An electrochemical system such as a rechargeable battery or a fuel cell relies on a chain of kinetic and transport processes, which occur and interact across many scales of size and distance. Our research program centers on electrochemical engineering, with an emphasis on the technological problems associated with energy storage and production. We aim to connect the microscopic perspective of the physical chemist with the macroscopic view of the device engineer.
Typical lithium-ion batteries convert chemical energy to electrical energy through reactions that insert or remove lithium from the crystal lattices of porous solids to induce electron exchange. The overall charge/discharge behavior of a battery cell depends on the crystal structure of the solid insertion compounds involved (angstrom scale), on lithium diffusion and intercalation through aggregated solid domains (nanometer scale), and on ionic conduction within electrode pores and the separator membrane (micrometer scale). These interdependent processes may also be accompanied by undesired side reactions, mechanical forces, and heat generation, all of which may degrade performance of the battery as a whole. Thus one of our current research thrusts is to build models that rationalize electrode instability, internal heat transfer, and material degradation in rechargeable lithium-ion or lithium-anode batteries.
Polymer-electrolyte or solid-oxide fuel cells involve similarly coupled processes, in which the flows of heat, electrical current, and mass occur simultaneously, and can impact each other on multiple scales and in various ways. The development of more sophisticated models for electrochemical systems mandates a parallel development of new theoretical methods, both to provide adequate predictive capability and to supply means by which material properties can be assessed without prohibitively large numbers of experiments. Another research thrust of our group is to extend techniques in the statistical mechanics of transport processes, which may allow macroscopic transport or thermodynamic properties to be deduced from molecular simulations.