The Polysulfide-Cathode Binding Energy Landscape for Lithium Sulfide Growth in Lithium-Sulfur Batteries.

A cathode substrate with strong adsorption of lithium polysulfides (LiPSs) has been preferred for lithium-sulfur (Li-S) batteries. However, the recent finding that controlled growth of lithium sulfides (Li S) during discharge is crucial for S utilization stimulates improvement of this preference. Here, the Li S growth and cell capacity in the LiPS binding energy landscape of cathode substrates are investigated. Specifically, Co-based ternary oxides are employed to obtain binding energies in the range of 4.0-7.4 eV. Of these substrates, only the MnCo O substrate with moderate LiPS affinity exhibits 3D Li S growth. The MnCo O cells achieve high sulfur utilization up to 84% at 0.2 C and excellent performance even under high sulfur loading/lean electrolyte conditions. In contrast, weak affinity substrates such as ZnCo O and strong affinity substrates such as NiCo O and CuCo O exhibit low discharge capacity with 2D Li S growth. For optimal LiPS affinity driving 3D growth, a balance between promoting LiPS adsorption and diffusion limitation in the LiPS adsorption layer is suggested.