A green recycling process designed for LiFePO4 cathode materials for Li-ion batteries

Abstract

A green process route to recycle LiFePO4/C electrode materials is proposed in this work. First, a robust strategy to synthesize LiFePO4/C cathode materials from a precursor of a crystalline FePO4$2H2O phase (metastrengite I) is presented. In order to prepare crystalline FePO4$2H2O, a solution precipitation route is adapted, where the reaction conditions such as temperature and pH are precisely controlled. Among various heat treatment temperatures to calcine our prepared FePO4$2H2O with lithium sources, we find that LiFePO4/C cathode materials synthesized at 700 C deliver a maximum discharge capacity of 168.51 mA h g 1 at 0.1 C (1 C rate ¼ 170 mA h g 1) with a capacity retention of 99.36% after the 25th cycle at 1 C. Furthermore, commercially available LiFePO4 powders and recovered LiFePO4 electrode materials from spent batteries are both tested with our developed recycling process, where we decompose LiFePO4 powders/electrodes to prepare crystalline FePO4$2H2O, and then re-synthesize LiFePO4/C cathode materials. In both cases, our recycled LiFePO4/C exhibits a very comparable discharge capacity of 140 mA h g 1 at 1 C with a capacity retention of 99%.