The theoretical energy density of lithium-oxygen batteries is by far the closest competitor to gasoline compared to other battery configurations. Unfortunately, the commercial implementation of this technology is hindered by the poor cycling performance, mostly due to the slow oxygen evolution/reduction kinetics. The sluggish oxygen evolution kinetics are typically more severe and cause the slow oxidation of lithium peroxide. This can cause the irreversible formation of a passivating lithium peroxide layer on the cathode surface. The interfacial dynamics due to the growth of lithium peroxide and the formation of cathode-electrolyte interface (CEI) layers remains largely unknown. It is crucial to elucidate how the nucleation of discharge products on the cathode surface affects the electrochemical performance in order to design new electrolytes and cathodes for lithium-oxygen batteries. In this study, we investigate the impact of the electrolyte salt on nanoscale dynamic changes on the surface of the thin Au film cathode (1-D) during charge / discharge of Li-O2 batteries. Thin Au films were deposited via e-beam evaporation onto a borosilicate glass substrate. These substrates were used as a cathode material. The electrolyte used was 1 M LiTFSI or LiNO3 in DMSO, and it was saturated with oxygen prior to performing electrochemical measurements. In situ stress measurements were conducted using a multiple beam optical sensor (MOS). A custom cell was designed to monitor the physical response of the cathode during cycling while enabling optical access to the back of the substrate for stress measurements. In situ curvature evolution on Au thin film cathode is monitored during discharge and charge cycle via galvanostatic and cycling voltammetry. In this talk, we will present the impact of the electrolyte salt on the potential-dependent surface stress generation during the formation and oxidation of electrochemical redox reaction products at nanoscale on the Au thin film cathode. Revealing the mechanical response of the charge / discharge products on cathode electrode will shed light into the formation mechanisms of these products, which is crucial to design new electrolyte and cathodes for Li-O2 batteries.

In situ stress measurement during oxygen evolution and reduction reactions on Au cathode for Li-O2 batteries

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.