A method for preparing battery-grade iron phosphate from lithium phosphate waste

Abstract

The invention discloses a method for preparing cell grade iron phosphate by using lithium phosphate waste. The method for preparing cell grade iron phosphate by using lithium phosphate wastecomprisesthe following steps that S1, lithium phosphate waste isprepared into slurry, sulfuric acid solution is added to prepare a mixed solution; S2, ferric salt and alkali liquor are sequentially addedto themixed solution to react under stirring, and the pH value of a reaction system is controlled to be 1.8 to 3.0 to obtain amorphous iron phosphate precipitate I and soluble lithium salt solution I; S3,an alkaline impurity removing agent is added to the soluble lithium salt solution I to adjust the pH value of the solution to 3.0 to 4.5, a solid phase partis collected to obtain iron-containing filter residue I; S4, the amorphous iron phosphate precipitate I and the iron-containing filter residue I are washed; S5, washed productsare mixed and subjected to slurrying, phosphoric acid is added, andafter the reaction is completed, aging and crystallization are conducted, and the precipitatesare washed and calcined to obtain an anhydrous iron phosphate finished product. According to the scheme,the recovery rates of lithium and phosphorus are high, and the prepared iron phosphate can be directly used as a precursor of a lithium battery material.

Description

technical field [0001] The invention relates to the technical field of resource recycling and lithium ion battery materials, in particular to a method for preparing battery-grade iron phosphate from lithium phosphate waste. Background technique [0002] Lithium phosphate is a white crystalline powder. In the industrial production process, lithium hydroxide monohydrate or lithium carbonate is usually used as raw material to prepare lithium phosphate. The prepared lithium phosphate is mainly used for the production of colored phosphors, special glass, optical disc materials, etc. In the production process of lithium and lithium compounds using lithium resources such as ore lithium and salt lake lithium, a large amount of lithium phosphate waste will be produced. Due to the low purity of this lithium phosphate waste product and the difficulty in separating impurities, it is very difficult to reuse and prepare a fluorescent agent lithium phosphate material with a specific valenc...

AI Technical Summary

Problems solved by technology

However, this method uses hydrochloric acid to dissolve lithium phosphate, which consumes a lot of acid, and hydrogen chloride gas will overflow. The operating conditions are harsh, the equipment is severely corroded, and the concentration of the mother liquor is low, which increases the energy consumption of the subsequent concentrated lithium extraction process.

In the process of precipitating phosphorus, a large amount of liquid alkali needs to be consumed, and a large amount of heat is released during the acid-base neutralization process, and some lithium phosphate will be re-precipitated, which will reduce the lithium yield; at the same time, the phosphorus resources in lithium phosphate are not well utilized. It will generate iron phosphate precipitation colloid, which is difficult to filter and wash, and will also entrain a large amount of solution

In addition, the iron phosphate produced by this operation is in an amorphous state and cannot be directly used as a precursor of lithium iron phosphate. If it is not treated, it will still occupy a lot of space

Images