Positive electrode lithium-supplementing agent, and precursor thereof, preparation method therefor and use thereof

Abstract

The present disclosure belongs to the technical field of lithium-supplementing agents, and disclosed are a positive electrode lithium-supplementing agent, and a precursor thereof, a preparation method therefor and the use thereof. The positive electrode lithium-supplementing agent precursor comprises a core material and a shell material, which coats 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; and the shell material contains at least one of an oxide of an M element and a hydroxide of the M element, with the M comprising at least one of Mn, Co, Cu, Mg, Ca, Fe, Sr, Al and Ti. The shell material of the precursor is adsorbed on the core material and can react with a lithium source at low temperatures, so as to generate a lithium-containing metal oxide, which coats the surface of the core material and promotes a reaction between the lithium source and Ni(OH)2 to form a good solid solution, thereby realizing the effect of reducing the sintering temperature and facilitating obtaining a high-purity lithium-supplementing material. The positive electrode lithium-supplementing agent prepared from the precursor has low hygroscopicity and high stability.

Description

A positive electrode lithium supplement and its precursor as well as preparation method and application Technical Field

[0001] The present disclosure relates to the technical field of lithium supplement agents, and in particular to a positive electrode lithium supplement agent, a precursor thereof, a preparation method and applications thereof. Background Art

[0002] Currently, new energy vehicles are placing increasingly higher demands on the range of their power batteries, which in turn places higher demands on the cycle capacity of power battery materials. During the charge and discharge process, lithium-ion batteries form a CEI (surface electrolyte interface) film on the surface of the positive electrode material and a SEI (solid electrolyte interface) film on the surface of the negative electrode material. These two processes irreversibly deplete the active lithium in the original materials, reducing the battery's charge and discharge efficiency and resulting in a loss of battery capacity.

[0003] Lithium-rich nickel oxides and other cathode materials are relatively safe, reliable, and low-cost. They can release a large amount of lithium ions during the first charge, and the products after the release of lithium ions are extremely inactive, preventing reinsertion or dissolution. This can significantly improve the cycle efficiency and energy density of lithium-ion batteries. However, the current preparation process for cathode material lithium supplements requires a long-term, high-temperature solid-phase sintering of the precursor and lithium source under relatively stringent conditions. This results in poor stability of the corresponding cathode material lithium supplements, and when used in batteries, the battery's charging capacity and initial charge efficiency are suboptimal.

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

[0005] Summary of the Invention

[0006] The purpose of the present disclosure includes providing a positive electrode lithium supplement agent and its precursor, preparation method and application, so as to solve or improve at least one of the above technical problems.

[0007] The present disclosure can be implemented as follows:

[0008] In a first aspect, the present disclosure provides a positive electrode lithium supplement precursor, 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.

[0009] In an optional embodiment, the core material has at least one of the following characteristics:

[0010] Feature 1: D of the core material 50 1μm-3μm;

[0011] Feature 2: The specific surface area of ​​the core material is 40m 2 / g-70m 2 / g;

[0012] Feature 3: The porosity of the core material is 30%-60%;

[0013] Feature 4: The core material has a flower-like morphology;

[0014] Feature 5: The core material is a porous spherical material composed of Ni(OH)2 nanosheets.

[0015] In an optional embodiment, the shell material has a thickness of 50 nm to 300 nm; and / or the shell material is formed of at least one of an oxide of the M element and a hydroxide of the M element.

[0016] In an optional embodiment, the mass ratio of the core material to the shell material is (100:1)-(100:5).

[0017] In an optional embodiment, the D of the positive electrode lithium supplement precursor 50 ≤4μm; and / or, the specific surface area of ​​the positive electrode lithium supplement precursor is 30m 2 / g-60m 2 / g.

[0018] In a second aspect, the present disclosure provides a method for preparing a positive electrode lithium supplement precursor according to any one of the aforementioned embodiments, comprising the following steps: preparing a shell material on the surface of a core material.

[0019] In an optional embodiment, 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.

[0020] In an optional embodiment, the nickel salt solution includes at least one of nickel acetate, nickel nitrate, nickel chloride, nickel sulfate or nickel oxalate.

[0021] In an optional embodiment, the first precipitant includes at least one of urea solution, ammonia water and sodium hydroxide solution.

[0022] In an optional 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).

[0023] In an optional embodiment, the pH value of the precipitation reaction is 7-11; and / or the precipitation reaction time is 3h-8h.

[0024] In an optional embodiment, the preparation of the shell material includes: mixing the core material with the oxide of the M element in the shell material to obtain a mixed solution; and heating and pressurizing the mixed solution to form the shell material on the surface of the core material.

[0025] In an optional embodiment, the mass ratio of the oxide formed by the core material and the M element in the shell material is (100:1)-(100:5).

[0026] In an optional embodiment, the heated and pressurized reaction includes at least one of the following features:

[0027] Feature 1: The temperature of the heating and pressurizing reaction is 60℃-200℃;

[0028] Feature 2: The pressure of the heating and pressurizing reaction is 1MPa-14MPa;

[0029] Feature 3: The heating and pressurizing reaction time is 6h-10h.

[0030] In an optional embodiment, the preparation of the shell material includes: mixing the core material with a soluble salt solution of the M element in the shell material and a second precipitant to perform a co-precipitation reaction to form the shell material on the surface of the core material.

[0031] In an optional embodiment, the second precipitant includes at least one of urea solution, ammonia water and sodium hydroxide solution; and / or the concentration of the second precipitant is 10wt%-25wt%, and the molar ratio of the second precipitant to the M element in the soluble salt solution of M is (2.0:1)-(2.5:1).

[0032] In an optional embodiment, the mass ratio of the hydroxide formed by the core material and the M element in the shell material is (100:1)-(100:5).

[0033] In an optional embodiment, the pH value of the coprecipitation reaction is 7-11, and / or the coprecipitation reaction time is 3h-8h.

[0034] In a third aspect, the present disclosure provides a positive electrode lithium supplement agent, wherein the precursor of the positive electrode lithium supplement agent is the positive electrode lithium supplement agent precursor of any one of the aforementioned embodiments.

[0035] In an optional embodiment, the positive electrode lithium supplement agent includes primary particles containing Li2NiO2 generated by the reaction of a positive electrode lithium supplement agent precursor and a lithium source, and a carbon coating layer coated on the surface of the primary particles.

[0036] In an alternative embodiment, the particle size D of the primary particles is 50 ≤10μm; and / or, the mass ratio of the carbon coating layer to the primary particles is (1:100)-(5:100).

[0037] In a fourth aspect, the present disclosure provides a method for preparing a positive electrode lithium supplement agent according to any one of the aforementioned embodiments, comprising the following steps: mixing a positive electrode lithium supplement agent precursor with a lithium source and then performing a first sintering.

[0038] In an optional embodiment, the molar ratio of the metal element in the positive electrode lithium supplement agent precursor to the lithium in the lithium source is (1:2)-(1:2.5).

[0039] In an alternative embodiment, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium oxide, lithium oxalate, and lithium nitrate.

[0040] In an optional embodiment, the first sintering includes at least one of the following features:

[0041] Feature 1: The temperature of the first sintering is 450℃-650℃;

[0042] Feature 2: The first sintering time is 10h-20h;

[0043] Feature 3: The first sintering is carried out in an inert atmosphere.

[0044] In an optional embodiment, the method further includes: crushing the first sintered material obtained by the first sintering, then mixing it with a carbon source, and sintering it for a second time.

[0045] In an optional embodiment, the D of the crushed first sintered material is 50 1.0μm-5.0μm, D 99 10μm-20μm.

[0046] In an alternative embodiment, the carbon source is an organic carbon source.

[0047] In an alternative embodiment, the organic carbon source includes at least one of phenolic resin, epoxy resin, glucose, sucrose, polyaniline, polypyrrole, polyacetylene, polythiophene and polydopamine.

[0048] In an optional embodiment, the second sintering includes at least one of the following features:

[0049] Feature 1: The temperature of the second sintering is 100℃-500℃;

[0050] Feature 2: The second sintering time is 4h-15h;

[0051] Feature 3: The second sintering is carried out in an inert atmosphere;

[0052] Feature 4: The second sintering is dynamic sintering.

[0053] In a fifth aspect, the present disclosure provides an application of a positive electrode lithium supplement agent according to any one of the aforementioned embodiments, for example, for preparing a lithium-ion battery.

[0054] In a sixth aspect, the present disclosure provides a lithium-ion battery, the raw materials for preparing the battery include the positive electrode lithium supplement agent of any one of the aforementioned embodiments.

[0055] The beneficial effects of the present disclosure include:

[0056] The cathode lithium supplement precursor provided by the present disclosure has a core-shell structure, forming a solid solution between the core and the shell. Furthermore, the shell material can react with the lithium source at low temperatures to form a lithium-containing metal oxide. The resulting lithium-containing metal oxide acts as a catalyst, prompting the lithium source to continue reacting with the core material inside, lowering the energy barrier for the reaction. Ultimately, this allows the sintering reaction between the precursor and the lithium source to proceed at a relatively low temperature (e.g., no more than 650°C). The lithium supplement material further prepared from this precursor has high purity and good stability, facilitating the preparation of lithium-ion batteries with excellent charge capacity and initial charge efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0058] FIG1 is a SEM image of the core material Ni(OH)2 of Example 1 of the present disclosure;

[0059] FIG2 is a SEM image of the positive electrode lithium supplement precursor of Example 1 of the present disclosure;

[0060] FIG3 is a schematic structural diagram of a cathode lithium supplement precursor according to Example 1 of the present disclosure;

[0061] FIG4 is a SEM image of the positive electrode lithium supplement agent of Example 1 of the present disclosure;

[0062] FIG5 is a SEM image of commercially available Ni(OH)2 of Comparative Example 1 of the present disclosure;

[0063] FIG6 is a SEM image of the positive electrode lithium supplement agent of Comparative Example 1 of the present disclosure;

[0064] FIG7 is an XRD diagram of the positive electrode lithium supplement agent of Example 1, Comparative Example 1 and Comparative Example 2 of the present disclosure;

[0065] FIG8 is a charging curve diagram of the positive electrode lithium supplement agents of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the present disclosure;

[0066] FIG9 is a graph showing moisture absorption rates of the positive electrode lithium replenishing agents of Example 1, Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 9 of the present disclosure. DETAILED DESCRIPTION

[0067] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0068] The following is a detailed description of the positive electrode lithium supplement agent, its precursor, and its preparation method provided by the present disclosure.

[0069] The present disclosure provides a positive electrode lithium supplement precursor, which includes a core material and a shell material coated on the surface of the core material.

[0070] The positive electrode lithium supplement agent precursor has a core-shell structure, and a solid solution can be formed between the core and the shell. Moreover, the shell material can form a lithium-containing metal oxide with the lithium source at low temperature. The formed lithium-containing metal oxide can act as a catalyst, prompting the lithium source to continue to react with the internal core material, reducing the energy barrier of the reaction, and ultimately allowing the sintering reaction between the precursor and the lithium source to proceed at a lower temperature (for example, not exceeding 650°C), thereby reducing the temperature of the sintering reaction between the precursor and the lithium source, and achieving high-purity lithium supplement agent material under low temperature conditions, thereby reducing processing costs.

[0071] In the present disclosure, the core material is a porous spherical material composed of nanosheets, which has a strong adsorption capacity. The core material contains Ni(OH)2. In some embodiments, the core material is a porous spherical material composed of Ni(OH)2 nanosheets.

[0072] As a reference, the above core material has a flower-like morphology, and its D 50 It can be 1 μm-3 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm, or any other value within the range of 1 μm-3 μm.

[0073] The specific surface area of ​​the core material can be 40m 2 / g-70m 2 / g, such as 40m 2 / g、45m 2 / g, 50m 2 / g、55m 2 / g, 60m 2 / g、65m 2 / g or 70m 2 / g, etc., can also be 40m2 / g-70m 2 Any other value within the range of / g.

[0074] The porosity of the core material may be 30%-60%, such as 30%, 35%, 40%, 45%, 50%, 55% or 60%, etc., or any other value within the range of 30%-60%.

[0075] The core material with the above-mentioned particle size range, specific surface area and porosity is beneficial to reduce the sintering temperature of the precursor and lithium source reaction. 50 <1μm, it is easy to cause incomplete coating of the core material by the shell material; if the D 50 >3μm, it is easy to cause the shell material to be too thick. If the specific surface area of ​​the core material is greater than 70m 2 / g, the porosity of the core material is greater than 60%, which easily leads to incomplete coating of the core material by the shell material.

[0076] The shell material contains at least one of an oxide of an M element and a hydroxide of an M element. The M element may illustratively but not limitatively include at least one of Mn, Co, Cu, Mg, Ca, Fe, Sr, Al, and Ti. In some embodiments, the shell material is formed of at least one of an oxide of an M element and a hydroxide of an M element.

[0077] For reference, the thickness of the shell material may be 50 nm-300 nm, such as 50 nm, 100 nm, 150 nm, 200 nm, 250 nm or 300 nm, or any other value within the range of 50 nm-300 nm.

[0078] If the thickness of the shell material is less than 50 nm, it is not conducive to 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.

[0079] In some optional 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 be any other value within the range of (100:1)-(100:5).

[0080] 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 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.

[0081] In the present disclosure, the D of the positive electrode lithium supplement precursor 50 ≤4μm. The specific surface area of ​​the positive electrode lithium supplement precursor is 30m 2 / g-60m 2 / g.

[0082] The above-mentioned positive electrode lithium supplement agent precursor has a high specific surface area and high reaction activity, which can ensure that the precursor and the lithium source have sufficient surface contact during the mixing process, and further increase the reaction sites between the precursor and the lithium source during the sintering reaction.

[0083] Correspondingly, the present disclosure also provides a method for preparing the above-mentioned positive electrode lithium supplement agent precursor, which may include the following steps: preparing a shell material on the surface of a core material.

[0084] For reference, the preparation of the core material may include: mixing a nickel salt solution with a first precipitant to perform a precipitation reaction and form Ni(OH)2.

[0085] The nickel salt solution may illustratively but not limitatively include at least one of nickel acetate, nickel nitrate, nickel chloride, nickel sulfate or nickel oxalate.

[0086] The first precipitant includes at least one of a urea solution, aqueous ammonia, and a sodium hydroxide solution. The concentration of the first precipitant can be 10 wt% to 25 wt%, such as 10 wt%, 15 wt%, 20 wt%, or 25 wt%, or any other value within the range of 10 wt% to 25 wt%. The molar ratio of the first precipitant to the nickel element in the nickel salt solution can be (2.0:1) to (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.

[0087] The pH value of the precipitation reaction can be 7-11, such as 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5 or 11, or any other value within the range of 7-11. The precipitation reaction time 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, or any other value within the range of 3 h-8 h.

[0088] In some embodiments, the preparation of the shell material may include: mixing the core material with an oxide of the M element in the shell material to obtain a mixed solution; and heating and pressurizing the mixed solution to form the shell material on the surface of the core material.

[0089] The mass ratio of the core material to the oxide formed by the M element in the shell material can be (100:1)-(100:5), such as 100:1, 100:2, 100:3, 100:4 or 100:5.

[0090] For reference, the temperature of the heating and pressurizing reaction can be 60°C-200°C, such as 60°C, 80°C, 100°C, 120°C, 150°C, 180°C or 200°C, or any other value within the range of 60°C-200°C.

[0091] The pressure of the heating and pressurizing reaction can be 1 MPa-14 MPa, such as 1 MPa, 2 MPa, 5 MPa, 8 MPa, 10 MPa, 12 MPa or 14 MPa, or any other value within the range of 1 MPa-14 MPa.

[0092] The heating and pressurizing reaction time can be 6 h to 10 h, such as 6 h, 7 h, 8 h, 9 h or 10 h, etc., or any other value within the range of 6 h to 10 h.

[0093] By carrying out a heating and pressurizing reaction under the above conditions, the oxide of the M element can be evenly coated on the surface of the core material, which is more conducive to improving the reaction activity of the precursor material, thereby achieving a high-purity positive electrode lithium supplement material by sintering the precursor and the lithium source at low temperature.

[0094] If the heating and pressurizing reaction temperature 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 heating and pressurizing reaction temperature is higher than 200°C, it is not conducive to the stability of the core-shell structure of the material. If the heating and pressurizing reaction pressure is lower than 1MPa, it is not conducive to the uniformity of the oxide coating. If the heating and pressurizing reaction pressure 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 heating and pressurizing reaction time is shorter than 6h, it is not conducive to the uniformity of the oxide coating. If the heating and pressurizing reaction time is longer than 10h, it is not conducive to the stability of the core-shell structure of the material.

[0095] Furthermore, after the heating and pressurizing reaction, the obtained material may be subjected to post-treatments such as dehydration, washing and drying.

[0096] In other embodiments, the preparation of the shell material may include: the preparation of the shell material includes: mixing the core material with a soluble salt solution of the M element in the shell material and a second precipitant to perform a co-precipitation reaction to form the shell material on the surface of the core material.

[0097] The mass ratio of the core material to the hydroxide formed by the M element in the shell material can be (100:1)-(100:5), such as 100:1, 100:2, 100:3, 100:4 or 100:5.

[0098] The second precipitant may include at least one of a urea solution, aqueous ammonia, and a sodium hydroxide solution. The concentration of the second precipitant may also be 10 wt% to 25 wt%. The molar ratio of the second precipitant to the M element in the soluble salt solution of M may be (2.0:1) to (2.5:1), such as 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, or 2.5:1.

[0099] 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. The coprecipitation reaction time can also be 3h-8h, such as 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h.

[0100] Furthermore, after the coprecipitation reaction, the obtained material may be subjected to post-treatments such as dehydration, washing and drying.

[0101] As mentioned above, the preparation method of the positive electrode lithium supplement agent precursor provided by the present disclosure is simple, easy to operate and has low cost.

[0102] In addition, the present disclosure also provides a positive electrode lithium replenisher, the precursor used by the positive electrode lithium replenisher precursor is the above-mentioned positive electrode lithium replenisher precursor.

[0103] In the present disclosure, the positive electrode lithium supplement agent includes primary particles containing Li2NiO2 generated by the reaction of a positive electrode lithium supplement agent precursor and a lithium source, and a carbon coating layer coated on the surface of the primary particles.

[0104] As a reference, the primary particle size D 50 For example, the particle size of the primary particles may be 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, or 1 μm, or any other value within the range of 10 μm or less.

[0105] If the particle size of the primary particles exceeds 10 μm, it will be detrimental to the capacity of the finished material.

[0106] 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, or any other value within the range of (1:100)-(5:100).

[0107] 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.

[0108] By coating the primary particles with a carbon coating, the stability and conductivity of the lithium supplement can be further improved. For example, the carbon coating provides a protective barrier for the lithium supplement, preventing direct contact with moisture and carbon dioxide in the air, thereby effectively improving its stability. Furthermore, the carbon material used in the coating can itself become part of the conductive material in the battery cell, further enhancing conductivity.

[0109] Correspondingly, the present disclosure also provides a method for preparing the above-mentioned positive electrode lithium replenisher, which may include the following steps: mixing a positive electrode lithium replenisher precursor with a lithium source and then performing a first sintering.

[0110] Among them, the molar ratio of the metal element in the positive electrode 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., or it can be any other value within the range of (1:2)-(1:2.5).

[0111] The lithium source may illustratively but not limitatively include at least one of lithium hydroxide, lithium carbonate, lithium oxide, lithium oxalate, and lithium nitrate.

[0112] For reference, the temperature of the first sintering can be 450℃-650℃, such as 450℃, 480℃, 500℃, 520℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃ or 650℃, etc., or it can be any other value within the range of 450℃-650℃.

[0113] The first sintering time may be 10 h to 20 h, such as 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h or 20 h, or any other value within the range of 10 h to 20 h.

[0114] It should be noted that during the current preparation of lithium-supplementing agents for cathode materials, the precursor and lithium source typically require a long-term, high-temperature, solid-phase sintering process at 750°C-850°C for 10-15 hours. However, the present invention, by employing a specific lithium-supplementing agent precursor, effectively reduces the sintering temperature of the precursor and lithium source. This not only facilitates industrial production but also improves the purity of the lithium-supplementing agent and avoids the formation of impurities.

[0115] The first sintering can be performed in an inert atmosphere, and the gas used can be at least one of nitrogen, argon, helium and neon.

[0116] Furthermore, the first sintered material obtained by the first sintering is crushed, then mixed with a carbon source, and sintered for a second time.

[0117] As a reference, the D of the first sintered material after crushing 50 Can be 1.0μm-5.0μm, D 99 It can be 10μm-20μm.

[0118] In some optional embodiments, the carbon source is an organic carbon source, such as at least one of phenolic resin, epoxy resin, glucose, sucrose, polyaniline, polypyrrole, polyacetylene, polythiophene and polydopamine.

[0119] In the present disclosure, the second sintering may be dynamic low-temperature sintering, and the process may be performed in a rotary kiln.

[0120] For reference, the temperature of the second sintering can be 100℃-500℃, such as 100℃, 120℃, 150℃, 180℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃ or 500℃, etc., or any other value within the range of 100℃-500℃.

[0121] The second sintering time can be 4h-15h, such as 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h, or any other value within the range of 4h-15h.

[0122] The second sintering can also be performed in an inert atmosphere, and the gas used can be at least one of nitrogen, argon, helium and neon.

[0123] The rotation speed of the rotary kiln can be 1 rpm-3 rpm. By adopting a dynamic sintering method, it is beneficial to ensure that the molten carbon source is fully in contact with the crushed material.

[0124] The present disclosure forms a dense nano-coated carbon layer on the surface of the first sintered material by mixing a crushed first sintered material with an organic carbon source under an inert atmosphere and performing dynamic solid-phase high-temperature sintering in a rotary kiln. Under the aforementioned conditions, the present disclosure achieves a superior coating effect, and the thickness of the coating layer is controllable, further improving the material's stability and electrical conductivity.

[0125] 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 is adsorbed on the core material and can react with the lithium source at low temperatures to generate a lithium-containing metal oxide coated on the surface of the core material. This promotes the reaction between the lithium source and Ni(OH)2 to form a good solid solution, thereby reducing the sintering temperature and facilitating the production of a high-purity lithium supplement material. Further carbon coating provides a good protective barrier for the material, preventing direct contact with moisture and carbon dioxide in the air, thereby improving the material's stability. Furthermore, the carbon coating can also provide electrical conductivity to the lithium supplement.

[0126] In addition, the present disclosure also provides applications of the above-mentioned positive electrode lithium supplement agent, for example, it can be used to prepare lithium-ion batteries.

[0127] Accordingly, the present disclosure also provides a lithium-ion battery, the raw materials of which include the above-mentioned positive electrode lithium supplement, and the lithium-ion battery can have a high charging capacity and a high initial charging efficiency.

[0128] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0129] Example 1

[0130] This embodiment prepares a positive electrode lithium supplement agent with a chemical formula of Li2NiO2@C, which includes 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 is 1:100, and the particle size of the primary particles is D 50 ≤10μm.

[0131] The preparation process of the positive electrode lithium supplement comprises:

[0132] Step (1): Add commercial NiCl2·6H2O into deionized water, and obtain a nickel salt solution by stirring and ultrasonic dispersion.

[0133] Step (2): Add ammonia water (concentration of 10%) to the nickel salt solution. 2+ The molar ratio of the reaction mixture is 5:1, stirring and ultrasonic dispersion are maintained during the addition of ammonia water, and the pH value of the solution is maintained at 7.5-8.5. After aging in the container for 4 hours, the core material Ni(OH)2 is obtained by filtration, washing and drying.

[0134] The core material Ni(OH)2 50 The surface area is 2.0 μm and the specific surface area is 48 m 2 / g, and the porosity is 39%.

[0135] Step (3): Add the core material Ni(OH)2 and CuO obtained above into water to obtain a mixed solution. The mass ratio of CuO to the core material Ni(OH)2 is 2:100.

[0136] Step (4): placing the mixed solution of step (3) in a high-pressure reactor and reacting it at 120° C. and 10 MPa for 10 h. After the reaction is completed, dehydrating, washing, and drying are performed to obtain a positive electrode lithium supplement precursor.

[0137] In the positive electrode lithium supplement agent precursor, the shell material has a thickness of 60nm. 50 The surface area is 2.2 μm and the specific surface area is 31 m 2 / g.

[0138] Step (5): The positive electrode lithium supplement precursor is mixed with a 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.

[0139] Step (6): The mixture obtained in step (5) is subjected to a solid phase reaction under a nitrogen atmosphere. Specifically, the temperature is raised to 450°C at a heating rate of 2°C / min and kept for 4 hours, and then the temperature is raised to 600°C at a heating rate of 2°C / min and kept for 10 hours, and then naturally cooled to room temperature with the furnace temperature to obtain a first sintered material; the first sintered material is crushed by a jet mill to obtain a first crushed material. The D of the first crushed material is 50 5μm, D 99 It is 19μm.

[0140] Step (7): The phenolic resin and the first crushed material are mixed uniformly with a high-speed mixer to obtain a mixed material. The amount of the phenolic resin added is 1 wt% of the first crushed material.

[0141] Step (8): The mixed material obtained in step (7) is subjected to a dynamic high-temperature sintering reaction in a rotary kiln under a nitrogen atmosphere. Specifically, the rotation rate of the rotary kiln is set to 1rpm, and the temperature is raised to 100°C at a heating rate of 1°C / min and kept warm for 5 hours. This process can ensure that the molten carbon source is in full contact with the primary crushed material, and then the temperature is raised to 350°C at a heating rate of 1°C / min and kept warm for 5 hours to allow the phenolic resin to be completely carbonized. After the sintering reaction, the mixture is naturally cooled to room temperature with the furnace temperature to obtain a second sintered material. The second sintered material is crushed with a mechanical mill to obtain the final positive electrode lithium supplement. The D of the positive electrode lithium supplement50 9μm.

[0142] The SEM of the core material Ni(OH)2 obtained in step (2) of this embodiment is shown in FIG1 . As can be seen from the figure, the obtained core material Ni(OH)2 has a flower-like morphology.

[0143] The SEM of the positive electrode lithium supplement precursor obtained in step (4) of this embodiment is shown in Figure 2, and the structural schematic is shown in Figure 3. As can be seen from Figure 2, after the core material Ni(OH)2 is coated, the flower-like morphology of the material is filled with CuO.

[0144] The SEM of the positive electrode lithium supplement obtained in step (8) of this embodiment is shown in FIG4 . As can be seen from FIG4 , the material appears as particles with regular morphology, and the sample surface is clean and smooth.

[0145] Example 2

[0146] This embodiment provides a positive electrode lithium supplement, the preparation method of which includes:

[0147] Step (1) and step (2) are the same as in Example 1.

[0148] Step (3): Add the core material Ni(OH)2 and CuSO4·5H2O obtained in step (2) to deionized water to obtain a mixed solution. The mass ratio of CuSO4·5H2O to the core material Ni(OH)2 is 5:100.

[0149] Step (4): Add 10% sodium hydroxide solution to the mixed solution obtained in step (3). 2+ The molar ratio of 2.2:1 was maintained, and stirring and ultrasonic dispersion were maintained during the addition of sodium hydroxide solution, and the pH value of the solution was maintained at 7.5-8.5. The reaction was carried out for 4 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a positive electrode lithium supplement precursor.

[0150] In the positive electrode lithium supplement agent precursor, the shell material has a thickness of 65nm. 50 The surface area is 2.2 μm and the specific surface area is 30 m 2 / g.

[0151] Step (5): The positive electrode lithium supplement precursor is mixed with a 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.

[0152] Step (6) is the same as in Example 1.

[0153] Step (7): Glucose and the first crushed material are mixed uniformly with a high-speed mixer to obtain a mixed material. The amount of glucose added is 1 wt% of the first crushed material.

[0154] Step (8): Same as Example 1.

[0155] Example 3

[0156] This embodiment provides a positive electrode lithium supplement, the preparation method of which includes:

[0157] Step (1): adding commercial NiSO4·7H2O into deionized water, and obtaining a nickel salt solution by stirring and ultrasonic dispersion.

[0158] Step (2): Add ammonia water (concentration of 10%) to the nickel salt solution. 2+ The molar ratio of the reaction mixture is 4:1, stirring and ultrasonic dispersion are maintained during the addition of ammonia water, and the pH value of the solution is maintained at 10.5-11. The mixture is then aged in a container for 4 hours, and then filtered, washed, and dried to obtain the core material Ni(OH)2.

[0159] The core material Ni(OH)2 50 The surface area is 1.5 nm and the specific surface area is 56 m 2 / g, and the porosity is 45%.

[0160] Step (3): Add the core material Ni(OH)2 and MgO obtained above to water to obtain a mixed solution. The mass ratio of MgO to the core material Ni(OH)2 is 2:100.

[0161] Step (4): placing the mixed solution of step (3) in a high-pressure reactor and reacting it at 120° C. and 10 MPa for 10 h. After the reaction is completed, dehydrating, washing, and drying are performed to obtain a positive electrode lithium supplement precursor.

[0162] In the positive electrode lithium supplement agent precursor, the shell material has a thickness of 60nm. 50 The surface area is 1.6 μm and the specific surface area is 34 m 2 / g.

[0163] Step (5): The positive electrode lithium supplement precursor is mixed with a 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.

[0164] Step (6): Same as Example 1.

[0165] Step (7): Glucose and the first crushed material are mixed uniformly with a high-speed mixer to obtain a mixed material. The amount of glucose added is 1 wt% of the first crushed material.

[0166] Step (8): Same as Example 1.

[0167] Example 4

[0168] This embodiment prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0169] In step (3), the metal oxide is TiO2; in step (5), the molar ratio of lithium hydroxide to lithium oxide in the mixed lithium salt is 4:3.

[0170] Example 5

[0171] This embodiment prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0172] In step (7), the organic carbon source is replaced by glucose instead of phenolic resin.

[0173] Example 6

[0174] This embodiment prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 2 in that:

[0175] In step (3), MgSO4·H2O is used instead of CuSO4·5H2O.

[0176] Example 7

[0177] This embodiment prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0178] In step (2), the D of the core material Ni(OH)2 50 The surface area is 3.0 μm and the specific surface area is 40 m 2 / g, porosity is 30%.

[0179] In step (4), the cathode lithium supplement precursor D 50 The surface area is 3.1 μm and the specific surface area is 30 m 2 / g.

[0180] Example 8

[0181] This embodiment prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0182] In step (2), the D of the core material Ni(OH)2 50 The surface area is 1 μm and the specific surface area is 56 m 2 / g, and the porosity is 55%.

[0183] In step (4), the cathode lithium supplement precursor D 50The surface area is 1.1 μm and the specific surface area is 30 m 2 / g.

[0184] Example 9

[0185] This embodiment prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0186] In step (3), the mass ratio of CuO to the core material Ni(OH)2 is 5:100.

[0187] In step (4), the thickness of the shell material in the positive electrode lithium supplement agent precursor is 250nm. 50 The surface area is 2.5 μm and the specific surface area is 30 m 2 / g.

[0188] Example 10

[0189] This embodiment prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0190] In step (6), the mixture obtained in step (5) is subjected to a solid phase reaction under a nitrogen atmosphere. Specifically, the temperature is increased to 450°C at a heating rate of 2°C / min and kept for 4 hours, and then increased to 650°C at a heating rate of 2°C / min and kept for 10 hours, and then naturally cooled to room temperature with the furnace temperature to obtain a first sintered material; the first sintered material is crushed by a jet mill to obtain a first crushed material. The D of the first crushed material is 50 5μm, D 99 It is 19μm.

[0191] Comparative Example 1

[0192] This comparative example provides a positive electrode lithium replenisher, which directly uses commercially available Ni(OH)2 as a positive electrode lithium replenisher precursor to carry out steps (5) to (8) in Example 1.

[0193] The SEM of commercially available Ni(OH)2 in this comparative example is shown in FIG5 .

[0194] The SEM image of the positive electrode lithium supplement agent obtained in this comparative example is shown in FIG6 .

[0195] It can be seen from Figures 5 and 6 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, it has lower reaction activity and does not have an external shell material as a catalyst. Therefore, its reaction with the lithium source at 600°C (lower than 650°C) is relatively incomplete, and a large amount of residual nickel oxide is left, resulting in a relatively poor reaction effect.

[0196] The self-prepared Ni(OH)2 precursor with a core-shell structure provided in Example 1 of the present disclosure has a shell material that can form a lithium-containing metal oxide with a lithium source at low temperature, and the formed lithium-containing metal oxide can act as a catalyst, prompting the lithium source to continue to react with the internal core material, thereby reducing the energy barrier of the reaction, and ultimately allowing the entire reaction to proceed at 600°C.

[0197] Comparative Example 2

[0198] This comparative example provides a positive electrode lithium supplement agent, which differs from comparative example 1 in that: a mixture of commercially available Ni(OH)2 and a mixed lithium salt is subjected to a high-temperature solid-phase reaction under a nitrogen atmosphere, and the temperature is increased to 450°C at a heating rate of 2°C / min and kept warm for 4 hours, and then the temperature is increased to 750°C at a heating rate of 2°C / min, kept warm for 10 hours, and then naturally cooled to room temperature with the furnace temperature to obtain a first sintered material.

[0199] The rest of the operations and conditions are the same.

[0200] Comparative Example 3

[0201] This comparative example provides a positive electrode lithium supplement, the chemical formula of which is Li2NiO2 and which has no carbon coating layer.

[0202] The preparation process of the positive electrode lithium supplement differs from that of Example 1 in that the steps related to carbon coating (step (7) and step (8)) are absent.

[0203] Comparative Example 4

[0204] This comparative example provides a positive electrode lithium supplement, the chemical formula of which is Li2NiO2 and which has no carbon coating layer.

[0205] The preparation process of the positive electrode lithium supplement agent differs from that of Comparative Example 1 in that there is no carbon coating step.

[0206] Comparative Example 5

[0207] This comparative example prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0208] In step (3), the mass ratio of CuO to the core material Ni(OH)2 is 10:100.

[0209] In step (4), the thickness of the shell material in the positive electrode lithium supplement precursor is 500nm. 50 The surface area is 4 μm and the specific surface area is 20 m 2 / g.

[0210] Comparative Example 6

[0211] This comparative example prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0212] In step (4), the mixed solution of step (3) is placed in a high-pressure reactor and reacted at 250° C. and 20 MPa for 15 hours. After the reaction is completed, the mixture is dehydrated, washed, and dried to obtain a positive electrode lithium supplement precursor.

[0213] In the positive electrode lithium supplement agent precursor, the shell material has a thickness of 500nm. 50 The surface area is 3 μm and the specific surface area is 20 m 2 / g.

[0214] Comparative Example 7

[0215] This comparative example prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0216] In step (6), the first sintered material is crushed by a jet mill to obtain a first crushed material. The D 50 15μm, D 99 25μm.

[0217] In step (8), the second sintered material is crushed by a mechanical mill to obtain the final positive electrode lithium supplement. The D 50 It is 16μm.

[0218] Comparative Example 8

[0219] This comparative example prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0220] In step (7), the phenolic resin and the first crushed material are mixed uniformly with a high-speed mixer to obtain a mixed material. The amount of the phenolic resin added is 10 wt% of the first crushed material.

[0221] Comparative Example 9

[0222] This comparative example prepares a positive electrode lithium supplement, and its preparation method differs from that of Example 1 in that:

[0223] 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, the temperature is raised to 100°C at a heating rate of 1°C / min and kept warm for 5 hours, and then the temperature is raised to 350°C at a heating rate of 1°C / min and kept warm for 5 hours to allow the phenolic resin to be completely carbonized. After the sintering reaction, the mixture is naturally cooled to room temperature with the furnace temperature to obtain a second sintered material. The second sintered material is crushed with a mechanical mill to obtain the final positive electrode lithium supplement. The D of the positive electrode lithium supplement 50 9μm.

[0224] In this comparative example, the positive electrode lithium supplement agent adopts a static coating method, and the moisture absorption rate of the final material is higher than that of the dynamic coated material, but lower than that of the uncoated material, which further proves that dynamic carbon coating can improve the coating uniformity of the material and thus improve the air stability of the material.

[0225] Test example

[0226] (1) Structural comparison

[0227] The positive electrode lithium supplement agents of Example 1, Comparative Example 1 and Comparative Example 2 were characterized by XRD, and the results are shown in FIG7 .

[0228] As can be seen from Figure 7: in the XRD results corresponding to Comparative Example 2, the peak intensity of nickel oxide is lower than that of 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 homemade Ni(OH)2 precursor provided in Example 1 of the present disclosure by reacting at high temperature (750°C).

[0229] (2) Electrochemical performance

[0230] The positive electrode lithium supplement provided in Examples 1-10 and Comparative Examples 1-9 were respectively prepared into button batteries according to the following methods:

[0231] ① Prepare slurry: weigh 3.6g of positive electrode lithium replenisher and conductive agent, mix with binder, the mass ratio of positive electrode lithium replenisher, conductive agent and binder is 90:5:5, the binder used is PVDF, and the conductive agent is conductive carbon;

[0232] ②Coating: Use a scraper to coat on the aluminum foil;

[0233] ③ Drying: Dry the coated electrode in a vacuum drying oven at a temperature of 110°C for 2 hours;

[0234] ④ Tablet pressing: Use a roller machine to press the dried electrode into tablets;

[0235] ⑤ Assemble the battery parts such as the positive electrode sheet, the negative electrode sheet (lithium metal sheet with a diameter of 16 mm), the diaphragm (polypropylene microporous diaphragm) and the 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 battery.

[0236] The charging capacity and initial efficiency of the obtained button battery were tested 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 FIG8 .

[0237] Table 1 Test results

[0238] It can be seen from Table 1 and Figure 8 that the batteries obtained from the homemade Ni(OH)2 precursor provided in Examples 1 and 2 of the present disclosure are better than the batteries obtained from commercially available Ni(OH)2 in terms of charging capacity and first charging efficiency.

[0239] In combination with Example 1, Example 2, Comparative Example 1 and Comparative Example 2, it is shown that the commercially available Ni(OH)2 precursor can only approach the effect of low-temperature sintering of the homemade Ni(OH)2 precursor with a core-shell structure in Example 1 with a lithium source by reacting with the lithium source at a high temperature (750°C), further proving 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] The positive electrode lithium supplements provided in Example 1, Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 9 were subjected to moisture absorption experiments to characterize the air stability of different carbon coating materials.

[0242] The specific steps are as follows: ① Weigh 5 g of each of the lithium-ion battery positive electrode pre-lithiation agent materials of Example 1, Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 9, and place them in a culture dish with a diameter of 90 mm; ② Place them in a constant temperature and humidity chamber, adjust the temperature to 25°C, and adjust the humidity to 30%; ③ Place them in the constant temperature and humidity chamber for 2 hours, during which the material mass is recorded every 30 minutes; ④ Calculate the moisture absorption rate of each material and compare them. The moisture absorption rate curve is shown in Figure 9.

[0243] It can be seen from Figure 9 that the moisture absorption rate of the carbon-coated positive electrode lithium replenishing material is lower than that of the non-carbon-coated lithium replenishing material, and the moisture absorption rate of the dynamic coated material is lower than that of the static coated material, which also shows that carbon coating can improve the stability of the material.

[0244] In summary, the cathode lithium supplement precursor provided by the present disclosure has a core-shell structure, a solid solution can be formed between the core and the shell, and the shell material can form a lithium-containing metal oxide with the lithium source at low temperatures. The formed lithium-containing metal oxide can act as a catalyst, prompting the lithium source to continue to react with the internal core material, reducing the energy barrier of the reaction, and ultimately allowing the sintering reaction between the precursor and the lithium source to proceed at a lower temperature (e.g., not exceeding 650°C). The lithium supplement material further prepared from the precursor has high purity and good stability, which is conducive to the preparation of lithium-ion batteries with excellent charging capacity and first charge efficiency. Industrial Applicability

[0245] The specific positive electrode lithium supplement precursor provided by the present disclosure can be sintered with a lithium source at relatively low temperatures to produce a high-purity lithium supplement material, which helps reduce production costs and energy consumption and is suitable for industrial production. The carbon-coated lithium supplement material provided by the present disclosure exhibits excellent stability and electrochemical performance, facilitating the preparation of lithium-ion batteries with excellent charge capacity and initial 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.

2. The precursor of the cathode lithium supplement agent according to claim 1, characterized in that, 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; Feature Five: The nuclear material is a porous spherical material composed of Ni(OH) 2 nanosheets.

3. The precursor of the 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 any one of claims 1-4, 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 the precursor of the cathode lithium supplement agent according to any one of claims 1-5, characterized in that, comprises the following steps: Prepare the shell material on the surface of the core material.

7. The preparation method according to claim 6, characterized in that, The preparation of the nuclear material includes: mixing a nickel salt solution with a first precipitating agent to carry out a precipitation reaction and form Ni(OH) 2 .

8. The preparation method according to claim 7, characterized in that, 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 precipitating agent includes at least one of urea solution, ammonia water and sodium hydroxide solution.

10. The preparation method according to any one of claims 7-9, characterized in that, The concentration of the first precipitating agent is 10wt%-25wt%, and the molar ratio of the first precipitating agent to the nickel element in the nickel salt solution is (2.0:1)-(5.0:1).

11. The preparation method according to any one of claims 7-9, 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 any one of claims 6-11, characterized in that, 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.

13. The preparation method according to claim 12, 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.

14. 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 precipitating agent for a coprecipitation reaction to form a shell material on the surface of the core material.

15. The preparation method according to claim 14, 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 10wt%-25wt%, 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).

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

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

18. The cathode lithium supplement agent according to claim 17, characterized in that, The positive electrode lithium supplement includes primary particles containing Li formed by the reaction of the positive electrode lithium supplement precursor and a lithium source 2 NiO 2 , and a carbon coating layer coated on the surface of the primary particles.

19. The cathode lithium supplement agent according to claim 18, 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).

20. A preparation method of a cathode lithium supplement agent according to any one of claims 17-19, characterized in that, comprises the following steps: Mix the precursor of the cathode lithium supplement agent with a lithium source and then perform the first sintering.

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

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

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

24. The preparation method according to any one of claims 20-23, characterized in that, further includes: Crush the first sintered material obtained from the first sintering, then mix it with a carbon source and perform the second sintering.

25. The preparation method according to claim 24, characterized in that, 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.

26. The preparation method according to claim 24, characterized in that, the carbon source is an organic carbon source.

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

28. The preparation method according to any one of claims 24-27, characterized in that, the second sintering includes at least one of the following characteristics: Characteristic 1: The temperature of the second sintering is 100°C-500°C; Characteristic 2: The time of the second sintering is 4h-15h; Characteristic 3: The second sintering is carried out in an inert atmosphere; Characteristic 4: The second sintering is dynamic sintering.

29. An application of a cathode lithium supplement agent according to any one of claims 17-19, characterized in that, the cathode lithium supplement agent is used to prepare a lithium-ion battery.

30. A lithium-ion battery, characterized in that, The preparation raw materials of the lithium-ion battery include the cathode lithium supplement agent described in any one of claims 17-19.

Images