Modified high-nickel precursor, preparation method thereof and positive electrode material

Abstract

The invention provides a modified high-nickel precursor, a preparation method thereof and a positive electrode material, and the preparation method comprises the following steps: under a protective atmosphere condition, a precipitant solution, a modified complexing agent solution and a metal salt solution are mixed in a base solution in a parallel flow manner, a co-precipitation reaction is performed to reach a target particle size, and washing and drying are performed to obtain the modified high-nickel precursor, solutes in the modified complexing agent solution comprise a complexing agent and a modifier; the modifier is ammonium lignosulfonate. According to the method, the anionic surfactant can be generated in the coprecipitation reaction process by using the modified complexing agent solution containing the modifier, so that the particle dispersity is remarkably improved, and the particle sphericity is improved; meanwhile, the lattice constant of the precursor can be expanded, and the diffusion kinetics of lithium ions in the corresponding positive electrode material is improved, so that the charge-discharge capacity, the rate capability and the cycling stability of the positive electrode material are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries and relates to a high-nickel precursor, in particular to a modified high-nickel precursor and a preparation method thereof and a positive electrode material. Background Art

[0002] High energy density lithium-ion batteries are widely used in storage fields such as portable electronic devices, electric vehicles and smart grids. As the core component of lithium-ion batteries, the performance of cathode materials directly affects the energy density, cycle stability and safety performance of lithium-ion batteries. In recent years, layered oxide cathode materials with high nickel content have become an ideal choice for high energy density lithium-ion batteries because of their high theoretical capacity and cost-effectiveness.

[0003] However, high-nickel layered oxide cathode materials face problems of poor structural stability and electrolyte compatibility during the charge and discharge process, which usually lead to rapid attenuation of battery capacity and shortened life. These technical problems can be solved to a certain extent through ion doping, surface coating and lattice parameter optimization. Among them, lattice parameter optimization improves the performance of high-nickel layered oxide cathode materials by improving the diffusion capacity of lithium ions.

[0004] To this end, it is necessary to provide a modified high-nickel precursor with good dispersibility, high sphericity and good crystallinity, a preparation method thereof and a positive electrode material. Summary of the invention

[0005] The object of the present invention is to provide a modified high-nickel precursor and a preparation method thereof and a positive electrode material. The preparation method can significantly improve the particle dispersibility of the modified high-nickel precursor, improve the particle sphericity, and also expand the precursor lattice constant; thereby improving the diffusion kinetics of lithium ions in the corresponding positive electrode material, thereby improving the charge and discharge capacity, rate performance and cycle stability of the positive electrode material.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a modified high-nickel precursor, the preparation method comprising the following steps:

[0008] Under protective atmosphere conditions, a precipitant solution, a modified complexing agent solution and a metal salt solution are mixed in parallel in a base liquid, and a co-precipitation reaction is performed to a target particle size, and the modified high-nickel precursor is obtained after washing and drying;

[0009] The solute in the modified complexing agent solution includes a complexing agent and a modifier;

[0010] The modifier is ammonium lignin sulfonate.

[0011] The present invention uses a modified complexing agent solution containing a modifier to generate anionic surfactants during a coprecipitation reaction, thereby significantly improving particle dispersibility and particle sphericity, and can also expand the precursor lattice constant, improve the diffusion dynamics of lithium ions in the corresponding positive electrode material, thereby improving the charge and discharge capacity, rate performance and cycle stability of the positive electrode material; moreover, when the ammonium lignin sulfonate reacts with the precipitant, it can slowly release ammonia water, reduce the growth rate of the precursor particles, thereby reducing pores and defects, and can also suppress the fluctuation of ammonia water concentration, which is helpful to improve the crystallinity of the hydroxide precursor and improve the quality of the modified high-nickel precursor.

[0012] Preferably, the concentration of the modifying agent in the modified complexing agent solution is 0.05 mol / L to 0.5 mol / L, preferably 0.15 mol / L to 0.35 mol / L.

[0013] Preferably, the complexing agent in the modified complexing agent solution includes any one of ammonium nitrate, ammonium sulfate, ammonium hydrogen sulfate or ammonium chloride, or a combination of at least two of them.

[0014] Preferably, the complexing agent concentration in the modified complexing agent solution is 0.2 mol / L to 2 mol / L, preferably 0.8 mol / L to 1.2 mol / L.

[0015] Preferably, the ammonia concentration during the coprecipitation reaction is 1 g / L to 8 g / L, preferably 3 g / L to 5 g / L.

[0016] Preferably, the temperature during the coprecipitation reaction is 40°C to 70°C.

[0017] Preferably, the coprecipitation reaction comprises a nucleation stage and a growth stage performed sequentially.

[0018] Preferably, the pH value of the nucleation stage is 11.4 to 12.8, preferably 11.8 to 12.3.

[0019] Preferably, the pH value during the growth stage is from 9.6 to 10.8, preferably from 10.0 to 10.4.

[0020] Preferably, the target particle size refers to a median particle size D50 of 3 μm to 15 μm, preferably 6 μm to 10 μm.

[0021] Preferably, the total concentration of metal ions in the metal salt solution is 1 mol / L to 3 mol / L.

[0022] Preferably, the concentration of the precipitant solution is 20 wt % to 40 wt %.

[0023] Preferably, the pH value of the base solution is 11.5 to 12.8.

[0024] Preferably, the ammonia concentration of the base solution is 0.5 g / L to 4 g / L.

[0025] Preferably, the concentration of the modifier in the base solution is 0.1 mol / L to 0.3 mol / L.

[0026] In a second aspect, the present invention provides a modified high-nickel precursor, wherein the modified high-nickel precursor is prepared by the preparation method described in the first aspect;

[0027] The chemical formula of the modified high nickel precursor is Ni x Co y Mn 1-x-y (OH)2 or Ni x Co y Al 1-x-y (OH)2 wherein 0.6≤x<1, 0≤y≤0.2.

[0028] In a third aspect, the present invention provides a positive electrode material, which is prepared from the modified high-nickel precursor described in the second aspect.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention uses a modified complexing agent solution containing a modifier to generate anionic surfactants during a coprecipitation reaction, thereby significantly improving particle dispersibility and particle sphericity, and can also expand the precursor lattice constant, improve the diffusion dynamics of lithium ions in the corresponding positive electrode material, thereby improving the charge and discharge capacity, rate performance and cycle stability of the positive electrode material; moreover, when the ammonium lignin sulfonate reacts with the precipitant, it can slowly release ammonia water, reduce the growth rate of the precursor particles, thereby reducing pores and defects, and can also suppress the fluctuation of ammonia water concentration, which is helpful to improve the crystallinity of the hydroxide precursor and improve the quality of the modified high-nickel precursor. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a SEM (Scanning Electron Microscope) image of the modified high-nickel precursor obtained in Example 1 of the present invention;

[0032] Figure 2 This is a SEM image of the high-nickel precursor obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0034] A certain embodiment of the present invention provides a method for preparing a modified high-nickel precursor, the preparation method comprising the following steps:

[0035] Under protective atmosphere conditions, a precipitant solution, a modified complexing agent solution and a metal salt solution are mixed in parallel in a base liquid, and a co-precipitation reaction is performed to a target particle size, and the modified high-nickel precursor is obtained after washing and drying;

[0036] The solute in the modified complexing agent solution includes a complexing agent and a modifier;

[0037] The modifier is ammonium lignin sulfonate.

[0038] The present invention uses a modified complexing agent solution containing a modifier to generate anionic surfactants during a coprecipitation reaction, thereby significantly improving particle dispersibility and particle sphericity, and can also expand the precursor lattice constant, improve the diffusion dynamics of lithium ions in the corresponding positive electrode material, thereby improving the charge and discharge capacity, rate performance and cycle stability of the positive electrode material; moreover, when the ammonium lignin sulfonate reacts with the precipitant, it can slowly release ammonia water, reduce the growth rate of the precursor particles, thereby reducing pores and defects, and can also suppress the fluctuation of ammonia water concentration, which is helpful to improve the crystallinity of the hydroxide precursor and improve the quality of the modified high-nickel precursor.

[0039] In some embodiments, the protective atmosphere includes nitrogen and / or argon.

[0040] In certain embodiments, the solute composition in the metal salt solution meets the chemical formula requirements of the final modified high-nickel precursor. In the present invention, the chemical formula of the modified high-nickel precursor is Ni x Co y Mn 1-x-y (OH)2 or Ni x Co y Al 1-x-y Any one of (OH)2, wherein 0.6≤x<1, 0≤y≤0.2.

[0041] In certain embodiments, the solute in the metal salt solution includes any one of sulfate, nitrate or halide, or a combination of at least two of them. Typical but non-limiting combinations include a combination of sulfate and nitrate, a combination of nitrate and halide, a combination of sulfate and halide, and a combination of sulfate, nitrate and halide.

[0042] Taking Ni ions as an example, the solute of Ni in the modified high-nickel precursor includes any one of nickel sulfate, nickel nitrate or nickel chloride, or a combination of at least two of them. Typical but non-limiting combinations include a combination of nickel sulfate and nickel nitrate, a combination of nickel nitrate and nickel chloride, a combination of nickel sulfate and nickel chloride, or a combination of nickel sulfate, nickel nitrate and nickel chloride.

[0043] Taking Co ions as an example, the solute of Co in the modified high-nickel precursor includes any one of cobalt sulfate, cobalt nitrate or cobalt chloride, or a combination of at least two of them. Typical but non-limiting combinations include a combination of cobalt sulfate and cobalt nitrate, a combination of cobalt nitrate and cobalt chloride, a combination of cobalt sulfate and cobalt chloride, or a combination of cobalt sulfate, cobalt nitrate and cobalt chloride.

[0044] Taking Mn ions as an example, the solute for Mn in the modified high-nickel precursor includes any one of manganese sulfate, manganese nitrate or manganese chloride, or a combination of at least two of them. Typical but non-limiting combinations include a combination of manganese sulfate and manganese nitrate, a combination of manganese nitrate and manganese chloride, a combination of manganese sulfate and manganese chloride, or a combination of manganese sulfate, manganese nitrate and manganese chloride.

[0045] Taking Al ions as an example, the solute for Al in the modified high-nickel precursor includes any one of aluminum sulfate, aluminum nitrate or aluminum chloride, or a combination of at least two of them. Typical but non-limiting combinations include a combination of aluminum sulfate and aluminum nitrate, a combination of aluminum nitrate and aluminum chloride, a combination of aluminum sulfate and aluminum chloride, or a combination of aluminum sulfate, aluminum nitrate and aluminum chloride.

[0046] In certain embodiments, the concentration of the modifier in the modified complexing agent solution is 0.05 mol / L to 0.5 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable, preferably 0.15 mol / L to 0.35 mol / L.

[0047] In certain embodiments, the complexing agent in the modified complexing agent solution includes any one of ammonium nitrate, ammonium sulfate, ammonium bisulfate or ammonium chloride, or a combination of at least two of them. Typical but non-limiting combinations include a combination of ammonium nitrate and ammonium sulfate, a combination of ammonium sulfate and ammonium bisulfate, a combination of ammonium bisulfate and ammonium chloride, a combination of ammonium nitrate, ammonium sulfate and ammonium bisulfate, a combination of ammonium sulfate, ammonium bisulfate and ammonium chloride, or a combination of ammonium nitrate, ammonium sulfate, ammonium bisulfate and ammonium chloride.

[0048] In certain embodiments, the complexing agent concentration in the modified complexing agent solution is 0.2 mol / L to 2 mol / L, for example, it can be 0.2 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L or 2 mol / L, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable, preferably 0.8 mol / L to 1.2 mol / L.

[0049] In certain embodiments, the ammonia concentration during the coprecipitation reaction is 1 g / L to 8 g / L, for example, 1 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L or 8 g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 3 g / L to 5 g / L.

[0050] In some embodiments, the temperature of the coprecipitation reaction is 40°C to 70°C, for example, 40°C, 50°C, 60°C or 70°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] In certain embodiments, the co-precipitation reaction comprises a nucleation phase and a growth phase performed sequentially.

[0052] In certain embodiments, the pH value of the nucleation stage is 11.4 to 12.8, for example, it can be 11.4, 11.5, 11.8, 12, 12.3 or 12.8, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 11.8 to 12.3.

[0053] In some embodiments, the pH value of the growth stage is 9.6 to 10.8, for example, it can be 9.6, 10.0, 10.2, 10.4 or 10.8, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 10.0 to 10.4.

[0054] In certain embodiments, the target particle size refers to a median particle size D50 of 3 μm to 15 μm, for example, 3 μm, 6 μm, 8 μm, 10 μm, 12 μm or 15 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 6 μm to 10 μm.

[0055] In some embodiments, the total concentration of metal ions in the metal salt solution is 1 mol / L to 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 unlisted values ​​within the numerical range are also applicable.

[0056] In certain embodiments, the concentration of the precipitant solution is 20 wt % to 40 wt %, for example, 20 wt %, 25 wt %, 30 wt %, 35 wt % or 40 wt %, but is not limited to the listed values, and the rest of the values ​​not listed within the range are also applicable.

[0057] In certain embodiments, the precipitant in the precipitant solution includes any one of sodium hydroxide, potassium hydroxide or lithium hydroxide, or a combination of at least two of them. Typical but non-limiting combinations include a combination of sodium hydroxide and potassium hydroxide, a combination of potassium hydroxide and lithium hydroxide, a combination of sodium hydroxide and lithium hydroxide, or a combination of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0058] The base liquid of the present invention is prepared by adding a precipitant, a complexing agent and a modifier into water.

[0059] In some embodiments, the pH value of the base solution is 11.5 to 12.8, for example, it can be 11.5, 11.8, 12, 12.5 or 12.8, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0060] In some embodiments, the ammonia concentration of the base liquid is 0.5 g / L to 4 g / L, for example, it can be 0.5 g / L, 1 g / L, 2 g / L, 3 g / L or 4 g / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0061] In some embodiments, the concentration of the modifier in the base solution is 0.1 mol / L to 0.3 mol / L, for example, 0.1 mol / L, 0.2 mol / L or 0.3 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0062] In certain embodiments, the coprecipitation reaction is accompanied by stirring at a stirring speed of 250 rpm to 350 rpm, for example, 250 rpm, 280 rpm, 300 rpm, 320 rpm or 350 rpm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0063] A certain embodiment of the present invention provides a modified high-nickel precursor, wherein the modified high-nickel precursor is prepared by the preparation method described in any embodiment;

[0064] The chemical formula of the modified high nickel precursor is Ni x Co y Mn 1-x-y (OH)2 or Ni x Co y Al 1-x-yAny one of (OH)2, wherein 0.6≤x<1, 0≤y≤0.2.

[0065] A certain embodiment of the present invention provides a positive electrode material, which is prepared from the modified high-nickel precursor described in any embodiment.

[0066] Exemplarily, the modified high-nickel precursor is mixed with a lithium source and then calcined to obtain the positive electrode material, wherein the lithium source includes but is not limited to lithium hydroxide and / or lithium carbonate.

[0067] The chemical formula of the modified high nickel precursor in the following examples and comparative examples is Ni 0.84 Co 0.11 Mn 0.05 (OH)2, the description of the modified high-nickel precursor is only for the purpose of clearly illustrating the technical solution of the present invention and is not regarded as a further limitation of the technical solution of the present invention.

[0068] Example 1

[0069] This embodiment provides a modified high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0070] (1) preparing a base solution using sodium hydroxide, ammonium sulfate and ammonium lignin sulfonate;

[0071] The pH value of the base solution was 12, the ammonia concentration was 2 g / L, and the concentration of ammonium lignin sulfonate was 0.2 mol / L;

[0072] (2) In a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (30 wt % sodium hydroxide solution), a modified complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the modified high-nickel precursor;

[0073] The complexing agent in the modified complexing agent solution is ammonium sulfate, and the modifier is ammonium lignin sulfonate; wherein the complexing agent concentration in the modified complexing agent solution is 1 mol / L, and the modifier concentration is 0.25 mol / L;

[0074] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0075] The ammonia concentration during the coprecipitation reaction is 4 g / L and the temperature is 55° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 12, and the pH value of the growth stage is 10.2.

[0076] The SEM image of the modified high nickel precursor obtained in this example is as follows: Figure 1 As shown, since this embodiment introduces ammonium lignin sulfonate as a modifier and combines it with the use of ammonium salt, the dispersibility, sphericity and crystallinity of the modified high-nickel precursor can be significantly improved, and the lattice parameters can be expanded, which helps to improve the diffusion kinetics of lithium ions in the positive electrode material, thereby improving the electrochemical performance of the positive electrode material.

[0077] Example 2

[0078] This embodiment provides a modified high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0079] (1) preparing a base solution using sodium hydroxide, ammonium sulfate and ammonium lignin sulfonate;

[0080] The pH value of the base solution was 12, the ammonia concentration was 1 g / L, and the concentration of ammonium lignin sulfonate was 0.2 mol / L;

[0081] (2) In a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (25 wt % sodium hydroxide solution), a modified complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the modified high-nickel precursor;

[0082] The complexing agent in the modified complexing agent solution is ammonium sulfate, and the modifier is ammonium lignin sulfonate; wherein the complexing agent concentration in the modified complexing agent solution is 0.8 mol / L, and the modifier concentration is 0.15 mol / L;

[0083] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0084] The ammonia concentration during the coprecipitation reaction is 3 g / L and the temperature is 50° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 11.8, and the pH value of the growth stage is 10.0.

[0085] Example 3

[0086] This embodiment provides a modified high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0087] (1) preparing a base solution using sodium hydroxide, ammonium sulfate and ammonium lignin sulfonate;

[0088] The pH value of the base solution was 12, the ammonia concentration was 3 g / L, and the concentration of ammonium lignin sulfonate was 0.2 mol / L;

[0089] (2) In a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (35 wt % sodium hydroxide solution), a modified complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the modified high-nickel precursor;

[0090] The complexing agent in the modified complexing agent solution is ammonium sulfate, and the modifier is ammonium lignin sulfonate; wherein the complexing agent concentration in the modified complexing agent solution is 1.2 mol / L, and the modifier concentration is 0.35 mol / L;

[0091] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0092] The ammonia concentration during the coprecipitation reaction is 5 g / L and the temperature is 60° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 12.3, and the pH value of the growth stage is 10.4.

[0093] Example 4

[0094] This embodiment provides a modified high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0095] (1) preparing a base solution using sodium hydroxide, ammonium sulfate and ammonium lignin sulfonate;

[0096] The pH value of the base solution was 11.5, the ammonia concentration was 0.5 g / L, and the concentration of ammonium lignin sulfonate was 0.1 mol / L;

[0097] (2) In a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (20 wt % sodium hydroxide solution), a modified complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the modified high-nickel precursor;

[0098] The complexing agent in the modified complexing agent solution is ammonium sulfate, and the modifier is ammonium lignin sulfonate; wherein the complexing agent concentration in the modified complexing agent solution is 0.2 mol / L, and the modifier concentration is 0.05 mol / L;

[0099] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 1 mol / L;

[0100] The ammonia concentration during the coprecipitation reaction is 1 g / L and the temperature is 40° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 11.4, and the pH value of the growth stage is 9.6.

[0101] Example 5

[0102] This embodiment provides a modified high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0103] (1) preparing a base solution using sodium hydroxide, ammonium sulfate and ammonium lignin sulfonate;

[0104] The pH value of the base solution was 12.8, the ammonia concentration was 4 g / L, and the concentration of ammonium lignin sulfonate was 0.3 mol / L;

[0105] (2) In a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (40 wt % sodium hydroxide solution), a modified complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the modified high-nickel precursor;

[0106] The complexing agent in the modified complexing agent solution is ammonium sulfate, and the modifier is ammonium lignin sulfonate; wherein the complexing agent concentration in the modified complexing agent solution is 2 mol / L, and the modifier concentration is 0.5 mol / L;

[0107] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 3 mol / L;

[0108] The ammonia concentration during the coprecipitation reaction is 8 g / L and the temperature is 70° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 12.8, and the pH value of the growth stage is 10.8.

[0109] Example 6

[0110] This embodiment provides a modified high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 The preparation method of (OH)2 is the same as that of Example 1 except that the target particle size D50 of the coprecipitation reaction is 6 μm.

[0111] Example 7

[0112] This embodiment provides a modified high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 The preparation method of (OH)2 is the same as that of Example 1 except that the target particle size D50 of the coprecipitation reaction is 10 μm.

[0113] Example 8

[0114] This embodiment provides a modified high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 The preparation method of (OH)2 is the same as that of Example 1 except that the target particle size D50 of the coprecipitation reaction is 3 μm.

[0115] Example 9

[0116] This embodiment provides a modified high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 The preparation method of (OH)2 is the same as that of Example 1 except that the target particle size D50 of the coprecipitation reaction is 15 μm.

[0117] Comparative Example 1

[0118] This comparative example provides a high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0119] (1) Prepare a base solution using sodium hydroxide and ammonium sulfate;

[0120] The pH value of the base solution was 12, and the ammonia concentration was 2 g / L;

[0121] (2) in a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (30 wt % sodium hydroxide solution), a complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the high-nickel precursor;

[0122] The complexing agent in the complexing agent solution is ammonium sulfate, and the concentration of the complexing agent is 1 mol / L;

[0123] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0124] The ammonia concentration during the coprecipitation reaction is 4 g / L and the temperature is 55° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 12, and the pH value of the growth stage is 10.2.

[0125] The SEM image of the high nickel precursor obtained in this comparative example is as follows Figure 2 As shown by Figure 1 and Figure 2 From the comparison, it can be seen that the use of ammonium lignin sulfonate as a modifier in combination with ammonium salt can significantly improve the dispersibility, sphericity and crystallinity of the modified high-nickel precursor, and expand the lattice parameters, which is helpful to improve the diffusion kinetics of lithium ions in the positive electrode material, thereby improving the electrochemical performance of the positive electrode material.

[0126] Comparative Example 2

[0127] This comparative example provides a high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0128] (1) Prepare a base solution using sodium hydroxide and ammonium sulfate;

[0129] The pH value of the base solution was 12, and the ammonia concentration was 2 g / L;

[0130] (2) in a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (30 wt % sodium hydroxide solution), a modified complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the high-nickel precursor;

[0131] The complexing agent in the modified complexing agent solution is ammonium sulfate, and the modifier is ammonium lignin sulfonate; wherein the complexing agent concentration in the modified complexing agent solution is 1 mol / L, and the modifier concentration is 0.25 mol / L;

[0132] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0133] The ammonia concentration during the coprecipitation reaction is 4 g / L and the temperature is 55° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 12, and the pH value of the growth stage is 10.2.

[0134] Comparative Example 3

[0135] This comparative example provides a high nickel precursor Ni 0.84 Co 0.11 Mn0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0136] (1) preparing a base solution using sodium hydroxide, ammonium sulfate and ammonium lignin sulfonate;

[0137] The pH value of the base solution was 12, the ammonia concentration was 2 g / L, and the concentration of ammonium lignin sulfonate was 0.2 mol / L;

[0138] (2) in a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (30 wt % sodium hydroxide solution), a complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the high-nickel precursor;

[0139] The complexing agent in the complexing agent solution is ammonium sulfate with a concentration of 1 mol / L;

[0140] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0141] The ammonia concentration during the coprecipitation reaction is 4 g / L and the temperature is 55° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 12, and the pH value of the growth stage is 10.2.

[0142] Comparative Example 4

[0143] This comparative example provides a high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0144] (1) Prepare the base solution using sodium hydroxide and ammonia water;

[0145] The pH value of the base solution was 12, and the ammonia concentration was 2 g / L;

[0146] (2) in a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (30 wt % sodium hydroxide solution), a complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the high-nickel precursor;

[0147] The complexing agent in the complexing agent solution is ammonia water with a concentration of 1 mol / L;

[0148] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0149] The ammonia concentration during the coprecipitation reaction is 4 g / L and the temperature is 55° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 12, and the pH value of the growth stage is 10.2.

[0150] Comparative Example 5

[0151] This comparative example provides a high nickel precursor Ni 0.84 Co 0.11 Mn 0.05 (OH)2 preparation method, the preparation method comprising the following steps:

[0152] (1) Use sodium hydroxide to prepare the base solution;

[0153] The pH value of the base solution is 12;

[0154] (2) in a nitrogen atmosphere, under stirring conditions of 300 rpm, a precipitant solution (30 wt % sodium hydroxide solution), a complexing agent solution and a metal salt solution are mixed in parallel in the base liquid, and a co-precipitation reaction is performed to a target particle size (D50 is 8 μm), followed by alkali washing, water washing and drying at 100° C. for 12 h to obtain the high-nickel precursor;

[0155] The complexing agent in the complexing agent solution is ammonia water with a concentration of 1 mol / L;

[0156] The metal salt in the metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of nickel, cobalt and manganese is 2 mol / L;

[0157] The ammonia concentration during the coprecipitation reaction is 4 g / L and the temperature is 55° C. The coprecipitation reaction includes a nucleation stage and a growth stage which are performed in sequence. The pH value of the nucleation stage is 12, and the pH value of the growth stage is 10.2.

[0158] Performance Characterization

[0159] The sphericity, specific surface area, tap density and lattice constant of the precursors obtained in the above examples and comparative examples were measured, and the results are shown in Table 1.

[0160] The sphericity is measured by image analysis, and its value is the ratio of the equivalent diameter to the maximum diameter; the lattice constant c / a ratio is calculated after refining the XRD spectrum.

[0161] Table 1

[0162]

[0163]

[0164] As can be seen from Table 1, the preparation method provided by the present application can improve the tap density and lattice constant (c / a ratio) of the obtained modified high-nickel precursor, and the sphericity is relatively high; specifically, the sphericity can be made above 0.896 and the tap density can be made above 1.614 g / cm 3 As a preferred technical solution of the present invention, the sphericity can be above 0.948 and the tap density can be above 1.832 g / cm 3 The above, while making the lattice constant above 1.551.

[0165] From the comparison between Comparative Example 1 and Example 1, it can be seen that when no modifier is added to the base liquid and the complexing agent, the sphericity of the obtained precursor is significantly reduced, and not only the specific surface area is increased from 12.25 m 2 / g decreased to 10.85m 2 / g, and the tap density is also from 1.907g / cm 3 Reduced to 1.723g / cm 3 At the same time, the lattice constant is reduced from 1.578 to 1.463; from the comparison of Comparative Examples 2 and 3 with Example 1, it can be seen that when no modifier is added to the base liquid or the complexing agent, the specific surface area, tap density, sphericity and lattice constant also show a significant decrease, which also shows that the present invention can improve the dispersibility and sphericity of the precursor and also expand the lattice constant of the precursor by using the modifier.

[0166] From the comparison between Comparative Example 4 and Example 1, it can be seen that the use of ammonia water as a complexing agent will cause a large fluctuation in the ammonia concentration during the preparation process, thereby causing a decrease in sphericity, dispersion and tap density, and at the same time, the lattice constant is significantly reduced compared to when the modifier is used. Comparative Example 5 is based on Comparative Example 4, but ammonia water is not added to the base liquid, resulting in a reduction in free ammonia during the nucleation period, uncontrolled particle size, and further reductions in sphericity, tap density and lattice constant.

[0167] The precursors obtained in the above examples and comparative examples were used to prepare positive electrode materials, and the electrochemical performance was tested:

[0168] Li2CO3 and the precursor are uniformly mixed by a high-speed mixer and sintered in an air atmosphere at a temperature of 800°C for 12 hours to obtain a positive electrode material; the theoretical molar ratio of lithium in Li2CO3 to the precursor is 1.03:1, and the ignition loss is supplemented according to the loss caused by sintering.

[0169] The positive electrode material, the binder polyvinylidene fluoride and the conductive agent Super P are 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 is then evenly coated on the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained after drying and rolling;

[0170] 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 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;

[0171] Ethylene carbonate EC, ethyl methyl carbonate EMC, and diethyl carbonate DEC are mixed in a volume ratio of 1:1:1, and then fully dried lithium salt LiPF6 is dissolved in the mixed solvent to prepare an electrolyte with a concentration of 1 mol / L;

[0172] The positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence, then wrapped with an aluminum-plastic film, and injected with an electrolyte after drying. After packaging, standing and forming, a lithium-ion battery is obtained; the separator is a PE porous film with a thickness of 11 μm, an air permeability of 280 s / 100 mL, and a porosity of 40%.

[0173] The initial specific capacity, cycle capacity retention rate and rate performance of the obtained lithium-ion battery were tested. The electrochemical performance test was carried out at room temperature in the voltage range of 2.8-4.3V. After 3 cycles of activation at a rate of 0.1C, the battery was cycled for 100 cycles at 1C. The results are shown in Table 2.

[0174] Table 2

[0175]

[0176]

[0177] It can be seen from Table 2 that the preparation method provided in the present application can improve the initial discharge specific capacity of the obtained positive electrode material to more than 193.2 mAh / g, and the 100-cycle capacity retention rate to more than 92.1%; as the preferred technical scheme of the present invention, the initial discharge specific capacity can be made above 194.9 mAh / g, and the 100-cycle capacity retention rate can be made above 93.3%; this shows that the preparation method provided by the present invention improves the diffusion kinetics of lithium ions in the positive electrode material through the use of a modifier, thereby improving the charge and discharge capacity and cycle stability of the positive electrode material.

[0178] From the comparison between Comparative Example 1 and Example 1, it can be seen that when no modifier is added to the base solution and the complexing agent, the initial discharge specific capacity of the positive electrode material corresponding to the obtained precursor is reduced from 196.8 mAh / g to 187.9 mAh / g, and the cycle stability is significantly reduced; from the comparison between Comparative Example 2 and Comparative Example 3 and Example 1, it can be seen that when no modifier is added to the base solution or the complexing agent, the initial discharge specific capacity and the cycle stability are also significantly reduced.

[0179] From the comparison between Comparative Example 4 and Example 1, it can be seen that the precursor obtained by using ammonia water as a complexing agent has significantly lower sphericity, dispersity, tap density and lattice constant than Example 1, and the electrochemical performance of the corresponding positive electrode material is significantly reduced; Comparative Example 5 is based on Comparative Example 4, but ammonia water is not added to the base liquid, and the electrochemical performance of the positive electrode material corresponding to the obtained precursor is also significantly reduced. This also shows that the present invention improves the dispersibility, sphericity and lattice constant of the precursor through the use of a modifier, thereby improving the diffusion kinetics of lithium ions in the positive electrode material, thereby improving the charge and discharge capacity and cycle stability of the positive electrode material.

[0180] In summary, the present invention can produce anionic surfactants during the coprecipitation reaction by using a modified complexing agent solution containing a modifier, thereby significantly improving the particle dispersibility and particle sphericity, and can also expand the precursor lattice constant, improve the diffusion kinetics of lithium ions in its corresponding positive electrode material, thereby improving the charge and discharge capacity, rate performance and cycle stability of the positive electrode material; moreover, when ammonium lignin sulfonate reacts with the precipitant, it can slowly release ammonia water, reduce the growth rate of the precursor particles, thereby reducing pores and defects, and can also suppress the fluctuation of ammonia water concentration, which helps to improve the crystallinity of the hydroxide precursor and improve the quality of the modified high-nickel precursor.

[0181] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a modified high-nickel precursor, characterized in that: The preparation method comprises the following steps: Under protective atmosphere conditions, a precipitant solution, a modified complexing agent solution and a metal salt solution are mixed in parallel in a base liquid, and a co-precipitation reaction is performed to a target particle size, and the modified high-nickel precursor is obtained after washing and drying; The solute in the modified complexing agent solution includes a complexing agent and a modifier; The modifier is ammonium lignin sulfonate.

2. The preparation method according to claim 1, characterized in that: The concentration of the modified complexing agent in the modified complexing agent solution is 0.05 mol / L to 0.5 mol / L, preferably 0.15 mol / L to 0.35 mol / L.

3. The preparation method according to claim 1, characterized in that: The complexing agent in the modified complexing agent solution includes any one of ammonium nitrate, ammonium sulfate, ammonium bisulfate or ammonium chloride, or a combination of at least two thereof; Preferably, the complexing agent concentration in the modified complexing agent solution is 0.2 mol / L to 2 mol / L, preferably 0.8 mol / L to 1.2 mol / L.

4. The preparation method according to claim 1, characterized in that: The ammonia concentration during the coprecipitation reaction is 1 g / L to 8 g / L, preferably 3 g / L to 5 g / L; Preferably, the temperature during the coprecipitation reaction is 40°C to 70°C.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The coprecipitation reaction includes a nucleation stage and a growth stage which are carried out sequentially; Preferably, the pH value of the nucleation stage is 11.4 to 12.8, preferably 11.8 to 12.3; Preferably, the pH value during the growth stage is from 9.6 to 10.8, preferably from 10.0 to 10.

4.

6. The preparation method according to claim 1, characterized in that: The target particle size refers to a median particle size D50 of 3 μm to 15 μm, preferably 6 μm to 10 μm.

7. The preparation method according to claim 1, characterized in that: The total concentration of metal ions in the metal salt solution is 1 mol / L to 3 mol / L; Preferably, the concentration of the precipitant solution is 20 wt % to 40 wt %.

8. The preparation method according to claim 1, characterized in that: The pH value of the base solution is 11.5 to 12.8; Preferably, the ammonia concentration of the base solution is 0.5 g / L to 4 g / L; Preferably, the concentration of the modifier in the base solution is 0.1 mol / L to 0.3 mol / L.

9. A modified high nickel precursor, characterized in that: The modified high-nickel precursor is prepared by the preparation method according to any one of claims 1 to 8; The chemical formula of the modified high nickel precursor is Ni x Co y Mn 1-x-y (OH)2 or Ni x Co y Al 1-x-y (OH)2, where 0.6≤x<1, 0≤y≤0.

2.

10. A positive electrode material, characterized in that: The positive electrode material is prepared from the modified high-nickel precursor described in claim 9.

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