3580results about "Phosphorus compounds" patented technology

The invention discloses an intelligent gradient extraction process and method for nutritional ingredients in yak bone marrow, and belongs to the technical field of bioactive substance extraction. The extraction method comprises the following four steps: gradient pressure supercritical degreasing, double-enzyme synergistic gradient enzymolysis, acid concentration gradient demineralization and temperature gradient gelatin extraction, and through the process coupling design of gradient pressure degreasing, buffer enzymolysis, graded acidolysis and membrane separation of gelatin, the high yield of the product in the previous stage is ensured; active structures of follow-up components are reserved to the greatest extent. Meanwhile, a sensing-decision-execution closed-loop system is constructed, real-time data sources such as NIR moisture sensing, online OPA detection and XRD in-situ analysis are integrated, technological parameters are dynamically adjusted through a multi-objective optimization algorithm, and global optimization of the yield, the purity and the energy consumption is achieved.

The invention relates to a preparation method of a nickel ion doped modified ferric sodium pyrophosphate positive electrode material, and belongs to the technical field of sodium ion battery positive electrode materials. The nickel ion doped modified ferric sodium pyrophosphate positive electrode material is prepared by adopting an integrated process system of liquid phase uniform mixing, spray granulation and precise segmented calcination. According to the process system, atomic-scale uniform doping of nickel ions and a specific microstructure of a precursor are realized through spray drying, and a plurality of inherent key technical problems of low electronic conductivity, low ion diffusion rate, impurity phase generation and the like of an NFPP material are solved together through a synergistic effect with a subsequent calcining process; furthermore, the discharge capacity of the ferric sodium phosphate pyrophosphate composite material at high rate is improved, so that the battery has relatively high cycling stability.

The invention provides a lithium iron phosphate-based positive electrode material and a preparation method thereof, a positive plate and a battery, the lithium iron phosphate-based positive electrode material comprises a lithium iron phosphate matrix and a carbon material existing on the surface of the lithium iron phosphate matrix, and the lithium iron phosphate-based positive electrode material comprises mesopores and macropores. The conductivity and the ion transmission performance of the lithium iron phosphate-based positive electrode material can be both improved, and the energy density and the rate capability of the battery are improved.

A lithium manganese iron phosphate cathode material, including a first lithium manganese iron phosphate particle and a second lithium manganese iron phosphate particle. A molar ratio of Mn to Fe in the first lithium manganese iron phosphate particle is greater than or equal to 1. A molar ratio of Mn to Fe in the second lithium manganese iron phosphate particle is smaller than or equal to the molar ratio of Mn to Fe in the first lithium manganese iron phosphate particle. A particle size of the first lithium manganese iron phosphate particle is smaller than or equal to a particle size of the second lithium manganese iron phosphate particle. A preparation method of the lithium manganese iron phosphate cathode material and an application thereof are provided. The first precursor, having a manganese content greater than or equal to that of iron, inhibits crystal growth during sintering, resulting in a smaller particle size. The second precursor, having a manganese to iron ratio smaller than or equal to the ratio in the first precursor, promotes crystal growth during sintering, resulting in a larger particle size. This results in a particle size grading between large particles and small particles, improves the spatial utilization of particle packing, and enhances the compaction density and volumetric capacity of the lithium manganese iron phosphate cathode material.

The invention discloses a reaction kettle device for synthesis of an iron phosphate material, and particularly relates to the technical field of synthesis of battery materials, and the device comprises a kettle body, a driving motor, a transmission disc and a turbo-type paddle. A sealing cover is arranged at the top of the kettle body, a driving motor is connected with a rotating shaft, an anchor blade is arranged below the rotating shaft, and the bottom realizes turbine blade lifting and sleeve guide limiting through transmission of a piston cavity and compressed gas; and a ratchet wheel on the outer wall of the rotating shaft is meshed with a pawl in the transmission disc in a one-way mode, and intermittent wall scraping is achieved. According to the device, dead angles are broken through synergistic stirring of the double blades, the mixing uniformity and the reaction rate are improved, materials adhering to the wall are efficiently removed through intermittent wall scraping, the stable reaction environment is guaranteed through multiple sealing, the structure is flexible to adjust, maintenance is convenient and fast, efficient and high-quality synthesis of the iron phosphate material can be achieved, and the device is suitable for industrial large-scale production.

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 provides equipment and a process for leaching battery-grade lithium phosphate by using waste lithium iron phosphate, and relates to the technical field of resource recovery and battery material preparation, the equipment comprises a support frame, a heating seat, a leaching tank, a driving mechanism and a discharging mechanism; the heating base is installed in the middle of the interior of the supporting frame, the leaching tank is installed on the inner wall of the heating base, an installation cover is installed on the top of the leaching tank in a sealed mode, a main material pipe and an auxiliary material pipe are installed on the two sides of the leaching tank respectively, and a discharging pipe is installed at the bottom end of the leaching tank; the driving mechanism comprises a mounting seat and a motor, the mounting seat is fixedly arranged at the inner bottom of the mounting cover, and the motor is mounted at the top of the mounting seat. According to the scheme, caked industrial-grade sodium phosphate or sodium hydroxide can be crushed into fine particles by adopting rotary grinding, and a reagent can be uniformly dispersed into a purification solution by matching with rotary dispersion blanking, so that the pH of a system and the concentration of sodium phosphate are integrally stable, local reaction abnormity is avoided, and more stable preparation of battery-grade lithium phosphate is ensured.

The invention provides a preparation method of grain size grading iron phosphate and high compaction type lithium iron phosphate. Removing impurities from the titanium dioxide byproduct ferrous sulfate, and filtering to obtain a purified ferrous sulfate base solution; the method comprises the following steps: reacting phosphoric acid with ammonia water to prepare ammonium phosphate solutions with different reaction pH values and phosphorus molar concentrations, respectively mixing the ammonium phosphate solutions with a certain amount of hydrogen peroxide, and sequentially adding an iron source, a first phosphorus salt solution, a second phosphorus salt solution and a third phosphorus salt solution into a tubular reactor for reaction to obtain iron phosphate slurry; and sequentially converting, filtering, washing, drying and calcining the completely reacted slurry to finally prepare the anhydrous iron phosphate. According to the invention, a mode of controlling solution nucleation and growth is adopted, nucleation and growth rates are controlled by preparing phosphorus salt solutions with different concentrations, size grading of precursor particles is directly realized in a synthesis reaction section, and slurry grading uniformity is further realized through aging crystal transformation. Lithium iron phosphate prepared from the iron phosphate precursor has high compaction density.

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises a carbon-coated lithium iron phosphate material. By regulating and controlling the relative proportion of the specific surface areas of carbon structures with different micromorphologies in the surface layer of the carbon-coated lithium iron phosphate material, specifically, the carbon-coated lithium iron phosphate material disclosed by the invention has a carbon coating factor eta, and when eta is more than or equal to 0.81 and less than or equal to 0.95, the lithium iron phosphate material has high-quality carbon coating; the lithium iron phosphate material capacity exertion is facilitated, the pole piece dehydration efficiency is remarkably improved, and the prepared battery monomer has excellent energy density, cycle performance and processing performance.

The invention relates to the technical field of batteries, in particular to a lithium iron phosphate material and a preparation method thereof, a positive pole piece, a battery, an energy storage device and electric equipment. The lithium iron phosphate material comprises first particles and second particles, the particle size of the second particles is larger than that of the first particles, the second particles comprise secondary particles, the secondary particles are composed of a plurality of primary particles, and at least part of the first particles are exposed on the surfaces of the secondary particles. On the surfaces of the second particles, the plane area of the second particles is S1, the accumulated plane area of all the primary particles with the size smaller than 1 micron in the primary particles exposed on the surfaces of the secondary particles is S2, and the following relational expression is met: 35% > = S2 / S1 > = 5%. The lithium iron phosphate material not only can improve the capacity performance of the battery, but also has relatively good electrical performance.

The embodiment of the invention provides a polyanionic positive electrode material and a preparation method thereof, a positive electrode plate, a secondary battery and an electric device, and belongs to the technical field of secondary batteries. The polyanionic positive electrode material is ferric sodium pyrophosphate, the polyanionic positive electrode material comprises primary particles and secondary spheres formed by the primary particles, and the primary particles comprise primary particles with the particle size Dv50 being d1 and primary particles with the particle size Dv50 being d2, d1gt; d2, the secondary sphere is of a core-shell structure, a core is of a porous structure, and a shell layer is of a compact structure. The polyanionic positive electrode material is relatively high in compaction density, and has the advantages of good cycle performance and good rate capability.

The invention relates to the technical field of production of dipotassium phosphate, discloses a process method for continuously producing food-grade anhydrous dipotassium phosphate, aims to obtain a food-grade anhydrous dipotassium phosphate product through a drying reaction in a rotary polymerization furnace by a one-step method, and effectively solves the problems of multiple control procedures, complicated process control and high production cost. The coke content is greatly reduced under the condition of ensuring the dipotassium phosphate content.

This invention provides a high-density lithium iron phosphate cathode material with a nanoporous structure and its preparation method, comprising the following steps: (1) preparing cathode material intermediate dispersion A; (2) preparing cathode material intermediate dispersion B; (3) mixing the cathode material intermediate dispersion A and the cathode material intermediate dispersion B, and spray drying to obtain lithium iron phosphate intermediate mixed particles; (4) sintering the lithium iron phosphate intermediate mixed particles in an inert gas to obtain the lithium iron phosphate cathode material. This invention can improve the electrolyte wettability of the material, shorten the lithium ion transport distance, and enable more lithium ions inside the particles to participate in insertion and extraction more quickly and effectively, thereby improving its electrochemical performance.

The application specifically discloses a phosphate-based positive electrode material and a preparation method and application thereof. The phosphate-based positive electrode material comprises base particles and a carbon coating layer coated on the surface of the base particles; the chemical formula of the base particles is Li x M y PO4, 0.96≤x≤1.08, 0.96≤y≤1, M comprises at least one of Fe and Mn; wherein, the M site is doped with a first metal element, the first metal element comprises at least one of Ti, V, Cr, Co, Ni, Nb, Mo and W; and / or, the Li site is doped with a second metal element, the second metal element comprises at least one of Mg and Zr; the carbon coating layer comprises a carbon material, and the degree of disorder I D / I G of the carbon material is ≤1.2. The application has the advantages of improving the electrochemical performance of the phosphate-based positive electrode material and reducing the ion elution rate thereof.

The invention belongs to the technical field of material recovery, and particularly discloses a regeneration method of a waste lithium iron phosphate battery positive electrode material, a lithium ion battery positive plate prepared from regenerated lithium iron phosphate powder and a lithium ion battery. Waste lithium iron phosphate powder is uniformly mixed with uric acid and a lithium source, and the mixture is subjected to annealing and annealing treatment in an inert atmosphere, so that structure repair and performance upgrading of a failure material are realized. Uric acid serves as a reducing agent and a carbon-nitrogen source at the same time in the process, Fe < 3 + > is effectively reduced through thermal decomposition of the uric acid, anti-position defects are reduced, a uniform nitrogen-doped carbon coating layer is synchronously formed on the surfaces of particles, and the conductivity and the ion diffusion rate of the material are remarkably improved. The method is short in process flow and environment-friendly, and does not need to use strong acid and strong alkali. The regenerated lithium iron phosphate material has excellent electrochemical performance, the capacity retention rate reaches 91.22% after 500 times of circulation under the multiplying power of 0.5 C, the capacity retention rate is far superior to that of a commercial material, and an effective way is provided for high-valued recovery of waste lithium iron phosphate.

The invention belongs to the technical field of lithium ion battery material recovery, and discloses a regeneration, repair and doping method of a waste lithium iron phosphate material and a regenerated positive electrode material. The method comprises the following steps: firstly, immersing waste LiFePO4 powder into a mixed solution of citric acid and ascorbic acid, oscillating to selectively dissolve out Fe < 3 + > impurities, and synchronously reducing Fe < 3 + > on the surface to Fe < 2 + >; then Li2CO3 is added into the leached powder for lithium bit compensation, and ball milling and uniform mixing are carried out; then Al2O3 and TiCl3 are added for aluminum-titanium co-doping, and ultrasonic dispersion is carried out uniformly; and finally, carrying out segmented sintering. In the first stage, sintering is carried out in an air atmosphere at 300-350 DEG C; in the second stage, sintering is performed at 600-700 DEG C in an inert gas atmosphere; and finally obtaining the regenerated positive electrode material. According to the method, waste lithium iron phosphate batteries can be turned into wealth, the lithium iron phosphate positive electrode material with good electrochemical performance is obtained, the complex and expensive impurity removal process is omitted, the cost is low, and possibility is provided for large-scale industrial regeneration and repair of waste lithium iron phosphate active substances.

The invention relates to a method for preparing lithium dihydrogen phosphate from a lithium-containing solution by using an extraction-reverse extraction technology, an extraction agent adopted in the method comprises a main extraction agent, a synergistic extraction agent and a diluent, the pKa value of the main extraction agent is 2.2-7, the synergistic extraction agent has a P = O group or a cavity diameter of 0.12-0.15 nm, the water solubility of the synergistic extraction agent is less than or equal to 50 mg / L, and the diluent is a diluent. The synergistic extraction factor R of the extraction agent is more than 100, R = Dmix / (D1 + D2), Dmix is the extraction distribution ratio of the main extraction agent to the lithium when the main extraction agent and the synergistic extraction agent are mixed according to the mass ratio of 1: 1-1: 2, D1 is the extraction distribution ratio of the main extraction agent to the lithium, D2 is the extraction distribution ratio of the synergistic extraction agent to the lithium, and the stripping agent is phosphoric acid. According to the method disclosed by the invention, by selecting the main extraction agent and the synergistic extraction agent, on one hand, lithium monohydrogen phosphate and lithium phosphate impurities cannot be generated by reaction when phosphoric acid is adopted for reverse extraction, and on the other hand, higher separation degree on sodium and potassium can be achieved during extraction, so that high-purity lithium dihydrogen phosphate can be efficiently prepared.

The invention relates to the technical field of lithium ion batteries, in particular to a chromium-molybdenum double-doped lithium iron phosphate material as well as a preparation method and application thereof. The preparation method is used for solving the problems of low capacity, low electronic conductivity and poor cycling stability of the existing lithium iron phosphate material. According to the preparation method, chromium-molybdenum is doped into lithium iron phosphate, and the bond energy of a Cr-O bond and a Mo-O bond is stronger than that of a Fe-O bond, so that the dissolution loss of Fe < 2 + > in long-term circulation is reduced, and the battery capacity and the intrinsic electron conductivity of the material are improved; lithium iron phosphate is coated with nitrogen-doped carbon nanotubes, and nitrogen is doped in graphite crystal lattices of the carbon nanotubes, so that additional free electrons are provided, the intrinsic conductivity is improved, the resistance is reduced, the rate capability is improved, and the cycle life is prolonged; the polyaniline coating layer forms a barrier layer on the surface of the lithium iron phosphate particles, so that the cycle performance and the battery capacity are improved; the three components cooperate to improve the capacity, conductivity, rate capability and cycling stability of the material.

The invention discloses a grading reaction crystallization recovery process and system for semiconductor fluorine-containing and phosphorus-containing waste liquid, the fluorine-containing and phosphorus-containing waste liquid and a lime solution react in a fluorine recovery crystallization reactor under the condition that the pH is 3-4 to form calcium fluoride crystals, and the calcium fluoride crystals are dehydrated to obtain calcium fluoride particle crystal products; the effluent of the fluorine recovery crystallization reactor, the calcium fluoride crystal dehydration filtrate, the lime solution and the calcium chloride solution react in a secondary reaction tank under the condition that the pH is 5-6, and calcium fluoride, fluorapatite, silicon dioxide and silicon-aluminum precipitates are removed through coagulation, flocculation and precipitation; effluent of the second-stage reaction tank, the lime solution and the calcium chloride solution react in the phosphorus recovery crystallization reactor under the condition that the pH is 7-8 to generate hydroxyapatite crystals, and the hydroxyapatite crystals are dehydrated to obtain hydroxyl calcium phosphate particle crystal products. Meanwhile, a high-purity calcium fluoride crystal product and a hydroxyl calcium phosphate crystal product are produced, and fluorine and phosphorus are recycled.

The invention discloses a preparation method of a metal doped type hydroxyapatite nanoflower. The method specifically comprises the following steps: dispersing a calcium source and soluble metal salt into water, adding acid phosphate, urea and L-histidine, uniformly mixing, carrying out a hydrothermal reaction, mechanically stirring, filtering, washing, and drying a hydrothermal system precipitate to obtain the corresponding metal-doped hydroxyapatite nanoflower. Compared with the prior art, the metal-doped hydroxyapatite nanoflower prepared by the preparation method disclosed by the invention is directly assembled by nanosheets, and a single metal type can be doped in a customized manner. According to the method, water is used as a unique solvent, the use of an organic solvent is avoided, the pH does not need to be adjusted in advance, the technological process is simple, operation is convenient, equipment investment is small, and the method is suitable for industrial production.

Disclosed in the present invention are a precursor for a polyanionic sodium-ion battery positive electrode material and a preparation method therefor. The chemical general formula of the precursor is NaxMyHzOa(POb)c·mH2O, wherein M is a transition metal element Fe and / or Mn. The relationship between x, y, z, a, b, and c is x+3y+z-2a+5c-2b×c=0, and m is greater than or equal to 0. The precursor for the polyanionic sodium-ion battery positive electrode material and the preparation method therefor of the present invention have the characteristics of high phase purity, high compaction density, excellent electrochemical performance, low costs, and wide system applicability.

The invention belongs to the technical field of preparation processes of barium metaphosphate, and particularly relates to a preparation method of monodisperse micron-sized barium metaphosphate. The preparation method comprises the following steps: mixing purified barium carbonate slurry and phosphoric acid according to a certain molar ratio, reacting to obtain barium dihydrogen phosphate slurry, adding ethanol and a particle size regulating agent, uniformly mixing, and carrying out spray drying to obtain a crude product; the particle size regulating agent comprises ammonium citrate, polyalcohol and barium metaphosphate; and calcining the crude product to obtain the product monodisperse micron-sized barium metaphosphate. According to the preparation method, a small amount of particle size regulating agent and a certain amount of ethanol are added, a crude product with uniform particle size distribution is prepared under a spray drying process condition, and then calcination is performed to obtain the micron-sized barium metaphosphate with uniform particle size distribution.

The invention discloses a manganese iron oxalate precursor, a lithium manganese iron phosphate material and a preparation method and application of the manganese iron oxalate precursor and the lithium manganese iron phosphate material, and belongs to the technical field of battery materials. The lithium manganese iron phosphate material core layer is prepared by taking the oxalate manganese iron precursor with a specific particle size range, particle size distribution uniformity and a specific structure as a raw material, and meanwhile, the shell layer comprising the ionic conductive agent and carbon is introduced outside the core layer, so that the comprehensive performance of the lithium manganese iron phosphate material can be effectively improved; and thus, the capacity, the cycle performance and the first charge-discharge efficiency of the prepared corresponding secondary battery are improved.

The invention relates to a method for selectively leaching and regenerating a positive electrode material from a waste lithium ion battery, and belongs to the technical field of lithium ion batteries. The method comprises the following steps: discharging, disassembling, crushing, calcining and screening the waste lithium ion battery, adding an obtained positive active material into an oxalic acid solution, and stirring and reacting at 60-80 DEG C under the irradiation of an ultraviolet lamp to obtain a leaching solution rich in metal elements and leaching residue iron phosphate; adding sodium carbonate into the leachate for reaction to obtain lithium carbonate; and ball-milling and mixing iron phosphate, lithium carbonate and a carbon source, drying and calcining to obtain the regenerated lithium iron phosphate positive electrode material. The oxalic acid system is catalyzed by ultraviolet light to generate hydroxyl free radicals with strong oxidizing property, so that the leaching efficiency of lithium is remarkably improved, and the dissolution of iron is inhibited, thereby realizing the efficient separation of lithium and iron. The leaching residue is high-purity iron phosphate, lithium in the leaching solution is recycled in the form of lithium carbonate, and the leaching residue and the lithium carbonate can be directly used for regenerating the lithium iron phosphate positive electrode material as precursors, so that the technological process is greatly simplified, and the production cost is reduced.

The invention provides a method for strengthening recovery of a waste lithium iron phosphate material by using waste lithium cobalt oxide as an oxidizing agent. The method comprises the following steps: discharging and disassembling waste lithium iron phosphate and lithium cobalt oxide batteries to obtain positive plates; dissolving aluminum foil in the positive plate in a sodium hydroxide alkaline leaching solution to obtain lithium iron phosphate and lithium cobalt oxide positive electrode powder; the method comprises the following steps: leaching lithium iron phosphate positive electrode powder by adopting a deep-eutectic solvent, and meanwhile, realizing an enhanced leaching process by taking lithium cobalt oxide positive electrode powder as an oxidizing agent; and carrying out coordination separation and photo-reduction separation on the completely leached solution to realize selective recovery of cobalt, iron, phosphorus and lithium. According to the method, the oxidation-reduction capacity of the material is fully utilized to strengthen the leaching process, efficient recovery of valuable elements in the waste positive electrode material is achieved, and additional addition of an oxidizing agent and a reducing agent is avoided. The method can achieve the purposes of synergistic enhanced leaching and selective separation of the waste lithium cobalt oxide material and the waste lithium iron phosphate material, and is low in cost, high in recovery rate and wide in industrial application prospect.

Disclosed is a phosphate e precursor, which has a chemical formula of LixMy(PO4)(x+y) / 2Az·wH2O, where M is a transition metal element selected from one or more of Fe, Ti, V, Cr, Ni, Co, Mn, Al, Nb, Y, Zr, Sb, Mo, Sn, and Ce, A is one or more of F, OH, CO32−, C2O42−, and O2−; and 0.5≥x<1.2, 0.5<y≥1, 0≥z≥1, and 0.1≥w<8. The phosphate precursor has good uniformity, contains crystal water, and exhibits excellent structural stability, and can be used to prepare olivine-type phosphate cathode material through sintering at a low temperature of 260° C.-600° C.; and the phosphate precursor is blended with a carbon source and is subjected to heat treatment to obtain carbon-contained cathode material, which has good electrochemical properties.

The invention discloses a regeneration method of a positive electrode active material, a regenerated positive electrode active material and a battery, and belongs to the technical field of regeneration of positive electrode active materials. The method comprises the following steps: mixing a positive electrode active material and a lithium salt, heating and preserving heat to obtain eutectic molten salt in a molten state, and inducing the eutectic molten salt to generate a cavitation effect. The molten lithium salt in the eutectic molten salt can supplement lithium ions lost by the positive electrode active material and repair and regenerate the positive electrode active material, the eutectic molten salt in the molten state is a carrier of the cavitation effect, the cavitation effect can further promote repair and regeneration of the positive electrode active material in the eutectic molten salt, and the two are combined to generate a synergistic effect; the regeneration of the retired lithium ion positive electrode active material is improved in situ in one step, so that the regenerated positive electrode active material with relatively high capacity retention ratio can be obtained, and the remanufacturing requirement of a vehicle-specification-grade power battery is met.

The invention discloses high-compaction-density modified spherical lithium iron phosphate and a preparation method and application thereof.The preparation method comprises the steps that a composite iron source precursor and modified phenolic resin are compounded to form a spherical inner core, and then the spherical inner core is coated with a lithium-phosphorus mixed layer to construct a core-shell structure; the modified spherical lithium iron phosphate with the characteristics of'spherical core-porous shell 'is prepared by introducing boron nitride nanosheets as a structure-directing agent and a doping source and combining a dynamic gradient sintering process, and the modified phenolic resin is obtained by grafting water-soluble phenolic resin and polyethylene glycol, and the solid content of the modified phenolic resin is greater than or equal to 50%. The modified lithium iron phosphate with the compaction density larger than or equal to 2.55 g / cm < 3 > and the capacity retention ratio larger than 92.0% after 1C circulation 2000 times is prepared, and the technical bottlenecks that doping is not uniform, morphology is out of control and the compaction density is low in a traditional process are solved.

The invention provides a lithium manganese iron phosphate material, a preparation method thereof, a positive pole piece and a lithium ion battery. The preparation method of the lithium manganese iron phosphate material comprises the following steps: sequentially mixing and sintering a manganese iron phosphate precursor, a manganese iron pyrophosphate precursor, a lithium source, a carbon source and an organic additive to obtain the lithium manganese iron phosphate material, the ferromanganese phosphate precursor is in an amorphous state; the crystal structure of the ferromanganese pyrophosphate precursor is a monoclinic system; the organic additive is a polymer of which the molecular structure carries an anionic functional group; sintering comprises first-stage sintering, second-stage sintering, third-stage sintering, fourth-stage sintering and fifth-stage sintering which are performed in sequence. According to the invention, the unique properties of the amorphous ferromanganese phosphate precursor and the monoclinic system ferromanganese pyrophosphate precursor are utilized, and the special organic additive and the five-stage sintering process are combined, so that the particle filling effect in the sintering process is enhanced, and the purpose of optimizing the particle gradation and the element distribution uniformity is achieved.

The invention provides a lithium iron phosphate positive electrode material, a preparation method thereof and a lithium ion battery. The lithium iron phosphate positive electrode material is secondary particles formed by stacking primary particles, the primary particles comprise first lithium iron phosphate particles and second lithium iron phosphate particles, the D50 of the second lithium iron phosphate particles is larger than that of the first lithium iron phosphate particles, and the difference value between the D50 of the second lithium iron phosphate particles and the D50 of the first lithium iron phosphate particles is larger than or equal to 1000 nm; each first lithium iron phosphate particle sequentially comprises a first inner core, a first coating layer and a second coating layer from inside to outside; the first inner core has a chemical formula Lix1FeMm1Pz1O4 (I) as shown in a general formula (I), and M is a first metal element; each second lithium iron phosphate particle comprises a second inner core and a third coating layer arranged on the surface of the second inner core; the second inner core has a chemical formula Lix2FeM'm2Pz2O4 (II) as shown in a general formula (II), M'is a second metal element, and the lithium iron phosphate positive electrode material has high conductivity and high compaction density.