Al2O3-induced phase conversion regulation from hexagonal FeS to orthorhombic FeS for enhancing the Li-ion accommodation ability

Abstract

Cycling lifespan/stability is one of the most important limitations for multivalent transition metal sulfides (TMSs) used in secondary batteries. However, the chaos reaction of TMSs is an important obstacle that restricts their electrochemical stability in all-enclosed batteries. Herein, taking FeS anode and lithium-ion batteries as the example, the phase-lithiation correlation is studied through TEM and DFT analysis. It's found that the pristine hexagonal FeS converts to tetragonal FeS phase accompanied by severe and rapid capacity decay. However, it converts to orthorhombic FeS with enhanced capacity and nice lifespan when introducing trace amount amorphous Al2O3 upon FeS power's surface. DFT calculations further reveal that Al2O3 induces the phase conversion from low-acitve tetragonal FeS to high-active orthorhombic FeS, which promotes the lithiation-delithiation reversibility and stability. Based on the above result, it is expected to provide useful guidelines for the in-situ structure engineering of TMSs-based anodes in all-enclosed secondary batteries.