A cathode material, a preparation method thereof, and an application thereof

Abstract

The present invention provides a cathode material, a preparation method thereof and an application. The cathode material includes a core and a coating layer provided on at least a part of the surface of the core; the core includes an oxide of Li n Ni x Co y Mn z M m O2, and 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 selected from at least one of Al, Ti, B, Zr, Ce and W; the mass ratio of Sr element to Ni element in the cathode material is a, and the mass ratio of Sr element to Ni element in the coating layer is b, and b / a ≥ 140. This cathode material has excellent capacity and stable performance.

Description

Technical Field

[0001] The present invention relates to a cathode material, a preparation method thereof and an application, belonging to the technical field of secondary batteries. Background Art

[0002] High-nickel cathode materials have attracted 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 relatively high surface residual lithium content. When applied to batteries, they not only affect the preparation of the batteries but also easily react with the electrolyte in the batteries, affecting the battery performance.

[0003] Existing technologies usually coat a coating layer including doped elements on the surface of high-nickel cathode materials to improve the stability of the nickel cathode materials and reduce the surface residual lithium content of the high-nickel cathode materials. Among them, Sr element is a common doping element that can effectively improve the stability of high-nickel cathode materials. However, the Sr element will occupy the active sites of Li elements in the high-nickel cathode materials, which is not conducive to the capacity of the high-nickel cathode materials.

[0004] Therefore, it is necessary to provide a high-nickel cathode material with both excellent capacity and stable performance. Summary of the Invention

[0005] The present invention provides a cathode material, which has excellent capacity and stable performance.

[0006] The present invention provides a preparation method of the above cathode material. The preparation method can prepare the above cathode material, and the preparation method is simple to operate and suitable for wide promotion and application.

[0007] The present invention provides a battery, including the above cathode material. The battery has excellent discharge specific capacity and cycling performance.

[0008] The present invention provides a cathode material, wherein the cathode material includes a core and a coating layer provided on at least a part of the surface of the core;

[0009] The core includes an oxide of Li n Ni x Co y Mn z M m O2, and the coating layer includes Sr element and L element;

[0010] 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;

[0011] L is selected from at least one of Al, Ti, B, Zr, Ce, and W;

[0012] The mass ratio of Sr element to Ni element in the positive electrode material is a, and the mass ratio of Sr element to Ni element in the coating layer is b, where b / a ≥ 140.

[0013] The positive electrode material as described above, wherein, in the positive electrode material, the content of Sr element is 500 - 5000 ppm, and the content of L element is 200 - 6000 ppm.

[0014] The positive electrode material as described above, wherein the Dv50 of the positive electrode material is 5 - 15 μm.

[0015] The positive electrode material as described above, wherein, on the surface of the positive electrode material, the content of Li + is ≤ 1500 ppm, the content of carbonate is ≤ 2000 ppm, and the content of hydroxide is ≤ 4500 ppm.

[0016] The present invention provides a method for preparing the positive electrode material as described above, which includes the following steps:

[0017] Mix the core material and the first coating agent to obtain a mixture, wash the mixture with water to obtain a first system, and filter and dry the first system to obtain a dried material;

[0018] After mixing the dried material with the second coating agent, perform a sintering treatment to obtain the positive electrode material;

[0019] Wherein, the first coating agent is selected from strontium sources;

[0020] The second coating agent is selected from at least one of titanium sources, boron sources, aluminum sources, zirconium sources, cerium sources, and tungsten sources.

[0021] 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,

[0022] The BET of the first coating agent > 1 m 2 / g.

[0023] The method for preparing the positive electrode material as described above, wherein, in the washing treatment, the mass ratio of the mixture to water is (0.5 - 2):1.

[0024] The method for preparing the positive electrode material as described above, wherein, in the sintering treatment, the temperature is 250 - 450 °C and the time is 4 - 16 h.

[0025] The present invention provides a battery, which includes the positive electrode material as described above.

[0026] In the positive electrode material of the present invention, the coating layer containing Sr element and L element 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. At the same time, since the strontium content in the core is small, this positive electrode material also has excellent capacity and can improve the discharge specific capacity of the battery.

[0027] The preparation method of the positive electrode material of the present invention can obtain the above positive electrode material. This preparation method is simple to operate and is suitable for wide promotion and application.

[0028] The battery of the present invention includes the above positive electrode material. This battery has excellent discharge specific capacity and cycle performance. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention or related technologies. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is the SEM diagram of the positive electrode material in Embodiment 1 of the present invention. Detailed Embodiments

[0031] To make the purpose, technical solutions and advantages of the present invention clearer, the following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0032] The first aspect of the present invention provides a positive electrode material. Among them, the positive electrode material includes a core and a coating layer provided on at least part of the surface of the core;

[0033] The core includes Li n Ni x Co y Mn z M m O2, and the coating layer includes Sr element and L element;

[0034] Among them, 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;

[0035] L is selected from at least one of Al, Ti, B, Zr, Ce, and W;

[0036] The mass ratio of Sr element to Ni element in the cathode material is a, and the mass ratio of Sr element to Ni element in the coating layer is b, where b / a ≥ 140.

[0037] The cathode material of the present invention refers to secondary particles formed by aggregation of primary particles. It can be understood that in the cathode material of the present invention, the coating layer can be provided on at least a part of the surface of the core, or can be provided on the entire surface of the core. The cathode material of the present invention includes a core and a coating layer from the inside out.

[0038] The core of the present invention includes an oxide with the molecular formula Li n Ni x Co y Mn z M m O2, and this oxide is an oxide containing at least Li and Ni, and may also include Co, Mn, and M elements. The coating layer of the present invention includes Sr element and L element. The Sr element can exist in at least one form of oxide, boride, fluoride, or sulfate compound, and the L element can exist in at least one form of oxide, boride, fluoride, or sulfate compound. The Sr element and the L element can also exist in the form of a composite compound.

[0039] In the present invention, conventional methods in the art can be used to obtain the mass ratio of Sr element to Ni element in the cathode material. In some embodiments, ICP can be used to test the cathode material to obtain the mass ratio of Sr element to Ni element in the cathode material. The present invention can use conventional methods in the art to obtain the mass ratio of Sr element to Ni element in the coating layer. In some embodiments, XPS can be used to test the cathode material to obtain the mass ratio of Sr element to Ni element in the coating layer.

[0040] The mass ratio a of Sr element to Ni element in the cathode material of the present invention and the mass ratio b of Sr element to Ni element in the coating layer satisfy: b / a ≥ 140. This shows that strontium element is more enriched in the coating layer of the cathode material and less embedded in the core. Further, b / a ≥ 180, and in some embodiments, 180 ≤ b / a ≤ 1000.

[0041] The positive electrode material of the present invention has a coating layer that can improve the stability of the positive electrode material, and the coating layer can 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, strontium elements are 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 invention has both excellent stability and capacity, and can improve the cycle performance and discharge specific capacity of the battery when applied to the battery.

[0042] In some embodiments of the present invention, when the content of Sr element in the positive electrode material is 500 - 5000 ppm and the content of L element is 200 - 6000 ppm, the positive electrode material has more excellent electrochemical performance. Further, the content of Sr element in the positive electrode material is 1000 - 2500 ppm.

[0043] In some embodiments of the present invention, the Dv50 of the positive electrode material is 5 - 15 μm.

[0044] When the Dv50 of the positive electrode material is within the above range, it can improve the lithium ion migration efficiency of the positive electrode material while ensuring the tap density of the positive electrode material, thereby improving the electrochemical performance of the positive electrode material.

[0045] The inventor also found that on the surface of the positive electrode material, the content of Li + ≤ 1500 ppm, the content of carbonate ≤ 2000 ppm, and the content of hydroxide ≤ 4500 ppm.

[0046] The present invention can use acid-base titration to obtain the content of Li + on the surface of the positive electrode material, the content of carbonate, and the content of hydroxide. When the lithium ion content on the surface of the positive electrode material is less than or equal to 1500 ppm, the positive electrode material is less likely to have side reactions with the electrolyte when applied to the battery, improving the cycle performance of the battery. When the content of carbonate on the surface of the positive electrode material ≤ 2000 ppm and the content of hydroxide ≤ 4500 ppm, it indicates that the surface residual alkali content of the positive electrode material is low, and the battery is not likely to generate gas after long-term cycling when applied to the battery, having more excellent cycle performance.

[0047] The second aspect of the present invention provides a preparation method of the positive electrode material of the first aspect, including the following steps:

[0048] Mix the core material and the first coating agent to obtain a mixture, wash the mixture with water to obtain a first system, and perform filtration and drying on the first system to obtain a dried material;

[0049] Mix the dried material with the second coating agent and then perform sintering treatment to obtain the positive electrode material;

[0050] Among them, the first coating agent is selected from strontium sources;

[0051] The second coating agent is selected from at least one of titanium sources, boron sources, aluminum sources, zirconium sources, cerium sources, and tungsten sources.

[0052] Specifically, the core material and the strontium source first coating agent are mixed evenly so that the strontium source is coated on at least part of the surface of the core material to obtain a mixture. Then, the mixture is subjected to a water washing treatment. During the water washing treatment, free Li + will dissolve, thereby reacting with the Sr element coated on the surface of the core material to generate Sr(OH)2 with low solubility, constructing a locally strong alkaline environment, and inhibiting the exchange of Li + with H + in the positive electrode material, avoiding the lithium ion extraction from the core material, and improving the capacity of the positive electrode material; then, the first system is filtered to obtain a precipitate, and the precipitate is dried to obtain a dried material with the strontium source preliminarily coated on the core material;

[0053] Then, the dried material is mixed with the second coating agent and then sintered, so as to form a coating layer on the surface of the core material, and a positive electrode material including a core and a coating layer is obtained.

[0054] The present invention does not make a special limitation on the strontium source, and the strontium source can be a commonly used strontium-containing compound in the art. The present invention does not make a special limitation on the titanium source, and it can be a commonly used titanium-containing compound in the art. The present invention does not make a special limitation on the boron source, and it can be a commonly used boron-containing compound in the art. The present invention does not make a special limitation on the aluminum source, and it can be a commonly used aluminum-containing compound in the art. The present invention does not make a special limitation on the zirconium source, and it can be a commonly used zirconium-containing compound in the art. The present invention does not make a special limitation on the cerium source, and it can be a commonly used cerium-containing compound in the art. The present invention does not make a special limitation on the tungsten source, and it can be a commonly used tungsten-containing compound in the art.

[0055] 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 element and at least one of C, H, and O, the C, H, and O elements are easily decomposed or generate gases and are removed during the subsequent sintering process, and no extra impurities are introduced into the reaction system, which helps to obtain a positive electrode material with higher purity.

[0056] Exemplarily, when the strontium source only includes the Sr element and at least one of C, H, and O, the C, H, and O elements are easily decomposed or generate gases and are removed during the subsequent sintering process, and no extra 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 strontium acetate will decompose into CO2 and be removed during the subsequent sintering.

[0057] The present invention does not make special limitations on the sintering treatment, and the sintering treatment can be carried out by using the methods commonly used in the art. In some embodiments, the sintering treatment can be carried out in an oxygen atmosphere.

[0058] In the present invention, a coating layer is first coated on the surface of the core material by a wet method, and the residual lithium of the core material reacts with strontium, which not only removes the surface residual lithium of the core material, but also realizes the preliminary coating of strontium, which can avoid strontium elements from entering the interior of the core material, thereby avoiding the capacity decline of the cathode material, and can also improve the coating uniformity; at the same time, the solvent of the present invention is only water, which can avoid the use of organic solvents, and the preparation method is more green and economical.

[0059] The inventors found in the research 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 entry of the first coating agent into 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 breaks, the particle size formed after breaking is also appropriate and still not easy to enter the core material along the grain boundary gaps of the core material, thereby improving the coating uniformity, and further improving the capacity and stability of the cathode material.

[0060] In some embodiments of the present invention, when the BET of the first coating agent > 1 m 2 / g, the first coating agent and the surface of the core material have a larger contact surface, can be more easily coated on the surface of the core material, and can also increase the reaction surface of the Sr source and water, which is beneficial to constructing a local strong alkaline environment faster, reducing the dissolution of lithium ions, and improving the capacity of the cathode material.

[0061] In some embodiments of the present invention, in the water washing treatment, 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 dissolved too much, thereby improving the capacity and stability of the cathode material.

[0062] In some embodiments of the present invention, in the sintering treatment, when the temperature is 250-450 °C and the time is 4-16 h, a lower temperature can uniformly form a coating layer on the surface of the core material and is not easy to make strontium elements enter the core material, thereby obtaining a cathode material with excellent capacity and stability.

[0063] The third aspect of the present invention provides a battery, including the cathode material of the first aspect.

[0064] It can be understood that in the present invention, the cathode material can be prepared into a cathode sheet by using the methods commonly used in the art, and then the cathode sheet and the anode sheet are assembled to obtain a battery.

[0065] The battery of the present invention, due to including the positive electrode material of the first aspect, has excellent cycle performance and discharge specific capacity.

[0066] Hereinafter, the technical solution of the present invention will be further explained and illustrated in conjunction with specific embodiments.

[0067] Example 1

[0068] The positive electrode material of this example is prepared by a method including the following steps:

[0069] Mix Ni 0.92 Co 0.04 Mn 0.04 (OH)2 with LiOH, ZrO2, TiO2, Y2O3 in a molar ratio of 1:1.04:0.002:0.001:0.0005, and after mixing evenly, heat it to 720 °C at a rate of 2 °C / min in an oxygen atmosphere and keep it 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 O2;

[0070] Mix the core material with SrO in a molar ratio of 1:0.0015 evenly to obtain a mixture, wash the mixture with deionized water to obtain a first system, filter the first system, and vacuum-dry the filter residue to obtain a dried material;

[0071] Mix the dried material with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002 evenly, heat it to 350 °C at a rate of 2 °C / min in an oxygen atmosphere and keep it for 8 h to obtain the positive electrode material including a coating layer;

[0072] Among them, in the washing treatment, the mass ratio of deionized water to the mixture is 1:0.8;

[0073] The Dv50 of SrO is 3 μm, and the BET is 1.31 m 2 / g;

[0074] The Dv50 of the positive electrode material is 9.5 μm.

[0075] Use SEM to observe the surface morphology of the positive electrode material in this example, Figure 1 It is the SEM image of the positive electrode material in Example 1 of the present invention.

[0076] Example 2

[0077] The positive electrode material of this example is prepared by a method including the following steps:

[0078] Mix Ni 0.90 Co 0.05 Mn 0.05 (OH)2 with LiOH, ZrO2, TiO2, Y2O3 in a molar ratio of 1:1.04:0.001:0.001:0.0005, mix evenly, and then heat to 720 °C at a rate of 2 °C / min in an oxygen atmosphere and hold for 12 h to obtain the core material Li 1.01 Ni 0. 9Co 0.05 Mn 0.05 Zr 0.001 Ti 0.001 Y 0.001 O2;

[0079] Mix the core material with Sr(OH)2 in a molar ratio of 1:0.001 to obtain a mixture. Wash the mixture with deionized water to obtain the first system, filter the first system, and vacuum dry the filter residue to obtain the dried material;

[0080] Mix the dried material with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, heat to 350 °C at a rate of 2 °C / min in an oxygen atmosphere, and hold for 8 h to obtain the cathode material including the coating layer;

[0081] Among them, in the washing treatment, the mass ratio of deionized water to the mixture is 1:1;

[0082] The Dv50 of Sr(OH)2 is 2.6 μm and the BET is 2.05 m 2 / g;

[0083] The Dv50 of the cathode material is 8.9 μm.

[0084] Example 3

[0085] The cathode material of this example is prepared by a method including the following steps:

[0086] Mix Ni 0.94 Co 0.04 Mn 0.02 (OH)2 with LiOH, ZrO2, TiO2, Y2O3, MgO in a molar ratio of 1:1.04:0.002:0.001:0.0005:0.001, mix evenly, and then heat to 720 °C at a rate of 2 °C / min in an oxygen atmosphere and hold 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 Mg0.001 O2;

[0087] Mix the core material and strontium acetate evenly at a molar ratio of 1:0.002 to obtain a mixture. Wash the mixture with deionized water to obtain the first system. Filter the first system, and vacuum-dry the filter residue to obtain a dried material.

[0088] Mix the dried material, B2O3, and Al2O3 evenly at a molar ratio of 1:0.005:0.002, and heat it to 380°C at a rate of 2°C / min in an oxygen atmosphere and hold for 8 h to obtain a cathode material including a coating layer.

[0089] Among them, in the washing treatment, the mass ratio of deionized water to the mixture is 1:0.8.

[0090] The Dv50 of strontium acetate is 4.2 μm, and the BET is 1.03 m 2 / g;

[0091] The Dv50 of the cathode material is 10.1 μm.

[0092] Example 4

[0093] The cathode material of this example is prepared by a method including the following steps:

[0094] Mix Ni 0.91 Co 0.05 Mn 0.04 (OH)2, LiOH, ZrO2, and Y2O3 evenly at a molar ratio of 1:1.04:0.002:0.0005, and then heat it to 720°C at a rate of 2°C / min in an oxygen atmosphere and hold for 12 h to obtain the core material Li 1.01 Ni 0.91 Co 0.05 Mn 0.04 Zr 0.002 Y 0.001 O2;

[0095] Mix the core material and SrO evenly at a molar ratio of 1:0.0015 to obtain a mixture. Wash the mixture with deionized water to obtain the first system. Filter the first system, and vacuum-dry the filter residue to obtain a dried material.

[0096] Mix the dried material, H3BO3, and Al2O3 evenly at a molar ratio of 1:0.01:0.002, and heat it to 350°C at a rate of 2°C / min in an oxygen atmosphere and hold for 8 h to obtain a cathode material including a coating layer;

[0097] Among them, in the washing treatment, the mass ratio of deionized water to the mixture is 1:0.8.

[0098] The Dv50 of SrO is 3 μm, and the BET is 1.31 m 2 / g;

[0099] The Dv50 of the cathode material is 10 μm.

[0100] Example 5

[0101] The cathode material of this example is prepared by a method including the following steps:

[0102] Mix Ni 0.93 Co 0.04 Mn 0.03 (OH)2 with LiOH, ZrO2, TiO2, Y2O3 in a molar ratio of 1:1.04:0.002:0.0015:0.0005, and after mixing evenly, heat it to 720 °C at a rate of 2 °C / min in an oxygen atmosphere and keep it for 12 h 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;

[0103] Mix the core material with SrO in a molar ratio of 1:0.0015 to obtain a mixture, wash the mixture with deionized water to obtain the first system, filter the first system, and vacuum dry the filter residue to obtain the dried material;

[0104] Mix the dried material with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, heat it to 350 °C at a rate of 2 °C / min in an oxygen atmosphere and keep it for 8 h to obtain the cathode material including the coating layer;

[0105] Among them, in the washing treatment, the mass ratio of deionized water to the mixture is 1:0.8;

[0106] The Dv50 of SrO is 3 μm, and the BET is 1.31 m 2 / g;

[0107] The Dv50 of the cathode material is 9.5 μm.

[0108] Example 6

[0109] The cathode material of this example is prepared by a method including the following steps:

[0110] Mix Ni 0.92 Co 0.04 Mn 0.04(OH)2 is mixed evenly with LiOH, ZrO2, TiO2, and Y2O3 in a molar ratio of 1:1.04:0.002:0.001:0.0005, and then heated to 720 °C at a rate of 2 °C / min in an oxygen atmosphere and held 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 O2;

[0111] The core material is mixed evenly with SrO in a molar ratio of 1:0.0015 to obtain a mixture. The mixture is washed with deionized water to obtain a first system, and the first system is filtered. The filter residue is dried in vacuo to obtain a dried material;

[0112] The dried material is mixed evenly with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, and then heated to 350 °C at a rate of 2 °C / min in an oxygen atmosphere and held for 8 h to obtain a cathode material including a coating layer;

[0113] Among them, in the washing treatment, the mass ratio of deionized water to the mixture is 1:0.8;

[0114] The Dv50 of SrO is 5 μm, and the BET is 1.01 m 2 / g;

[0115] The Dv50 of the cathode material is 15 μm.

[0116] Example 7

[0117] The preparation method of the cathode material in this example is basically the same as that in Example 1, except that:

[0118] In the washing treatment, the mass ratio of deionized water to the mixture is 1:0.5.

[0119] Example 8

[0120] The preparation method of the cathode material in this example is basically the same as that in Example 1, except that:

[0121] In the washing treatment, the mass ratio of deionized water to the mixture is 1:2.

[0122] Example 9

[0123] The preparation method of the cathode material in this example is basically the same as that in Example 1, except that:

[0124] In the washing treatment, the mass ratio of deionized water to the mixture is 1:0.4.

[0125] Example 10

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

[0127] In the water washing treatment, the mass ratio of deionized water to the mixed material is 1:2.2.

[0128] Comparative Example 1

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

[0130] The core material is directly subjected to water washing treatment.

[0131] Comparative Example 2

[0132] The positive electrode material in this comparative example is prepared by a method including the following steps:

[0133] Mix Ni 0.92 Co 0.04 Mn 0.04 (OH)2 with LiOH, ZrO2, TiO2, Y2O3, SrO in a molar ratio of 1:1.04:0.002:0.001:0.0005:0.0015, and after mixing evenly, heat it to 720 °C at a rate of 2 °C / min in an oxygen atmosphere and keep it 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;

[0134] Use deionized water to wash the core material to obtain the first system, filter the first system, and vacuum dry the filter residue to obtain the dried material;

[0135] Mix the dried material with H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002, and heat it to 350 °C at a rate of 2 °C / min in an oxygen atmosphere and keep it for 8 h to obtain a high-nickel positive electrode material including a coating layer.

[0136] Among them, in the water washing treatment, the mass ratio of deionized water to the core raw material is 1:0.8.

[0137] The Dv50 of the positive electrode material is 9.5 μm.

[0138] Performance Test

[0139] Perform the following performance tests on the positive electrode materials in the examples and comparative examples, and the results are shown in Table 1;

[0140] 1. ICP test and XPS test

[0141] Use ICP to test the mass ratio a of Sr element to Ni element in the cathode material, the content of Sr element and the content of L element in the cathode material; use XPS to test that the mass ratio of Sr element to Ni element in the coating layer is b.

[0142] 2. Surface lithium ion content, carbonate content, OH - content

[0143] Test according to GB / T 41704-2022.

[0144] 3. Discharge specific capacity

[0145] Mix the cathode material, conductive agent Super-P, and binder PVDF in a mass ratio of 96.5:1.5:2 and add them to NMP solvent to mix evenly to obtain a cathode slurry with a solid content of 30-40%. Coating the cathode slurry on the cathode current collector aluminum foil at a surface density of about 20mg / cm 2 , and successively go through drying - punching - rolling to obtain the cathode sheet;

[0146] Stack the above-mentioned cathode sheet, PP separator, and metallic lithium sheet in sequence, add 1.0M LiPF6 electrolyte to assemble an LR2430 type button cell, and conduct the following performance measurements on the obtained button cell:

[0147] At room temperature, charge the button cell at a constant current of 0.2C to 4.25V, then charge it at a constant voltage of 4.25V until the cut-off current is equal to 0.05C, let it stand for 5 minutes and then discharge it at a constant current of 0.2C to 2.5V, and record the discharge specific capacity of the battery; among them, 1C = 200mA / g.

[0148] 4. Capacity retention rate after 200 cycles

[0149] Stack the cathode sheet, PP separator, and commercially available graphite anode sheet in sequence in 3, wind them up to obtain an electric core, encapsulate the electric core in an aluminum-plastic film, inject 1.0M LiPF6 electrolyte, and after encapsulation and standing, carry out formation to obtain a full cell, and conduct the following performance tests on the obtained full cell:

[0150] Place the full cell in a 45°C constant temperature oven. First, charge it at a constant current of 0.2C to 4.25V, then charge it at a constant voltage of 4.25V until the cut-off current is 0.05C, let it stand for 5 minutes and then discharge it at a constant current of 0.2C to 2.8V, record the initial capacity a1 of the battery, then carry out charge and discharge cycles of 0.2C charge / 0.2C discharge, after 200 cycles, record the capacity of the battery as a2, and the capacity retention rate is a2 / a1×100%. Among them, 1C = 200mA / g.

[0151] Table 1

[0152]

[0153] As can be seen from Table 1, the battery in the embodiment of the present invention has more excellent discharge specific capacity and cycle performance, indicating that the cathode material with a special structure in the present invention can improve the comprehensive performance of the battery when applied to the battery;

[0154] Furthermore, as can be seen from Comparative Example 1 and Comparative Example 2, when the cathode material includes a coating layer containing Sr element and L element, the battery has more excellent cycle performance. The reason is that the coating layer can improve the stability of the cathode material, reduce the surface residual lithium content of the cathode material, and prevent side reactions between the cathode material and the electrolyte, thereby improving the cycle performance of the battery. However, the presence of the coating layer will reduce the discharge specific capacity of the battery;

[0155] As can be seen from Example 1 and Comparative Example 2, the battery in Example 1 has more excellent discharge specific capacity and cycle performance, indicating that only when the mass ratio of Sr element to Ni element in the cathode material and the mass ratio of Sr element to Ni element in the coating layer satisfy specific relationships can the battery have both excellent discharge specific capacity and cycle performance. The reason is that when the mass ratio of Sr element to Ni element in the cathode material and the mass ratio of Sr element to Ni element in the coating layer satisfy specific relationships, it indicates that strontium element is more enriched in the coating layer of the cathode material and less embedded in the core. Therefore, the core can provide capacity for the cathode material to a greater extent. Therefore, the cathode material of the present invention has both excellent stability and capacity, and can improve the cycle performance and discharge specific capacity of the battery when applied to the battery;

[0156] As can be seen from Example 1, Examples 7-8 and Examples 9-10, by adjusting the mass ratio of the mixture to water in the water washing treatment, a cathode material with more excellent comprehensive performance can be obtained, thereby improving the comprehensive performance of the battery.

[0157] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cathode material, characterized in that, The positive electrode material includes a core and a coating layer provided on at least a part of the surface of the core; The core includes Li n Ni x Co y Mn z M m oxide of O2, and 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 selected from at least one of Al, Ti, B, Zr, Ce, and W; The mass ratio of Sr element to Ni element in the positive electrode material is a, and the mass ratio of Sr element to Ni element in the coating layer is b, and b / a ≥ 140.

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

4. The cathode material according to any one of claims 1-3, characterized in that, In the surface of the positive electrode material, the content of Li + is ≤ 1500 ppm, the content of carbonate is ≤ 2000 ppm, and the content of hydroxide is ≤ 4500 ppm.

5. A method for preparing the cathode material according to any one of claims 1-4, characterized in that, It includes the following steps: Mix the core material and the first coating agent to obtain a mixture, wash the mixture with water to obtain a first system, and filter and dry the first system to obtain a dried material; After mixing the dried material with the second coating agent, perform a sintering treatment to obtain the positive electrode material; wherein, the first coating agent is selected from strontium sources; The second coating agent is selected from at least one of titanium sources, boron sources, aluminum sources, zirconium sources, cerium sources, and tungsten sources.

6. The method for preparing the positive electrode material according to claim 5, characterized in that, The Dv50 of the first coating agent is 2 - 20 μm.

7. The method for preparing the cathode material according to claim 5, characterized in that, The BET of the first coating agent > 1 m 2 / g.

8. The method for preparing the cathode material according to any one of claims 5-7, characterized in that, In the washing treatment, the mass ratio of the mixture to water is (0.5 - 2):

1.

9. The preparation method of the cathode material according to any one of claims 5-7, characterized in that, In the sintering treatment, the temperature is 250 - 450 °C, and the time is 4 - 16 h.

10. A battery, characterized in that, It includes the positive electrode material according to any one of claims 1 - 4.

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