An On-Chip, Nanomechanics Platform for Lithium Storage Capacity Measurements in Single Nanowire Electrodes

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The research objective of this award is to develop an experimental technique for directly quantifying the intrinsic lithium storage capacity of an individual nanowire (NW) electrode with attogram-scale precision. A lithium ion battery electrode represents a nanomechanical system in which both the stiffness and mass are modulated dynamically with charging or discharging. These dynamic nanomechanical signatures of the battery electrode will be probed within the experiments. Electrokinetically assembled, on-chip, single-NW electrochemical cells will be fabricated such that the electroactive NW forms a doubly-clamped beam and remains suspended between metallic current collectors. At any given lithiation state, static force vs. deflection measurements using an atomic force microscope will be employed to determine the nanomechanical stiffness of the suspended NW electrode. Furthermore, NW resonance frequency will be measured using in-situ electron microsopy based characterization of electrostatically actuated nanowires. This combination of static force-deflection and in-situ resonance measurements will enable the extraction of its lithiation / de-lithiation induced mass change at any given charge state.This effort would result in a new multiphysics diagnostic capability for energy storage systems based on nanostructured materials and would extend the relevance / capabilities of the mechanics community into electrochemical energy storage research in new directions. The award will entail research collaborations with the Sandia National Laboratories (SNL) and a graduate student from Virginia Commonwealth University will have opportunities to perform a part of his research at SNL. An undergraduate Summer Cadet from the Virginia Military Institute will also participate in a summer project at the PI's lab, as a part of the VCU-VMI research exchange program, and will perform in-situ microscopy experiments. The educational outreach activities will bring advanced microscopy and electrochemical energy storage topics into graduate and undergraduate curricula.