Regenerating the used LiFePO4 to high performance cathode via mechanochemical activation assisted V5+ doping

The wide usage of LiFePO 4 batteries makes their recovery and recycling urgent. Here, a novel, efficient and environmentally friendly recycling process has been developed to recover high performance LiFePO 4 nano composites from spent LiFePO 4 materials. The process comprises an intensive mechanochemical activation through mixing with precursor mixture and one-step solid state heat treatment. Spent LiFePO 4 , V 2 O 5 , Li 2 CO 3 , and NH 4 H 2 PO 4 are mixed according to the molar ratio of 1-xLiFePO 4 @xLi 3 V 2 (PO 4 ) 3 (x = 0, 0.005, 0.01, 0.03 and 0.1). In the typical process, the decomposition of self-contained binder and the conductive carbon provide a reducing environment as well as an in-situ coating carbon source. The SEM, XRD and XPS results illustrate that V 5+ is doped in the Fe 2+ site when x < 0.01, with co-existence of V 5+ doping and Li 3 V 2 (PO 4 ) 3 when x ≥ 0.03. Sole V 5+ doping assisted in-situ carbon coating displays the best electrochemical performance. The optimized sample shows discharge capacities of 154.3 mA h g −1 and 142.6 mA h g −1 at 0.1 and 1 C rates, respectively, with a high capacity retention of nearly ∼100% after 100 cycles. All results indicate that intensive mechanochemical activation assisted V 5+ doping is a promising strategy for spent LiFePO 4 recycling.