Multifunctional Energy Storage Composites: Design, Fabrication, and Experimental Characterization

We propose the concept of Multifunctional-Energy-Storage Composites (MES Composites) which highlights a unique integration technique for embedding lithium-ion battery materials in structural carbon-fiber-reinforced-polymers (CFRP). Unlike standard lithium-ion pouch cells, the MES Composites maximizes material utilization by using CFRP facesheets to house the electrochemistry. Through-thickness polymer reinforcements are implemented to allow load transfer between the two facesheets, analogous to the sandwich structure construction. In this work, the design rationale, materials and fabrication techniques, experimental evaluation, and performance of the first-generation MES Composites will be presented. MES Composite cells with a nominal capacity of approximately 4 Ah, with various reinforcements-array configurations, were fabricated and first tested through a series of electrochemical reference performance tests (RPT) under a strain-free condition. The MES Composite cells then underwent a mechanical-electrical-coupling test, where a quasi-static three-point-bending load was applied at increasing increments. Mechanical testing was interrupted after each increment to perform a sequential RPT to quantify any non-catastrophic degradation in the electrochemical performance. The obtained results verify the feasibility of the concept showing that the electrochemical performance of the MES Composites can be maintained at the same level as the regular lithium-ion battery. The reinforcement architecture of the MES Composite constrains the relative motion of the battery electrodes and increases the bending rigidity, resulting in a higher load carrying capacity and inhibiting non-fatal injury of the cell under mechanical loads. This multifunctional material system can also be scaled up and ultimately provide considerable weight and volume saving at the system level.