Surface engineering to upgrade spent LiCoO2 by removing Al impurity

Abstract

Developing rational regeneration protocol to upgrade spent cathode material for their usage in next generation lithium-ion batteries (LIBs) can alleviate resource stress and benefit environment and carbon neutrality. This work demonstrates that direct regeneration of spent LiCoO₂(LCO) encounters the negative effects of Al impurity, which is a common impurity in the spent LIB materials introduced during battery cycling and disassembly process. Our microanalysis show that Al impurity tends to segregate on the LCO surface during the direct regeneration process, which not only causes poor surface regeneration but also degenerates the surface modification effect for upgrading purpose. We therefore propose a one-pot protocol by using a bifunctional solution to realize Al impurity removal and Ti surface coating simultaneously, which successfully upgrade the spent LCO for high voltage and high-power usage. The upgraded LCO cathode can achieve 90 % and 97 % capacity retentions at 0.2C and 2C rates after 2.8–4.5 V 100 cycles, and their initial specific capacity is 180 mAh/g and 149 mAh/g, respectively. The microstructure characterizations in this work provide in-depth understanding of the direct regeneration process, which is essential for understanding and optimizing the recycling process. Further economic analysis show that the established regeneration protocol holds promise for realizing large-scale industrial recycling process of spent LCO.