For elements-utilization regeneration of spent LiFePO4: Designed basic precursors for advanced polycrystal electrode materials

Abstract

Spent lithium iron phosphate (LFP) is commonly recovered by hydrometallurgy to prepare Li₂CO₃ and FePO₄, but suffering from long process and low value-added products. Hydrothermal method avoids element separation and regenerates LFP materials directly from leaching solution of spent LFP. However, it requires three-time the theoretical amount of lithium. In this study, using LiFePO₄(OH) (LFPOH) as a medium, LFP materials were regenerated with theoretical amount of lithium in virtue of energetically favorable reaction of Li-ions into the internal structure. The formation mechanism of LFPOH and LFP materials were investigated, and advanced polycrystal LFP materials with fast ions-diffusion ability and high reversibility were obtained. The capacities of recovered LFP materials are 156.17 mAh g⁻¹, 148.51 mAh g⁻¹, 138.34 mAh g⁻¹, 124.1 mAh g⁻¹ at 0.2 C, 0.5 C, 1 C and 2 C, respectively and their capacity could be remained 139.92 mAh g⁻¹ at 1 C with retention of almost 100 % after 200 cycles. Moreover, with the assistance of economic analysis, the designed regenerated path displayed considerable recycling value-potential, especially the reducing of Li-resources (from three-time to one-time). This study sheds light on designing polycrystal recovered LFP with help of basic medium, whilst provides an effective strategy for preparing high-performance LFP materials.