Molecular Connectors Boosting the Performance of MoS Cathodes in Zinc-Ion Batteries.

Zinc-ion batteries (ZIBs) are promising energy storage systems due to high energy density, low-cost, and abundant availability of zinc as a raw material. However, the greatest challenge in ZIBs research is lack of suitable cathode materials that can reversibly intercalate Zn ions. 2D layered materials, especially MoS-based, attract tremendous interest due to large surface area and ability to intercalate/deintercalate ions. Unfortunately, pristine MoS obtained by traditional protocols such as chemical exfoliation or hydrothermal/solvothermal methods exhibits limited electronic conductivity and poor chemical stability upon charge/discharge cycling. Here, a novel molecular strategy to boost the electrochemical performance of MoS cathode materials for aqueous ZIBs is reported. The use of dithiolated conjugated molecular pillars, that is, 4,4'-biphenyldithiols, enables to heal defects and crosslink the MoS nanosheets, yielding covalently bridged networks (MoS-SH2) with improved ionic and electronic conductivity and electrochemical performance. In particular, MoS-SH2 electrodes display high specific capacity of 271.3 mAh g at 0.1 A g, high energy density of 279 Wh kg, and high power density of 12.3 kW kg. With its outstanding rate capability (capacity of 148.1 mAh g at 10 A g) and stability (capacity of 179 mAh g after 1000 cycles), MoS-SH2 electrodes outperform other MoS-based electrodes in ZIBs.