Hydrogen-Bond-Assisted Solution Discharge in Aprotic Li-O 2 Batteries.

Surface discharge mechanism induced cathode passivation is a critical challenge that blocks the full liberation of the ultrahigh theoretical energy density in aprotic Li-O 2 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 O 2 - and Li 2 O 2 (OH···O). Thus, a Li-O 2 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 Li 2 O 2 yield of 97.1% is also achieved due to the depressed reactivity of the reduced oxygen-containing species (O 2 - , LiO 2 , and Li 2 O 2 ) by the solvating and antioxidative abilities of DBHQ. Consequently, the Li-O 2 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-O 2 batteries one step closer to being a viable technology.