Evaluation of the Stability of Trimethyl Phosphate as a Li-O-2 Battery Electrolyte via Multinuclear Solid-State NMR

Solid-state O-17 NMR was used to compare the stability of two potential Li-O-2 electrolytes tetraethylene glycol dimethyl ether (TEGDME) and trimethyl phosphate (TMP). The TEGDME electrolyte demonstrated superior stability to the TMP electrolyte. Li2O2 and evidence of electrolyte breakdown was observed in the TEGDME cell, whereas only electrolyte breakdown products were discovered within the TMP cell. Potential decomposition pathways of TMP are proposed here that account for the formation of the discharge species observed in the O-17, Li-7, H-1, and P-31 solid-state NMR of the cycled cathodes.