(2ln) Redox Gel Polymer Electrolyte with Radical Molecules for Fibrous Energy Storage Devices

Fiber-shaped energy storage devices (FSESDs) are gaining attention as a promising wearable power supplier due to inherent flexibility and compatibility with fabrics/textiles based on high aspect ratio of fibers. Among component in FSESDs, integration of solid-state electrolytes is crucial to prevent short-circuit of devices and leakage of electrolytes during intense body movements, which often compromise their electrochemical performance owing to low ionic conductivity and the electrode-electrolyte interface issues. To overcome these challenges, researchers have proposed a solid electrolyte incorporating a redox additive that replaces pseudo-capacitive materials in fibrous electrodes and enhances ionic conductivity. In this study, we propose a redox polymer electrolyte system (RPE) incorporating 2,2,6,6-tetramethylpiperidine 1-oxyl (HT), the organic radical molecule known for its hydrophilicity and high electron transfer rate constant. The HT in the RPE is enable to pseudo-capacitive behavior by undergoing electrochemical faradaic reaction at its radical sites. The RPE exhibit high ionic conductivity of 73.5 mS cm^-1 via hopping process based on self-exchange reaction and strengthened segmental motion of the chain by amorphous nature of polymer. Hence, FSESDs integrating RPE systems reveal high electrochemical performance (17 Wh kg^-1 energy density at a power density of 97,000 W kg^-1) and superb electrochemical stability compared to other additives. This study presents a promising strategy for the development of a versatile RPEs that holds potential for application beyond FSESDs in various fields.