Exfoliability of two-dimensional silicon nanosheets from calcium disilicide and its enhanced performance as lithium-ion battery anode material

Abstract

Two-dimensional silicon nanosheets are a promising pathway for achieving stable silicon anode materials due to their large specific surface area, lower diffusion energy barrier, and controlled volume change. The soft chemical topochemical reaction of calcium disilicide is a top-down approach for synthesizing silicon nanosheets of interest due to its potential for large-scale applications. However, the as-reacted material is composed of multilayer silicon nanosheets still held together by interlayer Van der Waal forces which limit its performance and cycling stability as LIB anode material. The current work investigates the exfoliation of soft topochemical-synthesized 2D silicon nanosheets, and a strategy for controlling nanosheet morphology, exfoliability, yields, and LIB performance is outlined herein. The soft topochemical reaction for the top-down synthesis of silicon nanosheets in anhydrous ethanol demonstrates improved exfoliability and initial specific capacities of up to 2390 mAh/g and retentions up to 96.6 % (200 cycles). The exfoliation mechanism and yields were discussed concerning the underlying solute-solvent interactions and sonication hydrodynamic cavitation. Exfoliation yields of up to 10 % are achieved, which is higher than any other reported in the literature for soft chemical synthesis, thus demonstrating the process' potential for large-scale applications.