Three-Layer Sulfur Cathode with a Conductive Material-Free Middle Layer.

An ingenious design for a three-layer sulfur cathode is demonstrated, in which the pure sulfur layer is sandwiched between carbon nanotube (CNT) films. The unique feature of this particular model is that the sulfur layer does not contain any conductive materials, and therefore, the top CNT film of the prepared three-layer CNT/S/CNT electrode is electrically isolated from the bottom CNT film. Scanning electron microscopy studies revealed that the three-layer cathode was transformed into a single CNT cathode, with proximate contact between the two CNT films in the upper plateau of the first discharge. The lithium-sulfur cells employing a CNT/S/CNT cathode exhibited remarkably enhanced performance in terms of the specific capacity, rate property, and cycling stability compared to the cells with a sulfur-coated CNT cathode. This can mainly be attributed to the top CNT film, which serves not only as an interlayer to trap the migrating polysulfides, but also as an electrode to facilitate the redox reaction of active materials. Such an innovative approach is promising as it may promote the rational design of high-performance sulfur cathodes.