Molecular Perturbation of 2D Organic Modifiers on Porous Carbon Interlayer: Promoted Redox Kinetics of Polysulfides in Lithium-Sulfur Batteries

Abstract

The rate performance of Li-S batteries still remains poor due to the limited redox kinetics of polysulfides (PSs). Herein, by selectively coating a set of 2-demensional (2D) organic molecules, chenodeoxycholic acid (CA), 4,4′,4′′,4′′′-(porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) (TTBA), berberine chloride hydrate (BCH) and poly(diallyl dimethyl ammonium chloride) (PDDA) on honey comb-like porous carbon (HC) interlayers, respectively, the redox kinetics of PSs are remarkably enhanced in the interspace between the 2D molecules and carbon matrix, in the order of CA<TTBA<BCH<PDDA, with the most efficient molecules featured with positively charged amino groups. The capacity of Li-S batteries with PDDA on HC interlayer goes up to 637.6 mAh g–1 at 10 C and maintains 601.7 and 483.5 mAh g–1 after 1200 cycles at 2 C and 4 C, corresponding to a decay as low as 0.024% and 0.031% per cycle. Moreover, a reversible high areal capacity of 8.4 mAh cm−2 at 0.1 C and superior stability was achieved at a sulfur loading of 8.9 mg cm−2. This surface passivation technique is demonstrated to be a general strategy for any other carbon materials in promoting the redox kinetics of PSs as interlayers in Li-S batteries.