Multi-element modified single-crystal positive electrode material and preparation method therefor, lithium ion battery, and electric device

Abstract

A multi-element modified single-crystal positive electrode material and a preparation method therefor, a lithium ion battery, and an electric device. The multi-element modified single-crystal positive electrode material comprises a single-crystal positive electrode material matrix, element A and element B are doped in the matrix, and the surface of the matrix is coated with an ABO3 coating layer of a perovskite-like structure, wherein the element A is selected from at least one of La, Sr, Ca, Na, Nd, Ce, K, Rb, and Cs, the element B is selected from at least one of Zr, Mo, W, Nb, Sn, Sb, Sc, Al, Ta, and Ti, and in the multi-element modified single-crystal positive electrode material, the molar ratio of the element A to the element B is (0.033-1):1.

Description

A multi-element modified single-crystal positive electrode material, a preparation method thereof, and a lithium ion battery and an electric device

[0001] Related applications

[0002] The present application claims priority to the Chinese patent application No. 202410859226.0, filed on June 28, 2024, and entitled "A multi-element modified single-crystal positive electrode material, a preparation method thereof, and a lithium ion battery and an electric device", the contents of which are hereby incorporated by reference in their entirety. TECHNICAL FIELD

[0003] The present application belongs to the field of lithium ion batteries, and particularly relates to a multi-element modified single-crystal positive electrode material, a preparation method thereof, and a lithium ion battery and an electric device. BACKGROUND

[0004] In recent years, electric vehicles have developed rapidly, and higher requirements have been put forward for the energy density and cycle life of lithium ion batteries. In order to achieve better battery performance, the working voltage of single-crystal positive electrode materials is continuously increased, and with the increase of the amount of lithium extraction, the internal structure stability of the material becomes poor, which leads to a substantial deterioration of the cycle performance, affecting the endurance and battery life of electric vehicles. At present, doping can solve the problem of material bulk phase stability to a certain extent, but the current doping work is difficult to balance long-term performance and short-term performance, and often brings certain capacity loss or increase of initial impedance. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the deficiencies and defects mentioned in the above background, and to provide a multi-element modified single-crystal positive electrode material, a preparation method thereof, and a lithium ion battery and an electric device.

[0006] To solve the above technical problems, the technical solution provided by the present application is as follows:

[0007] A multi-element modified single-crystal positive electrode material, comprising a single-crystal positive electrode material base body, wherein A elements and B elements are doped in the single-crystal positive electrode material base body, and a perovskite-like structure ABO3 coating layer is coated on the surface of the single-crystal positive electrode material base body, wherein A is selected from at least one of La, Sr, Ca, Na, Nd, Ce, K, Rb, and Cs, and B is selected from at least one of Zr, Mo, W, Nb, Sn, Sb, Sc, Al, Ta, and Ti, and the molar ratio of A to B in the multi-element modified single-crystal positive electrode material is (0.033-1):1.

[0008] Based on a general inventive concept, the application also provides a multi-element modified single-crystal positive electrode material, the multi-element including an A element and a B element, the A element and the B element partially doped into a single-crystal positive electrode material matrix phase and partially forming an ABO3 coating layer with a perovskite-like structure on a single-crystal positive electrode material matrix surface, wherein the A element is selected from at least one of La, Sr, Ca, Na, Nd, Ce, K, Rb, and Cs, and the B element is selected from at least one of Zr, Mo, W, Nb, Sn, Sb, Sc, Al, Ta, and Ti, and a molar ratio of the A element to the B element in the multi-element modified single-crystal positive electrode material is (0.033-1):1.

[0009] The multi-element modified single-crystal positive electrode material described above, wherein a chemical formula of the single-crystal positive electrode material matrix is Li a Ni (1-x-y) Co x M y O2, wherein 1

[0010] The multi-element modified single-crystal positive electrode material described above, wherein a concentration of the A element and the B element gradually decreases from a surface of a single-crystal positive electrode material primary particle to a center of the single-crystal positive electrode material primary particle in the multi-element modified single-crystal positive electrode material.

[0011] The multi-element modified single-crystal positive electrode material described above, wherein a single-crystal positive electrode material primary particle of the multi-element modified single-crystal positive electrode material is regionally divided, a region with a distance of 0≤L≤0.3R from a surface of the primary particle is a first region, and a region with a distance of 0.3R

[0012] In the single-crystal cathode material of the present application, multiple elements are used for modification, the A and B elements have a higher concentration on the surface layer of the material, the ABO3 coating layer formed is conducive to resisting the corrosion of the electrolyte, enhancing the cycle stability, and the perovskite coating layer formed by ABO3 has a higher ionic conductivity, which is conducive to the rapid transmission of lithium ions, and the ABO3 coating layer can stabilize the oxygen on the surface of the material and also improve the cycle performance of the material; the low-concentration A and B element bulk-phase doping is conducive to inhibiting the inherent lattice strain in the layered oxide, enhancing the mechanical strength of the material, and improving the crystal structure of the material. As known, too much doping of some elements is not conducive to the capacity and cycle performance of the material, and the concentration gradient design of the A and B elements in the single-crystal cathode material of the present application makes the synergistic effect of doping and coating not only optimize the capacity, but also enhance the stability of the material and inhibit the release of gas.

[0013] In the present application, the doping elements enter the bulk phase, which can stabilize the interface / lattice, improve ion diffusion, and improve the bulk phase stability by coexisting multiple structures, form a perovskite coating on the surface of the material, and the surface coating layer protects the interface to prevent the corrosion of the electrolyte.

[0014] Based on the overall inventive concept, the present application further provides a preparation method of the above-mentioned multiple-element modified single-crystal cathode material, which comprises the following steps:

[0015] (1) adding single-crystal cathode material precursors, a lithium source, an A element-containing compound, and a B element-containing compound into a solvent for wet ball milling mixing, drying, and grinding, and then performing first sintering;

[0016] (2) re-grinding the sintered material of step (1), then performing second sintering on the ground material, and naturally cooling to room temperature after the sintering is completed, to obtain the multiple-element modified single-crystal cathode material.

[0017] In the above-mentioned preparation method, in step (1), the addition amount of the A element-containing compound is 200 ppm-1500 ppm, and the addition amount of the B element-containing compound is 200-3000 ppm.

[0018] In the above-mentioned preparation method, in step (1), the lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium acetate, or lithium nitrate.

[0019] Optionally, the A element-containing compound comprises one or more of an oxide, a hydroxide, a fluoride, a nitrate, a phosphate, or a sulfate containing the A element.

[0020] Optionally, the B element-containing compound comprises one or more of an oxide, a hydroxide, a fluoride, a nitrate, a phosphate, or a sulfate containing the B element.

[0021] In the preparation method, in step (1), the wet ball milling is performed at a speed of 240 rpm / min-360 rpm / min for 7 h-12 h, and the solvent is ethanol.

[0022] In the preparation method, in step (1), the drying comprises vacuum drying, and the vacuum drying is performed at a temperature of 60℃-120℃ for 6-12 h.

[0023] In the preparation method, in step (1), the first sintering is performed in an oxygen atmosphere, and the first sintering is performed at a temperature of 400℃-700℃ for 2 h-5 h.

[0024] In the preparation method, in step (2), the second sintering is performed in an oxygen atmosphere, and the second sintering is performed in stages, i.e., first, the temperature is increased from room temperature to 400℃-600℃, and then the temperature is kept constant for 1 h-3 h, and then the temperature is increased to 800℃-900℃, and then the temperature is kept constant for 7 h-12 h.

[0025] Based on the overall inventive concept, the application further provides a lithium ion battery comprising the multi-element modified single-crystal cathode material or the multi-element modified single-crystal cathode material prepared by the preparation method.

[0026] Based on the overall inventive concept, the application further provides an electric device comprising the lithium ion battery.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] (1) In the multi-element modified single-crystal cathode material, the coordination number of the A element is XII, the ionic radius is close to that of O ions, the coordination number of the B element is VI, and the A and B elements are partially doped into the single-crystal cathode material, which is beneficial to inhibit the inherent lattice strain in the layered oxide, enhance the mechanical strength of the material, improve the crystal structure of the material, form an ABO3 coating layer with a perovskite-like structure on the surface of the single-crystal cathode material, improve the stability of the material, and the ABO3 coating layer and the single-crystal cathode material substrate can be well integrated, which has obvious improvement effects on the capacity and initial DCR of the cathode material, and the doping and coating can synergistically enhance the structural stability of the material.

[0029] (2) The application introduces part of the A element and the B element into the bulk phase and part of them on the surface to form an ABO3 perovskite phase. Due to the structural compatibility, the perovskite phase can grow into a layered structure, which can greatly inhibit the inherent lattice strain in the layered oxide, thereby leading to long-term structural and morphological stability, preventing side reactions and irreversible phase from extending to the whole particle. The multi-element modified single-crystal positive electrode material has excellent long-term cycle stability at a high cut-off voltage of 4.45 V.

[0030] (3) The multi-element modified single-crystal positive electrode material of the application has an ABO3 type perovskite structure with an oxygen vacancy structure, which can act as a transfer station for internal lattice oxygen. This structure can be introduced as an oxygen-containing layer to the surface of the cathode material, which can reduce the oxygen loss rate by increasing the energy barrier of the lattice oxide escaping from the cathode, thereby reducing oxygen release, stabilizing the bulk phase structure, and alleviating irreversible phase transition, thereby improving the gas production performance of the single-crystal positive electrode material during long-term cycling or storage.

[0031] (4) The ABO3 type perovskite structure formed by the application can significantly improve the ionic conductivity of the material, which is conducive to the rapid transport of lithium ions. In addition, part of the ABO3 is located on the surface layer of the material, which can effectively inhibit the phase transition caused by the contact between the material surface and the electrolyte, and stabilize the cathode-electrolyte interface, thereby improving the stability and storage performance of the material.

[0032] (5) In the modified single-crystal positive electrode material of the application, the concentration of A and B elements gradually decreases from the surface of the single-crystal positive electrode material primary particles to the center of the single-crystal positive electrode material primary particles. The concentration of A and B elements in the material has a specific gradient distribution, which, combined with the protective layer formed by the surface coating layer, can significantly improve the Li + transport behavior, reduce the structural degradation and phase transition behavior at the grain boundary of the high-nickel single-crystal positive electrode material, and inhibit the generation of cracks in the particle, thereby improving the capacity and cycle stability of the material, and maintaining the complete structure even after multiple cycles.

[0033] (6) The preparation method of the application is simple. Wet grinding is used to increase the flowability between materials, and a large friction force is generated between materials and equipment, which finally makes the prepared material mixture more uniform. In addition, part of the elements in the A and B combination has a fluxing effect, which can reduce the sintering temperature and save sintering cost. The process is controllable, which is conducive to the partial doping of the material into the bulk phase and the partial location of the material on the surface, and the uniformity of the surface layer constructed by it is good. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only belong to the embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on the disclosed drawings.

[0035] Figure 1 is TEM and FFT data of the single-crystal cathode material prepared in Example 1 of the present application.

[0036] Figure 2 is EPMA data of the single-crystal cathode material prepared in Example 2 of the present application.

[0037] Figure 3 is data of EPMA point scanning from surface to bulk concentration change of the single-crystal cathode material prepared in Example 2 of the present application.

[0038] Figure 4 is high-temperature DCR growth rate performance data of the single-crystal cathode material prepared in Examples 1-6 and Comparative Examples 1-3 of the present application. DETAILED DESCRIPTION

[0039] In order to facilitate the understanding of the present application, the present application will be described more fully and completely by combining the accompanying drawings and preferred embodiments in the following description, but the scope of protection of the present application is not limited to the following specific embodiments.

[0040] Unless otherwise defined, all the professional terms used in the following description have the same meaning as understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific embodiments and are not intended to limit the scope of protection of the present application.

[0041] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0042] In the following examples, the radius R of the primary particles is obtained by measuring the diameters of a plurality of single-crystal particles using nano-measurer software, taking the average value and dividing it by 2 to obtain the radius R.

[0043] In the following examples, the concentration gradient distribution of elements A and B from the outside to the inside is tested by the following method: by using an electron probe X-ray microanalyzer (EPMA), 11 points with uniform spacing are selected from the surface of the single-crystal particle to the center R, and the mass fraction of the elements contained in each example is tested to obtain specific numerical values by calculation.

[0044] Example 1:

[0045] A multi-element modified single-crystal cathode material, comprising a single-crystal cathode material matrix, the chemical formula of the single-crystal cathode material matrix is LiNi 0.8 Co0.06 Mn 0.14 O2, the single crystal positive electrode material matrix is doped with Ca and Zr elements, and the surface of the matrix is coated with a CaZrO3 coating layer with a perovskite-like structure, the molar ratio of Ca and Zr elements in the multi-element modified single crystal positive electrode material is 0.545:1.

[0046] The preparation method of the multi-element modified single crystal positive electrode material of the embodiment is as follows:

[0047] (1) LiOH·H2O and Ni 0.8 Co 0.06 Mn 0.14 (OH)2 precursor according to a molar ratio of 1.06:1, and simultaneously weighing a dopant A: CaCO3, 600ppm, and a dopant B: ZrO2, 2500ppm, mixing the weighed raw materials with ethanol, and using a planetary ball mill with polyurethane balls and zirconia grinding media to grind for 9h, the rotation speed of wet ball milling is 300rpm / min;

[0048] (2) The wet raw materials after step (1) ball milling are dried in a vacuum drying box at 120℃ for 12h to remove ethanol;

[0049] (3) The dried raw materials after step (2) are ground, and then put into an alumina crucible, sintered at 600℃ for 3h in an oxygen atmosphere;

[0050] (4) The powder after step (3) sintering is ground again;

[0051] (5) The ground powder after step (4) is put into a zirconia crucible, heated from room temperature to 500℃ at a heating rate of 3℃ / min in an oxygen atmosphere, sintered for 3h, then heated to 870℃, sintered for 12h, and naturally cooled to room temperature, to obtain a multi-element modified single crystal positive electrode material, in which Ca and Zr elements are partially doped into the single crystal positive electrode material phase, and partially form a CaZrO3 coating layer with a perovskite-like structure on the surface of the single crystal positive electrode material.

[0052] The TEM and FFT data of the single crystal positive electrode material in this embodiment are shown in Figure 1, the coating layer can be observed on the surface of the single crystal particle, which can be attributed to the (020) plane of the CaZrO3 perovskite phase, confirming that the CaZrO3 coating layer is indeed formed on the surface of the single crystal positive electrode material.

[0053] The multi-element modified single crystal positive electrode material particles are regionally divided, the region with a distance of 0≤L≤0.3R from the surface of the primary particles is a first region, and the region with a distance of 0.3R

[0054] Example 2:

[0055] A multi-element modified single crystal positive electrode material, comprising a single crystal positive electrode material matrix, the chemical formula of the single crystal positive electrode material matrix being LiNi 0.8 Co 0.06 Mn 0.14 O2, the single crystal positive electrode material matrix being doped with Ca and Nb elements, and the surface of the matrix being coated with a CaNbO3 coating layer with a perovskite structure, the molar ratio of Ca and Nb elements in the multi-element modified single crystal positive electrode material being 0.93:1.

[0056] The preparation method of the multi-element modified single crystal positive electrode material of the present embodiment is as follows:

[0057] (1) LiOH·H2O and Ni 0.8 Co 0.06 Mn 0.14 (OH)2 precursor are weighed according to a molar ratio of 1.06:1, and a dopant A: CaCO3, 600 ppm, and a dopant B: Nb2O5, 1500 ppm, are weighed, the weighed raw materials are mixed with ethanol, and a planetary ball mill with polyurethane balls and zirconia grinding media is used for grinding for 9 h, and the rotation speed of wet ball milling is 300 rpm / min;

[0058] (2) The wet raw materials after ball milling in step (1) are dried in a vacuum drying box at 120℃ for 12 h to remove alcohol;

[0059] (3) The raw material after drying in step (2) is ground, and then put into an alumina crucible, heated to 600℃ in an oxygen atmosphere, and sintered for 3h;

[0060] (4) The powder after sintering in step (3) is ground again;

[0061] (5) The powder after grinding in step (4) is put into a zirconia crucible, heated to 500℃ at a heating rate of 3℃ / min from room temperature in an oxygen atmosphere, sintered for 3h, and then heated to 880℃, sintered for 12h, and naturally cooled to room temperature, to obtain a multi-element modified single-crystal cathode material. In the cathode material, Ca and Nb elements are partially doped into the single-crystal cathode material bulk phase, and partially form a CaNbO3coating layer with a perovskite-like structure on the surface of the single-crystal cathode material.

[0062] The EPMA data of the single-crystal cathode material prepared in this example is shown in Figure 2. It can be observed from the figure that Nb and C elements are enriched on the surface of the single-crystal particles, and form a clear gradient distribution from the surface to the center. The EPMA line scanning data of the concentration change from the surface to the bulk phase is shown in Figure 3. The concentration of Ca and Nb elements decreases in different amplitudes from the surface to the bulk phase. The region with a distance of 0≤L≤0.3R from the surface of the primary particles is the first region, and the region with a distance of 0.3R<L≤R from the surface of the particles is the second region. In the first region, the concentration of A element decreases in a gradient distribution by 61.04%, 52.27% and 15.76% in each 0.1R interval from the outside to the inside of the particles, and the concentration of B element decreases in a gradient distribution by 59.75%, 30.56% and 11.16% in each 0.1R interval from the outside to the inside of the particles. In the second region, the concentration of A element decreases in a gradient distribution by 9.02%, 6.17%, 5.7%, 5.37%, 4.96%, 2.99% and 2.31% in each 0.1R interval from the outside to the inside of the particles, and the concentration of B element decreases in a gradient distribution by 8.33%, 6.67%, 5.19%, 4.11%, 3.57%, 2.96% and 2.29% in each 0.1R interval from the outside to the inside of the particles. R is the radius of the primary particles of the multi-element modified single-crystal cathode material, and R is 1.03μm.

[0063] Example 3:

[0064] A multi-element modified single-crystal cathode material, comprising a single-crystal cathode material matrix, the chemical formula of the single-crystal cathode material matrix being LiNi 0.8 Co 0.06 Mn 0.14O2, the positive electrode material is doped with Sr and Zr elements, a SrZrO3coating layer with a perovskite-like structure is coated on the surface of the substrate, and the molar ratio of Sr and Zr in the positive electrode material is 0.41:1.

[0065] The preparation method of the multi-element modified single-crystal positive electrode material of the embodiment is as follows:

[0066] (1) LiOH·H2O and Ni 0.8 Co 0.06 Mn 0.14 (OH)2precursor are weighed according to a molar ratio of 1.06:1, a dopant A: SrO, 1000 ppm, and a dopant B: ZrO2, 2500 ppm are weighed, the weighed raw materials are mixed with ethanol, and a planetary ball mill with polyurethane balls and zirconia grinding media is used for grinding for 9 h, and the rotation speed of wet ball milling is 330 rpm / min;

[0067] (2) The wet raw materials after ball milling in step (1) are dried in a vacuum drying box at 120℃ for 12 h to remove alcohol;

[0068] (3) The dried raw materials in step (2) are ground, and then put into an alumina crucible, heated to 600℃ in an oxygen atmosphere, and sintered for 3 h;

[0069] (4) The powder after sintering in step (3) is ground again;

[0070] (5) The ground powder in step (4) is put into a zirconia crucible, heated to 500℃ from room temperature at a heating rate of 3℃ / min in an oxygen atmosphere, sintered for 3 h, then heated to 870℃, sintered for 12 h, and naturally cooled to room temperature, to obtain a multi-element modified single-crystal positive electrode material, in which Sr and Zr elements are partially doped into the single-crystal positive electrode material bulk phase, and partially form a SrZrO3coating layer with a perovskite-like structure on the surface of the single-crystal positive electrode material.

[0071] The multi-element modified single crystal positive electrode material primary particles are regionally divided, the region with a distance of 0≤L≤0.3R from the surface of the primary particle is a first region, and the region with a distance of 0.3R

[0072] Example 4:

[0073] A multi-element modified single crystal positive electrode material, comprising a single crystal positive electrode material matrix, the chemical formula of the single crystal positive electrode material matrix being LiNi 0.8 Co 0.06 Mn 0.14 O2, the single crystal positive electrode material matrix being doped with Sr and Ti elements, and a perovskite-like SrTiO3 coating layer being coated on the surface of the matrix, the molar ratio of Sr and Ti elements in the positive electrode material being 0.547:1.

[0074] The preparation method of the multi-element modified single crystal positive electrode material of the present embodiment is as follows:

[0075] (1) LiOH·H2O and Ni 0.8 Co 0.06 Mn 0.14 (OH)2 precursor are weighed according to a molar ratio of 1.06:1, a dopant A: SrO of 1000 ppm and a dopant B: TiO2 of 1000 ppm are weighed, the weighed raw materials are mixed with ethanol, and a planetary ball mill with polyurethane balls and zirconia grinding media is used for grinding for 10 h, and the rotation speed of wet ball milling is 350 rpm / min;

[0076] (2) The wet raw materials after ball milling in step (1) are dried in a vacuum drying box at 120℃ for 12 h to remove alcohol;

[0077] (3) The raw material dried in step (2) is ground and then placed in an alumina crucible, heated to 600℃ in an oxygen atmosphere, and sintered for 3h;

[0078] (4) The powder sintered in step (3) is ground again;

[0079] (5) The ground powder in step (4) is placed in a zirconia crucible, heated to 500℃ at a rate of 3℃ / min from room temperature in an oxygen atmosphere, sintered for 3h, then heated to 880℃, sintered for 12h, and naturally cooled to room temperature to obtain a multi-element modified single-crystal cathode material. In the cathode material, Sr and Ti elements are partially doped into the single-crystal cathode material bulk phase and partially form a SrTiO3 coating layer with a perovskite-like structure on the surface of the single-crystal cathode material.

[0080] The primary particles of the multi-element modified single-crystal cathode material are regionally divided. The region with a distance of 0≤L≤0.3R from the surface of the primary particle is the first region, and the region with a distance of 0.3R

[0081] Example 5:

[0082] A multi-element modified single-crystal cathode material includes a single-crystal cathode material matrix with a chemical formula of LiNi 0.8 Co 0.06 Mn 0.14 O2, doped with Na and Nb elements, and a perovskite-like NaNbO3 coating layer on the surface of the matrix. The molar ratio of Na and Nb in the single-crystal cathode material is 0.675:1.

[0083] The preparation method of the multi-element modified single-crystal cathode material of the present embodiment is as follows:

[0084] (1) LiOH H2O and Ni 0.8 Co 0.06 Mn 0.14 (OH)2 precursor according to a molar ratio of 1.06:1, while the dopant Na2CO3, 500 ppm, and the dopant B: Nb2O5, 1500 ppm, were weighed, the weighed raw materials were mixed with ethanol, and a planetary ball mill with polyurethane balls and zirconium oxide grinding media was used to grind for 10 h, with a wet ball mill rotation speed of 340 rpm / min;

[0085] (2) The wet raw materials after ball milling in step (1) were dried in a vacuum drying oven at 120°C for 12 h to remove alcohol;

[0086] (3) The dried raw materials in step (2) were ground and then placed in an alumina crucible, heated to 600°C in an oxygen atmosphere, and sintered for 3 h;

[0087] (4) The powder after sintering in step (3) was ground again;

[0088] (5) The ground powder in step (4) was placed in a zirconium oxide crucible, heated to 500°C at a heating rate of 3°C / min from room temperature in an oxygen atmosphere, sintered for 3 h, then heated to 870°C, sintered for 12 h, and naturally cooled to room temperature to obtain a multi-element modified single-crystal cathode material. In the multi-element modified single-crystal cathode material, Na and Nb elements partially doped into the single-crystal cathode material bulk phase, and partially formed a NaNbO3 coating layer with a perovskite-like structure on the surface of the single-crystal cathode material.

[0089] The primary particles of the multi-element modified single-crystal cathode material were regionally divided. The region with a distance of 0≤L≤0.3R from the surface of the primary particle was the first region, and the region with a distance of 0.3R

[0090] Example 6:

[0091] A multi-element modified single-crystal positive electrode material, comprising a single-crystal positive electrode material matrix, the single-crystal positive electrode material matrix having a chemical formula of LiNi 0.8 Co 0.06 Mn 0.14 O2, the single-crystal positive electrode material matrix being doped with Na, La and Ti elements, and a perovskite-like structure Na 0.35 La 0.55 TiO3 coating layer being coated on the surface of the matrix, wherein the molar ratio of Na+La to Ti in the single-crystal positive electrode material is 0.87:1.

[0092] The preparation method of the multi-element modified single-crystal positive electrode material of the embodiment is as follows:

[0093] (1) LiOH·H2O and Ni 0.8 Co 0.06 Mn 0.14 (OH)2 precursor are weighed according to a molar ratio of 1.06:1, and a dopant A: La2O3, 1000 ppm, Na2CO3, 500 ppm, and a dopant B: TiO2, 1000 ppm are weighed, the weighed raw materials are mixed with ethanol, and a planetary ball mill with polyurethane balls and zirconium oxide grinding media is used for grinding for 11 h, and the rotation speed of wet ball milling is 355 rpm / min;

[0094] (2) the wet raw materials after ball milling in step (1) are dried in a vacuum drying box at 120°C for 12 h to remove alcohol;

[0095] (3) the dried raw materials in step (2) are ground, and then are put into an alumina crucible, and are sintered at 600°C for 3 h in an oxygen atmosphere;

[0096] (4) the powder after sintering in step (3) is ground again;

[0097] (5) the ground powder in step (4) is put into a zirconium oxide crucible, and is heated to 500°C from room temperature at a heating rate of 3°C / min in an oxygen atmosphere, and is sintered at 500°C for 3 h, and then is heated to 875°C, and is sintered at 875°C for 12 h, and is naturally cooled to room temperature, to obtain a multi-element modified single-crystal positive electrode material, wherein the Na, La and Ti elements are partially doped into the single-crystal positive electrode material bulk phase, and a perovskite-like structure Na 0.35 La 0.55 TiO3 coating layer is formed on the surface of the single-crystal positive electrode material.

[0098] The multi-element modified single crystal cathode material primary particles are regionally divided, the region with a distance of 0≤L≤0.3R from the surface of the primary particle is a first region, and the region with a distance of 0.3R

[0099] Comparative Example 1

[0100] Except that the dopant A: CaCO3 is 2000 ppm, and the dopant B: ZrO2 is 2500 ppm, the remaining steps, process parameters and example 1 are the same.

[0101] Comparative Example 2

[0102] Except that the dopant A: BaCO3 is 1000 ppm, and the dopant B: ZrO2 is 2500 ppm, the remaining steps, process parameters and example 1 are the same.

[0103] Comparative Example 3

[0104] The preparation method of the single crystal cathode material in the present comparative example is as follows: LiOH·H2O and Ni 0.8 Co 0.06 Mn 0.14 (OH)2 precursor are weighed according to a molar ratio of 1.06:1, and the dopant A: CaCO3, 600 ppm, and the dopant B: ZrO2, 2500 ppm are weighed and mixed uniformly, then they are placed in a zirconium oxide crucible, heated from room temperature to 500℃ at a heating rate of 3℃ / min in an oxygen atmosphere, and then heated to 870℃ for 12h, and then naturally cooled to room temperature. The prepared cathode material has a chemical formula of LiNi 0.8 Co 0.058 Mn 0.13785 Ca 0.00146 Zr 0.00269 O2, and the single crystal cathode material has no coating layer.

[0105] The single crystal cathode material samples prepared in Examples 1-6 and Comparative Examples 1-3 of the present application were assembled into CR2025 button half-cells as ternary cathode active materials: first, 8:1:1 of the single crystal cathode active material, acetylene black conductive agent and polyvinylidene fluoride (PVDF) binder were mixed, then an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added, and the collected slurry was uniformly coated on an aluminum foil. After drying at 120°C for 12h, the cathode active material with a loading mass of 2.5mg / cm 2 The batteries were assembled in an Ar-filled glove box, with lithium metal as the anode, polypropylene (Celgard 2400) as the separator, and 1mol / L LiPF6 dissolved in a mixture of ethyl carbonate and dimethyl carbonate (EC:DMC = 1:1 by volume) as the electrolyte. Button half-cells were assembled for electrochemical performance testing.

[0106] The button half-cells assembled with the single crystal cathode materials prepared in Examples 1-6 and Comparative Examples 1-3 were tested at a voltage window of 3.0-4.45V, and the resulting capacity, DCR, room temperature cycling, high temperature cycling performance and high temperature DCR growth rate performance were as shown in Table 1.

[0107] Table 1. Single crystal cathode material button cell performance test results

[0108] As can be seen from Table 1, the multi-element modified single crystal cathode materials prepared in Examples 1-6 can significantly improve the DCR, room temperature cycling, high temperature cycling and high temperature DCR growth rate without losing capacity. In particular, Example 1, compared to Comparative Example 3, has a slightly improved capacity, a 5.5Ω reduction in initial DCR at 10% SOC, and a capacity retention rate of 96.2% after 30 cycles at 45°C. This is due to the partial doping of Ca and Zr into the bulk phase to improve the material structure, and the formation of a CaZrO3 perovskite coating layer at the material surface to improve stability. The CaZrO3 and the cathode material matrix can be well integrated.

[0109] In Comparative Example 1, the excessive amount of CaCO3 doping is not conducive to inhibiting phase transition and the resulting structural instability, and the excessively thick coating layer is not conducive to the rapid transport of Li + In Comparative Example 2, the introduction of Ba element forms a BaZrO3 perovskite coating layer that is not conducive to DCR. In Comparative Example 3, no CaZrO3 coating layer is formed, and the electrochemical performance of the material is poor.

[0110] The single crystal positive electrode materials prepared in Examples 1-6 and Comparative Examples 1-3 were assembled into coin half-cells, and the DCR increase rate performance of the coin half-cells was tested at 45°C under a voltage window of 3.0-4.45V for 30 cycles, as shown in FIG. 4. It can be seen from the figure that the multi-element modified single crystal positive electrode material prepared in Example 3 has the best DCR increase rate, and in addition, the other examples also have better DCR increase rate than Comparative Examples 1-3, which is due to the improvement effect of the ABO3 structure on the material structure and stability.

[0111] The technical features of the above-described embodiments can be combined in any manner. In order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not contradict each other, they should be considered as falling within the scope of the present disclosure.

[0112] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all fall within the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. A multi-element modified single-crystal cathode material, comprising a single-crystal cathode material matrix, wherein the single-crystal cathode material matrix is ​​doped with elements A and B, and the surface of the single-crystal cathode material matrix is ​​coated with a perovskite-like ABO3 coating layer, wherein... Element A is selected from at least one of La, Sr, Ca, Na, Nd, Ce, K, Rb, and Cs, and element B is selected from at least one of Zr, Mo, W, Nb, Sn, Sb, Sc, Al, Ta, and Ti. In the multi-element modified single-crystal cathode material, the molar ratio of element A to element B is (0.033-1):

1.

2. A multi-element modified single-crystal cathode material, wherein, The multi-element material includes elements A and B. Elements A and B are partially doped into the bulk phase of the single-crystal cathode material matrix and partially form a perovskite-like ABO3 coating layer on the surface of the single-crystal cathode material matrix. Element A is selected from at least one of La, Sr, Ca, Na, Nd, Ce, K, Rb, and Cs, and element B is selected from at least one of Zr, Mo, W, Nb, Sn, Sb, Sc, Al, Ta, and Ti. In the multi-element modified single-crystal cathode material, the molar ratio of element A to element B is (0.033-1):

1.

3. The multi-element modified single-crystal cathode material according to any one of claims 1 to 2, wherein, The chemical formula of the single crystal cathode material matrix is Li a Ni (1-x-y) Co x M y O2, where 1 < a ≤ 1.1, 0 < x ≤ 0.4, 0 < y < 0.4, and M is selected from Mn or / and Al.

4. The multi-element modified single-crystal cathode material according to any one of claims 1 to 3, wherein, In the multi-element modified single-crystal cathode material, the elemental concentrations of elements A and B gradually decrease from the surface of the primary particles of the single-crystal cathode material to the center of the primary particles.

5. The multi-element modified single-crystal cathode material according to any one of claims 1 to 4, wherein, The primary particles of the multi-element modified single-crystal cathode material are divided into regions. The region with a distance of 0 ≤ L ≤ 0.3R from the surface of the primary particle is the first region, and the region with a distance of 0.3R < L ≤ R from the surface of the primary particle is the second region. In the first region, the concentrations of elements A and B decrease in a gradient of 10.9%-62% from the outside to the inside, and in the second region, the concentrations of elements A and B decrease in a gradient of 0.1%-10% from the outside to the inside, where R is the radius of the primary particle of the multi-element modified single-crystal cathode material.

6. The multi-element modified single-crystal cathode material according to any one of claims 1 to 5, wherein, Element A is selected from one, two, or three of La, Sr, Ca, Na, Nd, Ce, K, Rb, and Cs, and element B is selected from one or two of Zr, Mo, W, Nb, Sn, Sb, Sc, Al, Ta, and Ti.

7. A method for preparing a multi-element modified single-crystal cathode material as described in any one of claims 1 to 6, wherein, Includes the following steps: (1) The single crystal cathode material precursor, lithium source, compound containing element A and compound containing element B are added to a solvent and mixed by wet ball milling, dried, ground and then sintered for the first time. (2) Grind the material after sintering in step (1) again, and sinter the ground material a second time. After sintering, cool it naturally to room temperature to obtain a multi-element modified single crystal cathode material.

8. The method for preparing the multi-element modified single-crystal cathode material as described in claim 7, wherein, In step (1), the amount of compound containing element A added is 200ppm-1500ppm, and the amount of compound containing element B added is 200ppm-3000ppm.

9. The method for preparing the multi-element modified single-crystal cathode material according to any one of claims 7-8, wherein, In step (1), the lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium acetate or lithium nitrate.

10. The method for preparing the multi-element modified single-crystal cathode material according to any one of claims 7 to 9, wherein, In step (1), the compound containing element A includes one or more of the following: oxides, hydroxides, fluorides, nitrates, phosphates, or sulfates containing element A.

11. The method for preparing the multi-element modified single-crystal cathode material according to any one of claims 7 to 10, wherein, In step (1), the compound containing element B includes one or more of the following: oxides, hydroxides, fluorides, nitrates, phosphates, or sulfates containing element B.

12. The method for preparing the multi-element modified single-crystal cathode material according to any one of claims 7 to 11, wherein, In step (1), the rotation speed of the wet ball mill is 240 rpm / min-360 rpm / min, and the ball milling time is 7h-12h.

13. The method for preparing the multi-element modified single-crystal cathode material according to any one of claims 7 to 12, wherein, In step (1), the drying includes vacuum drying, the temperature of which is 60℃-120℃ and the time of which is 6h-12h.

14. The method for preparing the multi-element modified single-crystal cathode material according to any one of claims 7 to 13, wherein, In step (1), the first sintering is carried out in an oxygen atmosphere.

15. The method for preparing the multi-element modified single-crystal cathode material according to any one of claims 7 to 14, wherein, In step (1), the temperature of the first sintering is 400℃-700℃, and the sintering time is 2h-5h.

16. The method for preparing the multi-element modified single-crystal cathode material according to any one of claims 7 to 15, wherein, In step (2), the second sintering is carried out in an oxygen atmosphere.

17. The method for preparing the multi-element modified single-crystal cathode material according to any one of claims 7 to 16, wherein, In step (2), the second sintering is a segmented sintering process. First, the temperature is raised from room temperature to 400℃-600℃ and held for 1h-3h, then raised to 800℃-900℃ and held for 7h-12h.

18. A lithium-ion battery, wherein, The lithium-ion battery comprises a multi-element modified single-crystal cathode material according to any one of claims 1 to 6, or a multi-element modified single-crystal cathode material prepared by the preparation method of the multi-element modified single-crystal cathode material according to any one of claims 7 to 17.

19. An electrical appliance, wherein, Including the lithium-ion battery as described in claim 18.

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