2, Vanderbilt University, Nashville, Tennessee, United States
3, Bar-Ilan University, Ramat-Gan, , Israel
Multifunctional structural materials have the potential to replace existing structural materials in systems, such as in electric vehicles, with dual-functioning structural and energy-dense storage media that can reduce dependence on externally situated batteries or supercapacitors. A critical challenge remains in the design of interfaces that dually store energy and maintain composite mechanical integrity under load. Here I will discuss our recent efforts in this area starting with the growth of carbon nanotubes on lightweight metal 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. These composites showcase high power densities of 10 kWh/kg and comparable energy densities of 20 Wh/kg. 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. Overall, these results forge a path toward practical multifunctional composites by combining (1) in-situ mechano-electrochemical testing to assess structural energy storage performance, (2) carbon nanotubes to reinforce and prevent failure at structural interfaces, and (3) redox-active materials processed to augment energy density.