A graphene foam electrode with high sulfur loading for flexible and high energy Li-S batteries

Abstract

Lithium-sulfur (Li-S) batteries have attracted great attention as next-generation high specific energy density storage devices. However, the low sulfur loading in the cathode for Li-S battery greatly offsets its advantage in high energy density and limits the practical applications of such battery concepts. Flexible energy storage devices are also becoming increasingly important for future applications but are limited by the lack of suitable lightweight electrode materials with robust electrochemical performance under cyclic mechanical strain. Here, we proposed an effective strategy to obtain flexible Li-S battery electrodes with high energy density, high power density, and long cyclic life by adopting graphene foam-based electrodes. Graphene foam can provide a highly electrically conductive network, robust mechanical support and sufficient space for a high sulfur loading. The sulfur loading in graphene foam-based electrodes can be tuned from 3.3 to 10.1mgcm−2. The electrode with 10.1mgcm−2 sulfur loading could deliver an extremely high areal capacity of 13.4mAhcm−2, much higher than the commonly reported Li-S electrodes and commercially used lithium cobalt oxide cathode with a value of ~3–4mAhcm−2. Meanwhile, the high sulfur-loaded electrodes retain a high rate performance with reversible capacities higher than 450mAhg−1 under a large current density of 6Ag−1 and preserve stable cycling performance with ~0.07% capacity decay per cycle over 1000 cycles. These impressive results indicate that such electrodes could enable high performance, fast-charging, and flexible Li-S batteries that show stable performance over extended charge/discharge cycling.