A bifunctional heterostructure promoting the kinetics and stability of sulfur cathodes in advanced aluminum–sulfur batteries†

The aluminum–sulfur battery is an ideal energy storage device with the merits of low cost, safety, and high energy density. However, due to the poor conductivity of sulfur and its soluble discharge products, the kinetics of sulfur and polysulfide redox reactions are very slow. Herein, a porous flaky Ti₃C₂T_x-Co host material is designed, which can form a Ti₃C₂T_x-CoS_x heterostructure in situ with sulfur. The unique heterostructure provides many catalytic anchoring sites and active sites for enhancing the adsorption and conversion of sulfur and polysulfides. Compared with pure Ti₃C₂T_x, Ti₃C₂T_x-CoS_x greatly reduces the decomposition energy barrier of discharge products and accelerates the redox kinetics of sulfur species. The Ti₃C₂T_x-CoS_x@S cathode realizes fast charging at 1 A g⁻¹ and achieves a long cycle life of 1000 cycles with discharge capacities in the range of 215–358 mA h g⁻¹. Even at 1.5 A g⁻¹, the cathode can still achieve a capacity greater than 190 mA h g⁻¹ for over 1500 cycles. Using Ti₃C₂T_x-Co as the host of sulfur, a reversible redox reaction among S, S⁻ and S²⁻ occurred during the charge–discharge process, indicating its potential for use in high-performance Al–S batteries.