Density Functional Theory Study on ZIF‐8 MOF Anchors for Mitigating Polysulfide Shuttling in Calcium–Sulfur Batteries

Integrating porous materials, especially, metal organic frameworks (MOFs) as anchoring components on cathode surfaces enhances sulfur–based battery performance due to strong polysulfide anchoring affinity. This study employs a thermodynamically stable ZIF–8 cluster to improve the electrochemical behavior of calcium–sulfur (Ca─S) batteries by trapping polysulfides (PS), including α–S ₈ , CaS ₈ , CaS ₆ , CaS ₄ , CaS ₂ , and CaS, within its hexagonal window. The computationally efficient ZIF–8 cluster confirms effective PS adsorption, with energies ranging from –0.75 to –4.94 eV for α–S ₈ through CaS. Projected density of states analysis reveals Ca─N interactions for higher–order PS, while lower–order PS exhibit strong C─S bonds. Bader charge and charge density difference analyses reveal charge accumulation on sulfur atom in CaS and charge depletion on the carbon atom of the 2‐methylimidazolate ligand involved in C─S bonding. The calculated Gibbs free energy change of 0.74 eV for the transition of CaS ₄ to CaS ₂ identifies this as the rate‐limiting step in the sulfur reduction pathway. Furthermore, the relatively low adsorption energies (≤ –1 eV) of PS in the selected electrolyte environment suggest that dissolution of higher‐order PS into the electrolyte during discharge is unlikely, supporting improved electrochemical stability.