Examining the role of electrolyte and binders in determining discharge product morphology and cycling performance of carbon cathodes in Li-O₂ batteries

In this report we examine the influence of electrode binder and electrolyte solvent on the electrochemical response of carbon based Li-O₂ battery cathodes. Much higher discharge capacities were noted for cathodes discharged in DMSO compared to TEGDME. The increased capacities were related to the large spherical discharge products formed in DMSO. Characteristic toroids which have been noted in TEGDME electrolytes previously were not observed due to the low water content of the electrolyte. Linear voltage sweeps were used to investigate ORR in both of the solvents for each of the binder systems (PVDF, PVP, PEO and PTFE) and related to the Li₂O₂ formed on the cathode surfaces. Galvanostatic tests were also conducted in air as a comparison with the pure O₂ environment typically used for Li-O₂ battery testing. Interestingly, tests for the two electrolytes showed opposite trends in terms of discharge capacity values with capacities increased in TEGDME (compared to those seen in O₂) and decreased in DMSO. The report highlights the key roles of electrolyte and cathode composition in determining the stability of Li-O₂ batteries and highlights the importance of identifying more stable electrolyte/cathode pairings.