Preparation method for lithium-rich manganese-based positive electrode material

Abstract

The present invention provides a preparation method for a lithium-rich manganese-based positive electrode material, comprising the following steps: carrying out co-precipitation reaction on a nickel-cobalt mixed salt solution, a precipitating agent, and a complexing agent to obtain a nickel-cobalt source; mixing the nickel-cobalt source, a manganese source, a lithium source, a carbon source, and water, and carrying out sand-milling to obtain a sand-milled slurry; spray-drying the sand-milled slurry to obtain a precursor; and pre-calcining and sintering the precursor to obtain a lithium-rich manganese-based positive electrode material. The lithium-rich manganese-based positive electrode material prepared by using an innovative process of co-precipitation-sand-milling-spraying and introducing a carbon source exhibits high tap density, high capacity, and high cycle performance.

Description

A method for preparing lithium-rich manganese-based cathode material

[0001] This application claims priority to Chinese Patent Application No. 202411449458.5, filed on October 17, 2024, entitled "A Method for Preparing a Lithium-Rich Manganese-Based Cathode Material", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention belongs to the field of cathode material preparation technology, and particularly relates to a method for preparing lithium-rich manganese-based cathode material. Background Technology

[0003] Lithium-ion batteries possess advantages such as high operating voltage, high specific energy, long cycle life, and environmental friendliness, making them the most promising energy storage devices to date. They are widely used in digital products and electric vehicles. Currently, the mainstream cathode materials include lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), and nickel-cobalt-manganese ternary cathode materials (LiNi). 1-x-y Mn x Co y O2, NCM) and lithium nickel cobalt aluminum oxide (LiNi 1-x-y Al x Co y Layered cathode materials such as O2 and NCA have achieved relatively mature development; however, these traditional cathode materials exhibit significant bottlenecks when facing high capacities. Lithium-rich manganese cathodes, with their ultra-high reversible cycle specific capacity (>250mAh / g), high operating voltage (>3.8V), low production cost, and environmental friendliness, are among the most valuable and promising cathode materials for high-capacity lithium-ion secondary batteries.

[0004] Lithium-rich manganese-based cathode materials suffer from drawbacks such as poor rate performance, capacity decay, and low tap density, which hinder their commercial application. Current research mainly focuses on in-depth exploration of the internal structure of lithium-rich manganese-based materials and modification treatments such as doping, coating, and surface modification. However, in most cases, the performance of the materials still needs to be improved, and the preparation cost is high, making industrialization difficult. Furthermore, it is difficult to ensure that lithium-rich manganese-based cathode materials have high tap density while maintaining high capacity and high cycle performance. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing lithium-rich manganese-based cathode materials, wherein the cathode materials prepared by this method have high capacity, high cycle performance and high tap density.

[0006] This invention provides a method for preparing a lithium-rich manganese-based cathode material, comprising the following steps:

[0007] A nickel-cobalt source was obtained by co-precipitation reaction of a nickel-cobalt mixed salt solution, a precipitant, and a complexing agent.

[0008] The nickel-cobalt source, manganese source, lithium source, carbon source and water are mixed and milled to obtain a milled slurry;

[0009] The sand-milled slurry is spray-dried to obtain the precursor;

[0010] The precursor is pre-sintered and sintered to obtain a lithium-rich manganese-based cathode material.

[0011] This invention obtains a nickel-cobalt source through co-precipitation, followed by the addition of carbon source and other raw materials, and then combines sand milling and spray drying to produce a lithium-rich manganese-based cathode material with high capacity, high cycle performance and high tap density.

[0012] This invention involves a co-precipitation reaction of a nickel-cobalt mixed salt solution, a precipitant, and a complexing agent to obtain a nickel-cobalt source. The invention further involves mixing nickel salt, cobalt salt, and deionized water, and stirring thoroughly to obtain a nickel-cobalt mixed salt solution. The salts in the nickel-cobalt mixed salt solution are selected from one or more of sulfates, nitrates, and acetates; the molar ratio of nickel to cobalt is 1:0.7–1.4; the concentration of nickel ions in the nickel-cobalt mixed salt solution is 1–2 mol / L; and the concentration of cobalt ions in the nickel-cobalt mixed salt solution is 1–2 mol / L.

[0013] The precipitant used in this invention is a sodium hydroxide solution or a sodium carbonate solution; the concentration of the precipitant is 0.1–2 mol / L. The complexing agent is selected from ammonia or NH4·HCO3. The coprecipitation reaction temperature is 40–70℃, and the reaction is stopped when the target particle size D50 is reached. This invention synthesizes a nickel-cobalt source with a small particle size through a coprecipitation synthesis method, ensuring thorough grinding during the sand milling process. The particle size D50 of the nickel-cobalt source is 3–20 micrometers. The nickel-cobalt source is a hydroxide or carbonate with a low phase transition temperature, which makes it easier for nickel, cobalt, manganese, and lithium elements to combine into a structurally stable lithium-rich manganese phase during sintering, improving the capacity and cycle performance of the cathode material. In a specific embodiment, the nickel-cobalt source is Ni. 1 / 2 Co 1 / 2 (OH)2 precursor or Ni 1 / 2 Co 1 / 2 CO3 precursor.

[0014] After obtaining the nickel-cobalt source, the present invention mixes the nickel-cobalt source, manganese source, lithium source, carbon source, and water, and then mills the mixture to obtain a milled slurry. The manganese source is selected from one or more of manganese dioxide, manganese trioxide, and manganese tetroxide; the lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate. The total solid content of the milled slurry is 5-50%, wherein the solid content is the sum of the nickel-cobalt source and / or the manganese source.

[0015] The carbon source used in this invention is selected from one or more of glucose, sucrose, starch, CMC, and polyethylene glycol; the concentration of the carbon source in the sand milling slurry is 0.01–0.8 mol / L. These specific types of carbon sources can appropriately increase the viscosity of the slurry and the surface tension of the sprayed droplets, thereby increasing the solidity of the particles and thus increasing the tap density.

[0016] The pH value of the sand-milled slurry described in this invention is 8.6–13, the sand-milling temperature is 40–60℃, the sand-milling time is 0.5–24 h, and the sand-milling speed is 1000–3000 rpm. This invention involves sand milling in a sand mill.

[0017] After obtaining the sand-milled slurry, the present invention spray-dries the sand-milled slurry to obtain a precursor. The inlet air temperature of the spray dryer is 150-500℃, the outlet air temperature is 80-150℃, and the peristaltic pump speed is 15-25 rpm. After the slurry is spray-dried, it forms solid spheres with a D50 size of 4-20 micrometers and a narrow particle size distribution, thus completing the secondary particle granulation process, resulting in a more uniform and stable electrochemical performance of the final product. In a specific embodiment, the inlet air temperature of the spray dryer is 250℃, 240℃, or 220℃; the outlet air temperature is 125℃, 118℃, or 115℃; the peristaltic pump speed is 20 rpm; and the D50 of the precursor is 8.5 micrometers or 10.5 micrometers.

[0018] After obtaining the precursor, the present invention pre-calcines and sintersects the precursor to obtain a lithium-rich manganese-based cathode material. The pre-calcination temperature is 450–700℃, the heating rate is 1–20℃ / min, and the holding time is 0.5–24h; the sintering temperature is 750–1100℃, the heating rate is 1–20℃ / min, and the holding time is 0.5–24h.

[0019] The lithium-rich manganese-based cathode material prepared by this invention has a composition of Li x Ni y Co z Mn t O2, wherein x is 0.9–1.4, y is 0.11–0.29, z is 0.11–0.29, and t is 0.51–0.58. In a specific embodiment, the lithium-rich manganese-based cathode material is composed of Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0020] Figure 1 is a schematic diagram of the preparation process of the lithium-rich manganese-based cathode material of the present invention. As shown in Figure 1, Ni, Co source, precipitant and complexing agent are mixed and co-precipitated to obtain precipitate. The precipitate is washed and dried to obtain nickel-cobalt source. The Ni-Co source is mixed with lithium source and Mn source and then milled. The collected slurry is spray-dried and the collected powder is sintered to obtain lithium-rich manganese-based cathode material.

[0021] This invention provides a method for preparing a lithium-rich manganese-based cathode material, comprising the following steps: co-precipitating a nickel-cobalt mixed salt solution, a precipitant, and a complexing agent to obtain a nickel-cobalt source; mixing the nickel-cobalt source, a manganese source, a lithium source, a carbon source, and water, and milling the mixture to obtain a milled slurry; spray-drying the milled slurry to obtain a precursor; and pre-firing and sintering the precursor to obtain the lithium-rich manganese-based cathode material. The lithium-rich manganese-based cathode material prepared by the above process exhibits high tap density, high capacity, and high cycle performance. Attached Figure Description

[0022] Figure 1 is a schematic diagram of the preparation process of the lithium-rich manganese-based cathode material of the present invention;

[0023] Figure 2 is a SEM image of the lithium-rich manganese-based cathode material prepared in Example 1 of the present invention;

[0024] Figure 3 is a SEM image of the lithium-rich manganese-based cathode material prepared in Example 2 of the present invention. Detailed Implementation

[0025] To further illustrate the present invention, the following detailed description of a method for preparing a lithium-rich manganese-based cathode material provided by the present invention is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0026] Example 1

[0027] (1) Weigh out a certain amount of NH3·H2O as a complexing agent, NaOH as a precipitating agent, and a mixture of CoSO4·7H2O and NiSO4·6H2O (molar ratio 1:1), and dissolve them separately in pure water (concentrations of 0.6 mol / L). -1 1.5 mol L -1 2 mol L -1 Then, under nitrogen protection and stirring conditions, the mixture is simultaneously pumped into a continuous stirred tank reactor. During the process, the temperature is maintained at 60℃, the pH at 11.5, and the rotation speed at 350 rpm. After the reaction, the material is collected, filtered, washed, and dried to obtain Ni with a particle size D50 of 8.5 micrometers. 1 / 2 Co 1 / 2 (OH)2 precursor;

[0028] (2) Take 39.561g of the precursor obtained in step (1), 80g of MnO2, 79.81g of LiOH·H2O, 2L of pure water as the medium, add 28g of sucrose and put them into a sand mill for sand milling to obtain slurry;

[0029] (3) The slurry obtained in step (2) is added to a spray dryer by a peristaltic pump for spray drying. The inlet air temperature of the spray dryer is 250°C, the outlet air temperature is 125°C, and the peristaltic pump speed is 20 rpm to obtain solid powder.

[0030] (4) The powder from step (3) is placed into a box furnace for a two-stage calcination process of pre-calcination and sintering. In the first step, the temperature is raised to 600℃ and held for 6 hours, with a heating time of 140 minutes. In the second step, the temperature is raised to 900℃ and held for 6 hours, with a heating time of 180 minutes, to obtain high-performance lithium-rich manganese-based cathode material Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0031] Example 2

[0032] (1) Weigh out a certain amount of NH4·HCO3 as a complexing agent, Na2CO3 as a precipitating agent, and a mixture of CoSO4·7H2O and NiSO4·6H2O (molar ratio 1:1), and dissolve them separately in pure water (concentrations of 0.25 mol / L). -1 2 mol L -1 2 mol L -1 Then, under nitrogen protection and stirring conditions, the mixture is simultaneously pumped into a continuous stirred tank reactor. During the process, the temperature is maintained at 60℃, the pH at 8.6, and the rotation speed at 400 rpm. After the reaction, the collected material is filtered, washed, and dried to obtain Ni with a particle size D50 of 10.5 micrometers. 1 / 2 Co 1 / 2 CO3 precursor;

[0033] (2) Take 52.638g of the precursor obtained in step (1), weigh 80g of MnO2 and 79.81g of LiOH·H2O, add 2L of pure water as a medium and 14g of sucrose, put them into a sand mill for sand milling to obtain slurry;

[0034] (3) The slurry obtained in step (2) is added to a spray dryer by a peristaltic pump for spray drying. The inlet air temperature of the spray dryer is 240℃, the outlet air temperature is 118℃, and the peristaltic pump speed is 20rpm to obtain a uniformly mixed solid powder.

[0035] (4) The powder from step (3) is placed into a box furnace for a two-stage calcination process. In the first step, the temperature is raised to 600℃ and held for 3 hours, with a heating time of 140 minutes. In the second step, the temperature is raised to 900℃ and held for 10 hours, with a heating time of 180 minutes, to obtain the high-performance lithium-rich manganese-based cathode material Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0036] Example 3

[0037] Unlike Example 1:

[0038] In step (2), 2L of pure water is used as a medium and 18g of glucose is added to the sand mill for sand milling.

[0039] In step (3), the inlet air temperature is 220℃ and the outlet air temperature is 115℃.

[0040] Example 4

[0041] The difference from Example 2 is:

[0042] In step (1), NH3·H2O is used as a complexing agent with a concentration of 0.1 mol / L;

[0043] In step (2), add 1L of water as a medium and 10g of sucrose into a sand mill for sand milling.

[0044] Example 5

[0045] Unlike Example 1:

[0046] In step (2), 1.6L of pure water is used as a medium, and 4.8g of CMC is added to the sand mill for sand milling.

[0047] Comparative Example 1

[0048] (1) Weigh 19.755g of Ni(OH)2, 19.806g of Co(OH)2 (both are commercially available Ni(OH)2 and Co(OH)2), 80g of MnO2, and 82.532g of LiOH·H2O. Add 2L of pure water as a medium and 28g of sucrose. Put the mixture into a sand mill for sand milling to obtain a slurry.

[0049] (2) The slurry obtained in step (1) is added to a spray dryer by a peristaltic pump for spray drying. The inlet air temperature of the spray dryer is 240°C, the outlet air temperature is 118°C, and the peristaltic pump speed is 18 rpm to obtain solid powder.

[0050] (3) The powder from step (2) is placed in a box furnace for a two-stage calcination process. In the first step, the temperature is raised to 600℃ and held for 3 hours, with a heating time of 140 minutes. In the second step, the temperature is raised to 900℃ and held for 3 hours, with a heating time of 180 minutes, to obtain a high-performance lithium-rich manganese-based cathode material Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0051] Comparative Example 2

[0052] Unlike Example 1:

[0053] The precursor, MnO2, and LiOH·H2O obtained in step (1) are directly sprayed without sand milling, and then the cathode material Li is prepared under the same spraying and sintering conditions. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2;

[0054] Comparative Example 3

[0055] (1) Weigh 461.8g of Li2CO3, 462.5g of MnO2, 98.9g of CoO, 97.6g of NiO and 9.3g of WO3, add each raw material and 2L of pure water to a sand mill for sand milling to obtain slurry;

[0056] (2) The slurry obtained in step (1) is added to a spray dryer by a peristaltic pump for spray drying. The inlet air temperature of the spray dryer is 240°C, the outlet air temperature is 118°C, and the peristaltic pump speed is 18 rpm to obtain solid powder.

[0057] (3) The powder from step (2) is placed in a box furnace for a two-stage calcination process. In the first step, the temperature is raised to 600℃ and held for 1 hour, with a heating time of 140 minutes. In the second step, the temperature is raised to 900℃ and held for 2 hours, with a heating time of 180 minutes, to obtain a high-performance lithium-rich manganese-based cathode material Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0058] Comparative Example 4

[0059] Unlike Example 1:

[0060] The mixed slurry obtained in step (3) is not spray-dried, but dried in an oven and then ground. Then, lithium-rich manganese-based cathode material Li is prepared under the same sintering conditions. 1.2 Ni 0.13 Co 0.13 Mn0.54 O2.

[0061] Comparative Example 5

[0062] (1) Weigh out a certain amount of NH3·H2O as a complexing agent, NaOH as a precipitating agent, and a mixture of CoSO4·7H2O, NiSO4·6H2O and MnSO4 (molar ratio of 0.13:0.13:0.54), and dissolve them in pure water (concentration of 0.6 mol / L). -1 1.5 mol L -1 2 mol L -1 Then, under nitrogen protection and stirring conditions, the mixture was simultaneously pumped into a continuous stirred tank reactor. During the process, the temperature was maintained at 60℃, the pH at 11.5, and the rotation speed at 350 rpm / min. After the reaction, the material was collected, filtered, washed, and dried to obtain Ni with a particle size D50 of 8.5 micrometers. 0.325 Co 0.325 Mn 1.35 (OH)2 precursor;

[0063] Take 30g of the precursor powder from step (1) and 26.8g of solid LiOH·H2O (4% excess to offset Li loss during sintering), mix and grind thoroughly, and place in a box furnace for a two-stage calcination process. In the first step, heat to 600℃ and hold for 1 hour, with a heating time of 140 minutes; in the second step, heat to 900℃ and hold for 2 hours, with a heating time of 180 minutes, to obtain high-performance lithium-rich manganese-based cathode material Li. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0064] Comparative Example 6

[0065] Unlike Example 1:

[0066] (2) 2L of pure water is used as the medium without adding other carbon sources and is put into a sand mill for sand milling.

[0067] The test methods and results of this invention for testing the tap density, capacity, and cycle performance of the cathode materials prepared in the above embodiments and comparative examples are shown in Table 1:

[0068] Table 1

[0069] As shown in the above embodiments, this invention provides a method for preparing lithium-rich manganese-based cathode materials, comprising the following steps: co-precipitating a nickel-cobalt mixed salt solution, a precipitant, and a complexing agent to obtain a nickel-cobalt source; mixing the nickel-cobalt source, a manganese source, a lithium source, a carbon source, and water, and milling the mixture to obtain a milled slurry; spray-drying the milled slurry to obtain a precursor; and pre-calcining and sintering the precursor to obtain a lithium-rich manganese-based cathode material. The lithium-rich manganese-based cathode material prepared using the innovative co-precipitation-milling-spray process and the introduction of a carbon source exhibits high tap density, high capacity, and high cycle performance. Experimental results show that the tap density of the lithium-rich manganese-based cathode material is 1.91–1.98 g / cm³. 3 The initial coulomb efficiency was 91.5–94.2%, the capacity retention rate after 200 cycles was 93.9–96.1%, and the 1C / 0.1C ratio was 83.6–85.7%.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium-rich manganese-based cathode material, comprising the following steps: A nickel-cobalt source was obtained by co-precipitation reaction of a nickel-cobalt mixed salt solution, a precipitant, and a complexing agent. The nickel-cobalt source, manganese source, lithium source, carbon source and water are mixed and milled to obtain a milled slurry; The sand-milled slurry is spray-dried to obtain the precursor; The precursor is pre-sintered and sintered to obtain a lithium-rich manganese-based cathode material.

2. The production method according to claim 1, characterized by, The salts in the nickel-cobalt mixed salt solution are selected from one or more of sulfates, nitrates, and acetates; The molar ratio of nickel to cobalt is 1:0 to 1.4; The concentration of nickel ions in the nickel-cobalt mixed salt solution is 1–2 mol / L; The concentration of cobalt ions in the nickel-cobalt mixed salt solution is 1–2 mol / L; The temperature for the coprecipitation reaction is 40–70℃; The particle size D50 of the nickel-cobalt source is 3 to 10 micrometers, and the reaction stops when the target particle size is reached.

3. The preparation method according to claim 1, characterized in that, The pH value of the sand-milled slurry is 8.6-13, the sand-milling temperature is 40-60℃, the sand-milling time is 0.5-24h, and the sand-milling speed is 1000-3000rpm.

4. The method of claim 1, wherein, The manganese source is selected from one or more of manganese dioxide, manganese trioxide, manganese tetroxide, manganese chloride, manganese acetate, and manganese sulfate; The lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium acetate, and lithium nitrate; The total solids content of the grinding slurry is 5-50%; The carbon source is selected from one or more of glucose, sucrose, and starch; the concentration of the carbon source in the sand mill slurry is 0.01 to 0.8 mol / L.

5. The preparation method according to claim 1, characterized in that, The inlet air temperature of the spray dryer is 150-500℃, the outlet air temperature is 80-150℃, and the peristaltic pump speed is 15-25 rpm.

6. The method of claim 1, wherein, The preheating temperature is 450–700℃, the heating rate is 1–20℃ / min, and the holding time is 0.5–24h.

7. The preparation method according to claim 1, characterized in that, The sintering temperature is 750–1100℃, the heating rate is 1–20℃ / min, and the holding time is 0.5–24h.

8. The method of claim 1, wherein, Li x Ni y Co z Mn t O2, wherein x is 0.9-1.4, y is 0.11-0.29, z is 0.11-0.29, and t is 0.51-0.

58.

9. The method of claim 1, wherein, The precipitant is a sodium hydroxide solution or a sodium carbonate solution, and the concentration of the precipitant is 0.1–2 mol / L; The complexing agent is ammonia or NH4·HCO3.

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