Gradient ternary positive electrode material and preparation method thereof
By using cobalt-containing additives as nucleating agents to synthesize cobalt gradient positive electrode materials, the problems of low performance and difficult process control in the prior art are solved, higher energy density and cycle stability are achieved, and the preparation process is simplified.
Patent Information
- Application Number
- CN202411799706.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-09
- Publication Date
- 2025-03-14
AI Technical Summary
The existing gradient ternary cathode materials have low performance and difficult process control, which makes it difficult to balance energy density and cycle stability.
By using the cobalt-containing additive as the nucleating agent, the inner core is synthesized as cobalt-containing additive powder particles, the outer layer is a precursor of nickel-cobalt-manganese hydroxide, and mixed with lithium hydroxide monohydrate to prepare a cobalt gradient positive electrode material with an internal cobalt content higher than the external cobalt content.
It improves the capacity and rate performance of the material, simplifies the preparation process, reduces production costs, and makes the process more convenient to control.
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Figure CN119627077A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of battery positive electrode materials and preparation methods thereof, and in particular to a gradient ternary positive electrode material and a preparation method thereof. Background Art
[0002] The application scope of lithium-ion batteries is constantly expanding to all walks of life. The demand for lithium-ion batteries is also becoming more and more refined and the requirements are getting higher and higher. The energy density and cost of lithium-ion batteries depend to a large extent on the positive electrode. Therefore, the industry has been carrying out various improvements in positive electrode materials.
[0003] Common modification methods include element doping, surface coating and gradient ternary cathode materials. Concentration gradient structure design is one of the effective strategies to improve the structural stability of ternary layered materials. The design idea of concentration gradient structure was originally derived from core-shell structure, mainly including core-shell structure, shell concentration gradient, full concentration gradient and double tilted concentration gradient design strategies. The core idea of concentration gradient design is to use ternary layered oxides with high nickel content as inner components and stable layered oxides with low nickel content as outer components, which provide high capacity and structural stability respectively. From a design perspective, these materials can effectively solve the difficult problem of balancing high specific capacity and cycle stability by placing nickel, which provides high capacity but is unstable, mainly in the core of the particles, and manganese, which is low in capacity but chemically stable, mainly on the outside of the particles. The function of the manganese-rich outer layer is similar to that of a coating, as it minimizes the side reactions of the active material with the electrolyte, but it differs from the coating in that there are no inactive components and all materials are electrochemically active, which helps to improve capacity and conductivity. However, its preparation process is relatively difficult. The coprecipitation parameters are difficult to control during the preparation process. Ternary layered oxides with different compositions require different calcination temperatures to obtain the desired electrochemical properties, and it is difficult to accurately control the synthesis temperature. In addition, the gradient concentration design inevitably limits the nickel content in the entire ternary cathode material, thereby limiting the energy density of the battery, and the high manganese content on the particle surface is susceptible to manganese dissolution problems.
[0004] In view of this, this application is filed. Summary of the invention
[0005] The purpose of the present invention is to provide a gradient ternary positive electrode material and a preparation method thereof, by using a cobalt-containing additive as a nucleating agent to prepare a cobalt gradient positive electrode material in which the internal cobalt content is higher than the external cobalt content, so as to solve the problems of low performance and difficult process control of the gradient ternary positive electrode material in the prior art.
[0006] The present invention is achieved through the following technical solution: An embodiment of the present invention provides a gradient ternary positive electrode material, which is a cobalt gradient positive electrode material in which the internal cobalt content is higher than the external cobalt content, and the cobalt gradient positive electrode material includes NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, lithium salt and cobalt-containing additives.
[0007] The cobalt-containing additive preferably includes insoluble compounds such as cobalt tetraoxide, cobalt hydroxide, cobalt carbonate, and cobalt oxalate.
[0008] Preferably, the cobalt-containing additive is in powder form, and the particle size is 0.1-2 μm.
[0009] Preferably, the molar ratio of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O is 0.60-0.95:0.02-0.2:0.02-0.3;
[0010] The mass fraction of the raw material containing the cobalt additive is 0.1%-5%.
[0011] In order to better solve the above problems, an embodiment of the present invention further provides a method for preparing a gradient ternary positive electrode material, wherein the positive electrode material is the above positive electrode material and comprises the following steps:
[0012] S1: Using the cobalt-containing additive as a nucleating agent, a coprecipitation method is used to synthesize a core of cobalt-containing additive powder particles and an outer layer of nickel-cobalt-manganese hydroxide precursor;
[0013] S2: Mixing the precursor with lithium hydroxide monohydrate and sintering them to obtain a cobalt gradient positive electrode material in which the internal cobalt content is higher than the external cobalt content.
[0014] Preferably, S1 includes first preparing NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O into a mixed solution, introducing the mixed solution into a reactor for reaction, continuously adding cobalt-containing additive powder within a period of 1 to 40 minutes after the start of the reaction, and then continuing the reaction for 12 to 50 hours. After the reaction is completed, washing and drying are performed once to obtain a precursor with a core of cobalt-containing additive particles and an outer layer of nickel-cobalt-manganese hydroxide.
[0015] Preferably, before the cobalt-containing additive powder is added to the reactor, NaOH solution and NH 3 ·H 2 O solution are also added to the reactor to react with the mixed solution.
[0016] Preferably, before the cobalt-containing additive powder is added into the reactor, the reaction pH of the mixed solution in the reactor is 10.8 to 11.8.
[0017] Preferably, after the cobalt-containing additive powder is added to the reactor, the reaction temperature in the reactor is 50-60°C.
[0018] Preferably, the mass ratio of the precursor to lithium hydroxide monohydrate in S2 is 1.45 to 1.6:1.
[0019] Preferably, the sintering temperature is 750-830° C., and the sintering time is 10-14 hours.
[0020] Compared with the prior art, the embodiments of the present invention have the following advantages and beneficial effects:
[0021] 1. In the embodiment of the present invention, a cobalt-containing additive is used as a ternary precursor to prepare a nucleating agent, which not only facilitates the migration and release of lithium ions inside the positive electrode material, but also improves the material capacity and rate performance under high rate and high current of a large-particle ternary positive electrode.
[0022] 2. In the embodiment of the present invention, the cobalt-containing additive is used as the ternary precursor to prepare the nucleating agent, which can avoid the preparation process of the ternary precursor nucleation stage, shorten the preparation process flow, and reduce the production cost.
[0023] 3. Compared with the preparation of traditional gradient ternary positive electrode materials, the embodiments of the present invention are easier to control and simpler, and avoid the frequent adjustment of process parameters in the preparation process of traditional gradient ternary precursors. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:
[0025] Figure 1 This is a SEM image of the sample provided in Example 1 of the present invention;
[0026] Figure 2 This is the XRD diagram of the sample provided in Example 1 of the present invention. DETAILED DESCRIPTION
[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.
[0028] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0029] The present invention provides a method for preparing a gradient ternary cathode material, comprising the following steps:
[0030] S1: Using the cobalt-containing additive as a nucleating agent, a coprecipitation method is used to synthesize a core of cobalt-containing additive powder particles and an outer layer of nickel-cobalt-manganese hydroxide precursor;
[0031] Specifically, the steps include firstly preparing NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O into a mixed solution, introducing the mixed solution into a reactor for reaction, continuously adding cobalt-containing additive powder within a period of 1 to 40 minutes after the reaction starts, and then continuing the reaction for 12 to 50 hours, and washing and drying once after the reaction ends to obtain a precursor with a core of cobalt-containing additive particles and an outer layer of nickel-cobalt-manganese hydroxide;
[0032] At the same time, before the cobalt-containing additive powder is added to the reactor, NaOH solution and NH3·H2O solution are also added to the reactor to react with the mixed solution;
[0033] Before the cobalt-containing additive powder is added to the reactor, the reaction pH of the mixed solution in the reactor is 10.8 to 11.8;
[0034] After the cobalt-containing additive powder is added into the reactor, the reaction temperature in the reactor is 50-60°C.
[0035] S2: mixing the precursor with lithium hydroxide monohydrate and sintering to obtain a cobalt gradient positive electrode material having an internal cobalt content higher than an external cobalt content;
[0036] The mass ratio of the precursor to lithium hydroxide monohydrate is 2.0 to 2.5:1;
[0037] The sintering temperature is 750-830° C., and the sintering time is 10-14 hours.
[0038] Example 1
[0039] The embodiment of the present invention provides a method for preparing a gradient ternary cathode material, comprising the following steps:
[0040] (1) Using 0.5% cobalt tetraoxide (particle size 0.5 μm) as a nucleating agent, a coprecipitation method was used to synthesize particles with a core of cobalt tetraoxide and an outer layer of Ni 0.83Co 0.12 Mn 0.05 (OH)2 precursor, first mix NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of 0.83:0.12:0.05 to obtain a 2M mixed solution, which is pumped into a 2L tank reactor. At the same time, pour in 1M NaOH solution and 3M NH3·H2O, control the pH at around 11.2, and continuously add cobalt tetroxide powder within 30 minutes of the start of the reaction, and then continue the reaction for 40 hours. Stir the solution evenly at 55°C to allow it to react fully, then wash it with deionized water several times until the pH is neutral to obtain the hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2. Figure 1 The cross-section of the precursor was tested by EDS, and the average value of 8 inner points was selected, in which the cobalt content accounted for 12.48% of the nickel-cobalt-manganese content, while the average value of 9 outer points was selected, in which the cobalt content accounted for 12.01% of the nickel-cobalt-manganese content.
[0041] (2) 500 g of the hydroxide precursor obtained above and 245 g of lithium hydroxide monohydrate were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, and sintered at 790°C in a preheated tube furnace for 12 h. Oxygen was passed throughout the sintering process, and the gas flow rate was controlled at about 1 L / min. After naturally cooling to room temperature, the sample was taken out and sieved with a 300-mesh sieve to obtain a gradient positive electrode material. Figure 2 It can be seen that the ternary gradient positive electrode material has a good structure and the synthesis results are good.
[0042] Example 2
[0043] The embodiment of the present invention provides a method for preparing a gradient ternary cathode material, comprising the following steps:
[0044] (1) Using cobalt hydroxide (0.5 μm in particle size) as a nucleating agent, a coprecipitation method was used to synthesize particles with a core of cobalt tetroxide and a Ni outer layer. 0.83 Co 0.12 Mn 0.05(OH)2 precursor, first mix NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of 0.83:0.12:0.05 to obtain a 2M mixed solution, which is pumped into a 2L tank reactor. At the same time, pour in 1M NaOH solution and 3M NH3·H2O, control the pH at around 11.2, and continuously add cobalt hydroxide powder within 30 minutes of the start of the reaction, and then continue the reaction for 40 hours. Stir the solution evenly at 55°C to allow it to react fully, then wash it with deionized water several times until the pH is neutral to obtain the hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2.
[0045] (2) 500 g of the hydroxide precursor obtained above and 245 g of lithium hydroxide monohydrate were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, and sintered at 790° C. in a preheated tube furnace for 12 h. Oxygen was passed throughout the sintering process, and the gas flow rate was controlled at about 1 L / min. After naturally cooling to room temperature, the sample was taken out and sieved with a 300-mesh sieve to obtain a gradient positive electrode material.
[0046] Example 3
[0047] The embodiment of the present invention provides a method for preparing a gradient ternary cathode material, comprising the following steps:
[0048] (1) Using 0.5% cobalt tetroxide (particle size 2 μm) as a nucleating agent, a coprecipitation method was used to synthesize particles with a core of cobalt tetroxide and an outer layer of Ni 0.83 Co 0.12 Mn 0.05 (OH)2 precursor, first mix NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of 0.80:0.15:0.07 to obtain a 2M mixed solution, which is pumped into a 2L tank reactor. At the same time, pour in 1M NaOH solution and 3M NH3·H2O, control the pH at around 11.2, and continuously add cobalt tetroxide powder within 30 minutes of the start of the reaction, and then continue the reaction for 40 hours. Stir the solution evenly at 55°C to allow it to react fully, then wash it with deionized water several times until the pH is neutral to obtain the hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2.
[0049] (2) 500 g of the hydroxide precursor obtained above and 245 g of lithium hydroxide monohydrate were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, and sintered at 790° C. in a preheated tube furnace for 12 h. Oxygen was passed throughout the sintering process, and the gas flow rate was controlled at about 1 L / min. After naturally cooling to room temperature, the sample was taken out and sieved with a 300-mesh sieve to obtain a gradient positive electrode material.
[0050] Example 4
[0051] The embodiment of the present invention provides a method for preparing a gradient ternary cathode material, comprising the following steps:
[0052] (1) Using 0.5% cobalt tetraoxide (particle size 0.5 μm) as a nucleating agent, a coprecipitation method was used to synthesize particles with a core of cobalt tetraoxide and an outer layer of Ni 0.83 Co 0.12 Mn 0.05 (OH)2 precursor, first mix NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of 0.70:0.10:0.2 to obtain a 2M mixed solution, which is pumped into a 2L tank reactor. At the same time, pour in 1M NaOH solution and 3M NH3·H2O, control the pH at around 11.2, and continuously add cobalt tetroxide powder within 30 minutes of the start of the reaction, and then continue the reaction for 40 hours. Stir the solution evenly at 55°C to allow it to react fully, then wash it with deionized water several times until the pH is neutral to obtain the hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2.
[0053] (2) 500 g of the hydroxide precursor obtained above and 245 g of lithium hydroxide monohydrate were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, and sintered at 810° C. in a preheated tube furnace for 12 h. Oxygen was passed throughout the sintering process, and the gas flow rate was controlled at about 1 L / min. After naturally cooling to room temperature, the sample was taken out and sieved with a 300-mesh sieve to obtain a gradient positive electrode material.
[0054] Example 5
[0055] The embodiment of the present invention provides a method for preparing a gradient ternary cathode material, comprising the following steps:
[0056] (1) Using cobalt tetroxide (particle size 1 μm) as a nucleating agent, a coprecipitation method was used to synthesize particles with a core of cobalt tetroxide and an outer layer of Ni 0.83 Co0.12 Mn 0.05 (OH)2 precursor, first mix NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of 0.83:0.12:0.05 to obtain a 2M mixed solution, which is pumped into a 2L tank reactor. At the same time, pour in 1M NaOH solution and 3M NH3·H2O, control the pH at around 11.2, and continuously add cobalt tetroxide powder within 30 minutes of the start of the reaction, and then continue the reaction for 40 hours. Stir the solution evenly at 55°C to allow it to react fully, then wash it with deionized water several times until the pH is neutral to obtain the hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2.
[0057] (2) 500 g of the hydroxide precursor obtained above and 245 g of lithium hydroxide monohydrate were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, and sintered at 790° C. in a preheated tube furnace for 12 h. Oxygen was passed throughout the sintering process, and the gas flow rate was controlled at about 1 L / min. After naturally cooling to room temperature, the sample was taken out and sieved with a 300-mesh sieve to obtain a gradient positive electrode material.
[0058] Example 6
[0059] The embodiment of the present invention provides a method for preparing a gradient ternary cathode material, comprising the following steps:
[0060] (1) Using cobalt tetroxide (particle size 0.5 μm) as a nucleating agent, a coprecipitation method was used to synthesize particles with a core of cobalt tetroxide and an outer layer of Ni 0.83 Co 0.12 Mn 0.05 (OH)2 precursor, first mix NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of 0.83:0.12:0.05 to obtain a 2M mixed solution, which is pumped into a 2L tank reactor. At the same time, pour in 1M NaOH solution and 3M NH3·H2O, control the pH at around 11.2, and continuously add cobalt tetroxide powder within 30 minutes of the start of the reaction, and then continue the reaction for 40 hours. Stir the solution evenly at 55°C to allow it to react fully, then wash it with deionized water several times until the pH is neutral to obtain the hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2.
[0061] (2) 500 g of the hydroxide precursor obtained above and 245 g of lithium hydroxide monohydrate were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, and sintered at 790° C. in a preheated tube furnace for 12 h. Oxygen was passed throughout the sintering process, and the gas flow rate was controlled at about 1 L / min. After naturally cooling to room temperature, the sample was taken out and sieved with a 300-mesh sieve to obtain a gradient positive electrode material.
[0062] Example 7
[0063] The embodiment of the present invention provides a method for preparing a gradient ternary cathode material, comprising the following steps:
[0064] (1) Using 0.5% cobalt tetraoxide (particle size 0.09 μm) as a nucleating agent, a coprecipitation method was used to synthesize particles with a core of cobalt tetraoxide and an outer layer of Ni 0.83 Co 0.12 Mn 0.05 (OH)2 precursor, first mix NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of 0.83:0.12:0.05 to obtain a 2M mixed solution, which is pumped into a 2L tank reactor. At the same time, pour in 1M NaOH solution and 3M NH3·H2O, control the pH at around 11.2, and continuously add cobalt tetroxide powder within 30 minutes of the start of the reaction, and then continue the reaction for 40 hours. Stir the solution evenly at 55°C to allow it to react fully, then wash it with deionized water several times until the pH is neutral to obtain the hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2.
[0065] (2) 500 g of the hydroxide precursor obtained above and 245 g of lithium hydroxide monohydrate were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, and sintered at 790° C. in a preheated tube furnace for 12 h. Oxygen was passed throughout the sintering process, and the gas flow rate was controlled at about 1 L / min. After naturally cooling to room temperature, the sample was taken out and sieved with a 300-mesh sieve to obtain a gradient positive electrode material.
[0066] Example 8
[0067] The embodiment of the present invention provides a method for preparing a gradient ternary cathode material, comprising the following steps:
[0068] (1) Using 0.5% cobalt tetraoxide (particle size 2.5 μm) as a nucleating agent, a coprecipitation method was used to synthesize particles with a core of cobalt tetraoxide and an outer layer of Ni 0.83 Co0.12 Mn 0.05 (OH)2 precursor, first mix NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of 0.83:0.12:0.05 to obtain a 2M mixed solution, which is pumped into a 2L tank reactor. At the same time, pour in 1M NaOH solution and 3M NH3·H2O, control the pH at around 11.2, and continuously add cobalt tetroxide powder within 30 minutes of the start of the reaction, and then continue the reaction for 40 hours. Stir the solution evenly at 55°C to allow it to react fully, then wash it with deionized water several times until the pH is neutral to obtain the hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2.
[0069] (2) 500 g of the hydroxide precursor obtained above and 245 g of lithium hydroxide monohydrate were fully mixed with a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, and sintered at 790° C. in a preheated tube furnace for 12 h. Oxygen was passed throughout the sintering process, and the gas flow rate was controlled at about 1 L / min. After naturally cooling to room temperature, the sample was taken out and sieved with a 300-mesh sieve to obtain a gradient positive electrode material.
[0070] Comparative Example 1
[0071] A method for preparing a ternary positive electrode material is provided, comprising the following steps:
[0072] (1) Synthesis of Ni using coprecipitation method 0.83 Co 0.12 Mn 0.05 (OH)2 precursor, first mix NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of 0.83:0.12:0.05 to obtain a 2M mixed solution, which is pumped into a 2L tank reactor. At the same time, pour in 1M NaOH solution and 3M NH3·H2O, first control the pH to about 12 to facilitate the rapid generation of precursor nuclei, and after half an hour, lower the pH to about 11.2 to facilitate the growth of the precursor. Stir the solution evenly at 55°C to allow it to react fully, then wash it with deionized water several times until the pH is neutral to obtain the hydroxide precursor Ni 0.83 Co 0.12 Mn 0.05 (OH)2.
[0073] (2) 500 g of the hydroxide precursor obtained above and 245 g of lithium hydroxide monohydrate were fully mixed using a high-speed mixer, sieved and mixed again to obtain a uniform mixture without white spots, placed in a clean sagger, and sintered at 790° C. in a preheated tube furnace for 12 h. Oxygen was passed throughout the sintering process, and the gas flow rate was controlled at about 1 L / min. After naturally cooling to room temperature, the sample was taken out and sieved using a 300-mesh sieve to obtain a positive electrode material.
[0074] Test: The positive electrode materials prepared in Examples 1-6 and Comparative Example 1 were respectively prepared into button batteries, and charge and discharge tests were performed at voltages of 3.0 to 4.3 V at rates of 0.1C, 0.2C, 0.33C, 0.5C and 1C, respectively. The discharge specific capacity test results are shown in Table 1 below, and the first charge and discharge efficiency test results are shown in Table 2:
[0075] Table 1
[0076]
[0077] Table 2
[0078]
[0079] Conclusion, as shown in Table 1 and Table 2, the first charge and discharge efficiency and discharge specific capacity of the positive electrode material prepared by the embodiment of the present invention are improved compared with the positive electrode material prepared by the conventional preparation method of Comparative Example 1. A gradient ternary positive electrode material with more internal cobalt content and less external cobalt content is prepared, which can facilitate the migration and escape of lithium ions inside the positive electrode material. In the high-rate and high-current environment of the large-particle ternary positive electrode, the material capacity and rate performance can be improved. By comparing Example 7 and Example 8 with Example 1, it can be seen that the particle size of the cobalt-containing additive powder is preferably 0.1 ~2μm, when the powder particle size is small, the powder is easy to agglomerate, which is not conducive to dispersion as a nucleating agent; when the powder particles are large, they cannot act as a nucleating agent, and the precursor is not easy to grow on them. By comparing Example 5 and Example 6 with Example 1, it can be seen that the amount of cobalt-containing additive powder cannot be too high by 5% and too low by 0.1%. Adding too much will result in too much nucleating agent, which is not conducive to the growth of the precursor; adding too little will result in too little nucleating agent, which is not conducive to the generation of more bodies, and the content of cobalt-containing additive in the generated precursor is also less.
[0080] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A gradient ternary cathode material, characterized in that: The positive electrode material is a cobalt gradient positive electrode material in which the internal cobalt content is higher than the external cobalt content. The cobalt gradient positive electrode material is made of NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, lithium salt and cobalt-containing additives.
2. A gradient ternary cathode material according to claim 1, characterized in that: The cobalt-containing additive is in powder form, and the particle size is 0.1-2 μm.
3. A gradient ternary cathode material according to claim 2, characterized in that: The molar ratio of NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O is 0.60-0.95:0.02-0.2:0.02-0.3; The mass fraction of the raw material containing the cobalt additive is 0.1%-5%.
4. A method for preparing a gradient ternary positive electrode material, wherein the positive electrode material is the positive electrode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: Using the cobalt-containing additive as a nucleating agent, a coprecipitation method is used to synthesize a core of cobalt-containing additive powder particles and an outer layer of nickel-cobalt-manganese hydroxide precursor; S2: Mixing the precursor with lithium hydroxide monohydrate and sintering them to obtain a cobalt gradient positive electrode material in which the internal cobalt content is higher than the external cobalt content.
5. The method for preparing a gradient ternary cathode material according to claim 4, characterized in that: S1 includes first preparing NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O into a mixed solution, introducing the mixed solution into a reactor for reaction, continuously adding cobalt-containing additive powder within 1 to 40 minutes after the reaction starts, and then continuing the reaction for 12 to 50 hours. After the reaction is completed, washing and drying are performed once to obtain a precursor with a core of cobalt-containing additive particles and an outer layer of nickel-cobalt-manganese hydroxide.
6. The method for preparing a gradient ternary cathode material according to claim 5, characterized in that: Before the cobalt-containing additive powder is added into the reactor, NaOH solution and NH3·H2O solution are also added into the reactor to react with the mixed solution.
7. The method for preparing a gradient ternary cathode material according to claim 6, characterized in that: Before the cobalt-containing additive powder is added into the reactor, the reaction pH of the mixed solution in the reactor is 10.8-11.
8.
8. The method for preparing a gradient ternary cathode material according to claim 7, characterized in that: After the cobalt-containing additive powder is added into the reactor, the reaction temperature in the reactor is 50-60°C.
9. The method for preparing a gradient ternary cathode material according to claim 4, characterized in that: The mass ratio of the precursor to lithium hydroxide monohydrate in S2 is 2.0 to 2.5:
1.
10. The method for preparing a gradient ternary cathode material according to claim 9, characterized in that: The sintering temperature is 750-830° C., and the sintering time is 10-14 hours.