Provided are a positive electrode active material and a preparation method therefor, a battery cell, and an electric device. The positive electrode active material includes a lithium-containing phosphate, where an X-ray diffraction pattern of the positive electrode active material tested in a fully charged state satisfies: there is a (311) crystal plane peak in a range of 35 to 36 and a (011) crystal plane peak in a range of 20 to 21, and the ratio of a peak intensity I.sub.311 of the (311) crystal plane peak to a peak intensity I.sub.011 of the (011) crystal plane peak satisfies I.sub.311/I.sub.0110.008. The positive active material can improve the cycle performance of a battery.

Disclosed are a preparation method and application of iron phosphate. The preparation method comprises: subjecting iron phosphate waste to calcination, dissolving it in an acid solution, and filtering to obtain filtrate, namely a solution A containing iron phosphorus; stirring a mixed solution of the solution A and a first alkali solution, adjusting pH of the mixed solution to acidity for reaction, and after washing and filtering to obtain second filter residue, namely an amorphous yellow iron phosphate filter cake; subjecting the yellow iron phosphate filter cake to aging and heating, adding phosphoric acid and a second alkali solution for reaction, followed by washing and filtering to obtain third filter residue, namely a basic ammonium iron phosphate filter cake, then drying to obtain basic ammonium iron phosphate crystal powder; and subjecting the basic ammonium iron phosphate crystal powder to calcination for dehydration and cooling to obtain iron phosphate.

The present application relates to the technical field of preparation of a lithium-ion cathode material, and discloses a lithium iron phosphate cathode material, a preparation method thereof, and a lithium-ion battery. Based on X-ray Diffraction (XRD) test, the lithium iron phosphate cathode material has diffraction characteristic peaks at 2.sub.A1=29.4 to 29.6, 2.sub.A2=29.8 to 30, and 2.sub.A3=43.8 to 43.9. As the lithium iron phosphate cathode material has specific diffraction characteristic peaks based on XRD test, the lithium iron phosphate cathode material can have a high pallet density, thereby significantly improving electrochemical performances such as capacity and cycle performance of the lithium-ion battery assembled from the lithium iron phosphate cathode material.

A method for preparing a positive electrode active material is provided. The method for preparing a positive electrode active material may comprise the steps of: preparing a lithium precursor, an iron precursor, a phosphorus precursor, and abase solvent; mixing the base solvent and the lithium precursor to prepare a first source, mixing the base solvent and the iron precursor to prepare a second source, and mixing the base solvent and the phosphorus precursor to prepare a third source; and mixing the first source, the second source, the third source, and a chelating agent and allowing a reaction to occur in the mixture by a heat treatment method to prepare a positive electrode active material comprising a compound of lithium, iron, phosphorus, and oxygen.

The invention belongs to the field of battery material recovery, and discloses a preparation method and application of heterosite phosphate. The method comprises the following steps: mixing lithium iron phosphate with a solvent, adding an acid solution, and adjusting the pH to obtain an acidic lithium iron phosphate liquid; adding a transition metal additive to the acidic lithium iron phosphate liquid, and performing leaching in an intensifying micro-environment, followed by filtrating to obtain heterosite iron phosphate and a lithium-rich solution. The leaching rate of lithium in the leaching solution reaches 90.5-99.9%, and both of the iron and phosphorus content in the leaching solution are less than 0.1 ppm; the recovered heterosite iron phosphate has a purity of 99.9%, and the recovery rate of the heterosite iron phosphate is 99.3%.

A positive electrode material, a preparation method thereof and application thereof are provided. The positive electrode material includes secondary particles formed by the agglomeration of primary particles, and each of the primary particles includes an active material having a chemical formula of LiM.sub.z(Mn.sub.xFe.sub.1-x).sub.1-z(BO.sub.3).sub.y(PO.sub.4).sub.1-y, where M includes at least one of Mg, Ti, Nb, Al, Ni, and a rare earth element, 0.4x0.7, 0.0025y0.01, and 0z0.003; boron element in the primary particles has a mass percentage of 0.5% to 1%, and BO bonds are provided between adjacent primary particles. In the positive electrode material, by introducing boron element into the active material, BO bonds are formed between adjacent primary particles in the positive electrode material. The fluxing effect of the BO bonds may enhance the compactness between the primary particles, reduce the spacing between adjacent primary particles.