A new energy-based multifunctional efficiency (MFE) metric is developed using micromechanics solutions for structural supercapacitors consisting of composite electrodes that can store electrical energy and sustain mechanical loads. MFE metrics quantify the volume and/or mass savings when structural and functional materials are replaced by multifunctional materials and evaluate the trade-off between different functionalities. Commonly used multifunctionality metrics for structural supercapacitors are based on the rule of mixtures for both mechanical and electrical performance. These metrics provide an adequate approximation for some electrode geometries and loading conditions, such as longitudinal direction for aligned fibers in multifunctional composite electrodes and in-plane directions for laminate composite electrodes. However, if supercapacitors with complex microstructure or multiple electrode materials encompass more complex geometries or orientations of the structural and functional phases, a more comprehensive method is required to accurately capture the MFE. The MFE proposed herein can account for complex geometries and different mechanical loading conditions by using micromechanics methods. The shapes considered here include layered composite supercapacitors, fibrous films and any shape that can be derived from an ellipsoid. When calculated utilizing the proposed metric, the MFE varies by orders of magnitude due to the difference in shapes and applied mechanical fields to the supercapacitors, while existing metrics provide a constant upper bound. The influence of Young’s modulus difference between multifunctional electrodes and solid electrolytes is also discussed.

使用微机械解决方案开发了一种新的基于能量的多功能效率（MFE）指标，该解决方案用于结构超级电容器，该超级电容器由可存储电能并承受机械负载的复合电极组成。当用多功能材料代替结构材料和功能材料时，MFE指标可量化节省的体积和/或质量，并评估不同功能之间的权衡。结构超级电容器的常用多功能度量基于机械和电气性能的混合规则。这些度量为某些电极的几何形状和负载条件提供了足够的近似值，例如多功能复合电极中对齐纤维的纵向和层压复合电极的面内方向。然而，如果具有复杂微结构或多种电极材料的超级电容器包含结构和功能相的更复杂的几何形状或方向，则需要一种更全面的方法来准确捕获MFE。本文提出的MFE可通过使用微力学方法解决复杂的几何形状和不同的机械负载条件。这里考虑的形状包括层状复合超级电容器，纤维膜以及可以从椭球体衍生的任何形状。当使用提议的度量进行计算时，由于形状和向超级电容器施加的机械场的差异，MFE会以数量级变化，而现有度量则提供恒定的上限。