Understanding mechanisms of fast sodium storage kinetics for MXene/MoS2@C in ether electrolytes

Molybdenum disulfide (MoS 2 ) holds great potential for sodium storage due to its abundant active sites, large interlayer spacing, and high theoretical capacity (670 mAh g −1 ). However, realizing this theoretical capacity is challenging due to its low conductivity, sluggish electrochemical kinetics, and limited structural stability. In this work, we developed MoS 2 nanosheets on a Ti 3 C 2 Tx MXene multilayered framework, which are fully wrapped by conductive carbon (MXene/MoS 2 @C, referred to as TMC). The hybrid TMC anode exhibited higher Coulombic efficiency and reversible capacity in ether electrolytes compared to ester electrolytes, due to more efficient electrode-electrolyte interactions. During the charge and discharge process, sodium ions are intercalated into the lattice structure of the composite material and extracted during deintercalation, thereby achieving reversible sodium ion storage. Additionally, a thin solid electrolyte interphase (SEI) film was observed, which results from different structural evolution provides sufficient space for Na + ions, as revealed by depth-profiling X-ray photoelectron spectroscopy. Moreover, the fast diffusion kinetics of solvated Na + ions in ether electrolytes was confirmed using galvanostatic intermittent titration technique. As a result, TMC demonstrates high-performance sodium storage, including excellent cycling stability with 436mAh g −1 after 3000 cycles at 5 A g −1 , and a favorable rate capability (∼240 mAh g −1 at 10 A g −1 ). In a full cell, an impressive specific capacity of 230 mAh g −1 is achieved, with stable capacity retention at 1 A g −1 . • A dual-skeleton MXene-carbon network enhances ion transport. • Ether electrolytes boost interface compatibility and electrochemical performance. • High rate capability (∼240 mAh g −1 at 10 A g −1 ) with excellent cycling stability.