1261 results about "Manganese phosphate" patented technology

The invention discloses a modified carbon-coated sodium manganese ferric phosphate pyrophosphate / sodium ferric phosphate pyrophosphate positive electrode material as well as a preparation method and application thereof, and relates to the technical field of new energy materials. The preparation method comprises the following steps: preparing MnFe-MOF from a manganese source, a first iron source and a first organic ligand under a hydrothermal reaction; a second iron source, the MnFe-MOF and a second organic ligand are subjected to a hydrothermal reaction, and MnFe-MOF / Fe-MOF is obtained; uniformly mixing with a sodium source and a phosphorus source, and sintering to obtain a positive electrode material; and carrying out high-temperature gas-phase etching treatment to obtain the fluorine-doped carbon-coated modified sodium manganese ferric phosphate pyrophosphate / sodium ferric phosphate pyrophosphate positive electrode material. The material disclosed by the invention has a coating modified structure, so that an interface side reaction caused by direct contact between sodium ferromanganese phosphate and an electrolyte can be effectively avoided, a manganese dissolution phenomenon is reduced, and the structural stability of the material is improved; and meanwhile, the material has high conductivity, excellent structural stability, excellent long cycle life and excellent rate capability.

The invention relates to a positive electrode active material, a preparation method, a battery monomer, a battery device and a power utilization device. The positive electrode active material comprises an inner core and a first coating layer arranged on at least part of the surface of the inner core, the inner core comprises lithium manganese iron phosphate; the first coating layer comprises lithium iron phosphate; an X-ray diffraction pattern of the positive electrode active material comprises a diffraction peak of a (020) crystal face and a diffraction peak of a (200) crystal face, the diffraction peak of the (020) crystal face and the diffraction peak of the (200) crystal face meet the condition that I (020) / I (200) is larger than or equal to 3.5, I (020) represents the intensity of the diffraction peak of the (020) crystal face, and I (200) represents the intensity of the diffraction peak of the (200) crystal face. The positive electrode active material provided by the embodiment of the invention has good lithium ion diffusion performance, and when the positive electrode active material is used for a battery, the battery can have good rate capability.

The invention discloses a method for regenerating waste lithium iron phosphate into a lithium manganese iron phosphate positive electrode material under assistance of element doping. According to the method, the waste lithium iron phosphate is successfully regenerated into the lithium manganese iron phosphate material with excellent performance through solid-phase sintering and element doping. Compared with a traditional repairing and regenerating method, the method has the advantages that upgrading and regenerating of the waste lithium iron phosphate are realized, and the market competitiveness of regenerated products is improved. Compared with other methods, the method does not need an acid leaching step, and the recovery process is simpler and more environment-friendly. And an element doping modification means is introduced, so that the performance of the regenerated lithium manganese iron phosphate material is further improved. The invention aims to provide a green, efficient and high-valued method for upgrading and regenerating the waste lithium iron phosphate positive electrode material into the lithium iron manganese phosphate positive electrode material with industrial application prospects.

The invention provides a method for preparing a high-performance lithium manganese iron phosphate positive electrode material based on a manganese iron phosphate precursor, and relates to the technical field of batteries. A method for preparing a high-performance lithium manganese iron phosphate positive electrode material based on a manganese iron phosphate precursor comprises the following steps: S1, mixing a phosphorus source, an iron source and a manganese source in a water medium, adding a surfactant, and carrying out ball milling, drying and sintering to obtain the manganese iron phosphate precursor; and S2, mixing the manganese iron phosphate precursor, a lithium source, a carbon source, a doping agent, an auxiliary agent and deionized water, and carrying out ball milling, drying and sintering to obtain the lithium manganese iron phosphate positive electrode material. The method can improve the surface / interface stability while improving the surface conductivity of the material, thereby prolonging the cycle life of the battery and improving the charge-discharge capacity of the battery.

The invention provides a composite lithium manganese iron phosphate positive electrode material and a preparation method and application thereof, the preparation method comprises the following steps: (1) mixing a lithium source, an iron source, a manganese source, a phosphorus source, a fluxing agent, a dispersing agent and a solvent to obtain mixed slurry, spray-drying the mixed slurry, and calcining to obtain a lithium manganese iron phosphate intermediate; and (2) mixing the lithium iron manganese phosphate intermediate, a lithium source, a dispersing agent and a solvent to obtain mixed slurry, performing spray drying on the mixed slurry, and performing calcination treatment to obtain the composite lithium iron manganese phosphate positive electrode material. According to the method, the lithium iron manganese phosphate positive electrode material is prepared in a sectional manner, and the lithium iron manganese phosphate positive electrode material which is compact in structure, good in structural stability, high in grain strength, uniform in particle size distribution and high in compaction density can be prepared by adjusting the adding types of the materials and the adding amount of each section.

The invention discloses a metal composite lithium iron phosphate solid-phase deposition coated lithium manganese iron phosphate positive electrode material and a preparation method thereof, and belongs to the technical field of lithium ion battery positive electrode materials. The preparation method of the metal composite lithium iron phosphate solid-phase deposition coated lithium iron manganese phosphate positive electrode material comprises the following steps: S1, preparing a lithium iron manganese phosphate material and sintering; s2, grinding lithium iron phosphate into nano particles, and mixing the nano particles with a sugar source to form lithium iron phosphate nano slurry; s3, transferring into a CVD (Chemical Vapor Deposition) fluidized bed in the lithium manganese iron phosphate cooling and sintering stage, spraying lithium iron phosphate nano slurry, gasifying and drying the lithium iron phosphate material, and coating the surface of the lithium manganese iron phosphate with the lithium iron phosphate material through solid-phase deposition; and S4, carrying out composite coating of carbon and metal oxide on the lithium manganese iron phosphate coated with the lithium iron phosphate to obtain the lithium manganese iron phosphate coated with the lithium iron phosphate. According to the invention, the problem of poor uniformity of lithium iron phosphate coated lithium iron manganese phosphate is solved, the electrical property of lithium iron manganese phosphate is improved, the ferromanganese dissolution is improved, and the cycle performance is improved.

The invention discloses a high-density lithium manganese iron phosphate positive electrode material and a preparation method thereof.The preparation method of the high-density lithium manganese iron phosphate positive electrode material comprises the following steps that 1, an iron source, a lithium source, a manganese source, a phosphorus source, an additive, a dispersing agent and a carbon source are added into deionized water, grinding, drying and sintering are conducted, and a primary material is obtained; and 2, coating the primary material with a polydopamine layer, and sintering to obtain the high-density lithium iron manganese phosphate positive electrode material, wherein the dispersing agent is polyethylene glycol tert-octyl phenyl ether; the carbon source is polyvinyl alcohol and at least one of glucose, carbon nanotubes and graphene; the additive is at least one of magnesium oxide and silicon oxide. The high-density lithium manganese iron phosphate positive electrode material disclosed by the invention has relatively good electrical performance and compaction density, and a battery prepared from the high-density lithium manganese iron phosphate positive electrode material has good electrochemical performance.

The invention belongs to the technical field of lithium ion battery positive electrode materials, and provides a double-layer coated lithium iron manganese phosphate positive electrode material, which comprises a lithium iron manganese phosphate positive electrode material, and an organic carbon source coating layer and a modified carbon nanotube coating layer which coat the surface of the lithium iron manganese phosphate positive electrode material from inside to outside. Firstly, an organic carbon source is adopted to perform primary carbon coating on lithium manganese iron phosphate to form a carbon core-shell composite structure, and then modified carbon nanotubes are utilized to perform secondary coating to obtain the double-layer coated lithium manganese iron phosphate positive electrode material, so that organic-inorganic dual coating is realized, the electronic conductivity of the material can be effectively improved, and the performance of the material is improved. And the condition that the lithium manganese iron phosphate is directly contacted with the electrolyte to reduce the dissolution of Mn can be avoided, so that the cycle performance of the positive electrode material is improved, and the preparation process is simple in process, easy to operate and suitable for large-scale production.

The invention discloses a manganese hydrogen phosphate precursor, lithium iron manganese phosphate, a preparation method of the manganese hydrogen phosphate precursor, a positive pole piece containing the lithium iron manganese phosphate, a battery containing the lithium iron manganese phosphate, and an electric device containing the lithium iron manganese phosphate. The preparation method comprises the following steps: firstly, carrying out primary precipitation reaction on soluble manganese salt and a precipitator to prepare manganese hydroxide, and then carrying out secondary precipitation reaction on the manganese hydroxide and phosphoric acid to prepare the manganese hydrogen phosphate precursor. The manganese hydrogen phosphate precursor with low impurity ion content and high yield is prepared through secondary precipitation reaction.

The present invention discloses a method for producing manganese monohydrogen phosphate trihydrate, a method for recycling Mn-containing mother liquor, and a cathode material, relating to the technical field of lithium-ion batteries. In the present invention, a solid manganese carbonate slurry is used as a bottom liquid to synthesize manganese monohydrogen phosphate. Through precipitation solid-phase transformation, an octahedral morphology feature is constructed, which has a larger specific surface area. During the subsequent synthesis of lithium iron manganese phosphate, it helps to improve the reactivity of Mn and form a more uniform lithium iron manganese phosphate cathode material, thereby improving the compaction capacity and electrochemical performance of the cathode material.

The invention relates to the technical field of electrode materials, and discloses a preparation method of a lithium iron manganese phosphate material and a lithium ion battery. The lithium iron manganese phosphate material is prepared by the following steps: performing in-situ growth in a cavity of polyethylene glycol-sucrose hybrid aerogel with a three-dimensional porous network structure to form a manganese iron phosphate precursor; the hybrid aerogel can control excessive agglomeration and disordered growth of ferromanganese phosphate precursor particles and avoid particle agglomeration, so that the finally formed lithium ferromanganese phosphate material particles are finer and more uniformly distributed, and an amorphous carbon-aluminum layer is formed during later calcination, so that the performance of the material is improved. The surface of lithium manganese iron phosphate particles is tightly coated with the composite material, electron transmission can be accelerated, particle pulverization can be reduced, meanwhile, corrosion of corrosive components in electrolyte can be inhibited, interface side reactions such as transition metal ion dissolution can be reduced, and finally the conductivity and cycling stability of the lithium ion battery are remarkably improved.

The invention discloses a preparation method of a high-capacity lithium iron manganese phosphate cathode material. In the method of the invention, by doping nickel and modifying polyethylene glycol, the intrinsic conductivity of the material is improved. At the same time, the lattice distortion caused by doping inhibits the growth of grains, improves the grading of particles, shortens the diffusion path of lithium ions. Meanwhile, nickel in nickel and fluorine modified polyethylene glycol can form nickel oxide on the surface of carbon sources such as carbon black or carbon fiber, which promotes the electron and ion transport between the cathode material and the electrolyte to a certain extent, improves the energy density and cycle performance of the battery. Fluorine can improve the interfacial composition between the carbon source and the cathode material, promote the transfer and diffusion of lithium ions, and improve the charge / discharge rate and capacity retention of the battery. Therefore, doping nickel and modifying polyethylene glycol in the invention have a synergistic effect. Especially when the molar amount of doped nickel is 0.02, the prepared battery has a high capacity and excellent rate performance.

The invention provides a lithium manganese iron phosphate positive electrode material and a preparation method and application thereof. The method comprises the following steps: mixing manganese metal and iron metal, heating, melting and uniformly mixing in an inert gas atmosphere, and grinding into powder; adding an ammonium salt solution, continuously adding the ground manganese-iron alloy powder under heating to form a suspension, introducing compressed air and stirring, reacting, filtering, washing, drying, crushing and grinding to obtain a manganese-iron oxide precursor, feeding the manganese-iron oxide precursor, a lithium source, a phosphorus source and doped metal elements into pure water, adding a carbon source, mixing to form a suspension, and grinding and drying to obtain the lithium-phosphorus-doped manganese-iron composite material. And carrying out carbon thermal reduction in an inert gas atmosphere, and crushing to obtain the lithium manganese iron phosphate positive electrode material. The ferromanganese oxide precursor prepared by heating the metal manganese and the metal iron to a molten state and mixing the metal manganese and the metal iron realizes uniform dispersion of the manganese and the iron at an atomic level, avoids the problems of nonuniform mixing of the manganese and the iron and dissolution of the manganese, and improves the conductivity and the electrochemical performance of the material.

The invention relates to the technical field of lithium batteries, in particular to a magnesium-doped and carbon nanotube dual-modified lithium manganese iron phosphate material and a preparation method thereof. The method comprises the following steps: preparing a mixed solution from a magnesium source component, a phosphorus source component, a manganese source component, an iron source component and a lithium source component, mixing the mixed solution with a carbon nanotube, and carrying out a hydrothermal reaction to generate the lithium iron manganese phosphate material in situ. According to the method, Mg < 2 + > doping optimizes the bulk phase structure stability of the material, relieves lattice stress and improves the lithium ion diffusion rate, a three-dimensional conductive network constructed by CNTs connects internal particles of agglomerated particles to make contact with the outside, and the internal particles and the outside synergistically reduce polarization and improve the rate performance; the material has less capacity attenuation and higher coulombic efficiency, and also has a good lithium ion transmission effect, and the capacity is greatly improved.

The invention discloses a lithium iron manganese phosphate positive electrode material and a preparation method thereof, a positive electrode plate and a secondary battery, and belongs to the technical field of lithium iron manganese phosphate batteries, the lithium iron manganese phosphate positive electrode material comprises a lithium iron manganese phosphate positive electrode active material and a solid electrolyte interface film located on the surface of the lithium iron manganese phosphate positive electrode active material, the solid electrolyte interface film contains C, N, F and O elements, and the ratio of the relative content of the C element to the relative content of the N element in the solid electrolyte interface film is (0.5-2): 1. According to the solid electrolyte interface film, the dissolution of manganese ions and the decomposition side reaction of the electrolyte at high voltage / high temperature are remarkably inhibited, the generation of gas is fundamentally reduced, the battery is free from flatulence phenomenon after being circulated at high temperature, and the safety and the reliability of the battery are greatly improved.

The invention relates to the field of positive electrode materials, in particular to a lithium manganese iron phosphate / carbon fiber composite positive electrode material and a preparation method thereof, which are used for solving the problems of poor electronic conductivity of lithium manganese iron phosphate and the like. The preparation method comprises the following steps: firstly, carrying out graft modification and ZrO2 film coating on carbon fibers, and then compounding the modified carbon fibers with lithium iron manganese phosphate to obtain the lithium iron manganese phosphate / carbon fiber composite positive electrode material. The lithium manganese iron phosphate / carbon fiber composite positive electrode material can greatly improve the electronic conductivity and improve the rate capability; active substance dissolution and side reaction can be inhibited, and the cycling stability is improved; a lithium ion diffusion channel can be optimized, and the ion conduction efficiency is improved; the electrode mechanical performance can be enhanced, and the structural reliability is improved. Meanwhile, the advantages of all the components are exerted, and finally the electrochemical performance and structural stability of the composite positive electrode are remarkably improved.

The invention discloses a preparation method of a sodium ferromanganese vanadium phosphate material of a sodium battery positive electrode. The preparation method comprises the following steps: S1, preparing a hydrophosphate solution and a manganous salt solution; and S2, adding the hydrophosphate solution into the manganous salt solution, and reacting to obtain the manganous hydrogen phosphate crystal nucleus slurry. And S3, filtering and washing the manganese hydrogen phosphate crystal nucleus slurry, adding water into the manganese hydrogen phosphate material to prepare slurry, heating to 85-95 DEG C, respectively adding a ferrous source and a phosphorus salt solution, and reacting to obtain the manganese iron hydrogen phosphate slurry. And S4, filtering, washing and drying the iron manganese hydrogen phosphate slurry, adding water into the dried slurry to prepare slurry, adding phosphoric acid, heating to 90-100 DEG C, reacting to obtain an iron manganese phosphate compound precipitate, and filtering, washing and drying the precipitate to obtain an iron manganese phosphate material. The sodium manganese iron vanadium phosphate product is prepared by adopting a coprecipitation method and high-temperature sintering, and the method has the advantages of short process flow, simple process, only one-time sintering, low energy consumption and the like.

The invention discloses a lithium iron manganese phosphate positive electrode material and a preparation method thereof, and belongs to the technical field of lithium ion batteries, the lithium iron manganese phosphate positive electrode material at least comprises lithium iron manganese phosphate particles and a coating layer coating the lithium iron manganese phosphate particles; the raw material of the coating layer comprises an aluminum fluoride embedded poly (ethylenedioxythiophene)-lithium polystyrene sulfonate compound. And the coating layer can be used as a physical barrier to form dynamic interface protection, so that dissolution of manganese and erosion of electrolyte are directly inhibited, and side reaction between the electrolyte and the positive electrode material is reduced. Meanwhile, a more flexible transmission channel is provided for lithium ions and electrons, the conductivity of the positive electrode material is enhanced while the transmission efficiency of the lithium ions is improved, and the lithium manganese iron phosphate positive electrode material with stable structure, high rate capability and cycling stability is obtained.

The invention provides a lithium manganese iron phosphate precursor and a preparation method thereof, lithium manganese iron phosphate, a lithium ion battery and electric equipment, and relates to the technical field of new energy. Primary particles of the lithium manganese iron phosphate precursor provided by the invention are thick-sheet-shaped, the side surfaces of the primary particles are porous, the large-size primary particles and the porous lithium manganese iron phosphate precursor have many defects, are easy to grind and have excellent processability, Li < + > is easier to react with manganese iron phosphate in the sintering process to generate lithium manganese iron phosphate with high sphericity degree, the compaction density is high, and the lithium manganese iron phosphate precursor has good performance. No other impure phase is generated, and the capacity and the rate capability are good. According to the preparation method of the lithium manganese iron phosphate precursor provided by the invention, the ammonium manganese iron phosphate hydrate with large-size primary particles can be generated by adding excessive phosphorus sources into the mixed metal salt solution. Furthermore, pyrophosphorylation is generated through high-temperature calcination, a large number of air holes are generated, and finally the porous lithium iron manganese phosphate precursor is generated.

The invention belongs to the technical field of batteries, and discloses a carbon-coated modified lithium manganese iron phosphate positive electrode material and a preparation method and application thereof, and the carbon-coated modified lithium manganese iron phosphate positive electrode material comprises carbon-coated modified lithium manganese iron phosphate positive electrode material particles, the carbon-coated modified lithium manganese iron phosphate positive electrode material particle comprises a lithium manganese iron phosphate core, a first carbon coating layer and a second carbon coating layer, wherein the first carbon coating layer is positioned between the lithium manganese iron phosphate and the second carbon coating layer; the graphitization degree of the first carbon coating layer is greater than that of the second carbon coating layer. The carbon-coated modified lithium manganese iron phosphate positive electrode material has relatively high conductivity, compaction density and the like, and a battery using the carbon-coated modified lithium manganese iron phosphate positive electrode material has relatively high charge-discharge rate, excellent energy density, excellent capacity and the like.

The invention discloses carbon-coated lithium manganese iron phosphate, a preparation method thereof, a positive pole piece containing the carbon-coated lithium manganese iron phosphate, a battery and an electric device, and the preparation method of the carbon-coated lithium manganese iron phosphate comprises the following steps: carrying out dry mixing on a lithium source, a manganese source, an iron source and a phosphorus source to obtain first mixed powder; carrying out presintering treatment and crushing treatment on the obtained first mixed powder under the protection of protective gas to obtain a lithium manganese iron phosphate precursor; carrying out dry mixing on the obtained lithium manganese iron phosphate precursor and a solid organic carbon source to obtain second mixed powder; and carrying out step-by-step sintering treatment and crushing treatment on the obtained second mixed powder under the protection of protective gas to obtain the carbon-coated lithium manganese iron phosphate. The preparation method of the carbon-coated lithium manganese iron phosphate provided by the invention is simple in process, low in production cost and suitable for large-scale production, and the prepared carbon-coated lithium manganese iron phosphate also has relatively high powder compaction density and relatively high gram volume.

The invention provides a secondary battery and an electronic device, the secondary battery comprises a positive pole piece and a negative pole piece, the positive pole piece comprises a positive pole material layer, the positive pole material layer comprises a positive pole active material, and the positive pole active material comprises a manganese-containing material; the manganese-containing material comprises at least one of lithium manganate, lithium iron manganese phosphate, a lithium-rich manganese-based material or nickel cobalt lithium manganate. The negative pole piece comprises a first additive, the first additive comprises at least one of carboxylate, sulfonate or a metal organic framework compound, carboxylate comprises at least one of lithium oxalate, sodium citrate, sodium maleate or sodium tartrate, sulfonate comprises at least one of sodium benzenesulfonate, sodium dodecyl benzene sulfonate or sodium methanesulfonate, and metal organic framework compound comprises at least one of lithium oxalate, sodium citrate, sodium maleate or sodium tartrate. The metal organic framework compound is prepared from at least one of Zn (C4H7N2) 2, C48H28O32Zr6 or C14H16N2O8Mg2. The invention further discloses a preparation method of the metal organic framework compound. The secondary battery meets the characteristics, and the cycle performance of the secondary battery can be improved.

The invention relates to the technical field of lithium ion battery materials, in particular to a preparation method of a manganese iron carbonate precursor and a lithium manganese iron phosphate positive electrode material, which comprises the following steps: preparing a mixed salt solution from a bivalent manganese salt and a bivalent iron salt; adding pure water and the mixed salt solution into a first-stage reaction kettle, preparing a reaction base solution, and adding a first precipitator into the first-stage reaction kettle to obtain a first reaction product; enabling the first reaction product to flow into a second reaction kettle through overflow, and adding a second precipitator to obtain a second reaction product; and enabling the second reaction product to flow into a slurry transfer tank through overflow, washing and drying the second reaction product to obtain a manganese iron carbonate precursor, mixing a lithium source, a phosphorus source, a carbon source and the manganese iron carbonate precursor, and sintering to prepare the carbon-coated lithium iron manganese phosphate positive electrode material. The primary particle size of the prepared manganese iron carbonate precursor can be less than or equal to 200nm, and the rate capability and the cycling stability of a positive electrode material lithium ion battery finally prepared by sintering are improved.

The invention discloses a lithium manganese iron phosphate material prepared by taking lithium iron phosphate as a template agent as well as a preparation method and application of the lithium manganese iron phosphate material. Specifically, lithium iron phosphate is taken as a template agent, other iron sources, manganese sources, lithium sources, phosphorus sources and carbon sources are added, high-energy ball milling mixing is carried out in water or an organic solvent, rheological phase reaction is carried out, and the surface of the lithium iron phosphate is uniformly coated with the raw materials. And then drying, pre-calcining, secondary carbon coating and high-temperature calcining are carried out, and bulk phase diffusion and epitaxial growth of the raw materials are synchronously carried out on the surface of the lithium iron phosphate by utilizing a solid phase diffusion-epitaxial growth coupling mechanism, so that the lithium iron manganese phosphate material is finally obtained. The lithium iron manganese phosphate prepared by taking lithium iron phosphate as a template agent and matching with other iron sources has the characteristic of manganese element concentration gradient distribution, and meanwhile, nanoscale particle refinement is realized. The secondary battery prepared by taking the lithium manganese iron phosphate as the positive electrode material has excellent electrochemical performance and cycling stability.

The application provides a lithium ion battery and an electric device, the lithium ion battery comprising a positive electrode sheet and an electrolyte, an active substance in the positive electrode sheet comprising a phosphate lithium positive electrode material and a lithium nickel cobalt manganese oxide, the electrolyte comprising a positive electrode film former, a negative electrode film former and a lithium salt, the lithium salt comprising lithium hexafluorophosphate and a lithium bisfluorosulfonylimide salt, the lithium ion battery satisfying the following formula: wherein NL is a mass ratio of the lithium nickel cobalt manganese oxide and the phosphate lithium positive electrode material, S alt is a value of a molar concentration of the lithium hexafluorophosphate and the lithium bisfluorosulfonylimide salt in the electrolyte in mol / L, and A dd is a mass ratio of the positive electrode film former and the negative electrode film former. The application can adjust the ratio of the positive electrode film former and the negative electrode film former and the ratio of the high-heat-resistance lithium salt according to the mixing ratio of the ternary material doped in the lithium manganese iron phosphate or the lithium iron phosphate, so that the cycle performance of the battery is improved.

The invention discloses a lithium iron phosphate and lithium manganese phosphate mixed positive electrode material, a battery and a preparation method. And mixing lithium iron phosphate, lithium iron manganese phosphate and the polymer, and then performing low-temperature pyrolysis to obtain the mixed lithium iron phosphate and lithium iron manganese phosphate positive electrode material. At present, although LFP and LMFP are applied to lithium ion batteries, the application of the LFP and the LMFP is limited due to objective defects of the LFP and the LMFP, the contradiction between energy density and processability cannot be solved in the prior art, and the technical scheme in the prior art has the problems that the technical process is complicated, and the LFP and the LMFP are not beneficial to industrial production and application. By adopting a simple technical scheme, the invention creatively provides the positive electrode material mixing lithium iron phosphate and lithium manganese iron phosphate, unexpectedly, good cycling stability, safety and processing performance are obtained, the energy density of the battery can be improved, and the popularization of the positive electrode in the field of high-energy density application is realized.

Disclosed is a preparation method for ammonium manganese iron phosphate. The preparation method comprises: respectively mixing a mixed salt solution of metals and an ammonium dihydrogen phosphate solution with an organic solution to obtain a mixed liquor of metal salts and a mixed liquor of phosphate; concurrently adding the mixed liquor of metal salts, the mixed liquor of phosphate and a first ammonia water into a base solution for reaction; and carrying out solid-liquid separation to obtain ammonium manganese iron phosphate. A mixed metal salt solution of a ferrous source and a manganese source and a phosphorus source are subjected to a coprecipitation reaction in an organic phase, to synthesize large-particle ammonium manganese iron phosphate with high compaction density. After the ammonium manganese iron phosphate is mixed with a lithium source and a carbon source, sintering can be carried out to prepare a lithium manganese iron phosphate cathode material.

The invention discloses carbon-coated lithium iron manganese phosphate, a preparation method thereof, a positive pole piece containing the carbon-coated lithium iron manganese phosphate, a battery containing the carbon-coated lithium iron manganese phosphate, and an electric device containing the carbon-coated lithium iron manganese phosphate. Lithium iron manganese phosphate slurry with the volume distribution particle size Dv50 of 100-150 nm and lithium iron manganese phosphate slurry with the volume distribution particle size Dv50 of 400-800 nm are mixed, and then spray granulation treatment, sintering treatment and crushing treatment are performed to obtain the carbon-coated lithium iron manganese phosphate. And the carbon-coated lithium manganese iron phosphate is obtained. The carbon-coated lithium manganese iron phosphate prepared by the preparation method provided by the invention can have high gram volume, high powder compaction density, low specific surface area and high cycle stability, and when the carbon-coated lithium manganese iron phosphate is applied to a positive pole piece and a battery, the battery can have high energy density and good cycle performance.

The invention provides an electrolyte for a lithium iron manganese phosphate battery and application of the electrolyte. The electrolyte for the lithium iron manganese phosphate battery comprises electrolyte lithium salt, a polyfunctional group compound additive, a film-forming additive and an organic solvent. The polyfunctional group compound additive with a specific structure is added into the electrolyte, so that the high-voltage performance and the high-temperature storage performance of the battery can be improved, the dissolution of manganese in the positive electrode material can be inhibited, and the cycle performance of the positive electrode material is improved.

A positive electrode piece, comprising a current collector and a positive electrode active layer, the positive electrode active layer being arranged on at least one surface of the current collector; the positive electrode active layer comprises a first active layer directly coated on the current collector and a second active layer coated on the surface of the side of the first active layer away from the current collector; the first active layer comprises first lithium iron phosphate salt particles and / or first manganese iron phosphate salt particles, the second active layer comprises second lithium iron phosphate salt particles, the primary average particle diameter of the first lithium iron phosphate salt particles and / or the first manganese iron phosphate salt particles is 150 nm to 480 nm, and the primary average particle diameter of the second lithium iron phosphate particles is 500-3000 nm.