Sustaining vacancy catalysis via conformal graphene overlays boosts practical Li–S batteries

Abstract

Sluggish reaction kinetics and uncontrollable dendrite growth are deemed as the main bottlenecks for practical Li–S batteries. Notwithstanding fruitful advances in designing dual-functional mediators for both electrodes, cooperative efforts on protecting catalytically active sites and optimizing solid electrolyte interphase (SEI) by the employment of industrial catalysts are still lacking. Herein, an oxygen vacancy (V_O)-sustained prototype mediator with layer-number controllable graphene modification (Al₂O₃@mG) is developed for concurrently accelerating redox kinetics at the S cathode and harvesting inorganic-rich SEI at the Li anode. Theoretical and experimental analyses reveal that V_O enhances the electrocatalytic activity while the graphene overlay serving as a catalysis sustainer enables vacancy protection. Meanwhile, Al₂O₃@mG is conducive to homogenizing Li-ion flux and boosting preferential decomposition of anions, thereby stabilizing the Li metal anode. Benefiting from such dual-functional reformulation, Li–S batteries with Al₂O₃@mG modified separators achieve a low capacity decay of 0.032% per cycle over 1600 cycles at 1.0 C. The assembled pouch cell delivers high areal capacity and stable cycling operation. Such a vacancy-sustained graphene strategy showcases promising universality to be applied on various oxide candidates, offering meaningful guidance in mediator design toward pragmatic Li–S batteries.