Regenerated spent LiFePO4 with tailored residual copper-atoms towards improved energy-storage capacity and reversibility

Abstract

Large-scale recycling spent LiFePO4 (LFP) has aroused the enthusiasm of widespread studies due to its significant economic/environmental values. Restricted by the accuracy of mechanical disassembling, Cu element would be inevitably introduced into the spent samples, resulting in the existence of impurities. Exploring precise thresholds of Cu-impurities was significant in commercial promotion of LiFePO4 regeneration processes. Theory calculation proved that Cu-doping was beneficial to accelerate the diffusion process of Li ions in LFP lattice. Inspired by the theory calculation, a generation process with tailored Cu-impurities content was designed in this work. Supported by the well-designed regeneration process, Cu ions can be rationally doped into the lattice of spent LFP, contributing to the attractive electrochemical properties. Utilized as the cathode of LIBs, the capacity of samples with optimized Cu-impurities content achieved about 130 mAh/g at 2.0C, accompanied by a capacity retention of 100 % among 300 cycles. Importantly, the in-depth mechanism between the reversibility and Cu-impurities threshold is investigated by in-suit XRD, especially the irreversible phase evolution of regenerated samples with excessive Cu-impurities introducing. Given this, this work revealed the in-depth mechanism between Cu-impurities threshold and electrochemical performance, while contribute to the large-scale regeneration of spent LFP.