Committee:

Matthew McDowell, MSE/ME (advisor)

Christopher Muhlstein, MSE

Seung Woo Lee, ME

Naresh Thadhani, MSE

Meilin Liu, MSE

Abstract:

The development and optimization of anode materials for solid-state batteries (SSBs) are essential to advancing the performance and reliability of energy storage systems, especially since the current use of graphite as an anode material limits fast charge capability and energy density of current battery technologies. SSBs, distinguished from their liquid electrolyte-based lithium-ion battery (LIB) counterparts, offer the possibly of safer, higher energy density, and more durable battery architectures. SSBs could also enable the use of novel anode materials capable of addressing the inherent limitations of conventional LIBs, such as the mechanical degradation of anode materials over repeated cycling. Specifically, aluminum foil alloys, particularly when engineered with specific microstructural modifications, emerge as promising candidates for SSB anodes.

Aluminum foil alloys, despite their attractive theoretical properties, face significant challenges within traditional LIBs that utilize liquid electrolytes. The volumetric expansion of aluminum during lithiation exacerbates these effects, leading to mechanical degradation and solid-electrolyte interphase (SEI) growth on the anode. SSBs, by virtue of their solid electrolytes, offer a fundamentally different operational environment compared to LIBs, which allows aluminum foil alloys to overcome the limitations encountered in liquid systems. In particular, the solid electrolytes in SSBs contribute to improved interfacial stability. This stability is critical for maintaining consistent ionic conductivity and mechanical integrity, even in the face of the volumetric changes that occur during battery operation. The solid-state architecture thus provides a unique opportunity to leverage the beneficial properties of aluminum and its alloys, which would otherwise be untenable in a liquid electrolyte environment.

Here, I demonstrate that the integration of indium phases into aluminum foil alloys can enable anodes that operate in SSBs with high capacity, good capacity retention, and fast diffusion kinetics. Using cryogenic focused ion beam scanning electron microscopy and X-ray diffraction analysis, I trace the evolution of aluminum-indium foil microstructure and provide insights into the underlying mechanisms of performance enhancement. The unique multiphase microstructure of aluminum-indium alloys, characterized by the distributed LiIn network within a dense aluminum matrix, significantly enhances cycling stability and electrochemical performance. This microstructural design mitigates lithium trapping and facilitates uniform stress distribution during the alloying and dealloying processes, effectively addressing the key limitations of using commercial-grade aluminum in energy storage applications. The role of indium in promoting a more efficient Li-Al reaction with minimal overpotential, while also mitigating the detrimental effects of volumetric expansion, underscores the importance of microstructural optimization in developing viable anode materials for SSBs. These advancements in aluminum foil alloy anodes through microstructural engineering mark a step towards the realization of high-performance SSBs.