Deciphering the e_g occupancy descriptor on perovskite oxides for lithium-sulfur batteries

The partially filled d orbital of transition metal-based catalysts demonstrate excellent catalytic activity against polysulfides. However, an appropriate descriptor to reveal their structure-activity relationship is lacked. This study proposes a quantitative relationship between the e_g occupancy of perovskite oxides and polysulfide catalytic activity, serving as an activity descriptor. LaCoO₃, with a moderate e_g occupation (t_2g⁵e_g^1.08), demonstrates effective polysulfide anchoring and facilitated redox kinetics conversion compared to LaCrO₃ (t_2g³e_g⁰) and LaFeO₃ (t_2g³e_g²), showcasing exceptional catalytic performance. The degree of e_g occupancy significantly influences the polysulfides adsorption strength, with empty or fully filled e_g orbitals resulting in either strong or weak adsorption, respectively. LaCoO₃-based batteries exhibit remarkable reversible capacity over 700 cycles at 1.0C, with a minimal capacity fading rate of 0.065 % per cycle. This work elucidates the crucial role of e_g descriptor for evaluating the adsorption and conversion on polysulfides, offering insights into the development of innovative lithium-sulfur electrocatalysts.