Unleash sodium storage potential of MoS₂ nanosheets: Generating favorable kinetics from optimal crystallinity and elaborate structure

Metal oxides with high crystallinities have been reported to exhibit better ion storage performances, which demonstrates the significance of controlling the crystallinity as a facile and economical method to synthesize high-performance electrode materials. However, the relationship between crystallinity and charge storage property remains unclear for transition metal disulfides (TMDs). In this work, we employ a series of MoS₂-based electrode materials with different crystallinities as a case to study the trend in sodium ion (Na⁺) storage characteristics of TMDs with varying crystallinity. Structure characterizations prove that the crystallinity of MoS₂ improves with the increase in calcination temperature. Electrochemical tests and kinetic analyses indicate that MoS₂-based electrode material with higher crystallinity shows better high-rate Na⁺ storage performance and stronger pseudocapacitive response. Finally, we carry out density functional theory calculations to study Na⁺ diffusion behaviors in MoS₂ with different crystallinities, and we prove that MoS₂ with higher crystallinity possesses better Na⁺ diffusion kinetics. The conclusions of this work provide beneficial guidance for the rational design of TMDs toward superior high-rate ion storage.