Clarification of Solvent Effects on Discharge Products in Li-O2 Batteries through a Titration Method

ACS Applied Materials & Interfaces

ACS Appl. Mater. Interfaces, Just Accepted Manuscript

As a substitute for current lithium-ion batteries (LIBs), rechargeable Li-O2 batteries have attracted much attention due to their theoretically high energy density, but many challenges continue to exist. For the development of this still problematic battery, understanding and controlling the main discharge product (Li2O2, lithium peroxide) are of paramount importance. Here, we comparatively analyzed the amount of Li2O2 in the cathodes discharged at various discharge capacities and current DMSO and TEGDME solvents. The precise assessment entailed revisiting and revising the UV-Vis titration analysis. The amount of Li2O2 electrochemically formed in DMSO was less than that formed in TEGDME at the same capacity and even at a much higher full discharge capacity in DMSO than in TEGDME. Based on our analytical experimental results, this unexpected result was ascribed to the presence of soluble LiO2-like intermediates that remained in the DMSO solvent and the chemical transformation of Li2O2 to LiOH, both of which originated from the inherent properties of the DMSO solvent.
December 2017
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