Ultramicroporous carbon aerogels encapsulating sulfur as the cathode for lithium–sulfur batteries

Abstract

Highly porous carbon materials employed in sulfur cathodes are of utmost importance to the charge transport, conductivity and stability of the cathode in metal–sulfur batteries. Herein, ultramicroporous carbon aerogels as conductive matrices embedding sulfur for cathode application in lithium–sulfur batteries are synthesized and investigated. Resulting from organic resorcinol–formaldehyde aerogels, the synthesized carbon aerogels feature a highly porous structure with a surface area of 500–2000 m2 g−1 and large micropore volume up to 0.6 cm3 g−1. The effective gas-phase sulfur infiltration of the carbon aerogels and the resulting confinement of sulfur in the micropores are demonstrated. It is indicated that sulfur-infiltrated microporous carbon aerogel cathodes are able to suppress the polysulfide shuttle effect, maintaining 80% (≥1000 mA h g(S)−1) and 70% (≥800 mA h g(S)−1) of the initial discharge capacity after 200 cycles at a rate of 0.3C in carbonate and ether-based electrolytes, respectively. Remarkably, the herein prepared composite cathode can still deliver a discharge capacity of at least 700 mA h g(S)−1 at a faster rate of 2C in both electrolyte systems. The cyclability and compatibility of the ether and carbonate-based electrolytes with such a composite cathode are discussed elaborately.