306results about How to "Coated evenly" patented technology

The invention discloses a composite positive electrode material and a preparation method thereof, a positive plate and a lithium ion battery. The composite positive electrode material comprises lithium iron phosphate and a carbon coating layer coating the surface of the lithium iron phosphate, wherein the integral intensity ratio ID / IG of a D peak to a G peak of the carbon coating layer in a Raman spectrum is 0.2-0.9, and the resistivity of the composite positive electrode material is 0.1-10 omega.cm. According to the preparation method, the graphitization degree of the carbon coating layer is controlled within a proper range (ID / IG is 0.2-0.9), so that good conductivity is ensured, and structural instability caused by excessive graphitization is avoided. The moderate graphitization degree is beneficial to formation of an ordered carbon layer structure, provides more electron transport channels and reduces the potential barrier of electron migration, so that the conductivity of the composite material is greatly improved, and the resistivity is reduced to an excellent level of 0.1-10 omega.cm.

The invention discloses an efficient chemical liquid phase coating method of metal soft magnetic powder and application, and belongs to the technical field of preparation of soft magnetic materials, aluminum isopropoxide is dissolved to form a coating precursor solution, and an Al2O3 insulation coating layer is formed on the surface of the fluidized metal soft magnetic powder after hydrolysis and dehydration reactions. The aluminum isopropoxide is dissolved to form gel, the gel is uniformly mixed with the fluidized metal soft magnetic powder, dried gel can be formed on the surface of the metal soft magnetic powder after high-temperature airflow drying, and the dried gel is further calcined and dehydrated to form the high-insulativity Al2O3 coated metal soft magnetic powder. The method can be widely applied to surface insulation coating of the metal soft magnetic powder, has the characteristics of controllable coating layer thickness, simplicity, rapidness and high coating efficiency, and meets the requirements of industrial production such as large-scale, low-cost, safe and environment-friendly industrial production.

The invention belongs to the technical field of batteries, and particularly relates to a lithium ferrite lithium supplement agent and a preparation method and application thereof. Compared with the prior art, a solid electrolyte coating layer is formed on the surface of the carbon-doped lithium iron oxide material through a low-temperature molten salt method, so that air can be effectively isolated, the air stability of the material is improved, the lithium removal phenomenon is reduced, and the structural integrity and lithium supplement performance of the material are kept; and the lithium ferrite lithium supplement agent combines the high theoretical lithium supplement capacity of Li5FeO4 and the excellent ionic conductivity of the solid electrolyte, so that the electrochemical performance of the material can be improved while the high lithium supplement capacity is maintained, and a new technical scheme is provided for commercial application of the high-energy-density lithium ion battery.

The invention discloses a preparation method of a hard-soft carbon coated silicon-carbon negative electrode material, which comprises the following steps: S1, mixing nano silicon and graphite to obtain silicon-carbon mixed powder; s2, dissolving asphalt in absolute ethyl alcohol, then mixing with the silicon-carbon mixed powder, and carrying out carbonization treatment; s3, dissolving sucrose in water, then mixing with the composite material obtained in S2, and performing carbonization treatment to obtain a hard-soft carbon coated silicon carbon negative electrode material; wherein the carbonization temperature in the step 2 and the carbonization temperature in the step 3 are both 1200-1300 DEG C. According to the hard-soft carbon coated silicon-carbon negative electrode material and the preparation method thereof, the mixture of silicon and graphite is subjected to soft carbon coating and hard carbon coating through asphalt and cane sugar in sequence, so that the obtained hard-soft carbon coated silicon-carbon negative electrode material not only can inhibit volume expansion of silicon, but also shows excellent rate capability and cycle performance.

The invention provides a composite carbon source coated lithium iron phosphate material and a preparation method thereof, a lithium ion battery and electric equipment, and relates to the field of materials. The preparation method comprises the following steps: carrying out first mixing on iron phosphate, a lithium source, a first carbon source and a solvent, grinding to obtain slurry, and then carrying out spray drying to obtain a powder material; carrying out second mixing on the powder material and a second carbon source, and then sintering in an inert atmosphere to obtain a composite carbon source coated lithium iron phosphate material; the first carbon source comprises a small-molecule carbon source with the pyrolysis temperature not higher than 500 DEG C, and the second carbon source comprises a high-thermal-stability carbon source with the pyrolysis temperature not lower than 600 DEG C. According to the preparation method of the composite carbon source-coated lithium iron phosphate material provided by the invention, uniform coating of the lithium iron phosphate material is realized through cooperation of the first carbon source and the second carbon source, and the problem that the lithium iron phosphate cannot be uniformly coated by an existing carbon coating scheme after fusion-growth of the lithium iron phosphate is solved.

The invention discloses a ferric sodium pyrophosphate positive electrode material, a preparation method thereof and a battery, and relates to the technical field of batteries. Pre-sintering is performed; sanding and spray drying; and high-temperature sintering. Wherein the pH value of the reaction is controlled by using a Tris-HCl buffer solution in the hydrothermal reaction, so that the precursor is uniformly crystallized and has high crystallinity, and low-temperature segmented presintering is adopted later, so that the compaction density of the material can be controlled, and the related electrical properties of the material are relatively good. In the preparation process, a carbon source and a doping element are supplemented twice, so that carbon coating is uniform in the sintering process, the compaction density of the NFPP positive electrode material is further improved, the properties such as theoretical specific capacity of the positive electrode material are better through doping and carbon coating modification, and the high-compaction and high-capacity ferric sodium pyrophosphate positive electrode material is obtained.

The invention discloses core-shell type hydrophobic modified activated carbon and a preparation method thereof. The obtained hydrophobic activated carbon is composed of a core (activated carbon) and a shell (hydrophobic breathable silicon dioxide shell). The method comprises the following three steps: (1) constructing a silicon dioxide shell layer: dispersing pretreated activated carbon in a solvent, adding tetraethyl orthosilicate into the solvent, firstly adjusting the pH value of a reaction solution to be weakly acidic, stirring for 20-30 minutes under a certain stirring condition, then adjusting the pH value of the reaction solution to be weakly alkaline, continuously stirring for 0.5-1 hour to obtain a suspension A, and carrying out centrifugal drying treatment on the suspension A to obtain the silicon dioxide shell layer; an intermediate product coated with a hydrophilic silicon dioxide shell layer is obtained; (2) hydrophobic group grafting: dispersing the obtained intermediate product in a solvent, adding siloxane with different alkyl chain lengths into the solvent, fully stirring to obtain a suspension B, and performing centrifugal drying treatment to obtain hydrophobic modified activated carbon; cleaning and drying the hydrophobic modified activated carbon; and (3) adding a hydrophilic group: grafting the hydrophilic group on the silicon dioxide shell layer in an acid environment.

The invention discloses a membrane electrode for a fuel cell type H2 gas sensor and a preparation method thereof. The preparation method comprises: adding SnO2 powder or SnO2-Pd powder to a chloroplatinic acid solution and adding sodium citrate and stirring to obtain a substance A; adding a sodium borohydride alkaline solution to the substance A under ice-water bath conditions, heating in a water bath at 60-90°C for 1-2h to obtain a substance B; centrifuging and washing the substance B, and drying to obtain a target powder, wherein the target powder is Pt / SnO2 powder or Pt / SnO2-Pd powder, wherein Pt / SnO2 is SnO2 modified by Pt nanoparticles, and Pt / SnO2-Pd is SnO2-Pd modified by Pt nanoparticles, and the mass ratio of Pt to SnO2 in the target powder is in the range of #imgabs0#. After the target powder is configured into an electrode slurry, an electrode layer is prepared by using the electrode slurry and adhered to both sides of a Nafion membrane to form a membrane electrode. Assembling the membrane electrode into the fuel cell type H2 gas sensor structure can greatly improve the sensor's detection sensitivity to hydrogen and reduce the sensor's detection limit.

The invention provides a silicon carbon material with a multilayer coating structure and a preparation method and application thereof, and relates to the technical field of battery materials. The silicon-carbon material with the multi-layer coating structure comprises a porous carbon core body, and a first carbon layer and a second carbon layer which sequentially coat the porous carbon core body from inside to outside, and the porous carbon core body comprises porous carbon and nano silicon particles deposited on the surface and in pore channels of the porous carbon; and a conductive nano carbon filler is dispersed in the second carbon layer. The silicon carbon material with the multilayer coating structure provided by the invention is used as a lithium ion battery negative electrode material, and has excellent specific capacity, coulombic efficiency and cycle performance. The result of the embodiment shows that when the silicon carbon material with the multi-layer coating structure is applied to the lithium ion battery, the first reversible capacity is 1882-2071 mAh / g, the first coulombic efficiency is 92.6-94.1%, and the capacity retention ratio of 100 cycles is 95.3-97.7%.

The invention provides a zirconium boride / graphene complex-phase wear-resistant and high-temperature-resistant ceramic material and a preparation method thereof, and belongs to the technical field of ceramics. The preparation method comprises the following steps: pretreating graphene, preparing titanium dioxide / graphene microspheres, modifying the titanium dioxide / graphene microspheres, functionalizing the titanium dioxide / graphene microspheres, preparing a ceramic mixture, molding and sintering. The step of functionalizing the titanium dioxide / graphene microspheres comprises the following steps: putting the modified titanium dioxide / graphene microspheres into xylene, adding bisphenol A epoxy resin and triphenylphosphine, raising the temperature, carrying out stirring reaction, filtering out, washing, putting into N, N-dimethylformamide, uniformly stirring, adding gallic acid and p-toluenesulfonic acid, and carrying out ultrasonic treatment to obtain the titanium dioxide / graphene microspheres. Raising the temperature for reaction, filtering, washing and drying after the reaction is finished, so as to prepare functionalized titanium dioxide / graphene microspheres; the prepared ceramic material is high in strength, good in wear resistance and excellent in high temperature resistance.

The invention discloses a preparation method of a material capable of realizing tetracycline adsorption and visible light degradation, and belongs to the field of antibiotic wastewater treatment. According to the combined optimization method, three strategies of doping transition metal nickel on UIO-66, adjusting defects of a manufacturing frame by using monocarboxylic acid benzoic acid and compounding with a black phosphorus sheet layer to construct a heterojunction are implemented at the same time. The integrated nano material which has efficient adsorption performance on tetracycline and realizes photocatalytic removal under visible light is synthesized through a solvothermal method by orderly adding reactants, performing successive ultrasonic compounding and controlling the addition amount of the reactants. The prepared material has high adsorption capacity of 358mg g <-1 > on TC, and can remove more than 99% of the initial concentration of tetracycline hydrochloride after being irradiated and degraded by visible light.

The utility model discloses a high-temperature-resistant adhesive tape coating machine which comprises a machine frame, an unwinding roller, an adhesive tape guide roller A, an adhesive tape guide roller B, a coating assembly, a drying assembly and a winding roller, an adhesive tape base material is wound on the unwinding roller, and the unwinding roller and the winding roller are driven by a servo motor and installed on the top side and the bottom side of the machine frame respectively. The adhesive tape guide roller A, the coating assembly and the drying assembly are distributed on the inner side of the rack and are sequentially arranged in the direction from unwinding to winding of an adhesive tape base material. The coating assembly comprises a container and a coating roller, the container is provided with a central cavity, a tape inlet cavity and a tape outlet cavity, the central cavity is filled with glue, the coating roller is arranged in the central cavity, and an adhesive tape base material is guided into the container through an adhesive tape guide roller A after being unwound and extends out of the container through the tape inlet cavity, the central cavity and the tape outlet cavity in sequence; the adhesive tape guide roller B is connected between the coating assembly and the drying assembly, and the drying assembly comprises a hot air drying box and an anti-sticking guide roller set. The device is small in occupied area and has a glue solution steam recovery function.

The invention discloses a high-stability silicon monoxide lithium ion battery negative electrode material and a preparation method thereof. The preparation method comprises the following steps: carrying out hydrothermal reaction on modified silicon monoxide micro powder and chromium nitrate nonahydrate to obtain MOF / silicon monoxide composite powder, and mixing the MOF / silicon monoxide composite powder with carbon nanotubes to obtain powder to be carbonized; and carbonizing the powder to be carbonized in a tubular furnace, and fluorinating with fluorine gas to obtain the high-stability silicon monoxide lithium ion battery negative electrode material. According to the preparation method, Cr-MOF coating is generated on the surface of the silicon monoxide powder in situ, agglomeration of the silicon monoxide powder is reduced, carbon nanotubes are evenly attached to Cr-MOF and then heated and carbonized, the carbon nanotubes are cured by a carbonization layer formed at a high temperature, the combination degree of the carbon nanotubes, a carbon layer and silicon monoxide is high, and the silicon monoxide powder is prepared. And under the synergistic effect with carbon fluoride formed by fluorination of fluorine, the stability of the silicon monoxide lithium battery negative electrode material is improved, the expansion rate of silicon monoxide is reduced, and the cycling stability of a lithium ion battery is improved.

The invention discloses a non-contact stirring dry method electrode material fibration method and a prepared pole piece. The principle that centrifugal force generated by autorotation and convection shear force caused by revolution are adopted, so that materials are uniformly mixed and fiberized by a'twisting 'and'pulling' force field generated under the condition of speed difference. The binder and the conductive agent are stirred and mixed for the first time in a non-contact mode, and the binder is coated with the conductive agent in advance; carrying out secondary non-contact stirring and mixing on the coated binder and the active substance particles to obtain a uniformly mixed pre-fibration material; carrying out uniform fibration treatment on the pre-fibration material, and then carrying out step-by-step hot pressing to obtain a dry-method electrode membrane; and performing hot-pressing compounding on the electrode film and a current collector containing a conductive agent to prepare the dry-method electrode plate. According to the non-contact stirring dry method electrode material fibration method, the length of a production line is shortened; the production cost is greatly reduced; the electrochemical performance is improved; and large-scale batch production can be realized.

The invention provides a preparation method of a heteroatom-doped mesoporous carbon nanotube material and application of the heteroatom-doped mesoporous carbon nanotube material in a lithium-sulfur battery. The preparation method comprises the following steps: S1, preparing a polyphosphazene nanotube by utilizing a self-template method; s2, preparing PZS coated SiO2 by adopting a sol-gel method; s3, NPS-C coated SiO2 is prepared through carbonization; and S4, adding the NPS-C-coated SiO2 powder into an etching solution, stirring, centrifuging, washing, and finally performing vacuum drying at room temperature to obtain the NPS-C material. The NPS-C obtained by carbonizing the precursor prepared on the basis of a self-template method and a sol-gel method has excellent conductivity, the mesoporous hollow structure can be used as a sulfur species packaging framework to inhibit large volume fluctuation in the circulation process, heteroatoms can adsorb and fix polysulfide to effectively inhibit the shuttle effect, and the performance of the NPS-C is improved. And a new thought is opened up for exploration and design of the high-performance electrode material of the lithium-sulfur battery.

The invention relates to the field of aluminum-plastic composite belt processing equipment, and discloses an aluminum-plastic composite belt longitudinal wrapping machine which comprises a bearing assembly and an unwinding assembly, an aluminum-plastic composite belt is arranged between the bearing assembly and the unwinding assembly, the bottom of the unwinding assembly is connected with a base assembly, and an adjusting assembly is installed on the back face of the top of the base assembly. The front face of the adjusting assembly is connected with the bearing assembly, the head end of the aluminum-plastic composite belt is wound on the other side of the front face of the unwinding assembly, the unwinding assembly is used for conveying the tail end of the aluminum-plastic composite belt to the other side of the bearing assembly, and the adjusting assembly drives the bearing assembly to move up and down when moving. And therefore, machining tables with different heights can be adapted.

The invention discloses a graphene-coated hard carbon negative electrode material and a preparation method thereof, and belongs to the technical field of hard carbon negative electrode materials. The preparation method of the graphene-coated hard carbon negative electrode material comprises the following steps: carrying out pretreatment and three-step soaking on coconut shells, carrying out biomass carbonization, mixing with a microbial suspension, and adsorbing to obtain a microbial adsorption type hard carbon material; and then carrying out surface treatment, chemical vapor deposition, impregnation, secondary chemical vapor deposition and annealing treatment on the microbial adsorption type hard carbon material to obtain the graphene coated hard carbon negative electrode material. The negative electrode material prepared by the method is high in first discharge capacity, high in first coulombic efficiency and good in cycle performance.

The invention provides a flexible 3D printing material with a double-layer structure and a preparation method thereof.The flexible 3D printing material comprises a TPU coating layer and an inner-layer TPU composite material, the TPU coating layer is prepared from hard TPU, and the inner-layer TPU composite material is prepared from flexible TPU and a coupling agent used for improving the interface bonding strength between the flexible TPU and the coupling agent; the inner-layer TPU composite material further comprises a plasticizer, the plasticizer is used for improving the overall elongation at break of the material and reducing the hardness of the material, and the plasticizer is one or more of phthalate, terephthalate, succinate or isophthalate. According to the scheme, the outer layer material which is moderate in hardness, good in tensile strength and low in elongation at break is used for coating the inner layer flexible material which is high in elongation at break, so that the 3D printing material can be smoothly replaced in AMS, a flexible product can be smoothly printed by using FDM, and additional treatment is not needed.

The invention relates to the technical field of batteries, in particular to a composite positive electrode material and a preparation method and application thereof. The composite positive electrode material comprises a base material and a perovskite phase coating layer coating the surface of the base material, the chemical formula of the base material comprises LiNi < x > Co < y > Mn < 1-x-y-z > M < z > O < 2 >, 1, 0 < = y < lt >; 0 < = zlt; 0.2, x + y + zlt; 1, the chemical formula of the perovskite phase coating layer comprises AQO3, A is at least one of Ca, Sr and Ba, and Q is Ti or Zr. According to the composite positive electrode material, the uniform perovskite phase coating layer is arranged on the surface of the base material, so that the surface residual alkali can be remarkably reduced, the side reaction on the surface of the material is slowed down, and the thermal stability and the cycle performance of the composite positive electrode material are improved.

The invention discloses an oxidized crosslinked asphalt coated resin hard carbon negative electrode material and a preparation method thereof. The preparation method comprises the following steps: S1, pre-treating resin to obtain a resin precursor; s2, performing mechanical pulverization, low-temperature pre-carbonization and airflow pulverization treatment on the resin precursor to obtain low-temperature pre-carbonized ground powder; s3, the low-temperature pre-carbonized ground powder is subjected to activation pore forming and high-temperature carbonization treatment, and resin hard carbon is obtained; s4, uniformly mixing the resin hard carbon and the asphalt to obtain a mixture; s5, performing asphalt melting coating and low-temperature oxidation cross-linking treatment on the mixture to obtain oxidation cross-linked asphalt coated resin hard carbon; s6, performing high-temperature carbonization treatment on the oxidized cross-linked asphalt coated resin hard carbon to obtain coated hard carbon; and S7, carrying out post-treatment on the coated hard carbon to obtain the oxidized crosslinked asphalt coated resin hard carbon negative electrode material. The oxidized cross-linked asphalt coated resin hard carbon negative electrode material has a relatively low specific surface area, and the first reversible capacity and the initial coulombic efficiency of a battery can be remarkably improved.

The invention relates to a lanthanide perovskite type oxide coated high-nickel ternary positive electrode material and a preparation method thereof. The positive electrode material is spherical-like particles formed by coating a high-nickel ternary positive electrode material with a lanthanide perovskite type oxide coating layer according to a mass ratio of (0.01-0.03): 1; the chemical formula of the lanthanide perovskite type oxide is LazCa1-zCoO3, and z is more than 0 and less than or equal to 1; the chemical formula of the high-nickel ternary positive electrode material is LiNixCoyMn (1-x-y) O2, x is greater than or equal to 0.80 and less than or equal to 0.96, y is greater than or equal to 0.01 and less than or equal to 0.10, and 1-x-y is greater than 0. The preparation method comprises the following steps: ball-milling and mixing the lanthanide perovskite type oxide and the high-nickel ternary positive electrode material, and sintering at low temperature in a protective atmosphere. The positive electrode material is high in lithium ion and electron conductivity in the charging and discharging process, high in reversibility, stable in structure and good in rate capability and cycling stability. The method is simple, low in cost and suitable for industrial production.

The invention provides a halide solid-state electrolyte and a preparation method and application thereof. The halide solid-state electrolyte comprises a halide solid-state electrolyte inner core and a halide solid-state electrolyte outer core, and the hydrophobic layer is uniformly coated on the halide solid electrolyte core, and the hydrophobic layer comprises bis-hexadecyl phosphate. According to the halide solid electrolyte as well as the preparation method and the application thereof, the air stability of the halide solid electrolyte can be remarkably improved, the cycle performance of an all-solid-state lithium ion battery is improved, the manufacturing process is simple, and the cost is relatively low.

The invention relates to a lithium nickel manganese oxide coated high-nickel ternary positive electrode material and a preparation method thereof. The positive electrode material is spherical particles formed by coating a high-nickel ternary positive electrode material with a spinel type lithium nickel manganese oxide coating layer according to a mass ratio of (0.005-0.040): 1, the chemical formula of the high-nickel ternary positive electrode material is LiNixCoyMn (1-x-y) O2, x is larger than or equal to 0.75 and smaller than or equal to 0.90, y is larger than or equal to 0.05 and smaller than or equal to 0.15, and 1-x-y is larger than 0. The preparation method comprises the following steps: (1) adding a high-nickel ternary positive electrode material into an organic solution containing nickel, manganese and lithium, and stirring and mixing; (2) dropwise adding a precipitant organic solution, stirring for reaction, heating and stirring until evaporation to dryness, and grinding; and (3) sintering and cooling in an oxidizing atmosphere. The positive electrode material disclosed by the invention is highly reversible in charge-discharge reaction, stable in structure and good in rate capability and cycling stability. The method is simple, short in process, good in coating effect, low in cost and suitable for industrial production.

The invention discloses a roll coating robot with curved surface self-adaption capability, and relates to the technical field of roll coating equipment, a roll coating mechanism comprises a mounting frame, a plurality of self-adaption roll coating units are fixedly mounted at the bottom of the mounting frame, each self-adaption roll coating unit comprises an adjusting frame, and a roller frame is slidably connected to the bottom of each adjusting frame; coating rollers are rotationally connected to the two sides of the roller frame, a linear motor is fixedly mounted in the middle of the inner wall of the adjusting frame, an adjusting rod is fixedly connected to the output end of the linear motor, and an adjusting groove is formed in the bottom of the adjusting rod; according to the self-adaptive roller coating equipment, an integrated coating roller in common roller coating equipment is divided into a plurality of self-adaptive roller coating units which act independently, and the coating rollers are driven by the linear motors to realize self-adaptive lifting motion, so that enough contact pressure between each coating roller and an object to be subjected to roller coating is ensured; therefore, the coating requirements of different curved surface shapes and positions are met.

The invention belongs to the related technical field of carbon materials and batteries, and particularly relates to a preparation method of a carbon-coated graphite composite material, the carbon-coated graphite composite material and a battery negative electrode. A preparation method of a carbon-coated graphite composite material comprises the following steps: mixing an alkaline mixed solution containing a graphite material, a main carbon source for coating, a synergistic carbon source for coating and an auxiliary agent to obtain a dispersion liquid; performing drying and coking treatment on the dispersion liquid under a preset condition to form a carbon-coated graphite precursor; carrying out carbonization treatment on the carbon-coated graphite precursor under a protective gas environment condition to obtain a carbon-coated graphite composite material; the main carbon source for coating comprises saccharides; the synergistic carbon source for coating comprises a compound containing non-carbon heteroatoms; and the auxiliary agent comprises a surfactant, can be in synergistic effect with the synergistic carbon source for coating, and can fully disperse the alkaline mixed solution to obtain a uniformly distributed dispersion solution.

The invention discloses a method for regenerating a lithium iron phosphate positive electrode material from waste lithium iron phosphate battery black powder, and belongs to the technical field of waste lithium ion battery recovery. According to the method, the black powder of the waste lithium iron phosphate battery is subjected to wet leaching, a lithium iron phosphate precursor is prepared through a one-step hydrothermal method after deep impurity removal of a leaching solution, and finally modified lithium iron phosphate is prepared through high-temperature roasting. According to the method disclosed by the invention, the lithium iron phosphate positive electrode material can be regenerated only through a hydrothermal method, and lithium iron phosphate and carbon are uniformly compounded after carbonization roasting. The modified lithium iron phosphate is used as a lithium ion battery positive electrode material, the electrical property is excellent, the 0.1 C discharge specific capacity is 159.21 mAh / g, and the 1 C discharge specific capacity can reach 145.33 mAh / g. The main raw material involved in the invention comes from the waste lithium iron phosphate battery, so that the production cost of lithium iron phosphate can be effectively reduced, and waste battery resource circulation and environment-friendly utilization are realized.

The invention provides a grain boundary coating method of a polycrystalline positive electrode material and a grain boundary coated polycrystalline positive electrode material.The grain boundary coating method of the polycrystalline positive electrode material comprises the following steps that the polycrystalline positive electrode material is placed in a furnace tube of a tube furnace to be heated, and a gas-phase reaction source diffuses into the polycrystalline positive electrode material along a grain boundary under the action of airflow pressure, the gas-phase reaction source reacts on the surface and the grain boundary of the polycrystalline positive electrode material, so that a coating layer is formed on the surface and the grain boundary of the polycrystalline positive electrode material, and the grain boundary coated polycrystalline positive electrode material is obtained. According to the method, the gas-phase reaction source is subjected to chemical reaction on the surfaces of the primary particles of the polycrystalline positive electrode material to form the required grain boundary coating layer, so that the defects of non-uniform coating, incapability of directly coating the primary particles and the like in the prior art are overcome.

The invention discloses a ternary positive electrode material, a preparation method thereof and an electrochemical device, and the preparation method of the ternary positive electrode material provided by the embodiment of the invention comprises the following steps: mixing a ternary positive electrode material precursor with a lithium source, and carrying out primary sintering to obtain an inner core; mixing the inner core with a lithium hydroxide solution in a spray coating manner to obtain a first mixture with a lithium hydroxide inner coating layer; mixing the first mixture with a phosphoric acid solution in a spray coating manner to obtain a second mixture with a phosphoric acid outer coating layer; the second mixture is subjected to secondary sintering, a coating layer containing lithium phosphate is formed on the surface of the inner core, the ternary positive electrode material is obtained, and the concentration gradient of lithium ions in the coating layer is gradually increased from the outside to the inside of the coating layer in the radial direction. The ternary positive electrode material prepared by adopting a step-by-step wet spraying coating mode shows excellent rate capability, cycle performance and structural stability.

The invention belongs to the technical field of negative electrode materials, and particularly relates to a graphite coating method. By adopting a three-step method of low-temperature softening, aqueous solution washing and high-temperature carbonization, the staged control of the contents of the three components in the working procedures is realized, and the content of each component of the asphalt in each working procedure is always in the optimal ratio. According to the invention, the uniformity in the coating process can be ensured, the coking value can be increased, and the hardening degree of the material can be reduced, and the adopted aqueous solution detergent can also ensure the full reaction of the organic polymer material and the components in the asphalt, and does not remain in the graphite material, so that the negative gain effect is avoided. The method disclosed by the invention is simple in process flow, low in volatile pollutant emission, low in production cost and suitable for large-scale industrialization.

The invention discloses a high-voltage lithium manganese iron phosphate positive electrode material as well as a preparation method and application thereof, and belongs to the technical field of lithium battery materials. The preparation method comprises the following steps: 1) preparing a mixed solution containing a soluble phosphate compound, soluble bivalent iron salt and soluble bivalent manganese salt; 2) adding a high-boiling-point organic solvent; 3) dropwise adding the lithium hydroxide solution into the mixed solution step by step, carrying out solvothermal reaction under the normal pressure condition, filtering, washing and drying; 4) spray drying and high-temperature calcination treatment; according to the method, the rice-grain-shaped lithium manganese iron phosphate nano-particles with the nano-scale particle size, uniform distribution, good crystallinity and high purity can be successfully prepared under normal pressure, the lithium manganese iron phosphate positive electrode material synthesized by adopting the nano-particles as the precursor can maintain high discharge voltage, so that the energy density of a battery is improved, the synthesis process is simple and novel, and the method is suitable for industrial production. The safety and reliability are high.