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(2) S) during discharge is crucial for S utilization stimulates improvement of this preference. Here, the Li(2) 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(2) O(4) substrate with moderate LiPS affinity exhibits 3D Li(2) S growth. The MnCo(2) O(4) 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(2) O(4) and strong affinity substrates such as NiCo(2) O(4) and CuCo(2) O(4) exhibit low discharge capacity with 2D Li(2) 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.