Highly reversible lithium storage in Li2C2 nanosheets

Abstract

Using Li-carbon composites as anodes in high-energy-density lithium batteries leads to significant improvements in cycling life and safety compared with lithium metal. Li2C2 consisting of dumbbell anions is the most thermodynamically stable phase in the family of lithium-carbon materials, however its low conductivity is a critical obstacle to the practical applications. sp2-hybridizing carbon is one promising option for unique electronic structures. Here, Li2C2 alloy nanosheets composed of sp2-hybridized carbon atoms are directly formed from Li element and carbon during ball milling process, presenting a metallic feature at ambient conditions. After removing lithium from these alloy nanosheets, amorphous carbon ultrathin nanosheets are obtained. A vertically aligned Li2C2 nanosheet foil prepared by pressing the milled powder, can be used as free-standing, binder-free electrodes for fabricating various types of lithium batteries, and their excellent electrochemical performance is attributed to a highly reversible Li atoms uptake in amorphous carbon nanosheets.