Electrochemical behavior of sebaconitrile as a cosolvent in the formulation of electrolytes at high potentials for lithium-ion batteries

The electrochemical behavior of new high potential electrolyte containing sebaconitrile in LiPF6/EC:DMC or LiBF4 was studied on glassy carbon and LiCoO2, LiCoPO4 as positive electrode materials. The increase of sebaconitrile concentration in EC:DMC electrolyte provides better electrolyte stability at higher potentials on glassy carbon as observed by cyclic voltammetry. Promising electrochemical results showing good reversibility and insertion/deinsertion efficiency have been also obtained on LiCoPO4 electrode cycled up to 5.3 V vs Li+/Li as upper potential limit. However, the cycling of LiCoPO4 at higher potential (6 V vs Li+/Li) shows lower reversibility and efficiency of insertion/deinsertion process due to the oxidative decomposition of the electrolyte at high potentials. The surface analysis performed by X-ray photoelectron spectroscopy confirms the formation of a surface layer induced by electrolyte degradation on both types of positive electrodes, which hinder the Li diffusion. The layer composition and morphology vary as a function of electrolyte composition and type of electrode.