Nickel-rich positive electrode material, preparation method and application thereof

Abstract

The application relates to the technical field of lithium ion battery positive electrode materials, in particular to a nickel-rich positive electrode material and a preparation method and application thereof. The preparation method is as follows: in a vacuum and high-temperature environment, a mixed solvent composed of acid, an organic solvent and an aqueous solution has a low boiling point, can be quickly self-evaporated, metal cation M1, metal cation M2, lithium ions, nickel ions and anions in the mixed solution are quickly precipitated, an atomically mixed uniform metal salt, nickel salt and lithium salt mixture is obtained, then high-performance nickel-rich positive electrode material with high crystallinity, small lithium-nickel mixing degree and accurate stoichiometric ratio is obtained through solid-phase sintering; the preparation method is simple, atomically mixed material can be realized, no element is lost in the whole synthesis process, the atomic utilization rate is high, the stoichiometric ratio is accurately controlled, and the method is suitable for wide application.

Description

Nickel-rich cathode materials, their preparation methods and applications Technical Field

[0001] This application belongs to the field of lithium-ion battery cathode material technology, and particularly relates to a nickel-rich cathode material, its preparation method and application. Background Technology

[0002] With the ongoing impact of energy shortages, the development of new energy technologies has become a focal point, with lithium-ion batteries serving as the core of this development. A lithium-ion battery consists of a positive electrode material, a negative electrode material, a separator, and an electrolyte. The positive electrode material, as the key material in a lithium-ion battery, is a crucial factor affecting battery performance.

[0003] Among the cathode materials for lithium-ion batteries, nickel-rich materials have attracted much attention due to their high discharge capacity, high operating voltage, and good industrialization foundation, and are considered ideal cathode materials for next-generation high-energy-density lithium-ion batteries. However, nickel-rich cathode materials also have some drawbacks, such as severe cation mixing, easy phase transition during charge and discharge, intense interfacial side reactions, and lattice oxygen release, resulting in poor cycle performance and low safety performance.

[0004] Currently, elemental doping and surface coating are the most effective and commonly used methods to improve the structure and interface of nickel-rich materials. For example, Ye Shewen et al. used elements with large ionic radii as dopants to carry out elemental doping during the mixing process of precursor and Li source to construct a surface doped layer, thereby improving the material interface stability (CN115548333 A). Sun Guozheng et al. used highly stable elements such as Mn, Al, and Ta as dopants and added additives during the mixing process of nickel-rich precursor and lithium source to successfully prepare element-doped modified nickel-rich cathode materials. This material can reduce the extraction of internal lithium when residual alkali is washed away from the surface, improve the stability of the crystal structure, and the doped material has better cycle life, lower DCR, and less gas production (CN115536077 A).

[0005] For elemental doping modification of nickel-rich materials, there are two main methods: one involves adding a dopant during high-speed mixing of the nickel-rich precursor and lithium source, followed by high-temperature solid-state sintering; the other involves doping the precursor during co-precipitation. While both methods achieve good modification results, they also have some drawbacks. For example, doping during the mixing of the nickel-rich precursor and lithium source requires a high dopant particle size, generally not exceeding 200 nm; while doping during precursor preparation requires the dopant element to precipitate in an alkaline environment, and the precipitation coefficient cannot differ too much from the main element. Furthermore, both methods struggle to achieve atomically uniform doping distribution.

[0006] Given that current preparation methods all have certain shortcomings, there is an urgent need for a new method for preparing nickel-rich materials for industrial production. Summary of the Invention

[0007] The purpose of this application is to provide a nickel-rich cathode material, its preparation method and application, aiming to solve the problem that the metal elements cannot be uniformly doped at the atomic level in the preparation process of nickel-rich cathode materials in the prior art.

[0008] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0009] In a first aspect, this application provides a method for preparing a nickel-rich cathode material, comprising the following steps:

[0010] According to the chemical formula LiNi x M1 y M2 z O2 provides a certain molar amount of lithium salt, nickel salt, M1 metal salt and M2 metal salt as raw materials, wherein M1 and M2 are selected from different transition metals, 0.8≤x<1, 0<7<0.2, 0<z<0.2, x+y+z=1;

[0011] After mixing the raw materials, acid solution and organic solvent, the mixture is subjected to rotary evaporation under vacuum to obtain a precursor material with atomically homogeneous mixing.

[0012] The precursor material is ground and then subjected to solid-state sintering to obtain a nickel-rich cathode material.

[0013] Secondly, this application provides a nickel-rich cathode material, which is prepared by the above-mentioned method for preparing nickel-rich cathode materials.

[0014] Thirdly, this application provides a lithium-ion battery positive electrode, which includes a positive electrode material, a conductive agent, and a binder, wherein the positive electrode material is selected from the aforementioned nickel-rich positive electrode material.

[0015] Fourthly, this application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is selected from the above-mentioned lithium-ion battery positive electrode.

[0016] The method for preparing nickel-rich cathode material provided in the first aspect of this application firstly obtains a mixed solution of lithium salt, nickel salt, M1 metal salt, and M2 metal salt in an acidic solution using a liquid-phase dissolution method. Then, taking advantage of the low boiling point property of the acid-low-boiling-point organic solvent-aqueous solution system under vacuum and high temperature, the solvent is rapidly evaporated, allowing metal cations and anions to precipitate simultaneously and rapidly. This ensures that the lithium salt, nickel salt, and metal salt in the obtained precursor material achieve an atomically homogeneous mixture, avoiding uneven material mixing caused by ions precipitating at different rates due to different crystallinity. Furthermore, a solid-state sintering treatment is used to form a nickel-rich cathode material with high crystallinity, intact layered structure, low cation mixing degree, and precise stoichiometry. This preparation method achieves a one-step atomically homogeneous mixture of metal salt and lithium salt, with no atomic loss and 100% atomic utilization. It enables precise control of the stoichiometry, has a simple preparation process, and provides mild and controllable reaction conditions, making it suitable for widespread application in industrial production.

[0017] The nickel-rich cathode material provided in the second aspect of this application is obtained by using the preparation method of nickel-rich cathode material described above. Based on the preparation method of nickel-rich cathode material, it is possible to ensure that the metal salt and lithium salt in the material can reach a state of atomic-level uniform mixing. Therefore, the obtained nickel-rich cathode material has high crystallinity and intact layered structure, which can significantly improve the structural stability of the material during charge and discharge, reduce uneven stress distribution and reduce the generation of microcracks; low cation mixing is conducive to increasing the amount of active lithium in the cathode material and ensuring the integrity of lithium ion diffusion channels; the precise stoichiometry can effectively avoid the generation of nickel-rich materials with non-stoichiometric ratios, which is conducive to obtaining nickel-rich cathode materials with excellent properties and wide application range.

[0018] The lithium-ion battery cathode provided in the third aspect of this application uses a nickel-rich cathode material as the cathode material, which can increase the amount of active lithium in the lithium-ion battery cathode and improve the cycle performance and structural stability of the battery.

[0019] The lithium-ion battery provided in the fourth aspect of this application has excellent cycle performance, high specific capacity, high capacity retention, and strong structural stability because it uses a cathode containing nickel-rich cathode material as the cathode, which is conducive to its widespread use. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 is the XRD pattern of the samples prepared in Examples 1-4 of this application.

[0022] Figure 2 is a SEM image of the samples prepared in Examples 1-2 and Comparative Examples 1-2 of this application.

[0023] Figure 3 is a TEM image of the NCM90 sample prepared in Example 1 of this application.

[0024] Figure 4 is a TEM image of sample SZ-NCM93 prepared in Example 3 of this application.

[0025] Figure 5 is the XRD pattern of the samples prepared in Comparative Examples 1-3 of this application.

[0026] Figure 6 is a TEM image of the sample prepared in Comparative Example 1 of this application. Detailed Implementation

[0027] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0028] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0029] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0030] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0031] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0032] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as μg, mg, g, or kg.

[0033] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0034] Currently, the industrial production of nickel-rich materials requires first converting metal salts into mixed hydroxide precipitates, then mixing them with lithium salts to obtain a mixture, followed by solid-state sintering to obtain the desired material. This method is not only complex, but also prone to metal atom loss during co-precipitation, resulting in the formation of non-stoichiometric nickel-rich materials. Furthermore, elemental doping during the hydroxide and lithium salt process is difficult to achieve uniform mixing, and the resulting doped material cannot achieve true atomic-level uniform doping.

[0035] The first aspect of this application provides a method for preparing a nickel-rich cathode material, comprising the following steps:

[0036] S01. Based on the chemical formula LiNi x M1 y M2 z O2 provides a certain molar amount of lithium salt, nickel salt, M1 metal salt and M2 metal salt as raw materials, wherein M1 and M2 are selected from different transition metals, 0.8≤x<1, 0<y<0.2, 0<z<0.2, x+y+z=1;

[0037] S02. After mixing the raw materials, acid solution and organic solvent, rotary evaporation is carried out under vacuum to obtain a precursor material with atomically homogeneous mixture;

[0038] S03. After grinding the precursor material, solid-state sintering is performed to obtain nickel-rich cathode material.

[0039] The method for preparing nickel-rich cathode material provided in the first aspect of this application firstly obtains a mixed solution of lithium salt, nickel salt, M1 metal salt, and M2 metal salt in an acidic solution using a liquid-phase dissolution method. Then, taking advantage of the low boiling point property of the acid-low-boiling-point organic solvent-aqueous solution system under vacuum and high temperature, the solvent is rapidly evaporated, allowing metal cations and anions to precipitate simultaneously and rapidly. This ensures that the lithium salt, nickel salt, and metal salt in the obtained precursor material can achieve an atomically homogeneous mixture, avoiding uneven material mixing caused by ions precipitating at different rates due to different crystallinity. Furthermore, a solid-state sintering treatment is used to form a nickel-rich cathode material with high crystallinity, intact layered structure, low cation mixing degree, and precise stoichiometry. This preparation method achieves a one-step atomically homogeneous mixture of metal salt and lithium salt, with no atomic loss throughout the process, 100% atomic utilization, precise control of stoichiometry, simple preparation process, mild and controllable reaction conditions, and is conducive to widespread application in industrial production.

[0040] In step S01, according to the chemical formula LiNi x M1 y M2 z O2 provides a certain molar amount of lithium salt, nickel salt, M1 metal salt and M2 metal salt as raw materials, wherein M1 and M2 are selected from different transition metals, 0.8≤x<1, 0<y<0.2, 0<z<0.2, x+y+z=1.

[0041] In some embodiments, the lithium salt is selected from at least one of lithium sulfate, lithium nitrate, lithium hydroxide, lithium carbonate, lithium oxide, lithium chloride, and lithium oxalate.

[0042] In some embodiments, the nickel salt is selected from at least one of nickel sulfate, nickel nitrate, and nickel chloride.

[0043] In some embodiments, the M1 metal salt and the M2 metal salt are independently selected from at least one of soluble metal sulfates, soluble metal nitrates, and soluble metal chlorides.

[0044] In some embodiments, M1 and M2 are each selected from any one of Mn, Co, Mg, Zr, Ti, Nb, and Sr.

[0045] In some specific embodiments, when the metal is Mn, the provided metal salt is selected from at least one of manganese sulfate and manganese acetate. When the metal is Co, the provided metal salt is selected from at least one of cobalt sulfate, cobalt nitrate, and cobalt chloride. When the metal is Mg, the provided metal salt is selected from at least one of magnesium sulfate, magnesium nitrate, and magnesium chloride. When the metal is Zr, the provided metal is selected from at least one of zirconium sulfate, zirconium nitrate, and zirconium chloride. When the metal is Ti, the provided metal is selected from at least one of titanium nitrate and titanium chloride. When the metal is Nb, the provided metal is selected from at least one of niobium sulfate and niobium chloride. When the metal is Sr, the provided metal is selected from at least one of strontium nitrate and strontium chloride.

[0046] In step S02, the raw materials, acid solution, and organic solvent are mixed and then subjected to rotary evaporation under vacuum to obtain a precursor material with atomically homogeneous mixing. In this step, by adding acid solution and organic solvent, a mixed system of acid environment, low-boiling-point organic solvent, and aqueous solution is formed. Starting from the metal salt raw materials, a rotary evaporation liquid-phase method is used to achieve a one-step process by constructing a low-boiling-point mixed liquid co-evaporation technique to obtain a material with atomically homogeneous mixing of metal salt and lithium salt. This avoids uneven mixing caused by ions precipitating at different rates due to differences in crystallinity of the mixed salts. Furthermore, the resulting atomically homogeneous precursor material forms a nickel-rich cathode material with high crystallinity, intact layered structure, low cation mixing degree, and precise stoichiometry during subsequent sintering.

[0047] In some embodiments, the step of mixing the raw material, acid solution, and organic solvent includes: mixing the raw material with water, heating and rapidly stirring, then sequentially adding the acid solution and organic solvent and rapidly stirring until dissolved to obtain a mixed solution. Heating and stirring during the mixing process promotes complete dissolution of each metal salt.

[0048] The raw material to water mass ratio is 1:1 to 10, and the amount of water added is controlled appropriately to ensure that the mixture of lithium salt, nickel salt and metal salt can be completely dissolved. In some specific implementations, the raw material to water mass ratio includes, but is not limited to, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 and 10:1.

[0049] Furthermore, to improve the solubility of each raw material, heating and stirring are performed during the mixing process to rapidly dissolve the metal salts in water. In some embodiments, the heating temperature is 50–80°C. If the heating temperature is too low, it will not effectively dissolve the metal salts; if the heating temperature is too high, it will affect the properties of the material. In some specific embodiments, the heating temperature is 60–70°C. In specific experiments, the heating temperature includes, but is not limited to, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, and 70°C.

[0050] Furthermore, acid solution and organic solvent are added sequentially and stirred rapidly until dissolved. By providing acid solution and organic solvent, the low-boiling-point properties of the acid-low-boiling-point organic liquid-aqueous solution system under vacuum and high temperature are constructed. Rapid evaporation of the solvent allows for the simultaneous and rapid precipitation of metal cations and anions, enabling the uniform mixing of metal salts, nickel salts, and lithium salts at the atomic level.

[0051] In some embodiments, the acid solution is also selected from at least one of nitric acid solution and hydrochloric acid solution. In some specific embodiments, the acid solution is selected from nitric acid solution or hydrochloric acid solution with a molar concentration of 0.8 to 1 mol / L.

[0052] In some embodiments, the volume ratio of the acid solution added to the total volume of the mixed solution is 1:20 to 1:10. In some specific embodiments, the volume ratio of the acid solution added to the total volume of the mixed solution includes, but is not limited to, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, and 1:20.

[0053] In some embodiments, the organic solvent is selected from at least one of dichloromethane, chloroform, and ethyl acetate. Providing an organic solvent can effectively lower the boiling point of the system, allowing cations and anions to precipitate simultaneously and mix at the atomic level.

[0054] In some embodiments, the volume ratio of the added organic solvent to the total volume of the mixed solution is 1:10 to 1:2. In some specific embodiments, the volume ratio of the added organic solvent to the total volume of the mixed solution includes, but is not limited to, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, and 1:10.

[0055] In some embodiments, the mass ratio of raw materials to water is 1:2 to 5. In some specific embodiments, the mass ratio of raw materials to water includes, but is not limited to, 1:2, 1:3, 1:4, and 1:5.

[0056] In some embodiments, the rapid stirring rate is 300 rad / min. -1 ~800 rad min -1 Rapid stirring accelerates the evaporation rate, allowing for faster and more efficient evaporation of the liquid in the mixture. This enables the simultaneous precipitation of cations and anions during liquid evaporation, resulting in atomically homogeneous precursor materials. In specific embodiments, the rapid stirring rate includes, but is not limited to, 300 rad / min. -1 350 rad min -1 400 rad min -1 450 rad min-1 500 rad min -1 550 rad min -1 600 rad min -1 650 rad min -1 700 rad min -1 750 rad min -1 800 rad min -1 .

[0057] Furthermore, the mixture is subjected to rotary evaporation under vacuum to obtain a precursor material with atomically homogeneous mixing. In some embodiments, the rotational evaporation step under vacuum is performed at a low rotational speed of 20 rpm. -1 ~40 rad min -1 Rotary evaporation is a good way to quickly and efficiently remove liquid from a system.

[0058] In step S03, the precursor material is ground and then subjected to solid-state sintering to obtain a nickel-rich cathode material. Since the obtained precursor material is an atomically homogeneous mixture, solid-state sintering ensures the preparation of a high-purity nickel-rich cathode material, guarantees no element loss during synthesis, ensures high atomic utilization, achieves precise control of the stoichiometry, and effectively avoids the formation of non-stoichiometric nickel-rich materials.

[0059] In some embodiments, the precursor material is ground, which increases the surface area and contact area between the materials, thus improving the sintering rate.

[0060] In some embodiments, solid-state sintering is carried out in an oxygen atmosphere or an air atmosphere. Sintering in an oxygen atmosphere or an air atmosphere ensures that the overall process contains oxygen, which is conducive to the chemical reaction.

[0061] In some embodiments, the solid-state sintering treatment includes a first sintering treatment and a second sintering treatment, wherein, during the first stage of the solid-state sintering treatment, the first sintering temperature is 550–650°C, and the first heating rate is 0.5–5°C / min. -1 The first sintering time is 1–5 hours; during the second stage of solid-state sintering, the second sintering temperature is 720–800℃, and the second heating rate is 0.5–1.5℃ / min. -1The second sintering time is 5–15 hours. A two-stage solid-state sintering process is employed, in which the temperature of the second stage sintering is controlled to be higher than that of the first stage. During the first stage sintering, the decomposition reaction of the various metal sources mainly occurs, while during the second stage sintering, the combination reaction of the oxides of the various metal sources mainly occurs in an oxygen atmosphere. If the sintering temperature is too high or the time is too long, the material is prone to agglomeration or even clumping, making it difficult to release capacity during charge and discharge. If the sintering temperature is too low or the time is too short, it is difficult to form the desired morphology, affecting electrochemical performance. If the heating rate is too fast, it is difficult to ensure sufficient material reaction, especially affecting the diffusion of lithium ions into the material structure. If the heating rate is too slow, it is not conducive to industrial production.

[0062] In some embodiments, the first heating rate is 1–3 °C / min. -1 The first sintering time is 2 to 4 hours.

[0063] In some embodiments, the second heating rate is 0.75–1 °C / min. -1 The second sintering time is 8 to 12 hours.

[0064] The second aspect of this application provides a nickel-rich cathode material, which is prepared by the above-described method for preparing nickel-rich cathode materials.

[0065] The nickel-rich cathode material provided in the second aspect of this application is obtained by using the preparation method of nickel-rich cathode material described above. Based on the preparation method of nickel-rich cathode material, it can ensure that the metal salt and lithium salt in the material can reach a state of atomic-level uniform mixing. Therefore, the obtained nickel-rich cathode material has high crystallinity and intact layered structure, which can significantly improve the structural stability of the material during charging and discharging, reduce uneven stress distribution and reduce the generation of microcracks; low cation mixing is conducive to increasing the amount of active lithium in the cathode material and ensuring the integrity of lithium ion diffusion channels; the stoichiometry is accurate, which can effectively avoid the generation of nickel-rich materials with non-stoichiometric ratios, which is conducive to obtaining nickel-rich cathode materials with excellent properties and wide application range.

[0066] A third aspect of this application provides a lithium-ion battery positive electrode, which includes a positive electrode material, a conductive agent, and a binder, wherein the positive electrode material is selected from the above-mentioned nickel-rich positive electrode material.

[0067] The lithium-ion battery cathode provided in the third aspect of this application uses a nickel-rich cathode material as the cathode material, which can increase the amount of active lithium in the lithium-ion battery cathode and improve the cycle performance and structural stability of the battery.

[0068] The fourth aspect of this application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is selected from the above-mentioned lithium-ion battery positive electrode.

[0069] The lithium-ion battery provided in the fourth aspect of this application has excellent cycle performance, high specific capacity, high capacity retention, and strong structural stability because it uses a cathode containing nickel-rich cathode material as the cathode. This makes it suitable for widespread use.

[0070] The following description is based on specific embodiments.

[0071] Example 1

[0072] Nickel-rich cathode materials and their preparation methods

[0073] The nickel-rich cathode material provided is LiNi 0.9 Mn 0.05 Co 0.05 O2 (NCM90).

[0074] The preparation method is as follows:

[0075] Weigh out 90 mmol Ni(NO3)2·6H2O, 5 mmol Mn(NO3)2·4H2O, 5 mmol Co(NO3)2·6H2O and 101 mmol LiNO3 and dissolve them in a round-bottom flask containing 100 mL of deionized water. Heat to 60 °C and stir rapidly at a rate of 500 rad / min. -1 Next, add 15 mL of 0.8 mol / L nitric acid solution and 80 mL of ethyl acetate, and stir rapidly at a rate of 500 rad / min to dissolve. -1 Next, rotary evaporation is performed under vacuum to rapidly evaporate the water in the solution and obtain a solid. The solid is then ground into powder and placed in a tube furnace. Under an oxygen atmosphere, it is first heated at 2°C for 1 minute. -1 The heating rate was initially set at room temperature to 600℃ and held at that temperature for 3.5 hours, then increased at a rate of 0.8℃ per minute. -1 High-performance nickel-rich material LiNi was obtained by heating to 750℃ at a heating rate and holding at that temperature for 10 hours. 0.9 Mn 0.05 Co 0.05 O2 (NCM90).

[0076] Example 2

[0077] Nickel-rich cathode materials and their preparation methods

[0078] The nickel-rich cathode material provided is LiNi 0.95 Mn 0.03 Co 0.02 O2 (NCM95).

[0079] The preparation method is as follows:

[0080] Weigh out 95 mmol Ni(NO3)2·6H2O, 3 mmol Mn(NO3)2·4H2O, 2 mmol Co(NO3)2·6H2O, and 101 mmol LiNO3 and dissolve them in a round-bottom flask containing 100 mL of deionized water. Heat the flask to 60 °C and stir rapidly at a rate of 500 rad / min. -1 Next, add 15 mL of 0.8 mol / L nitric acid solution and 80 mL of ethyl acetate, and continue stirring to dissolve at a stirring rate of 500 rad / min. -1 Next, rotary evaporation is performed under vacuum to rapidly evaporate the water in the solution and obtain a solid. The solid is then ground into powder and placed in a tube furnace. Under an oxygen atmosphere, it is first heated at 2°C for 1 minute. -1 The heating rate was initially set at room temperature to 600℃ and held at that temperature for 3.5 hours, then increased at a rate of 0.8℃ per minute. -1 High-performance nickel-rich material LiNi was obtained by heating to 730℃ at a heating rate and holding at that temperature for 10 hours. 0.95 Mn 0.03 Co 0.02 O2 (NCM95).

[0081] Example 3

[0082] Nickel-rich cathode materials and their preparation methods

[0083] The nickel-rich cathode material provided is LiNi 0.93 Mn 0.03 Co 0.02 Sr 0.01 Zr 0.01 O2(SZ-NCM93).

[0084] The preparation method is as follows:

[0085] Weigh out 93 mmol Ni(NO3)2·6H2O, 3 mmol Mn(NO3)2·4H2O, 2 mmol Co(NO3)2·6H2O, 1 mmol Sr(NO3)2, 1 mmol ZrO(NO3)2·xH2O, and 101 mmol LiNO3, and dissolve them in a round-bottom flask containing 100 mL of deionized water. Heat the flask to 60 °C and stir rapidly at a rate of 500 rad / min. -1 Next, add 15 mL of 0.8 mol / L nitric acid solution and 80 mL of ethyl acetate, and continue stirring to dissolve at a stirring rate of 500 rad / min. -1Next, rotary evaporation is performed under vacuum to rapidly evaporate the water in the solution and obtain a solid. The solid is then ground into powder and placed in a tube furnace. Under an oxygen atmosphere, it is first heated at 2°C for 1 minute. -1 The heating rate was initially set at room temperature to 600℃ and held at that temperature for 3.5 hours, then increased at a rate of 0.8℃ per minute. -1 High-performance nickel-rich material LiNi was obtained by heating to 740℃ at a heating rate and holding at that temperature for 10 hours. 0.93 Mn 0.03 Co 0.02 Sr 0.01 Zr 0.01 O2(SZ-NCM93).

[0086] Example 4

[0087] Nickel-rich cathode materials and their preparation methods

[0088] The nickel-rich cathode material provided is LiNi 0.95 Mn 0.03 Al 0.02 O2 (NMA95).

[0089] The preparation method is as follows:

[0090] Weigh out 95 mmol Ni(NO3)2·6H2O, 3 mmol Mn(NO3)2·4H2O, 2 mmol Al(NO3)3·9H2O and 101 mmol LiNO3 and dissolve them in a round-bottom flask containing 100 mL of deionized water. Heat to 60 °C and stir rapidly at a rate of 500 rad / min. -1 Next, add 20 mL of 1.0 mol / L hydrochloric acid solution and 80 mL of ethyl acetate, and continue stirring to dissolve at a stirring rate of 500 rad / min. -1 Next, rotary evaporation is performed under vacuum to rapidly evaporate the water in the solution and obtain a solid. The solid is then ground into powder and placed in a tube furnace. Under an oxygen atmosphere, it is first heated at 2°C for 1 minute. -1 The heating rate was initially set at room temperature to 600℃ and held at that temperature for 3.5 hours, then increased at a rate of 0.8℃ per minute. -1 High-performance nickel-rich material LiNi was obtained by heating to 720℃ at a heating rate and holding at that temperature for 10 hours. 0.95 Mn 0.03 Al 0.02 O2 (NMA95).

[0091] Example 5

[0092] Nickel-rich cathode materials and their preparation methods

[0093] The nickel-rich cathode material provided is LiNi 0.9 Mn 0.05 Co0.05 O2 (NCM90).

[0094] The preparation method is as follows:

[0095] Weigh out 90 mmol Ni(NO3)2·6H2O, 5 mmol Mn(NO3)2·4H2O, 5 mmol Co(NO3)2·6H2O and 101 mmol LiNO3 and dissolve them in a round-bottom flask containing 100 mL of deionized water. Heat to 60 °C and stir rapidly at a rate of 520 rad / min. -1 Next, add 15 mL of 0.8 mol / L nitric acid solution and 80 mL of ethyl acetate, and stir rapidly to dissolve at a stirring rate of 520 rad / min. -1 Next, rotary evaporation is performed under vacuum to rapidly evaporate the water in the solution and obtain a solid. The solid is then ground into powder and placed in a tube furnace, where it is first heated at 5°C for 1 minute under an oxygen atmosphere. -1 The heating rate was initially set at room temperature to 550℃ and held at that temperature for 5 hours, then increased at a rate of 1℃ per minute. -1 High-performance nickel-rich material LiNi was obtained by heating to 720℃ at a heating rate and holding at that temperature for 13 hours. 0.9 Mn 0.05 Co 0.05 O2 (NCM90).

[0096] Example 6

[0097] Nickel-rich cathode materials and their preparation methods

[0098] The nickel-rich cathode material provided is LiNi 0.95 Mn 0.03 Co 0.02 O2 (NCM95).

[0099] The preparation method is as follows:

[0100] Weigh out 95 mmol Ni(NO3)2·6H2O, 3 mmol Mn(NO3)2·4H2O, 2 mmol Co(NO3)2·6H2O, and 101 mmol LiNO3, and dissolve them in a round-bottom flask containing 100 mL of deionized water. Heat the flask to 60 °C and stir rapidly at a rate of 550 rad / min. -1 Next, add 15 mL of 0.8 mol / L nitric acid solution and 80 mL of ethyl acetate, and continue stirring to dissolve at a stirring rate of 550 rad / min. -1 Next, rotary evaporation is performed under vacuum to rapidly evaporate the water in the solution and obtain a solid. The solid is then ground into powder and placed in a tube furnace, where it is first heated at 0.5°C for 1 minute under an oxygen atmosphere. -1The heating rate was initially set at room temperature to 580℃ and held at that temperature for 4 hours, then increased at a rate of 0.5℃ per minute. -1 High-performance nickel-rich material LiNi was obtained by heating to 780℃ at a heating rate and holding at that temperature for 8 hours. 0.95 Mn 0.03 Co 0.02 O2 (NCM95).

[0101] Example 7

[0102] Nickel-rich cathode materials and their preparation methods

[0103] The nickel-rich cathode material provided is LiNi 0.93 Mn 0.03 Co 0.02 Sr 0.01 Zr 0.01 O2(SZ-NCM93).

[0104] The preparation method is as follows:

[0105] Weigh out 93 mmol Ni(NO3)2·6H2O, 3 mmol Mn(NO3)2·4H2O, 2 mmol Co(NO3)2·6H2O, 1 mmol Sr(NO3)2, 1 mmol ZrO(NO3)2·xH2O, and 101 mmol LiNO3, and dissolve them in a round-bottom flask containing 100 mL of deionized water. Heat the flask to 60 °C and stir rapidly at a rate of 580 rad / min. -1 Next, add 15 mL of 0.8 mol / L nitric acid solution and 80 mL of ethyl acetate, and continue stirring to dissolve at a stirring rate of 580 rad / min. -1 Next, rotary evaporation is performed under vacuum to rapidly evaporate the water in the solution and obtain a solid. The solid is then ground into powder and placed in a tube furnace, where it is first heated at 4°C for 1 minute under an oxygen atmosphere. -1 The heating rate was initially set at room temperature to 650℃ and held for 2 hours, then increased at a rate of 1.2℃ per minute. -1 High-performance nickel-rich material LiNi was obtained by heating to 800℃ at a heating rate and holding at that temperature for 6 hours. 0.93 Mn 0.03 Co 0.02 Sr 0.01 Zr 0.01 O2(SZ-NCM93).

[0106] Example 8

[0107] Nickel-rich cathode materials and their preparation methods

[0108] The nickel-rich cathode material provided is LiNi 0.95 Mn 0.03 Al 0.02O2 (NMA95).

[0109] The preparation method is as follows:

[0110] Weigh out 95 mmol Ni(NO3)2·6H2O, 3 mmol Mn(NO3)2·4H2O, 2 mmol Al(NO3)3·9H2O, and 101 mmol LiNO3, and dissolve them in a round-bottom flask containing 100 mL of deionized water. Heat the flask to 60 °C and stir rapidly at a rate of 600 rad / min. -1 Next, add 20 mL of 1.0 mol / L hydrochloric acid solution and 80 mL of ethyl acetate, and continue stirring to dissolve at a stirring rate of 600 rad / min. -1 Next, rotary evaporation is performed under vacuum to rapidly evaporate the water in the solution and obtain a solid. The solid is then ground into powder and placed in a tube furnace, where it is first heated at 5°C for 1 minute under an oxygen atmosphere. -1 The heating rate was initially set at room temperature to 650℃ and held at that temperature for 1.5 hours, then increased at a rate of 1.5℃ per minute. -1 High-performance nickel-rich material LiNi was obtained by heating to 8000℃ at a heating rate and holding at that temperature for 15 hours. 0.95 Mn 0.03 Al 0.02 O2 (NMA95).

[0111] Comparative Example 1

[0112] Nickel-rich cathode materials and their preparation methods

[0113] The nickel-rich cathode material provided is LiNi 0.9 Mn 0.05 Co 0.05 O2-1(NCM90-1).

[0114] The preparation method is as follows:

[0115] Weigh 0.1 mol of commercial Ni 0.9 Co 0.05 Mn 0.05 (OH)₂ and 0.102 mol LiOH were placed in a ball mill jar with a ball-to-material ratio of 5:1. The ball mill jar was then set to 300 rad / min. -1 The material was ball-milled at a speed of 2000 rpm for 2 hours, and then transferred to a tube furnace. Under an oxygen atmosphere, it was first milled at 2000 rpm for 2 minutes. -1 The heating rate was initially set at room temperature to 600℃ and held at that temperature for 3.5 hours, then increased at a rate of 0.8℃ per minute. -1 After heating to 750℃ at a rising rate and holding at that temperature for 10 hours, nickel-rich material LiNi was obtained. 0.9 Mn 0.05 Co 0.05 O2-1(NCM90-1).

[0116] Comparative Example 2

[0117] Nickel-rich cathode materials and their preparation methods

[0118] The nickel-rich cathode material provided is LiNi 0.9 Mn 0.05 Co 0.05 O2-2(NCM90-2).

[0119] The preparation method is as follows: Weigh 90 mmol Ni(NO3)2·6H2O, 5 mmol Mn(NO3)2·4H2O, 5 mmol Co(NO3)2·6H2O and 101 mmol LiNO3 and dissolve them in a round-bottom flask containing 100 mL of deionized water. Heat to 60 °C and stir rapidly at a stirring rate of 500 rad / min. -1 After the metal salt dissolves, the temperature is further increased to 105°C, causing the water in the solution to gradually evaporate and a mixed solid to be obtained. The solid is then ground into powder and placed in a tube furnace, where it is heated at 2°C for 1 minute under an oxygen atmosphere. -1 The heating rate was initially set at room temperature to 600℃ and held at that temperature for 3.5 hours, then increased at a rate of 0.8℃ per minute. -1 High-performance nickel-rich material LiNi was obtained by heating to 750℃ at a heating rate and holding at that temperature for 10 hours. 0.9 Mn 0.05 Co 0.05 O2-2(NCM90-2).

[0120] Comparative Example 3

[0121] Nickel-rich cathode materials and their preparation methods

[0122] The nickel-rich cathode material provided is LiNi 0.93 Mn 0.03 Co 0.02 Sr 0.01 Zr 0.01 O2(SZ-NCM93-1).

[0123] The preparation method is as follows: Weigh 99 mmol of commercially available Ni 0.95 Co 0.02 Mn 0.03 (OH)₂, 0.5 mmol nano-Sr(OH)₂, 1 mmol nano-ZrO₂, and 102 mmol LiOH were placed in a ball mill jar with a ball-to-material ratio of 5:1. The ball mill jar was then fixed at 300 rpm. -1 The material was ball-milled at a speed of 2000 rpm for 2 hours, and then transferred to a tube furnace. Under an oxygen atmosphere, it was first milled at 2000 rpm for 2 minutes. -1 The heating rate was initially set at room temperature to 600℃ and held at that temperature for 3.5 hours, then increased at a rate of 0.8℃ per minute.-1 After heating to 740℃ at a rising rate and holding at that temperature for 10 hours, nickel-rich material LiNi was obtained. 0.93 Mn 0.03 Co 0.02 Sr 0.01 Zr 0.01 O2(SZ-NCM93-1).

[0124] Property Test

[0125] (a) The nickel-rich cathode materials obtained in Examples 1-4 and Comparative Examples 1-3 were subjected to X-ray diffraction analysis, scanning electron microscopy analysis, transmission electron microscopy analysis and other analyses.

[0126] (II) The nickel-rich cathode materials obtained in Examples 1-8 and Comparative Examples 1-3 were assembled into 2016-type button batteries and charged and discharged in the voltage range of 2.8-4.3V. Then, the batteries were activated at 0.1C and 0.5C for one cycle at test temperatures of 25℃ and 50℃, respectively, and then cycled at 1.0C. The test data are shown in Table 1 and Table 2 below.

[0127] Results Analysis

[0128] (I) For the materials NCM90, NCM95, SZ-NCM93, and NCA95 obtained in Examples 1-4 of this application, as shown in XRD Figure 1, the crystallinity of all materials is very high, and the I003 peak is significantly stronger than the I104 peak, indicating that the materials have a low degree of cation mixing. In addition, the other two characteristic peaks 006 / 012 and 108 / 110 of the prepared materials show obvious splitting, which means that all materials have a good layered structure, indicating that the method of this application can prepare nickel-rich ternary materials with high crystallinity, low degree of cation mixing, and good layered structure. In contrast, the nickel-rich material prepared in the comparative example, as shown in Figure 5, although the characteristic peak of LiNiO2 appears, the peak intensities of the I003 and I104 peaks are not much different, which means that the material has more severe cation mixing. At the same time, its 006 / 012 characteristic peak does not show obvious splitting, but shows fusion, indicating that the material has a poor layered structure.

[0129] Figure 2 shows scanning electron microscope (SEM) images of the samples prepared in Examples 1, 2, Comparative Example 1, and 2. Clearly, the materials prepared using the method of this application exhibit a near-single-crystal morphology (NCM90 and NCM95), with clear primary particle boundaries, clean surfaces, and no obvious impurity phase adhesion or agglomeration. Furthermore, the materials do not exhibit large-scale agglomeration, which is beneficial for exposing more stable crystal planes and thus improving the electrochemical performance. Conversely, for Comparative Example 1, the material prepared using a commercial precursor and ball milling method exhibits a near-spherical morphology, and many impurity phases adhere to the material surface, which is detrimental to the material's electrochemical performance. Additionally, for Comparative Example 2, the material shows extensive and severe agglomeration, unclear primary particle boundaries, and obvious twinning, which is also detrimental to the material's electrochemical performance.

[0130] Figures 3, 4, and 6 are TEM images of the samples prepared in Examples 1, 3, and Comparative Example 1, respectively. As shown in the figures, the NCM90 and SZ-NCM93 prepared in Examples 1 and 3 exhibit extremely high crystallinity and a good layered structure, with regular atomic arrangement, clear interfaces, and no obvious impurity phase formation. This further demonstrates that the method of this application can prepare nickel-rich materials with excellent structures. However, the NCM90-1 material prepared in Comparative Example 1 has a relatively poor layered structure, and obvious spinel or rock salt phases appear both inside the bulk phase and at the interfaces.

[0131] (II) As shown in Tables 1 and 2 below, compared with nickel-rich materials prepared by traditional ball milling and high-mixing methods, the nickel-rich materials obtained by the method of this application not only achieve atomically homogeneous mixing and precise control of the stoichiometry of nickel-rich materials, but also exhibit higher crystallinity, lower cation mixing, and a better layered structure after sintering. High crystallinity effectively reduces uneven stress distribution during charging and discharging, reducing microcrack formation; low cation mixing reduces the loss of active lithium, ensuring higher charge and discharge capacity; and the better layered structure ensures smooth lithium-ion transport channels, which is beneficial for improving the rate performance of the material. Furthermore, this application has significant advantages in preparing element-doped modified nickel-rich materials. Through the special precursor treatment of this application, the element-doped modified nickel-rich materials prepared by this application achieve true atomically homogeneous doping, which is beneficial for significantly improving the structural stability of nickel-rich materials during charging and discharging.

[0132] LiNi prepared by the method of this application 0.9 Mn 0.05 Co 0.05 The O2 (NCM90) material achieves a first-charge specific capacity of up to 230.2 mAh g at room temperature and 0.1C. -1 The discharge specific capacity is 207.5 mAh g. -1The initial coulombic efficiency was 90.1%, and the discharge specific capacity of the material after 100 and 300 cycles was 186.7 mAh g, respectively. -1 and 171.6mAh g -1 The capacity retention rates were 89.9% and 82.7%, respectively. However, the discharge specific capacity of MCM90-1 prepared by conventional methods was only 172.1 mAh g after 100 and 300 cycles. -1 and 155.4mAh g -1 The capacity retention rates were 83.4% and 75.3%, respectively. In particular, the element-doped modified nickel-rich material SZ-NCM93 exhibited excellent electrochemical performance under both room temperature and high temperature testing. After 100 and 200 cycles at 50℃, the discharge specific capacity of SZ-NCM93 remained as high as 196.2 mAh g⁻¹. -1 and 187.2mAh g -1 The capacity retention rates were 89.4% and 85.3%, respectively. However, the SZ-NCM93-1 material prepared using conventional methods showed a discharge specific capacity of only 182.7 mAh g after 100 and 200 cycles at 50°C. -1 and 173.4mAh g -1 The capacity retention rates were 84.3% and 80.1%, respectively.

[0133] Table 1 (25℃)

[0134]

[0135] Table 2 (50℃)

[0136]

[0137] In summary, the method for preparing nickel-rich cathode material provided in this application firstly obtains a mixed solution of lithium salt, nickel salt, and metal salt in an acidic solution using a liquid-phase dissolution method. Then, utilizing the low-boiling-point properties of the acid-low-boiling-point organic solvent-aqueous solution system under vacuum and high temperature, the solvent is rapidly evaporated, allowing metal cations and anions to precipitate simultaneously and quickly. This ensures that the lithium salt, nickel salt, and metal salt in the resulting precursor material achieve an atomically homogeneous mixture, avoiding uneven material mixing caused by ions precipitating at different rates due to varying crystallinity. Furthermore, a solid-state sintering process is used to form a nickel-rich cathode material with high crystallinity, a well-preserved layered structure, low cation mixing, and precise stoichiometry. This preparation method achieves a one-step atomically homogeneous mixture of metal salt and lithium salt, with no atomic loss and 100% atomic utilization. It enables precise control of the stoichiometry, is simple in process, and has mild and controllable reaction conditions, making it suitable for widespread industrial application.

[0138] Therefore, the nickel-rich cathode material prepared by the above-mentioned method ensures that the metal salt and lithium salt in the material can achieve atomic-level uniform mixing. As a result, the obtained nickel-rich cathode material has high crystallinity and a well-preserved layered structure, which can significantly improve the structural stability of the material during charge and discharge, reduce uneven stress distribution and reduce the generation of microcracks; low cation mixing is conducive to increasing the amount of active lithium in the cathode material and ensuring the integrity of lithium ion diffusion channels; and the precise stoichiometry can effectively avoid the formation of nickel-rich materials with non-stoichiometric ratios, which is conducive to obtaining nickel-rich cathode materials with excellent properties and wide application range.

[0139] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a nickel-rich cathode material, characterized in that, The steps include: based on the chemical formula LiNi x M1 y M2 z O2 provides a certain molar amount of lithium salt, nickel salt, M1 metal salt, and M2 metal salt as raw materials, wherein M1 and M2 are selected from different transition metals, 0.8≤x<1, 0<y<0.2, 0<z<0.2, and x+y+z=1; the raw materials, acid solution, and organic solvent are mixed, including: mixing the raw materials with water, heating and rapidly stirring, then sequentially adding the acid solution and organic solvent and rapidly stirring until dissolved to obtain a mixed solution, wherein the mixed solution is an acid-low-boiling-point organic solvent-water solution system; the volume ratio of the added acid solution to the total volume of the mixed solution is 1:20-1:10; the volume ratio of the added organic solvent to the total volume of the mixed solution is 1:10-1:2; wherein the rapid stirring rate is 500 rad / min. -1 ~600 rad min -1 The acid solution is selected from at least one of nitric acid solution and hydrochloric acid solution; the organic solvent is selected from at least one of dichloromethane, trichloromethane, and ethyl acetate; rotary evaporation is performed under vacuum to obtain an atomically homogeneous precursor material; the rotation speed is 20 rad / min. -1 ~40 rad min -1 The precursor material is ground and then subjected to solid-state sintering to obtain a nickel-rich cathode material.

2. The method for preparing the nickel-rich cathode material according to claim 1, characterized in that, The mass ratio of the raw material to the water is 1:1 to 10; and / or the heating temperature is 50-80°C.

3. The method for preparing the nickel-rich cathode material according to claim 2, characterized in that, The mass ratio of the raw material to the water is 1:2~5.

4. The method for preparing the nickel-rich cathode material according to claim 1, characterized in that, The solid-state sintering treatment includes a first sintering treatment and a second sintering treatment; wherein, during the first sintering treatment, the first sintering temperature is 550~650℃, and the first heating rate is 0.5~5℃min. -1 The first sintering time is 1 to 5 hours; and / or during the second sintering process, the second sintering temperature is 720 to 800°C, and the second heating rate is 0.5 to 1.5°C / min. -1 The second sintering time is 5 to 15 hours.

5. The method for preparing the nickel-rich cathode material according to claim 4, characterized in that, The first heating rate is 1~3℃ min. -1 The first sintering time is 2-4 hours; and / or the second heating rate is 0.75-1℃ min. -1 The second sintering time is 8 to 12 hours.

6. The method for preparing the nickel-rich cathode material according to claim 1 or 4, characterized in that, The solid-state sintering process is carried out in an oxygen atmosphere or an air atmosphere.

7. The method for preparing the nickel-rich cathode material according to claim 1, characterized in that, M1 and M2 are independently selected from any one of Mn, Co, Mg, Zr, Ti, Nb, and Sr; and / or, the metal salt M1 and the metal salt M2 are independently selected from at least one of soluble metal sulfates, soluble metal nitrates, and soluble metal chlorides; and / or, the nickel salt is selected from at least one of nickel sulfate, nickel nitrate, and nickel chloride; and / or, the lithium salt is selected from at least one of lithium sulfate, lithium nitrate, lithium hydroxide, lithium carbonate, lithium oxide, lithium chloride, and lithium oxalate.

8. A nickel-rich cathode material, characterized in that, The nickel-rich cathode material is prepared by the method for preparing nickel-rich cathode materials according to any one of claims 1 to 7.

9. A lithium-ion battery positive electrode, characterized in that, The lithium-ion battery cathode comprises a cathode material, a conductive agent, and a binder, wherein the cathode material is selected from the nickel-rich cathode material described in claim 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is selected from the lithium-ion battery positive electrode of claim 9.

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