High-performance Sn2S3 as a conversion-alloying anode material for lithium-ion batteries: insights from first-principles calculations

Conversion-alloying based anode materials represent a promising frontier in the evolution of lithium-ion batteries (LIBs), offering high capacities and improved structural integrity. However, these anodes often suffer from large volume changes and low reversible capacity. To address these issues, Sn2S3, a tin-based conversion-alloy anode material, was studied using first-principles calculations. The lithiation behavior of bulk Sn2S3 was predicted and analyzed at various stages. In the fully lithiated state, the Sn2S3 anode expands by just 158%, significantly lower than other tin-based anodes and exhibits an open circuit voltage close to zero (similar to 0.2 V). It also demonstrated a high theoretical capacity of 1189 mA h g-1, with a reversible capacity of 707 mA h g-1. The diffusion of lithium in Sn2S3 showed an ultra-low barrier of 0.075 eV, one of the lowest reported among bulk and 2D anode materials. A composite of Sn2S3 with carbon could further enhance its electrochemical properties by increasing capacity and electrical conductivity and alleviating strain from volume changes. Our calculations predict Sn2S3 as a high-performance conversion-alloying anode material candidate for LIBs.