(6g) Rationally Designed and Deterministically Engineered Electrodes for High-Performance Energy Storage Applications

Over the past two decades, the widespread miniaturization of portable electronic devices has led to the need for similarly scaled energy storage systems. However, the energy storage technology has not improved at the same rapid pace as the portable electronics technology, resulting in limited operation duration of the device on a single charge. The vast majority of the energy storage systems utilized in the portable electronic devices consist of batteries. Considering the currently available battery chemistries, a drastic improvement in the battery performance in terms of capacity is not expected in the near future. Unless a completely new battery chemistry with an extremely high energy density is developed, the only way to achieve longer operation times is through increasing the mass of the active material present within the battery, which would be incompatible with the current shrinking trend of the portable electronics. However, improvements can be achieved in the rate of the energy transfer, i.e. power density, which these batteries can deliver. A battery that can be charged very rapidly would still be quite desirable even if it possesses a relatively low energy density.

The batteries with rapid charge and discharge capabilities can only be realized via simultaneous minimization of certain inherent resistances encountered during the transport of the ionic and electronic species. There are both intrinsic and extrinsic factors affecting the transportation process of ions and electrons. Intrinsic factors, such as diffusivity and conductivity of the battery components, depend on the choice of materials to be utilized within the system. Extrinsic factors, including the surface area, diffusion and conduction path lengths, on the other hand, primarily rely on the size, dimension, and geometry of the system components.

The focus of our research has been on the realization of rationally designed and deterministically engineered three-dimensional electrodes with precisely controlled dimensions that address the aforementioned critical extrinsic factors determining the ultimate performance of the battery. MEMS technologies and electrochemical techniques have been utilized for the fabrication as well as characterization of these scalable, well-ordered, and high-surface-area electrodes with rapid charge and discharge capabilities. Utilization of micro- and nanofabrication techniques also enables the realization of electrodes for high-performance power sources for a wide variety of applications, ranging from autonomous microsystems to macroscale portable electronics. The resultant electrodes demonstrate an improved performance in not only batteries, but also other energy storage systems, such as capacitors and supercapacitors.