Recycling application of waste Li–MnO2 batteries as efficient catalysts based on electrochemical lithiation to improve catalytic activity

Abstract

The ever-increasing consumption of tons of lithium batteries, for example, Li–MnO₂ batteries, has generated great concern regarding their recycling. Currently, the developed or proposed cathode recycling processes often suffer from complex recycling procedures, potential secondary pollution, high operating costs, or thermal reprocessing. The discharge of Li–MnO₂ batteries involves electrochemical lithiation, which is simultaneously accompanied by the transition from Mn(IV) to Mn(III). Studies on manganese-containing catalysts have experimentally and theoretically emphasized the role of Mn(III) as an important intermediate state for enabling catalytic reactions. We present herein a simple washing-recycling process for efficiently recycling the MnO₂-based cathode materials as catalysts from depleted lithium batteries. The multiple important properties of the lithiated MnO₂, including phase structure, oxidation state, surface oxygen species, and structural factors, were investigated in detail. Correspondingly, the effect of the degree of electrochemical lithiation on the catalytic activity of recycled MnO₂ was observed to be continuously tuned. Compared with pristine MnO₂, the recycled MnO₂ exhibited remarkably enhanced catalytic activity for activating PMS to decompose contaminants. The catalytic activity was correlated with the composition of Li_xMnO₂ generated in situ in Li–MnO₂ batteries owing to the tuning of the Mn valence and structural factors. This study provides an attractive method for converting the depleted electrode materials of lithium batteries into catalysts to enhance their recycling efficiency.