S4E5

Abstract

Mechanics and chemistry are intimately coupled in rechargeable batteries. Their interplay regulates the structural stability and kinetics of the electrodes and ultimately manifests in the battery's capacity retention and power density. However, characterizing the chemo-mechanical interplay in these systems is complicated by the small characteristic size, dynamic composition, and environmental sensitivity of the electrode materials. Considering these circumstances, we introduce the first operando nanoindentation platform for locally probing battery materials during controlled electrochemical reactions in an inert atmosphere. We expand the capabilities of this powerful tool and present a new mechanics-based technique for composition profiling. This method allows for tracking the spatiotemporal evolution of concentration fields and deconvoluting the role of stress gradients on diffusion. We apply this method to probe amorphous silicon electrodes in Li-ion batteries and answer long-debated questions about the origin of their sharp reaction front, asymmetric rate-capability, and Li trapping behavior. The framework brings about insights on fundamental mechanisms of chemomechanics and advises on battery design and operation.

Introduction of speaker

Dr. Luize Vasconcelos is a Postdoctoral fellow in the Department of Aerospace Engineering and Engineering Mechanics at the University of Texas at Austin. She holds Ph.D. and M.Sc. degrees in Mechanical Engineering from Purdue University - West Lafayette, USA. Her research interests center on the mechanics of functional materials for energy storage and flexible electronics. She is currently working on advanced materials and additive manufacturing techniques for the direct-write of flexible electronics on human skin.

Abstract

Electroactive polymers (EAPs) are promising materials for applications in energy harvesting, advanced prosthetics, wearable sensors and electronics, and soft, biologically-inspired robotics. However, many EAPs are limited by weak electromechanical coupling, which results in poor performance for the aforementioned applications. Here, we utilize statistical mechanics and polymer network theory to develop atomic-to-continuum scale models of electroactive polymers. The multiscale models allow us to connect the performance of these materials to many of their features across length scales such as their molecular-scale properties, cross-linking densities, and overall polymer network architectures. As a result, we discover concrete ways to design and manufacture new materials which outperform their standard counterparts. Specifically, we inform the design of 1) dielectric networks with enhanced actuation, 2) elastomer networks for piezoelectricity and 3) networks with enhanced flexoelectricity. We conclude by outlining a newly developed Monte Carlo method for simulating multifunctional polymers with nontrivial monomer-monomer interactions. The Monte Carlo algorithm has implications for understanding phase transitions and phase transition assisted actuation; and, more broadly, this work aims to inform the design of soft multifunctional materials with new properties and behaviors.

Introduction of speaker

Dr. Matthew Grasinger is currently a postdoc at the Air Force Research Laboratory. He received his Ph.D. in Computational Mechanics at Carnegie Mellon University in 2019. At Carnegie Mellon, he worked on the multiscale modeling and design of electroactive polymers. His current research is on mapping the multistabilities and branches of folding motion in morphing origami structures. More broadly, his interests lie in how collective behavior emerges from, and can be designed from, altering properties and interactions at smaller scales -- namely thermodynamics. This broader concept is particularly relevant to the paradigms of material design and the evolution of biological/natural systems.