Unveiling the autocatalytic growth of Li2S crystals at the solid-liquid interface in lithium-sulfur batteries

Abstract

Electrocatalysts are extensively employed to suppress the shuttling effect in lithium-sulfur (Li-S) batteries. However, it remains challenging to probe the sulfur redox reactions and mechanism at the electrocatalyst/LiPS interface after the active sites are covered by the solid discharge products Li₂S/Li₂S₂. Here, we demonstrate the intrinsic autocatalytic activity of the Li₂S (100) plane towards lithium polysulfides on single-atom nickel (SANi) electrocatalysts. Guided by theoretical models and experimental data, it is concluded that LiPS dissociates into Li₂S₂ and short-chain LiPS on the Li₂S (100) plane. Subsequently, Li₂S₂ undergoes further lithiation to Li₂S on the Li₂S (100) surface, generating a new Li₂S (100) layer, thus enabling the autocatalytic formation of a new Li₂S (100) surface. Benefiting from the autocatalytic growth of Li₂S, the concentration of LiPS in the electrolyte remains at a lower level, enabling Li-S batteries under high loading and low electrolyte conditions to exhibit superior electrochemical performance.