CAREER: Molecular Mechanisms Underlying Redox Chemistry in Electrochemical Cells from First Principles

University Of California-San Diego, La Jolla CA

Investigators

Abstract

Fast-charging, durable and sustainable batteries are critical for the applications of stationary, grid-scale energy storage and for propulsion in battery electric vehicles. The chemical and physical processes that occur at the electrode surface of a battery contacting the electrolyte has a significant impact on the overall observed performance of the system. Understanding the mechanisms of the chemistry and physics at the electrode’s interface with the battery electrolyte has been an ongoing challenge due to the complexity of the materials chemistry, morphology, and coupling of electrochemical processes. Predictive modeling of these electrochemical interfaces is a grand challenge, with potentially revolutionary scientific and technological applications. This project will develop a first principles, physics based, computational platform for elucidating the complex physics, structure, and dynamics of electrolytic solutions next to “realistic” electrodes, i.e., those with non-uniform surface geometries, chemistries, and morphologies. The successful completion of the project will lead to an improved understanding of the complex processes at the electrode, leading to new strategies for optimizing high energy density batteries, fuel cells, and other electrochemical systems. The project includes research opportunities for high school, community college, undergraduate, and graduate students. An example educational effort is development of a Immersive Material Discovery Platform to enable enriched hands-on, active learning for the teaching of computational electrochemistry that will use virtual reality, sound, and haptic feedback. Determining the properties of the nanoscale region at the electrode/electrolyte interface is of importance because near a polarizable metal interface, and in contrast to the bulk, symmetry breaking results in unique quantum mechanical effects that in turn gives rise to modified electrolyte structure, dynamics, and thermodynamics, which ultimately determines device function. This project’s computational framework addresses an approach that is capable of describing solvent dynamics, and charge transfer and reorganization physics at the electrode and in the electric double layer, while fully capturing the response due to a change in electrode potential. The project’s computational framework addresses the fundamental question of how changes in the electrode electron density affects the solvation dynamics and charge fluctuations of nearby ionic species. The project includes extensive computer simulations with several novel algorithmic and theoretical advances. The first objective of the project will describe the critical electrostatics using an interface sensitive, fluctuating charge model that will allow the modelling of Lithium in its metallic, semi-metallic and ionic states within the same simulation cell. The second objective will develop an approach for simulating applied voltage bias, based on self-consistently adjusting the electrochemical potential of the dynamically varying electrode atoms. Both advances will enable simulations of the charge/discharge process in a full-cell battery setup. The third research objective will relate changes in the interfacial atomic structure to the QM electronic structure by simulated X-ray spectroscopy. These spectra will be directly comparable to recent interface sensitive X-ray measurements, providing a feedback loop for both validating and improving the theory. The successful completion of the project is expected to address a critical knowledge gap concerning role of charge renormalization and transfer at model electrodes, due to electrolyte dynamics. Research outcomes will enable predictive design and nanoscale engineering optimization strategies for new high energy density battery systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.