Self-assembled sandwich hollow porous carbon sphere @ MXene composites as superior LiS battery cathode hosts

Inhibiting the polysulfide shuttle while maintaining high sulfur loading of sulfur cathode has been regarded as the major barriers to the practical applications of lithium-sulfur (Li–S) batteries. To address these issues, a sandwich composite of hollow porous carbon spheres (HPCSs) and conductive delaminated-MXene nanosheets (d-Ti₃C₂) is designed by an electrostatic self-assembly approach as the sulfur hosts (denoted as HPCSs@d-Ti₃C₂). The hollow and porous merits of HPCSs can provide sufficient space for sulfur loading, while the conductive and polar MXene can chemisorb or bond polysulfides to inhibit the shuttle effect. Optimized packing of zero-dimensional (0D) HPCSs on 2D MXene nanosheets can not only accommodate volume expansion during polysulfide adsorption and conversion, but also prevent the aggregation of HPCSs to extend the lifetime of Li-S batteries. Consequently, the HPCSs@d-Ti₃C₂/S cathode with a high sulfur content of 76.5% has a strong physical and chemical co-adsorbing and/or chemical bonding with polysulfides to suppress the shuttle effect, and thus delivers satisfied sulfur utilization, rate capacities and cycling stability (only a capacity decay ratio of 0.069% per cycle on average). Such proposed design based on synergistic effects via nanoengineering is expected to be applicable to a large amount of MXene derived materials for various energy storage devices. (paper)