Polysulfide solution effects on Li[sbnd]S batteries performances

Recently, rechargeable Li[sbnd]S batteries, a next-generation energy storage system, are deeply studied due to their theoretical specific energy density. However, to produce batteries comparable to those already available on the market some drawbacks must be overcome, including essentially self-discharge, high internal resistance and rapid capacity fading upon cycling. In this work the use of polysulfide solutions either as additives or as active material in Li[sbnd]S batteries is proposed. The addition of polysulfides to the electrolytic solution improves the cell performances in terms of specific capacity and coulombic efficiency, passing from a capacity of about 150 mAh/g with a coulombic efficiency of about 0.85 to a capacity of 600 mAh/g with a coulombic efficiency of about 0.99 after 10 cycles. In batteries where polysulfide solutions are used as cathodic material, the obtained performances are even higher, reaching specific capacities of 420–450 mAh/g after about 70 cycles. Moreover, the cells tested with carbon paper as electrode support shows a greater reversibility, with a coulombic efficiency very close to 1. Finally, reducing the potential window from 3 to 1.5 V to 2.8–1.7 V, the cells show high stability and efficiency, reaching specific capacity values of about 600 mAh/g after 200 cycles.