Preparation method and application of iron phosphate

Abstract

The invention belongs to the technical field of lithium ion battery positive electrode materials, and particularly provides a preparation method of iron phosphate which is low in cost, low in specific surface area (less than 3m < 2 > / g), low in impurity content, high in performance and suitable for industrial production and application of the iron phosphate. According to the method, the iron source and the phosphoric acid react under certain conditions such as low temperature, then the filtrate after the reaction and the hydrogen peroxide are subjected to oxidation reaction, the iron phosphate is directly prepared, and the prepared iron phosphate can be used as a precursor and can be used for preparing the lithium iron phosphate / carbon composite material with excellent performance. In the whole process, the acid-base adjusting process and the surfactant using process of a traditional iron phosphate production process are avoided. The iron phosphate prepared by the method has the advantages of special morphology, few types of byproducts (only phosphoric acid is left), small specific surface area, facilitation of washing, reduction of the use amount of washing water, facilitation of improvement of the recycling rate of mother liquor, avoiding of the introduction of sulfate ions and some cations, and further reduction of the pollution to the environment.

Description

technical field [0001] The invention belongs to the technical field of positive electrode materials for lithium ion batteries, and in particular relates to a preparation method of an iron phosphate intermediate with low cost, high performance, low surface area and quasi-polyhedral shape. Background technique [0002] With the gradual increase in the requirements of battery energy density, ternary cathode materials have attracted more and more attention. However, their high price and low thermal stability make the market slowly turn to low price, stable structure, safe performance and cycle. Lithium iron phosphate cathode material with good performance. [0003] Among various methods for preparing lithium iron phosphate, the production process using iron phosphate as a precursor has the advantages of simple production process and low production cost compared with the ferrous oxalate and iron red processes. With high capacity, high purity and high compaction, it has become th...

AI Technical Summary

Problems solved by technology

However, because the cost of ferric salt is too high to meet the current low-cost iron phosphate market requirements, this route has been gradually abandoned by manufacturers; the second method is to use ferrous sulfate (ferrous sulfate can be dissolved by sulfuric acid) One or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, phosphoric acid or sodium dihydrogen phosphate is used as a phosphorus source, and ferric phosphate is prepared by adding hydrogen peroxide to oxidize, which is currently the mainstream of iron phosphate manufacturers However, the process inevitably has by-product ammonium salt (ammonium sulfate), and a large amount of sulfate radicals are easily adsorbed on the surface of iron phosphate, which is not easy to wash. In order to reduce the sulfur content in iron phosphate, a large amount of water is often used in the washing process. , the cost of environmental protection treatment is high, and the existence of too high sulfur will affect the performance of lithium iron phosphate to a certain extent, and at the same time, sulfur dioxide gas is released during the preparation of lithium iron phosphate, causing environmental pollution

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