Ternary precursor having core-shell structure, positive electrode material and preparation method

Abstract

A ternary precursor having a core-shell structure, a positive electrode material and a preparation method. The chemical formula of the ternary precursor having a core-shell structure is NixCoyMz(OH)2, wherein 0<x<1, 0≤y<1, 0<z<1, x+y+z＝1, and M comprises Mn and / or Al. The shell layer thickness of the ternary precursor having a core-shell structure is 0.1-2 μm. In the method, the ternary precursor having a special core-shell structure is formed by means of a step-by-step coprecipitation method; the particle sphericity degree of the ternary precursor is high; and the positive electrode material formed by means of sintering does not show the phenomenon of core-shell separation and has the advantages of both energy density and safety.

Description

A core-shell structure ternary precursor, positive electrode material and preparation method Technical Field

[0001] The embodiments of the present application relate to the field of battery technology, such as a precursor material, and more particularly to a core-shell structure ternary precursor, a positive electrode material, and a preparation method. Background Art

[0002] Lithium-ion batteries, with their high energy density, excellent rate performance, and low self-discharge, have become a widely used power and energy storage device in our lives. With the rapid development of the automotive industry, green new energy vehicles are becoming the industry's most promising development direction. Therefore, improving the battery life and energy storage capacity of lithium batteries in new energy vehicles, the energy density per unit volume of lithium battery materials, battery safety, and service life have become the most pressing technical issues in the industry.

[0003] Nickel-cobalt-manganese ternary precursors and cathode materials are important components of lithium batteries and are the main factors that determine the performance of lithium batteries. In the ternary precursors, the performance of lithium battery materials can be adjusted by designing different nickel-cobalt-manganese ratios. Among them, Co in the ternary cathode material can stabilize the layered structure of the material, but its cost is relatively high; Ni in the ternary material can mainly increase the capacity and improve the energy density of the battery, but as the Ni content increases, the nickel-lithium mixing phenomenon is serious, which hinders the performance of Li + Diffusion reduces the discharge capacity and rate performance. At the same time, the increase in nickel content causes phase change during the charge and discharge process, which reduces thermal stability and cycle performance, thereby affecting the service life and safety of power lithium batteries for new energy vehicles.

[0004] By adjusting the structure of the precursor material and controlling the ratio of the core to the shell, it is theoretically possible to increase energy density while maintaining good discharge capacity, cycle performance, and rate capability. However, in actual use, it was found that during long-cycle charge and discharge, irregular gaps or holes appeared at the interface between the core and shell of the core-shell cathode material, defeating the purpose of the core-shell material.

[0005] To this end, it is necessary to provide a core-shell structured ternary precursor, positive electrode material and preparation method with uniform particle sphericity and good morphology, and no core-shell separation phenomenon in the sintered positive electrode material, which can take into account both energy density and safety performance.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] The embodiments of the present application provide a core-shell structured ternary precursor, a cathode material and a preparation method. The ternary precursor has a uniform morphology and good sphericity. The obtained cathode material can inherit the structure of the ternary precursor and will not show the phenomenon of core-shell separation, having the advantages of兼顾 energy density and safety.

[0009] In the first aspect, the embodiments of the present application provide a core-shell structured ternary precursor, and the chemical formula of the core-shell structured ternary precursor is Ni x Co y M z (OH)2, where 0 < x < 1, 0 ≤ y < 1, 0 < z < 1, and x + y + z = 1. M includes Mn and / or Al;

[0010] The shell layer thickness of the core-shell structured ternary precursor is 0.1 - 2 μm.

[0011] The core-shell structured ternary precursor provided by the present application consists of a core and a shell layer, and the thickness of the shell layer is 0.1 - 2 μm. For example, it can be 0.1 μm, 0.3 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm, 1.8 μm or 2 μm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable, and preferably 0.5 - 2 μm.

[0012] The chemical formula of the core-shell structured ternary precursor provided by the present application is Ni x Co y M z (OH)2, and this chemical formula is obtained by weighting the core composition and the shell composition according to mass percentages. For the core-shell structured ternary precursor provided by the present application, by controlling the thickness of the shell layer, it can not only ensure the sphericity of the ternary precursor particles but also avoid the phenomenon of core-shell separation, enabling the subsequent prepared cathode material to have the advantages of兼顾 energy density and safety.

[0013] Preferably, the chemical formula of the core-shell structured ternary precursor is Ni x Co y M z (OH)2, where 0.75 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.15, and 0.05 ≤ z ≤ 0.1.

[0014] In the chemical formula of the core-shell structured ternary precursor, the value range of x is 0.75 ≤ x ≤ 0.9. For example, it can be 0.75, 0.78, 0.8, 0.82, 0.85, 0.88 or 0.9, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0015] It should be noted that the "兼顾" in the original text seems to be an incorrect or incomplete expression. I translated it as "兼顾" as it is, but it might need to be corrected or further defined in the context.In the chemical formula of the core-shell structure ternary precursor, the value range of y is 0.05≤y≤0.15, for example, it can be 0.05, 0.06, 0.08, 0.1, 0.12 or 0.15, but is not limited to the listed values. Other values ​​not listed in the numerical range are also applicable.

[0016] In the chemical formula of the core-shell structure ternary precursor, the value range of z is 0.05≤z≤0.1, for example, it can be 0.05, 0.06, 0.08, 0.09 or 0.1, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0017] Preferably, the core-shell structure ternary precursor comprises a core and a shell;

[0018] The nickel content of the core is higher than that of the shell.

[0019] The core-shell structured ternary precursor provided in this application provides high capacity for the corresponding cathode material by having a high nickel content in the core; the shell has a low nickel content, which provides structural stability. Combined with the thickness of the shell in this application, the sphericity of the ternary precursor particles can be guaranteed while avoiding core-shell separation, thereby maximizing the advantages of spacing energy density and safety of the resulting cathode material.

[0020] In a second aspect, an embodiment of the present application provides a method for preparing the core-shell structure ternary precursor as described in the first aspect, the preparation method comprising the following steps:

[0021] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles of a target particle size are obtained;

[0022] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to react to obtain a core-shell structure ternary precursor having a shell thickness that meets the requirements;

[0023] The atomic mole percentage of nickel atoms in the first salt solution is higher than the atomic mole percentage of nickel atoms in the second salt solution.

[0024] The preparation method provided in the present application is simple to operate, and a core-shell structure precursor having a core and a shell is prepared by a step-by-step co-precipitation method. The preparation process has low energy consumption and meets the requirements of industrial production.

[0025] Preferably, the target particle size D50 of the core particles in step (1) reaches 2-18 μm, for example, it can be 2 μm, 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 16 μm or 18 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the target particle size D50 of the core-shell structure ternary precursor in step (2) reaches 2.1-20 μm, for example, it can be 2.1 μm, 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 16 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the metal ions in the first salt solution include any one or a combination of at least two of Ni, Co, Mn or Al. Typical but non-limiting combinations include a combination of Ni and Co, a combination of Ni, Co and manganese, a combination of Ni, Co and Al, or a combination of Ni, Co, Mn and Al.

[0028] The metal ions in the first salt solution of the present application are provided by soluble metal salts, and the soluble metal salts include any one or a combination of at least two of sulfates, chlorides, nitrates or aluminates. Typical but non-limiting combinations include a combination of sulfates and chlorides, a combination of chlorides and nitrates, a combination of nitrates and aluminates, a combination of sulfates, chlorides and nitrates, a combination of chlorides, nitrates and aluminates, or a combination of sulfates, chlorides, nitrates and aluminates.

[0029] The total concentration of metal ions in the first salt solution is 1-5 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the metal ions in the second salt solution include any one or a combination of at least two of Ni, Co, Mn or Al. Typical but non-limiting combinations include a combination of Ni and Co, a combination of Ni, Co and manganese, a combination of Ni, Co and Al, or a combination of Ni, Co, Mn and Al.

[0031] The metal ions in the second salt solution of the present application are provided by soluble metal salts, and the soluble metal salts include any one or a combination of at least two of sulfates, chlorides, nitrates or aluminates. Typical but non-limiting combinations include a combination of sulfates and chlorides, a combination of chlorides and nitrates, a combination of nitrates and aluminates, a combination of sulfates, chlorides and nitrates, a combination of chlorides, nitrates and aluminates, or a combination of sulfates, chlorides, nitrates and aluminates.

[0032] The total concentration of metal ions in the second salt solution is 1-5 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the complexing agent in the complexing agent solution includes any one of ammonia, citric acid, ethylenediaminetetraacetic acid, oxalic acid or sodium pyrophosphate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of ammonia and sodium pyrophosphate, a combination of citric acid and ethylenediaminetetraacetic acid, a combination of citric acid and oxalic acid, or a combination of citric acid, ethylenediaminetetraacetic acid and oxalic acid.

[0034] Preferably, the concentration of the complexing agent solution is 1-3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the precipitant in the precipitant solution includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide or sodium carbonate. Typical but non-limiting combinations include a combination of sodium hydroxide and potassium hydroxide, a combination of potassium hydroxide and sodium carbonate, a combination of sodium hydroxide and sodium carbonate, or a combination of sodium hydroxide, potassium hydroxide and sodium carbonate.

[0036] Preferably, the OH in the precipitant solution - The concentration is 1-3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the reaction temperature in step (1) is 35-70°C, for example, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the reaction in step (1) is carried out under stirring conditions, and the stirring speed is 200-500 r / min, for example, it can be 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min or 500 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, during the reaction in step (1), the pH value is maintained at 8-13, for example, 8, 9, 10, 11, 12 or 13, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, during the reaction in step (1), the concentration of the complexing agent is maintained at 1-20 g / L, for example, 1 g / L, 2 g / L, 4 g / L, 5 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 15 g / L, 16 g / L, 18 g / L or 20 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the reaction temperature in step (2) is 35-70°C, for example, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, the reaction in step (2) is carried out under stirring conditions, and the stirring speed is 100-400 r / min, for example, it can be 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min or 400 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, during the reaction in step (2), the pH value is maintained at 8-13, for example, 8, 9, 10, 11, 12 or 13, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 11.5-13.

[0044] Preferably, during the reaction in step (2), the concentration of the complexing agent is maintained at 1-20 g / L, for example, 1 g / L, 2 g / L, 4 g / L, 5 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 15 g / L, 16 g / L, 18 g / L or 20 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] The base solution described herein is composed of water, a complexing agent, and a precipitant. The concentrations of the complexing agent and the precipitant in the base solution correspond to the pH value and concentration of the complexing agent required to be maintained during the reaction. For example, when the reaction requires a pH of 10 and a complexing agent concentration of 10 g / L, the concentration of the complexing agent in the base solution is 10 g / L, and the pH of the base solution is 10.

[0046] In a third aspect, an embodiment of the present application provides a positive electrode material, which is prepared from the core-shell structure ternary precursor described in the first aspect.

[0047] In a fourth aspect, an embodiment of the present application provides a method for preparing the positive electrode material as described in the third aspect, the preparation method comprising:

[0048] The lithium source and the core-shell structure ternary precursor are uniformly mixed and sintered in an oxygen atmosphere to obtain the positive electrode material.

[0049] The amount of lithium source used in this application is the amount of lithium source required to fully react the core-shell structure ternary precursor, and this application does not make any specific restrictions here.

[0050] The sintering temperature described in the fourth aspect of the present application is 500-1000°C, for example, it can be 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] The sintering time described in the fourth aspect of this application is 6-20 hours, for example, it can be 6 hours, 8 hours, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours or 20 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] The preparation method described in the fourth aspect further includes conventional cooling, crushing and screening in the art after sintering, and this application does not make too many restrictions on this.

[0053] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0054] The core-shell structured ternary precursor provided in the embodiments of the present application provides high capacity for the corresponding cathode material by having a high nickel content in the core; the shell has a low nickel content, which provides structural stability. The thickness of the shell layer in the present application can not only ensure the sphericity of the ternary precursor particles, but also avoid the phenomenon of core-shell separation, thereby achieving the advantages of spacing energy density and safety of the subsequent cathode material.

[0055] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0057] Figure 1 shows the core-shell structure Ni in Example 1 0.9 Co 0.05 Mn0.05 EPMA diagram of Ni element in the cross section of (OH)2;

[0058] Figure 2 shows the core-shell structure Ni in Example 1 0.9 Co 0.05 Mn 0.05 EPMA diagram of Co element in the cross section of (OH)2. DETAILED DESCRIPTION

[0059] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0060] Example 1

[0061] This embodiment provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0062] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles with a particle size D50 of 11 μm are obtained;

[0063] The first salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the total concentration of nickel, cobalt and manganese is 3 mol / L, wherein the molar ratio of nickel, cobalt and manganese corresponds to the chemical formula of the final core-shell structure ternary precursor;

[0064] The complexing agent solution is 2 mol / L ammonia water; the precipitant solution is 2 mol / L sodium hydroxide solution;

[0065] The reaction was carried out under stirring conditions with a stirring speed of 350 r / min and a reaction temperature of 60°C. During the reaction, the pH value was maintained at 12.2 and the ammonia concentration was maintained at 15 g / L.

[0066] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to produce a core-shell structure ternary precursor with a particle size D50 of 12 μm;

[0067] The second salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, the total concentration of nickel, cobalt and manganese is 3 mol / L, and the molar ratio of nickel, cobalt and manganese is 1:1:1;

[0068] The complexing agent solution is 2 mol / L ammonia water; the precipitant solution is 2 mol / L sodium hydroxide solution;

[0069] The reaction was carried out under stirring conditions with a stirring speed of 250 r / min and a reaction temperature of 60°C. During the reaction, the pH value was maintained at 12.2 and the ammonia concentration was maintained at 15 g / L.

[0070] The chemical formula of the obtained core-shell structure ternary precursor is Ni 0.9 Co 0.05 Mn 0.05 (OH)2;

[0071] (3) uniformly mixing lithium hydroxide and the core-shell structure ternary precursor, sintering under an oxygen atmosphere to obtain the positive electrode material Ni 0.9 Co 0.05 Mn 0.05 O2; the sintering temperature is 750℃ and the time is 12h.

[0072] The EPMA diagram of the cross-section Ni element of the core-shell structure ternary precursor obtained in this example is shown in FIG1 , and the EPMA diagram of the cross-section Co element is shown in FIG2 .

[0073] Example 2

[0074] This embodiment provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0075] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles with a particle size D50 of 11 μm are obtained;

[0076] The first salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the total concentration of nickel, cobalt and manganese is 1 mol / L, wherein the molar ratio of nickel, cobalt and manganese corresponds to the chemical formula of the final core-shell structure ternary precursor;

[0077] The complexing agent solution is 1 mol / L ammonia water; the precipitant solution is 1 mol / L sodium hydroxide solution;

[0078] The reaction was carried out under stirring conditions at a stirring speed of 200 r / min and a reaction temperature of 35°C. During the reaction, the pH value was maintained at 12.5 and the ammonia concentration was maintained at 14 g / L.

[0079] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to produce a core-shell structure ternary precursor with a particle size D50 of 11.5 μm;

[0080] The second salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, the total concentration of nickel, cobalt and manganese is 1 mol / L, and the molar ratio of nickel, cobalt and manganese is 1:1:1;

[0081] The complexing agent solution is 1 mol / L ammonia water; the precipitant solution is 1 mol / L sodium hydroxide solution;

[0082] The reaction was carried out under stirring conditions at a stirring speed of 100 r / min and a reaction temperature of 35°C. During the reaction, the pH value was maintained at 12.5 and the ammonia concentration was maintained at 14 g / L.

[0083] The chemical formula of the obtained core-shell structure ternary precursor is Ni 0.9 Co 0.05 Mn 0.05 (OH)2;

[0084] (3) uniformly mixing lithium hydroxide and the core-shell structure ternary precursor, sintering under an oxygen atmosphere to obtain the positive electrode material Ni 0.9 Co 0.05 Mn 0.05 O2; the sintering temperature is 500℃ and the time is 20h.

[0085] Example 3

[0086] This embodiment provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0087] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles with a particle size D50 of 11 μm are obtained;

[0088] The first salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the total concentration of nickel, cobalt and manganese is 5 mol / L, wherein the molar ratio of nickel, cobalt and manganese corresponds to the chemical formula of the final core-shell structure ternary precursor;

[0089] The complexing agent solution is 3 mol / L ammonia water; the precipitant solution is 3 mol / L sodium hydroxide solution;

[0090] The reaction was carried out under stirring conditions at a stirring speed of 500 r / min and a reaction temperature of 70°C. During the reaction, the pH value was maintained at 12 and the ammonia concentration was maintained at 16 g / L.

[0091] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to produce a core-shell structure ternary precursor with a particle size D50 of 13 μm;

[0092] The second salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, the total concentration of nickel, cobalt and manganese is 5 mol / L, and the molar ratio of nickel, cobalt and manganese is 1:1:1;

[0093] The complexing agent solution is 1 mol / L ammonia water; the precipitant solution is 1 mol / L sodium hydroxide solution;

[0094] The reaction was carried out under stirring conditions at a stirring speed of 400 r / min and a reaction temperature of 70°C. During the reaction, the pH value was maintained at 12 and the ammonia concentration was maintained at 16 g / L.

[0095] The chemical formula of the obtained core-shell structure ternary precursor is Ni 0.9 Co0.05 Mn 0.05 (OH)2;

[0096] (3) uniformly mixing lithium hydroxide and the core-shell structure ternary precursor, sintering under an oxygen atmosphere to obtain the positive electrode material Ni 0.9 Co 0.05 Mn 0.05 O2; the sintering temperature is 1000℃ and the time is 6h.

[0097] Example 4

[0098] This embodiment provides a method for preparing a positive electrode material, wherein the particle size D50 of the core particles is 11 μm, the particle size D50 of the core-shell structure ternary precursor is 11.1 μm, and the composition of the first salt solution is adjusted so that the chemical formula of the core-shell structure ternary precursor is Ni 0.9 Co 0.05 Mn 0.05 Except for (OH)2, the rest are the same as in Example 1.

[0099] Example 5

[0100] This embodiment provides a method for preparing a positive electrode material, wherein the particle size D50 of the core particles is 11 μm, the particle size D50 of the core-shell structure ternary precursor is 13.5 μm, and the composition of the first salt solution is adjusted so that the chemical formula of the core-shell structure ternary precursor is Ni 0.9 Co 0.05 Mn 0.05 Except for (OH)2, the rest are the same as in Example 1.

[0101] Example 6

[0102] This embodiment provides a method for preparing a positive electrode material. In addition to the same composition of the first salt solution and the second salt solution, the particle size D50 of the core particles is 11 μm, the particle size D50 of the obtained ternary precursor is 12 μm, and the chemical formula of the finally obtained ternary precursor is Ni 0.9 Co 0.05 Mn 0.05 Except for (OH)2, the rest are the same as in Example 1.

[0103] In this embodiment, since the first salt solution and the second salt solution have the same composition, a ternary precursor with a core-shell structure cannot be obtained.

[0104] Example 7

[0105] This embodiment provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0106] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles with a particle size D50 of 2 μm are obtained;

[0107] The first salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the total concentration of nickel, cobalt and manganese is 3 mol / L, wherein the molar ratio of nickel, cobalt and manganese corresponds to the chemical formula of the final core-shell structure ternary precursor;

[0108] The complexing agent solution is 2 mol / L ammonia water; the precipitant solution is 2 mol / L sodium hydroxide solution;

[0109] The reaction was carried out under stirring conditions at a stirring speed of 350 r / min and a reaction temperature of 60°C. During the reaction, the pH value was maintained at 11.8 and the ammonia concentration was maintained at 12.5 g / L.

[0110] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to produce a core-shell structure ternary precursor with a particle size D50 of 3 μm;

[0111] The second salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, the total concentration of nickel, cobalt and manganese is 3 mol / L, and the molar ratio of nickel, cobalt and manganese is 5:2:3;

[0112] The complexing agent solution is 2 mol / L ammonia water; the precipitant solution is 2 mol / L sodium hydroxide solution;

[0113] The reaction was carried out under stirring conditions with a stirring speed of 250 r / min and a reaction temperature of 60°C. During the reaction, the pH value was maintained at 11.8 and the ammonia concentration was maintained at 12.5 g / L.

[0114] The chemical formula of the obtained core-shell structure ternary precursor is Ni 0.88 Co 0.05 Mn 0.07 (OH)2;

[0115] (3) uniformly mixing lithium hydroxide and the core-shell structure ternary precursor, sintering under an oxygen atmosphere to obtain the positive electrode material Ni 0.88 Co 0.05 Mn 0.07 O2; the sintering temperature is 750℃ and the time is 12h.

[0116] Example 8

[0117] This embodiment provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0118] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles with a particle size D50 of 2 μm are obtained;

[0119] The first salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the total concentration of nickel, cobalt and manganese is 1 mol / L, wherein the molar ratio of nickel, cobalt and manganese corresponds to the chemical formula of the final core-shell structure ternary precursor;

[0120] The complexing agent solution is 1 mol / L ammonia water; the precipitant solution is 1 mol / L sodium hydroxide solution;

[0121] The reaction was carried out under stirring conditions at a stirring speed of 200 r / min and a reaction temperature of 35°C. During the reaction, the pH value was maintained at 11.5 and the ammonia concentration was maintained at 12 g / L.

[0122] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to produce a core-shell structure ternary precursor with a particle size D50 of 2.5 μm;

[0123] The second salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, the total concentration of nickel, cobalt and manganese is 1 mol / L, and the molar ratio of nickel, cobalt and manganese is 5:2:3;

[0124] The complexing agent solution is 1 mol / L ammonia water; the precipitant solution is 1 mol / L sodium hydroxide solution;

[0125] The reaction was carried out under stirring conditions at a stirring speed of 100 r / min and a reaction temperature of 35°C. During the reaction, the pH value was maintained at 11.5 and the ammonia concentration was maintained at 12 g / L.

[0126] The chemical formula of the obtained core-shell structure ternary precursor is Ni 0.88 Co 0.05 Mn 0.07 (OH)2;

[0127] (3) uniformly mixing lithium hydroxide and the core-shell structure ternary precursor, sintering under an oxygen atmosphere to obtain the positive electrode material Ni 0.88 Co 0.05 Mn 0.07 O2; the sintering temperature is 500℃ and the time is 20h.

[0128] Example 9

[0129] This embodiment provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0130] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles with a particle size D50 of 2 μm are obtained;

[0131] The first salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the total concentration of nickel, cobalt and manganese is 5 mol / L, wherein the molar ratio of nickel, cobalt and manganese corresponds to the chemical formula of the final core-shell structure ternary precursor;

[0132] The complexing agent solution is 3 mol / L ammonia water; the precipitant solution is 3 mol / L sodium hydroxide solution;

[0133] The reaction was carried out under stirring conditions at a stirring speed of 500 r / min and a reaction temperature of 70°C. During the reaction, the pH value was maintained at 12 and the ammonia concentration was maintained at 13 g / L.

[0134] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to produce a core-shell structure ternary precursor with a particle size D50 of 4 μm;

[0135] The second salt solution is a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, the total concentration of nickel, cobalt and manganese is 5 mol / L, and the molar ratio of nickel, cobalt and manganese is 5:2:3;

[0136] The complexing agent solution is 1 mol / L ammonia water; the precipitant solution is 1 mol / L sodium hydroxide solution;

[0137] The reaction was carried out under stirring conditions at a stirring speed of 400 r / min and a reaction temperature of 70°C. During the reaction, the pH value was maintained at 12 and the ammonia concentration was maintained at 13 g / L.

[0138] The chemical formula of the obtained core-shell structure ternary precursor is Ni 0.88 Co 0.05 Mn 0.07 (OH)2;

[0139] (3) uniformly mixing lithium hydroxide and the core-shell structure ternary precursor, sintering under an oxygen atmosphere to obtain the positive electrode material Ni 0.88 Co 0.05 Mn 0.07 O2; the sintering temperature is 1000℃ and the time is 6h.

[0140] Example 10

[0141] This embodiment provides a method for preparing a positive electrode material, wherein the particle size D50 of the core particles is 2 μm, the particle size D50 of the core-shell structure ternary precursor is 2.1 μm, and the composition of the first salt solution is adjusted so that the chemical formula of the core-shell structure ternary precursor is Ni 0.88 Co 0.05 Mn 0.07 Except for (OH)2, the rest are the same as in Example 1.

[0142] Example 11

[0143] This embodiment provides a method for preparing a positive electrode material, wherein the particle size D50 of the core particle is 2 μm, the particle size D50 of the core-shell structure ternary precursor is 4.5 μm, and the composition of the first salt solution is adjusted so that the chemical formula of the core-shell structure ternary precursor is Ni 0.88 Co 0.05 Mn 0.07 Except for (OH)2, the rest are the same as in Example 1.

[0144] Example 12

[0145] This embodiment provides a method for preparing a positive electrode material. In addition to the same composition of the first salt solution and the second salt solution, the particle size D50 of the core particles is 2 μm, the particle size D50 of the obtained ternary precursor is 3 μm, and the chemical formula of the finally obtained ternary precursor is Ni 0.88 Co 0.05 Mn 0.07 Except for (OH)2, the rest are the same as in Example 1.

[0146] In this embodiment, since the first salt solution and the second salt solution have the same composition, a ternary precursor with a core-shell structure cannot be obtained.

[0147] Example 13

[0148] This embodiment provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0149] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles with a particle size D50 of 18 μm are obtained;

[0150] The first salt solution is a mixed solution of nickel sulfate and cobalt sulfate, with a total concentration of nickel and cobalt of 3 mol / L, wherein the molar ratio of nickel to cobalt corresponds to the chemical formula of the final core-shell structure ternary precursor;

[0151] The complexing agent solution is 2 mol / L ammonia water; the precipitant solution is 2 mol / L sodium hydroxide solution;

[0152] The reaction was carried out under stirring conditions at a stirring speed of 350 r / min and a reaction temperature of 60°C. During the reaction, the pH value was maintained at 11.8 and the ammonia concentration was maintained at 2.5 g / L.

[0153] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to produce a core-shell structure ternary precursor with a particle size D50 of 19 μm;

[0154] The second salt solution is a mixed solution of nickel sulfate and aluminum sulfate, the total concentration of nickel and aluminum is 3 mol / L, and the molar ratio of nickel to aluminum is 6:4;

[0155] The complexing agent solution is 2 mol / L ammonia water; the precipitant solution is 2 mol / L sodium hydroxide solution;

[0156] The reaction was carried out under stirring conditions with a stirring speed of 250 r / min and a reaction temperature of 60°C. During the reaction, the pH value was maintained at 11.8 and the ammonia concentration was maintained at 2.5 g / L.

[0157] The chemical formula of the obtained core-shell structure ternary precursor is Ni 0.75 Co 0.15 Al 0.1 (OH)2;

[0158] (3) uniformly mixing lithium hydroxide and the core-shell structure ternary precursor, sintering under an oxygen atmosphere to obtain the positive electrode material Ni 0.75 Co 0.15 Al 0.1 O2; the sintering temperature is 750℃ and the time is 12h.

[0159] Example 14

[0160] This embodiment provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0161] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles with a particle size D50 of 18 μm are obtained;

[0162] The first salt solution is a mixed solution of nickel sulfate and cobalt sulfate, wherein the total concentration of nickel, cobalt and manganese is 1 mol / L, wherein the molar ratio of nickel to cobalt corresponds to the chemical formula of the final core-shell structure ternary precursor;

[0163] The complexing agent solution is 1 mol / L ammonia water; the precipitant solution is 1 mol / L sodium hydroxide solution;

[0164] The reaction was carried out under stirring conditions at a stirring speed of 200 r / min and a reaction temperature of 35°C. During the reaction, the pH value was maintained at 11.5 and the ammonia concentration was maintained at 2 g / L.

[0165] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to produce a core-shell structure ternary precursor with a particle size D50 of 18.5 μm;

[0166] The second salt solution is a mixed solution of nickel sulfate and aluminum sulfate, the total concentration of nickel and aluminum is 1 mol / L, and the molar ratio of nickel to aluminum is 6:4;

[0167] The complexing agent solution is 1 mol / L ammonia water; the precipitant solution is 1 mol / L sodium hydroxide solution;

[0168] The reaction was carried out under stirring conditions at a stirring speed of 100 r / min and a reaction temperature of 35°C. During the reaction, the pH value was maintained at 11.5 and the ammonia concentration was maintained at 2 g / L.

[0169] The chemical formula of the obtained core-shell structure ternary precursor is Ni 0.75 Co 0.15 Al 0.1 (OH)2;

[0170] (3) uniformly mixing lithium hydroxide and the core-shell structure ternary precursor, sintering under an oxygen atmosphere to obtain the positive electrode material Ni 0.75 Co 0.15 Al 0.1 O2; the sintering temperature is 500℃ and the time is 20h.

[0171] Example 15

[0172] This embodiment provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0173] (1) mixing a first salt solution, a complexing agent solution, and a precipitant solution in a base solution and reacting until core particles with a particle size D50 of 18 μm are obtained;

[0174] The first salt solution is a mixed solution of nickel sulfate and cobalt sulfate, with a total concentration of nickel and cobalt of 5 mol / L, wherein the molar ratio of nickel to cobalt corresponds to the chemical formula of the final core-shell structure ternary precursor;

[0175] The complexing agent solution is 3 mol / L ammonia water; the precipitant solution is 3 mol / L sodium hydroxide solution;

[0176] The reaction was carried out under stirring conditions at a stirring speed of 500 r / min and a reaction temperature of 70°C. During the reaction, the pH value was maintained at 12 and the ammonia concentration was maintained at 3 g / L.

[0177] (2) continuing to mix the second salt solution, the complexing agent solution, and the precipitant solution to produce a core-shell structure ternary precursor with a particle size D50 of 20 μm;

[0178] The second salt solution is a mixed solution of nickel sulfate and aluminum sulfate, the total concentration of nickel and aluminum is 5 mol / L, and the molar ratio of nickel to aluminum is 6:4;

[0179] The complexing agent solution is 1 mol / L ammonia water; the precipitant solution is 1 mol / L sodium hydroxide solution;

[0180] The reaction was carried out under stirring conditions at a stirring speed of 400 r / min and a reaction temperature of 70°C. During the reaction, the pH value was maintained at 12 and the ammonia concentration was maintained at 3 g / L.

[0181] The chemical formula of the obtained core-shell structure ternary precursor is Ni 0.75 Co 0.15 Al 0.1 (OH)2;

[0182] (3) uniformly mixing lithium hydroxide and the core-shell structure ternary precursor, sintering under an oxygen atmosphere to obtain the positive electrode material Ni 0.75 Co 0.15 Al 0.1 O2; the sintering temperature is 1000℃ and the time is 6h.

[0183] Example 16

[0184] This embodiment provides a method for preparing a positive electrode material, wherein the particle size D50 of the core particle is 18 μm, the particle size D50 of the core-shell structure ternary precursor is 18.1 μm, and the composition of the first salt solution is adjusted so that the chemical formula of the core-shell structure ternary precursor is Ni 0.75 Co 0.15 Al 0.1 Except for (OH)2, the rest are the same as in Example 1.

[0185] Example 17

[0186] This embodiment provides a method for preparing a positive electrode material, wherein the particle size D50 of the core particle is 18 μm, the particle size D50 of the core-shell structure ternary precursor is 20.5 μm, and the composition of the first salt solution is adjusted so that the chemical formula of the core-shell structure ternary precursor is Ni 0.75 Co 0.15 Al 0.1 Except for (OH)2, the rest are the same as in Example 1.

[0187] Example 18

[0188] This embodiment provides a method for preparing a positive electrode material. In addition to the first salt solution and the second salt solution having the same composition, the particle size D50 of the core particles is 18 μm, the particle size D50 of the obtained ternary precursor is 19 μm, and the chemical formula of the finally obtained ternary precursor is Ni 0.75 Co 0.15 Al 0.1 Except for (OH)2, the rest are the same as in Example 1.

[0189] In this embodiment, since the first salt solution and the second salt solution have the same composition, a ternary precursor with a core-shell structure cannot be obtained.

[0190] Performance Characterization

[0191] The positive electrode material obtained in the above embodiment is prepared into a lithium ion battery by the following method:

[0192] The positive electrode material, binder polyvinylidene fluoride, and conductive agent Super P were added to N-methylpyrrolidone at a mass ratio of 97:1.5:1.5 and stirred to form a first positive electrode slurry; the first positive electrode slurry was then evenly coated on the positive electrode current collector aluminum foil, dried and roll-pressed to obtain a positive electrode sheet;

[0193] Graphite, conductive agent acetylene black, thickener CMC and binder SBR are mixed in a mass ratio of 96:1:1.5:1.5, and deionized water is added as a solvent and stirred thoroughly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained after drying, cold pressing and slitting;

[0194] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then fully dried lithium salt LiPF6 was dissolved in the mixed solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0195] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, then wrapped with aluminum-plastic film. After drying, the electrolyte is injected. After packaging, standing and formation processes, a lithium-ion battery is obtained. The separator is a PE porous film with a thickness of 11μm, an air permeability of 280s / 100mL, and a porosity of 40%.

[0196] The specific capacity, cycle capacity retention rate and rate performance of the obtained lithium-ion battery were tested, and the results are shown in Table 1.

[0197] The specific capacity test method is as follows: using the Blue Electric Battery Test System, at 25°C, the lithium-ion battery is charged and discharged three times in the voltage range of 2V to 4.3V at a charge and discharge rate of 0.04A / g (calculated based on the mass of the positive electrode material) to measure the battery specific capacity;

[0198] The test method for cycle capacity retention is: at 25 ° C, cycle at a charge and discharge rate of 0.19A / g (calculated based on the mass of the positive electrode material). After 500 cycles, the discharge capacity of the battery at this time is divided by the discharge capacity of the first cycle, which is the battery's 500-cycle capacity retention rate.

[0199] The test method for rate performance is as follows: at 25°C, charge and discharge three times in the voltage range of 2V to 4.3V at a charge and discharge rate of 0.04A / g (calculated based on the mass of the positive electrode material) to obtain the discharge capacity C0 of the last cycle; then, charge the battery to 4.3V at a charge rate of 0.04A / g (calculated based on the mass of the positive electrode material), and discharge the battery to 2V at a discharge rate of 0.12A / g (calculated based on the mass of the positive electrode material) to obtain the discharge capacity C2 of the last cycle; the ratio of C2 / C0 is the rate performance.

[0200] Table 1

[0201] In summary, the core-shell structure ternary precursor provided by this application provides high capacity for the corresponding positive electrode material by making the core have a high nickel content; the shell has a low nickel content, which makes it structurally stable. Combined with the thickness of the shell layer of this application, the sphericity of the ternary precursor particles can be guaranteed, and the phenomenon of core-shell separation can be avoided, so that the subsequent preparation of the positive electrode material has the advantages of spacing energy density and safety.

[0202] The above description is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art should understand that any changes or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application fall within the protection scope and disclosure scope of the present application.

Claims

1. A core-shell structure ternary precursor, wherein: The chemical formula of the core-shell structured ternary precursor is Ni x Co y M z (OH)2, where 0 < x < 1, 0 ≤ y < 1, 0 < z < 1, and x + y + z = 1, and M includes Mn and / or Al; The shell thickness of the core-shell structure ternary precursor is 0.1-2 μm.

2. The core-shell structure precursor according to claim 1, wherein The chemical formula of the core-shell structure ternary precursor is Ni x Co y M z (OH)2, where 0.75≤x≤0.9, 0.05≤y≤0.15, 0.05≤z≤0.

1.

3. The core-shell structure precursor according to claim 1 or 2, wherein: The core-shell structure ternary precursor comprises a core and a shell; The nickel content of the inner core is higher than that of the outer shell.

4. A method for preparing a core-shell structure ternary precursor according to any one of claims 1 to 3, comprising the following steps: (1) mixing a first salt solution, a complexing agent solution and a precipitant solution in a base solution and reacting until core particles of a target particle size are obtained; (2) continuing to mix the second salt solution, the complexing agent solution and the precipitant solution, and reacting to obtain a core-shell structure ternary precursor having a shell thickness that meets the requirements; The atomic mole percentage of nickel atoms in the first salt solution is higher than the atomic mole percentage of nickel atoms in the second salt solution.

5. The preparation method according to claim 4, wherein The target particle size of the core particles in step (1) is D50 reaching 2-18 μm.

6. The preparation method according to claim 4 or 5, wherein: The target particle size D50 of the core-shell structure ternary precursor in step (2) reaches 2.1-20 μm.

7. The preparation method according to any one of claims 4 to 6, wherein: The metal ions in the first salt solution include any one of Ni, Co, Mn or Al, or a combination of at least two of them.

8. The preparation method according to any one of claims 4 to 7, wherein: The total concentration of metal ions in the first salt solution is 1-5 mol / L.

9. The preparation method according to any one of claims 4 to 8, wherein: The metal ions in the second salt solution include any one or a combination of at least two of Ni, Co, Mn or Al; The total concentration of metal ions in the second salt solution is 1-5 mol / L.

10. The preparation method according to any one of claims 4 to 9, wherein: The complexing agent in the complexing agent solution includes any one of ammonia, citric acid, ethylenediaminetetraacetic acid, oxalic acid or sodium pyrophosphate, or a combination of at least two thereof; Preferably, the concentration of the complexing agent solution is 1-3 mol / L.

11. The preparation method according to any one of claims 4 to 10, wherein: The precipitant in the precipitant solution includes any one of sodium hydroxide, potassium hydroxide or sodium carbonate or a combination of at least two thereof; Preferably, the OH in the precipitant solution - The concentration is 1-3 mol / L.

12. The preparation method according to any one of claims 4 to 11, wherein: The reaction temperature in step (1) is 35-70°C; Preferably, the reaction in step (1) is carried out under stirring conditions, and the stirring speed is 200-500r / min; Preferably, during the reaction in step (1), the pH value is maintained at 8-13; Preferably, during the reaction process of step (1), the concentration of the complexing agent is maintained at 1-20 g / L.

13. The preparation method according to any one of claims 4 to 12, wherein: The reaction temperature in step (2) is 35-70°C; Preferably, the reaction in step (2) is carried out under stirring conditions, and the stirring speed is 100-400r / min; Preferably, during the reaction in step (2), the pH value is maintained at 8-13; Preferably, during the reaction process of step (2), the concentration of the complexing agent is maintained at 1-20 g / L.

14. A positive electrode material, wherein: The positive electrode material is prepared from the core-shell structure ternary precursor according to any one of claims 1 to 3.

15. A method for preparing the positive electrode material as claimed in claim 14, comprising: The lithium source and the core-shell structure ternary precursor are uniformly mixed and sintered in an oxygen atmosphere to obtain the positive electrode material.

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