In Situ Analysis of the Li–O2 Battery with Thermally Reduced Graphene Oxide Cathode: Influence of Water Addition

The Li–O2 battery technology holds the promise to deliver a battery with significantly increased specific energy compared to today’s Li-ion batteries. As a cathode support material, reduced graphene oxide has received increasing attention in the Li–O2 battery community due to the possibility of increased discharge capacity, increased battery cyclability, and decreased charging overpotential.

In this article we investigate the effect of water on a thermally reduced graphene oxide cathode in a Li–O2 battery. Differential electrochemical mass spectroscopy reveals a decreased electron count for batteries with 1000 ppm water added to the electrolyte in comparison to dry batteries, indicating additional parasitic electrochemical or chemical processes. A comparable capacity of the wet and dry batteries indicates that the reaction mechanism in the Li–O2 battery also depends on the surface of the cathode and not only on addition of water to the electrolyte as demonstrated by the solution-based mechanism. In situ synchrotron X-ray diffraction experiment using a new design of a capillary-based Li–O2 cell with a thermally reduced graphene oxide cathode shows formation of LiOH along with Li2O2.