Cationic two-dimensional sheets for an ultralight electrostatic polysulfide trap toward high-performance lithium-sulfur batteries

Lithium-sulfur batteries have many advantages, including their low material cost, high safety, and high energy density, and thus, they have recently been pursued as the most promising alternative to lithium-ion batteries in a multitude of applications, ranging from electric vehicles to stationary grid storage. However, these batteries are greatly hindered by certain problems, especially their low utilization of sulfur and fast capacity depletion due to the dissolution of the intermediate discharge product, polysulfide, and its diffusion across the separator to the anode side. In this study, we report the utilization of inorganic cationic sheets as a conformal modification layer on the separator, synergistically working as both a physical confinement barrier and chemical trap that efficiently blocked the crossover of polysulfide and accordingly improved the cycling life of Li-S batteries. Notably, due to the high percentage of surface atoms and the synergy of the physical and chemical trapping functions, the modification loading was minimized to a record low level (a density of ~0.018 mg cm−2 and a thickness of 20-30 nm), promising the unsacrificement of energy density when considering the entire cell. This proof-of-concept work of utilizing inorganic cationic sheets as a modification layer on a commercial separator provides a cheap and simple but effective strategy to enhance the cycle life of Li-S batteries.