Uniform growth of Li2S promoted by an organophosphorus-based mediator for high rate Li-S batteries

Lithium-sulfur (Li-S) batteries are impeded by the slow reaction kinetics of liquid (Li2Sn, n=4)-to-solid (Li2S2/Li2S) and uncontrollable interfacial electrodeposition of S species. Herein, bioinspired by the excellent catalytic effect of tris(2-carboxyethyl)phosphine hydrochloride (TCEP) on slicing disulfide bond, we confined commercialized organophosphorus TCEP in the pores of porous carbon nanosheets (PCN) and further modified PP separators by the PCN/TCEP composites. PCN/TCEP decreases the electrodeposition energy barrier, contributing to a uniform corrugated 2D Li2S film other than uncontrollable large Li2S2/Li2S islands. Benefitting from not only the catalytic effect of TCEP on long-chain polysulfide conversion to Li2S2/Li2S but also the promotion of disulfide bond breaking by thiosulfates, which is a by-product of TCEP catalysis, the polysulfide redox kinetics are propelled. The uniform distribution of S species and boosted polysulfides redox kinetics together account for low reaction resistance and stable dendrite-free lithium anode in the Li-S electrochemistry. As a result, by using PCN/TCEP@PP, a high rate performance up to 7.5 C (12.75 mA cm(-2), 503 mA h g(-1) in capacity) and long-term cycling stability (700 cycles at 1.0 C with a decay of 0.0356% per cycle) were achieved. This work provides an insight into interfacial chemistry to control electrodeposition process of S species and inspires more commercial functional interlayer materials for lithium-sulfur batteries.