Process for producing iron phosphate for producing iron lithium phosphate material

Abstract

The preparation method of iron phosphate used for preparing lithium iron phosphate material in the present invention relates to heavy metal phosphate, and the steps are: dissolving analytically pure soluble iron salt in distilled water to prepare a 0.05-5M aqueous solution, and the added mass is the iron salt mass 0.01~3% of anionic surfactant, then add analytically pure phosphoric acid according to the molar ratio of Fe3+:PO43-=1:0.8~1.2 and stir evenly, and slowly add alkaline solution with a concentration of 1~9M under stirring , the feeding time is more than 1 hour, until the pH value of the solution reaches 6-7, the iron phosphate precipitate is filtered, and the filtered iron phosphate is washed 3-5 times with distilled water 2-5 times its weight. Dry at ~90°C to obtain the product FePO4·2H2O powder. The iron phosphate product with two crystal waters prepared by the method of the invention has high reactivity, and the performance of the lithium iron phosphate material made by using it is better than that of the lithium iron phosphate material made by commercially available iron phosphate products.

Description

Technical field [0001] The technical scheme of the present invention relates to heavy metal phosphates, in particular to a method for preparing iron phosphate for preparing lithium iron phosphate materials. Background technique [0002] Lithium iron phosphate has high theoretical capacity (170mAh / g), high working voltage (voltage platform around 3.5V), and appropriate mass density (3.64g / cm 3 ), small self-discharge, LiFePO at low current density 4 Li in + Almost 100% embedding / de-embedding, long cycle life, good cycle performance, no memory effect, low price, good thermal stability, environmental friendliness, etc. It is expected to replace the higher-cost LiCoO 2 Become a new generation of lithium-ion battery cathode material. [0003] At present, the solid-phase reaction method is the main method for the synthesis of lithium iron phosphate materials. In the preparation methods of lithium iron phosphate materials disclosed in CN 1581537, CN 1753216, CN 1958440, CN 1958441 and C...

AI Technical Summary

Problems solved by technology

The ferric phosphate material with two crystal waters produced by the method of the present invention has a crystal structure similar to lithium iron phosphate, which overcomes the problem that commercially available ferric phosphate products have a complete grain structure, low reactivity, and lithium ion It is very difficult to diffuse in it, and it is difficult to insert lithium ions in the subsequent sintering process to form the shortcomings of lithium iron phosphate crystals suitable for lithium-ion battery cathode materials, thereby improving the performance of lithium iron phosphate materials