Preparation method of high-performance lithium cobalt oxide battery positive electrode material

Abstract

This invention relates to the field of lithium battery technology and proposes a method for preparing a high-performance lithium cobalt oxide battery cathode material, comprising the following steps: Step A: Wet ball milling is performed to mix cobalt source, lithium source, gradient dopant and flux to obtain a mixed slurry, which is then dried to obtain a doped precursor; the gradient dopant includes a first dopant and a second dopant, wherein the first dopant is a high-valence metal element dopant and the second dopant is a rare earth metal element dopant; by setting the gradient doping structure and the stepped sintering structure, an element concentration gradient from the inside to the surface is formed in the lithium cobalt oxide bulk phase, the high-valence metal ions stabilize the layered framework, the rare earth ions pin the grain boundaries, and the dopant elements are dissolved layer by layer by segmented heating, which effectively suppresses lattice oxygen precipitation and phase transition under high voltage, significantly alleviates the material structure degradation problem, and solves the structural degradation and interface side reaction problems in the prior art.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a method for preparing a high-performance lithium cobalt oxide battery cathode material. Background Technology

[0002] Lithium cobalt oxide (LiCoO2), as the earliest commercially available cathode material for lithium-ion batteries, has long dominated the consumer electronics field due to its high compaction density, high volumetric energy density, and excellent rate performance. With the increasing demands for battery energy density in portable electronic devices, power tools, and drones, the operating voltage of lithium cobalt oxide has gradually increased from the traditional 4.2 V to 4.45 V and even 4.5 V. However, under high-voltage charging conditions, lithium cobalt oxide materials face a series of severe challenges: on the one hand, deep delithiation leads to a decrease in the Co³⁺ / Co ratio. 4 The intensified redox reaction leads to lattice oxygen participating in charge compensation, causing surface oxygen precipitation and structural degradation. Furthermore, under high voltage, side reactions between the material surface and the electrolyte intensify, resulting in cobalt dissolution, increased interfacial impedance, and rapid capacity decay. These problems severely restrict the cycle life and safety performance of lithium cobalt oxide batteries under high voltage.

[0003] To address these challenges, existing technologies primarily modify lithium cobalt oxide through two main approaches: bulk doping and surface coating. In bulk doping, introducing high-valence metal elements (such as Al, Mg, Ti, Zr, etc.) or rare earth elements (such as La, Y, etc.) can stabilize the crystal structure and suppress phase transitions. However, existing doping techniques often employ single-element doping or simple co-doping methods, resulting in a uniform distribution of dopant elements within the particles, making it difficult to create an elemental concentration gradient and thus limiting the improvement in surface structure stability. Regarding surface coating, metal oxides (such as Al₂O₃, ZrO₂, TiO₂) or phosphates (such as Li₃PO₄, AlPO₄) are commonly used as protective layers to isolate the electrolyte from direct contact with the cathode material. However, traditional solid-phase coating methods suffer from uneven coating, weak adhesion between the coating layer and the substrate, and low ionic conductivity of the coating layer. This leads to the coating layer easily peeling off under high voltage, which in turn increases interfacial impedance.

[0004] Furthermore, in terms of sintering processes, existing preparation methods typically employ single-stage isothermal sintering or simple segmented heat preservation processes, making it difficult to simultaneously ensure uniform diffusion of dopants, complete crystal structure development, and precise control of surface oxidation stoichiometry. Particularly in the post-coating treatment stage, traditional sintering processes often use a constant oxygen partial pressure atmosphere, making it impossible to dynamically control the interfacial oxygen vacancy concentration during coating layer formation. This results in poor interfacial compatibility between the coating layer and the substrate, limiting the coating layer's ability to suppress interfacial side reactions. Summary of the Invention

[0005] This invention proposes a method for preparing high-performance lithium cobalt oxide battery cathode materials, which solves the problems of structural degradation and interfacial side reactions in related technologies.

[0006] The technical solution of the present invention is as follows: A method for preparing a high-performance lithium cobalt oxide battery cathode material, comprising the following steps:

[0007] Step A: The cobalt source, lithium source, gradient dopant and flux are mixed by wet ball milling to obtain a mixed slurry, which is then dried to obtain the doped precursor; the gradient dopant includes a first dopant and a second dopant, the first dopant being a high-valence metal element dopant and the second dopant being a rare earth metal element dopant;

[0008] Step B: The doped precursor is placed in an oxygen-containing atmosphere and sintered for the first time using a stepped heating sintering process to obtain a gradient-doped lithium cobalt oxide matrix material; the stepped heating sintering process includes a low-temperature pre-sintering section, a medium-temperature solid solution section, and a high-temperature crystallization section performed sequentially.

[0009] Step C: The gradient-doped lithium cobalt oxide matrix material is coated with a composite coating agent in a gas phase to obtain a coating intermediate; the composite coating agent includes a lithium-based fast ion conductor precursor and a conductive metal oxide precursor; the gas phase assisted coating refers to spraying an atomized composite coating agent solution onto the surface of the gradient-doped lithium cobalt oxide matrix material in a fluidized bed using an inert gas as a carrier;

[0010] Step D: The coated intermediate is placed in an oxygen-containing atmosphere and subjected to pulsed atmosphere sintering to obtain the high-performance lithium cobalt oxide battery cathode material; the pulsed atmosphere sintering refers to the alternating introduction of high oxygen partial pressure gas and low oxygen partial pressure gas in a periodic manner during the sintering process, with the ratio of the holding time of high oxygen partial pressure to low oxygen partial pressure in each cycle being 1:0.5 to 1:2.

[0011] In a preferred embodiment of the present invention, in step A:

[0012] The molar ratio of the cobalt source to the lithium source is 1:1.02 to 1:1.12;

[0013] The first dopant is selected from at least one of niobium oxide, tantalum oxide, molybdenum oxide, and tungsten oxide, and its addition amount is 0.2 mol% to 1.5 mol% of the molar amount of the cobalt source.

[0014] The second dopant is selected from at least one of lanthanum oxide, yttrium oxide, and cerium oxide, and its addition amount is 0.1 mol% to 0.8 mol% of the molar amount of the cobalt source.

[0015] The flux is selected from at least one of lithium fluoride, ammonium fluoride, and boric acid, and its addition amount is 0.2% to 1.5% of the mass of the cobalt source.

[0016] In a preferred embodiment of the present invention, the ball milling medium for wet ball milling is deionized water, the ball milling speed is 300 rpm to 500 rpm, the ball milling time is 4 h to 8 h, and the solid content of the mixed slurry is 30% to 50%; the drying is carried out by spray drying, the inlet temperature is 180℃ to 250℃, the outlet temperature is 90℃ to 120℃, and the average particle size D50 of the obtained doped precursor is 5 μm to 15 μm.

[0017] As a preferred embodiment of the present invention, the stepped heating sintering process is specifically as follows:

[0018] Low-temperature preheating section: Heat to 350℃~500℃ at a rate of 1℃ / min~3℃ / min, and hold for 2 h~5 h;

[0019] Medium-temperature solution treatment section: Heat to 600℃~750℃ at a rate of 2℃ / min~5℃ / min, and hold for 4 h~8 h;

[0020] High-temperature crystallization section: Increase the temperature to 850℃~980℃ at a rate of 1℃ / min~4℃ / min, and hold for 8 h~15 h;

[0021] The oxygen-containing atmosphere is a high-purity oxygen atmosphere with an oxygen volume concentration of not less than 95%.

[0022] As a preferred embodiment of the present invention, after step B and before step C, the gradient-doped lithium cobalt oxide matrix material is subjected to plasma surface activation treatment. The treatment atmosphere is oxygen or argon-oxygen mixture, the treatment power is 100W to 500W, and the treatment time is 5 min to 20 min, so as to increase the oxygen vacancy concentration on the surface of the matrix material by 10% to 30%.

[0023] In a preferred embodiment of the present invention, in step C:

[0024] The lithium-based fast ion conductor precursor is a lithium lanthanum zirconium oxide precursor sol or a lithium titanium aluminum phosphate precursor sol.

[0025] The conductive metal oxide precursor is an indium tin oxide precursor sol or an aluminum-doped zinc oxide precursor sol.

[0026] The mass ratio of lithium-based fast ion conductor precursor to conductive metal oxide precursor in the composite coating agent is 1:0.3 to 1:1.5.

[0027] The total coating amount of the composite coating agent, based on solid content, is 0.5% to 2.5% of the mass of the gradient-doped lithium cobalt oxide matrix material.

[0028] In a preferred embodiment of the present invention, the process conditions for the gas-phase assisted coating in step C are as follows:

[0029] The fluidized bed temperature is 60℃~120℃, and the fluidizing gas velocity is 0.5 m / s~1.5 m / s;

[0030] The inert gas is nitrogen or argon, and the atomization pressure is 0.1 MPa to 0.4 MPa;

[0031] After spraying, continue fluidized drying in a fluidized bed for 10 to 40 minutes to obtain the coated intermediate.

[0032] As a preferred embodiment of the present invention, in step D, the temperature of the pulse atmosphere sintering is 500℃~750℃, the total sintering time is 4 h~10 h, and the heating rate is 2℃ / min~8℃ / min.

[0033] The high oxygen partial pressure gas is oxygen-rich gas with an oxygen volume concentration ≥ 90%, and the low oxygen partial pressure gas is oxygen-lean gas or inert gas with an oxygen volume concentration ≤ 5%.

[0034] The number of pulse cycles is 2 to 8, and the duration of high oxygen partial pressure in each cycle is 10 to 40 minutes, while the duration of low oxygen partial pressure is 5 to 30 minutes.

[0035] As a preferred embodiment of the present invention, after step D, the sintered product is further subjected to gradient pulverization and shaping to obtain a finished cathode material with a median particle size D50 of 4 μm to 9 μm and a particle size distribution span ≤ 1.0; the gradient pulverization and shaping includes airflow pulverization, eddy current shaping and precision classification in sequence.

[0036] In a preferred embodiment of the present invention, in step A, the cobalt source is cobalt tetroxide or cobalt hydroxyoxide, and the primary particle size of the cobalt source is 50 nm to 300 nm; the lithium source is lithium carbonate or lithium hydroxide, and the median particle size D50 of the lithium source is 1 μm to 5 μm; the particle size ratio of the cobalt source to the lithium source satisfies: primary particle size of cobalt source : median particle size of lithium source = 1:10 to 1:50.

[0037] The working principle and beneficial effects of this invention are as follows:

[0038] 1. This invention creates an element concentration gradient from the inside to the surface in the lithium cobalt oxide bulk phase by setting a gradient doping structure and a step-by-step sintering structure. High-valence metal ions stabilize the layered framework, rare earth ions pin the grain boundaries, and the doping elements are dissolved layer by layer by segmented heating, which effectively suppresses lattice oxygen precipitation and phase transformation under high voltage and significantly alleviates the problem of material structure degradation.

[0039] 2. This invention constructs a double-layer dense coating layer composed of fast ion conductors and conductive oxides on the surface of lithium cobalt oxide by setting a gas-phase assisted coating structure and a pulsed atmosphere sintering structure. Fluidized bed spraying achieves nanoscale uniform coating, and pulsed alternating oxygen partial pressure dynamically controls the concentration of oxygen vacancies at the interface, enhancing the chemical bonding between the coating layer and the substrate, effectively blocking electrolyte erosion and reducing interfacial impedance, and significantly suppressing interfacial side reactions under high voltage. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] Example

[0042] A method for preparing a high-performance lithium cobalt oxide battery cathode material includes the following steps:

[0043] Step A: The cobalt source, lithium source, gradient dopant and flux are mixed by wet ball milling to obtain a mixed slurry, which is then dried to obtain the doped precursor; the gradient dopant includes a first dopant and a second dopant, the first dopant being a high-valence metal element dopant and the second dopant being a rare earth metal element dopant;

[0044] Step B: The doped precursor is placed in an oxygen-containing atmosphere and sintered for the first time using a stepped heating sintering process to obtain a gradient-doped lithium cobalt oxide matrix material; the stepped heating sintering process includes a low-temperature pre-sintering section, a medium-temperature solid solution section, and a high-temperature crystallization section performed sequentially.

[0045] Step C: The gradient-doped lithium cobalt oxide matrix material is coated with a composite coating agent in a gas phase to obtain a coating intermediate; the composite coating agent includes a lithium-based fast ion conductor precursor and a conductive metal oxide precursor; the gas phase assisted coating refers to spraying an atomized composite coating agent solution onto the surface of the gradient-doped lithium cobalt oxide matrix material in a fluidized bed using an inert gas as a carrier;

[0046] Step D: The coated intermediate is placed in an oxygen-containing atmosphere and subjected to pulsed atmosphere sintering to obtain the high-performance lithium cobalt oxide battery cathode material; the pulsed atmosphere sintering refers to the alternating introduction of high oxygen partial pressure gas and low oxygen partial pressure gas in a periodic manner during the sintering process, with the ratio of the holding time of high oxygen partial pressure to low oxygen partial pressure in each cycle being 1:0.5 to 1:2.

[0047] In step A:

[0048] The molar ratio of the cobalt source to the lithium source is 1:1.02 to 1:1.12;

[0049] The first dopant is selected from at least one of niobium oxide, tantalum oxide, molybdenum oxide, and tungsten oxide, and its addition amount is 0.2 mol% to 1.5 mol% of the molar amount of the cobalt source.

[0050] The second dopant is selected from at least one of lanthanum oxide, yttrium oxide, and cerium oxide, and its addition amount is 0.1 mol% to 0.8 mol% of the molar amount of the cobalt source.

[0051] The flux is selected from at least one of lithium fluoride, ammonium fluoride, and boric acid, and its addition amount is 0.2% to 1.5% of the mass of the cobalt source.

[0052] In step A, the ball milling medium for wet ball milling is deionized water, the ball milling speed is 300 rpm to 500 rpm, the ball milling time is 4 h to 8 h, and the solid content of the mixed slurry is 30% to 50%. The drying is carried out by spray drying, with an inlet temperature of 180℃ to 250℃ and an outlet temperature of 90℃ to 120℃. The average particle size D50 of the obtained doped precursor is 5 μm to 15 μm.

[0053] In step B, the stepped heating sintering process specifically refers to:

[0054] Low-temperature preheating section: Heat to 350℃~500℃ at a rate of 1℃ / min~3℃ / min, and hold for 2 h~5 h;

[0055] Medium-temperature solution treatment section: Heat to 600℃~750℃ at a rate of 2℃ / min~5℃ / min, and hold for 4 h~8 h;

[0056] High-temperature crystallization section: Increase the temperature to 850℃~980℃ at a rate of 1℃ / min~4℃ / min, and hold for 8 h~15 h;

[0057] The oxygen-containing atmosphere is a high-purity oxygen atmosphere with an oxygen volume concentration of not less than 95%.

[0058] After step B and before step C, the process also includes plasma surface activation treatment of the gradient-doped lithium cobalt oxide matrix material. The treatment atmosphere is oxygen or an argon-oxygen mixture, the treatment power is 100 W to 500 W, and the treatment time is 5 min to 20 min, thereby increasing the oxygen vacancy concentration on the surface of the matrix material by 10% to 30%.

[0059] In step C:

[0060] The lithium-based fast ion conductor precursor is a lithium lanthanum zirconium oxide precursor sol or a lithium titanium aluminum phosphate precursor sol.

[0061] The conductive metal oxide precursor is an indium tin oxide precursor sol or an aluminum-doped zinc oxide precursor sol.

[0062] The mass ratio of lithium-based fast ion conductor precursor to conductive metal oxide precursor in the composite coating agent is 1:0.3 to 1:1.5.

[0063] The total coating amount of the composite coating agent, based on solid content, is 0.5% to 2.5% of the mass of the gradient-doped lithium cobalt oxide matrix material.

[0064] 7. The preparation method according to claim 1, characterized in that, in step C, the process conditions for the gas-phase assisted coating are:

[0065] The fluidized bed temperature is 60℃~120℃, and the fluidizing gas velocity is 0.5 m / s~1.5 m / s;

[0066] The inert gas is nitrogen or argon, and the atomization pressure is 0.1 MPa to 0.4 MPa;

[0067] After spraying, continue fluidized drying in a fluidized bed for 10 to 40 minutes to obtain the coated intermediate.

[0068] The pulse atmosphere sintering temperature is 500℃~750℃, the total sintering time is 4 h~10 h, and the heating rate is 2℃ / min~8℃ / min;

[0069] The high oxygen partial pressure gas is oxygen-rich gas with an oxygen volume concentration ≥ 90%, and the low oxygen partial pressure gas is oxygen-lean gas or inert gas with an oxygen volume concentration ≤ 5%.

[0070] The number of pulse cycles is 2 to 8, and the duration of high oxygen partial pressure in each cycle is 10 to 40 minutes, while the duration of low oxygen partial pressure is 5 to 30 minutes.

[0071] After step D, the sintered product is further subjected to gradient pulverization and shaping to obtain a finished cathode material with a median particle size D50 of 4 μm to 9 μm and a particle size distribution span of Span ≤ 1.0; the gradient pulverization and shaping includes airflow pulverization, eddy current shaping and precision classification in sequence.

[0072] In step A, the cobalt source is cobalt tetroxide or cobalt hydroxyoxide, and the primary particle size of the cobalt source is 50 nm to 300 nm; the lithium source is lithium carbonate or lithium hydroxide, and the median particle size D50 of the lithium source is 1 μm to 5 μm; the particle size ratio of the cobalt source to the lithium source satisfies: primary particle size of cobalt source : median particle size of lithium source = 1:10 to 1:50.

[0073] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-performance lithium cobalt oxide battery cathode material, characterized in that, Includes the following steps: Step A: The cobalt source, lithium source, gradient dopant and flux are mixed by wet ball milling to obtain a mixed slurry, which is then dried to obtain the doped precursor; the gradient dopant includes a first dopant and a second dopant, the first dopant being a high-valence metal element dopant and the second dopant being a rare earth metal element dopant; Step B: The doped precursor is placed in an oxygen-containing atmosphere and sintered for the first time using a stepped heating sintering process to obtain a gradient-doped lithium cobalt oxide matrix material; the stepped heating sintering process includes a low-temperature pre-sintering section, a medium-temperature solid solution section, and a high-temperature crystallization section performed sequentially. Step C: The gradient-doped lithium cobalt oxide matrix material is coated with a composite coating agent in a gas phase to obtain a coating intermediate; the composite coating agent includes a lithium-based fast ion conductor precursor and a conductive metal oxide precursor; the gas phase assisted coating refers to spraying an atomized composite coating agent solution onto the surface of the gradient-doped lithium cobalt oxide matrix material in a fluidized bed using an inert gas as a carrier; Step D: The coated intermediate is placed in an oxygen-containing atmosphere and subjected to pulsed atmosphere sintering to obtain the high-performance lithium cobalt oxide battery cathode material; the pulsed atmosphere sintering refers to the alternating introduction of high oxygen partial pressure gas and low oxygen partial pressure gas in a periodic manner during the sintering process, with the ratio of the holding time of high oxygen partial pressure to low oxygen partial pressure in each cycle being 1:0.5 to 1:

2.

2. The preparation method according to claim 1, characterized in that, In step A: The molar ratio of the cobalt source to the lithium source is 1:1.02 to 1:1.12; The first dopant is selected from at least one of niobium oxide, tantalum oxide, molybdenum oxide, and tungsten oxide, and its addition amount is 0.2 mol% to 1.5 mol% of the molar amount of the cobalt source. The second dopant is selected from at least one of lanthanum oxide, yttrium oxide, and cerium oxide, and its addition amount is 0.1 mol% to 0.8 mol% of the molar amount of the cobalt source. The flux is selected from at least one of lithium fluoride, ammonium fluoride, and boric acid, and its addition amount is 0.2% to 1.5% of the mass of the cobalt source.

3. The preparation method according to claim 1, characterized in that, In step A, the ball milling medium for wet ball milling is deionized water, the ball milling speed is 300 rpm to 500 rpm, the ball milling time is 4 h to 8 h, and the solid content of the mixed slurry is 30% to 50%. The drying is carried out by spray drying, with an inlet temperature of 180℃ to 250℃ and an outlet temperature of 90℃ to 120℃. The average particle size D50 of the obtained doped precursor is 5 μm to 15 μm.

4. The preparation method according to claim 1, characterized in that, In step B, the stepped heating sintering process specifically refers to: Low-temperature preheating section: Heat to 350℃~500℃ at a rate of 1℃ / min~3℃ / min, and hold for 2 h~5 h; Medium-temperature solution treatment section: Heat to 600℃~750℃ at a rate of 2℃ / min~5℃ / min, and hold for 4 h~8 h; High-temperature crystallization section: Increase the temperature to 850℃~980℃ at a rate of 1℃ / min~4℃ / min, and hold for 8 h~15 h; The oxygen-containing atmosphere is a high-purity oxygen atmosphere with an oxygen volume concentration of not less than 95%.

5. The preparation method according to claim 1, characterized in that, After step B and before step C, the process also includes plasma surface activation treatment of the gradient-doped lithium cobalt oxide matrix material. The treatment atmosphere is oxygen or an argon-oxygen mixture, the treatment power is 100 W to 500 W, and the treatment time is 5 min to 20 min, thereby increasing the oxygen vacancy concentration on the surface of the matrix material by 10% to 30%.

6. The preparation method according to claim 1, characterized in that, In step C: The lithium-based fast ion conductor precursor is a lithium lanthanum zirconium oxide precursor sol or a lithium titanium aluminum phosphate precursor sol. The conductive metal oxide precursor is an indium tin oxide precursor sol or an aluminum-doped zinc oxide precursor sol. The mass ratio of lithium-based fast ion conductor precursor to conductive metal oxide precursor in the composite coating agent is 1:0.3 to 1:1.

5. The total coating amount of the composite coating agent, based on solid content, is 0.5% to 2.5% of the mass of the gradient-doped lithium cobalt oxide matrix material.

7. The preparation method according to claim 1, characterized in that, In step C, the process conditions for the vapor-phase assisted coating are as follows: The fluidized bed temperature is 60℃~120℃, and the fluidizing gas velocity is 0.5 m / s~1.5 m / s; The inert gas is nitrogen or argon, and the atomization pressure is 0.1 MPa to 0.4 MPa; After spraying, continue fluidized drying in a fluidized bed for 10 to 40 minutes to obtain the coated intermediate.

8. The preparation method according to claim 1, characterized in that, In step D, the temperature of the pulse atmosphere sintering is 500℃~750℃, the total sintering time is 4 h~10 h, and the heating rate is 2℃ / min~8℃ / min. The high oxygen partial pressure gas is oxygen-rich gas with an oxygen volume concentration ≥ 90%, and the low oxygen partial pressure gas is oxygen-lean gas or inert gas with an oxygen volume concentration ≤ 5%. The number of pulse cycles is 2 to 8, and the duration of high oxygen partial pressure in each cycle is 10 to 40 minutes, while the duration of low oxygen partial pressure is 5 to 30 minutes.

9. The preparation method according to claim 1, characterized in that, After step D, the sintered product is further subjected to gradient pulverization and shaping to obtain a finished cathode material with a median particle size D50 of 4 μm to 9 μm and a particle size distribution span of Span ≤ 1.0; the gradient pulverization and shaping includes airflow pulverization, eddy current shaping and precision classification in sequence.

10. The preparation method according to claim 1, characterized in that, In step A, the cobalt source is cobalt tetroxide or cobalt hydroxyoxide, and the primary particle size of the cobalt source is 50 nm to 300 nm; the lithium source is lithium carbonate or lithium hydroxide, and the median particle size D50 of the lithium source is 1 μm to 5 μm; the particle size ratio of the cobalt source to the lithium source satisfies: primary particle size of cobalt source : median particle size of lithium source = 1:10 to 1:50.