Directing electrochemical reaction mechanism via interfacial control for better sulfur cathode

The “shuttle effect” in ether electrolyte or nucleophilic reaction in carbonate electrolyte are major obstacles to developing of lithium-sulfur (Li–S) batteries. Superficial sulfur on the outside of microporous carbon host can occur“shuttle effect” in ether electrolyte or nucleophilic reaction in carbonate electrolyte, which may affect the electrochemical reaction mechanism for lithium-sulfur batteries and need to be further clarified. Herein, we rationally designed microporous carbon and non-microporous carbon as the sulfur hosts, and manipulated the distribution of sulfur via interfacial control in cathode material, exhibiting diverse electrochemical behavior in carbonate electrolyte and ether electrolyte. The surface composition of the electrode was confirmed by ex-situ XPS and verified by in-situ XRD, which contributes to demonstrating the definite reaction mechanisms of lithium-sulfur batteries in the different electrolytes. The results show only the sulfur confined in microporous structure is active via “solid–solid” pathway, and the presence of sulfur on the outer surface of the cathode electrode has the negative effect on electrochemical performance in both electrolytes, which should be avoided in the fabrication of carbon/sulfur composites. Based on microporous carbon/sulfur composites, the lithiated Ge-S full cell was proposed and exhibited superior cycling performance and high Coulombic Efficiency.