Electronic and mechanical scanning-probe based characterization of multi-phase composite silicon anodes for lithium-ion batteries
Huey, Zoey
Huey, Zoey
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2024
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2025-11-26
Abstract
Silicon anodes for lithium ion batteries offer promising improvements in energy density due to their high theoretical capacity. However, silicon undergoes a large volumetric expansion when it lithiates, resulting in mechanical damage that renders active material electrically isolated and results in an unstable solid electrolyte interphase (SEI), which then causes unwanted electrolyte reduction. These issues contribute to poor cycling in silicon anodes. Many approaches are utilized to mitigate the problems resulting from silicon’s expansion, including alloyed materials, coatings on the silicon, modified processing steps, and composite, multiphase electrodes. The results in this thesis demonstrate electrical and mechanical measurements on several different silicon electrode systems to explore and characterize the microstructure, phase distribution, mechanical property, and electrical property changes that accompany different mitigation strategies. The techniques used—scanning spreading resistance microscopy (SSRM) and contact resonance/force volume force microscopy (CR-FV)—are scanning probe-based techniques that are both powerful and underutilized for composite electrode research. This work demonstrates the use of SSRM to: (i) study the SEI, (ii) understand how thermal processing impacts electrode resistivity, (iii) identify individual components of electrodes and analyze their distribution, and (iv) study how the binder used in the electrode is impacted by cycling. The use of CR-FV to study composite electrodes is also demonstrated for the first time, providing previously unrealized insight into mechanical changes based on morphology and cycling in composite silicon anodes.
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