Preparation method of battery-grade iron phosphate

Abstract

The invention discloses a preparation method of battery-grade iron phosphate. The preparation method comprises the following steps: preparing a ferrous sulfate solution of which the mass percent of iron is 5.0-10.0%, adding an oxidizing agent and H3PO4 for oxidizing Fe <2+> into Fe <3+> to form a mixed solution of phosphoric acid and ferric sulfate, adding water to adjust the pH value to 1.5-2.5,performing a reaction to obtain iron phosphate precipitate, and washing, filtering, and drying and calcining a filter cake to obtain battery-grade iron phosphate. According to the invention, reactionpH is adjusted through pure water dilution; instead of adjusting the pH by ammonia water in a conventional route the product quality can be ensured and implementation of zero emission of ammonia nitrogen is achieved; no solid by-product is generated, the prepared battery-grade iron phosphate material is low in impurity content, dilute sulfuric acid in wastewater can be recycled through concentration, condensate water generated by heating evaporation can also be recycled for diluting and adjusting the pH value of a phosphoric acid and ferric sulfate mixed solution, zero emission of wastewater is achieved, and energy consumption and production cost are reduced.

Description

technical field [0001] The invention relates to the technical field of iron phosphate production, in particular to a method for preparing battery-grade iron phosphate. Background technique [0002] The synthesis process routes of lithium iron phosphate, the cathode material of lithium ion batteries, include hydrothermal process, ferrous oxalate process, iron red process, and iron phosphate process. The iron phosphate process has gradually become the mainstream route for lithium iron phosphate production due to its good batch stability and excellent electrochemical performance. Battery-grade iron phosphate usually adopts the following two production processes: 1. Using ferric salts such as iron sulfate Fe 2 (SO 4 ) 3 , Fe(NO 3 ) 3 , ferric chloride (FeCl 3 ) is the iron source, and H 3 PO 4 or NH 4 h 2 PO 4 Mix according to a certain ratio, then add ammonia water to adjust temperature and pH value, so that Fe 3+ with PO 4 3- Combined and precipitated, press filt...

AI Technical Summary

Problems solved by technology

There is following shortcoming in said method: production mother liquor is in high ammonia nitrogen waste water, as (NH 4 ) 2 SO 4 , NH 4 Cl, NH 4 NO 3 , at the same time to ensure that the anions (such as SO 4 2- , Cl - , NO 3- ) content is low, it is usually necessary to use a large amount of pure water to wash the ferric phosphate filter cake after press filtration, thereby producing a large amount of ammonia nitrogen (such as (NH 4 ) 2 SO 4 , NH 4 Cl, NH 4 NO 3 ) waste water

If this kind of high ammonia nitrogen mother liquor and washing wastewater are directly discharged, it will cause serious pollution to the environment, such as wastewater treatment, it will consume a lot of energy, and the value of by-products is very low

Prior art CN109368612A discloses a method for preparing battery-grade iron phosphate by using ferric phosphate production wastewater, which effectively utilizes phosphate radicals in ferric phosphate production wastewater, but is not aimed at solving the problem of high ammonia nitrogen wastewater caused by it

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