Electrochemical stability windows of electrolytes largely determine the limitations of operating regimes for lithium-ion batteries, ultimately affecting the overall performance of the battery. However, the detailed degradation mechanisms are difficult to characterize experimentally and remain poorly understood. Using computational quantum chemistry, we investigate the oxidative decomposition that limits the voltage stability of multi-component organic electrolytes. We find that the process of electrolyte decomposition involves both the solvent and the salt anion and its computational study requires explicit treatment of their coupling. We find that the ionization potential of the solvent-anion system is often lower than that of the isolated solvent or isolated anion. This mutual weakening effect is explained by the possibility of formation of the anion-solvent charge-transfer complex, depending on the energy tradeoff between ionization potentials and the electrostatic energy of a charge-transfer complex. After carefully studying different density functional theory functionals to assess which one describes better the electrostatic of oxidation of such systems, we study this weakening effect for 16 anion-solvent combinations. This understanding of the oxidation mechanism allows to formulate a simple predictive model that explains experimentally observed trends in the onset voltages of degradation of electrolytes near the cathode. This model opens opportunities for rapid rational design of stable electrolytes for high-energy batteries.

Role of solvent-anion charge transfer in oxidative degradation of battery electrolytes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.