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，用于直接量化单个纳米线（NW）电极的固有锂存储容量，并具有attogram-scale精度。锂离子电池电极代表了一种纳米机械系统，其中刚度和质量都随着充电或放电而动态调制。电池电极的这些动态纳米机械特征将在实验中进行探测。将制造动电组装的片上单NW电化学电池，使得电活性NW形成双夹持梁并保持悬浮在金属集流体之间。在任何给定的锂化状态下，将采用使用原子力显微镜的静态力与偏转测量来确定悬浮NW电极的纳米机械刚度。此外，NW共振频率将使用基于静电驱动纳米线的表征的原位电子显微镜来测量。这种静态力偏转和原位共振测量的组合将使其在任何给定的充电状态下的锂化/脱锂引起的质量变化的提取成为可能，这一努力将导致基于纳米结构材料的能量存储系统的新的多物理诊断能力，并将力学界的相关性/能力扩展到新的方向的电化学能量存储研究。该奖项将涉及与桑迪亚国家实验室（SNL）的研究合作，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。来自弗吉尼亚军事学院的一名本科生暑期学员也将参加PI实验室的一个暑期项目，作为VCU-VMI研究交流计划的一部分，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储能主题纳入研究生和本科生课程。

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.