Showing papers by "Matt Pharr published in 2014"
TL;DR: In this paper, a model of concurrent lithiation and rate-sensitive plasticity is developed for amorphous LixSi thin films, and the results have direct ramifications concerning the rate-capabilities of silicon electrodes: faster charging rates (i.e., strain rates) result in larger stresses and hence larger driving forces for fracture.
102 citations
TL;DR: In this article, the microstructural changes in {100} and {110} oriented silicon wafers during initial lithiation under relatively high current densities were observed, showing that the formation of such structures is energetically unfavorable in the absence of defects due to the large hydrostatic stresses that develop.
34 citations
Dissertation•
06 Jun 2014
TL;DR: In this paper, the authors examined the mechanical behavior of microelectronic devices and lithium-ion batteries and investigated the interplay between mass transport, deformation, stress, and fracture in lithium ion battery electrodes.
Abstract: This thesis explores mechanical behavior of microelectronic devices and lithium-ion batteries. We first examine electromigration-induced void formation in solder bumps by constructing a theory that couples electromigration and creep. The theory can predict the critical current density below which voids do not form. Due to the effects of creep, this quantity is found to be independent of the solder size and decrease exponentially with increasing temperature, different from existing theories. We then investigate the interplay between mass transport, deformation, stress, and fracture in lithium-ion battery electrodes. First, we model fracture of elastic electrodes by combining ideas from diffusion kinetics and fracture mechanics. Next, we examine mechanics of high-capacity lithium-ion batteries, which demonstrate inelastic deformation, by constructing a model that accounts for diffusion and elastic-plastic deformation. These models suggest that fracture is prevented in small and soft electrode materials that are cycled slowly. To investigate crystalline silicon electrodes, we construct a continuum model of concurrent reaction-controlled kinetics and plasticity. To quantify the kinetics of
6 citations