Promoting Reversible Redox Kinetics by Separator Architectures Based on CoS2 /HPGC Interlayer as Efficient Polysulfide-Trapping Shield for Li-S Batteries.

Abstract

Main obstacles from the shuttle effect and slow conversion rate of soluble polysulfide compromise the sulfur utilization and cycling life for lithium sulfur (Li-S) batteries. In pursuit of a practically viable high performance Li-S battery, a separator configuration (CoS2 /HPGC/interlayer) as efficient polysulfide trapping barrier is reported. This configuration endows great advantages, particularly enhanced conductivity, promoted polysulfide trapping capability, accelerated sulfur electrochemistry, when using the functional interlayer for Li-S cells. Attributed to the above merits, such cell shows excellent cyclability, with a capacity of 846 mAh g-1 after 250 cycles corresponding to a high capacity retention of 80.2% at 0.2 C, and 519 mAh g-1 after 500 cycles at 1C (1C = 1675mA g-1 ). In addition, the optimized separator exhibits a high initial areal capacity of 4.293 mAh cm-2 at 0.1C. Moreover, with CoS2 /HPGC/interlayer, the sulfur cell enables a low self-discharge rate with a very high capacity retention of 97.1%. This work presents a structural engineering of the separator toward suppressing the dissolution of soluble Li2 Sn moieties and simultaneously promoting the sulfur conversion kinetics, thus achieving durable and high capacity Li-S batteries.