Uncovering the untapped potential of copper(I) sulphide toward lithium-ion storage under ultra-low temperatures

Recently, to enhance the low-temperature performance of lithium-ion batteries (LIBs), significant efforts have been devoted to developing novel electrolytes with low viscosities, high conductivities, and facile Li-ion desolvation, while much less attention is paid to exploring optimum electrode materials for low-temperature LIBs. In this contribution, we discover that commercial microsized Cu₂S exhibits a remarkably high performance toward lithium storage under ultra-low temperatures. Under room temperature, it delivers a reversible specific capacity of 318.8 mA h g⁻¹ with very flat lithiation-delithiation plateaus around 1.75 V in Li metal cells. At −60 °C and a galvanostatic charge-discharge rate of 0.3C, it could still provide a reversible specific capacity of 168.8 mA h g⁻¹ with stable cycling performance, promising its application in ultra-low-temperature Li-based batteries. Through a combination of microscopic, spectroscopic, and electrochemical characterization bolstered by theoretical calculations, the detailed reaction mechanisms and mechanistic understanding of the excellent low-temperature performances are proposed. This work points out the great opportunities to enhance the low-temperature performance of LIBs by discovering suitable electrode materials.