The interface between electrodes and electrolytes hosts a fascinating array of chemical processes that are central to the performance of electrochemical energy storage devices. The microscopic properties of these interfaces are often highly complex, and the coupling of multiple redox-active processes is subtle, and often not well understood. We are interested in developing new computational approaches to model phase transitions, chemical reactivity, and electron transfer in these systems, and employing spectroscopic techniques to establish connections with experimental observables. We will couple computer simulations utilizing highly accurate, ab initio force fields with QM/MM techniques to enable predictive, first-principles descriptions of these complex chemical environments.
Nanostructured Carbon Electrodes
Nano-engineering electrodes is an important technique for enhancing the energy storage of supercapacitor devices. We are developing methods based on reactive molecular dynamics and Monte Carlo techniques to computationally model the structure and properties of nanoporous carbon materials. We explore combinations of nanoporous carbons and electrolyte mixtures to understand how nanoconfinement affects the properties of electrochemical systems, and employ sophisticated Monte Carlo approaches to predict equilibrium between electrolyte concentrations in nanoconfined and bulk liquid solutions. We will also utilize X-ray and neutron scattering analysis, as well as spectroscopy, to establish connections with analogous systems that have been experimentally synthesized and characterized.
Proton Transport in Synthetic and Biological Membranes
Proton transport is fundamental to many technological applications as well as biological processes. Unlike the transport of other ions, proton diffusion proceeds by a very special "Grotthuss" mechanism involving the thermal rearrangement of covalent and hydrogen bonds in aqueous environments. This leads to protons efficiently "hopping" along water wires, the rate of which is sensitively dependent on nanoconfinement and electrostatic interactions with the surroundings. From a computational perspective, modeling proton transport is difficult because it involves breaking and forming chemical bonds--not captured by standard molecular mechanics force fields. We are developing a synergy of reactive molecular dynamics and Monte Carlo methods to simulate proton transport over large length and time scales while incorporating realistic chemical detail, and will apply these approaches to important transport processes in synthetic and biological membranes.
New battery technology such as Lithium metal anodes or Li-S cathodes require solid-state electrolytes for enhanced stability. A fundamental challenge is designing solid-state electrolytes with efficient ion transport, as ion diffusion rates are generally many orders of magnitude lower than in comparable liquid electrolytes. Proposed materials that could achieve such performance are porous polymer gel or plastic electrolytes, or alternatively inorganic transition metal-oxide crystals or ceramics. We are particularly interested in poly-iodide containing systems, which exhibit intriguing properties due to the unique chemistry of poly-iodide chains. We utilize ab initio molecular dynamics (AIMD) approaches along with reactive force fields to understand and optimize ion transport in these systems.