Polar organic molecules assisting Mo-based cathode materials for enhanced zinc-ion transfer kinetics

The Mo-based oxides/sulfides are promising cathode materials for Zn-ion batteries (ZIBs). However, the volume expansion and poor intrinsic electronic conductivity limit their electrochemical performance. Herein, a strategy of introducing active organic small molecule (ethylenediamine) into the interlayer of the Mo-based oxides/sulfides (MoOS) is reported to solve these shortcomings. The experimental analysis reveals that ethylenediamine (EDA) can regulate the composition ratio of MoO3/MoS2 for its reduction ability, which can improve the electronic conductivity of the EDA-intercalated MoOS (MoOS-EDA). Besides, EDA can efficiently decrease the Zn2+ insertion energy for its strong coordinated ability with Zn2+, in combination with the enhanced interlayer spacing and the strong repulsion with Zn2+ from the non-polar group –CH2CH2 in EDA, leading to enhanced ionic transferring kinetics and Zn2+ storage ability. The theoretical and experimental analysis have confirmed the organic guest and inorganic skeleton all participate in the Zn2+ storage process. As a result, compared with the MoOS cathode, the MoOS-EDA exhibits improved specific capacity (203 vs. 88 mAh/g at 0.1 A/g) and prolonged cycle stability. Moreover, the soft-package cell based on MoOS-EDA cathode also delivers an impressive electrochemical performance. This work provides a strategy to improve the Zn2+ transfer kinetics in MoS2 cathode material towards high-performance ZIBs.