Structural electrochemical composites, which are capable of carrying mechanical loads while simultaneously storing or releasing electrical energy, combine the components and behaviors of conventional polymer composite structures and electrochemical devices such as batteries and supercapacitors into a single multifunctional material. In order to analyze these systems more rigorously, this paper derives relationships and metrics for the mass savings of a multifunctional design relative to a design consisting of conventional structures and electrochemical devices. These metrics are then evaluated using structural supercapacitors composed of carbon fiber electrodes and conductive solid polymer electrolytes, as well as multifunctional supercapacitors from literature. The analysis reveals that state-of-the-art multifunctional supercapacitors are still far from reaching the levels of performance needed to supplant conventional structures and save system mass. The metrics provide further insight regarding multifunctional value of the material components as well as influence of various functionalities on system performance.
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