Development of high-energy non-aqueous lithium-sulfur batteries via redox-active interlayer strategy

Abstract

Lithium-sulfur batteries have theoretical specific energy higher than state-of-the-art lithium-ion batteries. However, from a practical perspective, these batteries exhibit poor cycle life and low energy content owing to the polysulfides shuttling during cycling. To tackle these issues, researchers proposed the use of redox-inactive protective layers between the sulfur-containing cathode and lithium metal anode. However, these interlayers provide additional weight to the cell, thus, decreasing the practical specific energy. Here, we report the development and testing of redox-active interlayers consisting of sulfur-impregnated polar ordered mesoporous silica. Differently from redox-inactive interlayers, these redox-active interlayers enable the electrochemical reactivation of the soluble polysulfides, protect the lithium metal electrode from detrimental reactions via silica-polysulfide polar-polar interactions and increase the cell capacity. Indeed, when tested in a non-aqueous Li-S coin cell configuration, the use of the interlayer enables an initial discharge capacity of about 8.5 mAh cm⁻² (for a total sulfur mass loading of 10 mg cm⁻²) and a discharge capacity retention of about 64 % after 700 cycles at 335 mA g⁻¹ and 25 °C.

Lithium-sulfur batteries promise high energy density, but polysulfide shuttling acts as a major stumbling block toward practical development. Here, a redox-active interlayer is proposed to confine polysulfides, increase the cell capacity and improve cell cycle life.