Zirconium-yttrium composite coated modified lithium nickel cobalt manganese oxide positive electrode material and preparation method therefor, and lithium-ion battery

Abstract

A zirconium-yttrium composite coated modified lithium nickel cobalt manganese oxide positive electrode material and a preparation method therefor, and a lithium-ion battery. The zirconium-yttrium composite coated modified lithium nickel cobalt manganese oxide positive electrode material comprises a lithium nickel cobalt manganese oxide positive electrode material substrate and a zirconium-yttrium composite coating layer coating the surface of the substrate, and the chemical composition of the zirconium-yttrium composite coating layer is ZrzY1-zO1.5+0.5z, where 0.4≤z≤0.8. The surface of the lithium nickel cobalt manganese oxide positive electrode material substrate is coated with the zirconium-yttrium composite coating layer, and the coating layer has high levels of oxygen vacancy and can quickly absorb oxygen generated due to the de-intercalation of lithium ions and the corrosion of an electrolyte to the positive electrode material during an electrochemical reaction process, thereby ensuring the high-temperature storage and cycle performance of the material.

Description

Zirconium-yttrium composite coated modified nickel-cobalt-manganese oxide positive electrode material and preparation method thereof and lithium-ion battery

[0001] Cross-references

[0002] This application claims the priority of Chinese Patent Application No. 202311696209.1 filed on December 11, 2023, entitled “A Zirconium-Yttrium Composite-Coated Modified Nickel-Cobalt-Manganese Oxide Positive Electrode Material, Preparation Method and Lithium-Ion Battery”, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the field of lithium-ion battery materials, and in particular to a zirconium-yttrium composite-coated modified nickel-cobalt-manganese oxide positive electrode material, a preparation method thereof, and a lithium-ion battery. Background Art

[0004] With the development of new energy vehicles, people's demands for longer driving range are constantly increasing. For lithium battery cathode materials, developing high-energy, high-power density, and low-cost lithium-ion batteries is crucial. Ternary nickel-cobalt-manganese oxide cathode materials, due to their low Co content and high capacity, offer significant advantages over lithium cobalt oxide in terms of capacity and cost.

[0005] From the perspective of morphology, lithium nickel cobalt manganese oxide cathode materials are mainly divided into secondary spherical particles and single crystal (high voltage) particles. At present, there are relatively mature preparation methods for materials with these two morphologies. For example, the Chinese patent document with application number 201811382498.7 introduces a preparation method for a high-nickel cathode material, which produces a secondary spherical material. The primary particles of the secondary spheres are smaller and have a higher energy density. However, due to its poor high-temperature cycle performance, rapid growth of high-temperature DCR, and gas production, it is more widely used in the 3C field and less used in the power field. The Chinese patent document with application number 201710883429.3 discloses a preparation method for a single crystal material, which produces a single crystal cathode material. Since the primary particles of the single crystal cathode material are larger and the structure is complete, the anisotropy of the lattice expansion and contraction between the grains during the cycle is weak, and the structural integrity can be maintained during repeated cycles, thereby improving the cyclic stability of the material. Single crystal materials also have a low specific surface area and excellent structural stability, allowing them to withstand higher cutoff voltages (≥4.35V), thus having an energy density comparable to high-nickel materials. They are currently widely used in the new energy industry.

[0006] Generally speaking, as the cut-off voltage of high-voltage ternary cathode materials continues to increase to above 4.35V, the surface of the material will undergo a structural transformation from a layered structure to a spinel and then to a NiO rock salt phase. When lithium ions are repeatedly intercalated and deintercalated, due to the anisotropy of the crystal, intracrystalline cracks will appear inside the material, and the electrolyte can easily enter the interior of the material particles and induce various side reactions on the surface of the particles. These factors will deteriorate the capacity, cycle, rate, gas production and other performance of lithium-ion batteries. Therefore, improving the surface structural stability of high-voltage materials has become an important research topic for high-voltage ternary cathode materials.

[0007] Chinese patent publication CN111509205A discloses a method for preparing a zirconium-coated ternary cathode material for lithium-ion batteries. The method involves coating the surface of the ternary cathode material with ammonium zirconium carbonate via wet mixing, followed by drying and calcination to obtain a zirconium oxide-coated single crystal ternary cathode material. The surface coating reduces side reactions during the electrochemical process and prevents electrolyte corrosion on the surface of the ternary cathode material, thereby enabling the ternary cathode material to maintain good cycle stability and capacity retention. The zirconium oxide coating primarily serves to isolate the electrolyte at conventional voltages, thereby improving the material's cycle stability and capacity retention. However, it has no significant effect on cycle stability and capacity retention at high voltages, particularly in improving storage and gas production performance. Summary of the Invention

[0008] The present application provides a zirconium-yttrium composite-coated modified nickel-cobalt-manganese oxide positive electrode material, a preparation method, and a lithium-ion battery having good high-temperature cycle performance and storage performance and less high-temperature gas production.

[0009] The technical solutions proposed in this application are:

[0010] The first aspect of the present application provides a zirconium-yttrium composite-coated modified nickel cobalt manganese oxide positive electrode material, comprising a nickel cobalt manganese oxide positive electrode material substrate and a zirconium-yttrium composite coating layer coated on the surface of the nickel cobalt manganese oxide positive electrode material substrate, wherein the chemical composition of the zirconium-yttrium composite coating layer is Zr z Y 1-z O 1.5+0.5z , 0.4≤z≤0.8.

[0011] In any embodiment, the chemical composition of the lithium nickel cobalt manganese oxide positive electrode material matrix is ​​Li a Ni b Co c Mn 1-b- c-e M e O2, wherein 1.0≤a≤1.2, 0.5≤b<1, 0<c≤0.1, 0≤e≤0.06, and M includes one or more of Mg, Ti, Zr, Ba, Al, Y, Sr, Nd, W or Ca.

[0012] In any embodiment, the molar ratio of the zirconium-yttrium composite coating layer to the transition metal element in the lithium nickel-cobalt-manganese oxide positive electrode material matrix is ​​0.02% to 0.5%.

[0013] The second aspect of the present application provides a method for preparing the zirconium-yttrium composite-coated modified lithium nickel-cobalt-manganese oxide positive electrode material of the first aspect of the present application, comprising the following steps:

[0014] (1) mixing a nickel-cobalt-manganese hydroxide precursor, a lithium source, and an M-containing compound in a stoichiometric ratio, sintering, and crushing to obtain a nickel-cobalt-manganese oxide lithium positive electrode material matrix;

[0015] (2) mixing the zirconium compound and the yttrium compound uniformly, then adding them into deionized water and stirring them uniformly; after the materials are completely dissolved, adding ammonia water to adjust the pH value, stirring and reacting; then filtering, washing, and freeze-drying the precipitated material obtained by the reaction to obtain a coating agent intermediate;

[0016] (3) The lithium nickel cobalt manganate positive electrode material matrix obtained in step (1) is mixed with the coating agent intermediate obtained in step (2), and then the obtained mixture is sintered to obtain a zirconium yttrium composite coated modified lithium nickel cobalt manganate positive electrode material.

[0017] In any embodiment, in step (1), the lithium source is one or more of lithium carbonate, lithium hydroxide or lithium acetate.

[0018] In any embodiment, the M-containing compound is selected from one or more of M-containing carbonates, M-containing hydroxides, M-containing sulfates, or M-containing oxides.

[0019] In any embodiment, in step (1), the sintering is carried out in an atmosphere of oxygen or air, and the flow rate of the gas is 8m 3 / h~12m 3 / h, the sintering temperature is 700℃~950℃, and the sintering time is 12h~20h.

[0020] In any embodiment, in step (2), the zirconium compound is selected from one or more of zirconium nitrate, zirconium chloride, zirconium sulfate, zirconium oxychloride or zirconium acetate.

[0021] In any embodiment, in step (2), the yttrium compound is selected from one or more of yttrium chloride, yttrium nitrate, yttrium sulfate or yttrium acetate.

[0022] In any embodiment, in step (2), the ratio of the added volume of deionized water to the total amount of the zirconium compound and the yttrium compound is 30 to 50, and the unit of the ratio is mL / mmol.

[0023] In any embodiment, in step (2), the pH value is adjusted to 8.5 to 10.5.

[0024] In any embodiment, in step (2), the temperature for stirring the reaction is 30° C. to 60° C., the reaction time is 6 h to 20 h, and the stirring speed is 100 r / min to 550 r / min.

[0025] In any embodiment, in step (2), the freeze-drying step is to freeze the material at a temperature of -30°C to -50°C for 8 to 10 hours, followed by vacuum drying. The vacuum drying temperature is -20°C to -30°C, the vacuum drying time is 12 to 24 hours, and the vacuum degree is 0.05 mbar to 0.35 mbar, and the vacuum degree is more preferably 0.13 mbar to 0.30 mbar. Freeze-drying can maintain the original state of the material. After drying, the prepared coating agent intermediate has the advantages of large specific surface area, low particle size, and low moisture content.

[0026] In any embodiment, in step (2), the particle size D50 of the coating agent intermediate is 0.01 μm to 0.25 μm, the moisture content is 100 ppm to 400 ppm, and the specific surface area is 30 m 2 / g~60m 2 / g.

[0027] In any embodiment, in step (3), sintering is carried out in a high-oxygen pressure atmosphere furnace, the oxygen pressure of the high-oxygen pressure atmosphere furnace during the sintering process is 6MPa to 12MPa, the sintering temperature is 400°C to 800°C, and the sintering time is 8h to 16h.

[0028] The third aspect of the present application provides a lithium-ion battery, the positive electrode material of which includes the zirconium-yttrium composite-coated modified nickel-cobalt-manganese oxide positive electrode material of the first aspect of the present application or the zirconium-yttrium composite-coated modified nickel-cobalt-manganese oxide positive electrode material obtained by the preparation method of the second aspect of the present application.

[0029] Compared with the prior art, the advantages of this application are:

[0030] (1) The applicant found that in the zirconium-yttrium composite coating layer Zr z Y 1-z O 1.5+0.5zIn the present invention, when z is less than 0.4, the coating structure is unstable, and when it is compounded with the lithium nickel cobalt manganese oxide positive electrode material, it has no effect on improving its cycling and storage performance. When z is greater than 0.8, the formed coating material has fewer oxygen vacancies and has no effect on improving storage and cyclic gas production. The present application coats a zirconium-yttrium composite coating layer on the surface of the lithium nickel cobalt manganese oxide positive electrode material substrate. The coating layer has high oxygen vacancies and can quickly absorb oxygen elements generated by the deintercalation and deintercalation of lithium ions and the corrosion of the positive electrode material by the electrolyte during the electrochemical reaction, thereby reducing or avoiding the side reactions of the oxygen elements with other substances in the electrolyte, thereby reducing the production of CO2 and improving the safety performance of the battery. However, when a single zirconium compound or yttrium compound is used for coating, the oxide formed does not have the characteristics of high oxygen vacancies and has poor absorption of oxygen elements. Compared with using a single zirconium compound or yttrium compound to coat the modified lithium nickel cobalt manganese oxide positive electrode material, the use of the zirconium-yttrium composite coating layer can significantly improve the material's high-temperature storage performance at high voltage and the gas production performance during the cycle.

[0031] (2) The coating agent intermediate prepared by the co-precipitation method and freeze-drying in the present application has the advantages of large specific surface area, low particle size and low moisture content, and can fully contact and adhere to the surface of the nickel cobalt manganese oxide positive electrode material. Combined with the subsequent high oxygen pressure sintering process, it can ensure that the coating layer in the prepared zirconium yttrium composite coated modified nickel cobalt manganese oxide positive electrode material is more uniform, and can expand its contact area with the electrolyte, effectively avoiding the corrosion of the nickel cobalt manganese oxide positive electrode material by the electrolyte on the material surface under high voltage conditions, slowing down the generation of side reactions, and further improving the capacity retention rate of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0033] FIG1 is an XRD pattern of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in Example 1 of the present application.

[0034] FIG2 is an XRD pattern of the modified lithium nickel cobalt manganese oxide positive electrode material prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0035] To facilitate understanding of the present application, the present application will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the scope of protection of the present application is not limited to the following specific embodiments.

[0036] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this application.

[0037] Unless otherwise specified, all reagents and raw materials used in this application are commercially available products or products that can be prepared by known methods.

[0038] Example 1:

[0039] A zirconium-yttrium composite coated modified nickel cobalt manganese oxide positive electrode material of the present application, comprising a nickel cobalt manganese oxide positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 W 0.004 O2 and the zirconium-yttrium composite coating Zr coated on the substrate surface 0.8 Y 0.2 O 1.9 , zirconium-yttrium composite coating Zr 0.8 Y 0.2 O 1.9 The molar ratio of the transition metal element to the matrix material is 0.5%.

[0040] The preparation method of the zirconium-yttrium composite-coated modified lithium nickel-cobalt-manganese oxide positive electrode material in this embodiment includes the following steps:

[0041] (1) According to Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 W 0.004 The stoichiometric ratio of each element in O2 is obtained by mixing nickel cobalt manganese hydroxide precursor, lithium hydroxide and tungsten oxide, and then sintering them in an oxygen atmosphere furnace. During the sintering process, the flow rate is 10m 3 / h of oxygen, the sintering temperature is 920℃, and the sintering is 16h. After the sintering is completed, the sintered material is crushed and sieved to obtain the nickel cobalt manganese oxide lithium positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 W 0.004 O2.

[0042] (2) Mix zirconium acetate and yttrium acetate in a molar ratio of 4:1, mix well, and add deionized water, wherein 35 mL of deionized water is added to every 1 mmol of the zirconium acetate and yttrium acetate mixture. Then place the mixture in a reactor and stir it continuously at a speed of 200 r / min, and control the temperature of the solution to 50 ° C. When there are no obvious solid particles in the solution, inject ammonia water to adjust the pH value so that the pH value is stable at about 9.5. Continue stirring for 8 hours until no solid material precipitates in the solution, stop stirring, and then filter and wash.

[0043] (3) The washings obtained in step (2) were mixed with deionized water, placed in a freezing tube and frozen at -50°C for 10 hours, and then placed in a freeze drying device and the vacuum pump was turned on for freeze drying. During the freeze drying process, the temperature was maintained at -30°C and the vacuum degree was 0.25 mbar. The product was dried for 18 hours to obtain a coating agent intermediate having a D50 of 0.15 μm, a moisture content of 150 ppm, and a specific surface area of ​​45 m 2 / g.

[0044] (4) According to the zirconium yttrium composite coating layer Zr 0.8 Y 0.2 O 1.9 The molar ratio of the transition metal element in the matrix material is 0.5%, and the nickel cobalt manganese oxide lithium positive electrode material matrix obtained in step (1) and the coating agent intermediate obtained in step (3) are directly dry-mixed, and then placed in a high oxygen pressure atmosphere furnace for sintering, the furnace oxygen pressure is controlled to 9 MPa, the sintering temperature is 650 ° C, the sintering time is 12 h, and finally sieved to obtain a zirconium yttrium composite coated modified nickel cobalt manganese oxide lithium positive electrode material.

[0045] The XRD spectrum of the zirconium-yttrium composite-coated modified lithium nickel-cobalt-manganese oxide positive electrode material prepared in this embodiment is shown in FIG1 , wherein the diffraction peak marked by the black triangle is the XRD spectrum of the zirconium-yttrium composite coating layer formed after the coating agent intermediate obtained in step (3) is dehydrated at high temperature.

[0046] Example 2:

[0047] A zirconium-yttrium composite coated modified nickel cobalt manganese oxide positive electrode material of the present application, comprising a nickel cobalt manganese oxide positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 W 0.004 O2 and the zirconium-yttrium composite coating Zr coated on the substrate surface 0.6 Y 0.4 O 1.8 , zirconium-yttrium composite coating Zr 0.6 Y 0.4 O 1.8The molar ratio of the transition metal element to the matrix material is 0.2%.

[0048] The preparation method of the zirconium-yttrium composite-coated modified lithium nickel-cobalt-manganese oxide positive electrode material in this embodiment includes the following steps:

[0049] (1) According to Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 W 0.004 The stoichiometric ratio of each element in O2 is obtained by mixing nickel cobalt manganese hydroxide precursor, lithium hydroxide and tungsten oxide, and then sintering them in an oxygen atmosphere furnace. During the sintering process, the flow rate is 10m 3 / h of oxygen, the sintering temperature is 920℃, and the sintering is 16h. After the sintering is completed, the sintered material is crushed and sieved to obtain the nickel cobalt manganese oxide lithium positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 W 0.004 O2.

[0050] (2) Mix zirconium acetate and yttrium acetate in a molar ratio of 3:2, mix well, and add deionized water, wherein 40 mL of deionized water is added to every 1 mmol of the zirconium acetate and yttrium acetate mixture. Then place the mixture in a reactor and stir it continuously at a speed of 150 r / min, and control the temperature of the solution to 60 ° C. When there are no obvious solid particles in the solution, inject ammonia water to adjust the pH value so that the pH value is fixed at about 10. Stirring is continued for 10 hours until no solid material precipitates in the solution, and then stop stirring. Then filter and wash.

[0051] (3) The washings obtained in step (2) were mixed with deionized water, placed in a freezing tube and frozen at -40°C for 10 hours, and then placed in a freeze drying device and turned on the vacuum pump for freeze drying. During the drying process, the temperature was maintained at -20°C and the vacuum degree was maintained at 0.20 mbar. The product was dried for 18 hours to obtain a coating agent intermediate having a D50 value of 0.18 μm, a moisture content of 160 ppm, and a specific surface area of ​​48 m 2 / g.

[0052] (4) According to the zirconium yttrium composite coating layer Zr 0.6 Y 0.4 O 1.8The molar ratio of the transition metal element in the matrix material is 0.2%, and the nickel cobalt manganese oxide lithium positive electrode material matrix obtained in step (1) and the coating agent intermediate obtained in step (3) are dry-mixed; the mixture is then placed in a high oxygen pressure atmosphere furnace for sintering, the furnace oxygen pressure is controlled to 9 MPa, the sintering temperature is 550° C., the sintering time is 16 h, and finally sieved to obtain a zirconium yttrium composite coated modified nickel cobalt manganese oxide lithium positive electrode material.

[0053] Example 3:

[0054] A zirconium-yttrium composite coated modified nickel cobalt manganese oxide positive electrode material of the present application, comprising a nickel cobalt manganese oxide positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 W 0.004 O2 and the zirconium-yttrium composite coating Zr coated on the substrate surface 0.4 Y 0.6 O 1.7 , zirconium-yttrium composite coating Zr 0.4 Y 0.6 O 1.7 The molar ratio of the transition metal element to the matrix material is 0.06%.

[0055] The preparation method of the zirconium-yttrium composite-coated modified lithium nickel-cobalt-manganese oxide positive electrode material in this embodiment includes the following steps:

[0056] (1) According to Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 W 0.004 The stoichiometric ratio of each element in O2 is obtained by mixing nickel cobalt manganese hydroxide precursor, lithium hydroxide and tungsten oxide, and then sintering them in an oxygen atmosphere furnace. During the sintering process, the flow rate is 10m 3 / h of oxygen, the sintering temperature was controlled to be 920℃, and the sintering was carried out for 16h. After the sintering was completed, the sintered material was crushed and sieved to obtain the nickel cobalt manganese oxide lithium positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 W 0.004 O2.

[0057] (2) Mix zirconium acetate and yttrium acetate in a molar ratio of 2:3, mix well, and add deionized water, wherein 50 mL of deionized water is added to every 1 mmol of the zirconium acetate and yttrium acetate mixture. Then place the mixture in a reactor and stir it continuously at a speed of 350 r / min, and control the temperature of the solution to 40 ° C. When there are no obvious solid particles in the solution, inject ammonia water to adjust the pH value so that the pH value is fixed at about 8.5. Continue stirring for 20 hours until no solid material precipitates in the solution, stop stirring, and then filter and wash.

[0058] (3) The washings obtained in step (2) were mixed with deionized water, placed in a freezing tube and frozen at -50°C for 10 hours, and then the frozen items were placed in a freeze drying device and the vacuum pump was turned on for freeze drying. The temperature during the drying process was maintained at -30°C, the vacuum degree was maintained at 0.30 mbar, and the drying time was 12 hours to obtain a coating agent intermediate having a D50 value of 0.08 μm, a moisture content of 200 ppm, and a specific surface area of ​​50 m 2 / g.

[0059] (4) According to the zirconium yttrium composite coating layer Zr 0.4 Y 0.6 O 1.7 The molar ratio of the transition metal element in the matrix material is 0.06%, and the nickel cobalt manganese oxide lithium positive electrode material matrix obtained in step (1) and the coating agent intermediate obtained in step (3) are directly dry-mixed; the mixture is then placed in a high oxygen pressure atmosphere furnace for sintering, the furnace oxygen pressure is controlled to 9 MPa, the sintering temperature is 750° C., the sintering time is 8 h, and then sieved to obtain a zirconium yttrium composite coated modified nickel cobalt manganese oxide lithium positive electrode material.

[0060] Example 4:

[0061] A zirconium-yttrium composite coated modified nickel cobalt manganese oxide positive electrode material of the present application, comprising a nickel cobalt manganese oxide positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 Ba 0.004 O2 and the zirconium-yttrium composite coating Zr coated on the substrate surface 0.5 Y 0.5 O 1.75 , zirconium-yttrium composite coating Zr 0.5 Y 0.5 O 1.75 The molar ratio of the transition metal element to the matrix material is 0.2%.

[0062] The preparation method of the zirconium-yttrium composite-coated modified lithium nickel-cobalt-manganese oxide positive electrode material in this embodiment includes the following steps:

[0063] (1) According to Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 Ba 0.004 The stoichiometric ratio of each element in O2 is obtained by mixing nickel cobalt manganese hydroxide precursor, lithium hydroxide and barium carbonate, and then sintering them in an oxygen atmosphere furnace. During the sintering process, the flow rate is 10m 3 / h of oxygen, the sintering temperature is 850℃, and the sintering is 16h. After the sintering is completed, the sintered material is crushed and sieved to obtain the nickel cobalt manganese oxide lithium positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 Ba 0.004 O2.

[0064] (2) Mix zirconium acetate and yttrium acetate in a molar ratio of 1:1, mix well and add deionized water, wherein 50 mL of deionized water is added to every 1 mmol of the zirconium acetate and yttrium acetate mixture, then place in a reactor and stir continuously at a speed of 350 r / min, and control the temperature of the solution to 40 ° C. When there are no obvious solid particles in the solution, inject ammonia water to adjust the pH value so that the pH value is fixed at about 8.5, continue stirring for 20 hours, stop stirring when no solid material precipitates in the solution, and then filter and wash.

[0065] (3) The washings obtained in step (2) were mixed with deionized water, placed in a freezing tube and frozen at -40°C for 10 hours, and then placed in a freeze drying device and turned on the vacuum pump for freeze drying. The temperature during the drying process was maintained at -20°C and the vacuum degree was maintained at 0.25 mbar. The product was dried for 24 hours to obtain a coating agent intermediate having a D50 value of 0.10 μm, a moisture content of 100 ppm, and a specific surface area of ​​60 m 2 / g.

[0066] (4) According to the zirconium yttrium composite coating layer Zr 0.5 Y 0.5 O 1.75 The molar ratio of the transition metal element in the matrix material is 0.2%, and the nickel cobalt manganese oxide lithium positive electrode material matrix obtained in step (1) and the coating agent intermediate obtained in step (3) are directly dry-mixed, and then the mixture is placed in a high oxygen pressure atmosphere furnace for sintering, the furnace oxygen pressure is controlled to 12 MPa, the sintering temperature is 750 ° C, the sintering is carried out for 8 hours, and finally sieved to obtain a zirconium yttrium composite coated modified nickel cobalt manganese oxide lithium positive electrode material.

[0067] Example 5:

[0068] A zirconium-yttrium composite coated modified nickel cobalt manganese oxide positive electrode material of the present application, comprising a nickel cobalt manganese oxide positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 Al 0.004 O2 and the zirconium-yttrium composite coating Zr coated on the substrate surface 0.4 Y 0.6 O 1.7 , zirconium-yttrium composite coating Zr 0.4 Y 0.6 O 1.7 The molar ratio of the transition metal element to the matrix material is 0.02%.

[0069] The preparation method of the zirconium-yttrium composite-coated modified lithium nickel-cobalt-manganese oxide positive electrode material in this embodiment includes the following steps:

[0070] (1) According to Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 Al 0.004 The stoichiometric ratio of each element in O2 is obtained by mixing nickel cobalt manganese hydroxide precursor, lithium hydroxide and aluminum hydroxide, and then sintering them in an oxygen atmosphere furnace. During the sintering process, the flow rate is 8m 3 / h of oxygen, the sintering temperature is 850℃, and the sintering is 14h. After the sintering is completed, the sintered material is crushed and sieved to obtain the nickel cobalt manganese oxide positive electrode material matrix Li 1.05 Ni 0.69 Co 0.10 Mn 0.206 Al 0.004 O2.

[0071] (2) Mix zirconium acetate and yttrium acetate in a molar ratio of 2:3, mix well and add deionized water, wherein 50 mL of deionized water is added to every 1 mmol of the zirconium acetate and yttrium acetate mixture, then place in a reactor and stir continuously at a speed of 350 r / min, and control the temperature of the solution to 40 ° C. When there are no obvious solid particles in the solution, inject ammonia water to adjust the pH value so that the pH value is fixed at about 8.5, continue stirring for 20 hours, stop stirring when no solid material precipitates in the solution, and then filter and wash.

[0072] (3) The washings obtained in step (2) were mixed with deionized water, placed in a freezing tube and frozen at -50°C for 10 hours, and then placed in a freeze drying device and turned on the vacuum pump for freeze drying. The temperature during the drying process was maintained at -20°C and the vacuum degree was maintained at 0.25 mbar. The drying was carried out for 12 hours to obtain a coating agent intermediate. The coating agent intermediate had a D50 value of 0.1 μm, a moisture content of 150 ppm, and a specific surface area of ​​50 m2 / g.

[0073] (4) According to the zirconium yttrium composite coating layer Zr 0.4 Y 0.6 O 1.7 The molar ratio of the transition metal element in the matrix material is 0.02%, and the nickel cobalt manganese oxide lithium positive electrode material matrix obtained in step (1) and the coating agent intermediate obtained in step (3) are directly dry-mixed, and then the mixture is placed in a high oxygen pressure atmosphere furnace for sintering, the furnace oxygen pressure is controlled to 6 MPa, the sintering temperature is 750 ° C, the sintering time is 8 hours, and finally sieved to obtain a zirconium yttrium composite coated modified nickel cobalt manganese oxide lithium positive electrode material.

[0074] Comparative Example 1:

[0075] This comparative example differs from Example 1 only in that the molar ratio of zirconium acetate to yttrium acetate in step (2) is changed to 1:4. Other conditions remain the same as in Example 1, thereby obtaining a modified lithium nickel cobalt manganese oxide positive electrode material. The XRD pattern of the modified lithium nickel cobalt manganese oxide positive electrode material is shown in FIG2 . No stable composite coating is formed, and no diffraction peak of the zirconium yttrium composite coating material is observed in the XRD pattern.

[0076] Comparative Example 2:

[0077] Compared with Example 2, this comparative example differs in that the coating agent used in the preparation process is only yttrium acetate, and other conditions are consistent with Example 2, and the obtained positive electrode material is yttrium oxide-coated modified lithium nickel cobalt manganese oxide.

[0078] Comparative Example 3:

[0079] Compared with Example 3, this comparative example differs in that the coating agent used in the preparation process is only zirconium acetate, and other conditions are consistent with Example 3, and the obtained positive electrode material is zirconium oxide coated modified lithium nickel cobalt manganese oxide.

[0080] Comparative Example 4:

[0081] The difference between this comparative example and Example 4 is that zirconium acetate and yttrium acetate are directly mixed as a coating agent, and zirconium acetate and yttrium acetate are not subjected to any treatment. Other conditions are consistent with Example 4, and the coating layer finally formed is zirconium oxide and yttrium oxide.

[0082] Comparative Example 5:

[0083] The difference between this comparative example and Example 5 is that in step (4), the oxygen pressure in the furnace is controlled to be 3 MPa, and the other conditions are consistent with those in Example 5.

[0084] Comparative Example 6:

[0085] The difference between this comparative example and Example 5 is that in step (3), freeze drying is replaced by vacuum oven drying, the drying temperature during the vacuum drying process is 80°C, the vacuum degree is maintained at 0.25 mbar, and the drying is carried out for 12 hours. Other conditions are consistent with Example 5.

[0086] Physical and chemical performance test:

[0087] Positive electrode sheet: The battery positive electrode materials prepared in the above embodiments and comparative examples were added to NMP solvent with conductive carbon black, graphite, and binder PVDF in a mass ratio of 94:2:2:2, mixed evenly, and then coated on Al foil, dried at 120°C for 12 hours, and rolled to prepare a positive electrode sheet.

[0088] Negative electrode sheet: Add graphite, conductive carbon black, CMC, and SBR in a mass ratio of 97:1:1:1 to NMP solvent, mix evenly, and then apply it on Cu foil, dry it at 120°C for 12 hours, and roll it to prepare the negative electrode sheet.

[0089] Battery Assembly: 1.5Ah soft-pack batteries were assembled by assembling the above positive electrode sheets with the negative electrode sheets, separators, and electrolyte. The separator thickness was 20μm. The electrolyte used LiPF6 as the lithium salt, and the solvent volume ratio was ethylene carbonate:ethyl methyl carbonate:diethyl carbonate = 3:5:2. Additives and amounts were: 1.5wt% vinylene carbonate, 1wt% LiPO2F2.

[0090] Electrochemical performance tests were carried out at 25°C and a voltage window of 2.8-4.4V. The specific test regime was as follows: at room temperature of 25°C, charge at 0.33C to the cutoff voltage, maintain constant voltage until the cutoff current was ≤0.005C, stop charging, let stand for 5 minutes, and start discharging at a rate of 0.33C or 1C to a cutoff voltage of 2.8V. The resulting discharge capacities were 0.33C discharge capacity and 1C discharge capacity, respectively. The high-temperature cycle and gas production test regime was as follows: at 45°C, charge at 1C to 4.4V, discharge at 1C to 2.8V, cycle for 1000 weeks, and calculate the capacity retention rate and gas production content. The high-temperature storage gas production test regime was as follows: at 25°C, charge at 1C to 4.4V, then place the battery in a 60°C constant temperature box for 35 days, and calculate the gas production content using the drainage method.

[0091] The electrochemical performance data of the soft-pack batteries assembled with the materials obtained in the above embodiments and comparative examples, such as 0.33C discharge specific capacity, 1C discharge specific capacity, 1000-cycle capacity retention rate, 1000-cycle gas production, and 60°C storage gas production, are shown in Table 1, wherein 1000-cycle gas production refers to the difference between the battery volume after 1000 cycles and the initial battery volume, and 60°C storage gas production refers to the difference between the battery volume after 35 days of storage at 60°C and the initial battery volume.

[0092] Table 1 Electrochemical data of modified nickel cobalt manganese oxide positive electrode materials of various embodiments and comparative examples

[0093] It can be seen from the test data in Table 1 that the zirconium yttrium composite coated modified nickel cobalt manganese oxide positive electrode materials in Examples 1 to 5 have a capacity retention rate of more than 90% at 45°C and 1C cycle for 1000 weeks, and the gas production is less than 2.0 mL / Ah, and the storage gas production at 60°C is less than 0.6 mL / Ah, which shows that the high-temperature cycle performance of the zirconium yttrium composite coated modified nickel cobalt manganese oxide positive electrode material of the present application has been significantly improved, and it also has extremely excellent high-temperature storage performance and gas production performance during the cycle. However, the capacity retention rate, high-temperature cycle gas production performance, and storage gas production performance at 60°C of the modified nickel cobalt manganese oxide positive electrode materials in Comparative Examples 1-6 are very poor at 45°C for 1000 cycles.

[0094] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced with each other and will not be repeated herein for the sake of brevity.

[0095] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material, comprising a nickel-cobalt-manganese-oxide positive electrode material substrate and a zirconium-yttrium composite coating layer coated on the surface of the nickel-cobalt-manganese-oxide positive electrode material substrate, wherein the chemical composition of the zirconium-yttrium composite coating layer is Zr z Y 1-z O 1.5+0.5z , 0.4≤z≤0.

8.

2. The zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to claim 1, wherein: The chemical composition of the nickel cobalt manganese oxide lithium positive electrode material matrix is ​​Li a Ni b Co c Mn 1-b-c-e M e O2, wherein 1.0≤a≤1.2, 0.5≤b<1, 0<c≤0.1, 0≤e≤0.06, and M includes one or more of Mg, Ti, Zr, Ba, Al, Y, Sr, Nd, W or Ca.

3. The zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to claim 1 or 2, wherein: The molar ratio of the zirconium-yttrium composite coating layer to the transition metal element in the nickel-cobalt-manganese-oxide lithium positive electrode material matrix is ​​0.02% to 0.5%.

4. A method for preparing a zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 1 to 3, comprising the following steps: (1) mixing a nickel-cobalt-manganese hydroxide precursor, a lithium source, and an M-containing compound in a stoichiometric ratio, sintering, and crushing to obtain a nickel-cobalt-manganese lithium oxide positive electrode material matrix; (2) mixing the zirconium compound and the yttrium compound uniformly, then adding them into water and stirring them uniformly, after the materials are completely dissolved, adding ammonia water to adjust the pH value, stirring and reacting, and then filtering, washing, and freeze-drying the precipitate obtained by the reaction to obtain a coating agent intermediate; (3) The nickel cobalt manganese oxide positive electrode material matrix obtained in step (1) is mixed with the coating agent intermediate obtained in step (2), and then the obtained mixture is sintered to obtain a zirconium-yttrium composite coated modified nickel cobalt manganese oxide positive electrode material.

5. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to claim 4, wherein: In step (1), the lithium source is one or more of lithium carbonate, lithium hydroxide or lithium acetate.

6. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to claim 4 or 5, wherein: In step (1), the M-containing compound includes one or more of M-containing carbonates, M-containing hydroxides, M-containing sulfates, and M-containing oxides.

7. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 4 to 6, wherein: In step (1), the sintering is carried out in an oxygen or air atmosphere, and the flow rate of the oxygen or air introduced is 8m 3 / h~12m 3 / h, the sintering temperature is 700°C to 950°C, and the sintering time is 12h to 20h.

8. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 4 to 7, wherein: In step (2), the zirconium compound is selected from one or more of zirconium nitrate, zirconium chloride, zirconium sulfate, zirconium oxychloride and zirconium acetate.

9. The method for preparing a zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 4 to 8, wherein: In step (2), the yttrium compound is selected from one or more of yttrium chloride, yttrium nitrate, yttrium sulfate and yttrium acetate.

10. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 4 to 9, wherein: In step (2), the ratio of the added volume of water to the total amount of zirconium compound and yttrium compound is 30 to 50, and the unit of the ratio is mL / mmol.

11. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 4 to 10, wherein: In step (2), the pH value is adjusted to 8.5-10.

5.

12. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 4 to 11, wherein: In step (2), the temperature for stirring the reaction is 30°C to 60°C, the reaction time is 6h to 20h, and the stirring speed is 100r / min to 550r / min.

13. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 4 to 12, wherein: In step (2), the freeze drying refers to first freezing at a temperature of -30°C to -50°C for 8h to 10h, and then vacuum drying. The vacuum drying temperature is -20°C to -30°C, the vacuum drying time is 12h to 24h, and the vacuum degree is 0.05mbar to 0.35mbar.

14. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 4 to 13, wherein: In step (2), the particle size D50 of the coating agent intermediate is 0.01 μm to 0.25 μm, the moisture content is 100 ppm to 400 ppm, and the specific surface area is 30 m 2 / g~60m 2 / g.

15. The method for preparing the zirconium-yttrium composite-coated modified nickel-cobalt-manganese-oxide positive electrode material according to any one of claims 4 to 14, wherein: In step (3), the sintering is carried out in a high oxygen pressure atmosphere furnace. During the sintering process, the oxygen pressure of the high oxygen pressure atmosphere furnace is 6MPa to 12MPa, the sintering temperature is 400°C to 800°C, and the sintering time is 8h to 16h.

16. A lithium-ion battery, wherein the positive electrode material of the lithium-ion battery comprises the zirconium-yttrium composite-coated modified nickel-cobalt-manganese oxide positive electrode material according to any one of claims 1 to 3 or comprises the zirconium-yttrium composite-coated modified nickel-cobalt-manganese oxide positive electrode material obtained by the preparation method according to any one of claims 4 to 15.

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