Towards Structural Batteries Enabled By Fiber Reinforced Composites

Abstract

The advent of electric automobiles has garnered great interest in multifunctional electrochemical energy storage architectures which have the potential to store and release energy on demand while simultaneously being subjected to static or dynamic load conditions. At the forefront of these technologies are energy storage integrated fiber reinforced composites which promise substantial benefits to both mechanical as well as electrochemical performance. In this context, the design of interfaces that dually store energy and maintain composite mechanical integrity under load is of critical importance. Here, I will illustrate our systematic efforts on the development of multifunctional structural energy storage composites starting with CNTs grown on lightweight stainless steel meshes and incorporation of these materials into energy storing composite laminates where we simultaneously test mechanical and electrochemical performance. To further augment the energy storing capability of the carbon nanotubes, we electro-deposit ultrafast redox active pseudocapacitive nickel oxide and iron oxide onto the CNTs to fabricate fiber reinforced nickel-iron asymmetric redox pseudocapacitiors or nickel-iron ‘ultra-battery’ composites. Overall, composites showcase high power densities of 10 kWh/kgActive and comparable energy densities of 20 Wh/kgActive. Furthermore, these multifunctional composites demonstrate good mechanical (tensile, flexural and load impact) behavior while simultaneously exhibiting stable charge/discharge performance during in-situ mechano-electrochemical measurements. These results thus forge a path toward practical multifunctional composites by combining (1) in-situ mechano-electrochemical testing to assess structural energy storage performance, (2) effective reinforcements and prevent failure at structural interfaces, and (3) redox-active materials processed to augment energy density. Overall, these results provide new insights and creates a framework for developing such multifunctional energy storage architectures for a multitude of load-bearing applications.