A high-nickel ternary precursor with a structure of different particle size and concentration gradient and a preparation method thereof

Abstract

The present invention discloses a high-nickel ternary precursor with different particle scales and concentration gradient structures and a preparation method thereof. The chemical formula of the high-nickel ternary precursor is Ni x Co y Mn z (OH)2, where 0.8 ≤ x < 1, 0 < y < 0.2, 0 < z < 0.2, and x + y + z = 1. The preparation method is to gradually increase the Mn 2+ concentration and gradually decrease the Ni 2+ concentration during the reaction process, while the Co 2+ concentration remains relatively stable, thereby controlling the gradient distribution of the precipitation particles. The obtained high-nickel ternary precursor has a gradient change in nickel element content from high to low from the core to the shell, the cobalt element content remains basically unchanged, the manganese element content has a gradient change from low to high from the core to the shell, and has different particle scales, which can effectively improve the discharge specific capacity, cycle life and storage performance of its high-nickel ternary cathode material. This method has a simple process, is easy to operate, and is easy to realize industrial production. Moreover, the production process is pollution-free and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of high-nickel ternary material preparation technology for lithium-ion batteries, and particularly to a high-nickel ternary precursor with different particle size and concentration gradient structures and its preparation method. Background Technology

[0002] With the rapid development of the global new energy vehicle industry, increasingly higher requirements have been placed on the performance (such as energy density, rate performance, cycle life, safety performance, etc.) and cost of lithium-ion power batteries. Lithium-ion power battery products are increasingly developing towards higher capacity, lighter weight, better rate performance, cycle performance and safety performance, and lower cost, especially high energy density and low cost.

[0003] With the increasing demands for high energy density and low cost in lithium-ion power batteries, nickel-cobalt-manganese ternary cathode materials are continuously developing towards higher nickel content and lower cobalt content. The performance of high-nickel ternary cathode materials largely depends on the structure, size, and morphology of the particles. However, as the nickel content increases and the cobalt content decreases, the structural stability and safety of the cathode material deteriorate. For cathode materials with a nickel molar content exceeding 80%, the alkaline surface resulting from the high nickel content makes them more susceptible to reacting with CO2 and H2O in the air to form Li2CO3, or reacting with the electrolyte to produce byproducts such as HF. All these problems severely hinder their storage, stable electrochemical performance, and commercial application. Furthermore, the particle size of the ternary precursor also determines the particle size of the sintered ternary cathode material. The small particle size of ternary cathode materials results in a short lithium-ion diffusion path, low relative internal resistance, low self-polarization, high safety performance, and good rate performance. However, the small particle size also leads to higher surface energy, easier particle agglomeration, uneven mixing, and increased susceptibility to side reactions. Furthermore, the relatively large specific surface area of ​​small particles can easily cause surface-related adverse effects. Therefore, effectively controlling the surface nickel content and particle size of high-nickel ternary cathode materials to improve their stability and ultimately enhance their electrochemical performance is a current focus and hot topic in the industry.

[0004] In recent years, researchers have done a lot of work, including element doping, surface coating and core-shell structure, to improve the structural stability of high-nickel ternary cathode materials, thereby improving their electrochemical performance. These efforts have had some effect, but they cannot fundamentally solve the problems of stress-induced cracking and irreversible phase transitions within the particles. Summary of the Invention

[0005] The object of the present invention is to provide a high-nickel ternary precursor with different particle sizes and concentration gradient structures, and a preparation method thereof, so as to achieve a gradient change in the nickel element content from high to low from the core to the shell (along the center to the outer surface), the cobalt element content remains unchanged, the manganese element content changes from low to high from the core to the shell (along the center to the outer surface), and effective control of different particle sizes, thereby improving the electrochemical performance stability of the high-nickel ternary cathode material.

[0006] To achieve this object, the present invention adopts the following technical solutions: A high-nickel ternary precursor with different particle sizes and concentration gradient structures provided by the present invention has the chemical formula Ni x Co y Mn z (OH)2, where 0.8 ≤ x < 1, 0 < y < 0.2, 0 < z < 0.2, and x + y + z = 1.

[0007] The preparation method of the above-mentioned high-nickel ternary precursor with different particle sizes and concentration gradient structures includes the following steps: Step 1: Solution preparation; (1) Prepare a mixed solution of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O as solution A, where the molar fraction of manganese element is 0 < Mn < 5%; (2) Prepare a MnSO4·H2O solution as solution B, and the molar concentration of the solution is 0 < Mn < 0.4 mol / L; (3) Prepare a 6 - 11 mol / L sodium hydroxide solution as solution C; (4) Prepare a 1 - 3 mol / L ammonium sulfate complexing agent solution as solution D; Step 2: Add solution C, solution D, and pure water to a closed reaction kettle with an inert gas protection atmosphere to prepare a reaction bottom liquid with a pH of 11.00 - 12.50, and the concentration of ammonium sulfate in the reaction bottom liquid is 0.1 - 0.5 mol / L; Step 3: Keep the stirring of the reaction kettle on, and add solution A, solution C, and solution D in step 1 to the reaction kettle at a flow rate of 2 - 15 mL / min respectively for coprecipitation reaction. Control the pH value of the reaction kettle to be 10.90 - 12.40. At the beginning of the reaction, add solution B to solution A, and stop feeding when the particles grow to the target particle size to obtain a coprecipitation reaction product; Step 4: Centrifugally separate, wash, and dry the coprecipitation reaction product in step 3 to obtain the gradient structure high-nickel ternary precursor.

[0008] As a further improvement to the technical solution of the present invention, in step one (1), the mixing ratio of NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O is 95:4:1 ~ 85:10:5.

[0009] Furthermore, in step one, the total concentration of solution A is 1~3 mol / L.

[0010] Furthermore, in step two, the protective atmosphere in the reactor is nitrogen or argon.

[0011] Furthermore, in step two, the temperature of the base liquid is 45~60℃.

[0012] Furthermore, in step three, the reaction temperature is 45~60℃.

[0013] Furthermore, in step three, the ammonia concentration in the reactor is 0.20~0.50 mol / L.

[0014] Furthermore, in step three, the flow rate of solution B is 0.5~3 mL / min.

[0015] Furthermore, in step four, the D of the gradient structure high-nickel ternary precursor... 50 The micrometer diameter is 3–15 μm, and the tap density is 1.8–2.2 g / cm³. 3 Particle size distribution 0.6 < (D 90 -D 10 ) / D 50 <0.9, specific surface area is 3~15 m² 2 / g.

[0016] By adopting the above technical solution, the beneficial effects of the present invention are as follows: This invention provides a method for preparing high-nickel ternary precursors with different particle sizes and concentration gradients, by gradually increasing the Mn concentration during the reaction process. 2+ Concentration, and gradually decrease Ni 2+ Concentration, Co 2+ By maintaining a relatively stable concentration and thus controlling the gradient distribution of the precipitated particles, a gradient structure can be achieved in the high-nickel ternary precursor where the nickel content decreases from the core to the shell (from the center to the outer surface), the cobalt content remains essentially constant, and the manganese content increases from the core to the shell (from the center to the outer surface), with different particle sizes. This effectively improves the electrochemical stability of the high-nickel ternary cathode material. The method is simple, easy to operate, and readily scalable for industrial production. Furthermore, the production process is pollution-free and environmentally friendly. Attached Figure Description

[0017] Figure 1 Ni gradient structure in Example 10.8 Co 0.1 Mn 0.1 SEM image of (OH)2 precursor; Figure 2 Ni gradient structure in Example 1 0.8 Co 0.1 Mn 0.1 Particle size and particle size distribution of (OH)2 precursor; Figure 3 Ni gradient structure in Example 2 0.85 Co 0.05 Mn 0.1 SEM image of (OH)2 precursor; Figure 4 Ni gradient structure in Example 2 0.85 Co 0.05 Mn 0.1 XRD pattern of (OH)2 precursor; Figure 5 Ni gradient structure in Example 2 0.85 Co 0.05 Mn 0.1 Particle size and particle size distribution of (OH)2 precursor; Figure 6 Example 3: Gradient Structure Ni 0.9 Co 0.05 Mn 0.05 SEM image of (OH)2 precursor; Figure 7 Example 3: Gradient Structure Ni 0.9 Co 0.05 Mn 0.05 Particle size and particle size distribution of (OH)2 precursor; Figure 8 Example 4: Gradient Structure Ni 0.94 Co 0.02 Mn 0.04 SEM image of (OH)2 precursor; Figure 9 Example 4: Gradient Structure Ni 0.94 Co 0.02 Mn 0.04 (OH)2 precursor particle size and particle size distribution diagram; Figure 10 Example 4: Gradient structure LiNi 0.94 Co 0.02 Mn 0.04 A schematic diagram of the initial discharge specific capacity of the O2 cathode material. Detailed Implementation

[0018] To better understand the present invention, the following embodiments further illustrate its content; however, the scope of protection of the present invention is not limited to the embodiments described below. Numerous specific details are set forth in the following description to provide a more thorough understanding of the present invention. However, those skilled in the art will recognize that the present invention can be practiced without one or more of these details. In other instances, some technical features well-known in the art have not been described to avoid confusion with the present invention.

[0019] Example 1 This implementation provides a gradient structure high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 Methods for preparing (OH)2 include: Step 1: Prepare a mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate, designated solution A. The molar ratio of Ni, Co, and Mn in solution A is 86:11.5:2.5, and the total molar concentration of Ni, Co, and Mn is 1.85 mol / L. Prepare a manganese sulfate solution, designated solution B, with a manganese sulfate molar concentration of 0.15 mol / L.

[0020] Prepare a 10 mol / L sodium hydroxide precipitant solution as solution C.

[0021] Prepare a complexing agent solution of 1.4 mol / L ammonium sulfate solution, known as solution D.

[0022] Step 2: Add solution C, solution D, and pure water to a sealed reaction vessel with a nitrogen protective atmosphere and an effective volume of 5L to prepare a reaction base solution. The pH value of the base solution is controlled at 11.80, the reaction temperature is maintained at 50℃, and the concentration of ammonium sulfate in the base solution is controlled at 0.30 mol / L.

[0023] Step 3: Keep the reactor stirred (stirring intensity 40Hz), and continuously add solutions A, C and D from step 1 to the reactor at a flow rate of 3 mL / min to carry out the co-precipitation reaction. At the beginning of the reaction, solution B is continuously added to solution A at a flow rate of 1 mL / min. The reaction is carried out for 75 hours until the particles grow to 10 μm, at which point the liquid feeding is stopped.

[0024] The pH value was maintained at 11.65 and the reaction temperature was maintained at 50 ℃ during the reaction process. The ammonia concentration in the slurry in the reactor was maintained at 0.25 mol / L.

[0025] Step 4: The coprecipitation reaction product from Step 3 is separated by centrifugation and washed until SO4 is reached. 2- Washing was stopped when the concentration was ≤0.30%, and the sample was dried at 110℃ for 12 hours to obtain a gradient structure high-nickel ternary precursor with the chemical formula Ni. 0.8Co 0.1 Mn 0.1 (OH)2, from Figure 1 The SEM image shows that the particles are spherical; from Figure 2 It can be seen that D 50 The particle size is 10.135 μm, the particle size distribution is 0.6396, and the tap density is 2.18 g / cm³. 3 Its specific surface area is 6.26 m². 2 / g.

[0026] Example 2 This implementation provides a gradient structure high-nickel ternary precursor Ni 0.85 Co 0.05 Mn 0.10 Methods for preparing (OH)2 include: Step 1: Prepare a mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate, designated solution A. The molar ratio of Ni, Co, and Mn in solution A is 93.5:5:1.5, and the total molar concentration of Ni, Co, and Mn is 1.80 mol / L. Prepare a manganese sulfate solution, designated solution B, with a manganese sulfate molar concentration of 0.20 mol / L.

[0027] Prepare a 10.5 mol / L sodium hydroxide precipitant solution as solution C.

[0028] Prepare a complexing agent solution of 1.4 mol / L ammonium sulfate solution, known as solution D.

[0029] Step 2: Add solution C, solution D and pure water to a sealed reactor with an argon protective atmosphere and an effective volume of 30L to prepare a reaction base solution. The pH value of the base solution is controlled at 12.0, the reaction temperature is maintained at 51 ℃, and the concentration of ammonium sulfate in the base solution is controlled at 0.45 mol / L.

[0030] Step 3: Keep the reactor stirred (stirring speed 45 Hz), and continuously add solutions A, C and D from step 1 to the reactor at a flow rate of 10 mL / min to carry out the co-precipitation reaction. At the beginning of the reaction, solution B is continuously added to solution A at a flow rate of 2 mL / min. The reaction is carried out for 22 h until the particles grow to 4.5 μm, at which point the liquid feeding is stopped.

[0031] The pH value was maintained at 11.90 and the reaction temperature was maintained at 50 ℃ during the reaction process. The ammonia concentration in the slurry in the reactor was 0.35 mol / L.

[0032] Step 4: The coprecipitation reaction product from Step 3 is separated by centrifugation and washed until SO4 is reached. 2-Washing was stopped when the concentration was ≤0.30%, and the sample was dried at 100℃ for 12 hours to obtain a gradient structure high-nickel ternary precursor with the chemical formula Ni. 0.85 Co 0.05 Mn 0.10 (OH)2; from Figure 3 The SEM images show that the particles are spherical or near-spherical; from Figure 4 It can be seen that the granular crystal structure is a pure β-Ni(OH)2 phase; from Figure 5 It can be seen that D 50 The particle size was 4.76 μm, the particle size distribution was 0.7817, and the tap density was 2.12 g / cm³. 3 The specific surface area is 8.16 m². 2 / g.

[0033] Example 3 This implementation provides a gradient structure high-nickel ternary precursor Ni 0.90 Co 0.05 Mn 0.05 Methods for preparing (OH)2 include: Step 1: Prepare a mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate (solution A). The molar ratio of Ni, Co, and Mn in solution A is 90:11.5:2.5, and the total molar concentration of Ni, Co, and Mn is 1.9 mol / L. Prepare a manganese sulfate solution (solution B). The molar concentration of manganese sulfate in solution B is 0.10 mol / L.

[0034] Prepare a 10.88 mol / L sodium hydroxide precipitant solution as solution C.

[0035] Prepare a 1.5 mol / L ammonia solution complexing agent solution as solution D.

[0036] Step 2: Add solution C, solution D and pure water to a sealed reaction vessel with a nitrogen protective atmosphere and an effective volume of 30L to prepare a reaction base solution. The pH value of the base solution is controlled at 12.10~12.20, the reaction temperature is maintained at 49 ± 0.5 ℃, and the concentration of ammonium sulfate in the base solution is controlled at 0.40 mol / L.

[0037] Step 3: Keep the reactor stirred (stirring speed 40 Hz), and continuously add solutions A, C and D from step 1 to the reactor at a flow rate of 8 mL / min to carry out the co-precipitation reaction. At the beginning of the reaction, solution B is continuously added to solution A at a flow rate of 2.0 mL / min. The reaction is carried out for 90 h until the particles grow to 13.5 μm, at which point the liquid feeding is stopped.

[0038] The pH value was maintained at 12.10 and the reaction temperature was maintained at 49 ℃ during the reaction process. The ammonia concentration in the slurry in the reactor was 0.35 mol / L.

[0039] Step 4: The coprecipitation reaction product from Step 3 is separated by centrifugation and washed until SO4 is reached. 2- Washing was stopped when the concentration was ≤0.30%, and the sample was dried at 100℃ for 12 hours to obtain a high-nickel ternary precursor with a gradient structure and the chemical formula Ni. 0.90 Co 0.05 Mn 0.05 (OH)2, from Figure 6 The SEM images show that the particles are spherical or near-spherical; from Figure 7 It can be seen that D 50 The particle size was 9.627 μm, the particle size distribution was 0.6337, and the tap density was 2.20 g / cm³. 3 Its specific surface area is 6.11 m². 2 / g.

[0040] Example 4 A method for preparing a gradient-structured high-nickel ternary precursor includes: Step 1: Prepare a mixed solution of nickel sulfate, cobalt sulfate, and manganese sulfate (solution A). The molar ratio of Ni, Co, and Mn in solution A is 95:4.5:0.5, and the total molar concentration of Ni, Co, and Mn is 1.96 mol / L. Prepare a manganese sulfate solution (solution B). The molar concentration of manganese sulfate in solution B is 0.04 mol / L.

[0041] Prepare a 10 mol / L sodium hydroxide precipitant solution as solution C.

[0042] Prepare a 1.4 mol / L ammonia solution complexing agent solution as solution D.

[0043] Step 2: Add solution C, solution D and pure water to a sealed reaction vessel with a nitrogen protective atmosphere and an effective volume of 30L to prepare a reaction base solution. The pH value of the base solution is controlled at 12.20, the reaction temperature is maintained at 51℃, and the concentration of ammonium sulfate in the base solution is controlled at 0.45 mol / L.

[0044] Step 3: Keep the stirring vessel running (stirring speed 40 Hz), and continuously add solutions A, C and D from step 1 to the reaction vessel at a flow rate of 10 mL / min to carry out the co-precipitation reaction. At the beginning of the reaction, solution B is continuously added to solution A at a flow rate of 2 mL / min. The reaction is carried out for 90 h until the particles grow to 9.0 μm, at which point the liquid feeding is stopped.

[0045] The pH value was maintained at 12.10 and the reaction temperature was maintained at 51℃ during the reaction process. The ammonia concentration in the slurry in the reactor was 0.40 mol / L.

[0046] Step 4: The coprecipitation reaction product from Step 3 is separated by centrifugation and washed until SO4 is reached. 2- Washing was stopped when the concentration was ≤0.30%, and the sample was dried at 90℃ for 12 hours to obtain a high-nickel ternary precursor with a gradient structure and the chemical formula Ni. 0.94 Co 0.02 Mn 0.04 (OH)2, from Figure 8 The SEM images show that the particles are spherical or near-spherical; from Figure 9 It can be seen that D 50 The particle size distribution is 9.206 μm, the particle size distribution is 0.6515, and the tap density is 2.10 g / cm³. 3 The specific surface area is 8.32 g / m². 2 .like Figure 10 As shown, the ternary cathode material prepared using this as a precursor can achieve a discharge specific capacity of 212 mAh / g.

[0047] The above description is a preferred embodiment of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A high-nickel ternary precursor with different particle sizes and concentration gradient structures, characterized in that, The precursor has the chemical formula Ni x Co y Mn z (OH)2, where 0.8 ≤ x < 1, 0 < y < 0.2, 0 < z < 0.2, and x + y + z = 1.

2. The method for preparing a high-nickel ternary precursor with different particle sizes and concentration gradients as described in claim 1, characterized in that, Includes the following steps: Step 1: Solution preparation; (1) Solution A is a mixed solution of NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O, in which the mole fraction of manganese is 0. <Mn<5%; (2) Prepare MnSO4·H2O solution as solution B, with a molar concentration of 0. <Mn<0.4 mol / L; (3) Prepare a 6~11 mol / L sodium hydroxide solution as solution C; (4) Prepare solution D with 1~3 mol / L ammonium sulfate complexing agent; Step 2: Add solution C, solution D and pure water to a closed reaction vessel with an inert gas protective atmosphere to prepare a reaction base solution with a pH of 11.00~12.

50. The concentration of ammonium sulfate in the reaction base solution is 0.1~0.5 mol / L. Step 3: Keep the reactor stirring. Add solutions A, C, and D from Step 1 to the reactor at a flow rate of 2-15 mL / min to carry out the coprecipitation reaction. Control the pH of the reactor to be 10.90-12.

40. At the beginning of the reaction, add solution B to solution A. Stop adding liquid when the particles grow to the target particle size to obtain the coprecipitation reaction product. Step 4: The coprecipitation reaction product from Step 3 is centrifuged, washed, and dried to obtain the gradient structure high-nickel ternary precursor.

3. The method for preparing a high-nickel ternary precursor with different particle sizes and concentration gradients as described in claim 2, characterized in that, In step one (1), the molar ratio of NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O is 95:4:1 ~ 85:10:

5.

4. The method for preparing a high-nickel ternary precursor with different particle sizes and concentration gradients as described in claim 3, characterized in that, In step one, the total concentration of solution A is 1~3 mol / L.

5. The method for preparing a high-nickel ternary precursor with different particle sizes and concentration gradients as described in claim 2, characterized in that, In step two, the protective atmosphere in the reactor is nitrogen or argon.

6. The method for preparing a high-nickel ternary precursor with different particle sizes and concentration gradients as described in claim 2, characterized in that, In step two, the temperature of the base liquid is 45~60℃.

7. The method for preparing a high-nickel ternary precursor with different particle sizes and concentration gradients as described in claim 6, characterized in that, In step three, the reaction temperature is 45~60℃.

8. The method for preparing a high-nickel ternary precursor with different particle sizes and concentration gradients as described in claim 2, characterized in that, In step three, the ammonia concentration in the reactor is 0.20~0.50 mol / L.

9. The method for preparing a high-nickel ternary precursor with different particle sizes and concentration gradients as described in claim 2, characterized in that, In step three, the flow rate of solution B is 0.5~3 mL / min.

10. A method for preparing a high-nickel ternary precursor with different particle sizes and concentration gradients as described in any one of claims 2-9, characterized in that, In step four, the D of the gradient structure high-nickel ternary precursor 50 The micrometer diameter is 3–15 μm, and the tap density is 1.8–2.2 g / cm³. 3 Particle size distribution 0.6 < (D 90 -D 10 ) / D 50 <0.9, specific surface area is 3~15 m² 2 / g.

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