SUMMARY

Aluminum is an attractive candidate for replacing graphite anodes in lithium-ion batteries because of its high specific capacity and the potential for foils to remove slurry processing. However, achieving reversible reaction of aluminum is challenging due to volume changes, solid-electrolyte interphase (SEI) formation, and sluggish ion transport. The first objective of this proposal seeks to understand how different foils (99.999% Al and Al alloy 8111) behave electrochemically during galvanostatic cycling. Both foil compositions exhibited a power-law dependence between cycle life and the extent of reaction per cycle. This relationship was termed “electrochemical fatigue,” as inspired by mechanical fatigue processes. Alloy composition also affected the Coulombic efficiency (CE) in the first cycles, with high-purity foils exhibited higher initial CE compared to Al alloy. Operando optical microscopy revealed different spatiotemporal reaction mechanisms, which explains how lithium trapping potentially affects the observed CE behavior.

The second objective focuses on how chemo-mechanical degradation depends on composition, microstructure, areal capacity per cycle, and stack pressure for aluminum anodes. Commercial foils containing different alloying elements will be cycled under various areal capacities and stack pressure conditions, then characterized ex situ. Electron backscatter diffraction (EBSD) will be used to understand the microstructures of these foils in the pristine state and after cycling, and energy dispersive spectroscopy (EDS) will help visualize the evolution of morphology for different foil phases. Electrochemical impedance spectroscopy (EIS) will be used to track the impedance evolution which may cause cell failure. The final objective investigates how lithium trapping within aluminum can be controlled by varying the foil composition, microstructure, areal capacity, and pressure for both liquid and solid-state cells. Ex situ backscattering electron (BSE) imaging will help visualize the lithiated/delithiated phases. Galvanostatic Intermittent Titration Technique (GITT) will be a critical tool in quantifying lithium diffusivity of the overall foils. Improving our understanding about how aluminum behaves in batteries, both electrochemically and chemo-mechanically, paves the way for the rational design of metal foil anodes with enhanced stability and performance.

Teams Meeting ID: 245 749 891 012
Passcode: Vd99hZ