Elucidating the Potassiation Mechanism in SnS2 from a First-Principles Perspective

As a typical transition-metal dichalcogenide (TMD), SnS2 has received significant interest as an anode material for potassium-ion batteries (KIBs) due to its high safety and environmental friendliness. However, according to previous experimental results, the amount of K ions that can be reversibly inserted/extracted per SnS2 is limited, and detailed information about the reaction mechanisms during subsequent conversion and alloying processes is still poorly investigated. In this work, we performed first-principles calculations by density functional theory (DFT) to elucidate the potassiation reaction pathways of SnS(2 )as well as phase transformation caused by conversion and alloying. A variety of KxSnS2 (0 = x = 5) with nonequilibrium structural configurations as the anode material are systematically examined to understand the diffusion energetics, charge transfer, and lattice evolution. It is found that reversible intercalation occurs for KxSnS2 (0 = x = 1), which transforms to SnS, Sn, K2S, and KSn intermediate phases after the intercalation of K ions in tetrahedral interstitial sites. Based on these findings, the potassiation voltage profile of SnS2 is predicted to have a high theoretical capacity of 750 mAh g(-1). Our work opens a new avenue for understanding the architectural evolution and potassium storage chemistry for TMDs and provides important guidance for the design of energy-dense two-dimensional anodes in KIBs.