A High-Performance Li-O-2/Air Battery System with Dual Redox Mediators in the Hydrophobic Ionic Liquid-Based Gel Polymer Electrolyte

Lithium-oxygen (Li-O-2) batteries have captured worldwide attention owing to their highest theoretical specific energy density. However, this promising system still suffers from huge discharge/charge overpotentials and poor cycling stability, which are related to the leakage/volatilization of organic liquid electrolytes and the inefficiency of solid catalysts. A mixing ionic liquid-based gel polymer electrolyte (IL-GPE)-based Li-O-2 battery, consisting of a 20 mM 2,5-di-tert-butyl-1,4-benzoquinone (DBBQ) 40 mM N-methylphenothiazine (MPT)-containing IL-GPE and a single-walled carbon nanotube cathode, is designed for the first time here. This unique dual redox mediators-based GPE, which contains a polymer matrix immersed with mixed ionic liquid electrolyte, provides a proper ionic conductivity (0.48 mS cm(-1)) and effective protection for lithium anode. In addition, DBBQ, as the catalyst for an oxygen reduction reaction, can support the growth of discharge products through the solution-phase pathway. Simultaneously, MPT, as the catalyst for an oxygen evolution reaction, can decompose Li2O2 at low charge overpotentials. Hence, the DBBQ-MPT-IL-GPE-based Li-O-2 battery can operate for 100 cycles with lower charge/discharge overpotentials. This investigation may offer a promising method to realize high-efficiency Li-O-2/air batteries.