Additive-assisted complex-formation-regulated decalcification of calcium disilicide for enhanced exfoliation and stable bare silicon nanosheet anodes in lithium-ion batteries

Abstract

Thin, exfoliated silicon nanosheets represent a promising approach to enhance the structural and electrochemical stability of silicon anodes in lithium-ion batteries (LIBs). Reducing nanosheet thicknesses below critical fracture thresholds minimizes cycling-induced fractures, improving material stability and cycling performance. Our preliminary work shows that deliquescent moisture in the molten salt decalcification of calcium disilicide (CaSi₂) is crucial for effective exfoliation but also promotes unwanted silicon oxidation, prompting the search for alternatives. We report a thermodynamically optimized reaction route, regulated by complex formation, to enhance the molten salt decalcification and exfoliation of silicon nanosheets derived from the Zintl phase calcium disilicide. Structural analysis reveals increased specific surface area and robust interlayer separation, while electrochemical tests demonstrate significant gains in cycling performance, with a 51 % increase in reversible capacity retention and improved kinetics. This work highlights enhanced exfoliation and an optimized reaction technique as promising solutions to the limitations of bare silicon anodes, offering a scalable, high-performance pathway for lithium-ion battery technology.