Hydrogen-Bond-Assisted Solution Discharge in Aprotic Li-O2 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 Li2O2 (O-H center dot center dot center dot O). Thus, a Li-O-2 battery with 50 x 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 Li2O2 yield of 97.1% is also achieved due to the depressed reactivity of the reduced oxygen-containing species (O-2(-), LiO2, and Li2O2) 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.

Automated summary

This study proposes a new method to address cathode passivation in aprotic Li-O-2 batteries by utilizing hydrogen-bond-assisted solvation. An exemplary soluble catalyst called 2,5-di-tert-butylhydroquinone (DBHQ) is introduced to promote solution discharge and improve the discharge capacity and yield of Li2O2. The generalizability of this hydrogen-bond-assisted solvation approach is also verified with other soluble catalysts containing -OH or -NH groups.