Towards a Better Understanding of Aprotic Alkali-Oxygen Batteries

In the search for high density electrochemical energy storage, non-aqueous rechargeable metal-O₂ batteries are very attractive owing to their reliance on molecular oxygen, which forms oxides on discharge that release oxygen reversibly on charge. Much work has focused on aprotic Li–O₂ cells, but the aprotic Na-O₂ system is of equal interest owing to its more reversible chemistry.  In both cells, a chemically stable and conductive cathode interface is prerequisite for sustainable cell operation, along with a non-aqueous electrolyte that minimizes parasitic reactions at the electrode/electrolyte interface.  Li-O₂ cells (unlike their sodium counterparts), are also characterized by a high charge overpotential that must be overcome in order to increase round-trip efficiency.  In the last year, much progress has been made towards achieving these goals owing to a better understanding of the cell chemistries.   This presentation will focus on those topics, covering developments from our lab that include non-carbonaceous cathode hosts that possess stable conductive interfaces for reduced polarization on O₂ evolution, and novel soluble oxidation catalysts capable of Li₂O₂ oxidation without direct electrical contact with the cathode.  Characterization techniques ranging from electron microscopy, surface spectroscopy and operando electrochemical mass spectrometry have been applied to investigate the viability of various proposed systems.  This has resulted a deeper understanding of the critical parameters for positive electrodes in aprotic A-O₂ batteries, which will be presented in this talk.