The pursuit of efficient cathode catalysts to improve cycle stability at ultra-high rates plays an important role in boosting the practical utilization of Li-O2 batteries. Featured as industrial solid waste, coal gangue with rich electrochemical active components could be a promising candidate for electrocatalysts. Here, a coal gangue/Ti3C2 MXene hybrid with a TiO2/SiCx active layer is synthesized and applied as a cathode catalyst in Li-O2 batteries. The coal gangue/Ti3C2 MXene hybrid has a tailored amorphous/crystalline heterostructure, enhanced active TiO2 termination, and a stable SiCx protective layer; thereby, it achieved an excellent rate stability. The Li-O2 battery, assembled with a coal gangue/Ti3C2 MXene cathode catalyst, was found to obtain a competitive full discharge capacity of 3959 mAh g-1 and a considerable long-term endurance of 180 h (up to 175 cycles), with a stable voltage polarization of 1.72 V at 2500 mA g-1. Comprehensive characterization measurements (SEM, TEM, XPS, etc.) were applied; an in-depth analysis was conducted to reveal the critical role of TiO2/SiCX active units in regulating the micro-chemical constitution and the enhanced synergistic effect between coal gangue and Ti3C2 MXene. This work could provide considerable insights into the rational design of catalysts derived from solid waste gangue for high-rate Li-O2 batteries.
Keywords: Li-O2 battery; TiO2 catalytic units; amorphous/crystalline heterostructure; bifunctional electrocatalysts; mining solid waste.