A Hybrid Intercalation and Conversion Mechanism for Reversible Lithium Storage in Layered Silicane (SiH) with Low Molar Volume Change

Conversion-type anode materials generally suffer from significant volume change upon lithiation despite a high energy storage capacity. Here we report a new intercalation and conversion hybrid-type lithiation mechanism that enables a layered silicane (L-SiH) material to balance high capacity with low volume change. Using first-principles simulations of lithiation and delithiation processes, we predict L-SiH only shows a 3.8 cm3/mol volume expansion upon lithiation, significantly lower than that of crystalline Si (∼9.2 cm3/mol). During lithium intercalation, hydrogen in L-SiH is redox active, and LiH bonds are formed in the interlayer, without destruction of Si planes. The predicted lithiation proceeds via a two-phase coexisting process at an open-circuit voltage (OCV) plateau of ∼0.43 V, which coincides with experimental observation of a 0.4 V plateau upon the lithiation of synthesized L-SiH. This study introduces a promising anode material with a low volume change fulfilled by an intriguing mechanism.