Disclosed in the present invention are a novel green lithium iron phosphate precursor, a preparation method therefor and an application thereof. The preparation method comprises the following steps: S1, reacting a mixture of an iron source and a phosphoric acid solution, and grinding after the reaction is completed to obtain a product A; reacting a mixture of an organic acid solution, a lithium source, and a carbon source, and obtaining a product B after the reaction is completed, the preparation order of the product A and the product B being not limited; and S2, grinding the mixture of the product A and the product B to obtain a lithium iron phosphate precursor. In the preparation process of the lithium iron phosphate precursor, the solid content can be greatly improved, the energy consumption of the subsequent process is low, the preparation method is simple, and the cost is low.

A lithium iron phosphate positive electrode active material includes a first lithium iron phosphate material and a second lithium iron phosphate material. D.sup.1.sub.mo is a first particle size of first particles that have a largest volume distribution value of the first lithium iron phosphate material, and 0.3D.sup.1.sub.mo3.2. D.sup.2.sub.mo is a second particle size of second particles that have a largest volume distribution value of the second lithium iron phosphate material, 1D.sup.2.sub.mo5, and D.sup.1.sub.mo<D.sup.2.sub.mo. A distribution discreteness of the first particle size of the first lithium iron phosphate material is A.sub.1, and a distribution discreteness of the second particle size of the second lithium iron phosphate material is A.sub.2, where 1A.sub.13, and 2A.sub.24. D.sup.1.sub.mo and A.sub.1 meet: 4.07<A.sub.1(2.31+D.sup.1.sub.mo)<16, and D.sup.2.sub.mo and A.sub.2 meet: 0.4<A.sub.2(D.sup.2.sub.mo1.15)<14.

The present disclosure discloses a method, product, and system for cogenerating ferric phosphate through a nitrophosphate fertilizer device. The method comprises the steps of: acid-hydrolyzing phosphate rock with a nitric acid, and separating acid-insoluble substances to obtain an acid-hydrolyzed solution; freezing-crystallizing the acid-hydrolyzed solution, and carrying out solid-liquid separation to obtain a first solution; adding a solution containing sulfate ions to the first solution for reaction to obtain a second solution; subjecting the second solution to a denitrification to obtain a third solution; adding ammonia to the third solution for neutralization, and carrying out solid-liquid separation to obtain an ammonium phosphate solution, and adding an iron source to the ammonium phosphate solution for reaction to prepare a ferric phosphate. The present disclosure utilizes phosphate rock raw material to prepare a high-purity ferric phosphate, and by-product can be directly used for fertilizer preparation or as independent product, without waste.

Disclosed is a method for preparing iron phosphate dihydrate by decomplexing an iron phosphate complex. The method comprises: in an iron phosphate complex solution, adding water of 0.3-30 times, preferably 0.3-8 times the volume of the complex solution; reacting for 1 min to 20 h, preferably 10 min to 6 h; and separating the solid and liquid phases to give solid iron phosphate dihydrate. The method provided by the present invention can be used for simple, efficient, and environment-friendly preparation of iron phosphate of high purity as a positive electrode material for lithium batteries.

The present disclosure relates to a method for preparing ferroboron alloy-coated lithium iron phosphate, comprising: preparing ferrous phosphate and lithium phosphate, then mixing ferrous phosphate and lithium phosphate and adding a hydrazine hydrate solution to obtain a mixture which is then subjected to grinding, drying and then calcining to obtain a calcined mateiral, adding pure water to the calcined material and grinding the calcined material in water to obtain a slurry, to which PEG, ferrous sulfate crystals and disodium EDTA are added and stirred to dissolve, then adding a sodium borohydride solution and a sodium hydroxide solution while stirring and maintaining a pH in the process at 8.5-10.5, reacting for 15-30 min to obtain a product, and filtering, washing and vacuum drying the product to obtain the ferroboron alloy-coated lithium iron phosphate. The method may reduce interface resistance while improving conductivity, corrosion resistance, oxidation resistance and density of the product.

A method for preparing nano iron phosphate with low sulfur content. The method may include: S1: mixing a phosphorus source and an iron source to obtain a raw material solution, then adding alkali and a surfactant, adjusting a pH, and stirring and reacting to obtain an iron phosphate dihydrate slurry, S2: adding phosphoric acid solution into the iron phosphate dihydrate slurry, adjusting the pH, heating and stirring for aging, and filtering to obtain iron phosphate dihydrate, S3: adding water into the iron phosphate dihydrate for slurrying, and grinding to obtain a ground slurry; and S4: adding the ground slurry into a washing solution to wash, carrying out solid-liquid separation, and calcining a solid phase to obtain the nano iron phosphate with low sulfur content.

Disclosed is a preparation method for high-purity iron phosphate and use thereof, including: mixing and stirring an iron phosphide waste, an acid liquor, an oxidant, and an adsorbent, heating for leaching, and subjecting a resulting mixture to solid-liquid separation (SLS) to obtain a first filtrate and a first filter residue; adding an alkali liquor to the first filtrate to adjust a pH, holding a temperature of a resulting mixture, and subjecting the mixture to SLS to obtain a second filter residue and a second filtrate; and subjecting the second filter residue to a heat treatment to obtain iron oxide; subjecting the iron oxide to high-energy ball-milling, and adding a surfactant for activation to obtain a slurry; and mixing the slurry with phosphoric acid, heating to allow a reaction, subjecting a resulting mixture to SLS to obtain a solid, and washing and sintering the solid to obtain the iron phosphate.

An LFP electrode material is provided which has improved impedance, power during cold cranking, rate capacity retention, charge transfer resistance over the current LFP based cathode materials. The electrode material comprises crystalline primary particles and secondary particles, where the primary particle is formed from a plate-shaped single-phase spheniscidite precursor and a lithium source. The LFP includes an LFP phase behavior where the LFP phase behavior includes an extended solid-solution range.

The present invention relates to a method for preparing a graphene-based LiFePO.sub.4/C composite material, to solve the problem of poor conductivity and rate performance of lithium iron phosphate cathode material. The main features of the present invention include the steps of: 1) preparing an iron salt solution having graphene oxide dispersed therein; 2) preparing a ferric phosphate/graphene oxide precursor; 3) preparing the graphene-based LiFePO.sub.4/C composite material. The beneficial effects of the method is that the process is simple, easy to control and the resulted graphene-based LiFePO.sub.4/C composite material has high specific capacity, good recycle performance and excellent rate capability is particularly suitable to the field of the power battery application.

A method for preparing iron phosphate from an iron phosphorus slag includes: adding the iron phosphorus slag into an alkaline solution to carry out a reaction followed by a solid-liquid separation to obtain a residue and a first filtrate containing meta-aluminate ion and phosphate ion; adding an acid solution into the first filtrate to carry out an aluminum-removing reaction followed by a solid-liquid separation to obtain a second filtrate containing phosphate ion; mixing the residue with an acid solution to carry out a carbon-removing reaction followed by a solid-liquid separation to obtain a carbon residue and a third filtrate containing iron ion, titanium ion, and copper ion; adding metallic iron into the third filtrate to carry out a titanium and copper-removing reaction followed by a solid-liquid separation to obtain a fourth filtrate containing ferrous ion; mixing an oxidant, the second filtrate, and the fourth filtrate to carry out a reaction followed by a solid-liquid separation and a sintering process in sequence to obtain the iron phosphate.