Highly reversible lithium storage in Li2C2 nanosheets

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. Li 2 C 2 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. sp 2 -hybridizing carbon is one promising option for unique electronic structures. Here, Li 2 C 2 alloy nanosheets composed of sp 2 -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 Li 2 C 2 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.