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

Abstract

The invention provides a high-nickel-doped precursor, a preparation method thereof, a positive electrode material and application, and the preparation method comprises the following steps: mixing a precipitant solution, a complexing agent solution, a dopant solution, a metal mixed salt solution and a reaction base solution, and carrying out a co-precipitation reaction to obtain the high-nickel-doped precursor; the dopant solution comprises a single metal modified lignosulfonate. In the preparation method provided by the invention, the dopant solution and the precipitant solution are subjected to chemical reaction, and the generated sodium lignin sulfonate is used as an anionic surfactant, so that the dispersity of precipitate particles in the coprecipitation process is effectively improved, the agglomeration phenomenon of the precipitate particles is reduced, and the lattice constant of the high-nickel precursor is expanded; therefore, the charge-discharge performance of the ion battery is improved; besides, monometal modified lignosulfonate in the dopant solution is used as a dopant, and hydroxide precipitation can be slowly generated in the coprecipitation reaction process, so that uniform doping of a metal ion phase of the high-nickel precursor is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a method for preparing a doped high-nickel precursor, and in particular to a doped high-nickel precursor and a preparation method thereof, a positive electrode material and application thereof. Background Art

[0002] With the transformation of the global energy structure and the growing demand for high-energy-density batteries in mobile devices, the performance improvement of lithium-ion batteries, as the most mainstream secondary battery technology, has become a research hotspot in the field of new energy. In lithium-ion batteries, the performance of cathode materials directly affects the energy density, cycle stability and safety of the battery. In particular, high-nickel layered oxide cathode materials are considered to be an ideal choice for the next generation of lithium-ion batteries due to their high theoretical capacity and high energy density.

[0003] However, high-nickel layered oxide cathode materials face many challenges in practical applications. First, high-nickel materials are prone to lattice distortion during the charge and discharge process, resulting in structural instability, which in turn affects the cycle stability of the battery. Second, high-nickel material particles are prone to agglomeration, which reduces the specific surface area of ​​the electrode material and increases the diffusion resistance of lithium ions, thereby affecting the charge and discharge performance of the battery.

[0004] In order to solve the above problems, technicians in this field have tried a variety of modification strategies, including surface coating, ion doping and structural optimization. Among them, ion doping is an effective modification method, which changes the electrochemical properties of the material by introducing foreign ions. However, traditional doping methods often find it difficult to achieve uniform doping, and have limited effect on improving the material structure, which limits the further improvement of material performance.

[0005] CN115506021A discloses a single crystal ternary positive electrode material and a preparation method thereof, a lithium ion battery positive electrode and a lithium ion battery. The preparation method comprises step S1, first sintering a mixture including an NCM ternary precursor, a lithium salt, a first dopant and an optional second dopant to obtain a sintered product; step S2, crushing the sintered product to obtain a crushed material; step S3, mixing the coating agent and the crushed material for a second sintering to obtain a single crystal ternary positive electrode material; the first dopant is a strontium-containing compound, the second dopant is selected from any one or more of aluminum oxide, zirconium oxide, titanium dioxide, yttrium oxide and magnesium hydroxide, at least 30% of the sintering time in the first sintering uses a mixed gas containing oxygen, the volume fraction of oxygen in the mixed gas containing oxygen is 40-90%, and the temperature of the first sintering is lower than 950°C.

[0006] CN116715282A discloses a positive electrode material precursor and a preparation method thereof, a positive electrode material, a lithium ion battery and an electrical device, wherein the preparation method of the positive electrode material precursor comprises: in the process of preparing the positive electrode material precursor by a coprecipitation method, adding a chelating agent and a dopant to a reaction solution; wherein the chelating agent can undergo a chelating reaction with the cation of the dopant.

[0007] The preparation methods of doped high-nickel precursors disclosed in the prior art all have certain defects. The particles of the prepared doped high-nickel precursors are prone to agglomeration, and the diffusion resistance of ions is large, which leads to insufficient charging and discharging performance of the battery. There is also a problem that a uniformly doped high-nickel precursor cannot be obtained, resulting in an inability to effectively improve the structure of the material and thus the performance of the battery. Therefore, it is very important to develop and design a new type of doped high-nickel precursor and its preparation method, positive electrode material and application. Summary of the invention

[0008] In view of the deficiencies in the prior art, the object of the present invention is to provide a doped high-nickel precursor and a preparation method thereof, a positive electrode material and application. In the preparation method provided by the present invention, a dopant solution and a precipitant solution undergo a chemical reaction, and the generated sodium lignin sulfonate is used as an anionic surfactant, which effectively improves the dispersibility of precipitate particles during the co-precipitation process, reduces the agglomeration of precipitate particles, and expands the lattice constant of the high-nickel precursor, thereby improving the charge and discharge performance of the ion battery; in addition, the dopant solution uses a single metal-modified lignin sulfonate as a dopant, and the co-precipitation reaction process will slowly produce hydroxide precipitation, thereby achieving uniform doping of the metal ion phase of the high-nickel precursor; secondly, the preparation method has good industrial application prospects.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a doped high-nickel precursor, the preparation method comprising:

[0011] Mixing a precipitant solution, a complexing agent solution, a doping agent solution, a metal mixed salt solution and a reaction base solution to perform a coprecipitation reaction to obtain a doped high-nickel precursor;

[0012] The dopant in the dopant solution includes a single metal modified lignin sulfonate.

[0013] In the preparation method provided by the present invention, the dopant solution will chemically react with the precipitant solution, and the generated sodium lignin sulfonate is used as an anionic surfactant to effectively improve the dispersibility of the precipitate particles in the coprecipitation process, reduce the agglomeration phenomenon of the precipitate particles, and expand the lattice constant of the high-nickel precursor. The obtained doped high-nickel precursor is used to prepare a lithium-ion battery, which can improve the diffusion dynamics of the lithium-ion battery, thereby improving the charge and discharge performance of the lithium-ion battery; in addition, the dopant solution uses a single metal-modified lignin sulfonate as a dopant, and the coprecipitation reaction process slowly produces hydroxide precipitation, which realizes uniform doping of the metal ion phase of the high-nickel precursor, improves the structure of the high-nickel precursor, and further improves the performance of the lithium-ion battery prepared by the doped high-nickel precursor; secondly, the preparation method is simple and easy to implement, low in cost, easy to mass produce, and has good industrial application prospects.

[0014] Preferably, the mixing comprises a nucleation phase and a growth phase performed sequentially;

[0015] Nucleation stage: adding the precipitant solution, the complexing agent solution, the doping agent solution and the metal mixed salt solution to the reaction base liquid in parallel to perform a first coprecipitation reaction to obtain a first slurry;

[0016] Growth stage: adding the precipitant solution, the complexing agent solution, the doping agent solution and the metal mixed salt solution to the obtained first slurry in parallel, performing a second co-precipitation reaction, and obtaining a doped high-nickel precursor.

[0017] Preferably, in the nucleation stage, the pH of the first coprecipitation reaction is controlled to be 11.5-12.8, for example, it can be 11.5, 11.6, 11.7, 11.8, 11.9, 12, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7 or 12.8, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 11.8-12.3.

[0018] Preferably, during the growth stage, the pH of the second coprecipitation reaction is controlled to be 9.5 to 11.2, for example, it can be 9.5, 9.7, 9.9, 10, 10.2, 10.4, 10.6, 10.8, 11 or 11.2, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 10.0 to 10.6.

[0019] Preferably, in the nucleation stage and the growth stage, the ammonia concentration in the first coprecipitation reaction and the second coprecipitation reaction is independently controlled to be 2 to 12 g / L, for example, it can be 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but it is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 4 to 8 g / L.

[0020] Preferably, in the nucleation stage and the growth stage, the temperature of the first coprecipitation reaction and the second coprecipitation reaction are independently controlled to be 40-70° C. and the rotation speed is 200-600 rpm.

[0021] In the nucleation stage and the growth stage of the present invention, the temperature of the first coprecipitation reaction and the second coprecipitation reaction is independently controlled to be 40-70°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] In the nucleation stage and the growth stage of the present invention, the rotation speeds of the first coprecipitation reaction and the second coprecipitation reaction are independently controlled to be 200 to 600 rpm, for example, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm, but are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] Preferably, the D50 particle size of the precipitate in the first slurry obtained in the nucleation stage is 1.3 to 2.5 μm, for example, it can be 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm or 2.5 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the D50 particle size of the high-nickel doped precursor obtained in the growth stage is 3 to 15 μm, for example, it can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 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 to 10 μm.

[0025] Preferably, the mixing further comprises a transition phase between the nucleation phase and the growth phase;

[0026] The pH of the first slurry is gradually reduced in the transition stage. The pH of the first slurry before the gradual reduction is the same as the pH in the nucleation stage, and the pH of the first slurry after the gradual reduction is the same as the pH in the growth stage.

[0027] Preferably, the gradual reduction method is to reduce the addition rate of the precipitant solution and keep the addition rates of the complexing agent solution, the dopant solution and the metal mixed salt solution unchanged, the addition rate of the precipitant solution before the gradual reduction is the same as the addition rate in the nucleation stage, and the addition rate of the precipitant solution after the gradual reduction is the same as the addition rate in the growth stage.

[0028] Preferably, the monometallic modified lignin sulfonate comprises magnesium lignin sulfonate and / or calcium lignin sulfonate.

[0029] Preferably, the concentration of metal ions in the dopant solution is 0.01 to 0.5 mol / L, for example, it can be 0.01 mol / L, 0.02 mol / L, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 0.05 to 0.2 mol / L.

[0030] Preferably, the mass fraction of the precipitant solution is 20-40wt%, for example, it can be 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, 32wt%, 34wt%, 36wt%, 38wt% or 40wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the precipitant solution comprises sodium hydroxide solution and / or potassium hydroxide solution.

[0032] Preferably, the mass concentration of the complexing agent solution is 8 to 25wt%, for example, it can be 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt% or 25wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 12 to 16wt%.

[0033] Preferably, the metal salt in the metal mixed 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, or a combination of sulfate, nitrate and halide, preferably sulfate.

[0034] Preferably, the total concentration of metal ions in the metal mixed salt solution is 1.0 to 3.0 mol / L, for example, it can be 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L or 3.0 mol / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the reaction base solution is prepared from sodium hydroxide solution, concentrated ammonia water and pure water.

[0036] Preferably, the pH of the reaction base solution is 11.6-12.8, for example, it can be 11.6, 11.8, 12, 12.2, 12.4, 12.6 or 12.8, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 11.9-12.3.

[0037] Preferably, the ammonia concentration in the reaction base liquid is 2 to 12 g / L, for example, it can be 2 g / L, 3 g / L, 4 g / L, 5 g / L, 62 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L or 12 g / L, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 4 to 8 g / L.

[0038] Preferably, the coprecipitation reaction is carried out in a protective atmosphere.

[0039] Preferably, the protective atmosphere comprises nitrogen and / or an inert gas.

[0040] Preferably, the coprecipitation reaction further includes alkali washing, water washing and drying in sequence.

[0041] Preferably, the drying temperature is 80-150°C, for example, it can be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] In a second aspect, the present invention provides a doped high-nickel precursor, wherein the doped high-nickel precursor is obtained by the preparation method described in the first aspect.

[0043] Preferably, the chemical formula of the doped high nickel precursor comprises (Ni x Co y Mn 1-x-y ) z M 1-z (OH) 2 、(Nix Co y Al 1-x-y ) z M 1-z (OH) 2 or (Ni x Mn 1-x ) z M 1-z (OH) 2 , wherein 0.6≤x<1, the value of x can be, for example, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or 0.99; 0≤y<0.2, the value of y can be, for example, 0, 0.05, 0.1, 0.15 or 0.18; 0.95≤z<1, the value of z can be, for example, 0.95, 0.96, 0.97, 0.98 or 0.99. The above are not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0044] Preferably, the water content of the doped high-nickel precursor is lower than 1.0wt%, for example, it may be 0.99wt%, 0.95wt%, 0.90wt%, 0.85wt%, 0.80wt%, 0.7wt%, 0.6wt%, 0.5wt%, 0.4wt%, 0.3wt%, 0.2wt% or 0.1wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In a third aspect, the present invention provides a doped high-nickel positive electrode material, wherein the doped high-nickel positive electrode material is prepared from the doped high-nickel precursor described in the second aspect.

[0046] In a fourth aspect, the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the high-nickel doped positive electrode material described in the third aspect.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] In the preparation method provided by the present invention, the dopant solution will chemically react with the precipitant solution, and the generated sodium lignin sulfonate serves as an anionic surfactant, which effectively improves the dispersibility of precipitate particles in the coprecipitation process, reduces the agglomeration phenomenon of precipitate particles, and expands the lattice constant of the high-nickel precursor. The obtained doped high-nickel precursor is used to prepare a lithium-ion battery, which can improve the diffusion kinetics of the lithium-ion battery, thereby improving the charge and discharge performance of the lithium-ion battery; in addition, the dopant solution uses a single metal-modified lignin sulfonate as a dopant, and the hydroxide precipitate that is slowly generated during the coprecipitation reaction process realizes uniform doping of the metal ion phase of the high-nickel precursor, improves the structure of the high-nickel precursor, and further improves the performance of the lithium-ion battery prepared by the doped high-nickel precursor; secondly, the preparation method is simple and easy to implement, low in cost, easy to mass produce, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a SEM image of the high-nickel-doped precursor prepared by the preparation method provided in Example 1.

[0050] Figure 2 This is an SEM image of the high-nickel-doped precursor prepared by the preparation method provided in Comparative Example 1. DETAILED DESCRIPTION

[0051] 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 used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0052] Example 1

[0053] This embodiment provides a method for preparing a high-nickel doped precursor, the preparation method comprising:

[0054] (1) Nucleation stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, magnesium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the reaction bottom liquid (pH 12; ammonia concentration 6 g / L) in parallel, and the pH is controlled to be 12, the ammonia concentration is 6 g / L, the temperature is 55° C., and the rotation speed is 400 rpm to perform a first coprecipitation reaction to obtain a first slurry containing a precipitate with a D50 particle size of 1.8 μm;

[0055] (2) Transition stage: in nitrogen and / or inert gas, gradually reducing the pH of the first slurry, wherein the pH of the first slurry before the gradual reduction is the same as the pH in the nucleation stage, and the pH of the first slurry after the gradual reduction is the same as the pH in the growth stage;

[0056] The stepwise reduction method is to uniformly reduce the addition rate of the sodium hydroxide solution and keep the addition rates of the ammonia water, the magnesium lignin sulfonate solution and the nickel-cobalt-manganese mixed salt solution unchanged, the addition rate of the sodium hydroxide solution before the stepwise reduction is the same as the addition rate in the nucleation stage, and the addition rate of the sodium hydroxide solution after the stepwise reduction is the same as the addition rate in the growth stage;

[0057] (3) Growth stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, magnesium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the obtained first slurry in parallel, and the pH is controlled to be 10.3, the ammonia concentration is 6 g / L, the temperature is 55° C., and the rotation speed is 400 rpm. A second coprecipitation reaction is carried out, and after solid-liquid separation, alkali washing, water washing and drying are carried out in sequence to obtain a doped high-nickel precursor with a D50 particle size of 10 μm and a water content of 0.5 wt%;

[0058] In the above nucleation stage, transition stage and growth stage:

[0059] The mass fraction of the sodium hydroxide solution is 30wt%; the concentration of the metal ions in the magnesium lignin sulfonate solution is 0.1mol / L; the nickel-cobalt-manganese mixed salt solution is (sulfate, nitrate or halide, the total concentration of the metal ions is 2mol / L, and the molar ratio of nickel ions, cobalt ions and manganese ions is 90:5:5.

[0060] Example 2

[0061] This embodiment provides a method for preparing a high-nickel doped precursor, the preparation method comprising:

[0062] (1) Nucleation stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, calcium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the reaction base liquid (pH 11.9; ammonia concentration 4 g / L) in parallel, and the pH is controlled to be 11.8, the ammonia concentration is 4 g / L, the temperature is 60° C., and the rotation speed is 300 rpm to perform a first coprecipitation reaction to obtain a first slurry containing a precipitate with a D50 particle size of 1.3 μm;

[0063] (2) Transition stage: in nitrogen and / or inert gas, gradually reducing the pH of the first slurry, wherein the pH of the first slurry before the gradual reduction is the same as the pH in the nucleation stage, and the pH of the first slurry after the gradual reduction is the same as the pH in the growth stage;

[0064] The stepwise reduction method is to uniformly reduce the addition rate of the sodium hydroxide solution and keep the addition rates of the ammonia water, the calcium lignin sulfonate solution and the nickel-cobalt-manganese mixed salt solution unchanged, the addition rate of the sodium hydroxide solution before the stepwise reduction is the same as the addition rate in the nucleation stage, and the addition rate of the sodium hydroxide solution after the stepwise reduction is the same as the addition rate in the growth stage;

[0065] (3) Growth stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, calcium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the obtained first slurry in parallel, and the pH is controlled to be 10.0, the ammonia concentration is 4 g / L, the temperature is 60° C., and the rotation speed is 300 rpm. A second coprecipitation reaction is carried out, and after solid-liquid separation, alkali washing, water washing and drying are carried out in sequence to obtain a doped high-nickel precursor with a D50 particle size of 6 μm and a water content of 0.8 wt%;

[0066] In the above nucleation stage, transition stage and growth stage:

[0067] The mass fraction of the sodium hydroxide solution is 25wt%; the concentration of the metal ions in the calcium lignin sulfonate solution is 0.05mol / L; the nickel-cobalt-manganese mixed salt solution is (sulfate, nitrate or halide, the total concentration of the metal ions is 1.5mol / L, and the molar ratio of nickel ions, cobalt ions and manganese ions is 8:1:1.

[0068] Example 3

[0069] This embodiment provides a method for preparing a high-nickel doped precursor, the preparation method comprising:

[0070] (1) Nucleation stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, magnesium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the reaction bottom liquid (pH 12.3; ammonia concentration 8 g / L) in parallel, and the pH is controlled to be 12.3, the ammonia concentration is 8.0 g / L, the temperature is 50° C., and the rotation speed is 500 rpm to perform a first coprecipitation reaction to obtain a first slurry containing a precipitate with a D50 particle size of 2.5 μm;

[0071] (2) Transition stage: in nitrogen and / or inert gas, gradually reducing the pH of the first slurry, wherein the pH of the first slurry before the gradual reduction is the same as the pH in the nucleation stage, and the pH of the first slurry after the gradual reduction is the same as the pH in the growth stage;

[0072] The stepwise reduction method is to uniformly reduce the addition rate of the sodium hydroxide solution and keep the addition rates of the ammonia water, the magnesium lignin sulfonate solution and the nickel-cobalt-manganese mixed salt solution unchanged, the addition rate of the sodium hydroxide solution before the stepwise reduction is the same as the addition rate in the nucleation stage, and the addition rate of the sodium hydroxide solution after the stepwise reduction is the same as the addition rate in the growth stage;

[0073] (3) Growth stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, magnesium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the obtained first slurry in parallel, and the pH is controlled to be 10.6, the ammonia concentration is 8 g / L, the temperature is 50° C., and the rotation speed is 500 rpm. A second coprecipitation reaction is carried out, and after solid-liquid separation, alkali washing, water washing and drying are carried out in sequence to obtain a doped high-nickel precursor with a D50 particle size of 8 μm and a water content of 0.3 wt%;

[0074] In the above nucleation stage, transition stage and growth stage:

[0075] The mass fraction of the sodium hydroxide solution is 35wt%; the concentration of the metal ions in the magnesium lignin sulfonate solution is 0.2mol / L; the nickel-cobalt-manganese mixed salt solution is (sulfate, nitrate or halide, the total concentration of the metal ions is 2.5mol / L, and the molar ratio of nickel ions, cobalt ions and manganese ions is 95:2:3.

[0076] Example 4

[0077] This embodiment provides a method for preparing a high-nickel doped precursor, the preparation method comprising:

[0078] (1) Nucleation stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, calcium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the reaction base liquid (pH 11.6; ammonia concentration 2 g / L) in parallel, and the pH is controlled to be 11.5, the ammonia concentration is 2 g / L, the temperature is 70° C., and the rotation speed is 200 rpm to perform a first coprecipitation reaction to obtain a first slurry containing a precipitate with a D50 particle size of 1.3 μm;

[0079] (2) Transition stage: in nitrogen and / or inert gas, gradually reducing the pH of the first slurry, wherein the pH of the first slurry before the gradual reduction is the same as the pH in the nucleation stage, and the pH of the first slurry after the gradual reduction is the same as the pH in the growth stage;

[0080] The stepwise reduction method is to uniformly reduce the addition rate of the sodium hydroxide solution and keep the addition rates of the ammonia water, the calcium lignin sulfonate solution and the nickel-cobalt-manganese mixed salt solution unchanged, the addition rate of the sodium hydroxide solution before the stepwise reduction is the same as the addition rate in the nucleation stage, and the addition rate of the sodium hydroxide solution after the stepwise reduction is the same as the addition rate in the growth stage;

[0081] (3) Growth stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, calcium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the obtained first slurry in parallel, and the pH is controlled to be 9.5, the ammonia concentration is 2 g / L, the temperature is 70° C., and the rotation speed is 200 rpm. A second coprecipitation reaction is carried out, and after solid-liquid separation, alkali washing, water washing and drying are carried out in sequence to obtain a doped high-nickel precursor with a D50 particle size of 3 μm and a water content of 0.2 wt%;

[0082] In the above nucleation stage, transition stage and growth stage:

[0083] The mass fraction of the sodium hydroxide solution is 20wt%; the concentration of the metal ions in the calcium lignin sulfonate solution is 0.01mol / L; the nickel-cobalt-manganese mixed salt solution is (sulfate, nitrate or halide, the total concentration of the metal ions is 1mol / L, and the molar ratio of nickel ions, cobalt ions and manganese ions is 8:1:1.

[0084] Example 5

[0085] This embodiment provides a method for preparing a high-nickel doped precursor, the preparation method comprising:

[0086] (1) Nucleation stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, magnesium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the reaction bottom liquid (pH 12.8; ammonia concentration 12 g / L) in parallel, and the pH is controlled to be 12.8, the ammonia concentration is 12 g / L, the temperature is 40° C., and the rotation speed is 600 rpm to perform a first coprecipitation reaction to obtain a first slurry containing a precipitate with a D50 particle size of 2.5 μm;

[0087] (2) Transition stage: in nitrogen and / or inert gas, gradually reducing the pH of the first slurry, wherein the pH of the first slurry before the gradual reduction is the same as the pH in the nucleation stage, and the pH of the first slurry after the gradual reduction is the same as the pH in the growth stage;

[0088] The stepwise reduction method is to uniformly reduce the addition rate of the sodium hydroxide solution and keep the addition rates of the ammonia water, the dopant solution and the nickel-cobalt-manganese mixed salt solution unchanged, the addition rate of the sodium hydroxide solution before the stepwise reduction is the same as the addition rate in the nucleation stage, and the addition rate of the sodium hydroxide solution after the stepwise reduction is the same as the addition rate in the growth stage;

[0089] (3) Growth stage: In nitrogen and / or inert gas, sodium hydroxide solution, ammonia water, magnesium lignin sulfonate solution and nickel-cobalt-manganese mixed salt solution are added to the obtained first slurry in parallel, and the pH is controlled to be 11.2, the ammonia concentration is 12 g / L, the temperature is 40° C., and the rotation speed is 600 rpm. A second coprecipitation reaction is carried out, and after solid-liquid separation, alkali washing, water washing and drying are carried out in sequence to obtain a doped high-nickel precursor with a D50 particle size of 15 μm and a water content of 0.98 wt%;

[0090] In the above nucleation stage, transition stage and growth stage:

[0091] The mass fraction of the sodium hydroxide solution is 40wt%; the concentration of the metal ions in the magnesium lignin sulfonate solution is 0.5mol / L; the nickel-cobalt-manganese mixed salt solution is (sulfate, nitrate or halide, the total concentration of the metal ions is 3.0mol / L, and the molar ratio of nickel ions, cobalt ions and manganese ions is 90:5:5.

[0092] Example 6

[0093] This embodiment provides a method for preparing a doped high-nickel precursor, which is the same as that of Embodiment 1 except that the magnesium lignin sulfonate solution is replaced by a copper lignin sulfonate solution of the same concentration.

[0094] Example 7

[0095] This embodiment provides a method for preparing a doped high-nickel precursor, which is the same as that of Embodiment 1 except that the magnesium lignin sulfonate solution is replaced by an iron lignin sulfonate solution of the same concentration.

[0096] Example 8

[0097] This embodiment provides a method for preparing a doped high-nickel precursor, which is the same as that of Embodiment 1 except that the magnesium lignin sulfonate solution is replaced by a zinc lignin sulfonate solution of the same concentration.

[0098] Example 9

[0099] This embodiment provides a method for preparing a doped high-nickel precursor, which is the same as that of Embodiment 1 except that the concentration of metal ions in the magnesium lignin sulfonate solution is 0.005 mol / L.

[0100] Example 10

[0101] This embodiment provides a method for preparing a doped high-nickel precursor, which is the same as that of Embodiment 1 except that the concentration of metal ions in the magnesium lignin sulfonate solution is 0.8 mol / L.

[0102] Comparative Example 1

[0103] This comparative example provides a method for preparing a doped high-nickel precursor, which is the same as Example 1 except that the magnesium lignin sulfonate solution is replaced by a magnesium sulfate solution of the same concentration.

[0104] Comparative Example 2

[0105] This comparative example provides a method for preparing a high-nickel precursor, which is the same as Example 1 except that the magnesium lignin sulfonate solution added in the nucleation stage, transition stage and growth stage is omitted.

[0106] The high-nickel doped precursor was prepared by the preparation method provided in Example 1, and the obtained high-nickel doped precursor was tested by scanning electron microscopy to obtain a SEM image of the high-nickel doped precursor prepared by the preparation method in Example 1. Figure 1 shown; from Figure 1 It can be seen that the introduction of single metal modified lignin sulfonate as a dopant in the precursor synthesis stage can obtain a doped high nickel precursor with good particle dispersion, good sphericity, and basically no irregular small particles and no cracks;

[0107] The high-nickel doped precursor was prepared by the preparation method provided in Comparative Example 1, and the obtained high-nickel doped precursor was tested by scanning electron microscopy to obtain a SEM image of the high-nickel doped precursor prepared by the preparation method in Comparative Example 1. Figure 2 shown; from Figure 2 It can be seen that by introducing magnesium sulfate as a dopant in the precursor synthesis stage, the particles of the obtained high-nickel doped precursor have poor dispersion and sphericity, there are many small irregular particles, and some particles have obvious cracks.

[0108] pass Figure 1 and Figure 2 From the comparison, it can be seen that the introduction of single metal modified lignin sulfonate as a dopant in the precursor synthesis stage significantly improves the particle morphology and crystal structure of the high nickel precursor, achieves uniform bulk doping of metal ions, and improves the uneven distribution of stress.

[0109] A doped high-nickel precursor was prepared by the preparation method provided in the above embodiment and comparative example, and the obtained doped high-nickel precursor was mixed with lithium carbonate at a mass ratio of 1:1.1 and sintered at 820° C. for 16 hours to obtain a positive electrode material;

[0110] The obtained positive electrode material is used to prepare a lithium-ion battery: the obtained positive electrode material, conductive carbon black SP (TIMCAL) and polyvinylidene fluoride PVDF (HSV900) are mixed in a mass ratio of 90:5:5, N-methylpyrrolidone is used as a solvent, and the mixture is stirred into a slurry. The obtained slurry is evenly coated on an aluminum foil with a scraper with a coating gap of 100 um; after coating, it is first blown dry, then rolled and cut into circular electrode sheets, and then vacuum dried at 120° C. and the weight of the electrode sheets is weighed to obtain a button half-cell positive electrode sheet; a metal lithium sheet is used as a negative electrode, a PP microporous membrane is used as a separator, and a lithium battery basic electrolyte is used as an electrolyte. The positive electrode sheet, the metal lithium sheet, the separator and the electrolyte are assembled to obtain a button battery;

[0111] The battery test was performed using a battery test system (Blue Electric CT2001A, Wuhan, China). First, the battery was activated three times at 0.1C rate / 2.7-4.3V, and then the activated button cell was tested for electrochemical performance at 2.7-4.3V@0.1C / 1C. The test results are shown in Table 1.

[0112] Table 1

[0113]

[0114] From Table 1, we can get:

[0115] (1) The lithium-ion battery prepared by the high-nickel-doped precursor prepared by the preparation method provided in Examples 1 to 5 has a high initial discharge capacity, excellent rate performance and strong cycle stability;

[0116] (2) By comparing Example 1 with Examples 6 to 8, it can be seen that the type of the single metal modified lignin sulfonate in the present invention affects the performance of the lithium ion battery; when the single metal modified lignin sulfonate is magnesium lignin sulfonate and / or calcium lignin sulfonate, the lithium ion battery finally obtained exhibits a higher initial discharge capacity, better rate performance and stronger cycle stability; this is because Mg 2+ and Ca 2+ The ionic radius of Ni 2+ Similar, they replace Ni in the lattice 2+ The position of Zn can inhibit the cation mixing phenomenon and modify the electronic structure of the material, so that the material has a higher initial discharge capacity, better rate performance and stronger cycle stability; but Zn 2+ and Fe 3+ The ionic radius of Ni 2+ The doping may cause lattice distortion and greater volume expansion and contraction during charge and discharge, resulting in reduced structural stability. 2+ and Fe 3+Doping may increase the electronic resistance of the material, reduce the electrical conductivity, and thus affect the electrochemical performance; therefore, Mg 2+ and Ca 2+ Ion doping is usually more than Zn 2+ and Fe 3+ Ion doping is more effective in improving the performance of NCM ternary cathode materials;

[0117] (3) By comparing Example 1 with Examples 9 and 10, it can be seen that the concentration of metal ions in the single metal modified lignin sulfonate solution of the present invention will affect the performance of the lithium ion battery; when the concentration of metal ions in the single metal modified lignin sulfonate solution is 0.01-0.5 mol / L, preferably 0.05-0.2 mol / L, the lithium ion battery finally obtained exhibits a higher initial discharge capacity, better rate performance and stronger cycle stability. This is because if the concentration of the dopant solution is too low, the expected doping effect may not be achieved, resulting in no obvious improvement in the electrochemical properties of the material; on the contrary, if the concentration of the dopant solution is too high, it may cause excessive distortion of the lattice and cause greater volume expansion and contraction during the charge and discharge process, affecting the stability of the crystal structure of the material, and may also increase the resistance to lithium ion transmission, reduce the conductivity, and affect the charge and discharge efficiency of the battery; therefore, the concentration of metal ions in the single metal modified lignin sulfonate solution of the present invention cannot be too high or too low, and needs to be controlled within a reasonable range;

[0118] (4) By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that in the preparation method provided by the present invention, the dopant solution will chemically react with the precipitant solution, and the generated sodium lignin sulfonate acts as an anionic surfactant, which effectively improves the dispersibility of the precipitate particles during the co-precipitation process, reduces the agglomeration of the precipitate particles, and expands the lattice constant of the high-nickel precursor. The obtained doped high-nickel precursor is used to prepare a lithium-ion battery, which can improve the diffusion kinetics of the lithium-ion battery, thereby improving the charge and discharge performance of the lithium-ion battery; in addition, the dopant solution uses a single metal-modified lignin sulfonate as a dopant, and the co-precipitation reaction process will slowly produce hydroxide precipitate, thereby achieving uniform doping of the metal ion phase of the high-nickel precursor, improving the structure of the high-nickel precursor, and further improving the performance of the lithium-ion battery prepared using the doped high-nickel precursor; secondly, the preparation method is simple and easy to implement, low cost, easy to scale production, and has good industrial application prospects.

[0119] 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 high-nickel doped precursor, characterized in that: The preparation method comprises: Mixing a precipitant solution, a complexing agent solution, a doping agent solution, a metal mixed salt solution and a reaction base solution to perform a coprecipitation reaction to obtain a doped high-nickel precursor; The dopant in the dopant solution includes a single metal modified lignin sulfonate.

2. The preparation method according to claim 1, characterized in that: The mixing includes a nucleation stage and a growth stage performed sequentially; Nucleation stage: adding the precipitant solution, the complexing agent solution, the doping agent solution and the metal mixed salt solution to the reaction base solution in parallel to perform a first coprecipitation reaction to obtain a first slurry; Growth stage: adding the precipitant solution, the complexing agent solution, the doping agent solution and the metal mixed salt solution to the obtained first slurry in parallel, performing a second co-precipitation reaction, and obtaining a doped high-nickel precursor.

3. The preparation method according to claim 2, characterized in that: In the nucleation stage, the pH of the first coprecipitation reaction is controlled to be 11.5 to 12.8, preferably 11.8 to 12.3; Preferably, during the growth stage, the pH of the second coprecipitation reaction is controlled to be 9.5 to 11.2, preferably 10.0 to 10.6; Preferably, in the nucleation stage and the growth stage, the ammonia concentration during the first coprecipitation reaction and the second coprecipitation reaction is independently controlled to be 2 to 12 g / L, preferably 4 to 8 g / L; Preferably, in the nucleation stage and the growth stage, the temperature of the first coprecipitation reaction and the second coprecipitation reaction are independently controlled to be 40-70° C. and the rotation speed is 200-600 rpm; Preferably, the D50 particle size of the precipitate in the first slurry obtained in the nucleation stage is 1.3 to 2.5 μm; Preferably, the D50 particle size of the high-nickel doped precursor obtained in the growth stage is 3 to 15 μm, preferably 6 to 10 μm.

4. The preparation method according to claim 2 or 3, characterized in that: The mixing also includes a transition phase between the nucleation phase and the growth phase; The pH of the first slurry is gradually reduced in the transition stage, the pH of the first slurry before the gradual reduction is the same as the pH in the nucleation stage, and the pH of the first slurry after the gradual reduction is the same as the pH in the growth stage; Preferably, the stepwise reduction is carried out by reducing the addition rate of the precipitant solution and keeping the addition rates of the complexing agent solution, the doping agent solution and the metal mixed salt solution unchanged; The addition rate of the precipitant solution before the step-wise reduction is the same as the addition rate in the nucleation stage, and the addition rate of the precipitant solution after the step-wise reduction is the same as the addition rate in the growth stage.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The single metal modified lignin sulfonate comprises magnesium lignin sulfonate and / or calcium lignin sulfonate; Preferably, the concentration of metal ions in the dopant solution is 0.01 to 0.5 mol / L, preferably 0.05 to 0.2 mol / L.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The mass fraction of the precipitant solution is 20 to 40 wt %; Preferably, the mass concentration of the complexing agent solution is 8 to 25 wt%, preferably 12 to 16 wt%; Preferably, the total concentration of metal ions in the metal mixed salt solution is 1.0 to 3.0 mol / L; Preferably, the pH of the reaction base solution is 11.6 to 12.8, preferably 11.9 to 12.3; Preferably, the ammonia concentration in the reaction bottom solution is 2 to 12 g / L, preferably 4 to 8 g / L.

7. A high nickel-doped precursor, characterized in that: The high-nickel doped precursor is obtained by the preparation method according to any one of claims 1 to 6.

8. The high-nickel doped precursor according to claim 7, characterized in that: The chemical formula of the doped high nickel precursor includes (Ni x Co y Mn 1-x-y ) z M 1-z (OH)2、(Ni x Co y Al 1-x-y ) z M 1-z (OH)2 or (Ni x Mn 1-x ) z M 1-z (OH)2, where 0.6≤x<1, 0≤y<0.2, 0.95≤z<1; Preferably, the water content of the high-nickel doped precursor is lower than 1.0 wt %.

9. A high nickel-doped positive electrode material, characterized in that: The high-nickel doped positive electrode material is prepared from the high-nickel doped precursor according to claim 7 or 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the doped high-nickel positive electrode material according to claim 9.

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