Sulfonic\nGroups Originated Dual-Functional Interlayer for High Performance\nLithium–Sulfur Battery

Abstract

The lithium–sulfur\nbattery is one of the most prospective chemistries in secondary energy\nstorage field due to its high energy density and high theoretical\ncapacity. However, the dissolution of polysulfides in liquid electrolytes\ncauses the shuttle effect, and the rapid decay of lithium sulfur battery\nhas greatly hindered its practical application. Herein, combination\nof sulfonated reduced graphene oxide (SRGO) interlayer on the separator\nis adopted to suppress the shuttle effect. We speculate that this\nSRGO layer plays two roles: physically blocking the migration of polysulfide\nas ion selective layer and anchoring lithium polysulfide by the electronegative\nsulfonic group. Lewis acid–base theory and density functional\ntheory (DFT) calculations indicate that sulfonic groups have a strong\ntendency to interact with lithium ions in the lithium polysulfide.\nHence, the synergic effect involved by the sulfonic group contributes\nto the enhancement of the battery performance. Furthermore, the uniformly\ndistributed sulfonic groups working as active sites which could induce\nthe uniform distribution of sulfur, alleviating the excessive growth\nof sulfur and enhancing the utilization of active sulfur. With this\ninterlayer, the prototype battery exhibits a high reversible discharge\ncapacity of more than 1300 mAh g^–1 and good capacity\nretention of 802 mAh g^–1 after 250 cycles at 0.5\nC rate. After 60 cycles at different rates from 0.2 to 4 C, the cell\nwith this functional separator still recovered a high specific capacity\nof 1100 mAh g^–1 at 0.2 C. The results demonstrate\na promising interlayer design toward high performance lithium–sulfur\nbattery with longer cycling life, high specific capacity, and rate\ncapability.