Clean and efficient synthesis of LiFePO4 cathode material using titanium white waste and calcium dihydrogen phosphate

Abstract

Large amounts of titanium white waste are generated in the production of titanium dioxide using sulphate method, which in turn can be used to prepare LiFePO₄ cathode material, thereby reducing environmental risks and achieving resource recovery. However, a key challenge lies in the elimination of impurities. In this work, a cost-efficient and straightforward approach based on phase transformation during hydrothermal treatment was proposed to utilize titanium white waste with calcium dihydrogen phosphate for the preparation of LiFePO₄ cathode material. The content of Fe in the leachate was enriched to 81.5 g/L after purification, while 99.9 % of Ti and 98.36 % of Al and were successfully removed. In the subsequent process for Fe/P mother liquor preparation, the losses of Fe and P were only 5.82 % and 2.81 %, respectively. The Fe and P contents of the synthesized FePO₄ product were 29.47 % and 17.08 %, respectively, and the Fe/P molar ratio was 0.986. Crystal phase of the product matched well with standard iron phosphate, and the lamellar microstructure of FePO₄ was uniform with the particle size ranging from 3 to 5 μm. Moreover, the contents of impurities in the product were far below the standard. The initial discharge of LiFePO₄ synthesized by the iron phosphate was 160.6 mAh^.g^-1 at 0.1C and maintained good reversible capacity after 100 cycles. This work may provide new strategy for preparing LiFePO₄ cathode material from industrial solid waste.

Keywords: Iron phosphate; Phase transformation; Resource recycling; Titanium white waste.