Method for preparing high-conductivity lithium nickel manganese oxide material based on thermal cracking method and application

Abstract

The invention discloses a method for preparing a high-conductivity lithium nickel manganese oxide material based on a thermal cracking method and application, and the method comprises the following steps: dissolving a nickel source, a manganese source and a lithium source in a solvent according to a stoichiometric ratio, and stirring until the nickel source, the manganese source and the lithium source are completely dissolved to form a uniform nickel manganese lithium salt solution; introducing the uniformly mixed nickel-manganese-lithium salt solution into a spray cracking furnace, and carrying out spray cracking treatment; introducing the cracked product into a sintering kiln to form a hollow spherical lithium nickel manganese oxide; mixing the prepared lithium nickel manganese oxide with a carbon source, introducing the mixture into a spray cracking furnace, and carrying out secondary spray cracking under the protection of nitrogen to form a carbon-coated hollow spherical crude product; and naturally cooling the crude product to room temperature, and screening to obtain the hollow spherical lithium nickel manganese oxide material with uniform particle size distribution. According to the invention, a synergistic process of spray thermal cracking and carbon-coated secondary cracking is adopted for the first time, so that the electronic conductivity of the lithium nickel manganese oxide is greatly increased, and meanwhile, the high-temperature cycle function of the lithium nickel manganese oxide is improved.

Description

Technical Field

[0001] The present invention relates to the field of battery material preparation, and specifically to a method and application of preparing high-conductivity lithium nickel manganese oxide material based on a thermal cracking method. Background Art

[0002] As a lithium-ion battery cathode material with a spinel structure, lithium nickel manganese oxide has attracted widespread attention due to its unique advantages. It has a high operating voltage (about 4.7V vs. Li + / Li), meaning that lithium nickel manganese oxide batteries can store more energy for the same mass and volume, significantly improving the battery's energy density. Furthermore, lithium nickel manganese oxide does not contain scarce and expensive elements such as cobalt, resulting in relatively low raw material costs, which facilitates large-scale commercial applications. The material also exhibits excellent thermal and structural stability, making it less susceptible to structural collapse and phase transitions during charge and discharge, ensuring a long battery cycle life.

[0003] Although lithium nickel manganese oxide materials have many advantages, they still face some key problems that need to be solved in practical applications.

[0004] Low electronic conductivity: Lithium nickel manganese oxide is a semiconductor material with low electronic conductivity, which severely limits the battery's charge and discharge rates and power characteristics. During rapid charge and discharge, electrons cannot be transported quickly within the material, increasing the battery's internal resistance and causing significant heat generation. This not only reduces the battery's energy conversion efficiency but also poses potential safety risks.

[0005] Side reactions with high-voltage electrolytes: LiMnO2's high operating voltage makes it susceptible to side reactions with commonly used electrolytes. During the charge and discharge process, the solvent and lithium salts in the electrolyte undergo oxidative decomposition at high voltages, producing gases and impurities. These products corrode the surface of the LiMnO2 material, destroying its spinel structure, leading to accelerated capacity decay and shortened cycle life. Furthermore, these side reactions consume the solvent and additives in the electrolyte, further impacting battery performance.

[0006] Inadequate power characteristics: Due to its low electronic conductivity and high ion diffusion resistance, the power characteristics of lithium nickel manganese oxide (LMNO) materials are difficult to meet in some applications requiring fast charging and discharging, such as electric vehicle fast charging and high-power energy storage systems. Therefore, improving the power characteristics of LMNO materials has become one of the key challenges in achieving their large-scale application.

[0007] In order to solve the problems of lithium nickel manganese oxide materials, researchers at home and abroad have carried out a lot of research work and made some progress. At present, the commonly used improvement methods mainly include element doping, surface coating and nano-crystallization.

[0008] Element doping: By adding other metal elements, such as aluminum, magnesium, titanium, etc., to lithium nickel manganese oxide materials, the crystal structure and electronic structure of the material can be changed, thereby improving the electronic conductivity and ion diffusion rate (such as the preparation method of a hollow lithium nickel manganese oxide structure doped lithium ion battery positive electrode material disclosed in publication number CN103746108A). However, the effect of element doping is often limited by the type of doping element, the doping amount and the doping position, and may introduce new impurity phases, affecting the stability of the electrochemical properties of the material. In addition, element doping usually requires a specific synthesis process and precise control conditions, which increases production costs and process difficulty.

[0009] Surface coating: Surface coating is a commonly used method to improve the surface properties of materials. By coating the surface of lithium nickel manganese oxide particles with a layer of conductive or stable material (such as carbon, metal oxide, solid electrolyte, etc.), the direct contact between the material and the electrolyte can be reduced, the occurrence of side reactions can be inhibited, and the electronic conductivity can be improved.

[0010] For example, a preparation method of a surface-coated modified lithium nickel manganese oxide material is disclosed in publication number CN118894561A. In this patent application, a hollow micron-spherical lithium nickel manganese oxide material is first prepared by a hydrothermal method assisted by fluorodeoxyglucose; then the hollow micron-spherical lithium nickel manganese oxide material is coated once with dextran to obtain a once-coated lithium nickel manganese oxide material; then the once-coated lithium nickel manganese oxide material is coated twice with an aluminum isopropoxide solution, and finally, heat treatment and sintering are performed under an inert mixed gas to obtain a surface-coated modified lithium nickel manganese oxide material. The obtained surface-coated modified lithium nickel manganese oxide material has good cycle stability, rate performance, and thermal stability.

[0011] However, existing surface coating technologies suffer from problems such as uneven coating layers and difficulty controlling thickness, resulting in unstable coating effects. Furthermore, the preparation process of some coating materials is complex and costly, making large-scale industrial production difficult.

[0012] Nano-materialization: Preparing lithium nickel manganese oxide materials into nanoparticles can shorten the transmission path of electrons and ions, increase the reactivity of the material, and thus improve electronic conductivity and power characteristics.

[0013] For example, the lithium nickel manganese oxide cathode material disclosed in publication number CN108417830A describes lithium nickel manganese oxide nanoparticles with an average particle size of 150 to 250 nm, microrods with an average diameter of 1.5 to 2.5 μm, and microrods with an average length of 6 to 12 μm. The present invention provides a hierarchical structure of micron-nano assemblies, i.e., a composite of nanoparticles and microrods. The nanoparticles facilitate rapid lithium ion insertion and extraction, while the microrods serve as the primary structure, offering excellent thermodynamic stability. This combination improves the specific capacity and cycling stability of the lithium nickel manganese oxide cathode material.

[0014] However, nanoparticles have high surface energy and are prone to agglomeration, which can reduce the material's performance. Furthermore, nano-sizing typically requires specialized equipment and processes, increasing production costs and complexity.

[0015] In summary, although the existing technology has achieved certain results in improving the performance of lithium nickel manganese oxide materials, it still has many limitations and cannot meet the market's urgent demand for high-performance lithium-ion battery positive electrode materials. Summary of the Invention

[0016] The purpose of the present invention is to provide a method and application for preparing high-conductivity lithium nickel manganese oxide materials based on thermal cracking. Through the synergy of the first spray thermal cracking and the carbon coating secondary cracking process, a substantial increase in the electronic conductivity of lithium nickel manganese oxide, effective suppression of side reactions with high-voltage electrolytes, and significant enhancement of power characteristics are achieved.

[0017] To achieve the above object, the present invention provides the following technical solution: a method for preparing a high-conductivity lithium nickel manganese oxide material based on a thermal decomposition method, comprising the steps of:

[0018] S1: Prepare nickel-manganese-lithium salt solution with a molar concentration of 1.0-2.5 mol / L. Dissolve nickel source, manganese source and lithium source in a solvent according to a stoichiometric ratio and stir until completely dissolved to form a uniform nickel-manganese-lithium salt solution;

[0019] S2: First spray pyrolysis, introducing the uniformly mixed nickel-manganese-lithium salt solution into a spray pyrolysis furnace and treating it using a single-stage spray pyrolysis or a two-stage spray pyrolysis process to generate a nickel-manganese oxide precursor product;

[0020] S3: Heat treatment of the intermediate product: introducing the cracked product into a sintering kiln, keeping it at 750-980°C for 6-20 hours, then cooling it to 500-650°C at a cooling rate of 5°C / min, and keeping it at that temperature for 3-10 hours to allow the product to fully crystallize and form nickel-manganese oxide;

[0021] S4: Carbon-coated secondary pyrolysis: The nickel-manganese oxide prepared in step S3 is mixed with a carbon source and introduced into a spray pyrolysis furnace for secondary spray pyrolysis under nitrogen protection. The secondary pyrolysis temperature is 300-850°C to form a carbon-coated hollow spherical crude product;

[0022] S5: femtosecond laser scanning of the hollow spherical crude product;

[0023] S6: Post-processing and screening: the crude product after femtosecond laser treatment is naturally cooled to room temperature, and sieved to obtain a hollow spherical lithium nickel manganese oxide material with uniform particle size distribution.

[0024] Preferably, in step S1, the nickel source is at least one or more combinations of nickel sulfate, nickel acetate, nickel chloride, and nickel hydroxide; the manganese source is at least one or more combinations of manganese sulfate, manganese acetate, and manganese chloride; the lithium source is at least one or more combinations of lithium carbonate, lithium acetate, and lithium hydroxide; and the solvent is at least one or more combinations of deionized water, ethanol, or isopropanol.

[0025] Preferably, the atomization method of the spray cracking in step S2 and step S4 is centrifugal atomization or pressure atomization, the atmosphere in the spray cracking furnace in step S2 is air, oxygen or a mixture of air and oxygen, and the atmosphere in the sintering kiln in step S3 is air, oxygen or a mixture of air and oxygen.

[0026] Preferably, the single-stage spray cracking in step S2 refers to performing cracking spray at 500-980° C., with a spray time of 2-30 s.

[0027] Preferably, the two-stage spray pyrolysis in step S2 is first performed at 700-980 ° C. High-frequency resonance spraying (frequency 50-200 Hz), the droplets are forced to vibrate to form a porous structure, and the pyrolysis time is 5-15 s; the pyrolysis product is introduced into a sintering kiln, kept at 750 ° C.-980 ° C. for 6-20 hours, and then quickly cooled to 500-650 ° C., and water vapor is introduced for surface hydroxylation modification.

[0028] Preferably, the carbon source in step S4 is any one or more combinations of graphene, carbon nanotubes, carbon black, and organic carbon sources, and the carbon content of the carbon source before carbon coating in S4 is 0.01%-0.5%.

[0029] Preferably, the carbon source is added by direct mixing or pre-dispersing in a solvent to form a carbon source solution and then mixing.

[0030] Preferably, step S5 specifically includes: using a femtosecond laser with a wavelength of 800nm ​​and a pulse width of 50fs to scan the hollow spherical crude product at a scanning speed of 100-500mm / s. During the laser scanning process, high-energy laser pulses act on the surface of the material, which can break some chemical bonds on the surface of the material, thereby introducing oxygen vacancies and lattice distortion, and further optimizing the electrochemical properties of the material.

[0031] Preferably, the hollow spherical lithium nickel manganese oxide material prepared in step S6 has a particle size of 1-20 μm and a carbon content of 0.01%-0.3%.

[0032] The application of the method for preparing high-conductivity lithium nickel manganese oxide materials based on thermal decomposition in the preparation of battery positive electrode materials and supercapacitor electrode materials.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The preparation method of the present invention adopts a synergistic process of primary spray pyrolysis and carbon coating secondary pyrolysis, which achieves a substantial jump in the electronic conductivity of lithium nickel manganese oxide, effective suppression of side reactions with high-voltage electrolytes, and significant enhancement of power characteristics. The primary spray pyrolysis can precisely control the reaction conditions to generate a nickel manganese oxide precursor with a uniform particle size distribution and a suitable pore structure. This microstructure provides a good foundation for subsequent carbon coating, allowing the carbon source to be evenly attached to the surface of the particles. During the secondary pyrolysis process, the carbon source is converted into a conductive carbon layer, which is evenly and tightly coated on the surface of the lithium nickel manganese oxide particles, forming a three-dimensional conductive network. This network structure provides an additional fast channel for electron transmission, greatly reducing the transmission resistance of electrons inside the material.

[0035] 2. The conductive carbon layer formed on the surface of the lithium nickel manganese oxide particles during the carbon-coated secondary cracking process of the present invention serves as an important physical barrier. The decomposition products of high-voltage electrolytes are typically highly corrosive and easily react with the lithium nickel manganese oxide material, leading to structural damage and performance degradation. The carbon layer prevents direct contact between the electrolyte and the lithium nickel manganese oxide, reducing the occurrence of side reactions.

[0036] 3. In addition to the improvement of electronic conductivity, the process of the present invention also optimizes the ion diffusion performance of the lithium nickel manganese oxide material. The uniform microstructure and suitable pore structure generated by spray pyrolysis provide a smooth channel for the diffusion of lithium ions. During the charge and discharge process, lithium ions can be quickly embedded in and out of the material, reducing the resistance to ion diffusion. The improvement of electronic conductivity and the optimization of ion diffusion work together to enable the lithium nickel manganese oxide material to quickly exchange electrons and ions during the charge and discharge process, thereby significantly improving the power characteristics and meeting the requirements of high-power batteries for positive electrode materials.

[0037] 4. This invention significantly enhances the cycling stability of lithium nickel manganese oxide materials through the combined effects of improving electronic conductivity, mitigating side reactions, and optimizing power characteristics. During long-term cycling, the material maintains good structural and performance stability, reducing the rate of capacity fade and performance degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a comparative bar chart of the comparative example and Examples 1, 2 and 3 in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] Example 1: The present invention provides a technical solution: a method for preparing a high-conductivity lithium nickel manganese oxide material based on a thermal decomposition method, comprising the steps of:

[0041] S1: Prepare nickel-manganese-lithium salt solution with a molar concentration of 1.0-2.5 mol / L. Dissolve nickel source, manganese source and lithium source in a solvent according to a stoichiometric ratio and stir until completely dissolved to form a uniform nickel-manganese-lithium salt solution;

[0042] S2: First spray pyrolysis, introducing the uniformly mixed nickel-manganese-lithium salt solution into the spray pyrolysis furnace and treating it using a single-stage spray pyrolysis method to generate a nickel-manganese oxide precursor product;

[0043] S3: Heat treatment of the intermediate product: the cracked product is introduced into a sintering kiln and kept at 750-980°C for 6-20 hours, then cooled to 500-650°C at a cooling rate of 5°C / min and kept at this temperature for 3-10 hours to allow the product to fully crystallize and form nickel-manganese oxide;

[0044] S4: Carbon-coated secondary pyrolysis: The nickel-manganese oxide prepared in step S3 is mixed with a carbon source and introduced into a spray pyrolysis furnace for secondary spray pyrolysis under nitrogen protection. The secondary pyrolysis temperature is 300-850°C to form a carbon-coated hollow spherical crude product;

[0045] S5: Post-processing and screening: the treated crude product is naturally cooled to room temperature, and sieved to obtain a hollow spherical lithium nickel manganese oxide material with uniform particle size distribution.

[0046] In this embodiment, in step S1, the nickel source is at least one or more combinations of nickel sulfate, nickel acetate, nickel chloride, and nickel hydroxide; the manganese source is at least one or more combinations of manganese sulfate, manganese acetate, and manganese chloride; the lithium source is at least one or more combinations of lithium carbonate, lithium acetate, and lithium hydroxide; and the solvent is at least one or more combinations of deionized water, ethanol, or isopropanol.

[0047] In this embodiment, the single-stage spray cracking in step S2 refers to performing cracking spray at 500-980° C. with a spray time of 2-30 seconds.

[0048] In this embodiment, the carbon source in step S4 is any one or more combinations of graphene, carbon nanotubes, and organic carbon sources, and the carbon content of the carbon source before carbon coating in S4 is 0.01%-0.5%.

[0049] In this embodiment, the carbon source is added by direct mixing or pre-dispersing in a solvent to form a carbon source solution and then mixing.

[0050] In this embodiment, the hollow spherical lithium nickel manganese oxide material prepared in step S5 has a particle size of 5 μm and a carbon content of 0.2%.

[0051] Example 1 discloses a method for preparing a high-conductivity lithium nickel manganese oxide material based on a thermal cracking method. It forms a nickel manganese oxide precursor through single-stage spray thermal cracking and realizes the synergy of the carbon coating process through secondary spray cracking, effectively improving the electronic conductivity of the material, while optimizing the crystal structure and surface morphology of the material, and finally obtaining a hollow spherical lithium nickel manganese oxide material with excellent performance.

[0052] The method for preparing high-conductivity lithium nickel manganese oxide material based on thermal decomposition in Example 1 is applied to the preparation of battery positive electrode materials and supercapacitor electrode materials.

[0053] Example 2: The present invention provides a technical solution: a method for preparing a high-conductivity lithium nickel manganese oxide material based on a thermal decomposition method, comprising the steps of:

[0054] S1: Prepare nickel-manganese-lithium salt solution with a molar concentration of 1.0-2.5 mol / L. Dissolve nickel source, manganese source and lithium source in a solvent according to a stoichiometric ratio and stir until completely dissolved to form a uniform nickel-manganese-lithium salt solution;

[0055] S2: First spray pyrolysis, introducing the uniformly mixed nickel-manganese-lithium salt solution into a spray pyrolysis furnace and treating it using a single-stage spray pyrolysis or a two-stage spray pyrolysis process to generate a nickel-manganese oxide precursor product;

[0056] S3: Heat treatment of the intermediate product: the cracked product is introduced into a sintering kiln and kept at 750-980°C for 6-20 hours, then cooled to 500-650°C at a cooling rate of 5°C / min and kept at this temperature for 3-6 hours to allow the product to fully crystallize and form nickel-manganese oxide;

[0057] S4: Carbon-coated secondary pyrolysis: The nickel-manganese oxide prepared in step S3 is mixed with a carbon source and introduced into a spray pyrolysis furnace for secondary spray pyrolysis under nitrogen protection. The secondary pyrolysis temperature is 300-850°C to form a carbon-coated hollow spherical crude product;

[0058] S5: Post-processing and screening: the treated crude product is naturally cooled to room temperature, and sieved to obtain a hollow spherical lithium nickel manganese oxide material with uniform particle size distribution.

[0059] In this embodiment, in step S1, the nickel source is at least one or more combinations of nickel sulfate, nickel acetate, nickel chloride, and nickel hydroxide; the manganese source is at least one or more combinations of manganese sulfate, manganese acetate, and manganese chloride; the lithium source is at least one or more combinations of lithium carbonate, lithium acetate, and lithium hydroxide; and the solvent is at least one or more combinations of deionized water, ethanol, or isopropanol.

[0060] In this embodiment, the single-stage spray cracking in step S2 refers to performing cracking spray at 500-980° C. with a spray time of 2-30 seconds.

[0061] In this embodiment, the two-stage spray pyrolysis in step S2 is first performed at 700-980 ° C. High-frequency resonance spraying (frequency 50-200 Hz) is carried out, and the droplets are forced to vibrate to form a porous structure, and the pyrolysis time is 5-15 s; the pyrolysis product is introduced into a sintering kiln, kept at 750 ° C.-980 ° C. for 6-20 hours, and then quickly cooled to 500-650 ° C., and water vapor is introduced for surface hydroxylation modification.

[0062] In this embodiment, the carbon source in step S4 is any one or more combinations of graphene, carbon nanotubes, carbon black, and organic carbon sources, and the carbon content of the carbon source before carbon coating in S4 is 0.01%-0.5%.

[0063] In this embodiment, the hollow spherical lithium nickel manganese oxide material prepared in step S5 has a particle size of 10 μm and a carbon content of 0.3%.

[0064] Example 2 discloses a method for preparing a high-conductivity lithium nickel manganese oxide material based on thermal cracking. By flexibly selecting between single-stage and two-stage processes in the initial spray thermal cracking process and synergizing it with a carbon-coated secondary cracking process, precise control of the microstructure and electrochemical properties of the lithium nickel manganese oxide material is achieved. Single-stage spray cracking rapidly forms a nickel manganese oxide precursor, while two-stage spray cracking imparts unique properties to the precursor by forming a porous structure through high-frequency resonant spraying and combining surface hydroxylation modification. The carbon-coated secondary cracking further enhances the material's electronic conductivity.

[0065] The method for preparing high-conductivity lithium nickel manganese oxide material based on thermal decomposition in Example 2 is applied to the preparation of battery positive electrode materials and supercapacitor electrode materials.

[0066] Example 3: The present invention provides a technical solution: a method for preparing a high-conductivity lithium nickel manganese oxide material based on a thermal cracking method, comprising the steps of:

[0067] S1: Prepare nickel-manganese-lithium salt solution with a molar concentration of 1.0-2.5 mol / L. Dissolve nickel source, manganese source and lithium source in a solvent according to a stoichiometric ratio and stir until completely dissolved to form a uniform nickel-manganese-lithium salt solution;

[0068] S2: First spray pyrolysis, introducing the uniformly mixed nickel-manganese-lithium salt solution into a spray pyrolysis furnace and treating it using a single-stage spray pyrolysis or a two-stage spray pyrolysis process to generate a nickel-manganese oxide precursor product;

[0069] S3: Heat treatment of the intermediate product: introducing the cracked product into a sintering kiln, keeping it at 750-980°C for 6-20 hours, cooling it to 500-650°C at a cooling rate of 5°C / min, and keeping it at that temperature for 3-6 hours to allow the product to fully crystallize and form nickel-manganese oxide;

[0070] S4: Carbon-coated secondary pyrolysis: The nickel-manganese oxide prepared in step S3 is mixed with a carbon source and introduced into a spray pyrolysis furnace for secondary spray pyrolysis under nitrogen protection. The secondary pyrolysis temperature is 300-850°C to form a carbon-coated hollow spherical crude product;

[0071] S5: femtosecond laser scanning of the hollow spherical crude product;

[0072] S6: Post-processing and screening: the crude product after femtosecond laser treatment is naturally cooled to room temperature, and sieved to obtain a hollow spherical lithium nickel manganese oxide material with uniform particle size distribution.

[0073] In this embodiment, in step S1, the nickel source is at least one or more combinations of nickel sulfate, nickel acetate, nickel chloride, and nickel hydroxide; the manganese source is at least one or more combinations of manganese sulfate, manganese acetate, and manganese chloride; the lithium source is at least one or more combinations of lithium carbonate, lithium acetate, and lithium hydroxide; and the solvent is at least one or more combinations of deionized water, ethanol, or isopropanol.

[0074] In this embodiment, the atomization method of the spray cracking in step S2 and step S4 is centrifugal atomization or pressure atomization, the atmosphere in the spray cracking furnace in step S2 is air, oxygen or a mixture of air and oxygen, and the atmosphere in the sintering kiln in step S3 is air, oxygen or a mixture of air and oxygen.

[0075] In this embodiment, the carbon source in step S4 is any one or more combinations of graphene, carbon nanotubes, carbon black, and organic carbon sources, and the carbon content of the carbon source before carbon coating in S4 is 0.01%-0.5%.

[0076] In this embodiment, the carbon source is added by direct mixing or pre-dispersing in a solvent to form a carbon source solution and then mixing.

[0077] In this embodiment, step S5 specifically includes: using a femtosecond laser with a wavelength of 800nm ​​and a pulse width of 50fs to scan the hollow spherical crude product at a scanning speed of 100-500mm / s. During the laser scanning process, high-energy laser pulses act on the surface of the material, which can break some chemical bonds on the surface of the material, thereby introducing oxygen vacancies and lattice distortion, and further optimizing the electrochemical properties of the material.

[0078] In this embodiment, the hollow spherical lithium nickel manganese oxide material prepared in step S6 has a particle size of 8 μm and a carbon content of 0.2%.

[0079] Example 3 discloses a method for preparing a high-conductivity lithium nickel manganese oxide material based on thermal cracking. This method achieves in-depth optimization of the structure and performance of the lithium nickel manganese oxide material by flexibly selecting between single-stage and two-stage processes in the first spray thermal cracking process and coordinating it with a femtosecond laser scanning process. Femtosecond laser scanning applies high-energy laser pulses with a wavelength of 800 nm, a pulse width of 50 fs, and a scanning speed of 100-500 mm / s to the surface of the hollow spherical crude product, breaking some chemical bonds, introducing oxygen vacancies and lattice distortion, and further optimizing the electrochemical properties of the material.

[0080] The method for preparing high-conductivity lithium nickel manganese oxide material based on thermal decomposition in Example 3 is applied to the preparation of battery positive electrode materials and supercapacitor electrode materials.

[0081] Comparative example: Preparation method: Lithium nickel manganese oxide material is prepared by traditional solid-phase reaction method. Nickel sulfate and manganese sulfate are accurately weighed according to the stoichiometric ratio to form a solution, and nickel manganese hydroxide is formed by co-precipitation method. Lithium carbonate and hydroxide precursor are fully mixed in a mortar according to a certain proportion, and then placed in a muffle furnace, heated to 750°C at a heating rate of 5°C / min, and kept warm for 4 hours for pre-burning to allow the raw materials to react initially. After the pre-burning is completed, the product is taken out and ground evenly again, put back into the muffle furnace, heated to 950°C at the same heating rate, and kept warm for 14 hours for high-temperature sintering to allow the reaction to proceed fully, thereby obtaining the final product, lithium nickel manganese oxide material.

[0082] See also Figure 1 The performance of the battery positive electrode materials prepared in Examples 1-3 and the comparative example was compared. The comparison tests included conductivity, power characteristics and cycle stability. The table is as follows:

[0083]

[0084]

[0085] As can be seen from the examples, the hollow spherical lithium nickel manganese oxide material prepared by the thermal decomposition method of the present invention is significantly superior to that prepared by the traditional solid-phase method in terms of conductivity, crystal structure, surface morphology and electrochemical performance.

[0086] The embodiments of the present invention are provided for the purpose of illustration and description. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present invention. Any changes, modifications, replacements and variations of the above embodiments by ordinary technicians in this field within the scope of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing high-conductivity lithium nickel manganese oxide material based on thermal cracking, characterized in that: Including steps: S1: Prepare nickel-manganese-lithium salt solution with a molar concentration of 1.0-2.5 mol / L. Dissolve nickel source, manganese source and lithium source in a solvent according to a stoichiometric ratio and stir until completely dissolved to form a uniform nickel-manganese-lithium salt solution; S2: First spray pyrolysis, introducing the uniformly mixed nickel-manganese-lithium salt solution into a spray pyrolysis furnace and treating it using a single-stage spray pyrolysis or a two-stage spray pyrolysis process to generate a nickel-manganese oxide precursor product; S3: Heat treatment of the intermediate product: introducing the cracked product into a sintering kiln, keeping it at 750-980°C for 6-20 hours, cooling it to 500-650°C at a cooling rate of 5°C / min, and keeping it at that temperature for 3-10 hours to allow the product to fully crystallize and form nickel-manganese oxide; S4: Carbon-coated secondary pyrolysis: The nickel-manganese oxide prepared in S3 is mixed with a carbon source and introduced into a spray pyrolysis furnace for secondary spray pyrolysis under nitrogen protection. The secondary pyrolysis temperature is 300-850°C to form a carbon-coated hollow spherical crude product; S5: femtosecond laser scanning of the hollow spherical crude product; S6: Post-processing and screening: the crude product after femtosecond laser treatment is naturally cooled to room temperature, and sieved to obtain a hollow spherical lithium nickel manganese oxide material with uniform particle size distribution.

2. The method for preparing a high-conductivity lithium nickel manganese oxide material based on a thermal cracking method according to claim 1, characterized in that: The nickel source in S1 is at least one or more combinations of nickel sulfate, nickel acetate, nickel chloride, and nickel hydroxide; the manganese source is at least one or more combinations of manganese sulfate, manganese acetate, and manganese chloride; the lithium source is at least one or more combinations of lithium carbonate, lithium acetate, and lithium hydroxide; and the solvent is at least one or more combinations of deionized water, ethanol, or isopropanol.

3. The method for preparing high-conductivity lithium nickel manganese oxide material based on thermal decomposition according to claim 1, characterized in that: The atomization method of the spray cracking in S2 and S4 is centrifugal atomization or pressure atomization. The atmosphere in the spray cracking furnace in S2 is air, oxygen or a mixture of air and oxygen. The atmosphere in the sintering furnace in S3 is air, oxygen or a mixture of air and oxygen.

4. The method for preparing a high-conductivity lithium nickel manganese oxide material based on a thermal cracking method according to claim 1, characterized in that: The single-stage spray cracking process in S2 refers to cracking spraying at 500-980° C. with a spraying time of 2-30 seconds.

5. The method for preparing high-conductivity lithium nickel manganese oxide material based on thermal decomposition according to claim 1, characterized in that: The two-stage spray cracking process in S2 is to first perform high-frequency resonance spraying at 700-980°C, and the droplets are forced to vibrate to form a porous structure, and the cracking time is 5-15s; the cracked product is introduced into a sintering kiln, kept at 750-980°C for 6-20h, and then quickly cooled to 500-650°C, and water vapor is introduced for surface hydroxylation modification.

6. The method for preparing high-conductivity lithium nickel manganese oxide material based on thermal decomposition according to claim 1, characterized in that: The carbon source in S4 is any one or more combinations of graphene, carbon nanotubes, carbon black, and organic carbon sources. The carbon content of the carbon source in S4 before carbon coating is 0.01%-0.5%.

7. The method for preparing a high-conductivity lithium nickel manganese oxide material based on a thermal cracking method according to claim 6, characterized in that: The carbon source is added by direct mixing or pre-dispersing in a solvent to form a carbon source solution and then mixing.

8. The method for preparing high-conductivity lithium nickel manganese oxide material based on thermal decomposition according to claim 1, characterized in that: The S5 specifically includes: using a femtosecond laser with a wavelength of 800 nm and a pulse width of 50 fs to scan the hollow spherical crude product at a scanning speed of 100-500 mm / s.

9. The method for preparing a high-conductivity lithium nickel manganese oxide material based on thermal decomposition according to claim 1, characterized in that: The hollow spherical lithium nickel manganese oxide material prepared in S6 has a particle size of 1-20 μm and a carbon content of 0.01%-0.5%.

10. Use of the method for preparing high-conductivity lithium nickel manganese oxide material based on thermal decomposition method according to any one of claims 1 to 9 in the preparation of battery positive electrode materials and supercapacitor electrode materials.

Images