Polycrystalline 1-D TiN-based free-standing composite electrode for high performance of Li-polysulfide cells

Abstract

Li‑sulfur batteries are expected to transform electrochemical energy storage technology by taking it to the next level, as it holds the possibility to obtain a higher energy density levels than state-of-the-art Li-ion batteries. The poor electrical conductivity of sulfur and the high diffusivity of the intermediate lithium polysulfides create various problems, which limit the utilization of the full potential of these batteries. Polar conductive sulfur hosts such as titanium nitride (TiN) make it possible to realize remarkable improvements in active material utilization and capacity retention outcomes over long-term cycling. It has not been possible to use these polar, conductive, ceramic materials for higher active material loading (>2 mg cm−2) due to their low flexibility compared to carbonaceous materials. Here, we demonstrate the possibility of designing a three-dimensional free-standing electrode using polycrystalline 1-D TiN for a relatively high sulfur loading of 2.5 mg cm−2. The electrochemical performance of this 1-D TiN-based electrode is compared to that of an electrode based on 1-D TiO2 (the starting material for TiN synthesis). The results demonstrate the catalytic effect of TiN by virtue of its endowed conductivity, leading to remarkable capacity retention and better active material utilization at high C-rates compared to a TiO2-based electrode.