1545 results about "Manganese phosphate" patented technology

The invention discloses a preparation method of a high-compaction lithium manganese iron phosphate positive electrode material, which comprises the following steps: placing a manganese source, an iron source and a phosphorus source in deionized water, stirring, carrying out primary high-speed ball milling, carrying out constant-temperature water bath, adding an oxidizing agent, stirring and oxidizing, and drying the slurry to obtain manganese iron phosphate precursor powder; carrying out primary sintering on the ferromanganese phosphate precursor powder to obtain a ferromanganese phosphate primary sintering material; putting the ferromanganese phosphate primary sintering material into deionized water, adding a lithium source and a carbon source at the same time, and performing stirring, secondary high-speed ball milling and drying to obtain lithium ferromanganese phosphate precursor powder; and carrying out secondary sintering on the lithium manganese iron phosphate precursor powder to obtain the high-compaction lithium manganese iron phosphate positive electrode material. The void ratio is well reduced and good carbon coating is realized by means of secondary grinding and secondary sintering, and compared with the prior art, the method has the advantages that good capacity can be maintained, the powder compaction density of the material can be improved, the conductivity can be improved, and the specific surface area of the material can be effectively reduced.

The invention discloses a lithium manganese iron phosphate positive electrode material with a core-shell structure, which is prepared by the following steps: mixing a manganese source, an iron source, a phosphorus source, lithium carbonate and a carbon source, grinding and drying to prepare a pre-sintered material; then carrying out gas crushing on the pre-sintered material to obtain a pre-gas crushed material, and carrying out heat preservation at the temperature of 200-600 DEG C; putting the pre-gas crushed material subjected to heat preservation into an iron salt solution for quenching reaction to obtain iron compound coated lithium manganese iron phosphate; and finally, mixing the lithium iron manganese phosphate coated with the iron compound, a lithium source, a phosphorus source and a carbon source, grinding, drying, and carrying out secondary calcination to obtain the lithium iron manganese phosphate material with the core-shell structure. During preparation of the lithium manganese iron phosphate positive electrode material, a lithium manganese iron phosphate pre-sintered body and an iron salt solution are subjected to a quenching reaction to form an iron compound coated lithium manganese iron phosphate pre-sintered body, and then the iron compound coated lithium manganese iron phosphate pre-sintered body and other raw materials of lithium iron phosphate are subjected to a secondary calcination reaction to generate the composite positive electrode material with a core-shell structure. A coating structure is formed, the reaction between manganese and electrolyte is reduced, the dissolution of manganese is inhibited, the Gingtaler effect of manganese is relieved, and the stability of the material is improved; and the material has the advantages of high energy density, high power density, excellent cycle performance and strong core-shell interface bonding force.

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises an electrode assembly, wherein the electrode assembly comprises a positive plate, a negative plate and a non-aqueous electrolyte; the positive plate comprises a positive current collector and a positive film layer, and the negative plate comprises a negative current collector and a negative film layer; the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises a lithium manganese iron phosphate material and a nickel cobalt lithium manganate material; in the nickel cobalt lithium manganate material, the molar ratio of Ni in the sum of the three elements of Ni, Co and Mn is 0.5-0.95; the non-aqueous electrolyte comprises vinylene carbonate, and the mass content of the vinylene carbonate in the non-aqueous electrolyte is 0.5%-2%; the non-aqueous electrolyte comprises at least one of linear carbonic ester and linear carboxylic ester, and the conductivity of the non-aqueous electrolyte is 9-14 mS / cm. The energy density, the cycle performance and the power performance of the battery monomer are improved at the same time.

The invention provides a lithium iron manganese phosphate positive electrode material and a preparation method and application thereof, the lithium iron manganese phosphate positive electrode material comprises a doped type iron manganese phosphate inner core and a coating layer coating the surface of the doped type iron manganese phosphate inner core, and the coating layer is a lithium-containing carbon layer; the doped iron manganese phosphate inner core comprises doped ions, and in the particles of the doped iron manganese phosphate inner core from inside to outside, the content gradient of manganese ions and iron ions is reduced, and the content gradient of the doped ions is increased. According to the lithium manganese iron phosphate positive electrode material with the structure, a series of problems caused by poor phase structure stability, poor conductivity and Jahn-Teller effect and manganese dissolution of the material in the lithium manganese iron phosphate positive electrode material can be effectively improved; further, the conductivity of the lithium manganese iron phosphate positive electrode material and the comprehensive performance of gram volume, cycling stability and the like when the lithium manganese iron phosphate positive electrode material is applied to a battery are improved.

The invention provides a lithium ion battery and electric equipment, the lithium ion battery comprises a positive pole piece and an electrolyte, active substances in the positive pole piece comprise a phosphate lithium positive pole material and nickel cobalt manganese lithium oxide, and the electrolyte comprises a positive pole film-forming agent, a negative pole film-forming agent and a lithium salt, the lithium salt comprises lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide, the lithium ion battery meets the following formula: # imgabs0 #, NL is the mass ratio of the lithium nickel cobalt manganese oxide to the lithium phosphate positive electrode material, Salt is the sum of the molar concentrations of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide in the electrolyte by taking mol / L as the unit, and the sum of the molar concentrations of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide in the electrolyte is the sum of the molar concentrations of the lithium hexafluorophosphate and the lithium bis (fluorosulfonyl) imide. Add is the mass ratio of the positive electrode film-forming agent to the negative electrode film-forming agent. When the ternary material is doped in the lithium manganese iron phosphate or the lithium iron phosphate, the proportion of the positive and negative electrode film-forming agents and the proportion of the heat-resistant high-lithium salt can be adjusted according to the mixing proportion of the lithium manganese iron phosphate and the lithium iron phosphate, so that the cycle performance of the battery is improved.

The invention provides a lithium manganese iron phosphate battery. The battery comprises a positive pole piece, a negative pole piece and a non-aqueous electrolyte, the positive pole piece comprises a positive active material and a positive active coating arranged on at least one surface of the positive active material; the positive electrode active material comprises lithium manganese iron phosphate LiMnxFe1-xPO4 coated with a carbon coating layer, and x is more than or equal to 0.5 and less than or equal to 0.8; the negative pole piece comprises a negative active material and a negative active coating arranged on at least one surface of the negative active material; the battery satisfies the following relational expressions: 4.5 < = (a / 20 + d) / (b + c) < = 12.8; a is a coated diaphragm resistor of the positive pole piece; b is the compaction density of the positive pole piece; c is the mass percentage content of vinylene carbonate in the positive electrode slurry; and d is the mass percentage content of the lithium bis (fluorosulfonyl) imide in the non-aqueous electrolyte. By optimizing the composition of the lithium ion battery, the low-temperature discharge performance of the battery is improved, and meanwhile, the high-temperature cycle performance is considered.

Provided are a lithium manganese iron phosphate material and a preparation method therefor, a positive electrode sheet, and a lithium ion battery. The lithium manganese iron phosphate material comprises a core and a coating layer that coats the surface of the core. The chemical formula of the material of the core is LiaMnbFecMdPO4, wherein M comprises at least one element among magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum. The coating layer is formed by sintering a carbon source, and the carbon coating layer comprises graphitized carbon.

The invention provides a positive active material and a preparation method thereof, a positive plate and a battery, and belongs to the technical field of batteries, the positive active material comprises a ternary material and lithium manganese iron phosphate; wherein the mass of the lithium manganese iron phosphate is A, the total mass of the ternary material and the lithium manganese iron phosphate is B, and A / B is more than 0 and less than 50%; the lithium manganese iron phosphate is of a hollow spherical structure, and the median particle size of the lithium manganese iron phosphate is 0.5-3 microns. According to the positive electrode active material provided by the embodiment of the invention, the cost of the positive electrode active material can be reduced, relatively high rate capability, cycle performance and energy density are considered, and the comprehensive electrochemical performance is improved.

The invention relates to the technical field of electrochemistry, and particularly discloses a positive pole piece, an electrochemical device comprising the positive pole piece and an electric device. The positive pole piece comprises a first active material with a particle size of 4-20 [mu] m and a second active material with a particle size of 200-600 nm, the first active material comprises lithium manganese iron phosphate with the manganese content of m%, the second active material comprises lithium manganese iron phosphate and / or lithium iron phosphate with the manganese content of n%, and m and n meet the condition that m-n is larger than or equal to 15 and smaller than or equal to 85. According to the invention, by controlling the particle size distribution in the positive electrode active material and the manganese content relationship, the electrochemical device containing the positive electrode plate has excellent fast charging performance and energy density.

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 belongs to the technical field of new energy materials, and particularly relates to a low-sulfur metal cation doped ammonium manganese ferric phosphate precursor, carbon-coated modified sodium manganese ferric pyrophosphate and a preparation method and application thereof. According to the invention, the low-sulfur metal cation doped ammonium manganese ferric phosphate precursor is successfully prepared. A proper amount of phosphoric acid source is added into the prepared metal cation doped ammonium manganese ferric phosphate precursor for treatment, so that the sulfur content of the precursor is remarkably reduced, and the molar ratio of manganese, iron, doped elements and phosphorus elements is regulated and controlled to be slightly smaller than 1. The atomic-scale distribution of elements in the precursor is realized, the tap density is also improved, and the subsequent preparation of a high-performance carbon-coated modified manganese ferric sodium phosphate pyrophosphate material is facilitated. The sodium ion battery constructed based on the material has excellent charge-discharge capacity, capacity retention ratio and cycling stability. In addition, the preparation method of the precursor is simple and convenient to operate and easy to control, and has the advantage of wide application.

The invention discloses a gradient composite coated modified lithium manganese iron phosphate positive electrode material and a preparation method thereof, and belongs to the technical field of positive electrode materials. An LMFP precursor is pretreated through a citric acid-ethanol mixed solution, an active crystal face is exposed, and then a three-dimensional gradient coating structure of a polydopamine (PDA) chemical bonding layer, an MXene nanosheet middle layer and a polyaniline (PANI) conductive outer layer is sequentially constructed on the surface of the material, so that the electronic conductivity of the lithium manganese iron phosphate positive electrode material is increased to 10 <-3 > S / cm magnitude, and the performance of the lithium manganese iron phosphate positive electrode material is improved. The capacity retention ratio (1C) of 500 cycles is larger than 90%, the coating layer is not prone to falling off, and meanwhile dissolution of manganese ions is effectively inhibited.

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 discloses a method for preparing a manganese iron phosphate precursor by recycling waste lithium manganese iron phosphate, and belongs to the technical field of lithium ion batteries. The invention provides a method for preparing a manganese iron phosphate precursor by recycling waste lithium manganese iron phosphate, which comprises the following steps: by taking waste lithium manganese iron phosphate battery powder as a raw material, carrying out acid dissolution and filtration to remove graphite and part of impurities; adjusting the pH value of the filtrate to obtain a lithium-ion-rich solution and a ferromanganese precipitate, and adding sodium carbonate into the lithium-ion-rich solution for concentration and crystallization to obtain battery-grade lithium carbonate; carrying out acid dissolution on the ferromanganese precipitate, removing copper and aluminum impurities in the solution, adjusting the ratio of ferromanganese to phosphorus, and mixing with liquid caustic soda in a nitrogen atmosphere to obtain a ferromanganese phosphate precursor; according to the method, the problems of incomplete recovery and insufficient impurity removal of the manganese iron phosphate lithium battery are solved, the battery-grade lithium carbonate and the manganese iron phosphate precursor are prepared during recovery, the value of the recovered product is improved, and the production requirement of the lithium ion battery is met.

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises an electrode assembly, wherein the electrode assembly comprises a positive plate, a negative plate and an isolating membrane positioned between the positive plate and the negative plate; the negative plate comprises a negative current collector and a negative active layer located on at least one side of the negative current collector, the negative active layer comprises a negative material, the negative material comprises a negative active material, and the negative active material comprises graphite; the positive plate comprises a positive current collector and a positive active layer positioned on at least one side of the positive current collector, the positive active layer comprises a positive material, the positive material comprises a positive active material, and the positive active material comprises lithium iron phosphate and a lithium manganese iron phosphate material; the surface density of the positive electrode active layer is 200 to 370 mg / 1540.25 mm < 2 >; and when the battery monomer is in a 100% SOC state, the compaction density of the positive electrode active layer is 2.27-2.67 g / cm < 3 >. The battery monomer has the advantages of low cost, high energy density and long cycle life.

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 relates to a lithium manganese iron phosphate positive electrode material and a preparation method thereof, a positive plate and a battery, and belongs to the technical field of methods or devices for directly converting chemical energy into electric energy. The lithium manganese iron phosphate positive electrode material comprises an inner core, a first coating layer arranged on the surface of the inner core and a second coating layer arranged on the surface of the first coating layer, the inner core is lithium manganese iron phosphate I, the first coating layer comprises lithium manganese iron phosphate II, and the second coating layer comprises a carbon material and an inorganic solid electrolyte. The lithium manganese iron phosphate positive electrode material not only can endow a battery with relatively high energy density, but also can endow the battery with excellent cycle performance.

The invention provides a modified lithium iron manganese phosphate positive electrode material, a preparation method thereof and a lithium ion battery, and relates to the technical field of lithium ion battery materials. The positive electrode material comprises a phosphorus source, an iron source, a manganese source, a lithium source and a magnesium source. Mixing a titanium source solution, carrying out hydrothermal reaction, centrifugally washing and drying to synthesize the lithium manganese iron phosphate, and coating polypyrrole and a glucose carbon layer to improve the electronic conductivity of the lithium manganese iron phosphate. The magnesium-titanium co-doped stable crystal structure is introduced, the lithium ion diffusion path is shortened, the dissolution of the manganese element is inhibited, the structural change in the charging and discharging process is reduced, the side reaction with the electrolyte is inhibited by coating the cobalt boride, and the electrochemical performance of the lithium manganese iron phosphate is improved. The primary nano-particles improve ionic conductivity, and the secondary nano-particles are nano-particles formed by assembling the primary nano-particles and have the advantages of being good in rate capability, high in compaction density and high in tap density.

The invention belongs to the technical field of lithium ion battery materials, and discloses a bismuth silicate coated lithium ferric manganese phosphate material, a preparation method thereof and a lithium ion battery. The bismuth silicate coated lithium ferric manganese phosphate material comprises lithium ferric manganese phosphate and a coating layer coating at least part of the surface of the lithium ferric manganese phosphate, and the coating layer is made of bismuth silicate. Carrying out ball-milling mixing on the ferric manganese phosphate material, a lithium source, a carbon source and water to obtain mixed slurry; performing low-temperature spray drying on the mixed slurry to obtain a spray material; and carrying out wet mixing on a silicon source, a bismuth source and the spray material, carrying out high-temperature pyrolysis on the wet-mixed material in a spray pyrolysis furnace, and sintering to obtain the bismuth silicate coated lithium ferric manganese phosphate material. When the bismuth silicate coated lithium ferric manganese phosphate material is used as a positive electrode active material of a lithium ion battery, the high-temperature cycle performance of the battery can be improved while the high discharge capacity of the battery is ensured.

The invention provides a positive electrode active material as well as a preparation method and application thereof. The positive electrode active material comprises secondary particles consisting of primary particles, each primary particle comprises an inner core and a carbon coating layer arranged on at least part of the surface of the inner core; the inner core comprises a solid solution formed by lithium iron manganese phosphate and lithium manganate; the primary particles comprise primary particles A and primary particles B, the particle size of the primary particles A is 50-200nm, and the median particle size D50 is 80-120nm; the particle size of the primary particles B is 400-800 nm, and the median particle size D50 is 500-600 nm. The positive electrode active material has relatively high powder compaction density and ion transmission capability, and the electrochemical performance and energy density of the lithium ion battery can be effectively improved.

The invention provides a preparation method of a lithium manganese iron phosphate material, and relates to the technical field of positive electrode materials. The preparation method of the lithium manganese iron phosphate material comprises the following steps: mixing a first raw material component consisting of ferromanganese oxalate, a first lithium source, a first phosphorus source, a first carbon source and a first doping agent, adding deionized water, grinding, and then carrying out spray drying to obtain a precursor A; mixing a second raw material component consisting of carbon-coated ferromanganese oxalate, a second lithium source, a second phosphorus source, a second carbon source and a second doping agent, adding deionized water, grinding, and performing spray drying to obtain a precursor B; and uniformly mixing the precursor A and the precursor B, sintering in an inert atmosphere, and crushing to obtain the lithium manganese iron phosphate material. According to the lithium manganese iron phosphate material, on the premise of ensuring high specific capacity, relatively high compaction density and relatively high rate capability are realized at the same time.

The preparation method comprises the following steps: (1) taking a manganese source, an iron source, a phosphorus source and a lithium source according to the molar ratio of Mn: Fe: P: Li = x: (1-x): 1: (1.0-1.1), x is more than or equal to 0.3 and less than or equal to 0.7, and taking 15-25% of a carbon source according to the mass of the product lithium manganese iron phosphate; the lithium source comprises a first lithium source and a second lithium source, and the melting point of the first lithium source is lower than that of the second lithium source; (2) grinding and mixing the manganese source, the iron source, the phosphorus source, the first phosphorus source and half of the carbon source, drying, and carrying out a first sintering reaction at a temperature higher than the melting point of the first lithium source and lower than a second sintering reaction temperature to obtain a sintered material; and (3) grinding and mixing the sintered material, a second lithium source and the remaining half part of the carbon source, drying, and carrying out a second sintering reaction to obtain the lithium manganese iron phosphate positive electrode material at a second sintering temperature lower than the melting point of the second lithium source. According to the method, lithium sources with different melting points are added in batches, the sintering temperature is controlled, lithium manganese iron phosphate phases are sequentially generated and mutually restricted, the particle size difference is formed, and the compaction density and capacity are improved.

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.

A preparation method for a lithium manganese iron phosphate positive electrode material, comprising the following steps: (1) uniformly stirring an iron source, a phosphorus source, a lithium source and a dispersing agent in water, adding a manganese source, and uniformly mixing same to obtain a precursor pre-slurry; and (2) adjusting the solid content of the precursor pre-slurry to reach a target solid content A, the target solid content A satisfying 30 wt% ≤ A ≤ 60 wt%; (3) carrying out primary grinding treatment on the precursor slurry obtained in step (2); and (4) adding an organic phosphine scale and corrosion inhibitor to the precursor slurry, dissolving same, then drying the obtained slurry, and performing sintering and crushing to obtain the lithium manganese iron phosphate positive electrode material. Also provided is a positive electrode material prepared by the method.

According to the impurity removal method for the ferrophosphorus slag, impurities such as Al, Cu, Ti, carbon and organic electrolyte in the ferrophosphorus slag can be effectively removed through the method. The method comprises the following steps: (1) carrying out high-temperature calcination on ferrophosphorus slag A and chloride under a reduction condition to obtain ferrophosphorus slag B; (2) leaching the ferrophosphorus slag B to obtain ferrophosphorus liquid A and filter slag A; (3) adding sodium fluoride into the ferrophosphorus liquid A to obtain ferrophosphorus liquid B and filter residues B; and (4) adding iron powder into the ferrophosphorus liquid B, and carrying out solid-liquid separation to obtain the high-purity ferrophosphorus liquid. Meanwhile, the invention provides a method for preparing a ferromanganese phosphate precursor and an iron phosphate precursor by adopting the high-purity ferrophosphorus liquid obtained by the method.

The invention discloses an electrolyte adaptive to a lithium iron manganese phosphate positive electrode material and a battery, and belongs to the technical field of batteries. The electrolyte comprises a non-aqueous solvent, a lithium salt and a negative electrode film-forming additive, the mass ratio a of the total mass of the dimethyl carbonate and the carboxylic ester in the non-aqueous solvent, the molar ratio b of the lithium bis (fluorosulfonyl) imide in the lithium salt, the molar ratio y of manganese in the lithium manganese iron phosphate and the compaction density c of the positive pole piece meet the relational expression: # imgabs0 # 0.01 < = a < = 1; 0.01 < = b < = 1; 1.8 < = c < = 2.7 in g / cm < 3 >; the molecular formula of the lithium manganese iron phosphate is LixMnyFe1-yPO4, x is more than or equal to 0.95 and less than or equal to 1.05, and y is more than or equal to 0.3 and less than or equal to 0.8; and the mass ratio d and y of the negative electrode film-forming additive in the electrolyte meet the relational expression that (100 * d) / y is greater than or equal to 3 and less than or equal to 20, and d is greater than or equal to 0.001 and less than or equal to 0.2. The electrolyte can improve the deposition phenomenon of manganese ions on a negative electrode and improve the conductivity and the dynamic performance.

The invention provides a lithium manganese iron phosphate precursor hydrate which comprises a mixture of manganese phosphorus ore phase manganese manganese phosphate and ammonium manganese iron phosphate, and the molar ratio of the manganese phosphorus ore phase manganese manganese phosphate to the ammonium manganese iron phosphate is (1: 9)-(1: 1). A precursor material obtained by roasting the precursor hydrate is uniform in manganese and iron element distribution and good in processability, and lithium manganese iron phosphate with relatively high compaction density, relatively high capacity and better comprehensive performance can be prepared. The invention also provides a preparation method of the lithium iron manganese phosphate precursor hydrate, a lithium iron manganese phosphate precursor, lithium iron manganese phosphate and a secondary battery.

The invention discloses a lithium manganese iron phosphate positive electrode material coated with a carbon layer based on a CVD (chemical vapor deposition) method and a preparation method, the preparation method comprises the following steps: forming a uniform carbon coating layer on a lithium manganese iron phosphate precursor based on a CVD coating process, mixing the lithium manganese iron phosphate precursor with the uniform carbon coating layer and a lithium salt, and carrying out co-sintering, and the lithium salt can permeate through the carbon layer to form a lithium-doped uniform carbon coating layer. According to the method, the coating effect is improved, the problem that uniform coating cannot be formed on the surface of the precursor in a traditional carbon coating process is effectively solved, precipitation of trivalent manganese ions at a high temperature can be slowed down, the problem that the capacity exertion is reduced due to the fact that an amorphous carbon layer formed by a CVD cracking coating process affects lithium ion deintercalation is solved, and the performance of the lithium ion battery is improved. The safety and the service life of the battery are improved.

The invention relates to a phosphoric acid pyrophosphate composite polyanionic positive electrode material for a sodium-ion battery, a preparation method and application of the positive electrode material in the sodium-ion battery. The pyrophosphate composite polyanionic positive electrode has a structure as shown in a formula I: Na4Fe3-x-1. 5y-zMnxVyAz (PO4) 2P2O7 (at) C; when the pyrophosphate composite polyanionic positive electrode has the structure as shown in the formula I, x is more than 1.5 and less than 2.8; and 2) A is selected from one or two of Mg < 2 + >, Al < 3 + >, Cr < 3 + >, Ga < 3 + >, Co < 2 + >, Ni < 2 + >, Cu < 2 + >, Zn < 2 + >, Ge < 2 + >, Zr < 4 + >, Nb < 3 + / 4 + >, Mo < 3 + >, In < 3 + >, Sn < 4 + >, Sb < 3 + >, Te < 4 + >, Ce < 4 + >, Pr < 4 + >, Nd < 3 + >, Pm < 3 + >, Ta < 3 + / 4 + >, W < 4 + >, Bi < 5 + >, Po6 < + >, Cm < 4 + > and Bk < 4 + >. The ionic conductivity and the electronic conductivity of the material are improved through unit cell structure regulation and