Asymmetric Electronic Configuration for Sustainable Lithium-Sulfur Batteries.

Abstract

Homonuclear diatomic catalysts (DACs) show potential for accelerating polysulfide conversion and suppressing the shuttle effect in Li-S batteries due to favorable energy-level matching. However, their intrinsic symmetric electronic structure restricts intermetallic electron transfer, leading to unbalanced polysulfides adsorption-desorption and thus limited catalytic conversion. Herein, we construct an asymmetric Co homonuclear DAC via sulfur coordination (CoDAC-S₁N₅). Theoretical calculations reveal that the symmetry-broken structure induces mild electron delocalization and charge redistribution. This electronic modulation contributes to cooperative yet differentiated roles of the two Co sites governed by their e_g/t_2g ratios, with one site strengthening polysulfide anchoring while the other promotes S─S bond activation. This dual-site synergy effectively overcomes the intrinsic trade-off between adsorption strength and catalytic activity, leading to accelerated polysulfide conversion kinetics and improved reaction reversibility. As a result, CoDAC-S₁N₅ delivers outstanding cycling stability over 65 cycles in Ah-level pouch cells and achieves an initial energy density of 567.8 Wh kg_total ^-1 at a low electrolyte-to-sulfur ratio of 2.1 µL mg S^-1. This work establishes symmetry breaking as a key design principle for homonuclear DACs, providing mechanistic insights into the synergistic enhancement of catalytic activity and stability in Li-S systems.