(475d) Composite Battery Electrodes Derived From Bijels

Mohraz, A., University of California
Witt, J. A., University of California, Irvine
Mumm, D. R., University of California

High energy density and rapid charge and discharge rates are important characteristics in state of the art battery systems. In order to enhance these performance characteristics, the kinetics of ion and electron transport in the electrodes must be improved while maintaining a large volume fraction of electrolytically active materials for energy storage. In this regard, the idealized electrode microstructure has been envisioned as a three-dimensional arrangement of interpenetrating domains that allow for large interfacial contact between the constituent phases and low-resistance paths for ion and electron transport. Here we report a novel technique to produce this unique morphology using a soft matter template derived from bicontinuous interfacially jammed emulsion gels (bijels). These non-equilibrium soft materials inherently have a bicontinuous microstructure, where interpenetrating domains of two immiscible fluids are kinetically trapped through interfacial jamming of colloidal particles during spinodal decomposition. The characteristic size of the fluid domains, which determines the interfacial contact area between the phases, is controlled solely through the overall colloid volume fraction. Further, chemical processing of bijels allows for subsequent tuning of the length scale for ion diffusion through the intercalation matrix.  Therefore, the salient morphological parameters that govern electrode capacity and power density can be independently tailored. We provide examples of composite electrodes that we have synthesized through this route, demonstrate their salient electrochemical characteristics, and discuss how the unique morphology of bijel-derived composites can lead to superior electrochemical performance in these systems.