56 results about "Iron(II) phosphate" patented technology

The invention relates to a high-compaction lithium iron phosphate positive electrode material, a preparation method thereof and a lithium ion battery, and belongs to the technical field of batteries, the method adopts a two-step synthesis method, the first step adopts ferrous phosphate high-grinding sintering to prepare first-sintering large particles, and adopts in-situ doped iron phosphate low-grinding to prepare first-sintering small particles; 2, performing high grinding on the first-fired large particles, performing low grinding on the first-fired small particles, accurately controlling the sizes of the small particles, and stripping C3N4 through grinding to form g-C3N4; the large and small particles are mixed according to a certain mass ratio, and then secondary sintering is carried out to prepare the high-compaction high-capacity long-circulation lithium iron phosphate material, the advantages of different precursors are utilized, the particle composition is optimized, and the roundness of the large and small particles is better; meanwhile, the nitrogen-doped carbon layer is prepared by taking defect-type graphene and high-molecular organic nitride which are converted from C3N4 in a secondary sintering process as carbon sources, so that the conductivity and the cycle performance of the material are improved.

The present invention relates to a modified sodium iron phosphate pyrophosphate composite material and its preparation method and application, belonging to the technical field of sodium ion batteries. The preparation method of the present invention comprises the following steps: S1, adding a soluble doped metal salt solution and a surfactant to a ferrous phosphate solution, and dripping a hydrogen peroxide solution and a hydrofluoric acid solution within 40min-80min under the conditions of 60°C-80°C, reacting at 85°C-98°C for 2h-5h after the dropwise addition, and washing and calcining to obtain a flaky composite precursor; S2, dissolving the flaky composite precursor, a sodium source, a phosphorus source, and a carbon source in water, and obtaining a modified sodium iron phosphate pyrophosphate composite material through sand milling, spray drying, and heat treatment. Element doping and material modification are successfully achieved during the precursor synthesis, thereby achieving optimization of the crystal phase, reduction of the impurity phase, improvement of the energy density, conductivity, and other physical and chemical properties of the NFPP material, and reduction of its water absorption.

The present solution provides a preparation method for a three-dimensional structured ferrous phosphate pigment with corrosion early warning capability, including following steps: preparing a ferrous ion-containing solution for providing ferrous ions, where the ferrous ion-containing solution includes a soluble ferrous salt and a surfactant but no oxidizing ions, and the ferrous ion-containing solution is maintained in an acidic environment; preparing an initial mixed solution for providing phosphate ions and ammonium ions; and performing ultrasonic refinement, heating, and holding on the intermediate mixed solution using an auxiliary device with ultrasonic oscillation and microwave heating functions to obtain a final mixed solution; and filtering out precipitates from the final mixed solution, and then transferring the precipitates to a vacuum environment for high-temperature heating treatment to obtain a three-dimensional structured ferrous phosphate pigment with corrosion early warning capability.

The invention provides a preparation method for preparing a high-compaction lithium iron phosphate positive electrode material by utilizing double-iron-source composite grade matching. The preparation method comprises the following steps: adding ferrous sulfate and phosphoric acid into pure water, and fully mixing to obtain a solution; dividing the solution into a solution A and a solution B; adding a certain amount of a metal doping source material, an oxidizing agent and phosphoric acid into the solution A, and controlling the pH to be 1-3 to obtain iron phosphate; adding a certain amount of metal doped source material and ammonia water into the solution B, and controlling the pH to be 5-6 to obtain ferrous phosphate; the preparation method comprises the following steps: respectively sanding and spraying iron phosphate and ferrous phosphate with a lithium source, a carbon source and pure water according to a molar ratio to obtain a lithium iron phosphate yellow material A and a lithium iron phosphate yellow material B; calcining the yellow material A in a furnace to obtain a precursor A, calcining the yellow material B in the furnace to obtain a precursor B, mixing the precursor A and the precursor B according to a certain mass ratio, and calcining to obtain a finished product. The method is simple in technological process, can be combined with actual production, and is very effective for improving the compaction density and the electrical property.

The invention belongs to the field of battery positive electrode materials, and particularly relates to a preparation method of a ferrous phosphate precursor, a Fe < 3 + > solution and a phosphate radical source solution with the Fe / P element ratio of 3: (1.8-2.1) are mixed and subjected to a first-stage precipitation reaction in advance, and the initial pH A of the first-stage precipitation reaction is 0.5-2; then supplementing an alkaline substance to carry out a second-stage precipitation reaction under the condition that the pH value is 2.5-5, and then carrying out solid-liquid separation to obtain an iron phosphate-Fe (OH) 3 composite material; and compounding the iron phosphate Fe (OH) 3 composite material with a carbon source, and carrying out reduction roasting treatment to obtain the ferrous phosphate precursor. The invention also comprises a preparation method and application of the material. According to the method, the performance of the prepared material can be improved, and the low-temperature and batch quality stability of the material is particularly facilitated.

The invention specifically discloses a method for preparing ferric sodium pyrophosphate by taking ferrous phosphate as a precursor. The method comprises the following steps: S100, preparing a ferrous phosphate powder precursor through a reverse titration coprecipitation method; s200, the ferrous phosphate powder precursor, sodium pyrophosphate and a carbon source are placed in a ball milling container for a ball milling reaction, and a ferric sodium pyrophosphate precursor is prepared; and S300, calcining the obtained ferric sodium pyrophosphate precursor under a second preset temperature condition, and cooling after the calcination is finished, so as to obtain the ferric sodium pyrophosphate powder. The method for preparing the ferric sodium pyrophosphate with the ferrous phosphate as the precursor is easy to operate, low in cost and beneficial to industrial production, in addition, the ferric sodium pyrophosphate prepared through the method has the advantages of being uniform in particle size, uniform in morphology and high in purity, and the method is suitable for industrial production. And when being applied to the sodium-ion battery, the sodium-ion battery shows relatively high capacity, good rate capability and excellent cycle performance.

The invention relates to the technical field of industrial solid waste resource utilization, in particular to a method for preparing ferrous phosphate octahydrate by taking pyrite cinder as a raw material, which comprises the following steps: 1) taking pyrite cinder as a raw material, and carrying out ball milling to obtain fine powder; 2) rinsing the fine powder with dilute acid and water respectively to obtain red slag; 3) mixing the red slag with a reducing agent, and calcining to obtain reducing slag; (4) under the protection of inert gas, leaching the reducing slag with sulfuric acid, filtering to obtain a leaching solution, and adjusting the iron ion concentration and the iron-phosphorus ratio to obtain an iron-phosphorus solution; (5) under the protection of inert gas, dilute alkali is added into the iron-phosphorus solution to adjust the pH value, filtering is performed after full reaction, and an iron-phosphorus purified solution is obtained; (6) under the protection of inert gas, dilute alkali is added into the iron-phosphorus purified liquid to adjust the pH value, filtering is performed after full reaction, and a filter cake is obtained; and 7) washing the filter cake, and carrying out vacuum drying to obtain ferrous phosphate octahydrate. The problems of environmental pollution and serious resource waste caused by difficult recycling of pyrite cinder can be solved.

This invention provides a lithium iron phosphate cathode material, its preparation method, and its application. The preparation method includes the following steps: (1) mixing ferrous salt and phosphorus source with an alcohol solvent, heating and stirring, and adding a first lithium source solution to obtain a mixed solution; adjusting the pH of the mixed solution to obtain a mixed precursor; (2) mixing a complexing agent, ferric salt, a second lithium source, phosphorus source, and surfactant with water, stirring to form a sol solution; mixing the mixed precursor obtained in step (1) with the sol solution, heating and stirring to obtain a gel precursor; (3) sintering the gel precursor to obtain the lithium iron phosphate cathode material; wherein the mixed precursor includes lithium phosphate and ferrous phosphate. This invention can achieve lithium iron phosphate gradation of different particle sizes through a single production line, improving the uniformity and compaction density of the material, and avoiding performance differences and poor stability between different batches.

The application provides a preparation method of high-density lithium iron phosphate positive electrode material by using double-iron-source complex level matching, and the method comprises the following steps: adding ferrous sulfate and phosphoric acid into pure water and fully mixing to obtain a solution; the solution is divided into solution A and solution B; solution A is added into a certain amount of metal doping source material, an oxidizing agent and phosphoric acid, and the pH is controlled to be 1-3 to obtain iron phosphate; solution B is added into a certain amount of metal doping source material and ammonia water, and the pH is controlled to be 5-6 to obtain ferrous phosphate; the iron phosphate and the ferrous phosphate are respectively sand-mixed, sprayed with lithium source, carbon source and pure water according to a molar ratio to obtain yellow materials A and B; the yellow material A is calcined in a furnace to obtain a precursor A, the yellow material B is calcined in a furnace to obtain a precursor B, and the precursors A and B are mixed according to a certain mass ratio and then calcined to obtain a finished product. The process flow of the application is simple, can be combined with actual production, and is very effective for improving the compaction density and the electrical performance.

A process for the production of iron phosphate, comprising the following steps: (1) Mixing an iron phosphide waste, an acidic liquid, an oxidizing agent and an adsorbent with stirring, heating to leaching and subjecting the resulting mixture to solid-liquid separation to obtain a first filtrate and a first filter residue; (2) Adding an alkaline liquid to the first filtrate to adjust the pH of the first filtrate, maintaining a temperature of the resulting mixture, and subjecting the resulting mixture to solid-liquid separation to obtain a second filter residue and a second filtrate; and subjecting the second filter residue to heat treatment to obtain iron oxide; (3) Subjecting the iron oxide to high-energy ball milling and adding a surfactant for activation to obtain a slurry; (4) Adding an extraction agent and an acidic liquid to the second filtrate obtained in step (2), carrying out an extraction and separation on a resulting mixture and subjecting a resulting organic phase to back-extraction to obtain phosphoric acid; and (5) Mixing the slurry obtained in step (3) with the phosphoric acid, heating to enable a reaction, subjecting the resulting mixture to solid-liquid separation to obtain a solid, and washing and sintering the solid to obtain the iron phosphate; where in step (1) the iron phosphide waste comprises a mixture of FeP and Fe2P; in step (1) the acidic liquid contains at least two from the following group: nitric acid, sulfuric acid and hydrochloric acid; In step (1) the oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, oxygen, nitric acid and sodium persulfate; wherein in step (2) the alkaline liquid is at least one selected from the group consisting of a NaOH solution, a KOH solution, ammonia water, a urea solution, NH4Cl, NH4HCO3, Na2CO3 and NaHCO3; In step (2) the pH of the first filtrate is adjusted to 2.5 to 5; and In step (5) the molar ratio of Fe in the slurry to P in the phosphoric acid is 1:1–2; heating to enable a reaction is carried out at a temperature of 50 °C to 80 °C for 20 to 60 min; and the iron phosphate has a D 50 from 2 µm to 6 µm, a tapped density of 0.80 g / cm³ 3 up to 1.30 g / cm³ 3 , and a specific surface area of ​​4 m² 2 / g up to 8 m 2 / g indicates.

The application provides a method for preparing cobalt-doped ferromanganese subphosphate by using iron phosphate sewage treatment sludge, and comprises the following steps: adding acid liquor into the iron phosphate sewage treatment sludge, performing acid leaching reaction, performing solid-liquid separation, and obtaining filtrate A; adding an extraction agent into the filtrate A, and performing extraction to obtain an extracted organic phase and a raffinate; performing multistage impurity removal on the raffinate to obtain a cobalt-manganese-phosphorus-containing solution, supplementing an iron source and a phosphorus source, and using a hydrothermal synthesis method to obtain a cobalt-doped ferromanganese subphosphate crude product, which is washed, dried and calcined to obtain the cobalt-doped ferromanganese subphosphate. The method can comprehensively recycle and utilize P, Mn and Co elements in the iron phosphate sewage treatment sludge, and reduces the production cost of the cobalt-doped ferromanganese subphosphate.

There is provided a method for producing ferrous sulphate and phosphoric acid comprising treating ferrous phosphate with sulphuric acid for obtaining ferrous sulphate and phosphoric acid. Additionally, there is provided a use of sulphuric acid for treating ferrous phosphate for obtaining ferrous sulphate and phosphoric acid.

The application provides a battery monomer, a preparation method thereof, a battery and a power utilization device, and belongs to the technical field of sodium batteries. The battery monomer comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode film layer, the positive electrode film layer comprises an active substance, the active substance comprises 96-99 wt% of sodium iron pyrophosphate phosphate, 0-1.9 wt% of sodium ferrous phosphate and 0.6-4 wt% of sodium iron pyrophosphate, and the mass ratio of sodium iron pyrophosphate in the active substance is greater than the mass ratio of sodium ferrous phosphate. The battery monomer of the application controls the content of the main phase and the impurity phase in the active substance in the above range, which can not only improve the compaction density of the positive electrode active material, but also is beneficial to improving the compaction density of the positive electrode sheet, and can improve the charge gram capacity and the discharge gram capacity of the positive electrode active material. When the mass ratio of sodium iron pyrophosphate in the active substance is greater than the mass ratio of sodium ferrous phosphate in the active substance, the energy density and the cycle performance of the battery monomer can be further improved.

The invention relates to the field of lithium ion battery positive electrode materials, and particularly discloses a preparation method and application of a co-doped ferrous phosphate precursor material.The preparation method comprises the steps that an antioxidant solution and a salt solution containing doped metal ions are added into a ferrite solution, and an iron source mixed solution is obtained; mixing and reacting a phosphorus source, an iron source and an alkaline solution to obtain blue ferrous phosphate slurry; and then filtering, washing, drying and crushing to obtain the doped ferrous phosphate precursor material. According to the invention, doping and morphology regulation and control are integrated in a single reaction system through a metal ion doping process, so that the preparation process is greatly simplified, and the compaction density and the rate capability of the prepared lithium iron phosphate positive electrode material are remarkably improved.

The invention discloses a carbon-coated sodium ferrous fluorophosphate positive electrode material and a preparation method thereof. A phosphorus source, an iron source, an organic carbon source, a sodium source and a surfactant are mixed, stirred and heated, a fluorine source solution is added after reaction, a conductive carbon source is added after continuous stirring, and the sodium ferrous fluorophosphate positive electrode material is obtained through dispersion, drying and high-temperature sintering. Compared with an existing synthesis method, the method provided by the invention is small in pollution and simple in process, the conductivity of the prepared positive electrode material is greatly improved after the positive electrode material is subjected to carbon coating modification, and the specific capacity can reach 80% or above of a theoretical value.

The application relates to the technical field of lithium ion batteries, in particular to a preparation method of lithium iron phosphate. The preparation method of the lithium iron phosphate comprises the following steps: reacting a mixed solution containing ferrous phosphate and ferrous biphosphate, and performing first grinding to obtain slurry; and sequentially performing second grinding, spray drying, calcination and crushing on a mixture of the slurry, a lithium source, a carbon source and a dopant to obtain the lithium iron phosphate. The two ferrous salts of the ferrous phosphate and the ferrous biphosphate are adopted, and superfine grinding can be realized under the dual action of physical grinding and chemical reaction; the generation of strong reducing gas is avoided, and the content of magnetic substances in the product is reduced. The lithium iron phosphate prepared by adopting the preparation method has the characteristics of small primary particle size, high rate performance, low powder resistivity and excellent low-temperature performance.

The invention provides an integrated multi-stage tubular reactor and a continuous reaction system, and relates to the technical field of chemical equipment, the integrated multi-stage tubular reactor comprises a reaction container, the reaction container is made of a non-metal material; the microwave heating device is arranged in the reaction container and is used for heating a solution in the reaction container; the gas stirring device is arranged in the reaction container and is used for stirring a solution in the reaction container; wherein the microwave heating devices are uniformly distributed in the reaction container. Compared with the prior art, the problem that the crystallinity of ferrous phosphate is not ideal due to uneven heating of the reaction solution can be effectively solved, the crystallization quality of ferrous phosphate is improved, and then the particle uniformity and phase purity of subsequent iron phosphate are improved.

The invention relates to a preparation method of high-purity ferrous phosphate and lithium iron phosphate, which comprises the following steps: heating dilute phosphoric acid, weighing iron powder, slowly adding the iron powder into the dilute phosphoric acid, carrying out stirring reaction, carrying out filter pressing to obtain reaction liquid, and taking filtrate to obtain a clear ferrous solution; when the temperature of the ferrous solution reaches a first temperature, adjusting the pH value of the reaction solution to a first numerical value by using ammonia water with a first concentration, preserving heat, heating the slurry, adjusting the pH value of the reaction solution to a second numerical value by using ammonia water with a second concentration, preserving heat to obtain ferrous phosphate octahydrate slurry, and carrying out filter pressing on the ferrous phosphate octahydrate slurry to obtain a ferrous phosphate octahydrate filter cake and a mother solution, the first concentration is lower than the second concentration, the first numerical value is lower than the second numerical value, and the first heat preservation time is shorter than the second heat preservation time. According to the method, phosphoric acid and iron powder are taken as raw materials, and the pH value of each stage of the reaction process is adjusted, so that the ferrous phosphate octahydrate with relatively high purity and relatively good crystallinity can be directly prepared.

The invention discloses a preparation method of lithium manganese iron phosphate with a composite polycrystalline structure. The method comprises the following steps: adding a phosphorus source and a carbon-containing substance in an amount of 3% to 10% by mass of the ferrous sulfate to a ferrous sulfate solution, reacting the mixture in an oxygen-free environment with a pH value of 5 to 10, and filtering to obtain a wet ferrous phosphate material containing carbon compounds; the carbon-containing substances comprising at least two substances; adding an oxidant and an aerogel to a manganese sulfate solution for reaction to obtain a manganese dioxide nanomaterial; mixing the graphene-containing ferrous phosphate wet material and the manganese dioxide nanomaterial, and reacting the mixture with a lithium salt and an adhesion promoter in an oxygen-free environment to obtain a lithium manganese iron phosphate precursor; and sequentially subjecting the lithium manganese iron phosphate precursor to ball milling, drying, sintering, and cooling to obtain the lithium manganese iron phosphate with the composite polycrystalline structure. The prepared lithium manganese iron phosphate has good charge and discharge performance, compaction density, and processing performance, and is worthy of promotion in the battery field.

The invention relates to ferrous phosphate based on mixed acid and iron powder and a preparation method and system thereof.The preparation method comprises the steps that dilute phosphoric acid and dilute sulfuric acid are mixed, pure iron powder is added into the mixed acid according to the ratio of n (p) to n (Fe) being (0.67-1): 1, and an iron dissolving reaction is conducted after a certain temperature is reached; taking the temperature as a starting point, sampling once every time period, analyzing the content of Fe < 2 + > in the obtained sample, and obtaining a ferrous liquid when the content of Fe < 2 + > in the sample reaches 3.5-5.0%; adding ammonia water into the ferrous liquid until the pH value of a reaction system reaches 5.0-6.5 to obtain slurry; and aging the slurry, and carrying out filter pressing, washing and drying to obtain the ferrous phosphate octahydrate. According to the method, the content of sulfate radicals in the obtained product can be effectively controlled while the use amount of phosphoric acid is reduced, the product quality is effectively improved, meanwhile, the thickness distribution uniformity of a ferrous phosphate octahydrate crystal lamellar structure is controlled, the thickness of the lamellar structure is reduced, the product quality is improved, and the compaction density of lithium iron phosphate is improved.

The present invention relates to a lithium iron phosphate material and a preparation method thereof, and a positive electrode material for lithium-ion batteries, and relates to the technical field of battery materials. The preparation method of the lithium iron phosphate material comprises the following steps: 1) a first solution containing a phosphorus source and polyethylene glycol is subjected to a co-precipitation reaction with a second solution containing an iron source to obtain a polyethylene glycol-coated ferrous phosphate precursor; 2) a third solution containing a lithium source and a polyethylene glycol-coated ferrous phosphate precursor are subjected to a hydrothermal crystallization reaction to obtain a reaction product, lithium iron phosphate; 3) the reaction product, lithium iron phosphate, is calcined under a reducing atmosphere to obtain a lithium iron phosphate material. The present invention first in-situ coats ferrous phosphate with polyethylene glycol, and uses a hydrothermal crystallization method to synthesize the reaction product, lithium iron phosphate crystals, with low antisite defects, and then calcines under a reducing atmosphere to reduce the Li + Diffusion impedance, improved electronic conductivity, and demonstrated excellent rate and capacity performance.

The present disclosure relates to the technical field of lithium ion battery cathode materials, and particularly discloses a method for preparing a carbon-coated lithium iron phosphate material from ferrous phosphate. The method comprises: mixing self-made ferrous phosphate with a carbon source, and sintering at a low temperature under nitrogen to remove a part of crystal water to obtain carbon-coated ferrous phosphate with a small amount of crystal water; evenly mixing ferrous phosphate with a lithium source, a phosphorus source and multiple carbon sources, and adjusting until a proper iron-to-phosphorus ratio is 0.960-0.975 and a carbon content is 1.5%-1.8%; subsequently drying slurry to obtain material powder; and sintering the material powder through a two-stage temperature rising curve, naturally cooling and then pulverizing to obtain the carbon-coated lithium iron phosphate material. The nano lithium iron phosphate material prepared by the method has high compaction, high capacity and long cycle performance.

The invention relates to a high-compaction lithium iron phosphate positive electrode material, a preparation method thereof and a lithium ion battery, and belongs to the technical field of batteries, the method adopts a two-step synthesis method, the first step adopts ferrous phosphate high-grinding sintering to prepare first-sintering large particles, and adopts in-situ doped iron phosphate low-grinding to prepare first-sintering small particles; 2, performing high grinding on the first-fired large particles, performing low grinding on the first-fired small particles, accurately controlling the sizes of the small particles, and stripping C3N4 through grinding to form g-C3N4; the large and small particles are mixed according to a certain mass ratio, and then secondary sintering is carried out to prepare the high-compaction high-capacity long-circulation lithium iron phosphate material, the advantages of different precursors are utilized, the particle composition is optimized, and the roundness of the large and small particles is better; meanwhile, the nitrogen-doped carbon layer is prepared by taking defect-type graphene and high-molecular organic nitride which are converted from C3N4 in a secondary sintering process as carbon sources, so that the conductivity and the cycle performance of the material are improved.

This invention discloses a method for preparing layered iron phosphate and lithium iron phosphate. The method includes: preparing a ferrous phosphate mixture; filtering the ferrous phosphate mixture to obtain a refined ferrous phosphate filtrate; taking a portion of the refined ferrous phosphate filtrate and adding crude iron phosphate seed crystals to it, mixing evenly, and using it as a reaction base solution; continuously adding the remaining refined ferrous phosphate filtrate and an oxidant to the reaction base solution in a parallel flow, and carrying out a precipitation reaction at a specific temperature; the reaction product is washed and calcined to obtain battery-grade layered iron phosphate. This invention combines "seed induction" and "co-current co-precipitation" processes to control the nucleation and growth process of iron phosphate crystals, successfully preparing a uniform, large-particle-size layered iron phosphate product. This method can prepare uniform-size, tightly packed layered iron phosphate precursors, obtaining high-density lithium iron phosphate cathode materials, while improving the production yield and reducing washing water consumption, and has good process production application value.

The invention relates to a method for preparing ferrous phosphate by using reduced titanium, which comprises the following steps: 1) detecting the components of the reduced titanium to obtain the iron content in the reduced titanium, and controlling the iron content in the reduced titanium to be 30-60wt%; (2) carrying out acid leaching on the reduced titanium by using dilute phosphoric acid, carrying out solid-liquid separation to obtain a leaching solution and filter residues, washing the filter residues with water, preparing titanium dioxide, and preparing ferrous phosphate by using the leaching solution; dilute phosphoric acid with the mass fraction of 10% is adopted during acid leaching, and the molar ratio of Fe to P is controlled to be 1: 1.9. According to the method, the titanium-iron separation efficiency of reduced titanium can be improved, and a battery-grade ferrous phosphate product with relatively high value can be obtained.

This invention discloses a method for preparing lithium iron phosphate (LFP) materials, as well as the LFP materials and their applications, belonging to the field of LFP material technology. Addressing the problems of low volumetric energy density and high production costs associated with current LFP preparation methods, this invention provides a method for preparing LFP materials. Under co-precipitation and excess phosphorus source reaction conditions, a chelating agent is first used to chelate and inhibit grain growth to prepare nano-micron-sized hydrous ferrous phosphate salts. High-temperature decrystallization treatment is then used to form anhydrous ferrous phosphate with numerous defects. During calcination in a reducing atmosphere, high-performance LFP is synthesized through secondary phosphorus supplementation and the combined effects of sufficient lithium and carbon sources.

The invention belongs to the technical field of battery material recovery and reutilization, and particularly relates to a method for preparing an iron cobaltate diaphragm based on a waste lithium iron phosphate positive electrode material and application of the iron cobaltate diaphragm. Then leaching, filtering and washing to obtain a solid product lithium iron phosphate, and aging, centrifugally washing and drying the lithium iron phosphate, and heating in a nitrogen environment to obtain an iron cobaltate product; and finally, adding conductive carbon black and polyvinylidene fluoride into iron cobaltate to prepare the iron cobaltate diaphragm. According to the method, the lithium iron phosphate LiFePO4 is recycled from the positive electrode material of the waste lithium iron phosphate battery by adopting an organic acid method, and is converted into the iron phosphate FePO4 to prepare the iron cobaltate diaphragm material, so that the effective recycling of resources is realized, the environmental pollution is reduced, and the sustainability of the battery material is improved.

The present scheme provides a preparation method of a three-dimensional structured ferrous phosphate pigment with corrosion warning capability, comprising the following steps: configuring a ferrous ion-containing solution for providing ferrous ions, wherein the ferrous ion-containing solution contains soluble ferrous salts and surfactants and does not contain oxidizing ions, and the ferrous ion-containing solution is in an acidic environment; configuring an initial mixed solution for providing phosphate ions and ammonium ions; atomizing and spraying the initial mixed solution into the ferrous ion-containing solution to obtain an intermediate mixed solution, and using an ultrasonic oscillation and microwave heating auxiliary device to ultrasonically refine, heat and keep the intermediate mixed solution warm to obtain a final mixed solution; filtering the precipitate in the final mixed solution, and transferring the precipitate to a vacuum environment for high-temperature heating treatment to obtain a three-dimensional structured ferrous phosphate pigment with corrosion warning capability, which can have corrosion warning capability.

The invention discloses a method for preparing ferrous phosphate octahydrate by using ilmenite. The method comprises the following steps: carrying out acid leaching on ilmenite, and filtering to obtain titanium slag and ferrous sulfate crude liquid; adding alkali liquor into the ferrous sulfate crude liquid to adjust the pH value, adding a filter aid and a flocculating agent, and filtering to obtain a ferrous sulfate solution; alkali liquor is added into the obtained titanium slag for stirring and pulping, a complexing agent is added for complexing leaching, and a titanium complex solution is obtained; heating, filtering and washing the titanium complex solution to obtain a precipitate, and dissolving the precipitate in a sulfuric acid solution to obtain a Ti < 4 + > dopant solution; and under an inert atmosphere, dropwise adding the Ti < 4 + > dopant solution, the phosphate solution and the alkaline solution into the ferrous base solution, adjusting the pH value to weak acidity, and reacting to obtain the titanium-doped ferrous phosphate octahydrate. According to the method, low-cost ilmenite is used as a raw material, phosphoric acid / sulfonyl modified ligand is used as a Ti < 4 + > complexing agent, uniform titanium doping of ferrous phosphate octahydrate under high pH is achieved through a coprecipitation method, the doping effect is good, the technological process is simple, and the production cost is low.

The invention relates to a method for synthesizing iron phosphate from a chip or waste liquid generated in industrial production. The method comprises the following steps: removing suspended particles through three-stage filtration, and adsorbing heavy metal ions in a solution by adopting ion exchange; the method comprises the following steps: precipitating interfering ions under a weakly acidic condition, and converting phosphoric acid into a sodium phosphate mixture under an alkaline condition; selectively adding a ferric salt compound to the obtained sodium phosphate salt solution, wherein a ferric phosphate precipitate is generated when a ferric salt is used, and a ferrous phosphate precipitate is generated when a ferrous salt is used; and carrying out centrifugal separation to obtain a ferric phosphate or ferrous phosphate precipitation product, and carrying out multi-effect evaporation on the mother liquor to recover a sodium salt byproduct. The method for synthesizing high-purity ferric phosphate and ferrous phosphate from the chip production waste liquid is realized, and sodium salt byproducts are recovered at the same time.