Development of Analytical Models for Evaluating the Mechanical and Electrochemical Response of Flexible and Stretchable Lithium Ion Battery Materials




Berg, Sean

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Flexible and stretchable batteries have become a highly active area of research in recent years due to a new demand for mechanically compliant energy storage devices for a wide range of flexible applications including wearable and implantable electronics, touch-screens, and smart technology. Lithium ion batteries are leading candidates for flexible and stretchable energy storage devices due to their high energy density and efficiency. Considerable research has been related to developing flexible and stretchable materials, and solid polymer electrolyte lithium ion batteries show promise, offering many mechanical and safety advantages. While much experimental work has been in the development of these batteries, considerably less analytical modeling and numerical work has been a part of the development, which would elucidate experimental observations and provide enhanced understanding of the materials behavior in these new batteries. The work presented in this dissertation includes results of computational modeling and simulation of the mechanical and electrochemical behavior of flexible and stretchable battery materials under normal operating conditions and applied deformations resulting from mechanical loads. Additionally, analytical multiphysics models in the form of series of differential equations were derived to explain experimental observations of changes in battery performance and material properties due to applied loads and deformations. These models can be used to predict materials behavior and to relate key design parameters of flexible and stretchable batteries. The battery materials and designs that are assessed in this work were developed in our lab. Objectives of this work include understanding relationships between mechanical loading and certain key controllable fabrication parameters such as layer interface contact properties to predict the influence on flexible battery performance, and exploring how deformation occurring in the polymer electrolyte due to an applied mechanical load influences electrochemical performance. The effect of loading on other performance parameters, including battery impedance, is further studied, and all analytical work is compared to experimental data. An important aspect of this development is the consideration of nonlinearity in the models. Novel approaches are taken to include and address nonlinearity within the systems considered. While these models can be simplified through linearization, limitations of linear solutions are also discussed.



Flexible batteries, Batteries, Lithium-ion batteries (LIB), Stretchable lithium ion batteries, Nonlinear modeling


Portions of this document appear in: Kammoun, Mejdi, Sean Berg, and Haleh Ardebili. "Flexible thin-film battery based on graphene-oxide embedded in solid polymer electrolyte." Nanoscale 7, no. 41 (2015): 17516-17522. And in: Kelly, Taylor, Bahar Moradi Ghadi, Sean Berg, and Haleh Ardebili. "In situ study of strain-dependent ion conductivity of stretchable polyethylene oxide electrolyte." Scientific reports 6 (2016): 20128.