Positive electrode material, and preparation method therefor and use thereof

Abstract

The present application provides a positive electrode material, and a preparation method therefor and a use thereof. The positive electrode material comprises an inner core and a coating layer arranged on at least part of the surface of the inner core; the inner core comprises oxide of LinNixCoyMnzMmO2, and the coating layer comprises an Sr element and an L element, wherein M is selected from at least one of Zr, Y, Al, Mo, Ta, Ti, Mg, and B, 0.9≤n≤1.2, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.2, 0≤m≤0.05, and x+y+z=1; L is selected from at least one of Al, Ti, B, Zr, Ce, and W; and the mass ratio of the Sr element to a Ni element in the positive electrode material is a, the mass ratio of the Sr element to the Ni element in the coating layer is b, and b / a≥140. The positive electrode material has excellent capacity and stability.

Description

A positive electrode material and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on February 28, 2024, with application number 202410225790.7 and application name “A positive electrode material, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery materials, and in particular to a positive electrode material and a preparation method and application thereof. Background Art

[0003] High-nickel cathode materials are gaining increasing attention in the field of lithium-ion batteries due to their ultra-high specific capacity. However, high-nickel cathode materials have poor stability and a high content of residual lithium on the surface. When used in batteries, they not only affect the preparation of the battery, but also easily react with the electrolyte in the battery, affecting the battery performance.

[0004] The existing technology usually coats the surface of the high-nickel positive electrode material with a coating layer including doping elements to improve the stability of the nickel positive electrode material and reduce the residual lithium content on the surface of the high-nickel positive electrode material. Among them, the Sr element is a common doping element that can effectively improve the stability of the high-nickel positive electrode material, but the Sr element will occupy the active site of the Li element in the high-nickel positive electrode material, which is not conducive to the capacity of the high-nickel positive electrode material.

[0005] Therefore, it is necessary to provide a high nickel cathode material with both excellent capacity and stable performance.

[0006] Application Contents

[0007] The present application provides a positive electrode material having excellent capacity and stability.

[0008] The present application provides a method for preparing the above-mentioned positive electrode material, which can prepare the above-mentioned positive electrode material, and the preparation method is simple to operate and suitable for wide promotion and application.

[0009] The present application provides a battery comprising the above-mentioned positive electrode material, and the battery has excellent discharge specific capacity and cycle performance.

[0010] The present application provides a positive electrode material, wherein the positive electrode material comprises a core and a coating layer provided on at least a portion of the surface of the core;

[0011] The core includes Li n Ni x Co y Mn z M mO2 oxide, the coating layer includes Sr element and L element;

[0012] wherein M is selected from at least one of Zr, Y, Al, Mo, Ta, Ti, Mg, and B; 0.9≤n≤1.2, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.2, 0≤m≤0.05, and x+y+z=1;

[0013] L is at least one selected from Al, Ti, B, Zr, Ce and W;

[0014] The mass ratio of the Sr element to the Ni element in the positive electrode material is a, the mass ratio of the Sr element to the Ni element in the coating layer is b, and b / a≥140.

[0015] The positive electrode material as described above, wherein, in the positive electrode material, the content of the Sr element is 500-5000 ppm, and the content of the L element is 200-6000 ppm.

[0016] The positive electrode material as described above, wherein, in the positive electrode material, the content of the Sr element is 1000-2500 ppm, and the content of the L element is 1000-2000 ppm.

[0017] The positive electrode material as described above, wherein the Dv50 of the positive electrode material is 5-15 μm.

[0018] The positive electrode material as described above, wherein the surface of the positive electrode material has Li + The content of iodine is ≤1500ppm, the content of carbonate ion is ≤2000ppm, and the content of hydroxide ion is ≤4500ppm.

[0019] The present application provides a method for preparing the positive electrode material as described above, which comprises the following steps:

[0020] The core material and the first coating agent are mixed to obtain a mixture, the mixture is washed with water to obtain a first system, and the first system is filtered and dried to obtain a dried material;

[0021] After mixing the dried material with the second coating agent, sintering the mixture to obtain the positive electrode material;

[0022] Wherein, the first coating agent is selected from a strontium source;

[0023] The second coating agent is selected from at least one of a titanium source, a boron source, an aluminum source, a zirconium source, a cerium source and a tungsten source.

[0024] The method for preparing the positive electrode material as described above, wherein the Dv50 of the first coating agent is 2-20 μm; and / or,

[0025] The BET of the first coating agent is greater than 1m 2 / g.

[0026] In the method for preparing the positive electrode material as described above, in the water washing process, the mass ratio of the mixed material to water is (0.5-2):1.

[0027] The method for preparing the positive electrode material as described above, wherein, during the sintering process, the temperature is 250-450° C. and the time is 4-16 hours.

[0028] The present application provides a battery, which includes the positive electrode material as described above.

[0029] In the positive electrode material of the present application, the coating layer containing Sr and L elements can not only improve the stability of the positive electrode material, avoid side reactions between the positive electrode material and the electrolyte, and improve the cycle performance of the battery, but also, due to the low strontium content in the core, the positive electrode material also has excellent capacity, which can improve the discharge specific capacity of the battery.

[0030] The preparation method of the positive electrode material of the present application can obtain the above-mentioned positive electrode material. The preparation method is simple to operate and is suitable for wide promotion and application.

[0031] The battery of the present application comprises the above-mentioned positive electrode material, and the battery has excellent discharge specific capacity and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the following briefly introduces the drawings required for use in the embodiments of this application or related technologies. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0033] FIG1 is a SEM image of the positive electrode material in Example 1 of the present application. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] A first aspect of the present application provides a positive electrode material, wherein the positive electrode material comprises a core and a coating layer provided on at least a portion of the surface of the core;

[0036] The core includes Li n Ni x Co y Mn z M m O2, the coating layer includes Sr and L elements;

[0037] wherein M is selected from at least one of Zr, Y, Al, Mo, Ta, Ti, Mg, and B; 0.9≤n≤1.2, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.2, 0≤m≤0.05, and x+y+z=1;

[0038] L is at least one selected from Al, Ti, B, Zr, Ce and W;

[0039] The mass ratio of the Sr element to the Ni element in the positive electrode material is a, the mass ratio of the Sr element to the Ni element in the coating layer is b, and b / a≥140.

[0040] The cathode material of this application refers to secondary particles formed by the aggregation of primary particles. It is understood that in the cathode material of this application, the coating layer can be provided on at least a portion of the surface of the core, or it can be provided on the entire surface of the core. The cathode material of this application includes, from the inside out, the core and the coating layer.

[0041] The core of the present application includes a molecular formula of Li n Ni x Co y Mn z M m Oxide of O2, the oxide is an oxide of at least Li and Ni, and may also include Co, Mn and M elements. The coating layer of the present application includes Sr element and L element, the Sr element may exist in the form of at least one of an oxide, a boride, a fluoride or a sulfate compound, the L element may exist in the form of at least one of an oxide, a boride, a fluoride or a sulfate compound, and the Sr element and the L element may also exist in the form of a composite compound.

[0042] In the present application, the mass ratio of the Sr element to the Ni element in the positive electrode material can be obtained using conventional methods in the art. In some embodiments, the positive electrode material can be tested using ICP to obtain the mass ratio of the Sr element to the Ni element in the positive electrode material. In the present application, the mass ratio of the Sr element to the Ni element in the coating layer can be obtained using conventional methods in the art. In some embodiments, the positive electrode material can be tested using XPS to obtain the mass ratio of the Sr element to the Ni element in the coating layer.

[0043] In some embodiments of the present application, the Ni element in the cathode material of the present application is distributed in the core, and the Sr element is distributed in the core and the coating layer. The mass ratio of the Sr element to the Ni element in the cathode material, a, and the mass ratio of the Sr element to the Ni element in the coating layer, b, satisfy the following conditions: b / a ≥ 140. This indicates that the strontium element is more concentrated in the coating layer of the cathode material and less embedded in the core. Furthermore, b / a ≥ 180. In some embodiments, 180 ≤ b / a ≤ 1000.

[0044] The positive electrode material of the present application has a coating layer that can improve the stability of the positive electrode material and reduce the residual lithium content on the surface of the positive electrode material, preventing side reactions between the positive electrode material and the electrolyte. At the same time, the strontium element is more enriched in the coating layer of the positive electrode material and less embedded in the core, so the core can provide greater capacity for the positive electrode material. Therefore, the positive electrode material of the present application has excellent stability and capacity. When used in a battery, it can improve the battery's cycle performance and discharge specific capacity.

[0045] In some embodiments of the present application, when the content of the Sr element in the positive electrode material is 500-5000 ppm and the content of the L element is 200-6000 ppm, the positive electrode material has more excellent electrochemical performance. Furthermore, the content of the Sr element in the positive electrode material is 1000-2500 ppm and the content of the L element is 1000-2000 ppm.

[0046] In some embodiments of the present application, the Dv50 of the positive electrode material is 5-15 μm.

[0047] When the Dv50 of the positive electrode material is within the above range, the lithium ion migration efficiency of the positive electrode material can be improved while ensuring the compaction density of the positive electrode material, thereby improving the electrochemical performance of the positive electrode material.

[0048] The applicant also found that the surface of the positive electrode material has Li + The content of iodine is ≤1500ppm, the content of carbonate ion is ≤2000ppm, and the content of hydroxide ion is ≤4500ppm.

[0049] This application can use acid-base titration to obtain the surface Li of the positive electrode material + When the surface lithium ion content of the positive electrode material is less than or equal to 1500ppm, the positive electrode material is less likely to undergo side reactions with the electrolyte when used in the battery, thereby improving the battery's cycle performance. When the surface carbonate content of the positive electrode material is ≤2000ppm and the hydroxide content is ≤4500ppm, it indicates that the surface residual alkali content of the positive electrode material is low. When used in the battery, the battery is less likely to produce gas after long-term cycling, and has better cycle performance.

[0050] The second aspect of the present application provides a method for preparing the positive electrode material of the first aspect, comprising the following steps:

[0051] The core material and the first coating agent are mixed to obtain a mixture, the mixture is washed with water to obtain a first system, and the first system is filtered and dried to obtain a dried material;

[0052] After mixing the dried material with the second coating agent, sintering is performed to obtain a positive electrode material;

[0053] wherein the first coating agent is selected from a strontium source;

[0054] The second coating agent is selected from at least one of a titanium source, a boron source, an aluminum source, a zirconium source, a cerium source and a tungsten source.

[0055] Specifically, the core material and the first strontium source coating agent are mixed evenly, and the strontium source is coated on at least a portion of the surface of the core material to obtain a mixture, and then the mixture is washed with water. During the washing process, the free Li + It will dissolve and react with the Sr element coated on the surface of the core material to generate low-solubility Sr(OH)2, constructing a local strong alkaline environment and inhibiting the Li + With H + exchange, thereby preventing lithium ions in the core material from being released and increasing the capacity of the positive electrode material; then filtering the first system to obtain a precipitate, drying the precipitate to obtain a dried material of the core material preliminarily coated with the strontium source;

[0056] Then, the dried material is mixed with the second coating agent and then sintered to form a coating layer on the surface of the core material, thereby obtaining a positive electrode material including the core and the coating layer.

[0057] The present application does not impose any particular limitation on the strontium source, which may be a strontium-containing compound commonly used in the art. The present application does not impose any particular limitation on the titanium source, which may be a titanium-containing compound commonly used in the art. The present application does not impose any particular limitation on the boron source, which may be a boron-containing compound commonly used in the art. The present application does not impose any particular limitation on the aluminum source, which may be an aluminum-containing compound commonly used in the art. The present application does not impose any particular limitation on the zirconium source, which may be a zirconium-containing compound commonly used in the art. The present application does not impose any particular limitation on the cerium source, which may be a cerium-containing compound commonly used in the art. The present application does not impose any particular limitation on the tungsten source, which may be a tungsten-containing compound commonly used in the art.

[0058] In some embodiments, when the strontium source, titanium source, boron source, aluminum source, zirconium source, cerium source, and tungsten source only include the corresponding metal elements and at least one of C, H, and O, the C, H, and O elements are easily decomposed or generated into gas and removed during the subsequent sintering process, and no additional impurities are introduced into the reaction system, which helps to obtain a positive electrode material with higher purity.

[0059] Exemplarily, when the strontium source includes only Sr and at least one of C, H, and O, the C, H, and O elements are easily decomposed or generated during the subsequent sintering process to remove gas, and no additional impurities are introduced into the reaction system, which helps to obtain a positive electrode material with higher purity. In some embodiments, the strontium source can be at least one of strontium acetate, strontium oxide, and strontium hydroxide. Specifically, when the strontium source is strontium acetate, the acetate ions in the strontium acetate will decompose and generate CO2 during subsequent sintering and be removed.

[0060] The present application does not impose any particular limitation on the sintering process, and the sintering process may be performed using methods commonly used in the art. In some embodiments, the sintering process may be performed in an oxygen atmosphere.

[0061] The present application first adopts a wet method to coat the coating layer on the surface of the core material, and uses the residual lithium of the core material to react with strontium, which not only removes the residual lithium on the surface of the core material, but also achieves the initial coating of strontium, which can prevent the strontium element from entering the interior of the core material, thereby avoiding the capacity decrease of the positive electrode material, and can also improve the uniformity of the coating; at the same time, the solvent of the present application is only water, which can avoid the use of organic solvents, and the preparation method is more green and economical.

[0062] During the research, the applicant found that when the Dv50 of the first coating agent is 2-20 μm, the particle size of the first coating agent is appropriate and not easy to break, which can reduce the first coating agent from entering the core material along the grain boundary gaps of the core material, thereby improving the coating uniformity; and even if part of the first coating agent is broken, the particle size formed after the breakage is also appropriate, and it is still not easy to enter the core material along the grain boundary gaps of the core material, thereby improving the coating uniformity, and then improving the capacity and stability of the positive electrode material.

[0063] In some embodiments of the present application, when the BET of the first coating agent is greater than 1 m 2 / g, the first coating agent has a larger contact area with the surface of the core material, can be more easily coated on the surface of the core material, and can also increase the reaction surface between the Sr source and water, which is conducive to faster construction of a local strong alkaline environment, reducing the dissolution of lithium ions, and increasing the capacity of the positive electrode material.

[0064] In some embodiments of the present application, during the water washing process, when the mass ratio of the mixture to water is (0.5-2):1, the residual lithium on the surface of the core material can be fully removed while ensuring that the core material is not excessively dissolved, thereby improving the capacity and stability of the positive electrode material.

[0065] In some embodiments of the present application, during the sintering process, when the temperature is 250-450°C and the time is 4-16 hours, the lower temperature can uniformly form a coating layer on the surface of the core material, and it is not easy for strontium elements to enter the core material, thereby obtaining a positive electrode material with excellent capacity and stability.

[0066] A third aspect of the present application provides a battery comprising the positive electrode material of the first aspect.

[0067] It is understood that in the present application, the positive electrode material can be prepared into a positive electrode sheet using a method commonly used in the art, and then the positive electrode sheet and the negative electrode sheet can be assembled to obtain a battery.

[0068] The battery of the present application, because it includes the positive electrode material of the first aspect, has excellent cycle performance and discharge specific capacity.

[0069] The technical solution of the present application will be further explained below with reference to specific embodiments.

[0070] Example 1

[0071] The positive electrode material of this embodiment is prepared by a method comprising the following steps:

[0072] Ni 0.92 Co 0.04 Mn 0.04 After (OH)2 was mixed evenly with LiOH, ZrO2, TiO2, and Y2O3 in a molar ratio of 1:1.04:0.002:0.001:0.0005, the temperature was raised to 720°C at 2°C / min in an oxygen atmosphere and maintained for 12 hours to obtain the core material Li 1.01 Ni 0.92 Co 0.04 Mn 0.04 Zr 0.002 Ti 0.001 Y 0.001 O2;

[0073] The core material and SrO are uniformly mixed in a molar ratio of 1:0.0015 to obtain a mixture, the mixture is washed with deionized water to obtain a first system, the first system is filtered, and the filter residue is vacuum dried to obtain a dried material;

[0074] The dried material was evenly mixed with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, and the temperature was raised to 350°C at 2°C / min in an oxygen atmosphere and maintained for 8 hours to obtain a positive electrode material including a coating layer;

[0075] Among them, in the water washing process, the mass ratio of deionized water to mixed material is 1:0.8;

[0076] The Dv50 of SrO is 3 μm and the BET is 1.31 μm. 2 / g;

[0077] The Dv50 of the positive electrode material is 9.5 μm.

[0078] The surface morphology of the positive electrode material in this embodiment was observed using SEM. FIG1 is a SEM image of the positive electrode material in Example 1 of the present application.

[0079] Example 2

[0080] The positive electrode material of this embodiment is prepared by a method comprising the following steps:

[0081] Ni 0.90 Co 0.05 Mn 0.05 After (OH)2 was mixed evenly with LiOH, ZrO2, TiO2, and Y2O3 in a molar ratio of 1:1.04:0.001:0.001:0.0005, the temperature was raised to 720°C at 2°C / min in an oxygen atmosphere and maintained for 12 hours to obtain the core material Li 1.01 Ni 0.9 Co 0.05 Mn 0.05 Zr 0.001 Ti 0.001 Y 0.001 O2;

[0082] The core material and Sr(OH)2 are uniformly mixed in a molar ratio of 1:0.001 to obtain a mixture, the mixture is washed with deionized water to obtain a first system, the first system is filtered, and the filter residue is vacuum dried to obtain a dried material;

[0083] The dried material was evenly mixed with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, and the temperature was raised to 350°C at 2°C / min in an oxygen atmosphere and maintained for 8 hours to obtain a positive electrode material including a coating layer;

[0084] In the water washing process, the mass ratio of deionized water to the mixed material is 1:1;

[0085] The Dv50 of Sr(OH)2 is 2.6μm and the BET is 2.05m 2 / g;

[0086] The Dv50 of the positive electrode material is 8.9μm.

[0087] Example 3

[0088] The positive electrode material of this embodiment is prepared by a method comprising the following steps:

[0089] Ni 0.94 Co 0.04 Mn 0.02 After (OH)2 was mixed evenly with LiOH, ZrO2, TiO2, Y2O3, and MgO in a molar ratio of 1:1.04:0.002:0.001:0.0005:0.001, the temperature was raised to 720°C at 2°C / min in an oxygen atmosphere and maintained for 12 h to obtain the core material Li 1.01 Ni 0.94 Co 0.04 Mn 0.02 Zr 0.002 Ti 0.001 Y 0.001 Mg 0.001 O2;

[0090] The core material and strontium acetate are uniformly mixed in a molar ratio of 1:0.002, the mixture is washed with deionized water to obtain a first system, the first system is filtered, and the filter residue is vacuum dried to obtain a dried material;

[0091] The dried material was evenly mixed with B2O3 and Al2O3 in a molar ratio of 1:0.005:0.002, and the temperature was raised to 380°C at 2°C / min in an oxygen atmosphere and maintained for 8 hours to obtain a positive electrode material including a coating layer.

[0092] Among them, in the water washing process, the mass ratio of deionized water to mixed material is 1:0.8;

[0093] The Dv50 of strontium acetate is 4.2 μm and the BET is 1.03 m 2 / g;

[0094] The Dv50 of the positive electrode material is 10.1 μm.

[0095] Example 4

[0096] The positive electrode material of this embodiment is prepared by a method comprising the following steps:

[0097] Ni 0.91 Co 0.05 Mn 0.04After (OH)2 was mixed evenly with LiOH, ZrO2, and Y2O3 in a molar ratio of 1:1.04:0.002:0.0005, the temperature was raised to 720°C at 2°C / min in an oxygen atmosphere and maintained for 12 hours to obtain the core material Li 1.01 Ni 0.91 Co 0.05 Mn 0.04 Zr 0.002 Y 0.001 O2;

[0098] The core material and SrO are uniformly mixed in a molar ratio of 1:0.0015 to obtain a mixture, the mixture is washed with deionized water to obtain a first system, the first system is filtered, and the filter residue is vacuum dried to obtain a dried material;

[0099] The dried material was evenly mixed with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, and the temperature was raised to 350°C at 2°C / min in an oxygen atmosphere and maintained for 8 hours to obtain a positive electrode material including a coating layer;

[0100] Among them, in the water washing process, the mass ratio of deionized water to mixed material is 1:0.8;

[0101] The Dv50 of SrO is 3 μm and the BET is 1.31 μm. 2 / g;

[0102] The Dv50 of the positive electrode material is 10 μm.

[0103] Example 5

[0104] The positive electrode material of this embodiment is prepared by a method comprising the following steps:

[0105] Ni 0.93 Co 0.04 Mn 0.03 After (OH)2 was mixed evenly with LiOH, ZrO2, TiO2, and Y2O3 in a molar ratio of 1:1.04:0.002:0.0015:0.0005, the temperature was raised to 720°C at 2°C / min in an oxygen atmosphere and maintained for 12 hours to obtain the core material Li 1.01 Ni 0.93 Co 0.04 Mn 0.03 Zr 0.002 Ti 0.0015 Y 0.001 O2;

[0106] The core material and SrO are uniformly mixed in a molar ratio of 1:0.0015 to obtain a mixture, the mixture is washed with deionized water to obtain a first system, the first system is filtered, and the filter residue is vacuum dried to obtain a dried material;

[0107] The dried material was evenly mixed with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, and the temperature was raised to 350°C at 2°C / min in an oxygen atmosphere and maintained for 8 hours to obtain a positive electrode material including a coating layer;

[0108] Among them, in the water washing process, the mass ratio of deionized water to mixed material is 1:0.8;

[0109] The Dv50 of SrO is 3 μm and the BET is 1.31 μm. 2 / g;

[0110] The Dv50 of the positive electrode material is 9.5 μm.

[0111] Example 6

[0112] The positive electrode material of this embodiment is prepared by a method comprising the following steps:

[0113] Ni 0.92 Co 0.04 Mn 0.04 After (OH)2 was mixed evenly with LiOH, ZrO2, TiO2, and Y2O3 in a molar ratio of 1:1.04:0.002:0.001:0.0005, the temperature was raised to 720°C at 2°C / min in an oxygen atmosphere and maintained for 12 hours to obtain the core material Li 1.01 Ni 0.92 Co 0.04 Mn 0.04 Zr 0.002 Ti 0.001 Y 0.001 O2;

[0114] The core material and SrO are uniformly mixed in a molar ratio of 1:0.0015 to obtain a mixture, the mixture is washed with deionized water to obtain a first system, the first system is filtered, and the filter residue is vacuum dried to obtain a dried material;

[0115] The dried material was evenly mixed with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, and the temperature was raised to 350°C at 2°C / min in an oxygen atmosphere and maintained for 8 hours to obtain a positive electrode material including a coating layer;

[0116] Among them, in the water washing process, the mass ratio of deionized water to mixed material is 1:0.8;

[0117] The Dv50 of SrO is 5 μm and the BET is 1.01 μm. 2 / g;

[0118] The Dv50 of the positive electrode material is 15 μm.

[0119] Example 7

[0120] The preparation method of the positive electrode material of this embodiment is basically the same as that of Example 1, except that:

[0121] In the water washing process, the mass ratio of deionized water to the mixed material is 1:0.5.

[0122] Example 8

[0123] The preparation method of the positive electrode material of this embodiment is basically the same as that of Example 1, except that:

[0124] In the water washing process, the mass ratio of deionized water to the mixed material is 1:2.

[0125] Example 9

[0126] The preparation method of the positive electrode material of this embodiment is basically the same as that of Example 1, except that:

[0127] In the water washing process, the mass ratio of deionized water to the mixed material is 1:0.4.

[0128] Example 10

[0129] The preparation method of the positive electrode material of this embodiment is basically the same as that of Example 1, except that:

[0130] In the water washing process, the mass ratio of deionized water to the mixed material is 1:2.2.

[0131] Example 11

[0132] The preparation method of the positive electrode material of this embodiment is basically the same as that of Example 1, except that:

[0133] The molar ratio of the core material to SrO is 1:0.003.

[0134] Example 12

[0135] The preparation method of the positive electrode material of this embodiment is basically the same as that of Example 2, except that:

[0136] The dried material was evenly mixed with ZrO2, WO3, and CeO2 in a molar ratio of 1:0.0015:0.001:0.001, and the temperature was raised to 450°C at a rate of 2°C / min in an oxygen atmosphere and maintained for 8 hours to obtain a positive electrode material including a coating layer.

[0137] Example 13

[0138] The preparation method of the positive electrode material of this embodiment is basically the same as that of Example 1, except that:

[0139] The molar ratio of the core material to SrO is 1:0.0006.

[0140] Comparative Example 1

[0141] The preparation method of the positive electrode material of this comparative example is basically the same as that of Example 1, except that:

[0142] The core material is directly washed with water.

[0143] Comparative Example 2

[0144] The positive electrode material of this comparative example was prepared by a method comprising the following steps:

[0145] Ni 0.92 Co 0.04 Mn 0.04 After (OH)2 was mixed evenly with LiOH, ZrO2, TiO2, Y2O3, and SrO in a molar ratio of 1:1.04:0.002:0.001:0.0005:0.0015, the temperature was raised to 720°C at 2°C / min in an oxygen atmosphere and maintained for 12 h to obtain the core material Li 1.01 Ni 0.92 Co 0.04 Mn 0.04 Zr 0.002 Ti 0.001 Y 0.001 Sr 0.0015 O2;

[0146] The core material is washed with deionized water to obtain a first system, the first system is filtered, and the filter residue is vacuum dried to obtain a dried material;

[0147] The dried material was evenly mixed with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, and the temperature was raised to 350°C at 2°C / min in an oxygen atmosphere and maintained for 8 hours to obtain a high-nickel positive electrode material including a coating layer.

[0148] Among them, in the water washing process, the mass ratio of deionized water to core raw material is 1:0.8.

[0149] The Dv50 of the positive electrode material is 9.5 μm.

[0150] Performance Testing

[0151] The following performance tests were performed on the positive electrode materials in the examples and comparative examples. The results are shown in Table 1.

[0152] 1. ICP test and XPS test

[0153] ICP was used to test the mass ratio a of Sr element to Ni element in the positive electrode material, the content of Sr element and the content of L element in the positive electrode material; XPS was used to test the mass ratio b of Sr element to Ni element in the coating layer.

[0154] 2. Surface lithium ion content, carbonate content, OH - content

[0155] Tested in accordance with GB / T 41704-2022.

[0156] 3. Discharge specific capacity

[0157] The positive electrode material, conductive agent Super-P, and binder PVDF were mixed in a mass ratio of 96.5:1.5:2 and added to NMP solvent to mix evenly to obtain a positive electrode slurry with a solid content of 30-40%. The positive electrode slurry was heated at a temperature of about 20 mg / cm 2 The surface density of the positive electrode is coated on the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained by drying, punching and rolling.

[0158] The above-mentioned positive electrode sheet, PP separator, and metal lithium sheet were stacked in sequence, and 1.0M LiPF6 electrolyte was added to assemble into an LR2430 button cell. The following performance of the obtained button cell was measured:

[0159] At room temperature, the button cell was charged at a constant current of 0.2C to 4.25V, then charged at a constant voltage of 4.25V to a cutoff current of 0.05C. After standing for 5 minutes, the cell was discharged at a constant current of 0.2C to 2.5V, and the discharge specific capacity of the cell was recorded; where 1C = 200mA / g.

[0160] 4. Capacity retention rate after 200 cycles

[0161] The positive electrode sheet, PP separator, and commercially available graphite negative electrode sheet in 3 were stacked in sequence and wound to obtain a battery cell. The battery cell was encapsulated in an aluminum-plastic film, injected with 1.0M LiPF6 electrolyte, and the encapsulated cell was allowed to stand for formation to obtain a full battery. The following performance tests were performed on the obtained full battery:

[0162] Place the full battery in a 45°C constant temperature chamber and first charge it at a constant current of 0.2C to 4.25V. Then charge it at a constant voltage of 4.25V to a cutoff current of 0.05C. After standing for 5 minutes, discharge it at a constant current of 0.2C to 2.8V. Record the initial capacity a1 of the battery. Then, perform a charge-discharge cycle of 0.2C charge / 0.2C discharge. After 200 cycles, record the capacity a2 of the battery. The capacity retention rate is a2 / a1×100%. Where 1C = 200mA / g.

[0163] Table 1

[0164] As can be seen from Table 1, the battery in the embodiment of the present application has a more excellent discharge specific capacity and cycle performance, indicating that the positive electrode material with a special structure in the present application can improve the overall performance of the battery when applied to the battery;

[0165] Furthermore, it can be seen from Comparative Examples 1 and 2 that when the positive electrode material includes a coating layer containing Sr and L elements, the battery has better cycle performance. The reason is that the coating layer can improve the stability of the positive electrode material, reduce the residual lithium content on the surface of the positive electrode material, and prevent the positive electrode material from reacting with the electrolyte, thereby improving the cycle performance of the battery. However, the presence of the coating layer will reduce the discharge capacity of the battery.

[0166] It can be seen from Example 1 and Comparative Example 2 that the battery in Example 1 has a more excellent discharge specific capacity and cycle performance, indicating that only when the mass ratio of the Sr element to the Ni element in the positive electrode material and the mass ratio of the Sr element to the Ni element in the coating layer meet a specific relationship can the battery have both excellent discharge specific capacity and cycle performance. The reason is that when the mass ratio of the Sr element to the Ni element in the positive electrode material and the mass ratio of the Sr element to the Ni element in the coating layer meet a specific relationship, it means that the strontium element is more enriched in the coating layer of the positive electrode material and less embedded in the core. Therefore, the core can provide capacity for the positive electrode material to a greater extent. Therefore, the positive electrode material of the present application has both excellent stability and capacity, and when applied to a battery, it can improve the battery's cycle performance and discharge specific capacity.

[0167] It can be seen from Examples 1, 7-8 and 9-10 that by regulating the mass ratio of the mixture to water in the water washing process, a positive electrode material with better overall performance can be obtained, thereby improving the overall performance of the battery.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A positive electrode material, characterized in that The positive electrode material includes a core and a coating layer provided on at least a portion of the surface of the core; The core includes Li n Ni x Co y Mn z M m O2 oxide, the coating layer includes Sr element and L element; wherein M is selected from at least one of Zr, Y, Al, Mo, Ta, Ti, Mg, and B; 0.9≤n≤1.2, 0.8≤x≤1, 0≤y≤0.2, 0≤z≤0.2, 0≤m≤0.05, and x+y+z=1; L is at least one selected from Al, Ti, B, Zr, Ce and W; The mass ratio of the Sr element to the Ni element in the positive electrode material is a, the mass ratio of the Sr element to the Ni element in the coating layer is b, and b / a≥140.

2. The positive electrode material according to claim 1, characterized in that In the positive electrode material, the content of Sr element is 500-5000 ppm, and the content of L element is 200-6000 ppm.

3. The positive electrode material according to claim 2, characterized in that In the positive electrode material, the content of Sr element is 1000-2500 ppm, and the content of L element is 1000-2000 ppm.

4. The positive electrode material according to claim 1 or 2, characterized in that The Dv50 of the positive electrode material is 5-15 μm.

5. The positive electrode material according to any one of claims 1, 2 or 4, characterized in that On the surface of the positive electrode material, Li + The content of iodine is ≤1500ppm, the content of carbonate ion is ≤2000ppm, and the content of hydroxide ion is ≤4500ppm.

6. A method for preparing the positive electrode material according to any one of claims 1 to 5, characterized in that: The following steps are involved: Mixing the core material and the first coating agent to obtain a mixture, washing the mixture with water to obtain a first system, and filtering and drying the first system to obtain a dried material; After mixing the dried material with the second coating agent, sintering the mixture to obtain the positive electrode material; Wherein, the first coating agent is selected from a strontium source; The second coating agent is selected from at least one of a titanium source, a boron source, an aluminum source, a zirconium source, a cerium source and a tungsten source.

7. The method for preparing the positive electrode material according to claim 6, wherein: The Dv50 of the first coating agent is 2-20 μm.

8. The method for preparing the positive electrode material according to claim 6 or 7, characterized in that: The BET of the first coating agent is greater than 1m 2 / g.

9. The method for preparing a positive electrode material according to any one of claims 6 to 8, characterized in that: In the water washing process, the mass ratio of the mixture to water is (0.5-2):

1.

10. The method for preparing a positive electrode material according to any one of claims 6 to 9, characterized in that: During the sintering process, the temperature is 250-450° C. and the time is 4-16 hours.

11. A battery, characterized in that: The positive electrode material comprises the positive electrode material according to any one of claims 1 to 5.

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