Tailoring Polymer\nPolarity to Regulate Disulfide Accessibility\nin Redox-Active Particles for Organic Batteries

This study seeks to explore the relationship between\nparticle polarity\nand the electrochemical accessibility of organo-disulfide-based redox-active\nparticles. Micron-sized poly(glycidyl methacrylate) (PMGA) particles\nwere synthesized and subsequently cross-linked with thiadiazole disulfide\nto produce redox-active particles (DS-RAPs). The residual glycidyl\nunits underwent reactions with various side chains to modulate the\npolarity of the DS-RAPs. These side chains vary from nonpolar aliphatic <i>N</i>-methylbutylamine (MBA) to the more polar\noligoethylene glycol amine (EGA) and glycidyl carbonate (GC) moieties.\nCyclic voltammetry reveals that functionalization with polar side\nchains enhances electrochemical accessibility, with DS-RAP<sub>GC</sub> demonstrating the highest accessibility in both acetonitrile and\ntetraglyme-based electrolytes. Testing the DS-RAP derivatives as cathode\nelectrodes in a lithium cell with a LiTFSI/tetraglyme electrolyte\nindicates that DS-RAP<sub>GC</sub> yields the highest specific capacities,\nenergy efficiency, and best kinetics at 0.1C. Conversely, C-rate dependence\nmeasurements show that DS-RAP<sub>EGA</sub> has higher specific capacities\nat faster C-rates and is more resilient to mass transport limitations\ncompared to DS-RAP<sub>GC</sub> and DS-RAP<sub>MBA</sub>. This is\nattributed to greater electrolyte swelling in DS-RAP<sub>EGA</sub> and higher ion diffusivity, as evidenced by galvanostatic intermittent\ntitration technique (GITT) measurements. Lastly, long-term cycling\ntests at 0.1C indicate minimal degradation, with the resulting capacity\nfade attributed to charge trapping during the continuous reversible\noxidation/reduction of disulfides. Overall, these findings contribute\nsignificantly to the development of effective RAPs for energy storage\napplications, highlighting the pivotal role of chemical modifications\nvia side chain engineering in controlling particle polarity to enhance\ncharge transport and overall electrochemical performance.