Preparation method of ferric phosphate with high tap density

Abstract

The invention discloses a preparation method of ferric phosphate with high tap density. The preparation method comprises: 1) synthesizing solid ferrous phosphate by using a liquid phase precipitationmethod; 2) preparing a ferrous phosphate slurry from the solid ferrous phosphate; and 3) adding a phosphoric acid and hydrogen peroxide mixed solution to the ferrous phosphate slurry in a dropwise manner, and carry out a reaction to obtain a ferric phosphate precursor material with characteristics of large particle, nearly spherical shape and high tap density. According to the present invention, the method has characteristics of simple operation, low agent consumption, less wastewater generation and high ammonia nitrogen concentration, wherein the wastewater can be subjected to evaporation condensation treatment so as to avoid the problem of high concentration ammonia nitrogen wastewater treatment.

Description

technical field [0001] The invention relates to a method for preparing iron phosphate, in particular to a method for preparing an iron phosphate precursor with large particles, nearly spherical shape, and high tap density for the synthesis of lithium iron phosphate cathode active materials for lithium ion batteries, which belongs to new energy sources The field of material preparation technology. Background technique [0002] Lithium iron phosphate has become one of the most potential battery cathode materials due to its advantages of low price, environmental protection and pollution-free, high safety and good thermal stability, so it has attracted the attention of many scientific research institutions and commercial institutions. The conductivity, tap density and stability of lithium iron phosphate are important indicators for its quality characterization, and the iron phosphate precursor (FePO 4 2H 2 O) powder, its physical and chemical properties have a great influence ...

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Problems solved by technology

[0003] FePO reported in the literature 4 2H 2 There are many methods for O synthesis, such as solid-phase synthesis, hydrothermal synthesis, co-precipitation, etc., but the only synthetic technology that has achieved large-scale industrial application is the co-precipitation method.

The main process is to use ferrous iron source, hydrogen peroxide and phosphate as raw materials to synthesize FePO 4 2H 2 O powder, there are following deficiencies in this technology: 1) due to Fe 2+ 、PO 4 3- and H 2 o 2 The ion concentration in the coexistence solution system is high, the nucleation rate is large, and the FePO formed by precipitation 4 2H 2 O particle diameter is small, the product tap density is low

2) To avoid Fe 3+ Ferric hydroxide is formed by hydrolysis, resulting in a high Fe / P ratio, requiring a large excess of phosphate and controlling a low pH value. The acidity of the solution after precipitation is high, and the utilization rate of phosphorus resources is low.

3) The precipitation process produces a large amount of high-concentration ammonia-nitrogen wastewater containing sulfate, hydrogen ions, and hydrogen phosphate, which can only be neutralized with lime to form a large amount of solid waste containing calcium sulfate and calcium phosphate, and the liquid after nitrogen blowing must be carried out. Advanced treatment to remove ammonia nitrogen can meet the emission standards, and the cost of environmental protection is very high

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