Novel nanostructured sulfur (S)-carbide derived carbon (CDC) composites with ordered mesopores and high S content are successfully prepared for lithium sulfur batteries. The tunable pore-size distribution and high pore volume of CDC allow for an excellent electrochemical performance of the composites at high current densities. A higher electrolyte molarity is found to enhance the capacity utilization dramatically and reduce S dissolution in S-CDC composite cathodes during cycling.

One of the most challenging problems in the development of lithium–sulfur batteries is polysulfide dissolution, which leads to cell overcharge and low columbic efficiency. Here, we propose the formation of a thin conformal Li‐ion permeable oxide layer on the sulfur‐carbon composite electrode surface by rapid plasma enhanced atomic layer deposition (PEALD) in order to prevent this dissolution, while preserving electrical connectivity within the individual electrode particles. PEALD synthesis offers a fast deposition rate combined with a low operating temperature, which allows sulfur evaporation during deposition to be avoided. After PEALD of a thin layer of aluminium oxide on the surface of electrode composed of large (ca. 10 μm in diameter) S‐infiltrated activated carbon fibers (S‐ACF), significantly enhanced cycle life is observed, with a capacity in excess of 600 mA·h·g−1 after 300 charge–discharge cycles. Scanning electron microscopy (SEM) shows a significant amount of redeposited lithium sulfides on the external surface of regular S‐ACF electrodes. However, the PEALD alumina‐coated electrodes show no lithium sulfide deposits on the fiber surface. Energy dispersive spectroscopy (EDS) studies of the electrodes’ chemical composition further confirms that PEALD alumina coatings dramatically reduce S dissolution from the cathodes by confining the polysulfides inside the alumina barrier.

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