Conversion of LiFePO4 to FePO4 via Selective Lithium Bicarbonation: A Direct Pathway Towards Battery Recycling

Abstract

Recycling of spent LiFePO4 batteries represents a challenge due to their relatively low economic value. This paper proposes a novel direct recycling route that extracts selectively lithium while keeping the delithiated solid product electrochemically active. The innovative use of CO2, as a mild solubilization agent for lithium, in conjunction with an oxidizing agent such as H2O2 allows to selectively extract from 85% to 95% of the lithium content from pristine active material at room temperature and 2 atm CO2 partial pressure, while keeping intact the orthorhombic heterosite structure of the delithiated iron phosphate (FePO4). Extensive characterization studies revealed the FePO4 product to remain highly pure with its carbon coating electronically active. In fact, the delithiated product showed similar electrochemical performance as the pristine material with an initial capacity at around 154 mAh.g−1 for a 12 h discharge rate (C/12) and a capacity retention of 98% after 100 cycles. When applied to spent LiFePO4 batteries, the new direct process provided high de-lithiation efficiency exceeding 90% lithium extraction despite somewhat slower kinetics.