Method for stabilizing high-nickel positive electrode material through microphase distributed manganese oxide or nickel oxide

Abstract

The invention discloses a method for stabilizing a high-nickel positive electrode material through microphase-distributed manganese oxide or nickel oxide, microphase distribution of the manganese oxide or nickel oxide is introduced into the high-nickel positive electrode material, and the manganese oxide or nickel oxide reacts with or absorbs lattice oxygen released in the circulation process of the high-nickel positive electrode material to stabilize the high-nickel positive electrode material. The oxygen vacancy concentration is dynamically adjusted, so that lattice oxygen escape is inhibited, and the cycle life and thermal stability of the material are improved.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion batteries, and specifically relates to a modification technology that distributes manganese oxide or nickel oxide in microphases in high-nickel positive electrode materials (such as lithium nickel cobalt manganese oxide, NCM) to absorb or react with oxygen ions (lattice oxygen) released during the cycle of the high-nickel material, thereby inhibiting the escape of lattice oxygen, stabilizing the material structure, and improving the cycle life and thermal stability. Background Art

[0002] With the widespread application of lithium-ion batteries in electric vehicles, energy storage systems and other fields, the demand for their high energy density and high safety is also increasing. High-nickel cathode materials (such as NCM811 and NCA) have become a research hotspot due to their high capacity characteristics. However, these materials are prone to lattice oxygen release under cyclic and high temperature environments, resulting in material structure collapse, battery performance degradation, and even thermal runaway. Therefore, it is crucial to improve the safety and electrochemical performance of lithium-ion batteries.

[0003] The structure of high nickel NCM material is layered α-NaFeO2 type (R-3m space group), and its lattice oxygen (O 2- ) is stabilized in metal oxygen octahedron (MO6). Under battery cycling or high temperature conditions, high nickel NCM materials will release lattice oxygen and form oxygen vacancies. Specifically, during high potential charge and discharge, oxygen ions are first released from the surface of the material to form oxygen vacancies; oxygen vacancies gradually diffuse into the interior of the particles, accompanied by the reduction and migration of transition metals (such as Ni 3+ →Ni 2+ ); this process destroys the integrity of the lattice structure and induces the layered structure to transform into an irreversible rock salt phase.

[0004] To solve these problems, researchers usually improve the stability of NCM materials through surface coating (such as inert oxides such as Al2O3 and ZrO2) or doping (such as Al, Mg, and Ti doping), but these methods mostly focus on inhibiting the generation of oxygen vacancies rather than dynamically adjusting the concentration of oxygen vacancies. In particular, for the large amount of lattice oxygen released during the circulation process in high-nickel materials, there is still a lack of effective capture or reaction technology. In addition, most existing surface coatings have problems such as insufficient mechanical stability and poor bonding between the coating layer and the material, which makes it difficult to meet the needs of practical applications. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a modification method by distributing manganese oxide or nickel oxide in microphase in high-nickel NCM positive electrode materials. Manganese oxide (such as MnO2, Mn3O4) or nickel oxide (such as NiO, NiCo2O4) reacts with or absorbs lattice oxygen released during the cycle to dynamically adjust the oxygen vacancy concentration in the material, thereby inhibiting the escape of lattice oxygen and improving the cycle life and thermal stability of the material. The present invention provides the following technical solution: a method for stabilizing a high-nickel positive electrode material by microphase distributed manganese oxide or nickel oxide, A microphase distribution of manganese oxide or nickel oxide is introduced into the high-nickel positive electrode material. The manganese oxide or nickel oxide reacts with or absorbs the lattice oxygen released during the cycle of the high-nickel positive electrode material to dynamically adjust the oxygen vacancy concentration, thereby inhibiting the escape of lattice oxygen and improving the cycle life and thermal stability of the material. Preferably, the manganese oxide includes one or more of MnO2, Mn3O4 or Mn2O3, and the nickel oxide includes one or more of NiO and NiCo2O4. Preferably, the microphase distributed manganese oxide or nickel oxide is prepared by coating an inert oxide, and the inert oxide includes one or more of Al2O3, ZrO2 or TiO2. Preferably, the coating layer has a thickness of 5-10 nm. Preferably, the high nickel cathode material is LiNi x Co γ Mn z O2, where 0.8≤x≤0.96, 0≤y≤0.1, 0≤z≤0.1. Preferably, the doping ratio of the microphase distribution of the manganese oxide or nickel oxide in the positive electrode material is 0.001 to 0.015 parts by mass, preferably 0.02 parts by mass. Preferably, a method for stabilizing a high-nickel cathode material by microphase distributed manganese oxide or nickel oxide comprises the following steps: (1) dispersing manganese oxide or nickel oxide particles in deionized water and ultrasonically dispersing for 30 minutes; (2) adding the dispersed manganese oxide or nickel oxide to an inert oxide precursor solution and adjusting the pH value to form a precipitate; (3) filtering and washing the reaction particles, and calcining at 300-800° C. for 3-10 hours to obtain manganese oxide or nickel oxide particles coated with an inert oxide; (4) doping the prepared microparticles into a high-nickel cathode material precursor at a set mass ratio, mixing with a lithium source, and pre-firing and main-firing in an oxygen atmosphere to obtain a high-nickel cathode material with microphase distributed manganese oxide or nickel oxide. Preferably, the calcination temperature is preferably 450°C for pre-calcination for 4 hours and 730°C for main calcination for 10 hours, and the heating rate is 2-5°C / min. Preferably, the doped mixture contains Li + The molar ratio to (Ni+Co+Mn) is 1.01 to 1.05, preferably 1.02. Preferably, the manganese oxide or nickel oxide micro-domains in the material are evenly distributed, and have excellent cycle stability and thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 Example 1 LiNi with NiO and Mn2O3 microdomains 0.96 Co 0.02 Mn 0.02 SEM image of O2 cathode material after 600 cycles; Figure 2 For Example 2 LiNi 0.96 Co 0.02 Mn 0.02 SEM image of O2 cathode material after 600 cycles; Figure 3 Example 1 LiNi with NiO and Mn2O3 microdomains 0.96 Co 0.02 Mn 0.02 XRD pattern of O2 cathode material; Figure 4 This is a capacity-cycle comparison diagram of the materials described in Examples 1 and 2. DETAILED DESCRIPTION Embodiment 1: (1) Dispersing NiO particles in deionized water and ultrasonically dispersing for 30 minutes; adding Zr(NO3)4 solution, stirring evenly, and then dropping ammonia water, adjusting the pH value to 8.5 to form zirconium hydroxide precipitation; filtering and washing the particles after the reaction, and calcining at 500°C for 4 hours to generate ZrO2-coated NiO particles; the coating layer thickness is controlled to be 5-10 nm. (2) Mn2O3 particles are dispersed in deionized water and ultrasonically dispersed for 30 minutes; Al(NO3)3·9H2O solution is added, stirred evenly, and then ammonia water is added dropwise to adjust the pH value to 9.0 to form aluminum hydroxide Al(OH)3; the particles after the reaction are filtered and washed, and calcined at 500°C for 3 hours to generate Al2O3-coated Mn2O3 particles; the coating layer thickness is controlled to be 5-10 nm. (3) NiO particles coated with ZrO2 at a ratio of 1 wt% and Mn2O3 particles coated with Al2O3 at a ratio of 2 wt% were doped into the Ni 0.96 Co 0.02 Mn 0.02 (OH)2 precursor; the doped mixture was mixed with lithium hydroxide in a molar ratio of Li:(Ni+Co+Mn)=1.02; in an oxygen atmosphere, the temperature was raised to 450°C at 2°C / min and kept at this temperature for 4 hours to complete the pre-sintering; then the temperature was raised to 730°C at 5°C / min and kept at this temperature for 10 hours to complete the main sintering; after cooling, LiNi with NiO and Mn2O3 microdomains was obtained. 0.96Co 0.02 Mn 0.02 O2 positive electrode material. (4) Material properties: XRD confirmed that the layered structure of the material was not damaged; LiNi with NiO and Mn2O3 microdomains 0.96 Co 0.02 Mn 0.02 SEM image of O2 cathode material after 600 cycles; The LiNi with NiO and Mn2O3 microdomains 0.96 Co 0.02 Mn 0.02 The capacity retention rate of lithium-ion batteries made of O2 positive electrode materials after 600 cycles at 25°C and 1C is 91.58-93.36%, and the capacity retention rate cycle performance is better than that of undoped materials. Embodiment 2: (1) Ni 0.96 Co 0.02 Mn 0.02 The (OH)2 precursor was mixed with lithium hydroxide in a molar ratio of Li:(Ni+Co+Mn)=1.02; in an oxygen atmosphere, the temperature was raised to 450°C at 2°C / min and kept at this temperature for 4 hours to complete the pre-sintering; then the temperature was raised to 730°C at 5°C / min and kept at this temperature for 10 hours to complete the main sintering; after cooling, LiNi 0.96 Co 0.02 Mn 0.02 O2 positive electrode material. (2) Material properties: ·LiNi 0.96 Co 0.02 Mn 0.02 SEM image of particles of O2 cathode material after 600 cycles; ·The LiNi 0.96 Co 0.02 Mn 0.02 The capacity retention rate of the lithium-ion battery made of O2 positive electrode material after 600 cycles at 25°C and 1C is 82.15-83.07%. Embodiment three: (1) Dispersing NiO particles in deionized water and ultrasonically dispersing for 30 minutes; adding Zr(NO3)4 solution, stirring evenly, and then dropping ammonia water, adjusting the pH value to 8.5 to form zirconium hydroxide precipitation; filtering and washing the particles after the reaction, and calcining at 500°C for 4 hours to generate ZrO2-coated NiO particles; the coating layer thickness is controlled to be 5-10 nm. (2) ZrO2-coated NiO particles were doped into Ni 0.96Co 0.02 Mn 0.02 (OH)2 precursor; the doped mixture was mixed with lithium hydroxide in a molar ratio of Li:(Ni+Co+Mn)=1.02; in an oxygen atmosphere, the temperature was raised to 450°C at 2°C / min and kept at this temperature for 4 hours to complete the pre-sintering; then the temperature was raised to 730°C at 5°C / min and kept at this temperature for 10 hours to complete the main sintering; after cooling, LiNi with NiO microdomains was obtained. 0.96 Co 0.02 Mn 0.02 O2 positive electrode material positive electrode material. Embodiment 4: (1) Disperse NiO particles in deionized water and disperse them by ultrasonic for 30 minutes; add Zr(NO3)4 solution, stir evenly, then add ammonia water, adjust the pH value to 8.5, and form zirconium hydroxide precipitate; filter and wash the particles after reaction, and calcine at 500℃ for 4 hours to generate ZrO2-coated NiO particles; the coating thickness is controlled to be 5-10nm. Disperse Mn2O3 particles in deionized water and disperse them by ultrasonic for 30 minutes; add Al(NO3)3·9H2O solution, stir evenly, then add ammonia water, adjust the pH value to 9.0, and form aluminum hydroxide Al(OH)3; filter and wash the particles after reaction, and calcine at 500℃ for 3 hours to generate Al2O3-coated Mn2O3 particles; the coating thickness is controlled to be 5-10nm. (2) By mass, 100 parts of Ni 0.96 Co 0.02 Mn 0.02 (OH)2 precursor, 0.5 parts of sucrose, 0.02 parts of Al2O3-coated Mn2O3 particles, and 0.01 parts of ZrO2-coated NiO particles are fully mixed to obtain slurry A; slurry A is coarsely ground in a coarse grinding tank to obtain slurry B, and slurry B is transferred to a nano sand mill and sand-ground to obtain slurry C, and the particle size after sand grinding is 400nm; slurry C is then spray-dried and sintered, wherein the air inlet temperature of the spray drying is 220°C, the air outlet temperature is 90°C, and the doped mixture is mixed with lithium hydroxide at a molar ratio of Li:(Ni+Co+Mn)=1.02; in an oxygen atmosphere, the temperature is raised to 450°C at 2°C / min, and the temperature is kept for 4 hours to complete pre-sintering; then the temperature is raised to 730°C at 5°C / min, and the temperature is kept for 10 hours to complete the main sintering; after cooling, LiNi with NiO and Mn2O3 microdomains is obtained 0.96 Co 0.02 Mn 0.02 O2 positive electrode material positive electrode material. Embodiment five: (1) Ni 0.96 Co 0.02 Mn 0.02The (OH)2 precursor and lithium hydroxide were mixed in a molar ratio of Li:(Ni+Co+Mn)=1.0; in an oxygen atmosphere, the temperature was raised to 450°C at 2°C / min and kept at this temperature for 4 hours to complete the pre-sintering; then the temperature was raised to 730°C at 5°C / min and kept at this temperature for 10 hours to complete the main sintering; after cooling, the lithium-poor LiNi 0.96 Co 0.02 Mn 0.02 O2 positive electrode material (because lithium will volatilize to generate lithium-poor products during high-temperature sintering, NiO and Mn2O3 micro-domains will be generated in situ inside the material). Embodiment six: (1) Ni 0.96 Co 0.02 Mn 0.02 The (OH)2 precursor is mixed with lithium hydroxide in a molar ratio of Li:(Ni+Co+Mn)=1.0. (2) In a pure oxygen atmosphere, the temperature was raised to 450°C at 3°C / min and kept at this temperature for 4 hours to complete the pre-sintering, so that the precursor was decomposed and the initial layered LiNi 0.96 Co 0.02 Mn 0.02 O2 phase. (3) After pre-sintering, the temperature was rapidly increased to 730°C at a rate of 10°C / min and kept in an oxygen atmosphere for 8 hours to complete the main sintering. Rapid heating intensifies lithium volatilization, resulting in the enrichment of Ni and Mn ions in local lithium-poor areas, which are rapidly oxidized and precipitated into NiO and Mn2O3 micro-domains at high temperatures. (4) After the main sintering is completed, the temperature is rapidly cooled to 500°C at a rate of >10°C / min to quickly lock the microdomain structure, and then slowly cooled to room temperature at a rate of 1°C / min to reduce the lattice residual stress and obtain lithium-poor LiNi rich in NiO and Mn2O3 microdomains. 0.96 Co 0.02 Mn 0.02 O2 positive electrode material. (5) In the final material, NiO and Mn2O3 microdomains are mainly distributed on the particle surface and grain boundary regions, with a size of about 1–5 nm. The interface is rich in oxygen vacancies, which is expected to enhance the oxygen ion storage and release capacity. Embodiment seven: (1) Ni 0.96 Co 0.02 Mn 0.02 The (OH)2 precursor is mixed with lithium hydroxide in a molar ratio of Li:(Ni+Co+Mn)=1.05, and ZrO2, TiO2, MgO, WO3 and SrCO3 are added (the total doping amount accounts for 2% of the total molar amount of transition metals, and the molar ratio of each element is Zr:Ti:Mg:W:Sr=1:1:1:1:1). (2) In a pure oxygen atmosphere, the temperature was raised to 450°C at 3°C / min and kept at this temperature for 4 hours to complete the pre-sintering, decompose the precursor, and initially form LiNi 0.96 Co 0.02 Mn 0.02 O2 is the main phase, and the doping elements are enriched in local areas, inducing the formation of heterogeneous nuclei. (3) After pre-sintering, the temperature was raised to 740°C at 8°C / min and kept in an oxygen atmosphere for 10 hours to complete the main sintering. The volatilization of lithium at high temperature leads to local lithium deficiency, Ni and Mn enrichment, and induces the precipitation of multi-element micro-domains under the action of doping elements, such as NiO, Mn2O3, ZrO2, Li2TiO3, MgO, WO3 and SrCO3 nanophases. The existence of these micro-domains not only provides additional active sites, but also serves as an oxygen ion buffer. (4) After the main firing, the steel is rapidly cooled to 500°C at a rate of 10°C / min to lock in the multi-domain microstructure generated at high temperature, and then slowly cooled to room temperature at a rate of 2°C / min to reduce the lattice stress. (5) In the final material, the multi-doped elements are enriched at the grain boundaries and particle surfaces to form nano-domains of 2–6 nm. These domain boundaries are rich in oxygen vacancies, which can promote the rapid migration of oxygen ions. At the same time, the doped elements stabilize the crystal structure, which is expected to improve the cycle stability and rate performance.

Claims

1. A method for stabilizing a high nickel cathode material by microphase distributed manganese oxide or nickel oxide, characterized in that: A microphase distribution of manganese oxide or nickel oxide is introduced into the high-nickel positive electrode material. The manganese oxide or nickel oxide reacts with or absorbs the lattice oxygen released during the cycle of the high-nickel positive electrode material to dynamically adjust the oxygen vacancy concentration, thereby inhibiting the escape of lattice oxygen and improving the cycle life and thermal stability of the material.

2. A method for stabilizing a high-nickel cathode material by microphase-distributed manganese oxide or nickel oxide according to claim 1, characterized in that: The manganese oxide includes one or more of MnO2, Mn3O4 or Mn2O3, and the nickel oxide includes one or more of NiO and NiCo2O4.

3. The method for stabilizing a high-nickel cathode material by microphase-distributed manganese oxide or nickel oxide according to claim 1, characterized in that: The microphase distributed manganese oxide or nickel oxide is prepared by coating an inert oxide, and the inert oxide includes one or more of Al2O3, ZrO2 or TiO2.

4. The method for stabilizing a high-nickel cathode material by microphase-distributed manganese oxide or nickel oxide according to claim 3, characterized in that: The coating layer has a thickness of 5-10 nm.

5. The method for stabilizing a high-nickel cathode material by microphase-distributed manganese oxide or nickel oxide according to claim 1, characterized in that: The high nickel positive electrode material is LiNi x Co γ Mn z O2, where 0.8≤x≤0.96, 0≤y≤0.1, 0≤z≤0.

1.

6. The method of stabilizing a high-nickel cathode material by microphase-distributed manganese oxide or nickel oxide according to claim 1, characterized in that: The doping ratio of the microphase distribution of the manganese oxide or nickel oxide in the positive electrode material is 0.001 to 0.015 parts by mass, preferably 0.02 parts by mass.

7. The method for stabilizing a high-nickel cathode material by microphase-distributed manganese oxide or nickel oxide according to claim 1, characterized in that: The following steps are involved: (1) dispersing manganese oxide or nickel oxide particles in deionized water and ultrasonically dispersing for 30 minutes; (2) adding the dispersed manganese oxide or nickel oxide to an inert oxide precursor solution and adjusting the pH value to form a precipitate; (3) filtering and washing the reaction particles, and calcining at 300-800° C. for 3-10 hours to obtain manganese oxide or nickel oxide particles coated with an inert oxide; (4) doping the prepared microparticles into a high-nickel cathode material precursor at a set mass ratio, mixing with a lithium source, and pre-firing and main-firing in an oxygen atmosphere to obtain a high-nickel cathode material with microphase distributed manganese oxide or nickel oxide.

8. The method for stabilizing a high-nickel cathode material by microphase-distributed manganese oxide or nickel oxide according to claim 7, characterized in that: The calcination temperature is preferably 450°C for pre-calcination for 4 hours and 730°C for main calcination for 10 hours, with a heating rate of 2-5°C / min.

9. The method for stabilizing a high-nickel cathode material by microphase-distributed manganese oxide or nickel oxide according to claim 7, characterized in that: The molar ratio of Li+ to (Ni+Co+Mn) in the doped mixture is 1.01 to 1.05, preferably 1.

02.

10. A high nickel positive electrode material prepared by any method of claims 1-9, characterized in that: The manganese oxide or nickel oxide micro-phase domains in the material are uniformly distributed and have excellent cycle stability and thermal stability.

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