PTMA coated carbon fibers - Characterization and development toward high power structural battery positive electrode

Abstract

Traditional batteries are often seen as structural parasites: they add weight without contributing to structural strength. Structural batteries represent a new generation of energy storage that actively reinforces structures while carrying both electrical and mechanical loads, creating multifunctional composites. However, most multifunctional composite batteries rely on lithium-based chemistries, which are inadequate for future demands in safety, sustainability, and performance. To address these limitations, this thesis develops carbon fibers coated with poly (2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA), an organic free radical polymer as a lithium-free alternative for next-generation structural batteries. To investigate this approach, PTMA was synthesized and coated onto carbon fibers using optimized polymerization techniques. Electrochemical performance was evaluated via half-cell voltammetry and cycling testing, while microstructural analyses (SEM, FTIR, 1H NMR and 13C NMR) assessed coating quality and stability. The systematic evaluation of carbon fiber electrodes with varying PTMA content (30-60 wt%) yielded promising results. Spectroscopic analysis confirmed successful PTMA synthesis and nitroxide radical formation. Cyclic voltammetry revealed that formulation F1 (30% PTMA) achieved optimal electrochemical reversibility with ∆Ep = 59 mV, meeting theoretical criteria for reversible one-electron transfer. High-loading formulations demonstrated near-reversible behavior with ∆Ep = 119mV. Galvanostatic testing showed excellent capacity retention (> 90%) and stable cycling performance. SEM analysis revealed successful thermal crosslinking at 175°C, transforming discrete particles into consolidated, uniform coatings with improved interfacial adhesion. These findings demonstrate the first successful integration of PTMA with carbon fiber substrates for structural batteries. The optimized electrodes achieve reversible electrochemical behavior while maintaining mechanical integrity, establishing a foundation for sustainable, high-power structural energy storage systems and opening pathways for lightweight, multifunctional composites in aerospace and automotive applications.