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Abstract

The growing need for advanced, safe battery technologies across a spectrum of applications—from handheld devices to industrial-scale energy storage—demands innovative solutions beyond conventional metal-based systems. This dissertation investigates organic redox-active materials, with a specific focus on redox-active polymer particles (RAPs), as promising sustainable substitutes in battery technology. The application of these engineered polymers included lithium batteries and redox flow batteries, including cutting-edge redox targeting flow battery designs. Here in this dissertation, the synthesis and characterization of a series novel RAPs are investigated. Chapter 2 synthesizes redox-active polymer particles (RAPs) by crosslinking poly(glycidyl methacrylate) with redox-responsive disulfide groups, demonstrating superior electrochemical reversibility compared to small molecule analogues due to effective spatial confinement. Optimal electrolyte conditions, identified through galvanostatic cycling, showcased that a dimethyl sulfoxide/magnesium triflate mix enhances both stability and specific capacity. Notably, smaller particle sizes correlated with higher specific capacities. These findings highlight the potential of organosulfur-based materials for advanced multi-electron energy storage beyond lithium-ion systems. Chapter 3 introduces a novel electrode cleaning strategy for electrochemical flow cells using the similar RAPs in Chapter 2, specifically targeting electrode fouling, a prevalent issue in such systems. These RAPs can de-crosslink via electrochemical reduction or UV photoexcitation. In a custom flow cell with an artificially fouled ITO electrode, applying these stimuli resulted in 80% particle removal—six times more efficient than without stimulation. Furthermore, post-cleaning electrode performance restored accessible charge to levels comparable to a pristine electrode. This approach demonstrates the potential of stimuli-responsive RAPs to enhance maintenance and functionality in electrochemical flow cells. In Chapter 4, side chain modifications were applied to RAPs to enhance cycling stability and electrochemical performanceInitial modification with non-polar N-methylbutylamine (MBA) side chains (DS-RAPMBA) improved stability, while subsequent functionalization with polar, lithium-solvating oligoethylene glycol (OEG) and glycerol carbonate (GC) side chains significantly enhanced the electrochemical responses. DS-RAPGC exhibited the highest capacity, followed by DS-RAPOEG and DS-RAPMBA, with unmodified DS-RAP showing the lowest. Enhanced swelling in DS-RAPOEG and DS-RAPGC improved ion transport, contributing to their superior performance across various C rates and long-term cycling tests at 0.1C for 400 cycles, with minimal degradation. This study demonstrates the effectiveness of side chain modification adjacent to the redox center in enhancing the electrochemical properties of organic materials for energy storage applications. Chapter 5 details a novel synthetic method for creating poly-3,4-ethylenedioxythiophene (PEDOT) nanoparticles functionalized with a disulfide/thiolate redox couple, 2,5-dimercapto-1,3,4-thiadiazole (DMcT), to produce dual redox particles for use as organic cathode materials in Li-ion batteries. The nano-sized PEDOT-DMcT-Li particles, characterized by dense crosslinking with redox-active disulfides, exhibit significantly enhanced capacity due to improved electrochemical accessibility and a semiconducting backbone that reduces internal resistance. Comprehensive evaluations, including cyclic voltammetry (CV) and galvanostatic cycling, confirm the material's dual electrochemical behavior and exceptional long-term stability without degradation. Optimized asymmetrical cycling conditions further improved capacity retention, eliminating the need for additional chemical modifications. These results underscore the potential of the PEDOT-DMcT-Li dual-redox system for advancing battery performance. Chapter 6 utilized similar molecular design from Chapter 2 and 3, changing the topic of energy storage to trainable jamming. DS-RAPs are capable of forming amorphous structures with varying degrees of percolation in response to electrochemical stimuli or UV light. This adaptiveness, inspired by biological organisms, is achieved through a dynamic disulfide crosslinker in the particles, which supports tunable mechanical properties through reductive cleavage during repeated cycling in a toggled field. Additionally, our stimulus-responsive jamming network incorporates structural memory, controlled by external small amplitude oscillatory shear, allowing the complex modulus to be adjusted over several orders of magnitude based on specific training protocols. This mechanism also permits resetting by erasing structural memory. These advancements herald a new class of materials with trainable properties at both the molecular and mesoscopic scales. Chapter 7 highlights other redox active polymeric systems to further expand the library of RAPs, including nanosized DS-RAPs, dual functionalized polymer particles containing both disulfide and ferrocene moieties, RAP with diselenide as redox active components, and polyvinyl benzyl chloride (PVBC) particles with ferrocene as redox active components for redox targeting flow battery.

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