A high-compaction-density lithium-rich manganese-based positive electrode material and a preparation method thereof

Abstract

The application discloses a high-compaction-density lithium-rich manganese-based positive electrode material and a preparation method thereof. A transition metal carbonate or hydroxide precursor is placed in an inert atmosphere with an oxygen content of 2.3-4.8%, and is subjected to a first calcination treatment at high temperature to obtain a pretreated precursor. Then, the pretreated precursor is mixed with a lithium source, and is subjected to a second calcination treatment, and after cooling, the lithium-rich manganese-based positive electrode material with high compaction density is obtained. The application effectively adjusts the gas release behavior in the decomposition process of the precursor by controlling the pretreatment calcination atmosphere, and the obtained precursor has good flowability and compact particles, and the compaction density is significantly higher than that of a traditional air calcination product. After the second calcination, the lithium-rich manganese-based positive electrode material with high compaction density is obtained by mixing the precursor with the lithium source, the volume energy density is greatly improved, and the good flowability of the precursor is also beneficial to improving the production efficiency and product consistency. The application has a simple process and is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of electrode materials, specifically to a high-density lithium-rich manganese-based cathode material and its preparation method. Background Technology

[0002] Lithium-rich manganese-based cathode materials (xLi2MnO3·(1-x)LiMO2, M = Ni, Co, Mn, etc.) are considered to be one of the key materials for the next generation of high-energy-density lithium-ion batteries due to their high specific capacity and low cost.

[0003] However, its industrial application faces a significant bottleneck: the material's compaction density needs further improvement to enhance its volumetric energy density. The reason for this is that in the currently prevalent industrial process of preparing cathode material powder by calcining a mixture of precursor and lithium source in an air atmosphere, the precursor (usually nickel-cobalt-manganese carbonate or hydroxide) suffers from poor texture and low compaction density, thus affecting the preparation of the cathode material. Specifically: (1) The precursor has a loose texture. Especially during the calcination process in an air atmosphere, the carbonate or hydroxide ions in the precursor decompose to produce a large amount of gas (CO2 or H2O), which further leads to the formation of too many pores inside the particles and loose bonding between particles, resulting in low tap density and compaction density of the precursor itself and the cathode material powder synthesized in the subsequent reaction process. (2) Poor material flowability. Precursors with low compaction density and high porosity often have high surface energy and are prone to agglomeration, resulting in poor material flowability. This not only affects the uniformity of the material in the solid phase mixing process with lithium salt, but also easily causes problems such as blockage and wall adhesion in production links such as pipeline transportation and feeding, affecting production efficiency and product consistency. (3) Limiting the performance of cathode materials. The low compaction density and poor morphology of the precursor will be inherited by the final cathode material, resulting in low compaction density of the cathode sheet, which severely limits the volumetric energy density of the battery.

[0004] Therefore, improving the precursors for the synthesis of lithium-rich manganese-based materials and developing a preparation method that can effectively improve the compaction density and flowability of lithium-rich manganese-based precursors is of great significance for enhancing the overall performance of lithium-rich manganese-based cathode materials and promoting their large-scale industrialization. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a high-density lithium-rich manganese-based cathode material, which can achieve a compaction density exceeding 2.4 g / cm³. 3 The precursor A has a Hall current rate of no more than 25.5 s / 50 g, and the cathode material has a discharge specific capacity of more than 255 mAh / g at 0.1C.

[0006] The technical solution of the present invention is as follows: A method for preparing a high-density lithium-rich manganese-based cathode material, the method comprising: Spherical carbonate precursors were prepared by co-precipitation: Nickel sulfate, cobalt sulfate, and manganese sulfate were weighed according to stoichiometric ratio and dissolved in deionized water to prepare a mixed solution of transition metal salts with a concentration of 1.5-2.0 mol / L; sodium carbonate was used as a precipitant and ammonia as a complexing agent to prepare sodium carbonate solutions with a concentration of 1.8-2.0 mol / L and ammonia solutions with a concentration of 0.5-1.2 mol / L, respectively; the three solutions were simultaneously pumped into a reactor, and the reaction temperature was controlled at 60-65℃, the stirring speed at 300-320 r / min, nitrogen protection was maintained, the pH of the system was adjusted to 7.0±0.2, the reaction was carried out at a constant temperature for 12-15 h, and the mixture was aged for 6-8 h. The slurry was filtered and washed until sulfate ions were removed, and then vacuum dried at 120-130℃ for 12-15 h to obtain spherical carbonate precursors. The molecular formula of the carbonate precursors is: Ni x Co y Mn 1-x-y CO3, x≥0, y≥0, and x+y<0.5; The precursor was placed in an atmosphere sintering furnace, and a nitrogen-oxygen mixed gas with an oxygen volume content of 2.3-4.8% was introduced. The temperature was increased to 550-560℃ at 5-6℃ / min, and calcined at a constant temperature for 5-8 hours. The precursor was then cooled to room temperature in the furnace under a protective atmosphere to obtain precursor A. The two precursors were thoroughly ball-milled and mixed uniformly according to a stoichiometric ratio of 1:1.05-1.46 between the total amount of transition metals in precursor A and the amount of Li in Li2CO3. The mixture was then placed in a muffle furnace and calcined at a constant temperature of 900-950℃ in an air atmosphere for 12-15 hours. The mixture was then cooled to room temperature in the furnace to obtain manganese-rich cathode material.

[0007] Preferably, the carbonate precursor comprises Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3, Ni 0.15 Co 0.15 Mn 0.7 CO3, Ni 0.2 Co 0.1 Mn 0.7 CO3, Ni 0.35 Mn 0.65 CO3, Ni 0.25 Mn 0.75 CO3, Ni 0.4 Co 0.1 Mn 0.5 CO3 or Ni 0.44 Mn 0.55 One or more of CO3.

[0008] Preferably, the pH value is 7.0.

[0009] Preferably, the aging time is 8 hours.

[0010] Preferably, the stirring speed is 300 r / min.

[0011] Preferably, the concentration of the ammonia solution is 0.5 mol / L.

[0012] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1) Significantly improves precursor compaction density. By pre-treating and calcining in a low-oxygen atmosphere, the gas release rate during precursor decomposition is precisely controlled. Compared to the violent decomposition under air, this invention allows precursor particles to gradually remove water of crystallization and carbonate ions in a relatively "mild" environment, enabling more thorough solid-phase diffusion and rearrangement of the internal substances of the particles. This results in a calcined product with fewer internal pores, a denser structure, and tighter interparticle fusion, ultimately significantly improving the precursor compaction density. 2) Significantly improved material flowability. The dense particle morphology and reduced surface energy significantly improve the flowability of the precursor powder. This facilitates high-speed, efficient, and uniform mixing with the lithium source, improving the consistency of the cathode material composition. Simultaneously, good flowability reduces pipeline resistance and blockage risks during production, increasing production efficiency and capacity. 3) Improved performance of the final lithium-rich manganese-based material. The lithium-rich manganese-based cathode material synthesized from the high-compact density precursor prepared by this invention exhibits simultaneous improvement in both powder compaction density and electrode compaction density, thereby significantly increasing the volumetric energy density of the battery.

[0013] 4) The process is simple and easy to industrialize. This invention only adds a controlled atmosphere pretreatment step to the existing precursor production process. It does not require complex equipment or expensive raw materials, and the process is highly controllable, making it very suitable for large-scale industrial production. Detailed Implementation

[0014] The technical effects of the present invention will be verified through specific embodiments below, but the implementation of the present invention is not limited thereto.

[0015] Example 1 Ni was prepared by co-precipitation method 0.15 Co 0.15 Mn 0.7CO3 spherical carbonate precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were weighed according to stoichiometric ratio and dissolved in deionized water to prepare a 1.5 mol / L mixed solution of transition metal salts; sodium carbonate was used as a precipitant and ammonia as a complexing agent to prepare 1.8 mol / L sodium carbonate solution and 0.5 mol / L ammonia solution respectively; the three solutions were simultaneously pumped into the reactor, the reaction temperature was controlled at 60℃, the stirring speed at 300 r / min, nitrogen protection was applied, the pH of the system was adjusted to 7.0±0.2, the reaction was carried out at a constant temperature for 12 h, aged for 6 h, the slurry was filtered and washed until no sulfate ions were present, and then vacuum dried at 120℃ for 12 h to obtain the spherical carbonate precursor; The precursor was placed in an atmosphere sintering furnace, and a nitrogen-oxygen mixed gas with an oxygen volume content of 2.3% was introduced. The temperature was increased to 550℃ at 5℃ / min, and calcined at a constant temperature for 5 hours. The precursor was then cooled to room temperature in the furnace under a protective atmosphere to obtain precursor A. The two precursors were thoroughly ball-milled and mixed uniformly according to a stoichiometric ratio of 1:1.05 between the total amount of transition metals in precursor A and the amount of Li in Li2CO3. The mixture was then placed in a muffle furnace and calcined at a constant temperature of 900℃ in air for 12 hours. The mixture was then cooled to room temperature in the furnace to obtain manganese-rich cathode material.

[0016] Example 2 Ni was prepared by co-precipitation method 0.15 Co 0.15 Mn 0.7 CO3 spherical carbonate precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were weighed according to stoichiometric ratio and dissolved in deionized water to prepare a 1.5 mol / L mixed solution of transition metal salts; sodium carbonate was used as a precipitant and ammonia as a complexing agent to prepare 1.8 mol / L sodium carbonate solution and 0.5 mol / L ammonia solution respectively; the three solutions were simultaneously pumped into the reactor, the reaction temperature was controlled at 60℃, the stirring speed at 300 r / min, nitrogen protection was applied, the pH of the system was adjusted to 7.0±0.2, the reaction was carried out at a constant temperature for 12 h, aged for 6 h, the slurry was filtered and washed until no sulfate ions were present, and then vacuum dried at 120℃ for 12 h to obtain the spherical carbonate precursor; The precursor was placed in an atmosphere sintering furnace, and a nitrogen-oxygen mixed gas with an oxygen volume content of 4.8% was introduced. The temperature was increased to 550℃ at 5℃ / min, and calcined at a constant temperature for 5 hours. The precursor was then cooled to room temperature in the furnace under a protective atmosphere to obtain precursor A. The two precursors were ball-milled and mixed thoroughly according to a stoichiometric ratio of 1:1.05 between the total amount of transition metals in precursor A and the amount of Li in Li2CO3. The mixture was then placed in a muffle furnace and calcined at a constant temperature of 900℃ in air for 12 hours. The mixture was then cooled to room temperature in the furnace to obtain manganese-rich cathode material B.

[0017] Example 3 Ni was prepared by co-precipitation method 0.15 Co 0.15 Mn 0.7 CO3 spherical carbonate precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were weighed according to stoichiometric ratio and dissolved in deionized water to prepare a 1.5 mol / L mixed solution of transition metal salts; sodium carbonate was used as a precipitant and ammonia as a complexing agent to prepare 1.8 mol / L sodium carbonate solution and 0.5 mol / L ammonia solution respectively; the three solutions were simultaneously pumped into the reactor, the reaction temperature was controlled at 60℃, the stirring speed at 300 r / min, nitrogen protection was applied, the pH of the system was adjusted to 7.0±0.2, the reaction was carried out at a constant temperature for 12 h, aged for 6 h, the slurry was filtered and washed until no sulfate ions were present, and then vacuum dried at 120℃ for 12 h to obtain the spherical carbonate precursor; The precursor was placed in an atmosphere sintering furnace, and a nitrogen-oxygen mixed gas with an oxygen volume content of 2.3% was introduced. The temperature was increased to 550℃ at 5℃ / min, and calcined at a constant temperature for 5 hours. The precursor was then cooled to room temperature in the furnace under a protective atmosphere to obtain precursor A. The two precursors were thoroughly ball-milled and mixed uniformly according to a stoichiometric ratio of 1:1.22 between the total amount of transition metals in precursor A and the amount of Li in Li2CO3. The mixture was then placed in a muffle furnace and calcined at a constant temperature of 900℃ in air for 12 hours. The mixture was then cooled to room temperature in the furnace to obtain manganese-rich cathode material.

[0018] Example 4 Ni was prepared by co-precipitation method 0.15 Co 0.15 Mn 0.7 CO3 spherical carbonate precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were weighed according to stoichiometric ratio and dissolved in deionized water to prepare a 1.5 mol / L mixed solution of transition metal salts; sodium carbonate was used as a precipitant and ammonia as a complexing agent to prepare 1.8 mol / L sodium carbonate solution and 0.5 mol / L ammonia solution respectively; the three solutions were simultaneously pumped into the reactor, the reaction temperature was controlled at 60℃, the stirring speed at 300 r / min, nitrogen protection was applied, the pH of the system was adjusted to 7.0±0.2, the reaction was carried out at a constant temperature for 12 h, aged for 6 h, the slurry was filtered and washed until no sulfate ions were present, and then vacuum dried at 120℃ for 12 h to obtain the spherical carbonate precursor; The precursor was placed in an atmosphere sintering furnace, and a nitrogen-oxygen mixed gas with an oxygen volume content of 2.3% was introduced. The temperature was increased to 550℃ at 5℃ / min, and calcined at a constant temperature for 5 hours. The precursor was then cooled to room temperature in the furnace under a protective atmosphere to obtain precursor A. The two precursors were thoroughly ball-milled and mixed uniformly according to a stoichiometric ratio of 1:1.46 between the total amount of transition metals in precursor A and the amount of Li in Li2CO3. The mixture was then placed in a muffle furnace and calcined at a constant temperature of 900℃ in air for 12 hours. The mixture was then cooled to room temperature in the furnace to obtain manganese-rich cathode material.

[0019] Example 5 Ni was prepared by co-precipitation method 0.15 Co 0.15 Mn 0.7 CO3 spherical carbonate precursor: Nickel sulfate, cobalt sulfate, and manganese sulfate were weighed according to stoichiometric ratio and dissolved in deionized water to prepare a 1.5 mol / L mixed solution of transition metal salts; sodium carbonate was used as a precipitant and ammonia as a complexing agent to prepare 1.8 mol / L sodium carbonate solution and 0.5 mol / L ammonia solution respectively; the three solutions were simultaneously pumped into the reactor, the reaction temperature was controlled at 60℃, the stirring speed at 300 r / min, nitrogen protection was applied, the pH of the system was adjusted to 7.0±0.2, the reaction was carried out at a constant temperature for 12 h, aged for 6 h, the slurry was filtered and washed until no sulfate ions were present, and then vacuum dried at 120℃ for 12 h to obtain the spherical carbonate precursor; The precursor was placed in an atmosphere sintering furnace, and a nitrogen-oxygen mixed gas with an oxygen volume content of 2.3% was introduced. The temperature was increased to 550℃ at 5℃ / min, and calcined at a constant temperature for 5 hours. The precursor was then cooled to room temperature in the furnace under a protective atmosphere to obtain precursor A. The two precursors were ball-milled and mixed thoroughly according to a stoichiometric ratio of 1:1.46 between the total amount of transition metals in precursor A and the amount of Li in Li2CO3. The mixture was then placed in a muffle furnace and calcined at a constant temperature of 900℃ in air for 12 hours. The mixture was then cooled to room temperature in the furnace to obtain manganese-rich cathode material B. Finally, manganese-rich cathode material B was cryogenically treated in liquid nitrogen for 3 hours.

[0020] Comparative Example 1 The step of calcining nitrogen-oxygen mixed gas to prepare precursor A is omitted, and the remaining conditions are exactly the same as in Example 4.

[0021] Comparative Example 2 Except for the oxygen volume content in the nitrogen-oxygen mixture being 6.5%, the other conditions were exactly the same as in Example 4.

[0022] Comparative Example 3 Except for the stoichiometric ratio of the total amount of transition metals in precursor A to the amount of Li in Li2CO3 being 1:0.8, all other conditions were exactly the same as in Example 4.

[0023] Comparative Example 4 Except for the stoichiometric ratio of the total amount of transition metals in precursor A to the amount of Li in Li2CO3 being 1:1.75, all other conditions were exactly the same as in Example 4.

[0024] The compaction density, Hall flow rate, and 0.1C discharge specific capacity of the cathode material in Examples 1-5 and Comparative Examples 1-4 were tested below. For Comparative Example 1, since precursor A was not prepared, the data in the table represent the characterization of the spherical carbonate precursor. The experimental results are shown in Table 1.

[0025] Table 1 Test data for each sample As shown in Table 1, controlling the oxygen volume content in the nitrogen-oxygen mixture between 2.3% and 4.8% can achieve a compaction density exceeding 2.4 g / cm³. 3 A precursor A with a Hall flow rate not exceeding 25.5 s / 50 g was used. By controlling the ratio of the total amount of transition metals in precursor A to the amount of Li in Li₂CO₃ at 1:1.05-1.46, a cathode material with a 0.1C discharge specific capacity exceeding 255 mAh / g could be obtained. Furthermore, cryogenic treatment of the cathode material could further enhance its performance. The compaction density of the manganese-rich cathode material in this invention was further measured; the compaction densities of Examples 1-5 were all greater than 3.02 g / cm³. 3 .

[0026] 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 technical principles 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 high-density lithium-rich manganese-based cathode material, characterized in that, The preparation method includes: Spherical carbonate precursors were prepared by co-precipitation: Nickel sulfate, cobalt sulfate, and manganese sulfate were weighed according to stoichiometric ratio and dissolved in deionized water to prepare a mixed solution of transition metal salts with a concentration of 1.5-2.0 mol / L; sodium carbonate was used as a precipitant and ammonia as a complexing agent to prepare sodium carbonate solutions with a concentration of 1.8-2.0 mol / L and ammonia solutions with a concentration of 0.5-1.2 mol / L, respectively; the three solutions were simultaneously pumped into a reactor, and the reaction temperature was controlled at 60-65℃, the stirring speed at 300-320 r / min, nitrogen protection was maintained, the pH of the system was adjusted to 7.0±0.2, the reaction was carried out at a constant temperature for 12-15 h, and the mixture was aged for 6-8 h. The slurry was filtered and washed until sulfate ions were removed, and then vacuum dried at 120-130℃ for 12-15 h to obtain spherical carbonate precursors. The molecular formula of the carbonate precursors is: Ni x Co y Mn 1-x-y CO3, x≥0, y≥0, and x+y<0.5; The precursor was placed in an atmosphere sintering furnace, and a nitrogen-oxygen mixed gas with an oxygen volume content of 2.3-4.8% was introduced. The temperature was increased to 550-560℃ at 5-6℃ / min, and calcined at a constant temperature for 5-8 hours. The precursor was then cooled to room temperature in the furnace under a protective atmosphere to obtain precursor A. The two precursors were thoroughly ball-milled and mixed uniformly according to a stoichiometric ratio of 1:1.05-1.46 between the total amount of transition metals in precursor A and the amount of Li in Li2CO3. The mixture was then placed in a muffle furnace and calcined at a constant temperature of 900-950℃ in an air atmosphere for 12-15 hours. The mixture was then cooled to room temperature in the furnace to obtain manganese-rich cathode material.

2. A preparation method as described in claim 1, characterized in that, The carbonate precursor includes Ni 1 / 6 Co 1 / 6Mn 4 / 6 CO3, Ni 0.15 Co 0.15 Mn 0.7 CO3, Ni 0.2 Co 0.1 Mn 0.7 CO3, Ni 0.35 Mn 0.65 CO3, Ni 0.25 Mn 0.75 CO3, Ni 0.4 Co 0.1 Mn 0.5 CO3 or Ni 0.44 Mn 0.55 One or more of CO3.

3. A preparation method as described in claim 1, characterized in that, The pH value is 7.

0.

4. A preparation method as described in claim 1 or 2, characterized in that, The aging time is 8 hours.

5. A preparation method as described in claim 1, characterized in that, The stirring speed is 300 r / min.

6. A preparation method as described in claim 1, characterized in that, The concentration of the ammonia solution is 0.5 mol / L.

7. A high-density lithium-rich manganese-based cathode material prepared by the method according to any one of claims 1-6.

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