Electrocatalytic and stoichiometric reactivity of 2D layered siloxene for high-energy-dense lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) have emerged as promising power sources for high-performance devices such as electric vehicles. However, the poor energy density of LSBs owing to polysulfide shuttling and passivation has limited their further market penetration. To mitigate this challenge, two-dimensional (2D) siloxene (2DSi), a Si-based analog of graphene, is utilized as an additive for sulfur cathodes. The 2DSi is fabricated on a large scale by simple solvent extraction of calcium disilicide to form a thin-layered structure of Si planes functionalized with vertically aligned hydroxyl groups in the 2DSi. The stoichiometric reaction of 2DSi with polysulfides generates a thiosulfate redox mediator, secures the intercalation pathway, and reveals Lewis acidic sites within the siloxene galleries. The 2DSi utilizes the corresponding in-situ-formed electrocatalyst, the 2D confinement effect of the layered structure, and the surface affinity based on Lewis acid-base interaction to improve the energy density of 2DSi-based LSB cells. Combined with the commercial carbon-based current collector, 2DSi-based LSB cells achieve a volumetric energy density of 612 Wh L-cell(-1) at 1 mA cm(-2) with minor degradation of 0.17% per cycle, which rivals those of state-of-the-art LSBs. This study presents a method for the industrial production of high-energy-dense LSBs.