Hydrogen-Bond-Assisted Solution Discharge in Aprotic Li-O₂ Batteries.

Abstract

Surface discharge mechanism induced cathode passivation is a critical challenge that blocks the full liberation of the ultrahigh theoretical energy density in aprotic Li-O₂ batteries. Herein, a facile and universal concept of hydrogen-bond-assisted solvation is proposed to trigger the solution discharge process for averting the shortcomings associated with surface discharge. 2,5-Di-tert-butylhydroquinone (DBHQ), an antioxidant with hydroxyl groups, is introduced as an exemplary soluble catalyst to promote solution discharge by hydrogen-bond-assisted solvation of O₂ ^- and Li₂ O₂ (OH···O). Thus, a Li-O₂ battery with 50 × 10^-3 m DBHQ delivers an extraordinary discharge capacity of 18 945 mAh g^-1 (i.e., 9.47 mAh cm^-2 ), even surpassing the capacity endowed by the state-of-the-art reduction mediator of 2,5-di-tert-butyl-1,4-benzoquinone. Besides, an ultrahigh Li₂ O₂ yield of 97.1% is also achieved due to the depressed reactivity of the reduced oxygen-containing species (O₂ ^- , LiO₂ , and Li₂ O₂ ) by the solvating and antioxidative abilities of DBHQ. Consequently, the Li-O₂ battery with DBHQ exhibits excellent cycling lifetime and rate capability. Furthermore, the generalizability of this approach of hydrogen-bond-assisted solution discharge is verified by other soluble catalysts that contain OH or NH groups, with implications that could bring Li-O₂ batteries one step closer to being a viable technology.