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

该奖项的研究目标是开发一种实验技术，以阿图克级精度直接量化单个纳米线（NW）电极的固有锂存储容量。锂离子电池电极是一个刚度和质量随充放电动态调制的纳米力学系统。这些电池电极的动态纳米力学特征将在实验中进行探讨。通过电动力组装的片上单NW电化学电池将被制造出来，使电活性NW形成双夹紧的光束，并悬浮在金属集流器之间。在任何给定的锂化状态下，使用原子力显微镜进行静力与偏转测量，以确定悬浮NW电极的纳米机械刚度。此外，将使用基于静电驱动纳米线的原位电子显微镜表征来测量NW共振频率。这种静力偏转和原位共振测量的结合将能够在任何给定的电荷状态下提取其锂化/去锂化引起的质量变化。这项工作将为基于纳米结构材料的储能系统带来一种新的多物理场诊断能力，并将力学领域的相关性/能力扩展到电化学储能研究的新方向。该奖项将与桑迪亚国家实验室（SNL）进行研究合作，来自弗吉尼亚联邦大学的一名研究生将有机会在SNL进行部分研究。作为VCU-VMI研究交流计划的一部分，来自弗吉尼亚军事学院的一名本科暑期学员也将参加PI实验室的一个暑期项目，并将进行原位显微镜实验。教育推广活动将把先进的显微镜和电化学能量存储主题纳入研究生和本科课程。

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.