Porous spherical cobalt oxide particle and preparation method therefor

Abstract

Disclosed are a porous spherical cobalt oxide particle and a preparation method therefor. The preparation method comprises the following steps: (1) mixing a cobalt salt solution, thiourea, and urea to form a mixed solution; (2) heating the mixed solution in step (1) and performing a reaction under an aerobic atmosphere; (3) performing solid-liquid separation, and roasting the obtained solid product under an aerobic atmosphere to obtain a roasted material; and (4) washing and drying the roasted material obtained in step (3) to obtain the porous spherical cobalt oxide particle. The cobalt oxide particle prepared by the preparation method has a relatively large specific surface area, which can significantly increase the specific capacity of a battery.

Description

Porous spherical cobalt oxide particles and preparation method thereof Technical Field

[0001] The present invention belongs to the technical field of lithium battery positive electrode materials, and in particular relates to porous spherical cobalt oxide particles and a preparation method thereof. Background Art

[0002] Lithium cobalt oxide (LCO) electrode materials, with their high specific capacity and excellent cycling stability, are currently widely used as cathode materials in the 3C (consumer electronics) sector. With the rapid development of 3C electronic products, manufacturers are increasingly demanding higher processing and electrochemical performance requirements for LCOO cathode materials. As one of the earliest commercialized cathode materials for lithium-ion batteries, LCOO remains one of the cathode materials with the highest compaction density in practical applications.

[0003] Cobalt tetroxide is a key raw material for preparing lithium cobalt oxide, the cathode material for lithium-ion batteries. Its physical and chemical properties significantly impact the performance of both the cathode material and the battery. Battery-grade cobalt tetroxide requires not only high purity and tap density, but also certain requirements for its morphology and particle size distribution. Existing methods for preparing cobalt tetroxide result in a small specific surface area, which affects the rapid charge and discharge performance of the cathode material. Furthermore, batteries prepared using existing cobalt tetroxide have a low specific capacity, failing to meet the increasingly stringent requirements of the battery industry.

[0004] Summary of the Invention

[0005] The present invention aims to address at least one of the technical problems existing in the prior art. To this end, the present invention provides porous spherical cobalt oxide particles and a method for preparing the same. The cobalt oxide particles produced by this method have a large specific surface area, significantly increasing the specific capacity of batteries.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] A method for preparing porous spherical cobalt oxide particles comprises the following steps: (1) mixing a cobalt salt solution, thiourea and urea to form a mixed solution; (2) heating the mixed solution obtained in step (1) and reacting it in an oxygen atmosphere; (3) performing solid-liquid separation and roasting the obtained solid product in an oxygen atmosphere to obtain a roasted material; and (4) washing and drying the roasted material obtained in step (3) to obtain porous spherical cobalt oxide particles.

[0008] Preferably, the cobalt salt in the cobalt salt solution in step (1) is at least one of cobalt sulfate, cobalt chloride and cobalt nitrate.

[0009] Preferably, the concentration of the cobalt salt solution in step (1) is 0.05-1.0 mol / L.

[0010] Preferably, the concentration of thiourea in the mixed solution of step (1) is 0.05-1.0 mol / L.

[0011] Preferably, the concentration of urea in the mixed solution of step (1) is 0.2-2.5 mol / L.

[0012] Preferably, the reaction temperature in step (2) is 160-180° C., and the reaction temperature is maintained for 8-12 hours.

[0013] Preferably, the pressure of the oxygen atmosphere in step (2) is 0.1-1.0 MPa.

[0014] Preferably, the calcination temperature in step (3) is 500-750° C., and the calcination time is 2-6 hours.

[0015] Preferably, the washing method in step (4) is to first wash with ethanol and then wash with pure water.

[0016] Preferably, the drying temperature in step (4) is 80-120° C., and the drying time is 2-4 hours.

[0017] Preferably, a method for preparing porous spherical cobalt oxide particles comprises the following steps:

[0018] (1) preparing a cobalt salt solution with a concentration of 0.05-1.0 mol / L, wherein the cobalt salt is at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate;

[0019] (2) adding the cobalt salt solution in step (1) into a high-pressure reactor in an amount of 3 / 5-4 / 5 of the volume of the reactor;

[0020] (3) adding thiourea and urea to the reactor to make the concentration of thiourea reach 0.05-1.0 mol / L and the concentration of urea reach 0.2-2.5 mol / L;

[0021] (4) introducing air into the reactor and controlling the air pressure in the reactor to be 0.1-1.0 MPa;

[0022] (5) Heat the reactor to 160-180°C and maintain the reaction temperature for 8-12 hours;

[0023] (6) After the reaction is completed, the solid and liquid are separated, and the obtained solid product is dried and then calcined in air or oxygen atmosphere for 2-6 hours at a calcination temperature of 500-750°C to obtain a calcined material;

[0024] (7) The calcined material is first washed with ethanol and then with pure water, and then dried at 80-120°C for 2-4 hours to obtain porous spherical cobalt oxide particles.

[0025] A porous spherical cobalt oxide particle is prepared by the above-mentioned preparation method.

[0026] A lithium cobalt oxide positive electrode material is obtained by mixing lithium carbonate and the above-mentioned porous spherical cobalt oxide particles and then sintering them.

[0027] A battery comprises the lithium cobalt oxide positive electrode material as described above.

[0028] The beneficial effects of the present invention are:

[0029] The present invention's method for preparing porous spherical cobalt oxide particles involves hydrothermally reacting a mixture of cobalt salt, urea, and thiourea in a reactor. Air at a certain pressure is then applied during the reaction to produce sulfur-doped cobalt particles. The particles are then calcined and washed with water to remove the sulfur, yielding cobalt oxide (a mixture of cobalt trioxide and cobalt oxide). The reaction equation is as follows:

[0030] During hydrothermal reaction: CO(NH2)2+H2O→2NH3+CO2 CS(NH2)2+2H2O→2NH3+CO2+H2S NH3·H2O→NH 4+ +OH - CO2+H2O→CO3 2- +2H + Co 2+ +S 2- →CoS 4CoS+O2+2H2O→4CoSOH Co 2+ +(1-0.5y)CO3 2- +yOH - →Co(OH) y (CO3) 1-0.5y 6Co(OH) y (CO3) 1-0.5y +O2→2Co3O4+3yH2O+(6-3y)CO2

[0031] During the calcination reaction: 2CoSOH+3O2→Co2O3+H2O+2SO2

[0032] During the entire hydrothermal reaction process, thiourea is decomposed to produce sulfur ions. Under the induction of sulfur ions, the generated cobalt precipitate can crystallize better. On the one hand, it avoids the direct addition of sulfur ions that leads to too rapid precipitation and the production of non-spherical waste; on the other hand, the addition of sulfur ions replaces the oxygen atoms in the crystal lattice, and atomic vacancies are generated during the subsequent further roasting and water washing to remove sulfur. When used for lithium cobalt oxide positive electrode materials, it can accommodate more lithium and improve the specific capacity of the material.

[0033] By adding air during the hydrothermal process and increasing the reaction temperature, cobalt can be directly oxidized to obtain hydrothermally synthesized cobalt tetroxide particles; at the same time, the cobalt sulfide precipitation is further oxidized to cobalt hydroxysulfide, and during calcination, cobalt trioxide particles are generated. Properly increasing the trivalent cobalt content can further reduce cation mixing during subsequent cobalt-lithium sintering and improve the material's cycle performance.

[0034] The cobalt oxide particles finally obtained are porous spherical and have a high specific surface area, which is conducive to the deintercalation and extraction of lithium ions in the prepared lithium cobalt oxide material during the charge and discharge process, ensuring that the final battery has good fast charge and discharge performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a SEM image of cobalt oxide particles prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to specific embodiments.

[0037] Example 1:

[0038] A method for preparing porous spherical cobalt oxide particles comprises the following steps:

[0039] (1) Prepare a cobalt sulfate solution with a concentration of 0.05 mol / L;

[0040] (2) adding the cobalt sulfate solution in step 1 to a high-pressure reactor in an amount of 3 / 5 of the volume of the reactor;

[0041] (3) adding thiourea and urea to the reactor to make the concentration of thiourea reach 0.05 mol / L and the concentration of urea reach 0.2 mol / L;

[0042] (4) Introduce air into the reactor and control the air pressure in the reactor to 0.1 MPa;

[0043] (5) Heat the reactor to 160°C and maintain the reaction temperature for 12 hours;

[0044] (6) After the reaction is completed, the solid and liquid are separated, and the obtained solid product is dried and then calcined in an air atmosphere for 6 hours at a calcination temperature of 500°C to obtain a calcined material;

[0045] (7) The calcined material was first washed with ethanol and then with pure water, and then dried at 80°C for 4 h to obtain porous spherical cobalt oxide particles.

[0046] A porous spherical cobalt oxide particle is prepared by the above preparation method. The SEM image of the cobalt oxide particle is shown in FIG1 .

[0047] Example 2:

[0048] A method for preparing porous spherical cobalt oxide particles comprises the following steps:

[0049] (1) Prepare a cobalt chloride solution with a concentration of 0.5 mol / L;

[0050] (2) adding the cobalt chloride solution in step 1 to the autoclave in an amount of 7 / 10 of the volume of the autoclave;

[0051] (3) adding thiourea and urea to the reactor to make the concentration of thiourea reach 0.5 mol / L and the concentration of urea reach 1.5 mol / L;

[0052] (4) Air was introduced into the reactor and the air pressure in the reactor was controlled to be 0.5 MPa;

[0053] (5) Heat the reactor to 170°C and maintain the reaction temperature for 10 hours;

[0054] (6) After the reaction is completed, the solid and liquid are separated, and the obtained solid product is dried and then calcined in an oxygen atmosphere for 4 hours at a calcination temperature of 650°C to obtain a calcined material;

[0055] (7) The calcined material was first washed with ethanol and then with pure water, and then dried at 100°C for 3 h to obtain porous spherical cobalt oxide particles.

[0056] A porous spherical cobalt oxide particle is prepared by the above preparation method.

[0057] Example 3:

[0058] A method for preparing porous spherical cobalt oxide particles comprises the following steps:

[0059] (1) Prepare a 1.0 mol / L cobalt nitrate solution;

[0060] (2) adding the cobalt nitrate solution in step 1 to a high-pressure reactor in an amount of 4 / 5 of the reactor volume;

[0061] (3) adding thiourea and urea to the reactor to make the concentration of thiourea reach 1.0 mol / L and the concentration of urea reach 2.5 mol / L;

[0062] (4) Introduce air into the reactor and control the air pressure in the reactor to 1.0 MPa;

[0063] (5) Heat the reactor to 180°C and maintain the reaction temperature for 8 hours;

[0064] (6) After the reaction is completed, the solid and liquid are separated, and the obtained solid product is dried and then calcined in an oxygen atmosphere for 2 hours at a calcination temperature of 750°C to obtain a calcined material;

[0065] (7) The calcined material was first washed with ethanol and then with pure water, and then dried at 120 °C for 2 h to obtain porous spherical cobalt oxide particles.

[0066] A porous spherical cobalt oxide particle is prepared by the above preparation method.

[0067] Comparative Example 1:

[0068] A method for preparing cobalt oxide particles comprises the following steps:

[0069] (1) Prepare a cobalt sulfate solution with a concentration of 0.05 mol / L;

[0070] (2) adding the cobalt sulfate solution in step 1 to a high-pressure reactor in an amount of 3 / 5 of the volume of the reactor;

[0071] (3) adding urea to the reactor to make the urea concentration 0.2 mol / L;

[0072] (4) Heat the reactor to 160°C and maintain the reaction temperature for 12 hours;

[0073] (5) After the reaction is completed, the solid and liquid are separated, and the obtained solid product is dried and then calcined in an air atmosphere for 6 hours at a calcination temperature of 500°C to obtain a calcined material;

[0074] (6) The calcined material was first washed with ethanol and then with pure water, and then dried at 80°C for 4 hours to obtain cobalt oxide particles.

[0075] Cobalt oxide particles are prepared by the above preparation method.

[0076] Comparative Example 2:

[0077] A method for preparing cobalt oxide particles comprises the following steps:

[0078] (1) Prepare a cobalt chloride solution with a concentration of 0.5 mol / L;

[0079] (2) adding the cobalt chloride solution in step 1 to the autoclave in an amount of 7 / 10 of the volume of the autoclave;

[0080] (3) adding urea to the reactor to make the urea concentration be 1.5 mol / L;

[0081] (4) Heat the reactor to 170°C and maintain the reaction temperature for 10 hours;

[0082] (5) After the reaction is completed, the solid and liquid are separated, and the obtained solid product is dried and then calcined in an oxygen atmosphere for 4 hours at a calcination temperature of 650°C to obtain a calcined material;

[0083] (6) The calcined material was first washed with ethanol and then with pure water, and then dried at 100°C for 3 hours to obtain cobalt oxide particles.

[0084] Cobalt oxide particles are prepared by the above preparation method.

[0085] Comparative Example 3:

[0086] A method for preparing cobalt oxide particles comprises the following steps:

[0087] (1) Prepare a 1.0 mol / L cobalt nitrate solution;

[0088] (2) adding the cobalt nitrate solution in step 1 to a high-pressure reactor in an amount of 4 / 5 of the reactor volume;

[0089] (3) adding urea to the reactor to make the urea concentration 2.5 mol / L;

[0090] (4) Heat the reactor to 180°C and maintain the reaction temperature for 8 hours;

[0091] (5) After the reaction is completed, the solid and liquid are separated, and the obtained solid product is dried and then calcined in an oxygen atmosphere for 2 hours at a calcination temperature of 750°C to obtain a calcined material;

[0092] (6) The calcined material was first washed with ethanol and then with pure water, and then dried at 120°C for 2 hours to obtain cobalt oxide particles.

[0093] Cobalt oxide particles are prepared by the above preparation method.

[0094] Test example:

[0095] 1. The specific surface areas of the cobalt oxide particles of Examples 1-3 and Comparative Examples 1-3 were tested respectively. The test results are shown in Table 1:

[0096] Table 1: Specific surface area test results:

[0097] 2. The cobalt oxides obtained in Examples 1-3 and Comparative Examples 1-3 were each mixed with lithium carbonate to a Li:Co molar ratio of 1.06. The mixture was then subjected to high-temperature solid-phase sintering in a push-plate kiln at 1000°C for 12 hours to obtain lithium cobalt oxide positive electrode materials. The lithium cobalt oxide materials obtained in Examples 1-3 and Comparative Examples 1-3 were used as the active material, acetylene black as the conductive agent, and PVDF as the binder. The active material, conductive agent, and binder were weighed in a ratio of 92:4:4. A certain amount of the organic solvent NMP was added, stirred, and coated onto aluminum foil to form a positive electrode sheet. A metallic lithium sheet was used as the negative electrode. CR2430 button cells were fabricated in an argon-filled glove box. Electrical performance testing was performed using a CT2001A blue-electricity test system. Test conditions: 3.0-4.48 V, current density 1C = 180 mAh / g, and test temperature 25±1°C. The test results are shown in Table 2.

[0098] Table 2: Electrical performance test results

[0099] As shown in Table 1, the specific surface area of ​​the porous spherical cobalt oxide particles of the present invention can reach 5.3 m 2 / g and above, the highest can reach 6.7m 2 / g. By comparing Example 1 with Comparative Example 1, Example 2 with Comparative Example 2, and Example 3 with Comparative Example 3, it can be seen that when other conditions remain unchanged, thiourea is not added to the hydrothermal reaction and air is not introduced, the specific surface area of ​​the cobalt oxide particles finally obtained will be greatly reduced.

[0100] As can be seen from Table 2, after the lithium cobalt oxide positive electrode material prepared using the porous spherical cobalt oxide particles of the present invention is assembled into a battery, the battery has a large specific capacity, the discharge capacity of the battery (0.1C / 4.48V) can reach 248.3mAh / g and above, and can reach a maximum of 249.9mAh / g, and the capacity retention rate after 600 cycles at 0.1C / 4.48V is 84% ​​and above, and can reach a maximum of 86%. At the same time, by comparing Example 1 with Comparative Example 1, Example 2 with Comparative Example 2, and Example 3 with Comparative Example 3, it can be seen that when other conditions remain unchanged, thiourea is not added to the hydrothermal reaction, and air is not introduced, the discharge capacity (0.1C / 4.48V) and the capacity retention rate of the battery finally obtained after 600 cycles will be greatly reduced.

[0101] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing porous spherical cobalt oxide particles, characterized by: The steps include: (1) mixing a cobalt salt solution, thiourea and urea to form a mixed solution; (2) heating the mixed solution of step (1) and reacting it under an oxygen atmosphere; (3) solid-liquid separation, and roasting the obtained solid product in an oxygen atmosphere to obtain a roasted material; (4) Washing and drying the calcined material obtained in step (3) to obtain porous spherical cobalt oxide particles.

2. The method for preparing porous spherical cobalt oxide particles according to claim 1, wherein: The cobalt salt in the cobalt salt solution in step (1) is at least one of cobalt sulfate, cobalt chloride and cobalt nitrate.

3. The method for preparing porous spherical cobalt oxide particles according to claim 1, wherein: The concentration of the cobalt salt solution in step (1) is 0.05-1.0 mol / L.

4. The method for preparing porous spherical cobalt oxide particles according to claim 1, wherein: The concentration of thiourea in the mixed solution of step (1) is 0.05-1.0 mol / L.

5. The method for preparing porous spherical cobalt oxide particles according to claim 1, wherein: The concentration of urea in the mixed solution of step (1) is 0.2-2.5 mol / L.

6. The method for preparing porous spherical cobalt oxide particles according to claim 1, wherein: The reaction temperature in step (2) is 160-180° C., and the reaction temperature is maintained for 8-12 hours.

7. The method for preparing porous spherical cobalt oxide particles according to claim 1, wherein: The pressure of the oxygen atmosphere in step (2) is 0.1-1.0 MPa.

8. The method for preparing porous spherical cobalt oxide particles according to claim 1, wherein: The calcination temperature in step (3) is 500-750° C., and the calcination time is 2-6 hours.

9. A porous spherical cobalt oxide particle, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. A lithium cobalt oxide positive electrode material, characterized in that: The porous spherical cobalt oxide particles are prepared by mixing lithium carbonate and the porous spherical cobalt oxide particles according to claim 9 and then sintering them.