The design of Co3S4@MXene heterostructure as sulfur host to promote the electrochemical kinetics for reversible magnesium-sulfur batteries

The rechargeable Mg-S batteries are attractive because of their resource abundances of Mg and S, high volumetric energy density, and less dendrite property of Mg anodes. However, the development is barred by the intrinsic low electronic conductivity of S and the discharge products as well as the lack of understanding the hidden electrochemical kinetics. Here, a Co3S4@MXene heterostructure is proposed as effective sulfur host for reversible Mg-S batteries. XPS results and density functional theory (DFT) calculation confirm that the chemical interaction between the decorated Co3S4 nanocrystals host and polysulfide intermediates could well absorb and catalyze the polysulfides conversion, thus improve the electrochemical redox kinetics. Meanwhile, the MXene matrix could promote Mg ion diffusion dynamics greatly. As a result, the developed Mg-S batteries using the Co3S4@MXene-S as the cathode material could demonstrate high sulfur utilization with specific capacity of 1220 mAh g−1 and retain a capacity of 528 mAh g−1 after 100 cycles, together with a satisfactory rate performance even at 2 C. This work shed light on the advanced cathode design for reversible high energy Mg-S batteries.