Novel positive electrode architecture for rechargeable lithium/sulfur batteries

Abstract

The lithium/sulfur battery is a very promising technology for high energy applications. Among other advantages, this electrochemical system has a high theoretical specific capacity of 1675mAhg−1, but suffers from several drawbacks: poor elemental sulfur conductivity, active material dissolution and use of the highly reactive lithium metal electrode. More particularly, the discharge capacity is known to be dictated by the short lithium polysulfide precipitation. These poorly soluble and highly insulating species are produced at the end of discharge, and are responsible for the positive electrode passivation and the early end of discharge. Nevertheless, the discharge capacity can be improved by working on the positive electrode specific surface area and morphology, as well as on the electrolyte composition. In this paper, we focused on the positive electrode issue. To this purpose, various current collector structures have been tested in order to achieve a high positive electrode surface area and a stable morphology during cycling. We demonstrated that the discharge capacity could be increased up to 1400mAhg−1 thanks to the use of carbon foam. As well, the capacity fading could be dramatically decreased in comparison with the one obtained for conventional sulfur composite electrodes.