Revealing the Coordination and Mediation Mechanism of Arylboronic Acids Toward Energy-Dense Li-S Batteries

Abstract

Lithium-sulfur (Li─S) batteries offer a promising avenue for the next generation of energy-dense batteries. However, it is quite challenging to realize practical Li─S batteries under limited electrolytes and high sulfur loading, which may exacerbate problems of interface deterioration and low sulfur utilization. Herein, the coordination and mediation chemistry of arylboronic acids that enable energy-dense and long-term-cycling Li─S batteries is proposed. The coordination chemistry between NO₃⁻ and arylboronic acids breaks the resonance configuration of NO₃⁻ and thermodynamically promotes its reduction on the anode, contributing to a mechanically robust interface. The mediation chemistry between lithium arylborate and polysulfides distorts S─S/Li─S bonds, alters the rate-determining step from Li₂S₄→Li₂S₂ to Li₂S₆→Li₂S₄, and homogeneously accelerates the sulfur redox kinetics. Li─S batteries using 3,5-bis(trifluoromethyl)phenylboronic acid (BPBA) show excellent cycling stability (1000 cycles with a low capacity decay rate of 0.033% per cycle) and a high energy density of 422 Wh kg⁻¹ under aggressive chemical environments (high sulfur loading of 17.4 mg cm⁻² and lean electrolyte operation of 3.6 mL g_S⁻¹). The basic mechanism of coordination and mediation chemistry can be extended to other arylboronic acids with different configurations and compositions, thus broadening the application prospect of arylboronic acids in the electrolyte engineering of Li─S batteries.