according to claim 6, characterized in that, The heating and pressurizing reaction includes at least one of the following characteristics: Characteristic one: The temperature of the heating and pressurizing reaction is 60°C-200°C; Characteristic two: The pressure of the heating and pressurizing reaction is 1MPa-14MPa; Characteristic three: The time of the heating and pressurizing reaction is 6h-10h.

13. The preparation method according to claim 6, characterized in that, The preparation of the shell material includes: mixing the core material with a soluble salt solution of element M in the shell material and a second precipitant to perform a coprecipitation reaction to form a shell material on the surface of the core material.

14. The preparation method according to claim 13, characterized in that, The second precipitating agent includes at least one of urea solution, ammonia water, and sodium hydroxide solution; and / or, the concentration of the second precipitating agent is 10 wt% - 25 wt%, and the molar ratio of the second precipitating agent to the M element in the soluble salt solution of M is (2.0:1) - (2.5:1).

15. The preparation method according to claim 13 or 14, characterized in that, The pH value of the coprecipitation reaction is 7 - 11, and / or, the time of the coprecipitation reaction is 3 h - 8 h.

16. A cathode lithium supplement, characterized in that, The precursor of the cathode lithium supplementing agent is the precursor of the cathode lithium supplementing agent according to any one of claims 1 - 5.

17. The cathode lithium supplement according to claim 16, wherein, The cathode lithium supplementing agent includes primary particles containing Li2NiO2 formed by reacting the precursor of the cathode lithium supplementing agent with a lithium source, and a carbon coating layer coated on the surface of the primary particles.

18. The cathode lithium supplement agent according to claim 17, characterized in that, The particle size D of the primary particles 50 ≤ 10 μm; and / or, the mass ratio of the carbon coating layer to the primary particles is (1:100)-(5:100).

19. A method for preparing a cathode lithium supplement as described in any one of claims 16-18, characterized in that, It includes the following steps: Mix the precursor of the cathode lithium supplementing agent with the lithium source and then conduct the first sintering.

20. The preparation method according to claim 19, wherein The molar ratio of the metal element in the precursor of the cathode lithium supplementing agent to the lithium in the lithium source is (1:2) - (1:2.5).

21. The preparation method according to claim 19 or 20, characterized in that, The lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium oxide, lithium oxalate, and lithium nitrate.

22. The preparation method according to claim 19, characterized in that, The first sintering includes at least one of the following features: Feature 1: The temperature of the first sintering is 450°C - 650°C; Feature 2: The time of the first sintering is 10 h - 20 h; Feature 3: The first sintering is carried out in an inert atmosphere.

23. The preparation method according to claim 19, characterized in that, It also includes: Crush the first sintered material obtained from the first sintering, then mix it with a carbon source and conduct the second sintering.

24. The preparation method according to claim 23, wherein The D of the first sintered material after crushing 50 is 1.0 μm - 5.0 μm, and the D 99 is 10 μm - 20 μm.

25. The preparation method according to claim 23, wherein, The carbon source is an organic carbon source.

26. The preparation method according to claim 25, wherein, The organic carbon source includes at least one of phenolic resin, epoxy resin, glucose, sucrose, polyaniline, polypyrrole, polyacetylene, polythiophene, and polydopamine.

27. The preparation method according to any one of claims 23-26, characterized in that, The second sintering includes at least one of the following features: Feature 1: The temperature of the second sintering is 100°C - 500°C; Feature 2: The time of the second sintering is 4 h - 15 h; Feature 3: The second sintering is carried out in an inert atmosphere; Feature 4: The second sintering is dynamic sintering.

28. Use of a cathode lithium supplement as described in any one of claims 16-18, characterized in that, The cathode lithium supplementing agent is used for preparing a lithium-ion battery.

29. A lithium-ion battery, characterized in that, The preparation raw materials of the lithium-ion battery include the cathode lithium supplementing agent according to any one of claims 16 - 18.

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