Advanced engineering of nanostructured carbons for lithium-sulfur batteries

The present-day lithium ion batteries represent a brilliant electrochemical energy storage technology that has established a dominant niche in portable electronics, yet loses the potentiality in applications that demand increasing energy density such as electric vehicles. Lithium-sulfur (Li-S) batteries are considered as an alternative candidate owing to its ultrahigh energy density, low cost, natural abundance, and eco-friendliness. However, the paramount challenges to become a viable technology include inferior utilization of active materials, short cycle life, and low Coulombic efficiency, which are closely associated with the structural designs of sulfur cathodes. Significant progresses and breakthroughs have been made in the most recent years towards the successful modification of the sulfur cathodes for high-performance Li-S batteries. Among them, nanostructured carbons have been demonstrated to be particularly effective to address the critical hurdles mentioned above. To promote the advancement of this exciting field, this article herein will discuss the progresses of the sulfur cathodes with an emphasis on the advanced engineering of nanostructured carbons to improve specific capacity and Coulombic efficiency, high-rate capability, and cycling retention. The review article primarily covers "inside" and "outside" design strategies on cathodes by developing carbon-sulfur composites and novel cell configurations, respectively. Discussion will be detailed to correlate synthesis principles and characteristics of nanostructured carbons with electrochemical performance.