High-nickel positive electrode material, preparation method therefor and use thereof

Abstract

The present application relates to a high-nickel positive electrode material, a preparation method therefor and a use thereof. Phases of the high-nickel positive electrode material include a layered phase and a rock-salt phase, the space group of the layered phase is R-3m, the space group of the rock-salt phase is Fm-3m, the mass fraction of the rock-salt phase in the high-nickel positive electrode material is 3-23%, and a lithium vacancy defect is present in the rock-salt phase. The high-nickel positive electrode material of the present application has high specific capacity, excellent cycling performance, and low cost.

Description

High-nickel positive electrode material, preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202410880091.6, filed on July 2, 2024, and entitled "High-nickel positive electrode material, preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of lithium ion batteries, in particular to a high-nickel positive electrode material, a preparation method and an application thereof. BACKGROUND

[0003] High-nickel ternary materials have become one of the preferred materials for lithium ion battery positive electrode materials because they have high specific capacity and can make lithium ion batteries have high energy density.

[0004] However, with the increase of nickel content, high-nickel ternary materials have problems such as reduced safety performance, gas production and cracking, which leads to poor structural stability and poor cycle performance of lithium ion batteries. At the same time, due to the high cost of cobalt, excessive cobalt content leads to high production cost of high-nickel ternary materials, which makes the cost of lithium ion batteries high, which is not conducive to the sustainable development of lithium ion batteries. SUMMARY

[0005] Therefore, it is necessary to provide a high-nickel positive electrode material, a preparation method and an application thereof to solve the above problems. The high-nickel positive electrode material has high specific capacity, excellent cycle performance and low cost.

[0006] In a first aspect, the present application provides a high-nickel positive electrode material, wherein the phase of the high-nickel positive electrode material includes a layered phase and a rock salt phase, the space group of the layered phase is R-3m, the space group of the rock salt phase is Fm-3m, the mass fraction of the rock salt phase in the high-nickel positive electrode material is 3%-23%, and lithium vacancy defects exist in the rock salt phase.

[0007] In one embodiment, the molecular formula of the high-nickel positive electrode material is Li m Ni x Mn y M z O2, wherein 0.9

[0008] In one of the embodiments, the high-nickel positive electrode material is secondary microspheres formed by stacking primary particles, wherein the particle size of the primary particles is 50-100 nm, and the median particle size of the secondary microspheres is 5-20 μm.

[0009] In one of the embodiments, the rock salt phase is distributed in the bulk structure and the surface structure of the high-nickel positive electrode material, and the mass fraction of the rock salt phase in the bulk structure of the high-nickel positive electrode material is greater than the mass fraction of the rock salt phase in the surface structure of the high-nickel positive electrode material.

[0010] In one of the embodiments, the crystal structure of the high-nickel positive electrode material satisfies at least one of the following conditions:

[0011] (1) there is a (110) crystal face characteristic diffraction peak in the X-ray diffraction pattern of the high-nickel positive electrode material in the diffraction angle range of 14-15°;

[0012] (2) the characteristic diffraction peak existing in the X-ray diffraction pattern of the high-nickel positive electrode material in the diffraction angle range of 15-15.5° is a single peak;

[0013] (3) there is a characteristic diffraction peak in the X-ray diffraction pattern of the high-nickel positive electrode material in the diffraction angle range of 17.4-17.8°;

[0014] (4) the characteristic diffraction peak existing in the X-ray diffraction pattern of the high-nickel positive electrode material in the diffraction angle range of 24.6-25.2° is a single peak.

[0015] The high-nickel positive electrode material of the present application has lithium vacancy defects in the rock salt phase, which can inhibit the phase transition from the rock salt phase to the layered phase and inhibit the crystal growth, so that the high-nickel positive electrode material has both the layered phase with the space group of R-3m and the rock salt phase with the space group of Fm-3m, thereby inhibiting the large lattice expansion and shrinkage during the lithium extraction process of the layered phase, so that the high-nickel positive electrode material has low lattice expansion and shrinkage during the cycle process, and further has excellent cycle performance and safety performance, and can effectively reduce the content of cobalt or eliminate the addition of cobalt, thereby reducing the cost. At the same time, by controlling the content of the rock salt phase, the specific capacity and cycle performance of the nickel positive electrode material can be balanced, so that the high-nickel positive electrode material has high specific capacity while improving the cycle performance. Therefore, the high-nickel positive electrode material of the present application can have high specific capacity, excellent cycle performance and low cost.

[0016] In a second aspect, the present application provides a preparation method of the high-nickel positive electrode material, comprising:

[0017] A transition metal hydroxide precursor is provided;

[0018] The lithium source and the transition metal hydroxide precursor are mixed, and then subjected to step-by-step sintering in an oxygen atmosphere to obtain a high-nickel positive electrode material, wherein the molar ratio of the lithium source to the transition metal hydroxide precursor is R, 0.9 < R < 1, and in the step-by-step sintering, the temperature of the first step sintering is 450-650°C, the sintering time is 8-16h, the temperature of the second step sintering is 700-800°C, and the sintering time is 10-16h.

[0019] In one of the embodiments, the transition metal hydroxide precursor has a molecular formula of Ni x Mn y M z (OH)2, wherein 0.9≤x<1, 0

[0020] In one of the embodiments, the transition metal hydroxide precursor is prepared by a co-precipitation method, and the co-precipitation method comprises:

[0021] A mixed solution is prepared by mixing a nickel source, a manganese source, an M source, and water, wherein the M source is selected from at least one of Co, Al, Ti, Mg, Zr, Nb, Ta, W, Mo, Ce, La, Y, Sb, Zn, and Sr;

[0022] The mixed solution, a precipitant solution, and a complexing agent solution are mixed and subjected to a co-precipitation reaction under a protective atmosphere, and then subjected to aging, filtration, washing, and drying to obtain the transition metal hydroxide precursor.

[0023] In one of the embodiments, at least one of the following conditions is met in the step of the co-precipitation method:

[0024] (1) the reaction temperature is controlled to be 50-55°C, the reaction pH value is controlled to be 11.5-12.5, the protective atmosphere is selected from an inert gas atmosphere, and the stirring speed is controlled to be 600-1000rpm;

[0025] (2) the concentration of the mixed solution (i.e., the sum of the concentrations of the nickel source, the manganese source, and the M source in the mixed solution) is 1-3mol / L;

[0026] (3) the concentration of the precipitant solution is 2-6mol / L, and the precipitant solution is selected from a sodium hydroxide solution;

[0027] (4) the concentration of the complexing agent solution is 2-6 mol / L, and the complexing agent solution is selected from ammonia water;

[0028] (5) the nickel source is selected from at least one of nickel sulfate, nickel chloride, nickel acetate or nickel nitrate, the manganese source is selected from at least one of manganese sulfate, manganese chloride, manganese acetate or manganese nitrate, and the M source is selected from at least one of cobalt sulfate, cobalt chloride, cobalt acetate or cobalt nitrate.

[0029] The preparation method of the high-nickel positive electrode material provided by the application can control the generation ratio and distribution of the rock salt phase by controlling the molar ratio between the lithium source and the transition metal hydroxide precursor and the conditions of the step-by-step sintering, so that lithium vacancy defects exist in the rock salt phase, forming a high-nickel positive electrode material with both a layered phase and a rock salt phase; meanwhile, the growth of primary particles can be inhibited, so that the size of the primary particles is within hundreds of nanometers, so that the high-nickel positive electrode material has high specific capacity, rate performance and excellent cycle performance.

[0030] In a third aspect, the application provides a positive electrode sheet prepared from the high-nickel positive electrode material.

[0031] In a fourth aspect, the application provides a lithium ion battery prepared from the positive electrode sheet. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments described in the application, and those skilled in the art can also obtain other drawings according to these drawings without any creative effort.

[0033] FIG. 1 is an X-ray diffraction pattern and XRD refinement result of the high-nickel positive electrode material in Example 1 of the application, wherein RS in FIG. 1 represents a rock salt phase, and L represents a layered phase;

[0034] FIG. 2 is an electron microscope image of the high-nickel positive electrode material in Example 2 of the application, wherein the magnification of the electron microscope image is 1000 times;

[0035] FIG. 3 is an electron microscope image of the high-nickel positive electrode material in Example 2 of the application, wherein the magnification of the electron microscope image is 30000 times;

[0036] FIG. 4 is an X-ray diffraction pattern of the high-nickel positive electrode material in Comparative Example 1 of the application, wherein L in FIG. 4 represents a layered phase. DETAILED DESCRIPTION

[0037] For the purpose of promoting an understanding of the present application, the present application will be described in greater detail below. It should be noted, however, that the present application can be practiced in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for describing the specific embodiments or examples only and is not intended to be limiting of the application. As used herein, the term "and / or", alone or in combination, means that there is at least one of the items named and that combinations of the items are also included.

[0039] The high-nickel positive electrode material provided by the present application has a phase including a layered phase and a rock salt phase, the layered phase has a space group of R-3m, the rock salt phase has a space group of Fm-3m, the mass fraction of the rock salt phase in the high-nickel positive electrode material is 3%-23%, and lithium vacancy defects exist in the rock salt phase.

[0040] The high-nickel positive electrode material of the present application has lithium vacancy defects in the whole high-nickel positive electrode material due to the existence of lithium vacancy defects in the rock salt phase. The existence of the lithium vacancy defects can inhibit the phase transition from the rock salt phase to the layered phase and inhibit the crystal growth, so that the high-nickel positive electrode material has both the layered phase with a space group of R-3m and the rock salt phase with a space group of Fm-3m, thereby inhibiting the large lattice expansion and contraction during the lithium extraction process of the layered phase, so that the high-nickel positive electrode material has low lattice expansion and contraction during the cycle process, and further has excellent cycle performance and safety performance, and can effectively reduce the content of cobalt or does not need to add cobalt, thereby reducing the cost.

[0041] At the same time, by controlling the content of the rock salt phase, the specific capacity and cycle performance of the nickel positive electrode material can be kept in a balanced state, so that the cycle performance of the high-nickel positive electrode material can be improved, for example, the median voltage attenuation degree of the high-nickel positive electrode material of the present application is less than 0.05V after 100 cycles at a rate of 0.5C and a voltage of 2.7V-4.3V, while ensuring that the high-nickel positive electrode material has a high specific capacity.

[0042] It should be noted that in the present application, the median voltage attenuation degree is the difference between the median voltages of the first discharge curve and the 100th discharge curve.

[0043] It should be noted that in ternary materials, cobalt is mainly used to stabilize the layered structure of the ternary material, which can improve its cycle performance. However, in this application, the presence of a rock salt phase containing lithium vacancy defects can suppress the large lattice expansion and contraction during the lithium insertion / extraction process in the layered phase. This results in lower lattice expansion and contraction in the high-nickel cathode material during cycling, improving its structural stability and thus giving it excellent cycle performance. It is understood that the high-nickel cathode material of this application can effectively reduce the cobalt content or eliminate the need for cobalt addition, thereby reducing material costs.

[0044] Therefore, the high-nickel cathode material of this application can have high specific capacity, excellent cycle performance and low cost.

[0045] For example, the mass fraction of the rock salt phase in the high-nickel cathode material can be a range of 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, or any combination thereof.

[0046] Furthermore, the molecular formula of the high-nickel cathode material is Li. m Ni x Mn y M z O2, wherein 0.9 < m < 1, 0.9 ≤ x < 1, 0 < y ≤ 0.1, x + y + z = 1, and M is selected from at least one of Co, Al, Ti, Mg, Zr, Nb, Ta, W, Mo, Ce, La, Y, Sb, Zn, and Sr. Further, 0.9 < x < 1, 0 < y ≤ 0.05. Based on the molecular formula of the high-nickel cathode material, it is known that the high-nickel cathode material of this application has lithium vacancy defects and a high nickel content. Simultaneously, by adding a specific amount of manganese and doping element M, the high-nickel cathode material can achieve both high specific capacity and excellent cycle performance.

[0047] Furthermore, in high-nickel cathode materials, the proportion of lithium in the rock salt phase to the total amount of transition metal elements is less than 1, meaning that lithium vacancy defects exist in the rock salt phase. For example, the molecular formula of a high-nickel cathode material is Li. m Ni x Mn y M z O2, in which the amount of lithium in the rock salt phase accounts for less than 1 of the total amount of transition metals (total amount of transition metals = amount of nickel + amount of manganese + amount of M), that is, there are lithium vacancy defects in the rock salt phase.

[0048] Exemplarily, in the high-nickel positive electrode material, the amount of substance a of lithium element in the rock salt phase and the total amount of substance b of transition metal elements can be 0.85-0.999, for example, 0.85, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98, 0.999, or a range consisting of any two of them.

[0049] Specifically, in the high-nickel positive electrode material, the chemical formula of the rock salt phase can be represented as Li a A b O2, 0.85≤a / b≤0.999, and a and b satisfy Li a A b O2 is electrically neutral; A represents the above-mentioned transition metal element, for example, the molecular formula of the high-nickel positive electrode material is Li m Ni x Mn y M z O2, A includes Ni, Mn, M.

[0050] In the present application, the content of each element in the rock salt phase can be measured by a conventional method, for example, the crystal structure of the high-nickel positive electrode material can be measured by an X-ray diffractometer, and the chemical composition (chemical formula) and other characteristics of the rock salt phase can be obtained by conventional crystal structure processing methods such as refinement.

[0051] Alternatively, the high-nickel positive electrode material is a secondary microsphere formed by stacking primary particles, wherein the particle size of the primary particles is 50-100 nm, for example, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or a range consisting of any two of them, and the median particle size of the secondary microsphere is 5-20 μm, for example, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, or a range consisting of any two of them, preferably 8-15 μm. In this way, the specific capacity and rate performance of the high-nickel positive electrode material can be further improved.

[0052] In the present application, the phase of the high-nickel positive electrode material includes a layered phase and a rock salt phase, and the rock salt phase is distributed in the bulk phase structure and the surface structure of the high-nickel positive electrode material. Under the structure and composition system of the high-nickel positive electrode material, lithium vacancy defects exist in the rock salt phase, so that the high-nickel positive electrode material as a whole has lithium vacancy defects. The existence of the lithium vacancy defects can inhibit the phase transition from the rock salt phase to the layered phase and inhibit the crystal growth, so that the high-nickel positive electrode material has both the layered phase with a space group of R-3m and the rock salt phase with a space group of Fm-3m, and the rock salt phase is distributed in the bulk phase structure and the surface structure of the high-nickel positive electrode material. Therefore, the large lattice expansion and contraction during the lithium extraction process of the layered phase can be inhibited, the high-nickel positive electrode material has low lattice expansion and contraction during the cycle process, and the high-nickel positive electrode material has excellent cycle performance and safety performance. In addition, the content of cobalt can be effectively reduced or cobalt does not need to be added, thereby reducing the cost.

[0053] Specifically, the mass fraction of the rock salt phase in the bulk phase structure of the high-nickel positive electrode material is greater than the mass fraction of the rock salt phase in the surface structure of the high-nickel positive electrode material. In this way, the structural stability of the high-nickel positive electrode material can be further improved.

[0054] Specifically, the high-nickel positive electrode material has a bulk phase structure and a surface structure on the surface of the bulk phase structure. The bulk phase structure is the main body of the high-nickel positive electrode material, and the surface structure is the surface part of the high-nickel positive electrode material. The content of the rock salt phase in the bulk phase structure of the high-nickel positive electrode material is greater than the content of the rock salt phase in the surface structure. As described above, the content can be represented by the mass fraction. The distribution of the rock salt phase in the high-nickel positive electrode material can be detected by a transmission electron microscope. The part with a high content of the rock salt phase is the bulk phase structure, and the part with a low content of the rock salt phase (the surface part) is the surface structure. In a specific implementation, the transmission electron microscope can be used to detect the high-nickel positive electrode material, and it can be clearly detected that the content of the rock salt phase in the bulk phase structure is greater than the content of the rock salt phase in the surface structure (i.e., the mass fraction of the rock salt phase in the bulk phase structure of the high-nickel positive electrode material is greater than the mass fraction of the rock salt phase in the surface structure of the high-nickel positive electrode material).

[0055] Optionally, the crystal structure of the high-nickel positive electrode material satisfies at least one of the following conditions: the X-ray diffraction pattern of the high-nickel positive electrode material has a (110) crystal face characteristic diffraction peak in the diffraction angle range of 14°-15°, and the (110) crystal face characteristic diffraction peak belongs to the layered phase; the X-ray diffraction pattern of the high-nickel positive electrode material has a characteristic diffraction peak in the diffraction angle range of 15°-15.5°, and the characteristic diffraction peak is a single peak composed of a (006) / (102) crystal face characteristic diffraction peak belonging to the layered phase and a (111) crystal face characteristic diffraction peak belonging to the rock salt phase; the X-ray diffraction pattern of the high-nickel positive electrode material has a characteristic diffraction peak in the diffraction angle range of 17.4°-17.8°, and the characteristic diffraction peak is composed of a (104) crystal face characteristic diffraction peak belonging to the layered phase and a (200) crystal face characteristic diffraction peak belonging to the rock salt phase; the X-ray diffraction pattern of the high-nickel positive electrode material has a characteristic diffraction peak in the diffraction angle range of 24.6°-25.2°, and the characteristic diffraction peak is a single peak composed of a (108) / (110) crystal face characteristic diffraction peak belonging to the layered phase and a (220) crystal face characteristic diffraction peak belonging to the rock salt phase.

[0056] It can be understood that the bulk phase structure and the surface structure of the high-nickel positive electrode material of the present application both distribute the layered phase and the rock salt phase, compared with the rock salt phase in the traditional positive electrode material which only exists in the surface structure of the positive electrode material, the distribution of the rock salt phase in the present application can fully utilize the high stability of the rock salt phase, reduce the phase change in the charging and discharging process, and better improve the structural stability of the high-nickel positive electrode material.

[0057] Meanwhile, the present application also provides a preparation method of the high-nickel positive electrode material, comprising:

[0058] S1, providing a transition metal hydroxide precursor;

[0059] S2, mixing a lithium source and the transition metal hydroxide precursor, and then performing step-by-step sintering in an oxygen atmosphere to obtain the high-nickel positive electrode material, wherein the molar ratio of the lithium source to the transition metal hydroxide precursor is R, 0.9

[0060] In view of the fact that the transition metal precursor and the lithium source will undergo different phase transitions during sintering as the temperature rises, in the present application, step sintering is adopted, specifically, the temperature of the first step of sintering is controlled to be 450-650 DEG C, at which temperature the transition metal precursor will first dehydrate to become a rock salt phase, and at this temperature, sintering is performed for 8-16 hours, so that the transition metal precursor is completely changed into a rock salt phase, and then reacts with the lithium source, at this time, the second step of sintering is performed, that is, the temperature is raised, and the temperature of the second step of sintering is controlled to be 700-800 DEG C, at which temperature the rock salt phase reacts with the lithium source and becomes a layered phase, and since the molar ratio of the lithium source to the transition metal hydroxide precursor is R, 0.9 < R < 1, that is, the amount of lithium source is insufficient, therefore, only most of the rock salt phase forms a layered phase, while the remaining small part of the rock salt phase will continue to remain, at this time, this part of the rock salt phase does not contain lithium, that is, there are lithium vacancy defects, thereby forming a high-nickel positive electrode material having a layered phase with a space group of R-3m and a rock salt phase with a space group of Fm-3m, and both phases are distributed in the bulk phase structure and the surface structure of the high-nickel positive electrode material.

[0061] Therefore, in the preparation method of the high-nickel positive electrode material of the present application, by controlling the molar ratio of the lithium source to the transition metal hydroxide precursor and the specific conditions of step sintering, the generation ratio and distribution of the rock salt phase can be regulated, so that lithium vacancy defects exist in the rock salt phase, a high-nickel positive electrode material having a layered phase and a rock salt phase is formed, and both phases are distributed in the bulk phase structure and the surface structure of the high-nickel positive electrode material; at the same time, the growth of primary particles can also be inhibited, so that the size of the primary particles is within hundreds of nanometers, thereby making the high-nickel positive electrode material have high specific capacity and rate performance.

[0062] Alternatively, the transition metal hydroxide precursor has a molecular formula of Ni x Mn y M z (OH)2, wherein 0.9 < x < 1, 0 < y < 0.1, x + y + z = 1, M is selected from at least one of Co, Al, Ti, Mg, Zr, Nb, Ta, W, Mo, Ce, La, Y, Sb, Zn, Sr, further, 0.9 < x < 1, 0 < y < 0.05.

[0063] In step S1, the preparation method of the transition metal hydroxide precursor can be hydrothermal method, coprecipitation method or electrochemical deposition method.

[0064] It is considered that the coprecipitation method can obtain spherical secondary particles formed by agglomeration of needle-shaped or block-shaped primary particles by controlling crystallization, the particle surface is smooth, the particle size distribution is uniform, the tap density is high, and the raw materials are uniformly distributed in the crystal lattice, and the material has fewer impurities, therefore, the present application preferably adopts the coprecipitation method.

[0065] Optionally, the co-precipitation method comprises:

[0066] S11, mixing a nickel source, a manganese source, an M source and water to prepare a mixed solution, wherein the M source is selected from a compound containing at least one of Co, Al, Ti, Mg, Zr, Nb, Ta, W, Mo, Ce, La, Y, Sb, Zn, Sr;

[0067] S12, mixing the mixed solution, a precipitant solution and a complexing agent solution, and performing a co-precipitation reaction under a protective atmosphere, and then performing aging, filtering, washing and drying to obtain a transition metal hydroxide precursor.

[0068] In step S11, the concentration of the mixed solution is 1 mol / L-3 mol / L, and the concentration of the mixed solution refers to the sum of the concentrations of the nickel source, the manganese source and the M source in the mixed solution.

[0069] Optionally, the nickel source is selected from at least one of nickel sulfate, nickel chloride, nickel acetate or nickel nitrate, the manganese source is selected from at least one of manganese sulfate, manganese chloride, manganese acetate or manganese nitrate, and the M source is selected from at least one of cobalt sulfate, cobalt chloride, cobalt acetate or cobalt nitrate.

[0070] In step S12, the reaction temperature is controlled to be 50°C-55°C, the pH value of the reaction is controlled to be 11.5-12.5, the protective atmosphere is selected from an inert gas atmosphere, and the stirring speed is controlled to be 600 rpm-1000 rpm, so that the components can be fully co-precipitated.

[0071] Optionally, the concentration of the precipitant solution is 2 mol / L-6 mol / L, and the precipitant solution is selected from a sodium hydroxide solution.

[0072] Optionally, the concentration of the complexing agent solution is 2 mol / L-6 mol / L, and the complexing agent solution is selected from ammonia water.

[0073] In this application, by adjusting the reaction conditions of the co-precipitation method and the concentrations of the components, the transition metal hydroxide precursor Ni x Mn y M z (OH)2can be better formed, and the molar relationship of x, y and z in the molecular formula can be better controlled.

[0074] In an embodiment, the mixed solution, the precipitant solution and the complexing agent solution are mixed in a reaction kettle and co-precipitated under a protective atmosphere.

[0075] In an embodiment, the protective atmosphere is selected from an inert gas atmosphere and / or a nitrogen atmosphere.

[0076] In step S2, the lithium source is selected from lithium hydroxide.

[0077] In an embodiment, the specific steps of the step-by-step sintering include: first, heating to 450-650℃ at a heating rate of 1-5℃ / min, and sintering for 8-16h; then, heating to 700-800℃, and sintering for 10-16h.

[0078] In addition, the application also provides a positive electrode sheet prepared by using the high-nickel positive electrode material as described above.

[0079] In addition, the application also provides a positive electrode sheet prepared by using the high-nickel positive electrode material as described above.

[0080] In the following, the high-nickel positive electrode material, the preparation method and application thereof will be further described through the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be obtained by purchase.

[0081] Example 1

[0082] According to the stoichiometric ratio of the Ni 0.9 Mn 0.05 Co 0.05 (OH)2precursor, nickel sulfate, manganese sulfate, cobalt sulfate and deionized water are prepared into a mixed salt solution with a concentration of 2mol / L, sodium hydroxide and deionized water are prepared into a precipitant solution with a concentration of 3mol / L, and concentrated ammonia and deionized water are prepared into a complexing agent solution with a concentration of 4mol / L; then the mixed salt solution, the precipitant solution and the complexing agent solution are slowly added into a reaction kettle and a coprecipitation reaction is carried out under a nitrogen atmosphere, wherein the reaction temperature is 50℃ and the stirring speed is 800rpm; after the reaction is completed, aging, filtration, washing and drying are carried out to obtain the Ni 0.9 Mn 0.05 Co 0.05 (OH)2precursor.

[0083] Lithium hydroxide and the Ni 0.9 Mn 0.05 Co 0.05 (OH)2precursor are mixed, wherein the lithium hydroxide and the Ni 0.9 Mn 0.05 Co 0.05The molar ratio of the (OH)2precursor is 0.95:1, and then step sintering is carried out in a box furnace in an oxygen atmosphere, wherein the temperature is raised to 550 ℃ at a temperature raising rate of 2 ℃ / min, and then sintered for 10 h, and then the temperature is raised to 720 ℃, and then sintered for 12 h, to obtain a high-nickel positive electrode material with a molecular formula of Li 0.95 Ni 0.9 Mn 0.05 Co 0.05 O2.

[0084] The high-nickel positive electrode material of Example 1 is tested by an X-ray diffractometer to obtain an XRD ray spectrum, as shown in FIG. 1. As can be seen from FIG. 1, in the X-ray diffraction pattern of the high-nickel positive electrode material of Example 1, there is a (110) L crystal face (i.e., (110) crystal face) characteristic diffraction peak belonging to the layered phase; the characteristic diffraction peak existing in the range of 15.18° is a single peak, which is composed of (006) L / (102) L crystal face (i.e., (006) / (102) crystal face) characteristic diffraction peak and (111) RS crystal face (i.e., (111) crystal face) characteristic diffraction peak belonging to the rock salt phase; there is a characteristic diffraction peak existing in the range of 17.52°, which is composed of (104) L crystal face (i.e., (104) crystal face) characteristic diffraction peak and (200) RS crystal face (i.e., (200) crystal face) characteristic diffraction peak belonging to the rock salt phase; the characteristic diffraction peak existing in the range of 24.88° is a single peak, which is composed of (108) L / (110) L crystal face (i.e., (108) / (110) crystal face) characteristic diffraction peak and (220) RS crystal face (i.e., (220) crystal face) characteristic diffraction peak belonging to the rock salt phase. Therefore, the high-nickel positive electrode material of Example 1 of the present application has the rock salt phase and the layered phase distributed in the bulk structure and the surface structure.

[0085] According to transmission electron microscope detection, the mass fraction of the rock salt phase in the surface structure of the high-nickel positive electrode material of Example 1 of the present application is less than the mass fraction of the rock salt phase in the bulk structure of the high-nickel positive electrode material.

[0086] Example 2

[0087] Example 2 is compared with Example 1, and the difference is only that the molar ratio of the (OH)2precursor is 1:1. 0.9 Mn 0.05 Co 0.05With a molar ratio of (OH)₂ precursor of 0.97:1 and all other conditions being the same, a molecular formula of Li was obtained. 0.97 Ni 0.9 Mn 0.05 Co 0.05 O2 high-nickel cathode material.

[0088] The morphology and structure of the high-nickel cathode material of Example 2 were tested using scanning electron microscopy (SEM). The test results are shown in Figures 2 and 3, where the SEM images are magnified at 1000x and 30000x, respectively. As can be seen from Figures 2 and 3, the high-nickel cathode material of Example 2 is a secondary microsphere formed by the stacking of primary particles. The particle size of the primary particles is approximately 85 nm, and the median particle size of the secondary microspheres is approximately 9.5 μm.

[0089] Example 3

[0090] Example 3 differs from Example 1 only in the amount of lithium hydroxide and Ni. 0.9 Mn 0.05 Co 0.05 With a molar ratio of (OH)₂ precursor of 0.93:1 and all other conditions being the same, a molecular formula of Li was obtained. 0.93 Ni 0.9 Mn 0.05 Co 0.05 O2 high-nickel cathode material.

[0091] Example 4

[0092] The only difference between Example 4 and Example 1 is that Example 4 first raises the temperature to 450°C at a heating rate of 2°C / min, holds it at that temperature for sintering for 15 hours, and then raises the temperature to 700°C and holds it at that temperature for sintering for 13 hours. All other conditions are the same, yielding a product with the molecular formula Li. 0.95 Ni 0.9 Mn 0.05 Co 0.05 O2 high-nickel cathode material.

[0093] Example 5

[0094] The only difference between Example 5 and Example 1 is that Example 5 first raises the temperature to 630°C at a heating rate of 2°C / min, holds it at that temperature for 8 hours, and then raises the temperature to 780°C and holds it at that temperature for 10 hours. All other conditions are the same, yielding a product with the molecular formula Li. 0.95 Ni 0.9 Mn 0.05 Co 0.05 O2 high-nickel cathode material.

[0095] Example 6

[0096] The only difference between Example 6 and Example 1 is that, according to Ni 0.9 Mn0.05 A1 0.05 The stoichiometric ratio of the (OH)₂ precursor was determined by preparing a 2.5 mol / L mixed salt solution using nickel sulfate, manganese sulfate, aluminum sulfate, and deionized water; a 4 mol / L precipitant solution using sodium hydroxide and deionized water; and a 4 mol / L complexing agent solution using concentrated ammonia and deionized water. The mixed salt solution, precipitant solution, and complexing agent solution were then slowly added to a reaction vessel and a co-precipitation reaction was carried out under a nitrogen atmosphere at 50°C and a stirring speed of 800 rpm. After the reaction, the mixture was aged, filtered, washed, and dried to obtain Ni. 0.9 Mn 0.05 Co 0.05 (OH)₂ precursor; all other conditions are the same, yielding a product with the molecular formula Li. 0.95 Ni 0.9 Mn 0.05 A1 0.05 O2 high-nickel cathode material.

[0097] Example 7

[0098] The only difference between Example 7 and Example 1 is that, according to Ni 0.9 Mn 0.05 Ti 0.05 The stoichiometric ratio of the (OH)₂ precursor was determined by preparing a mixed salt solution with a concentration of 2.5 mol / L using nickel sulfate, manganese sulfate, titanium sulfate, and deionized water, while keeping all other conditions constant. This yielded a solution with the molecular formula Li. 0.95 Ni 0.9 Mn 0.05 Ti 0.05 O2 high-nickel cathode material.

[0099] Example 8

[0100] The only difference between Example 8 and Example 1 is that, according to Ni 0.9 Mn 0.03 Nb 0.07 The stoichiometric ratio of the (OH)₂ precursor was determined by preparing a 2 mol / L mixed salt solution using nickel sulfate, manganese sulfate, niobium sulfate, and deionized water, with all other conditions remaining the same, to obtain a solution with the molecular formula Li. 0.93 Ni 0.9 Mn 0.03 Nb 0.07 O2 high-nickel cathode material.

[0101] Example 9

[0102] The only difference between Example 9 and Example 1 is that, according to Ni 0.95 Mn 0.03 Co 0.02stoichiometric ratio of the LiNi0.8Mn0.1Co0.1(OH)2 precursor, and the rest of the conditions were the same, a mixed salt solution with a concentration of 2 mol / L was prepared from nickel sulfate, manganese sulfate, cobalt sulfate and deionized water, and a high-nickel positive electrode material with a molecular formula of LiNi0.8Mn0.1Co0.1O2was obtained. 0.95 Ni 0.95 Mn 0.03 Co 0.02 O2.

[0103] Example 10

[0104] Example 10 is only different from Example 1 in that the molar ratio of the LiNi0.8Mn0.1Co0.1(OH)2 precursor is 0.99:1, and the rest of the conditions are the same, a high-nickel positive electrode material with a molecular formula of LiNi0.8Mn0.1Co0.1O2is obtained. 0.9 Mn 0.05 Co 0.05 O2. 0.99 Ni 0.9 Mn 0.05 Co 0.05 O2.

[0105] Comparative Example 1

[0106] Comparative Example 1 is only different from Example 1 in that the molar ratio of the LiNi0.8Mn0.1Co0.1(OH)2 precursor is 1.02:1, and the rest of the conditions are the same, a high-nickel positive electrode material with a molecular formula of LiNi0.8Mn0.1Co0.1O2is obtained. 0.9 Mn 0.05 Co 0.05 O2. 1.02 Ni 0.9 Mn 0.05 Co 0.05 O2.

[0107] The high-nickel positive electrode material of Comparative Example 1 was tested by an X-ray diffractometer to obtain an XRD ray spectrum and an XRD refinement result, as shown in FIG. 4. As can be seen from FIG. 4, the high-nickel positive electrode material of Comparative Example 1 only contains a layered phase.

[0108] Comparative Example 2

[0109] Comparative Example 2 is only different from Example 1 in that the molar ratio of the LiNi0.8Mn0.1Co0.1(OH)2 precursor is 0.8:1, and the rest of the conditions are the same, a high-nickel positive electrode material with a molecular formula of LiNi0.8Mn0.1Co0.1O2is obtained. 0.9 Mn 0.05 Co 0.05 O2. 0.8 Ni 0.9 Mn 0.05 Co 0.05 O2.

[0110] Comparative Example 3

[0111] Comparative Example 3 is the same as Example 1 except that the step sintering is not performed in the oxygen atmosphere box furnace, i.e., directly heated to 720℃ at a heating rate of 2℃ / min, and sintered for 16h, to obtain a high-nickel positive electrode material with a molecular formula of Li 0.95 Ni 0.9 Mn 0.05 Co 0.05 O2.

[0112] The high-nickel positive electrode materials prepared in Examples 1 to 10 and Comparative Examples 1 to 3 are used as positive electrode sheets to assemble button cells.

[0113] The method for assembling the button cell is as follows: the high-nickel positive electrode material, conductive carbon black, and polyvinylidene fluoride are mixed in a mass ratio of 95:3:2 in a nitrogen methyl pyrrolidone solvent under the conditions of 25℃ and normal pressure (0.1MPa) to obtain a positive electrode slurry, which is uniformly coated on the surface of a carbon-coated aluminum foil, and then dried and cold-pressed to obtain a positive electrode sheet containing a positive electrode active layer with a cold-pressed thickness of 100; then the positive electrode sheet, lithium sheet, separator, and electrolyte are assembled into a button cell in a button cell box, wherein the separator is polyethylene, the electrolyte is LiPF6, and the solvent is EC / DMC.

[0114] Performance test of the button cell prepared above:

[0115] The cycle performance test is performed at a test temperature of 25℃, a charge-discharge rate of 0.2C, and a voltage range of 2.5 to 4.3V, and the test method is as follows: 0.2C-rate constant current charging to a voltage of 4.3V (cut-off voltage), then constant voltage charging under the cut-off voltage condition until the current is less than 0.05C, at which time the charging capacity is recorded as the first cycle charging capacity, then standing for 5min, and then 0.2C-rate constant current discharging to a voltage of 2.5V, the discharging capacity at this time is recorded as the first cycle discharge specific capacity, i.e., the initial capacity; then 0.5C-rate charging and discharging for 100 cycles, and the capacity of the first 100 cycles divided by the capacity of the first cycle, i.e., the capacity retention rate of 100 cycles, and the test results are shown in Table 1.

[0116] Primary particle size test:

[0117] The morphology and structure of the high-nickel positive electrode materials of the above examples and comparative examples are tested by scanning electron microscopy, and the size of 100 primary particles is tested in the electron microscope image, and the average value is obtained, i.e., the particle size of the primary particles, and the test results are shown in Table 1.

[0118] Secondary microsphere median particle size test:

[0119] The test is performed according to GBT19077.1-2016, and the test results are shown in Table 1.

[0120] Distribution test of phase structure:

[0121] The high-nickel positive electrode materials prepared in the above examples and the comparative example were tested by using an X-ray diffractometer, and the XRD spectra of the high-nickel positive electrode materials were obtained. The XRD spectra of the high-nickel positive electrode material prepared in Example 1 is shown in FIG. 1, and the XRD spectra of the high-nickel positive electrode materials prepared in the other examples are similar to that of Example 1. The XRD spectra of the high-nickel positive electrode materials prepared in the above examples and the comparative example all satisfy the following conditions: in the X-ray diffraction pattern of the high-nickel positive electrode material, there exists a characteristic diffraction peak of a (110) crystal face in the range of 14°-15°, the characteristic diffraction peak belongs to the layered phase; there exists a characteristic diffraction peak in the range of 15°-15.5°, the characteristic diffraction peak is a single peak, the single peak is composed of a (006) crystal face characteristic diffraction peak and a (102) crystal face characteristic diffraction peak both belonging to the layered phase; there exists a characteristic diffraction peak in the range of 17.4°-17.8°, the characteristic diffraction peak is composed of a (104) crystal face characteristic diffraction peak belonging to the layered phase and a (200) crystal face characteristic diffraction peak belonging to the rock salt phase; there exists a characteristic diffraction peak in the range of 24.6°-25.2°, the characteristic diffraction peak is a single peak, the single peak is composed of a (108) crystal face characteristic diffraction peak belonging to the layered phase and a (110) crystal face characteristic diffraction peak belonging to the rock salt phase; and there exists a characteristic diffraction peak in the range of 27.4°-27.8°, the characteristic diffraction peak is composed of a (220) crystal face characteristic diffraction peak belonging to the rock salt phase. L L L RS L RS L L RS Therefore, the high-nickel positive electrode materials prepared in Examples 2-10 all have the rock salt phase and the layered phase distributed in the bulk phase structure and the surface structure of the high-nickel positive electrode materials.

[0122] In addition, the high-nickel positive electrode materials prepared in Examples 1-10 were detected by using a transmission electron microscope, and the high-nickel positive electrode materials prepared in the examples all satisfy the following condition: the mass fraction of the rock salt phase in the surface structure of the high-nickel positive electrode material is less than the mass fraction of the rock salt phase in the bulk phase structure of the high-nickel positive electrode material.

[0123] Specifically, the high-nickel positive electrode materials of the above examples and the comparative example were tested by using an X-ray diffractometer, and the XRD spectra and the XRD refinement data were obtained, and the phase structure (i.e., the type of phase) of the high-nickel positive electrode material, the mass fraction of each phase in the high-nickel positive electrode material, and the chemical formula of the rock salt phase in the high-nickel positive electrode material were obtained, and the test results are shown in Tables 1 and 2. ​​​​​​​​

[0124] Table 1

[0125] In Table 1, A in the chemical formula of the rock salt phase represents a transition metal element, that is, A = Ni + Mn + Co.

[0126] As can be seen from Table 1, the molar ratio of lithium element to transition metal element A in the rock salt phase in the high-nickel positive electrode material prepared in Examples 1-10 is less than 1, and lithium vacancy defects exist in the rock salt phase.

[0127] Table 2

[0128] As can be seen from Table 2, compared with Comparative Examples 1-3, the high-nickel positive electrode material of the present application Examples 1-10, by controlling the ratio of lithium source and transition metal precursor and controlling the specific conditions of step sintering, under the synergistic effect of the two, the high-nickel positive electrode material can have high specific capacity, at the same time has excellent cycle performance and lower cost.

[0129] Among them, compared with Example 1, the specific capacity and capacity retention rate of the high-nickel positive electrode material of Comparative Example 3 are poor, and the voltage decay is fast, the reason is that due to the use of step sintering, the mass fraction of the rock salt phase of the prepared high-nickel positive electrode material is low, and there is also a lack of lithium state in the layered phase, so that the structural stability of the high-nickel positive electrode material is poor.

[0130] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0131] The above-described embodiments only express several implementation manners of the present application, the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A high-nickel positive electrode material, characterized by, The high-nickel positive electrode material has a phase including a layered phase and a rock salt phase, the layered phase has a space group of R-3m, the rock salt phase has a space group of Fm-3m, the mass fraction of the rock salt phase in the high-nickel positive electrode material is 3%-23%, and lithium vacancy defects exist in the rock salt phase. 2.The high-nickel cathode material of claim 1, wherein, The high-nickel positive electrode material has a molecular formula of Li m Ni x Mn y M z O2, wherein 0.9 3.The high-nickel cathode material of claim 1, wherein, The high-nickel positive electrode material is a secondary microsphere formed by accumulation of primary particles, the particle size of the primary particles is 50 nm-100 nm, and the median particle size of the secondary microsphere is 5 μm-20 μm. 4.The high-nickel cathode material of claim 1, wherein, The rock salt phase is distributed in the bulk structure and the surface structure of the high-nickel positive electrode material, and the mass fraction of the rock salt phase in the bulk structure of the high-nickel positive electrode material is greater than the mass fraction of the rock salt phase in the surface structure of the high-nickel positive electrode material. 5.The high-nickel cathode material of claim 1, wherein, The crystal structure of the high-nickel positive electrode material satisfies at least one of the following conditions: (1) the X-ray diffraction pattern of the high-nickel positive electrode material has a (110) crystal face characteristic diffraction peak in the range of 14°-15°; (2) the characteristic diffraction peak existing in the range of 15°-15.5° in the X-ray diffraction pattern of the high-nickel positive electrode material is a single peak; (3) the X-ray diffraction pattern of the high-nickel positive electrode material has a characteristic diffraction peak in the range of 17.4°-17.8°; (4) the characteristic diffraction peak existing in the range of 24.6°-25.2° in the X-ray diffraction pattern of the high-nickel positive electrode material is a single peak.

6. A method of producing the high-nickel positive electrode material according to any one of claims 1 to 5, characterized by, The method comprises the steps of: providing a transition metal hydroxide precursor; mixing a lithium source and the transition metal hydroxide precursor, and then performing step-by-step sintering in an oxygen atmosphere to obtain a high-nickel positive electrode material, wherein the molar ratio of the lithium source to the transition metal hydroxide precursor is R, 0.9 7. The method for preparing the high-nickel cathode material according to claim 6, characterized in that, The molecular formula of the transition metal hydroxide precursor is Ni x Mn y M z (OH)2, wherein 0.9≤x<1, 0 M is selected from at least one of Co, Al, Ti, Mg, Zr, Nb, Ta, W, Mo, Ce, La, Y, Sb, Zn, Sr.

8. The method for preparing the high-nickel cathode material according to claim 7, characterized in that, The preparation method of the transition metal hydroxide precursor adopts a coprecipitation method, and the coprecipitation method comprises the steps of: mixing a nickel source, a manganese source, an M source, and water to prepare a mixed solution, wherein the M source is selected from at least one compound containing Co, Al, Ti, Mg, Zr, Nb, Ta, W, Mo, Ce, La, Y, Sb, Zn, and Sr; mixing the mixed solution, a precipitant solution, and a complexing agent solution, and performing a coprecipitation reaction under a protective atmosphere, and then performing aging, filtering, washing, and drying to obtain the transition metal hydroxide precursor.

9. The method for preparing the high-nickel cathode material according to claim 8, characterized in that, In the steps of the coprecipitation method, at least one of the following conditions is satisfied: (1) the reaction temperature is controlled to be 50°C-55°C, the reaction pH value is controlled to be 11.5-12.5, the protective atmosphere is selected from an inert gas atmosphere, and the stirring speed is controlled to be 600 rpm-1000 rpm; (2) the concentration of the mixed solution is 1 mol / L-3 mol / L; (3) the concentration of the precipitant solution is 2 mol / L-6 mol / L, and the precipitant solution is selected from a sodium hydroxide solution; (4) the concentration of the complexing agent solution is 2-6 mol / L, and the complexing agent solution is selected from ammonia; (5) the nickel source is selected from at least one of nickel sulfate, nickel chloride, nickel acetate or nickel nitrate, the manganese source is selected from at least one of manganese sulfate, manganese chloride, manganese acetate or manganese nitrate, and the M source is selected from at least one of cobalt sulfate, cobalt chloride, cobalt acetate or cobalt nitrate.

10. A positive electrode sheet prepared by using the high-nickel positive electrode material according to any one of claims 1 to 5.

11. A lithium ion battery prepared by using the positive electrode sheet according to claim 10.

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