Pre-Intercalation of TMA Cations in MoS₂ Interlayers for Fast and Stable Zinc Ion Storage

Applications of aqueous zinc ion batteries (ZIBs) for grid-scale energy storage are hindered by the lacking of stable cathodes with large capacity and fast redox kinetics. Herein, the intercalation of tetramethylammonium (TMA⁺) cations is reported into MoS₂ interlayers to expand its spacing from 0.63 to 1.06 nm. The pre-intercalation of TMA⁺ induces phase transition of MoS₂ from 2H to 1T phase, contributing to an enhanced conductivity and better wettability. Besides, The calculation from density functional theory indicates that those TMA⁺ can effectively shield the interactions between Zn²⁺ and MoS₂ layers. Consequently, two orders magnitude high Zn²⁺ ions diffusion coefficient and 11 times enhancement in specific capacity (212.4 vs 18.9 mAh g^‒1 at 0.1 A g^‒1) are achieved. The electrochemical investigations reveal both Zn²⁺ and H⁺ can be reversibly co-inserted into the MoS₂-TMA electrode. Moreover, the steady habitat of TMA⁺ between MoS₂ interlayers affords the MoS₂-TMA with remarkable cycling stability (90.1% capacity retention after 2000 cycles at 5.0 A g^‒1). These performances are superior to most of the recent zinc ion batteries assembled with MoS₂ or VS₂-based cathodes. This work offers a new avenue to tuning the structure of MoS₂ for aqueous ZIBs.