Date of Award
Doctor of Philosophy (PhD)
Mechanical and Aerospace Engineering
George J. Nelson
Lithium ion batteries., Electrodes., Storage batteries--Design and construction.
The further development of the lithium-ion battery (LIB) for transportation applications requires increased energy density paired with the capability for fast charging. This development needs to keep pace with the increasing market share projection for electric vehicles. New generation electrodes that can increase the cell energy density and capacity, have been studied and developed throughout the past years by changing active materials and microstructural geometries. These new materials present a range of challenges covering areas of performance, reliability, and sustainability. Among these challenges, battery degradation limits the performance and reliability of current LIBs. Furthermore, degradation may hinder development of batteries that support development of a more sustainable and equitable global energy infrastructure. The following study will connect morphological and chemical changes within higher capacity LIB electrodes’ microstructure while cycled under different cut-off voltage and operating temperatures. To correlate these factors with the electrode degradation a combined set of electrochemical, ex situ and in operando imaging characterization techniques are applied. Ex situ techniques include, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray absorption near edge structure (XANES) nanotomography, while in operando data taken while cycling the batteries were acquired using 2D XANES imaging techniques. Results of three studies are presented based on these methods. The effects of non-uniform temperature distribution on commercial stack degradation were assessed. Increased non-uniform growth of the anode solid electrolyte interphase contributed excessive formation of lithium deposits. Studies of Cu6Sn5 alloy anodes, performed using X-ray tomography and nanoscale 2D XANES, reveal material volume expansion, fracture, and dissolution as key failure mechanisms. Finally, degradation of low cobalt cathodes was assessed under different cut-off voltage and operating temperatures. Higher cycling temperature was found to accelerate degradation related to rock-salt phase formation and cathode material dissolution. In all cases, degradation of battery performance reveals evolution of both active materials and the supporting phases of the composite electrodes. Further understanding of electrode degradation mechanisms will enable design of better LIBs to advance cleaner energy storage technologies to reduce our dependence on fossil fuel.
Malabet, Hernando Jesus Gonzalez, "Multimodal characterization of degradation in lithium-ion battery electrodes" (2021). Dissertations. 226.