Cathode Reactions in the Rechargeable Aprotic Li-O2 Battery
Authors: Holc Conrad , Bruce Peter G. 
Published: February 2020

Rechargeable battery technologies such as Li-ion have revolutionised personal electronics over the last 25 years. However, Beyond Li-ion technologies are becoming increasingly important towards meeting society’s future energy storage needs. We must explore these alternatives, such as the Li-air (O2) battery, which can offer higher practical specific energy densities than Li-ion batteries; however there remain many challenges to be overcome before Li-O2 batteries are commercialised.1-5 One spin-off from the recent interest in rechargeable Li-O2 batteries, based on aprotic electrolytes, is the significant advances made in understanding the fundamental processes occurring on O2 reduction (discharge) at the cathode.6-12

Based on these studies, it is generally accepted that a solution growth mechanism will be required to achieve high rates and capacities. One way to achieve discharge in solution is use of high donor or acceptor number (DN/AN) electrolytes,13,14 but these are typically less stable towards LiO2 and Li2O2 than their low DN/AN counterparts.15 To solve this dilemma, additives, such as redox mediators, have been introduced into low DN/AN electrolytes to encourage the discharge in solution.13,16-18 Here, we discuss our recent studies into the electrochemistry at the cathode, in the presence of additives and utilise a range of electrochemical and spectroscopic techniques to determine the precise nature in which additives influence O2 reduction.
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