Ultrahigh nickel layered oxide positive electrode material and application thereof

Abstract

The invention relates to the technical field of lithium ion battery positive electrode materials, in particular to an ultrahigh nickel layered oxide positive electrode material and application thereof. The general formula of the ultrahigh nickel layered oxide positive electrode material provided by the invention is LiNix (M1, M2... Mn) 1-xO2, M1, M2... Mn are doping elements, n is the number of the doping elements, and the numerical value of n should meet the requirement that the mixing entropy of the doping elements is greater than or equal to a gas constant. The doping elements M1, M2... Mn should meet the following conditions: (1) at least one doping element is an element with oxygen bond energy greater than nickel oxygen bond energy, (2) at least one doping element is a microstructure improvement element, (3) at least one doping element is a bulk phase doping element with an ion radius less than 0.076 nm, and (4) at least one doping element is a bulk phase doping element with an ion radius less than 0.076 nm. And (4) at least one doping element is a surface gradient doping element of which the ion radius is greater than 0.076 nm.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials for lithium-ion batteries, and particularly to a high-nickel layered oxide cathode material and its use. Background Art

[0002] Due to reasons such as limited driving range, long charging time, low service life, and high cost of lithium-ion battery technology, its market share in the automotive industry is still lower than expected. Therefore, it is urgent to develop lithium-ion batteries with more excellent comprehensive performance. As an important component of lithium-ion batteries, the cathode material directly determines the high or low energy density of the battery. The ternary layered lithium nickel cobalt manganese oxide cathode material has a higher discharge specific capacity, higher energy density, and lower material cost compared with the spinel lithium manganate and olivine lithium iron phosphate cathode materials, and has become the most promising next-generation lithium-ion battery cathode material.

[0003] How to increase the nickel content, reduce the cobalt content or achieve a cobalt-free content to improve its cost performance has become a current research hotspot. Although cobalt-free or even cobalt-free high-nickel (nickel content greater than or equal to 90%) layered oxide cathode materials have attractive reversible capacities, they have problems such as deterioration of the electrode-electrolyte interface, structural deterioration, and thermal runaway, and have poor cycle stability, which seriously hinders their wide application. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-nickel layered oxide cathode material and its use. The high-nickel layered oxide cathode material provided by the present invention does not contain cobalt and has excellent cycle stability.

[0005] To achieve the above purpose, on the one hand, the present invention provides a high-nickel layered oxide cathode material, whose general formula is LiNi x (M 1 ,M 2 ……M n ) 1-x O 2 , where 0.9 ≤ x ≤ 0.98, M 1 , M 2 ……M n are doping elements, n is the number of doping elements, and the value of n should satisfy that the mixing entropy of the doping elements is greater than or equal to the gas constant R requirements, M 1 , M 2 ……M n The doping elements should meet the following conditions: (1) At least one doping element is an element with a bond energy with oxygen greater than the nickel-oxygen bond energy, (2) At least one doping element is a microstructure improvement element, (3) At least one doping element is a bulk doping element with an ionic radius less than 0.076 nm, and (4) At least one doping element is a surface gradient doping element with an ionic radius greater than 0.076 nm.

[0006] In some embodiments of the present invention, the formula for calculating the mixing entropy of the doping elements is: , where ΔS mix is the mixing entropy, R is the gas constant, R has a value of 8.314 J / K, i is the i th doping element, n is the number of doping elements, C i is the i th atomic percentage of the element.

[0007] In some embodiments of the present invention, the elements with a bond energy with oxygen greater than that of the nickel-oxygen bond are Sn, Ta, Sr, Ti, W, Y, Nd, Mo, La, Ge, Er, Ce, B, Al, Si, Zr, and Nb.

[0008] In some embodiments of the present invention, the microstructure-improving elements are Ti, Nb, Ta, Mo, W, B, and Ga.

[0009] In some embodiments of the present invention, the bulk doping elements are B, Si, Mn, Ge, Al, V, W, Ti, Ga, Ta, Fe, Mo, Nb, Sn, Mg, and Zn.

[0010] In some embodiments of the present invention, the surface gradient doping elements are Er, Y, Ca, Na, La, Sr, and Ce.

[0011] In some embodiments of the present invention, the atomic ratios of the doping elements are the same, 0.94 ≤ x ≤ 0.96.

[0012] In some embodiments of the present invention, the doping elements are selected from the elements with a bond energy with oxygen greater than that of the nickel-oxygen bond, the microstructure-improving elements, the bulk doping elements, and the surface gradient doping elements.

[0013] In some embodiments of the present invention, the ultra-high nickel layered oxide cathode material is specifically LiNi 0.96 (Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 )O 2 、LiNi 0.96(Zn 0.01 Al 0.01 Nb 0.01 Y 0.01 ) 2 、LiNi 0.94 (Zn 0.01 Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 Y 0.01 ) 2 or LiNi 0.96 (Mg 0.01 Al 0.01 Mo 0.01 Ca 0.01 ) 2 , where the ratio of each element is the atomic ratio.

[0014] Another aspect of the present invention provides use of the ultra-high nickel layered oxide positive electrode material described in any of the above technical solutions in positive electrode materials for lithium-ion batteries.

[0015] The present invention utilizes a medium-entropy or high-entropy element doping strategy (i.e., the mixing entropy of the doping element is greater than or equal to the gas constant) and a microstructure engineering strategy (introducing a high-price element as a micromorphology improvement element to improve the oriented growth of primary particles during the material synthesis process) to obtain a cobalt-free ultra-high nickel layered oxide positive electrode material. Specifically, the bulk phase doping element with an ion radius smaller than the lithium ion radius is dispersed inside the structure, while the surface gradient doping element with a larger ion radius is distributed from the surface to the inside, and plays a role in stabilizing the structure during the lithium ion insertion and extraction process, whether in the bulk phase or the surface layer; in addition, through the bond energy between some doping elements (elements with a bond energy greater than the nickel-oxygen bond energy with oxygen) and oxygen elements that is stronger than the nickel-oxygen bond, an indestructible "oxygen clamping site" is established to prevent oxygen from escaping; the micromorphology improvement element can reduce the surface energy of the (003) crystal plane, thereby inducing the radial arrangement of primary particles, and more single crystal grain boundaries and special radial arrangement structures can provide more internal space and stress release paths for effectively mitigating phase changes. This improves the cycle stability of the ultra-high nickel layered oxide positive electrode material and exhibits excellent electrochemical performance. The results of the examples of the present invention show that the ultra-high nickel layered oxide positive electrode material provided by the present invention is α-NaFeO 2 The hexagonal layered structure has good mechanical strength and excellent thermal stability. After experiencing high temperature, the structure can be reversibly restored. The capacity retention rate after 100 cycles of charge and discharge is still maintained at more than 90%, and after 300 cycles of charge and discharge, the secondary particles of the positive electrode material still maintain structural integrity, indicating that the ultra-high nickel layered oxide positive electrode material provided by the present invention has excellent cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features, and advantages of the present invention will be apparent from the following description of the preferred embodiments and the accompanying drawings that illustrate the gist of the present invention and its use. In the accompanying drawings: Figure 1 Scanning electron microscope (SEM) images of the positive electrode materials obtained in Examples 1-5 and Comparative Example 1, where the scale in the figures is 1 μm for all.

[0017] Figure 2 Graph of pressure-displacement for the positive electrode materials obtained in Example 1 and Comparative Example 1.

[0018] Figure 3 X-ray diffraction (XRD) patterns of the positive electrode materials obtained in Examples 1-5 and Comparative Example 1.

[0019] Figure 4 Graph of the results of high-temperature in-situ XRD tests for the positive electrode materials obtained in Example 1 and Comparative Example 1, where a is the in-situ XRD pattern of the positive electrode materials obtained in Example 1 and Comparative Example 1 at 50°C, heated to 500°C, and cooled to 50°C; b is the graph of the change in the interplanar spacing during heating from 50°C to 500°C.

[0020] Figure 5 Graph of the change in voltage over time when the batteries using the positive electrode materials obtained in Example 1 and Comparative Example 1 are at rest at 25°C in the charged state.

[0021] Figure 6 Graph of the first charge-discharge curves of the batteries using the positive electrode materials obtained in Examples 1-5 and Comparative Example 1 at a 0.1 C rate.

[0022] Figure 7 First-week current-voltage curves of the positive electrode materials obtained in Example 1 and Comparative Example 1.

[0023] Figure 8 Graph of the peak displacement changes of the (003), (101), and (104) peaks during the first-week charge-discharge process of the positive electrode materials obtained in Example 1 and Comparative Example 1, where (a), (b), and (c) are the peak displacement change curves of the (003), (101), and (104) peaks in sequence.

[0024] Figure 9 Graph of charge-discharge cycle curves of the batteries using the positive electrode materials obtained in Example 1 and Comparative Example 1 at different cut-off voltages at a 1 C rate, where the cut-off voltages of the curves in (a), (b), and (c) are 4.3 V, 4.4 V, and 4.5 V in sequence.

[0025] Figure 10 Graph of charge-discharge cycle curves of the batteries using the positive electrode materials obtained in Example 1 and Comparative Examples 1-4 at a 1 C rate.

[0026] Figure 11 SEM images of the cathode materials of Example 1 and Comparative Example 1 after 300 cycles of charge and discharge at a rate of 1 C. Among them, a is the SEM image of the cathode material of Comparative Example 1 and the enlarged view of some secondary particles, and b is the SEM image of the cathode material of Example 1 and the enlarged view of some secondary particles. The scale bar in the figure is 1 μm for both. Detailed implementation manners

[0027] The present invention will be described below through specific implementation examples. Those skilled in the art can understand that the following specific implementation examples are only for the purpose of illustration and do not limit the scope of the present invention in any way. In addition, in the following implementation examples, unless otherwise specified, the reagents and equipment used are commercially available. If the specific processing conditions and processing methods are not clearly described in the subsequent implementation examples, the conditions and methods known in the art can be used for processing.

[0028] On the one hand, the present invention provides a high-nickel layered oxide cathode material with the general formula LiNi x (M 1 ,M 2 ……M n ) 1-x O 2 , where 0.9 ≤ x ≤ 0.98, M 1 , M 2 ……M n are doping elements, n is the number of doping elements, and the value of n should satisfy the requirement that the mixing entropy of the doping elements is greater than or equal to the gas constant R . The doping elements M 1 , M 2 ……M n should meet the following conditions: (1) At least one doping element is an element with a bond energy with oxygen greater than the nickel-oxygen bond energy, (2) At least one doping element is a microstructure improvement element, (3) At least one doping element is a bulk doping element with an ionic radius less than 0.076 nm, and (4) At least one doping element is a surface gradient doping element with an ionic radius greater than 0.076 nm.

[0029] In the present invention, a cobalt-free ultra-high nickel layered oxide cathode material is obtained by using a medium-entropy or high-entropy element doping strategy (i.e., the mixing entropy of the doping elements is greater than or equal to the gas constant) and a microstructure engineering strategy (incorporating a high-valence element as a microstructure-improving element to improve the oriented growth of primary particles during the material synthesis process). By maintaining structural integrity, suppressing and delaying harmful phase transitions, improving charge transport kinetics, reducing the incidence of adverse reactions, and establishing an indestructible "oxygen clamping site", superior thermal and chemical stability and a longer cycle life within a wide voltage range are obtained.

[0030] In the present invention, x in the general formula of the ultra-high nickel layered oxide cathode material satisfies 0.9 ≤ x ≤ 0.98, and specifically can be 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, and any value between the above values. In some embodiments of the present invention, 0.94 ≤ x ≤ 0.96.

[0031] In the present invention, n in the general formula of the ultra-high nickel layered oxide cathode material is the number of doping elements, and the value of n is determined by meeting the requirements of the aforementioned mixing entropy. In the present invention, when the above requirements are met, n ≥ 3, and specifically can be any integer such as 3, 4, 5, 6, 7, etc.

[0032] In the present invention, the mixing entropy of the doping elements is greater than or equal to the gas constant ( R ), for example, specifically can be 1.386 R , 1.79 R , etc. In the present invention, the calculation formula for the mixing entropy of the doping elements is: , where ΔS mix is the mixing entropy, R is the gas constant, R The value of i is 8.314 J / K, i is the C i th doping element, n is the number of doping elements, i is the atomic percentage of the

[0033] In the present invention, the elements satisfying conditions (1)-(4) among the doping elements may be the same element or different elements, as long as the types of doping elements can satisfy conditions (1)-(4). For example, if the doping elements contain Nb, Nb belongs to both the element with a bond energy with oxygen greater than that of the nickel-oxygen bond, and the element for improving the microscopic morphology and the bulk doping element. Therefore, containing Nb can be considered to satisfy the three conditions of (1)-(3); another example is that the doping elements contain Al, Al belongs to both the element with a bond energy with oxygen greater than that of the nickel-oxygen bond and the bulk doping element. Therefore, containing Al can be considered to satisfy conditions (1) and (3).

[0034] In some embodiments of the present invention, the doping elements are selected from the elements with a bond energy with oxygen greater than that of the nickel-oxygen bond, the elements for improving the microscopic morphology, the bulk doping elements, and the surface gradient doping elements, where the elements with a bond energy with oxygen greater than that of the nickel-oxygen bond, the elements for improving the microscopic morphology, the bulk doping elements, and the surface gradient doping elements respectively correspond to the elements in the foregoing conditions (1)-(4); or rather, the doping elements are selected from Sn, Ta, Sr, Ti, W, Y, Nd, Mo, La, Ge, Er, Ce, B, Al, Si, Zr, Nb, Ta, Ga, Mn, V, Fe, Sn, Mg, Zn, Er, Y, Ca, Na, and Sr, but must simultaneously satisfy the foregoing conditions (1)-(4) and the requirement that the number of doping elements should satisfy the mixing entropy greater than or equal to the gas constant.

[0035] In some embodiments of the present invention, the elements with a bond energy with oxygen greater than that of the nickel-oxygen bond are Sn, Ta, Sr, Ti, W, Y, Nd, Mo, La, Ge, Er, Ce, B, Al, Si, Zr, and Nb. In the present invention, the elements with a bond energy with oxygen greater than that of the nickel-oxygen bond establish an indestructible "oxygen clamping site" to prevent oxygen from escaping. This stable framework can effectively inhibit the migration of oxygen anions in the bulk phase and increase the energy barrier for oxygen evolution on the surface, thereby ensuring the structural and interfacial stability of the ultra-high nickel oxide.

[0036] In some embodiments of the present invention, the elements for improving the microscopic morphology are Ti, Nb, Ta, Mo, W, B, and Ga. In the present invention, the elements for improving the microscopic morphology can reduce the surface energy of the (003) crystal plane, thereby inducing the radial arrangement of primary particles. More single crystal grain boundaries and special radial arrangement structures can provide more internal space and stress release paths for effectively alleviating the phase change.

[0037] In some embodiments of the present invention, the bulk doping elements are B, Si, Mn, Ge, Al, V, W, Ti, Ga, Ta, Fe, Mo, Nb, Sn, Mg, and Zn. In some embodiments of the present invention, the surface gradient doping elements are Er, Y, Ca, Na, La, Sr, and Ce. In the present invention, the bulk doping elements with an ionic radius smaller than that of lithium ions are dispersed inside the structure, while the surface gradient doping elements with a larger ionic radius are distributed in a gradient manner from the surface to the interior. Both in the bulk and on the surface, they play a role in stabilizing the structure during the insertion and extraction of lithium ions.

[0038] The present invention does not limit the proportion of the doping elements in the general formula, and it can be any proportion as long as it can meet the requirements of the aforementioned mixing entropy and conditions (1)-(4). In some embodiments of the present invention, the atomic ratios of the respective doping elements are the same.

[0039] In some embodiments of the present invention, the average particle size of the ultra-high nickel layered oxide cathode material is 3-8 μm.

[0040] As an illustrative example, the ultra-high nickel layered oxide cathode material can specifically be LiNi 0.96 (Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 )O 2 、LiNi 0.96 (Zn 0.01 Al 0.01 Nb 0.01 Y 0.01 )O 2 、LiNi 0.94 (Zn 0.01 Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 Y 0.01 )O 2 Or LiNi 0.96 (Mg 0.01 Al 0.01 Mo 0.01 Ca 0.01 )O 2 , where the proportion of each element is an atomic ratio.

[0041] The present invention also provides a preparation method for the ultra-high nickel layered oxide cathode material described in the above technical solution, including the following steps: Mix a precursor containing nickel and doping elements with lithium hydroxide in a proportion where lithium hydroxide is 2% in excess according to the stoichiometric ratio in the general formula, and then calcine in an oxygen atmosphere to obtain the ultra-high nickel layered oxide cathode material.

[0042] In the present invention, those skilled in the art can select a suitable hydroxide precursor containing nickel and doping elements according to needs.

[0043] In some embodiments of the present invention, the precursor containing nickel and doping elements is independently at least one of hydroxide, oxide, and acetate.

[0044] In some embodiments of the present invention, when the precursor containing nickel and doping elements is a hydroxide precursor, the hydroxide precursor containing nickel and doping elements is prepared by a coprecipitation method. The present invention does not limit the specific steps of the coprecipitation method. Those skilled in the art can select the specific steps according to needs, such as separately preparing salt solutions of nickel and doping elements, or directly preparing a mixed salt solution of nickel and doping elements, or separately preparing salt solutions of several of the metals and a mixed salt solution of the remaining metals, and then pumping them into a reaction kettle together with an alkali solution for coprecipitation reaction. Specifically, in some embodiments of the present invention, the salt solution of aluminum can be an ethanol solution of Al(OCH(CH 3 )C 2 H 5 ) 3 and C 5 H 8 O 2 (molar ratio 1:1); the salt solution of niobium can be an aqueous solution of C 4 H 4 NNbO 9 hydrate, the salt solution of yttrium can be a yttrium salt solution obtained by dissolving yttrium(III) chloride hexahydrate and citric acid in deionized water at a molar ratio of 1:2 and then adding ammonia water to adjust the pH value of the solution to 9.0; the salt solution of molybdenum can be an aqueous solution of (NH 4 ) 6 Mo 7 O 24 . In some embodiments of the present invention, the alkali solution is a clear liquid obtained by dissolving NaOH and NH 3 ·H 2 O (molar ratio 5:3 mol / L) in 2 L of deionized water; during the coprecipitation process, the pH of the reaction solution is controlled to 11.6, the temperature of the coprecipitation reaction is 50 - 51 °C, specifically it can be 50.5 °C; during the coprecipitation process, stirring is preferably maintained, and the present invention does not particularly limit the rotation speed of the stirring, as long as the reaction solution can be mixed evenly; the time of the coprecipitation reaction is 48 h. In some embodiments of the present invention, after the coprecipitation reaction is completed, the obtained reaction solution is filtered, and the obtained filter residue is washed and dried in sequence to obtain a hydroxide precursor of nickel and doping elements.

[0045] In some embodiments of the present invention, the concentration of the doping element should be determined according to the stoichiometry of the prepared sample. For example, for 1 mol of LiNi 0.96 (Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 )O 2 , the nickel-containing salt solution should be 0.96 mol, and the magnesium-containing salt solution should be 0.01 mol. This is implemented in all examples.

[0046] In some embodiments of the present invention, the precursor material selected should pass through a 400-mesh sieve.

[0047] In some embodiments of the present invention, the calcination is carried out in an oxygen atmosphere. The temperature is raised from room temperature to 480 °C, held for 5 h, and then raised to 700 - 760 °C, preferably 740 °C, and held for 10 h. In some embodiments of the present invention, the heating rate for raising the temperature to the calcination temperature is 5 °C / min.

[0048] The present invention also provides the use of the ultra-high nickel layered oxide cathode material according to any of the above technical solutions or the ultra-high nickel layered oxide cathode material prepared by the preparation method according to any of the above technical solutions in a lithium-ion battery cathode material.

[0049] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the drawings and examples. The examples of this application are only for illustration. All other examples obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

[0050] The mixed alkali solution used in the following examples is a clear liquid obtained by dissolving 10 mol of NaOH and 6 mol of NH 3 ·H 2 O in 2 L of deionized water. Example 1

[0051] The target product of this example is LiNi 0.96 (Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 )O 2 (abbreviated as NMANC), and the mixing entropy of the doping elements is 1.386 R , and the cathode material is prepared according to the following method: (1) Weigh nickel sulfate hexahydrate, magnesium chloride hexahydrate, and calcium chloride hexahydrate according to the stoichiometry of the target product and dissolve them in 1 L of deionized water to obtain a dark green liquid; Dissolve Al(OCH(CH 3 )C 2 H 5 ) 3 and C 5 H 8 O 2 (acetylacetone, molar ratio 1:1) in 0.1 L of ethanol, and stir evenly at 40 °C to obtain a slightly yellow liquid; Dissolve C 4 H 4 NNbO 9 hydrate in 0.1 L of deionized water to obtain a clear solution.

[0052] (2) Pump the above-obtained solution and the mixed alkali solution into a continuously stirred co-precipitation reactor through a peristaltic pump. At the same time, use an instrument pH automatic control system to adjust the pumping of the mixed alkali solution to maintain the pH of the reaction solution at 11.6, the temperature at 50.5 °C, and the rotation speed at 600 rpm. After 48 hours, the reaction ends. Filter the obtained reaction solution, and then wash and dry the obtained filter cake in sequence to obtain a hydroxide precursor.

[0053] (3) Grind the obtained hydroxide precursor and pass it through a 400-mesh sieve. Take the material under the sieve and mix it with lithium hydroxide monohydrate in a ratio where lithium hydroxide monohydrate is 2% in excess according to the stoichiometric ratio. Then, heat it to 480 °C at a rate of 5 °C / min in an oxygen atmosphere, hold it at 480 °C for 5 h, and then heat it to 740 °C at a rate of 5 °C / min and hold it at 740 °C for 10 h to obtain a high-nickel layered oxide cathode material NMANC. Example 2

[0054] According to the stoichiometric ratio, mix nickel hydroxide (400 mesh), lithium hydroxide monohydrate (lithium hydroxide monohydrate is 2% in excess), magnesium acetate tetrahydrate, calcium acetate monohydrate, Al(OH) 3 and Nb 2 O 5 and then heat it to 480 °C at a rate of 5 °C / min in an oxygen atmosphere, hold it at 480 °C for 5 h, and then heat it to 740 °C at a rate of 5 °C / min and hold it at 740 °C for 10 h to obtain a high-nickel layered oxide cathode material LiNi 0.96 (Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 )O 2 (denoted as NMANC’). Example 3

[0055] The target product of this example is LiNi 0.96 (Zn 0.01 Al 0.01Nb 0.01 Y 0.01 )O 2 (abbreviated as NZANY), where the mixing entropy of the doping elements is 1.386 R , and the cathode material is prepared by the following method: 1) Weigh nickel sulfate hexahydrate and zinc sulfate heptahydrate according to the stoichiometric ratio of the target product and dissolve them in deionized water to obtain a dark green liquid.

[0056] Dissolve yttrium(III) chloride hexahydrate and citric acid in deionized water according to a molar ratio of 1:2, then add ammonia water to adjust the pH value of the solution to 9.0 to obtain a yttrium salt solution.

[0057] Dissolve Al(OCH(CH 3 )C 2 H 5 ) 3 and C 5 H 8 O 2 (acetylacetone, molar ratio 1:1) in 0.1 L of ethanol, stir evenly at 40 °C to obtain a slightly yellow liquid; dissolve C 4 H 4 NNbO 9 hydrate in 0.1 L of deionized water to obtain a clear solution.

[0058] (2) Pump the above-obtained solution and the mixed alkali solution into a continuously stirred co-precipitation reactor through a peristaltic pump. At the same time, use an instrument pH automatic control system to adjust the pumping of the mixed alkali solution to maintain the pH of the reaction solution at 11.6, the temperature at 50.5 °C, and the rotation speed at 600 rpm. After 48 hours, the reaction ends. After filtering the obtained reaction solution, wash and dry the obtained filter cake in sequence to obtain a hydroxide precursor.

[0059] (3) Grind the obtained hydroxide precursor, pass it through a 400-mesh sieve, take the material under the sieve, mix it with lithium hydroxide monohydrate according to the stoichiometric ratio (lithium hydroxide monohydrate is 2% in excess), and then heat it to 480 °C at a rate of 5 °C / min in an oxygen atmosphere, keep it at 480 °C for 5 h, and then heat it to 740 °C at a rate of 5 °C / min and keep it at 740 °C for 10 h to obtain the ultra-high nickel layered oxide cathode material NZANY. Example 4

[0060] The target product of this example is LiNi 0.94 (Zn 0.01 Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 Y 0.01 )O 2(abbreviated as NZMANCY), where the mixing entropy of the doped elements is 1.79 R , and the positive electrode material is prepared according to the following method: 1) Weigh nickel sulfate hexahydrate, zinc sulfate heptahydrate, magnesium chloride hexahydrate and calcium chloride hexahydrate according to the stoichiometric ratio of the target product and dissolve them in deionized water to obtain a dark green liquid.

[0061] Dissolve yttrium(III) chloride hexahydrate and citric acid in deionized water according to a molar ratio of 1:2, then add ammonia water to adjust the pH value of the solution to 9.0 to obtain a yttrium salt solution.

[0062] Dissolve Al(OCH(CH 3 )C 2 H 5 ) 3 and C 5 H 8 O 2 (acetylacetone, molar ratio 1:1) in 0.1 L of ethanol, stir evenly at 40 °C to obtain a slightly yellow liquid; dissolve C 4 H 4 NNbO 9 hydrate) in 0.1 L of deionized water to obtain a clear solution.

[0063] (2) Pump the above-obtained solution and the mixed alkali solution into a continuously stirred co-precipitation reactor through a peristaltic pump. At the same time, use an instrument pH automatic control system to adjust the pumping of the mixed alkali solution to maintain the pH of the reaction solution at 11.6, the temperature at 50.5 °C, and the rotation speed at 600 rpm. After 48 hours, the reaction ends. Filter the obtained reaction solution, and then wash and dry the obtained filter residue in sequence to obtain a hydroxide precursor.

[0064] (3) Grind the obtained hydroxide precursor and pass it through a 400-mesh sieve. Take the material under the sieve and mix it with lithium hydroxide monohydrate according to the stoichiometric ratio (lithium hydroxide monohydrate is 2% in excess). Then, heat it to 480 °C at a rate of 5 °C / min in an oxygen atmosphere, keep it at 480 °C for 5 h, and then heat it to 740 °C at a rate of 5 °C / min and keep it at 740 °C for 10 h to obtain a high-nickel layered oxide positive electrode material NZMANCY. Example 5

[0065] The target product of this example is LiNi 0.96 (Mg 0.01 Al 0.01 Mo 0.01 Ca 0.01 )O 2 (abbreviated as NMAMC), where the mixing entropy of the doped elements is 1.386 R , and the positive electrode material is prepared according to the following method: (1) Weigh nickel sulfate hexahydrate, magnesium chloride hexahydrate, and calcium chloride hexahydrate according to the stoichiometric ratio of the target product and dissolve them in 1 L of deionized water to obtain a dark green liquid.

[0066] Dissolve Al(OCH(CH 3 )C 2 H 5 ) 3 and C 5 H 8 O 2 (molar ratio 1:1) in 0.1 L of ethanol, stir evenly at 40 °C to obtain a slightly yellow liquid; dissolve (NH 4 ) 6 Mo 7 O 24 in 0.1 L of deionized water to obtain a clear solution.

[0067] (2) Pump the above-obtained solutions and the mixed alkali solution into a continuously stirred co-precipitation reactor through a peristaltic pump. At the same time, use an instrument pH automatic control system to adjust the pumping of the mixed alkali solution to maintain the pH of the reaction solution at 11.6, the temperature at 50.5 °C, and the rotation speed at 600 rpm. After 48 hours, the reaction ends. Filter the obtained reaction solution, and then wash and dry the obtained filter residue in sequence to obtain a hydroxide precursor.

[0068] (3) Grind the obtained hydroxide precursor and pass it through a 400-mesh sieve. Take the material under the sieve and mix it with lithium hydroxide monohydrate according to the stoichiometric ratio (lithium hydroxide monohydrate is 2% in excess). Then, heat it to 480 °C at a rate of 5 °C / min in an oxygen atmosphere, keep it at 480 °C for 5 h, and then heat it to 740 °C at a rate of 5 °C / min and keep it at 740 °C for 10 h to obtain the ultra-high nickel layered oxide cathode material NMAMC. Comparative Example 1

[0069] The target product of this comparative example is LiNi 0.94 Co 0.06 O 2 (abbreviated as NC), and the cathode material is prepared according to the following method: (1) Weigh nickel sulfate hexahydrate and cobalt sulfate heptahydrate according to the stoichiometric ratio of the target product and dissolve them in 1 L of deionized water to obtain a dark green liquid.

[0070] (2) Pump the Ni and Co salt solutions and the mixed alkali solution obtained in step (1) into a continuously stirred co - precipitation reactor through a peristaltic pump. At the same time, use an instrument pH automatic control system to adjust the pumping of the mixed alkali solution to maintain the pH of the reaction solution at 11.6, the temperature at 50.5 °C, and the rotation speed at 600 rpm. After 48 hours, the reaction ends. After filtering the obtained reaction solution, wash and dry the obtained filter residue in sequence to obtain a hydroxide precursor.

[0071] (3) Grind the obtained hydroxide precursor and pass it through a 400 - mesh sieve. Take the material under the sieve and mix it with lithium hydroxide monohydrate according to the stoichiometric ratio (lithium hydroxide monohydrate is 2% in excess). Then, in an oxygen atmosphere, heat it to 480 °C at a rate of 5 °C / min, hold it at 480 °C for 5 h, and then heat it to 740 °C at a rate of 5 °C / min and hold it at 740 °C for 10 h to obtain a nickel - rich layered oxide cathode material NC. Comparative Example 2

[0072] The target product of this example is LiNi 0.95 (Co 0.04 Nb 0.01 )O 2 (abbreviated as NCN), where the mixing entropy of the doping elements is 0.506 R , and prepare the cathode material according to the following method: (1) Weigh nickel sulfate hexahydrate and cobalt sulfate heptahydrate according to the stoichiometric ratio of the target product and dissolve them in 1 L of deionized water to obtain a dark green liquid.

[0073] Dissolve C 4 H 4 NNbO 9 hydrate in 0.1 L of deionized water to obtain a clear solution.

[0074] (2) Pump the above - obtained solution and the mixed alkali solution into a continuously stirred co - precipitation reactor through a peristaltic pump. At the same time, use an instrument pH automatic control system to adjust the pumping of the mixed alkali solution to maintain the pH of the reaction solution at 11.6, the temperature at 50.5 °C, and the rotation speed at 600 rpm. After 48 hours, the reaction ends. After filtering the obtained reaction solution, wash and dry the obtained filter residue in sequence to obtain a hydroxide precursor.

[0075] (3) Grind the obtained hydroxide precursor and pass it through a 400 - mesh sieve. Take the material under the sieve and mix it with lithium hydroxide monohydrate according to the stoichiometric ratio (lithium hydroxide monohydrate is 2% in excess). Then, in an oxygen atmosphere, heat it to 480 °C at a rate of 5 °C / min, hold it at 480 °C for 5 h, and then heat it to 740 °C at a rate of 5 °C / min and hold it at 740 °C for 10 h to obtain a nickel - rich layered oxide cathode material NCN. Comparative Example 3

[0076] The target product of this comparative example is LiNi 0.95 (Co 0.04 Al 0.01 )O 2 (abbreviated as NCA), where the mixing entropy of the doping elements is 0.506 R , and the cathode material is prepared according to the following method: (1) Weigh nickel sulfate hexahydrate and cobalt sulfate heptahydrate according to the stoichiometric ratio of the target product and dissolve them in 1 L of deionized water to obtain a dark green liquid.

[0077] Dissolve Al(OCH(CH 3 )C 2 H 5 ) 3 and C 5 H 8 O 2 (acetylacetone, molar ratio 1:1) in 0.1 L of ethanol, stir evenly at 40 °C to obtain a slightly yellow liquid; (2) Pump the above-obtained solution and the mixed alkali solution into a continuously stirred co-precipitation reactor through a peristaltic pump. At the same time, use an instrument pH automatic control system to adjust the pumping of the mixed alkali solution to maintain the pH of the reaction solution at 11.6, the temperature at 50.5 °C, and the rotation speed at 600 rpm. After 48 hours, the reaction ends. Filter the obtained reaction solution, and then wash and dry the obtained filter residue in sequence to obtain a hydroxide precursor.

[0078] (3) Grind the obtained hydroxide precursor and pass it through a 400-mesh sieve. Take the material under the sieve and mix it with lithium hydroxide monohydrate according to the stoichiometric ratio (lithium hydroxide monohydrate is 2% in excess). Then, heat it to 480 °C at a rate of 5 °C / min in an oxygen atmosphere, keep it at 480 °C for 5 h, and then heat it to 740 °C at a rate of 5 °C / min and keep it at 740 °C for 10 h to obtain the ultra-high nickel layered oxide cathode material NCA. Comparative Example 4

[0079] The target product of this comparative example is LiNi 0.96 (Mg 0.01 Al 0.01 Zn 0.01 Ca 0.01 )O 2 (abbreviated as NMAZC), where the mixing entropy of the doping elements is 1.386 R , and the cathode material is prepared according to the following method: (1) Weigh nickel sulfate hexahydrate, magnesium chloride hexahydrate, zinc sulfate heptahydrate, and calcium chloride hexahydrate according to the stoichiometric ratio of the target product and dissolve them in 1 L of deionized water to obtain a dark green liquid.

[0080] Dissolve Al(OCH(CH 3 )C 2 H 5 ) 3 and C 5 H 8 O 2 (acetylacetone, molar ratio 1:1) in 0.1 L of ethanol, and stir evenly at 40 °C to obtain a slightly yellow liquid; (2) Pump the above-obtained solution and the mixed alkali solution into a continuously stirred co-precipitation reactor through a peristaltic pump. At the same time, use an instrument pH automatic control system to adjust the pumping of the mixed alkali solution to maintain the pH of the reaction solution at 11.6, the temperature at 50.5 °C, and the rotation speed at 600 rpm. After 48 hours, the reaction ends. Filter the obtained reaction solution, and then wash and dry the obtained filter residue in sequence to obtain a hydroxide precursor.

[0081] (3) Grind the obtained hydroxide precursor and pass it through a 400-mesh sieve. Take the material under the sieve and mix it with lithium hydroxide monohydrate according to the stoichiometric ratio (lithium hydroxide monohydrate is 2% in excess). Then, heat it to 480 °C at a rate of 5 °C / min in an oxygen atmosphere, keep it at 480 °C for 5 h, and then heat it to 740 °C at a rate of 5 °C / min and keep it at 740 °C for 10 h to obtain the ultra-high nickel layered oxide cathode material NMAZC.

[0082] 1. Morphology Characterization Characterize the morphologies of the cathode materials obtained in Examples 1-5 and Comparative Example 1, and the results are as Figure 1 shown. As can be seen from Figure 1 it, all the cathode materials are spherical-like particles.

[0083] 2. Mechanical Property Testing Conduct nanoindentation tests on the cathode materials obtained in Example 1 and Comparative Example 1 to test the mechanical properties of the secondary particles of the cathode materials. The obtained pressure-displacement diagram is as Figure 2 shown. When the nanoindentation probe contacts a single secondary particle, the displacement increases with the increase of the pressure. Until the particle is crushed, the displacement becomes constant. When the compression displacement is less than 2 µm, the secondary particles of NC (i.e., the cathode material obtained in Comparative Example 1) are crushed, showing brittle characteristics. In contrast, the failure displacement of the secondary particles of NMANC (i.e., the cathode material obtained in Example 1) is about 3 µm. Therefore, the NMANC cathode material has higher mechanical strength than NC.

[0084] 3. Crystal Form Characterization Conduct XRD tests on the cathode materials obtained in Examples 1-5 and Comparative Example 1 to characterize their crystal forms, and the results are as Figure 3 shown. As can be seen from Figure 3It can be seen that all the cathode materials are α-NaFeO 2 type hexagonal layered structure, belonging to the R3m space group, and no impurity phases appear. The results show that the modification measures in the present invention do not change its original crystal structure, that is, the addition of doping elements in the ultra-high nickel layered oxide cathode material provided by the present invention does not change the crystal form of the cathode material.

[0085] 4. Thermal Stability The cathode material (NC) obtained in Comparative Example 1 and the cathode material (NMANC) obtained in Example 1 were subjected to high-temperature in-situ XRD tests to test the XRD changes of the cathode material during the process of heating from 50 °C to 500 °C and then cooling to 50 °C. The results are as Figure 4 shown, where a is the in-situ XRD patterns of the cathode materials obtained in Example 1 and Comparative Example 1 at 50 °C, heated to 500 °C, and cooled to 50 °C. For the same cathode material, the XRD curves are the corresponding curves of the initial 50 °C, heated to 500 °C, and cooled to 50 °C from top to bottom; b is the change curve of the interplanar spacing during the heating from 50 °C to 500 °C. From Figure 4 a in it can be seen that compared with NC, the displacement change of the (003) peak (i.e., the bulging peak in the figure) of NMANC during the heating process is smaller. Generally speaking, the evolution of the (003) peak is an important signal of structural change. During the heating process from 50 to 500 °C, the maximum change in the peak position of the (003) peak of NMANC is 0.12°, which is less than that of NC (0.19°), indicating that the structural change of NMANC under high-temperature conditions is smaller. When quickly restored from 500 °C to 50 °C, the (003) peak also returns to the initial position, indicating that the structural change is reversible. As Figure 4 shown in b in it, the interplanar spacing of NC and NMANC during the heating process calculated from the peak position of the (003) peak increases linearly, and the thermal expansion coefficient of NMANC (6.81×10 -5 Å / °C) is much lower than that of NC (11.34×10 -5 Å / °C). The above results show that NMANC is less susceptible to high temperature, that is, it has better thermal stability. The cathode materials obtained from other examples were tested and similar results were obtained.

[0086] 5. Electrochemical Property Testing The cathode materials obtained in the examples and comparative examples were prepared into 2032-type button cells according to the following method to test the electrochemical performance.

[0087] The cathode material, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were dispersed in N-methylpyrrolidone in a mass ratio of 8:1:1 to obtain a black slurry. The black slurry was uniformly coated on aluminum foil with a thickness of 75 μm and dried in an oven at 110 °C for 12 h to obtain the cathode electrode sheet. LiPF 6 was dissolved in ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio 3:7) solution to obtain an electrolyte solution with a LiPF 6 concentration of 1 mol / L. In a glove box under a high-purity argon atmosphere (relative humidity < 2%), the cathode electrode sheet, lithium metal anode, Celgard 2400 separator, and electrolyte were assembled into a 2032 coin cell. Before testing, to allow the newly assembled coin cell to reach a stable state, it needed to be left standing for 6 hours before performing the electrochemical performance test.

[0088] (1) After assembling the cathode materials obtained in Example 1 and Comparative Example 1 into batteries according to the above method, the open-circuit potential evolution during standing at 25 °C in the charged state was tested, and the results are as Figure 5 shown.

[0089] After charging to 4.5 V, Example 1 (NMANC) showed a relatively stable open-circuit voltage (OCV) during the resting period. In contrast, the OCV value of Comparative Example 1 (NC) decreased rapidly. The OCV of NC decreased by 0.25 V after only 5 hours, but for NMANC, even after 10 hours, the corresponding OCV decrease was only 0.20 V. This indicates that the self-discharge process of NMANC is slower, and the electrode interface reactivity of the cathode material provided by the present invention is relatively low.

[0090] (2) After assembling the cathode materials obtained in Examples 1-5 and Comparative Example 1 into batteries according to the above method, the first charge-discharge performance of the batteries was tested using a high-precision battery performance test system (Wuhan Blue Electronic Co., Ltd.). The charge-discharge regime was as follows: (1) Stand still for 5 minutes; (2) Constant current charge to the cut-off voltage; (3) Stand still for 5 minutes; (4) Constant current discharge to 2.8 V. The results are as Figure 6 shown.

[0091] As can be Figure 6 seen, the first-week discharge specific capacities of the cathode materials obtained in Examples 1-5 and Comparative Example 1 were close, all exceeding 235 mAh·g -1 , which was significantly better than the currently commercialized high-nickel cathode materials.

[0092] (3) After assembling the cathode materials obtained in Example 1 and Comparative Example 1 into batteries according to the above method, the first-week current-voltage curves (CV curves) of the two cathode materials were tested, and the results are as Figure 7 shown.

[0093] As Figure 7 shown, during the process of lithium ion deintercalation and intercalation, it successively undergoes phase transitions of H1-M, M-H2, H2-H3 and their corresponding reverse reactions. Among them, the H2-H3 phase transition will cause a large volume change of the material. Compared with NC (the cathode material obtained in Comparative Example 1), the intensities of all phase transition peaks from the initial H1 phase to the final H3 phase in NMANC (the cathode material obtained in Example 1) are significantly weakened. At the same time, the anodic peak of the H1-M phase transition in NC starts at 3.65 V, while the corresponding starting potential of NMANC is 3.58 V, indicating that the polarization value of NMANC is lower. In addition, the harmful H2-H3 phase transition peak in NMANC is also significantly inhibited and shifted to a higher potential (4.20 V). In addition, the H2-H3 peak and H3-H2 peak of NMANC are shifted 34 mV and 41 mV to higher potentials compared with NC, respectively, that is, the difference between these two redox peaks decreases, indicating a reduction in polarization and an improvement in the kinetic process. In addition, compared with NC (49 mV), NMANC shows a wider phase transition voltage (81 mV) during the H2-H3 phase transition to mitigate the occurrence of harmful phase transitions, so that the anisotropic strain generated by the phase transition can be dissipated more effectively. In addition, the irreversible lattice oxygen reaction accompanying the harmful H2-H3 phase transition is significantly inhibited, and O 2- and (O 2 ) n- are successfully anchored in the indestructible "oxygen clamping site" of NMANC, thus preventing oxygen escape. It should be noted that the voltage difference between the H1-M and M-H1 phase transitions in NMANC is reduced by 0.11 V, which is less than that of NC (0.25 V), indicating a reduction in electrochemical polarization and good electrochemical reversibility.

[0094] After assembling the cathode materials obtained in Example 1 and Comparative Example 1 into batteries according to the above method, the peak displacement change curves of the (003), (101) and (104) peaks during the first charge and discharge processes of the two cathode materials were tested. The results are as Figure 8 shown, where (a), (b) and (c) are the peak displacement change curves of the (003), (101) and (104) peaks in sequence.

[0095] As Figure 8As shown, for the NMANC cathode material (the cathode material obtained in Example 1), at different cut-off voltages, the angles where the peak positions of (003), (101), and (104) are located show a small and smooth displacement, indicating a small structural change. However, for the NC cathode material (the cathode material obtained in Comparative Example 1), the positions of the corresponding (003), (101), and (104) peaks changed suddenly and significantly. In addition, the changes of NMANC between the initial state and the deep delithiation state (the maximum cut-off voltage is 4.5 V) are lower than those of NC, which are 1.21% (a-axis) and -0.70% (c-axis) respectively, while the corresponding values of NC are 2.00% and -1.67%. Therefore, the volume change value corresponding to NMANC is -1.03%, which is much smaller than the absolute value of NC (-6.72%). That is to say, the volume change of NMANC is only about one-seventh of that of NC, and it is extremely close to the "zero strain" state (volume change < 1%). The above results show that the modified product provided by the present invention can alleviate the severe lattice distortion during the deep delithiation process, stabilize the crystal structure, prevent microcracks from appearing during the charge and discharge process, and even prevent the secondary particles from being crushed.

[0096] (5) After assembling the cathode materials obtained in Example 1 and Comparative Example 1 into batteries according to the above method, a cyclic voltammetry test was performed on the batteries using an electrochemical analyzer (Tianjin Lanliko Technology Co., Ltd.), and the results are as Figure 9 shown.

[0097] As can be Figure 9 seen, at room temperature, when the cut-off potentials are 4.3 V, 4.4 V, and 4.5 V respectively, the capacity retention rates of NMANC after 100 cycles at a current density of 1 C are 98.2%, 96.7%, and 92.5% respectively. In sharp contrast, the corresponding capacity retention rates of NC rapidly dropped to 69.4%, 68.0%, and 67.2% respectively. Even after 300 cycles, NMANC can still provide good and stable Coulomb efficiency in a wide voltage range, demonstrating excellent cycle stability.

[0098] (6) After assembling the cathode materials obtained in Example 1 and Comparative Examples 1-4 into batteries according to the above method, a cyclic voltammetry test (voltage range: 2.8 V - 4.4 V) was performed on the batteries using an electrochemical analyzer (Tianjin Lanliko Technology Co., Ltd.). The result graph is shown in Figure 10.

[0099] As can be Figure 10It can be seen that after 300 cycles, the cathode materials obtained in Example 1 and Comparative Examples 1-4, the cathode material obtained in Example 1 (NMANC) has better cycle stability compared to the nickel-cobalt cathode material (NC in Comparative Example 1), the cathode material doped only with cobalt and modified with micro-morphology improving elements (NCN in Comparative Example 2), the cathode material doped only with cobalt and elements with a bond energy with oxygen greater than that of nickel-oxygen bond (NCA in Comparative Example 3), and the cathode material without doping with micro-morphology improving elements (NMAZC in Comparative Example 4). Specifically, at a current density of 1 C, after 100 cycles, the capacity retention rates of NMANC, NCN, NCA, NMAZC, and NC are 96.7%, 80.4%, 80.0%, 87.1%, and 67.2%, respectively. Characterizations of the cathode materials obtained in Examples 2-5 yielded similar results.

[0100] (7) After the cathode materials obtained in Example 1 and Comparative Example 1 were assembled into batteries according to the above method and cycled at a rate of 1 C for 300 times, scanning electron microscopy was used to characterize the morphology of the cathode materials on their surfaces, and the results are as Figure 11 shown, where a is the SEM image of the cathode material in Comparative Example 1 after 300 cycles, and I, II, and III are the enlarged views of three secondary particles in the first SEM image; b is the SEM image of the cathode material in Example 1 before and after 300 cycles, and I, II, and III are the enlarged views of three secondary particles in the first SEM image. From Figure 11 it can be seen that the NC electrode after cycling shows severe structural degradation. After 300 cycles, obvious spreading cracks and particle crushing occurred in some secondary particles. In contrast, the secondary particles of NMANC still maintained their original spherical morphology after cycling. In addition, the corresponding cross-section shows that after 300 cycles, the internal arrangement still remained basically intact without obvious spreading cracks, indicating that the mechanical integrity of the ultra-high nickel layered oxide crystal structure provided by the present invention is enhanced.

[0101] Although the preferred embodiments of the present invention have been shown and described, it is contemplated that those skilled in the art can design various modifications to the present invention within the spirit and scope of the appended claims.

Claims

1. An ultra-high nickel layered oxide positive electrode material, characterized in that: Its general formula is LiNi x (M1,M2...M n ) 1-x O2, where 0.9≤x≤0.98, M1, M2…M n is the doping element, n is the number of doping elements, and the value of n should satisfy that the mixing entropy of the doping element is greater than or equal to the gas constant R Requirements, M1, M2...M n The doping elements should meet the following conditions: (1) at least one doping element is an element whose bond energy with oxygen is greater than the bond energy with nickel and oxygen, (2) at least one doping element is a microscopic morphology improving element, (3) at least one doping element is a bulk doping element with an ion radius less than 0.076 nm, and (4) At least one doping element is a surface gradient doping element having an ion radius greater than 0.076 nm.

2. The ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: The calculation formula of the mixing entropy of the doping element is: ,in ΔS mix is the mixing entropy, R is the gas constant, R The value of is 8.314 J / K, i For the i doping elements, n is the number of doping elements, C i For the i The atomic percentage of an element.

3. The ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: The elements whose bond energy with oxygen is greater than the bond energy with nickel and oxygen are Sn, Ta, Sr, Ti, W, Y, Nd, Mo, La, Ge, Er, Ce, B, Al, Si, Zr and Nb.

4. The ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: The microstructure improving elements are Ti, Nb, Ta, Mo, W, B and Ga.

5. The ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: The bulk doping elements are B, Si, Mn, Ge, Al, V, W, Ti, Ga, Ta, Fe, Mo, Nb, Sn, Mg and Zn.

6. The ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: The surface gradient doping elements are Er, Y, Ca, Na, La, Sr and Ce.

7. The ultra-high nickel layered oxide positive electrode material according to any one of claims 1 to 6, characterized in that: The atomic ratio of each doping element is the same, 0.94≤x≤0.

96.

8. The ultra-high nickel layered oxide positive electrode material according to any one of claims 1 to 6, characterized in that: The doping element is selected from the element whose bond energy with oxygen is greater than the bond energy with nickel and oxygen, the microscopic morphology improving element, the bulk doping element and the surface gradient doping element.

9. The ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: The ultra-high nickel layered oxide positive electrode material is specifically LiNi 0.96 (Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 )O2、LiNi 0.96 (Zn 0.01 Al 0.01 Nb 0.01 Y 0.01 )O2、LiNi 0.94 (Zn 0.01 Mg 0.01 Al 0.01 Nb 0.01 Ca 0.01 Y 0.01 )O2 or LiNi 0.96 (Mg 0.01 Al 0.01 Mo 0.01 Ca 0.01 )O2, wherein the ratio of each element is the atomic ratio.

10. Use of the ultra-high nickel layered oxide positive electrode material according to any one of claims 1 to 9 in positive electrode materials for lithium-ion batteries.

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