Challenges with prediction of battery electrolyte electrochemical stability window and guiding the electrode – electrolyte stabilization

Abstract

Progress in development of novel battery chemistries critically depends on the stabilization of electrode – electrolyte interfaces. Battery electrolytes are commonly selected to either be electrochemically stable at the electrode, current collector, and conductive additive surfaces or to decompose at these interfaces electrochemically and form a kinetically protective ionically-conducting but electronically-insulating passivation film. Increasing energy density of electrical double layer (EDL) capacitors, or supercapacitors, also requires electrolytes with an extended electrochemical stability window. Quantum chemistry (QC) calculations of the representative electrolyte clusters or electrolyte components reacting with the electrode surfaces provide molecular scale understanding of the key electrolyte decomposition pathways under reductive or oxidative conditions. Moreover, QC calculations show that the electrolyte reduction and oxidation stability depends on the solvent and salt partitioning within EDL near electrolytes and the number of lithium cations complexing anions or solvents. Thus, an electrolyte electrochemical stability could be controlled by adjusting salt concentration, salt aggregation and preferential solvent or anion partitioning within EDL, opening new opportunities for enabling aggressive battery chemistries and EDL capacitors with improved energy densities.