Investigating oxidative stability of lithium-ion battery electrolytes using synthetic charge-discharge profile voltammetry

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 LiNi_0.5Mn_1.5O₄ electrodes. The credibility of this technique is validated by correlations to the coulombic efficiencies of corresponding half-cells.