MEAM Ph.D. Thesis Defense: “Transport Modeling and Design of Electrode Architectures for High Energy Density Batteries”

With the ever-increasing production of portable electronics, internet of things devices, electric vehicles, unmanned aerial vehicles, and other autonomous robotic systems comes an increasing demand for reliable, long-lasting, portable power sources. Portable electronic systems are often limited by the energy density of the batteries that power them, and these batteries typically take up a large fraction of the overall device weight and volume. Higher energy density batteries are needed to effectively power current and future devices.

One strategy for increasing energy density is to increase the volume fraction of active materials in the battery by increasing the thickness and decreasing the porosity of the electrodes. However, existing electrode architectures cannot simultaneously enable thick, high-density electrodes because electrolyte pathways are necessary for ion transport. Creating high solid volume fraction electrodes requires new electrode architectures which enable ion transport even when electrolyte volume is limited.

To achieve high energy, most battery research focuses on making packaged batteries as small or as light as possible, irrespective of the systems that such batteries will power. In biology, multifunctional interconnected subsystems work together to create a more efficient full system. Incorporating multifunctionality into energy storage for robotics will lead to similar improvements in system-level efficiency.

This work demonstrates multiple approaches toward electrode architecture design for high energy density batteries. First, we demonstrate how continuous electrode architectures enabled by the electrodeposition of lithium cobalt oxide (LCO) can overcome electrolyte transport limitations via fast solid-state diffusion. These electrodeposited LCO cathodes create a large opportunity space for improved energy density by enabling thick, high solid volume fraction electrodes. We also present a novel catholyte architecture with the ability to store and extract energy from dissolved oxygen in silicone oil emulsions. This electrolyte is a promising candidate for multifunctional power systems and presents new design opportunities for flow batteries by removing the need for the challenging gas-liquid-solid interfaces and semi-open boundaries in conventional oxygen reduction reaction (ORR) cathodes.