Large-particle ultrahigh-nickel ternary precursor as well as preparation method and application thereof

Abstract

The invention provides a large-particle ultrahigh-nickel ternary precursor as well as a preparation method and application thereof. The method comprises the following steps: S1, adding a ternary mixed metal salt solution, a precipitator solution and a complexing agent solution into a reaction base solution in a parallel flow manner, and carrying out a nucleation stage reaction in a coprecipitation process; s2, after the nucleation stage reaction is finished, first-time growth stage reaction and second-time growth stage reaction are sequentially carried out, the large-particle ultrahigh-nickel ternary precursor is obtained, and the pH value of the first-time growth stage reaction is larger than that of the second-time growth stage reaction. By improving the preparation method of the ultra-high nickel ternary precursor, the ultra-high nickel ternary precursor which is large in particle size, good in sphericity degree, high in tap density and free of cracks is finally obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of positive electrode precursor materials, and in particular relates to a large-particle ultra-high nickel ternary precursor and a preparation method and application thereof. Background Art

[0002] In today's rapidly developing new energy field, the key role of battery technology, especially lithium-ion battery technology, has become increasingly prominent. With the popularization of electric vehicles and large-scale energy storage systems, the market's requirements for battery performance are becoming higher and higher, especially in terms of energy density, cycle stability and safety. High-nickel ternary positive electrode materials have become one of the important choices for lithium-ion battery positive electrode materials due to their high energy density and cost-effectiveness. However, during the preparation and application of high-nickel ternary positive electrode materials, they often face problems such as particle cracks and structural instability, which not only affects the cycle performance of the assembled lithium-ion batteries, but may also bring safety hazards, thus limiting their potential in large-scale applications.

[0003] The preparation methods of traditional high-nickel ternary precursors mainly include coprecipitation method, sol-gel method, etc. Although the composition and structure of the precursor material can be well controlled to a certain extent, it is difficult to completely avoid the phenomenon of cracking of larger particles during the preparation process, especially when the molar content of nickel element is as high as 90% or more, the cracking of the precursor particles is more obvious. This is mainly due to the weak strength of the Ni-O bond. The large number of Ni-O bonds in the ultra-high nickel precursor makes the structure of the material unstable. Therefore, the spherical particles are prone to cracking or even breaking under high stirring intensity. The positive electrode material sintered with the above precursor will also crack or break to a greater extent, which ultimately greatly reduces the mechanical strength of the positive electrode material. In the process of charge and discharge cycle, it is corresponding to excessive contact with the electrolyte to produce serious side reactions, thereby accelerating the degradation of the positive electrode material and shortening the service life of the lithium-ion battery.

[0004] In order to solve the above problems, on the one hand, the prior art generally adopts a method of reducing the stirring intensity to alleviate the phenomenon of cracks in spherical particles during the preparation of large-particle high-nickel ternary precursors, but reducing the stirring speed easily leads to a deterioration in the sphericity of the particles and a low tap density, thereby affecting the comprehensive performance of the positive electrode material. On the other hand, in the prior art, for example, Chinese patent CN114620777A discloses a method for preparing a crack-free ultra-high nickel precursor material by anion and cation doping and a double-sided feeding scheme, but the process of dual ion doping is complicated, costly, and requires strict control of the accuracy of the feed, which is not easy to carry out large-scale industrial production.

[0005] Therefore, it is urgent to develop a simple-to-operate method for preparing crack-free, large-particle, ultra-high nickel ternary precursor. Summary of the invention

[0006] In view of the deficiencies of the prior art, the object of the present invention is to provide a large-particle ultra-high nickel ternary precursor and a preparation method and application thereof. The present invention improves the preparation method of the ultra-high nickel ternary precursor, and finally obtains an ultra-high nickel ternary precursor with a large particle size, good sphericity, high tap density and no cracks.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a large-particle ultra-high nickel ternary precursor, the method comprising the following steps:

[0009] S1. In the reaction bottom liquid, a ternary mixed metal salt solution, a precipitant solution and a complexing agent solution are introduced in parallel to carry out the nucleation stage reaction of the coprecipitation process;

[0010] S2. After the nucleation stage reaction is completed, the first growth stage reaction and the second growth stage reaction are carried out in sequence to obtain the large-particle ultra-high nickel ternary precursor, wherein the pH value of the first growth stage reaction is greater than the pH value of the second growth stage reaction.

[0011] The present invention adopts an improved coprecipitation method and combines the control of reaction parameters to prepare an ultra-high nickel ternary precursor. During the first growth stage reaction, the dispersion and sphericity of the precursor are improved; in the second growth stage reaction, the primary grains are refined by adjusting the pH and the primary grains are formed into a mesh structure of cross-growth, which helps to improve the structural stability and conductivity of the precursor material, and finally obtains a large-particle ultra-high nickel ternary precursor with good dispersion, good sphericity, high tap density and no cracks, so that the positive electrode material prepared by using the large-particle ultra-high nickel ternary precursor has higher capacity and better cycle performance, thereby comprehensively improving the cycle stability and safety of the assembled secondary battery.

[0012] The preparation method provided by the present invention does not require the addition of other difficult-to-handle organic or inorganic additives during the overall coprecipitation reaction, nor does it require complex element doping treatment. The preparation method is simple to operate and is fully compatible with the production line in the prior art, which is conducive to industrial production.

[0013] It should be noted that the "large particles" in the large-particle ultra-high nickel ternary precursor of the present invention refers to the situation where the maximum particle size of the ternary precursor is not less than 6μm; and "ultra-high nickel" refers to the situation where the molar percentage of nickel element in the ternary precursor exceeds 85%.

[0014] Preferably, the reaction base solution in step S1 comprises a precipitant, a complexing agent and a solvent.

[0015] In the present invention, the precipitant exemplarily includes at least one of sodium hydroxide, potassium hydroxide or lithium hydroxide; the complexing agent exemplarily includes at least one of ammonia water, ammonium carbonate, ammonium bicarbonate, oxalic acid or ethylenediaminetetraacetic acid (EDTA), preferably ammonia water.

[0016] Preferably, the solvent comprises water.

[0017] Preferably, the concentration of the complexing agent in the reaction base solution in step S1 is 1.5-12 g / L, for example, 1.5 g / L, 2 g / L, 4 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, etc.

[0018] Preferably, the pH value of the reaction base solution in step S1 is 11.3-12.9, for example, it can be 11.3, 11.4, 11.6, 11.8, 12.0, 12.2, 12.4, 12.6, 12.8, 12.9, etc.

[0019] Preferably, the ternary mixed metal salt solution in step S1 comprises a nickel-cobalt-manganese mixed metal salt solution.

[0020] In the present invention, the nickel-cobalt-manganese mixed metal salt solution exemplarily includes at least one of a nickel-cobalt-manganese mixed metal sulfate solution, a nickel-cobalt-manganese mixed metal nitrate solution or a nickel-cobalt-manganese mixed metal halide solution, and is more preferably a nickel-cobalt-manganese mixed metal sulfate solution.

[0021] Preferably, the total concentration of metal ions in the ternary mixed metal salt solution in step S1 is 1.0-3.0 mol / L, for example, it can be 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3.0 mol / L, etc.

[0022] Preferably, the mass concentration of the precipitant solution in step S1 is 20-40%, for example, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, etc.

[0023] In the present invention, the precipitant solution illustratively includes at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution or a lithium hydroxide aqueous solution.

[0024] Preferably, the nucleation stage reaction in step S1 is carried out under an inert atmosphere.

[0025] Preferably, the pH value of the nucleation stage reaction in step S1 is greater than the pH value of the first growth stage reaction.

[0026] Preferably, the pH value of the nucleation stage reaction in step S1 is 11.4-12.7, preferably 11.7-12.3, for example, it can be 11.4, 11.6, 11.7, 11.8, 12.0, 12.2, 12.3, 12.4, 12.6, 12.7, etc.

[0027] Preferably, the reaction time of the nucleation stage in step S1 is 2 to 6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc.

[0028] Preferably, the atmosphere of the first growth stage reaction in step S2 contains oxygen.

[0029] In the present invention, the atmosphere of the first growth stage reaction exemplarily includes at least one of a combination of nitrogen and air, a combination of nitrogen and oxygen, a combination of argon and air, or a combination of argon and oxygen.

[0030] Preferably, the volume fraction of oxygen in the atmosphere of the first growth stage reaction in step S2 is 0.5-10%, preferably 2-5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, etc. The present invention regulates the volume fraction of oxygen to a suitable range, so as to achieve the effect of improving the dispersibility and sphericity of the large-particle ultra-high nickel ternary precursor.

[0031] Preferably, in step S2, the feed rate of the precipitant solution in the first growth stage reaction is lower than the feed rate of the precipitant solution in the nucleation stage reaction.

[0032] Preferably, the pH value of the first growth stage reaction in step S2 is 10.8-11.4, preferably 11.0-11.2, for example, it can be 10.8, 10.9, 11.0, 11.02, 11.05, 11.08, 11.1, 11.12, 11.15, 11.18, 11.2, 11.3, 11.4, etc.

[0033] Preferably, the average particle size of the particles after the first growth stage reaction in step S2 is 3 to 8 μm, preferably 4 to 6 μm, for example, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, etc. The present invention regulates the average particle size of the particles after the first growth stage reaction to ensure that the obtained particles are substantially free of cracks. If all the particles are larger in average particle size, microcracks will occur in some particles, affecting the quality of subsequent large particle precursors.

[0034] Preferably, the second growth stage reaction in step S2 is carried out under an inert atmosphere, which exemplarily includes nitrogen and / or argon.

[0035] Preferably, in step S2, the feed rate of the precipitant solution in the second growth stage reaction is lower than the feed rate of the precipitant solution in the first growth stage reaction.

[0036] Preferably, the pH value of the second growth stage reaction in step S2 is 9.6-10.8, preferably 10.0-10.4, for example, it can be 9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, etc.

[0037] In the present invention, after the second growth stage reaction in step S2 is completed, a post-processing step is also included, and the post-processing step includes washing and drying treatments in sequence.

[0038] Furthermore, the washing includes alkali washing and water washing in sequence, and the alkali washing and water washing are performed no less than three times.

[0039] Furthermore, the drying temperature is 80-150°C, for example, 80°C, 100°C, 120°C, 150°C, etc.

[0040] Preferably, the average particle size of the large-particle ultra-high nickel ternary precursor in step S2 is 6 to 18 μm, preferably 10 to 14 μm, for example, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 18 μm, etc. The present invention regulates the average particle size of the particles after the second growth stage reaction is completed, so that the precursor can be refined through dissolution-recrystallization to form a cross-net-like loose structure. If all particles are of a smaller average particle size, it will cause the primary grains to be unable to be sufficiently refined and cross-grown through sufficient dissolution-recrystallization, and it is impossible to avoid the phenomenon that larger particles do not produce microcracks.

[0041] Preferably, the chemical formula of the large particle ultra-high nickel ternary precursor in step S2 is Ni x Co y Mn 1-x-y (OH)2, wherein 0.85≤x<1, and x can be, for example, 0.85, 0.88, 0.9, 0.92, 0.95, 0.98, etc.; 0.02≤y<0.15, and y can be, for example, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, etc.

[0042] Preferably, the water content of the large-particle ultra-high nickel ternary precursor in step S2 is not higher than 0.8wt.%, for example, it can be 0.05wt.%, 0.1wt.%, 0.2wt.%, 0.3wt.%, 0.4wt.%, 0.5wt.%, 0.6wt.%, 0.7wt.%, 0.8wt.%, etc.

[0043] In the present invention, the temperature during the entire co-precipitation process of preparing large-particle ultra-high nickel ternary precursor is 50-70°C, for example, 50°C, 55°C, 60°C, 65°C, 70°C, etc.

[0044] In a second aspect, the present invention provides a large-particle ultra-high nickel ternary precursor, wherein the large-particle ultra-high nickel ternary precursor is prepared by the method for preparing a large-particle ultra-high nickel ternary precursor according to the first aspect.

[0045] In a third aspect, the present invention provides a positive electrode, which includes a positive electrode active material, and the positive electrode active material is prepared from the large-particle ultra-high nickel ternary precursor according to the second aspect.

[0046] In the present invention, the positive electrode active material is exemplarily prepared by calcining the large-particle ultra-high nickel ternary precursor and a lithium source according to the second aspect under an oxygen atmosphere.

[0047] In a fourth aspect, the present invention provides a secondary battery, comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises the positive electrode according to the third aspect.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention provides a method for preparing a large-particle ultra-high nickel ternary precursor, which adopts an improved coprecipitation method and combines the control of reaction parameters to prepare an ultra-high nickel ternary precursor. During the first growth stage reaction, the dispersion and sphericity of the precursor are improved; in the second growth stage reaction, the primary grains are refined by adjusting the pH and the primary grains are formed into a mesh structure of cross-growth, which helps to improve the structural stability and conductivity of the precursor material, and finally obtains a large-particle ultra-high nickel ternary precursor with good dispersion, good sphericity, high tap density and no cracks, so that the positive electrode material prepared by using the large-particle ultra-high nickel ternary precursor has higher capacity and better cycle performance, thereby comprehensively improving the cycle stability and safety of the assembled secondary battery.

[0050] The preparation method provided by the present invention does not require the addition of other difficult-to-handle organic or inorganic additives during the overall coprecipitation reaction, nor does it require complex element doping treatment. The preparation method is simple to operate and is fully compatible with the production line in the prior art, which is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a SEM image of the large-particle ultra-high nickel ternary precursor prepared in Example 1;

[0052] Figure 2 This is a SEM image of the large-particle ultra-high nickel ternary precursor prepared in Comparative Example 2;

[0053] Figure 3 This is the SEM image of the large-particle ultra-high nickel ternary precursor prepared in Comparative Example 3. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below by combining the accompanying drawings and 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.

[0055] Example 1

[0056] This embodiment provides a chemical formula of Ni 0.96 Co 0.02 Mn 0.02 A large-particle ultra-high nickel ternary precursor of (OH)2 (abbreviated as NCM960202) and a preparation method thereof, which comprises the following steps:

[0057] S1. According to the chemical formula, Ni 0.96 Co 0.02 Mn 0.02 Prepare a nickel-cobalt-manganese mixed metal sulfate solution with a stoichiometric ratio of (OH)2, wherein the total metal ion concentration is 2 mol / L; prepare an ammonia solution with a mass concentration of 18%; prepare a sodium hydroxide solution with a mass concentration of 30%; mix the above sodium hydroxide solution, ammonia solution and 20L pure water to prepare a reaction base solution with a pH value of 12.0±0.1 and an ammonia solution concentration of 4±0.5g / L;

[0058] Under the protection of nitrogen atmosphere, the prepared nickel-cobalt-manganese mixed metal sulfate solution, sodium hydroxide solution and ammonia solution were added to a 50L reactor containing the reaction base liquid at a feed rate of 2.4kg / h, 1.0kg / h and 0.3kg / h respectively in a uniform and parallel flow manner to carry out the nucleation stage reaction of the coprecipitation process, wherein the pH value of the nucleation stage reaction was 12.0±0.2, and the reaction was maintained for 4h;

[0059] S2. After the nucleation stage reaction is completed, the nitrogen is switched to a mixed gas (including nitrogen and air) with a volume fraction of 3.5% of oxygen, and the feed flow rate of the sodium hydroxide solution is gradually reduced, so that the pH value of the reaction system reaches the pH value of the first growth stage reaction (11.1±0.1) in 8 hours, and when the average particle size of the particles reaches 5.0μm, the first growth stage reaction is stopped; the mixed gas of nitrogen and air is switched to nitrogen, and then the feed flow rate of the sodium hydroxide solution is gradually reduced, so that the pH value of the system gradually decreases to the pH value of the second growth stage reaction (10.2±0.1), and the reaction is continued until the average particle size of the particles reaches 12.0μm, and then the feed is stopped to obtain a large-particle ultra-high nickel ternary precursor slurry;

[0060] The large-particle ultra-high nickel ternary precursor slurry was washed with dilute sodium hydroxide solution and hot pure water three times, and then dried at 100°C for 12 hours to obtain Figure 1 For the large-particle ultra-high nickel ternary precursor shown, the reaction temperature of the entire coprecipitation reaction was maintained at 60±1° C., the stirring speed was 300 rpm, and the ammonia concentration was maintained at 4.0±0.5 g / L.

[0061] Example 2

[0062] This embodiment provides a chemical formula of Ni 0.96 Co 0.02 Mn 0.02 A large-particle ultra-high nickel ternary precursor of (OH)2 (abbreviated as NCM960202) and a preparation method thereof, which comprises the following steps:

[0063] S1. According to the chemical formula, Ni 0.96 Co 0.02 Mn 0.02 Prepare a nickel-cobalt-manganese mixed metal sulfate solution with a stoichiometric ratio of (OH)2, wherein the total metal ion concentration is 2 mol / L; prepare an ammonia solution with a mass concentration of 18%; prepare a sodium hydroxide solution with a mass concentration of 30%; mix the above sodium hydroxide solution, ammonia solution and 20L pure water to prepare a reaction base solution with a pH value of 11.7±0.1 and an ammonia solution concentration of 2±0.5g / L;

[0064] Under the protection of nitrogen atmosphere, the prepared nickel-cobalt-manganese mixed metal sulfate solution, sodium hydroxide solution and ammonia solution were added to a 50L reactor containing the reaction base liquid at a feed rate of 2.4kg / h, 1.0kg / h and 0.3kg / h respectively in a uniform and parallel flow manner to carry out the nucleation stage reaction of the coprecipitation process, wherein the pH value of the nucleation stage reaction was 11.7±0.2, and the reaction was maintained for 2h;

[0065] S2. After the nucleation stage reaction is completed, the nitrogen is switched to a mixed gas (including nitrogen and air) with a volume fraction of 2% of oxygen, and the feed flow rate of the sodium hydroxide solution is gradually reduced, so that the pH value of the reaction system reaches the pH value of the first growth stage reaction (11.0±0.1) in 8 hours. When the average particle size of the particles reaches 4μm, the first growth stage reaction is stopped; the nitrogen and air mixed gas is switched to nitrogen, and then the feed flow rate of the sodium hydroxide solution is gradually reduced to make the pH value of the system gradually decrease to the pH value of the second growth stage reaction (10.0±0.1), and the reaction is continued until the average particle size of the particles reaches 10μm, then the feed is stopped to obtain a large-particle ultra-high nickel ternary precursor slurry;

[0066] The large-particle ultra-high nickel ternary precursor slurry was washed with dilute sodium hydroxide solution three times and hot pure water three times, and then dried at 100°C for 12 hours to obtain the large-particle ultra-high nickel ternary precursor. The reaction temperature of the entire co-precipitation reaction was maintained at 50±1°C, the stirring speed was 300rpm, and the ammonia concentration was maintained at 2±0.5g / L.

[0067] Example 3

[0068] This embodiment provides a chemical formula of Ni 0.96 Co 0.02 Mn 0.02 A large-particle ultra-high nickel ternary precursor of (OH)2 (abbreviated as NCM960202) and a preparation method thereof, which comprises the following steps:

[0069] S1. According to the chemical formula, Ni 0.96 Co 0.02 Mn 0.02 Prepare a nickel-cobalt-manganese mixed metal sulfate solution with a stoichiometric ratio of (OH)2, wherein the total metal ion concentration is 2 mol / L; prepare an ammonia solution with a mass concentration of 18%; prepare a sodium hydroxide solution with a mass concentration of 30%; mix the above sodium hydroxide solution, ammonia solution and 20L pure water to prepare a reaction base solution with a pH value of 12.3±0.1 and an ammonia solution concentration of 7±0.5g / L;

[0070] Under the protection of nitrogen atmosphere, the prepared nickel-cobalt-manganese mixed metal sulfate solution, sodium hydroxide solution and ammonia solution were added to a 50L reactor containing the reaction base liquid at a feed rate of 2.4kg / h, 1.0kg / h and 0.3kg / h respectively in a uniform and parallel flow manner to carry out the nucleation stage reaction of the coprecipitation process, wherein the pH value of the nucleation stage reaction was 12.3±0.2, and the reaction was maintained for 6h;

[0071] S2. After the nucleation stage reaction is completed, the nitrogen is switched to a mixed gas (including nitrogen and air) with a volume fraction of 5% of oxygen, and the feed flow rate of the sodium hydroxide solution is gradually reduced, so that the pH value of the reaction system reaches the pH value of the first growth stage reaction (11.2±0.1) in 8 hours. When the average particle size of the particles reaches 6μm, the first growth stage reaction is stopped; the nitrogen and air mixed gas is switched to nitrogen, and then the feed flow rate of the sodium hydroxide solution is gradually reduced to make the pH value of the system gradually decrease to the pH value of the second growth stage reaction (10.4±0.1), and the reaction is continued until the average particle size of the particles reaches 14μm, then the feed is stopped to obtain a large-particle ultra-high nickel ternary precursor slurry;

[0072] The large-particle ultra-high nickel ternary precursor slurry was washed with dilute sodium hydroxide solution three times and hot pure water three times, and then dried at 100°C for 12 hours to obtain the large-particle ultra-high nickel ternary precursor. The reaction temperature of the entire co-precipitation reaction was maintained at 70±1°C, the stirring speed was 300rpm, and the ammonia concentration was maintained at 7±0.5g / L.

[0073] Example 4

[0074] This embodiment provides a chemical formula of Ni 0.85 Co 0.07 Mn 0.08 A large-particle ultra-high nickel ternary precursor of (OH)2 (abbreviated as NCM850708) and a preparation method thereof, which comprises the following steps:

[0075] S1. According to the chemical formula, Ni 0.85 Co 0.07 Mn 0.08 Prepare a mixed metal sulfate solution of nickel, cobalt and manganese in a stoichiometric ratio of (OH)2, with a total metal ion concentration of 1 mol / L; prepare an aqueous ammonia solution with a mass concentration of 18%; prepare a sodium hydroxide solution with a mass concentration of 20%; mix the above sodium hydroxide solution, aqueous ammonia solution and 20L pure water to prepare a reaction base solution with a pH value of 11.4±0.1 and an aqueous ammonia solution concentration of 4±0.5g / L;

[0076] Under the protection of nitrogen atmosphere, the prepared nickel-cobalt-manganese mixed metal sulfate solution, sodium hydroxide solution and ammonia solution were added to a 50L reactor containing the reaction base liquid at a feed rate of 2.4kg / h, 1.0kg / h and 0.3kg / h respectively in a uniform and parallel flow manner to carry out the nucleation stage reaction of the coprecipitation process, wherein the pH value of the nucleation stage reaction was 11.4, and the reaction was maintained for 6h;

[0077] S2. After the nucleation stage reaction is completed, the nitrogen is switched to a mixed gas (including nitrogen and air) with a volume fraction of 1% of oxygen, and the feed flow rate of the sodium hydroxide solution is gradually reduced, so that the pH value of the reaction system reaches the pH value of the first growth stage reaction (10.9±0.1) within 6 hours. When the average particle size of the particles reaches 3.0 μm, the first growth stage reaction is stopped; the nitrogen and air mixed gas is switched to nitrogen, and then the feed flow rate of the sodium hydroxide solution is gradually reduced, so that the pH value of the system gradually decreases to the pH value of the second growth stage reaction (9.7±0.1), and the reaction is continued until the average particle size of the particles reaches 8.0 μm, then the feed is stopped to obtain a large-particle ultra-high nickel ternary precursor slurry;

[0078] The large-particle ultra-high nickel ternary precursor slurry was washed with dilute sodium hydroxide solution three times and hot pure water three times, and then dried at 100°C for 12 hours to obtain the large-particle ultra-high nickel ternary precursor. The reaction temperature of the entire co-precipitation reaction was maintained at 55±1°C, the stirring speed was 300rpm, and the ammonia concentration was maintained at 4±0.5g / L.

[0079] Example 5

[0080] This embodiment provides a chemical formula of Ni 0.98 Co 0.01 Mn 0.01 A large-particle ultra-high nickel ternary precursor of (OH)2 (abbreviated as NCM980101) and a preparation method thereof, which comprises the following steps:

[0081] S1. According to the chemical formula, Ni 0.98 Co 0.01 Mn 0.01 Prepare a nickel-cobalt-manganese mixed metal sulfate solution with a stoichiometric ratio of (OH)2, wherein the total metal ion concentration is 3 mol / L; prepare an ammonia solution with a mass concentration of 18%; prepare a sodium hydroxide solution with a mass concentration of 40%; mix the above sodium hydroxide solution, ammonia solution and 20L pure water to prepare a reaction base solution with a pH value of 12.8±0.1 and an ammonia solution concentration of 10±0.5g / L;

[0082] Under the protection of nitrogen atmosphere, the prepared nickel-cobalt-manganese mixed metal sulfate solution, sodium hydroxide solution and ammonia solution were added to a 50L reactor containing the reaction base liquid at a feed rate of 2.4kg / h, 1.0kg / h and 0.3kg / h respectively in a uniform and parallel flow manner to carry out the nucleation stage reaction of the coprecipitation process, wherein the pH value of the nucleation stage reaction was 12.5±0.1, and the reaction was maintained for 2h;

[0083] S2. After the nucleation stage reaction is completed, the nitrogen is switched to a mixed gas (including nitrogen and air) with a volume fraction of 10% of oxygen, and the feed flow rate of the sodium hydroxide solution is gradually reduced, so that the pH value of the reaction system reaches the pH value of the first growth stage reaction (11.3±0.1) in 10 hours, and when the average particle size of the particles reaches 8.0μm, the first growth stage reaction is stopped; the nitrogen and air mixed gas is switched to nitrogen, and then the feed flow rate of the sodium hydroxide solution is gradually reduced, so that the pH value of the system gradually decreases to the pH value of the second growth stage reaction (10.2±0.1), and the reaction is continued until the average particle size of the particles reaches 18.0μm, and then the feed is stopped to obtain a large-particle ultra-high nickel ternary precursor slurry;

[0084] The large-particle ultra-high nickel ternary precursor slurry was washed with dilute sodium hydroxide solution three times and hot pure water three times, and then dried at 100°C for 12 hours to obtain the large-particle ultra-high nickel ternary precursor. The reaction temperature of the entire co-precipitation reaction was maintained at 60±1°C, the stirring speed was 300rpm, and the ammonia concentration was maintained at 10±0.5g / L.

[0085] Example 6

[0086] The difference between this embodiment and embodiment 1 is that the first growth stage reaction and the second growth stage reaction after the nucleation stage reaction in step S2 are both carried out under a nitrogen atmosphere, and the rest is the same as embodiment 1.

[0087] Example 7

[0088] The difference between this embodiment and embodiment 1 is that the first growth stage reaction and the second growth stage reaction after the nucleation stage reaction in step S2 are both carried out in a mixed gas atmosphere (including nitrogen and air) with an oxygen volume fraction of 3.5%, and the rest is the same as embodiment 1.

[0089] Example 8

[0090] The difference between this embodiment and embodiment 1 is that the first growth stage reaction after the nucleation stage reaction in step S2 is carried out in a nitrogen atmosphere, and the second growth stage reaction is carried out in a mixed gas atmosphere (including nitrogen and air) with an oxygen volume fraction of 3.5%, and the rest is the same as embodiment 1.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 1 is that the pH value of the first growth stage reaction after the nucleation stage reaction in step S2 is the same as that of the second growth stage reaction, which is 11.1±0.1, and the rest is the same as Example 1.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 1 is that the first growth stage reaction and the second growth stage reaction after the nucleation stage reaction in step S2 are both carried out under a nitrogen atmosphere, and the pH value of the second growth stage reaction after the nucleation stage reaction in step S2 is 11.1±0.1. The morphology of the prepared large-particle ultra-high nickel ternary precursor material is as follows: Figure 2 As shown, the rest are the same as in Example 1.

[0095] Comparative Example 3

[0096] The difference between this comparative example and Example 1 is that the first growth stage reaction and the second growth stage reaction after the nucleation stage reaction in step S2 are both carried out in a mixed gas atmosphere (including nitrogen and air) with a volume fraction of 3.5% oxygen, and the pH value of the second growth stage reaction after the nucleation stage reaction in step S2 is 11.1±0.1. The morphology of the prepared large-particle ultra-high nickel ternary precursor material is as follows: Figure 3 As shown, the rest are the same as in Example 1.

[0097] Comparative Example 4

[0098] The difference between this comparative example and Example 1 is that the first growth stage reaction is not carried out in step S2, that is, after the nucleation stage reaction is completed, the feed flow rate of the sodium hydroxide solution is gradually reduced under a nitrogen atmosphere, so that the pH value of the system gradually decreases to the pH value of the second growth stage reaction (10.2±0.1), and the reaction is continued until the average particle size of the particles reaches 12.0 μm, and then the feeding is stopped. The rest is the same as Example 1.

[0099] Comparative Example 5

[0100] The difference between this comparative example and Example 1 is that the second growth stage reaction is not carried out in step S2, that is, after the nucleation stage reaction is completed, the nitrogen is switched to a mixed gas (including nitrogen and air) with a volume fraction of 3.5% of oxygen, and the feed flow rate of the sodium hydroxide solution is gradually reduced so that the pH value of the reaction system reaches the pH value of the first growth stage reaction (11.1±0.1) within 8 hours. When the average particle size of the particles reaches 5.0 μm, the feeding is stopped. The rest is the same as in Example 1.

[0101] Test conditions

[0102] The large-particle ultra-high nickel ternary precursors provided in Examples 1 to 8 and Comparative Examples 1 to 5 were tested to prepare a positive electrode, and then assembled to obtain a lithium-ion battery. The specific method is as follows:

[0103] The ternary precursors provided in Examples 1 to 8 and Comparative Examples 1 to 5 were mixed with lithium carbonate at a lithiation ratio of Li:(Ni+Co+Mn)=1.02, and calcined at 750° C. for 20 h in an oxygen atmosphere to obtain a positive electrode material;

[0104] The positive electrode material, Super P and polyvinylidene fluoride are mixed in a mass ratio of 8:1:1, and the mixture is prepared with N-methylpyrrolidone solvent to obtain a positive electrode slurry, and the positive electrode slurry is scraped onto the surface of an aluminum foil, and dried to obtain a positive electrode sheet;

[0105] The positive electrode sheet, the graphite negative electrode sheet, the polypropylene separator and the electrolyte are assembled to obtain a lithium-ion battery, wherein the electrolyte is a mixed solution of 1 mol / L LiPF6+DEC / EC (volume ratio 1:1);

[0106] The cycling performance and specific capacity of the lithium-ion battery were tested at 25°C and 1C rate.

[0107] The test results are shown in Table 1:

[0108] Table 1

[0109]

[0110]

[0111] Combined with Table 1 Figure 1-Figure 3 It can be seen that Examples 1-5 of the present invention show that the dispersion and sphericity of the precursor are improved by preferably carrying out the first growth stage reaction in a micro-oxidizing atmosphere and a higher pH value, and carrying out the second growth stage reaction in an inert atmosphere and a lower pH value, so that finer primary grains can be obtained and the primary grains form a network structure of mutual cross-growth, and finally a large-particle ultrahigh nickel ternary precursor with good dispersion, good sphericity, high tap density and no cracks is obtained, so that the prepared lithium-ion battery has a higher first-cycle discharge specific capacity and good cycle stability.

[0112] Compared with Example 1, Examples 6-8 show that the reaction atmosphere of the first growth stage reaction and the second growth stage reaction has an important influence on the dispersibility and sphericity of the large-particle ultra-high nickel ternary precursor. Only the large-particle ultra-high nickel ternary precursor with good dispersibility, good sphericity, high tap density and no crack characteristics can make the prepared lithium-ion battery have better comprehensive performance.

[0113] Compared with Example 1, Comparative Example 1 shows that the present invention further reduces the pH value of the second growth stage reaction, thereby refining the primary grains and forming a network structure of cross-growth of the primary grains, ultimately improving the structural stability and conductivity of the precursor, thereby improving the cycle stability of the lithium-ion battery.

[0114] Compared with Example 1, Comparative Examples 2-3 show that only using a single reaction atmosphere and reaction pH value cannot achieve all the technical effects of the present invention, and the prepared lithium ion battery has poor overall performance.

[0115] Compared with Example 1, Comparative Examples 4-5 show that only small particles of high-nickel ternary precursor material or only large particles of high-nickel ternary precursor material are generated, and the stability and dispersibility of the precursor structure cannot be guaranteed, so that the prepared lithium-ion batteries also have poor overall performance.

[0116] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing large-particle ultra-high nickel ternary precursor, It is characterized in that The method comprises the following steps: S1. In the reaction bottom liquid, a ternary mixed metal salt solution, a precipitant solution and a complexing agent solution are introduced in parallel to carry out the nucleation stage reaction of the coprecipitation process; S2. After the nucleation stage reaction is completed, the first growth stage reaction and the second growth stage reaction are carried out in sequence to obtain the large-particle ultra-high nickel ternary precursor, wherein the pH value of the first growth stage reaction is greater than the pH value of the second growth stage reaction.

2. The method according to claim 1, It is characterized in that The reaction base solution in step S1 includes a precipitant, a complexing agent and a solvent; Preferably, the solvent comprises water; Preferably, the concentration of the complexing agent in the reaction base solution in step S1 is 1.5 to 12 g / L; Preferably, the pH value of the reaction base solution in step S1 is 11.3-12.

9.

3. The method according to claim 1 or 2, It is characterized in that The ternary mixed metal salt solution in step S1 includes a nickel-cobalt-manganese mixed metal salt solution; Preferably, the total concentration of metal ions in the ternary mixed metal salt solution in step S1 is 1.0 to 3.0 mol / L; Preferably, the mass concentration of the precipitant solution in step S1 is 20-40%; Preferably, the nucleation stage reaction in step S1 is carried out under an inert atmosphere; Preferably, the pH value of the nucleation stage reaction in step S1 is greater than the pH value of the first growth stage reaction; Preferably, the pH value of the nucleation stage reaction in step S1 is 11.4 to 12.7, preferably 11.7 to 12.3; Preferably, the reaction time of the nucleation stage in step S1 is 2 to 6 hours.

4. The method according to any one of claims 1 to 3, It is characterized in that The atmosphere of the first growth stage reaction in step S2 contains oxygen; Preferably, the volume fraction of oxygen in the atmosphere of the first growth stage reaction in step S2 is 0.5 to 10%, preferably 2 to 5%; Preferably, in step S2, the feed rate of the precipitant solution in the first growth stage reaction is lower than the feed rate of the precipitant solution in the nucleation stage reaction; Preferably, the pH value of the first growth stage reaction in step S2 is 10.8-11.4, preferably 11.0-11.

2.

5. The method according to any one of claims 1 to 4, It is characterized in that After the first growth stage reaction in step S2 is completed, the average particle size of the particles is 3 to 8 μm, preferably 4 to 6 μm.

6. The method according to any one of claims 1 to 5, It is characterized in that The second growth stage reaction in step S2 is carried out under an inert atmosphere; Preferably, in step S2, the feed rate of the precipitant solution in the second growth stage reaction is less than the feed rate of the precipitant solution in the first growth stage reaction; Preferably, the pH value of the second growth stage reaction in step S2 is 9.6 to 10.8, preferably 10.0 to 10.

4.

7. The method according to any one of claims 1 to 6, It is characterized in that The average particle size of the large-particle ultra-high nickel ternary precursor in step S2 is 6 to 18 μm, preferably 10 to 14 μm; Preferably, the chemical formula of the large-particle ultra-high nickel ternary precursor in step S2 is Ni x Co y Mn 1-x-y (OH) 2 , where 0.85≤x<1, 0.02≤y<0.15; Preferably, the water content of the large-particle ultra-high nickel ternary precursor in step S2 is not higher than 0.8wt.%.

8. A large particle ultra-high nickel ternary precursor, It is characterized in that The large-particle ultra-high nickel ternary precursor is prepared by the method for preparing a large-particle ultra-high nickel ternary precursor according to any one of claims 1-7.

9. A positive electrode, It is characterized in that The positive electrode includes a positive electrode active material, and the positive electrode active material is prepared from the large-particle ultra-high nickel ternary precursor according to claim 8.

10. A secondary battery, It is characterized in that The secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and the positive electrode includes the positive electrode according to claim 9.

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