The Polysulfide‐Cathode Binding Energy Landscape for Lithium Sulfide Growth in Lithium‐Sulfur Batteries
Ki-Won Kim, Jae Hyun Kim, Jun Hyuk Moon
Abstract
Abstract 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.