Vacancy-Assisted Transformation of MoS₂ Nanosheets into Defective MoS_x Nanoclusters to Regulate Sodium-Ion Electrode Functionality

Defect structure has attracted significant attention because of its importance as design factor for exploring high-performance functional materials. This study reports a defect-engineering strategy to optimize the electrode performance of transition metal dichalcogenides and a clear elucidation of the underlying mechanism on the benefit of defect engineering with cycling-induced transformation into small nanoclusters. The intercalative hybridization of monolayered MoS₂ nanosheets with bulky tetraalkylammonium cations is effective for generating abundant crystal vacancies in the MoS₂ lattice and improving the sodium-ion electrode performance, achieving one of the excellent performances among MoS₂-based sodium-ion anode materials. The improved electrode activity of the tetrapropylammonium−MoS₂ nanohybrid is ascribed to the vacancy-assisted transformation from monolayered MoS₂ nanosheets into trimeric/dimeric MoS_x nanoclusters during electrochemical cycling. ²³Na/¹H magic angle spinning-nuclear magnetic resonance analyses demonstrated that cycling-induced defective MoS_x nanoclusters yields a complex Na environment with high ion mobility and enhanced electrolyte absorptivity, promoting the excellent electrode functionality of tetrapropylammonium-assembled MoS₂ nanosheets.