In situ study on the charge/discharge of nanocrystalline Li2C2 as a new cathode material

Abstract

The real-time charge and discharge processes of a single phase nanocrystalline Li₂C₂ alloy were directly observed by in situ transmission electron microscopy. Upon lithiation, nanocrystalline Li₂C₂ exhibits obvious volume expansion and morphology change, and an amorphous structure is generated from the nanocrystalline matrix. The change of structure affects the cycling stability of nanocrystalline Li₂C₂ as a cathode material. To reduce the effect of the structural change, the degree of delithiation was optimized by controlling the charge/discharge voltage range in the electrochemical tests. A high initial specific capacity of 352 mA h g⁻¹ was obtained for nanocrystalline Li₂C₂, and a discharge capacity of 171 mA h g⁻¹ was maintained after 50 cycles. The present work proposed a new alloy-type cathode material of nanocrystalline Li₂C₂ for lithium ion batteries with promising electrochemical performance.