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The basic process of phosphoric acid railway line, including the production of iron phosphate precursor, wet ball milling, spray drying and sintering, the most important of which is the production of iron phosphate precursors.

The railway line for phosphorus, iron phosphate is a precursor of LFP, its quality will directly determine the electrochemical performance of final LFP products and processing performance, made of iron phosphate, lithium iron phosphate is a major success. On the other hand, if the LFP manufacturer does not produce iron phosphate, not only the quality of products can not effectively control the source, and the supply of raw materials will also be heteronomy.

Therefore, from the perspective of production cost and product quality control, the author thinks that LFP manufacturers must produce their own iron phosphate in any case, grasp the synthesis process of iron phosphate. At present, the general iron phosphate by precipitation process of liquid phase oxidation, then the setting of process parameters directly affects the indexes of BET, particle morphology, particle size and particle size distribution of the products, iron phosphorus ratio, water content and impurity content etc..

In order to ensure consistent quality of iron phosphate, must use the continuous rather than batch reactor for the production, strictly control the reaction velocity, stirring, temperature, pH value and other factors, which requires manufacturers to continuously explore in practice. Synthesis of iron phosphate key is more difficult to control the liquid pH value, pH value changes will lead to the material morphology, particle size, microstructure and activity changes of pH and fluid flow pump by computer for real-time feedback control is a feasible way.

Iron phosphate prepared by liquid phase is actually two times by a nano particle particle accumulation, BET mainly depends on the particle size and a two particle relationship is not big, but the iron phosphate precursor surface area will directly affect the filtering and impurity of washing products. The size and morphology of primary particles of iron phosphate directly determine the morphology and size of the primary LFP particles.

Iron phosphate secondary particle size of power type LFP should be controlled at 20-40 nm, and the capacity of the grain size can be relaxed. Iron phosphorus ratio is one of the most important indicators, in general, the ratio of iron and phosphorus should be strictly controlled between 0.98-1.0. Of course, the ratio of iron to phosphorus can be adjusted before sintering, but it will affect the stability and electrochemical performance of LFP materials.

The modification of LFP doped, is the most appropriate theory of doping in the iron phosphate precursor phase, because use can achieve uniform distribution of heteroatom doped co precipitation principle, but the actual operation is not easy to accurately control the amount, it will need to carefully understand the conditions of exploration. In the author's opinion, it is feasible to apply wet doping in the iron phosphate precursor phase or dry doping at the ball milling stage.