Recycling spent LiNi _1-x-yMn _xCo _yO ₂ cathodes to bifunctional NiMnCo catalysts for zinc-air batteries

Significance

In recent years, lithium-ion batteries (LIBs) have been widely applied in electric vehicles as energy storage devices. However, it is a great challenge to deal with the large number of spent LIBs. In this work, we employ a rapid thermal radiation method to convert the spent LIBs into highly efficient bifunctional NiMnCo-activated carbon (NiMnCo-AC) catalysts for zinc-air batteries (ZABs). The obtained NiMnCo-AC catalyst shows excellent electrochemical performance in ZABs due to the unique core-shell structure, with face-centered cubic Ni in the core and spinel NiMnCoO ₄ in the shell. This work provides an economical and environment-friendly approach to recycling the spent LIBs and converting them into novel energy storage devices.

Abstract

The skyrocketing production of lithium-ion batteries (LIBs) for electric vehicles portends that tremendous numbers of used LIBs will be generated. However, the recycling of used LIBs is limited by the complicated separation processes of traditional pyrometallurgy and hydrometallurgy methods. Here, we applied a rapid thermal radiation method to convert spent LiNi _1-x-yMn _xCo _yO ₂ (NMC) cathodes from used LIBs into highly efficient NiMnCo-based catalysts for zinc-air batteries (ZABs) through acid leaching and radiative heating processes, which avoids sophisticated separation of different metals and can synthesize the catalysts rapidly. The prepared NiMnCo-activated carbon (NiMnCo-AC) catalyst presents a unique core-shell structure, with face-centered cubic Ni in the core and spinel NiMnCoO ₄ in the shell, which redistributes the electronic structure of the NiMnCoO ₄ shell to decrease the energy barrier for oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) processes and ensures high electrocatalytic activities. The NiMnCo-AC catalyst in ZABs as cathode materials exhibits a high power density of 187.7 mW cm ⁻², low voltage gap of 0.72 V at the initial three cycles, and long cycling duration of 200 h at the current density of 10 mA cm ⁻². This work provides a promising strategy to recycle spent LIBs to highly efficient catalysts for ZABs.