Structural organic battery cathodes comprised of organic redox active polymers, reduced graphene oxide, and aramid nanofibers

Abstract

Structural batteries are increasingly being studied because of their multifunctionality, combining good energy storage and mechanical properties. By storing energy within the object's structural elements, these may lead to substantial mass and volume savings in electrified transportation, cube satellites, and aerospace applications. However, most studies on structural batteries focus on conventional cathode materials such as lithium iron phosphate (LFP), lithium cobalt oxide (LCO), or nickel manganese cobalt oxide (NMC). These metal oxide active materials are challenged by their poor rate capabilities at higher C-rates, poor adhesion to current collectors, and, in some cases, materials supply chain issues. Organic radical polymers are a promising alternative because they exhibit rapid charge transfer at high C-rates, have improved adhesion, and are sourced from earth-abundant elements. In this work, structural battery cathodes using the redox-active polymer PTMA (poly(2,2,6,6-tetramethyl-piperidenyloxyl-4-yl methacrylate)) as the electrochemically active material are examined. PTMA-based slurries are thermally crosslinked to inhibit PTMA's dissolution on a structural current collector comprised of mechanically strong reduced graphene oxide (rGO) nanosheets and branched aramid nanofibers (BANFs). High rate capabilities at 25C-rate are observed owing to the fast redox reaction kinetics of PTMA, which led to an excellent specific power of 4310 W kg⁻¹, which is higher than other commercial and structural electrodes. The structural electrode's specific modulus (4.33 GPa cm³ g⁻¹) was superior to that of other commercial systems. Importantly, the PTMA-based active material did not delaminate from the structural electrode during cycling. This investigation focuses on developing structural organic battery electrodes that possess superior mechanical strength while not compromising on electrochemical performance. This work provides a pathway for utilizing earth-available, redox-active polymers as active materials in fast-charging, structural batteries.