Lithium-metal anode interfaces in Li-S batteries: From failure mechanisms to practical stabilization

Lithium-sulfur (Li-S) batteries are among the most promising post-lithium-ion energy storage technologies because of their extremely high theoretical specific capacity (1675 mAh g −1 ) and gravimetric energy density of 2567 Wh kg −1 . However, the use of lithium metal anodes in a high-concentration polysulfide environment is a primary limitation to the practical deployment of Li-S batteries. This is exacerbated by commercially relevant conditions of lean electrolyte operation, high sulfur loading (6-10 mg cm −2 ), and limited lithium supply. In this review, we present a holistic picture of the underlying failure processes in lithium metal degradation in the Li-S battery, focusing on lithium plating/stripping processes, SEI formation mechanisms, ion-transport heterogeneity, and chemo-mechanical instabilities. The latest developments on lithium-anode stabilization by three-dimensional current collectors and host architecture, artificial interphases, lithiophilic surface engineering, solid-state and gel-polymer electrolyte are critically evaluated. Importantly, this review emphasises the interplay between interface chemistry, transport kinetics, and structural evolution and their effect on long-term anode stability and cell performance. This review links fundamental mechanistic insights with practical engineering solutions and highlights major challenges and new opportunities for stable lithium-metal anodes under operating conditions. The perspectives discussed herein set the groundwork for designing commercially viable, high-energy-density Li-S batteries.