Investigating oxidative stability of lithium-ion battery electrolytes using synthetic charge-discharge profile voltammetry
Alma Mathew, Matthew J. Lacey, Daniel Brandell
Abstract
Electrolytes are an integral part of any electrochemical energy storage systems, including batteries. Among the many properties which determine the applicability of a Li-ion battery electrolyte, electrochemical stability – and for high voltage electrodes, in particular anodic stability – is a key parameter to consider. Despite being simple and straightforward to employ, the conventional linear sweep voltammetry (LSV) technique often leads to an over-estimation of the oxidative stability. In this study, an alternative approach termed Synthetic Charge-discharge Profile Voltammetry (SCPV) is explored to investigate the oxidative electrolyte stability. We have found this to be a convenient method of quantifying the anodic stability of the electrolyte in a more practically representative manner, in which passivation kinetics and electrode potential changes at the electrode-electrolyte interface are more appropriately reproduced. The viability of this technique is explored with liquid electrolytes based on ether, carbonate, sulfone and carbonate-sulfone mixtures, all with lithium hexafluorophosphate (LiPF6) salt, tested for a potential profile equivalent to LiNi0.5Mn1.5O4 electrodes. The credibility of this technique is validated by correlations to the coulombic efficiencies of corresponding half-cells.