Theoretical and Experimental Investigations of Coupled Mechanics and Electrochemistry in Silicon Anodes Lithium Ion Batteries

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The research objective of this award is to understand the fundamentals in coupled mechanics and electrochemistry in lithium (Li)-ion batteries. Silicon is an attractive anode material being closely scrutinized for use in Li-ion batteries because of its highest-known theoretical charge capacity of 4,200 mAh/g. However, the development of silicon anode Li-ion batteries has lagged behind because of their large mechanical deformation, i.e., up to 400 percent volumetric change, during electrochemical reactions, which results in fracture, pulverization and early capacity fading. In other words, this coupled mechanics (e.g., volumetric change) and electrochemistry problem is a bottleneck to the development of silicon anode Li-ion batteries. The objective of this project is to understand the fundamental mechanical properties of the lithiated silicon anodes using combined experimental and theoretical methods. Specific studies will focus on i) nanoindentation experiments to obtain the influence of lithiation on mechanical properties as a function of depth; coupled with ii) continuum modeling to extract the stress-strain curve of lithiated silicon anodes under different state of charges.If successful, the results of this research will help facilitate the fundamental understanding of the coupled mechanics and electrochemistry of silicon anodes in Li-ion batteries, specifically the mechanical behavior of lithiated silicon. The theoretical and experimental methodology can be also applied to other electrodes and materials in Li-ion batteries, such as the cathode. The successful implementation of the proposed research will contribute to a new area of mechanics of materials, namely, coupled mechanics and electrochemistry, which will potentially lead to a range of transformative applications in battery and energy-related fields. The graduate students involved in the research will be trained in a multidisciplinary environment.