Graphene Chainmail-Enabled Moderate Precatalyst Phase Evolution for Sustainable Polysulfide Electrocatalysis in Li─S Batteries.

Abstract

The rational design of polysulfide electrocatalysts is of vital importance to achieve longevous Li─S batteries. Notwithstanding fruitful advances made in elevating electrocatalytic activity, efforts to regulate precatalyst phase evolution and protect active sites are still lacking. Herein, an in situ graphene-encapsulated bimetallic model catalyst (CoNi@G) is developed for striking a balance between electrocatalytic activity and stability for sulfur electrochemistry. The layer numbers of directly grown graphene can be dictated by tuning the synthetic duration. Exhaustive experimental and theoretical analysis comprehensively reveals that the tailored graphene chainmail boosts catalytic durability while guaranteeing moderate phase evolution, accordingly attaining a decorated surface sulfidation with advanced catalytic essence. Benefiting from the sustainable polysulfide electrocatalysis, CoNi@G enabled sulfur electrodes to harvest a capacity output of 1276.2 mAh g^-1 at 0.2 C and a negligible capacity decay of 0.055% per cycle after 1000 cycles at 1.0 C. Such a maneuver can be readily extended to other metallic catalysts including NiFe, CoFe, or Co. The work elucidates the precatalyst phase evolution mechanism through a controllable graphene-armored strategy, offering meaningful guidance to realize durable electrocatalysts in Li─S batteries.