Tracking Multi-Electron Redox Kinetics in Li/Na-Organic Cathodes Via Operando EPR

Redox-active organic materials hold great potential as electrode materials for Li-ion and next-generation batteries due to their low cost, high theoretical capacity, and synthetic tunability. Understanding charge–discharge kinetics in organic electrodes is essential for decipering their redox mechanisms and guiding rational cathode design. Operando electron paramagnetic resonance (EPR) has already shed light on two-electron lithiation/delithiation pathways but overlapping cathode- and anode-derived signals hinder quantitative analysis of radicals during cycling. Using a custom operando EPR cell that independently probes the cathode and anode, we tracked the evolution of radical speciation and concentration in tetraaminobenzoquinone (TAQ) cathodes throughout charge-discharge cycles. Our results suggested a four-electron redox sequence proceeding through consecutive single-electron transfers, each characterized by a distinct rate constant. By varying anode (Li vs Na) and tuning the cathode’s crystallinity and oxidation state, we can disentangle the respective roles of cation intercalation, structural order, and electronic configuration in dictating multi-electron kinetics.