Cobalt-doped MoS2·nH2O nanosheets induced heterogeneous phases as high-rate capability and long-term cyclability cathodes for wearable zinc-ion batteries

The abundant Zn resource and high safety water-based electrolytes promote fiber-shaped aqueous zinc-ion batteries (FAZIBs) to become promising energy-storage devices for powering portable and wearable electronics. However, the low capacity and poor cyclic stability arising from the intrinsic low conductivity and the strong electrostatic interaction between Zn2+ and the host structures remain a formidable challenge to develop freestanding MoS2-based cathodes for high-performance FAZIBs. Herein, an effective strategy of cobalt-doped MoS2·nH2O nanosheets directly grown on carbon nanotube fiber (CoxMo1-xS2·nH2O/CNTF) was proposed to achieve efficient cathodes for FAZIBs. The introduction of Co-ion activates the transformation of MoS2 from 2H-phase to 1T-phase and the invasion of crystal water further expands the interlayer spacing of MoS2 for well-designed CoxMo1-xS2·nH2O/CNTF, thus achieving a remarkable capacity of 305.4 mAh cm−3 at 0.1 A cm−3, high rate capability (154.4 mAh cm−3 at 4 A cm−3) and impressive durability (79.2% capacity retention after 1800 cycles). Density Functional Theory (DFT) shows that the increase of the conductivity of heterogeneous phases MoS2 and the expanded interlayers stemming from the crystal water contribute to the insertion and extraction of zinc ions. To highlight, quasi-solid-state FAZIBs adopting CoxMo1-xS2·nH2O/CNTF cathode displays great flexibility (79.3% capacity retention over 1000 bending cycles). This work will shed light on developing high-performance MoS2-based materials for wearable AZIBs.