Composite Silicon Anodes for Energy Storage, Sensing, and Actuation in Multifunctional Lithium Ion Devices

该项目探索了用于多功能锂离子(Li-ion)设备的复合硅阳极的潜力。锂离子电池广泛应用于高功率和高能量密度的应用，如电动汽车、手机、笔记本电脑和无人机。硅阳极有望提供更高的电化学能量密度，但它们的使用因硅在完全锂化时经历的高体积膨胀而变得复杂。此外，硅阳极锂离子电池的开路电压对机械应力高度敏感。该项目将利用这些效应来创造能够集成能量存储、机械驱动以及惯性、振动和化学传感的新型多功能结构。这类新型设备的基本功能和权衡将通过建模、设计优化和实验测试来确定。项目成果将对各种技术产生广泛影响，包括医用微型机器人、可穿戴电子设备和电动汽车。一个由研究生和本科生组成的不同的研究团队将在基础研究任务以及翻译工程研讨会上共同努力，学习将基础研究转化为商业产品和系统的关键技能。该项目通过理论、实验和器件设计研究，寻求对锂化硅复合结构的电化学和机械耦合动力学的基本理解。将结合电化学和力学的基本方程来预测这些活动结构所提供的位移和力。控制偏微分方程将通过可支持的工程假设、线性化和模型降阶来简化，以产生数值高效的模型，从而对潜在的物理和化学有深刻的理解。这些模型将依次用于设计复合阳极的化学、形貌和介观结构，包括硅、粘结剂和导电添加剂，以探索电气和机械功率之间的帕累托前沿。第一次，与硅复合材料锂化相关的大体积变化将被利用来创建在充电和放电时以所需方式移动的致动结构。此外，松树-卡恩电势还将首次被用于制造能够自我感应其应力状态的电池。从新的第一性原理模型和一个概念的介观结构出发，简化了完整的控制方程，以有效和准确地基于施加的负载和电流输入来预测输出电压。化学成分、形态和结构将发生变化，以研究能量存储和对外加负载的敏感性之间的权衡。新的驱动和自感知储能结构将与标准阴极和电解液配对，并对电气、机械和传感器性能进行测试。该项目的结果将被封装在第一原理模型中，该模型将根据电压、电流、位移和施加的负载的测量进行实验验证。

This project explores the potential of composite silicon anodes for multifunctional lithium ion (Li-ion) based devices. Li-ion batteries are widely used for high power and energy density applications, such as electric vehicles, cell phones, laptop computers, and unmanned aerial vehicles. Silicon anodes promise even higher electrochemical energy densities, but their use is complicated by the high volumetric expansion that silicon undergoes when fully lithiated. Furthermore, open-circuit voltage in Li-ion cells with silicon anodes is highly sensitive to mechanical stress. This project will harness these effects to create novel multifunctional structures capable of integrated energy storage, mechanical actuation, and inertial, vibration, and chemical sensing. The fundamental capabilities and trade-offs of this new and novel class of devices will be characterized through modeling, design optimization, and experimental testing. Project outcomes will have broad impacts on a variety of technologies, including medical microrobots, wearable electronic devices, and electric vehicles. A diverse research team of graduate and undergraduate students will work together on fundamental research tasks, as well as in translational engineering workshops to learn skills crucial to converting fundamental research into commercial products and systems.This project seeks a fundamental understanding of the coupled electrochemical and mechanical dynamics of lithiated Si composite structures, through theoretical, experimental, and device design research. Fundamental equations of electrochemistry and mechanics will be combined to predict the displacement and force provided by these active structures. The governing partial differential equations will be simplified via supportable engineering assumptions, linearization, and model order reduction, to produce numerically efficient models providing an insightful understanding of the underlying physics and chemistry. These models will be used in turn to design the chemistry, morphology, and mesoscale structure of composite anodes, including the Si, binder, and conductive additives, to explore the Pareto frontier between electrical and mechanical power. For the first time, the large volume change associated with lithiation of Si composites will be harnessed to create actuated structures that move in a desired fashion when charged and discharged. Also for the first time, the Larché-Cahn potential will be used to make batteries that self-sense their stress state. Starting from novel, first principle models and a notional mesostructure, the full governing equations will be simplified to efficiently and accurately predict output voltage based on applied loads and electrical current input. Chemical composition, morphology, and structure will be varied to study the tradeoff between energy storage and sensitivity to applied loads. The new actuating and self-sensing energy storage structures will be paired with standard cathodes and electrolytes, and tested for electrical, mechanical, and sensor performance. The results of the project will be encapsulated in first-principles models, which will be experimentally validated against measurements of voltage, current, displacement, and applied load.