Direct recovery of degraded LiFePO4 cathode via mild chemical relithiation strategy

Abstract

With the rapid popularization of LiFePO4 (LFP) based lithium-ion batteries, the rational recycle of spent LFP has become focus in recent years. Direct regeneration of spent LFP has received continuous attention as it can effectively eliminate the capacity attenuation caused by lithium loss and Fe (Ⅲ) phase and maintain the original LFP structure. Here, we propose an efficient approach on basis of mild chemical relithiation combining with appropriate thermal annealing to realize the direct regeneration of spent LFP without high temperature/pressure or extra hazardous chemical. Specifically, subtle reductive hydrogen peroxide in LiOH solution is utilized to remove the structural defects of a degraded LFP cathode, and the restored LFP shows excellent cycling stability and rate capability (a capacity retention of 84.9% after 1000 cycles at 5C). Moderate regeneration conditions guarantee high security and profit of this strategy compared with other regeneration technologies, which reveals a favourable potential of practical application and is expected to the sustainable development of spent lithium-ion batteries.