Regeneration of spent cathodes of Li-ion batteries into multifunctional electrodes for overall water splitting and rechargeable Zn-air batteries by ultrafast carbothermal shock

Lithium-ion batteries (LIBs) are widely used in electric vehicles and consumer electronics and require reliable recycling strategies. In this paper, we investigated how an ultrafast carbothermal shock treatment can be used to convert spent cathodes of LIBs (LiNi0.8Mn0.1Co0.1O2) into Ni/Ni-Mn-Co-O (N/NMCO) composites with a remarkable electrocatalytic performance toward oxygen evolution, oxygen reduction, and hydrogen evolution reactions. The converted spent cathodes can be employed as cathodes and anodes in an overall water-splitting system, and they displayed a low overpotential of 1.61 V and remarkable stability at different current densities. Moreover, N/NMCO electrodes can be used as cathodes in rechargeable Zn-air batteries, which displayed long-term stability (>30 h), high specific capacity (781 mA h g−1) and peak power density (137 mW cm−2), as well as a small charge/discharge voltage gap of 0.71 V. Thus, our study offers a “waste-to-treasure” strategy for the regeneration of spent cathodes of LIBs and their applications in other advanced energy storage and conversion technologies.