Coated layer with Cu-P electrocatalyst to enhance lithium polysulfides redox reaction for high energy Li-S batteries.

Abstract

Lithium-sulfur (Li-S) batteries have garnered significant attention for use in electric vehicles due to their high theoretical capacity (1,672mAh g-1) and energy density (2,600Wh kg-1). However, despite their great potential, Li-S batteries still face challenges related to unstable long-term cycle performance and inadequate practical energy densities. The primary cause of capacity degradation in Li-S batteries is attributed to the 'lithium polysulfides (LiPS, Li₂Sₓ, 3 ≤x ≤ 8) shuttle phenomenon.' During the cycling process, LiPS is generated through redox reactions and can migrate through the separator, leading to active material loss and side reactions in the electrolyte. Therefore, it is crucial to design a coated separator with two key attributes: high adsorption capability for dissolved LiPS and fast electrochemical redox kinetics. In this study, we have designed a coated separator incorporating a Cu-P compound to mitigate LiPS dissolution and enhance its redox reactions. Our results reveal the adsorption mechanism, in which ST-1 of LiPS can be effectively adsorbed onto the surface of copper and oxidized phosphorus. Furthermore, we have confirmed that the introduction of our coated separator with the Cu-P electrocatalyst effectively suppresses the shuttle phenomenon and improves the electrochemical performance of Li-S batteries.