A flexible self-supporting ultralong MnO2 nanowires-expanded graphite nanosheets current collector with enhanced catalytic reaction kinetics for high-loading lithium-sulfur batteries

Abstract

Owing to the shuttle effect of lithium polysulfides (LiPSs), poor conductivity and low loading mass of active sulfur, and its large volume expansion during cycling, these shortcomings still restrict practical application of high performance lithium-sulfur (Li-S) batteries. Herein, a stable flexible current collector, composed of ultralong MnO 2 nanowires and expanded graphite nanosheets (MnO 2 NW/EG) with high electronic conductivity, is combined with Li 2 S 6 to serve as a self-supporting cathode in Li-S batteries, in which the maximum loading mass of sulfur can be regulated to 7 mg cm −2 , the ultralong MnO 2 nanowires has the ability to accelerate the adsorption and catalytic conversion of LiPSs through the chemical action of the polar active surface and the good mechanical flexibility caused by the introduction of ultralong nanowires and nanosheets can buffer the large volume expansion of sulfur during charging/discharging. Moreover, Li-S batteries with MnO 2 NW/EG current collector still maintain a high capacity of 538 mAh g −1 after 500 cycles at 1 C and the capacity decay is only 1.2 mAh g −1 per cycle, even when the sulfur loading is 7 mg cm −2 , the capacity can be as high as 2.5 mAh cm −2 , indicating a practical application ability. • A stable flexible current collector is applied in Li-S batteries. • The loading mass of sulfur can be regulated to 7 mg cm −2 • The MnO 2 nanowires can accelerate the adsorption and catalytic conversion of LiPSs. • The cathode with high sulfur loading mass exhibits excellent cyclic stability.