UCLA

As the global demand for energy continues to rise, cost effective and energy dense rechargeable battery systems have become increasingly desirable. This dissertation focuses on the synthesis of high-energy density alloy anode nanomaterials and characterization utilizing synchrotron X-ray sources for lithium- and sodium-ion batteries (LIBs/SIBs). Alloy anodes form atomic-scale mixtures with Li/Na, accompanied by multi-electron redox, providing drastically higher energy densities (phosphorous=2596 mAh/g), compared to commercial graphite anodes (372 mAh/g). Unfortunately, to accommodate so much Li/Na, the primary particles volume must expand, leading to particle pulverization and rapid capacity decay. To mitigate these effects, here, nanoporous architectures and nanocomposites were used to improve high-capacity long-term cycling.This thesis first details the synthesis of nanoporous Sb (NP-Sb) and characterizes the electro-chemo-mechanical behavior when cycled with Li and Na utilizing operando X-ray diffraction (XRD) and transmission X-ray microscopy (TXM). NP-Sb cycled against Li transitions through crystalline phase intermediates, resulting in crack formation; NP-Sb cycled against Na transitions through amorphous phase intermediates, and shows ductile behavior and crack self-healing. To visualize these structure changes, a cost-effective operando single particle nanotomography electrochemical cell was developed to follow volume expansion or crack formation in 3D. Utilizing this cell, operando nanotomographic reconstructions for a variety of battery materials were obtained. For example, NPSb cycled with Na undergoes massive, but reversible, anisotropic expansion. A bimetallic nanoporous SbSn alloy (NP-SbSn) with variable porosity was then examined. Operando XRD and TXM indicate that the nanotruss architectures in highly-porous samples mitigate the formation of cracks and enable reversible long-term, high-capacity cycling as LIBs. TXM tomography using AI-assisted segmentation on optimized NP-SbSn materials allow for quantification of the mechanism responsible for mitigation of volume expansion and strain dissipation.To make more economically-viable high-capacity SIB anodes, laser-scribed phosphorous/graphene oxide (GO) nanocomposites were synthesized. Utilizing synchrotron soft- and tender-X-ray absorption spectroscopy (XAS), the nanocomposites were shown to have a stratified nanoscale architecture, which enhance long-term high-capacity cycling in SIBs. Lastly, the synthesis and electrochemical performance of a phosphorous/GO nanocomposite anode with exceptional electrochemical performance over hundreds of cycles is described. High-capacity full cells were achieved by coupling these anodes to several SIB cathodes.