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Vol. 17 (2025)

Organic Radical-Boosted Ionic Conductivity in Redox Polymer Electrolyte for Advanced Fiber-Shaped Energy Storage Devices

https://doi.org/10.1007/s40820-025-01700-9
Jeong‑Gil Kim
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, 92 Chudong‑ro, Bongdong‑eup, Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea
Jaehyoung Ko
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, 92 Chudong‑ro, Bongdong‑eup, Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea
Hyung‑Kyu Lim
Division of Chemical and Bioengineering, Kangwon National University, Chuncheon 24341, Republic of Korea
Yerin Jo
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, 92 Chudong‑ro, Bongdong‑eup, Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea
Hayoung Yu
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, 92 Chudong‑ro, Bongdong‑eup, Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea
Min Woo Kim
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, 92 Chudong‑ro, Bongdong‑eup, Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea
Min Ji Kim
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, 92 Chudong‑ro, Bongdong‑eup, Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea
Hyeon Su Jeong
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, 92 Chudong‑ro, Bongdong‑eup, Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea
Jinwoo Lee
Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak‑ro, Yuseong‑gu, Daejeon 34141, Republic of Korea
Yongho Joo
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, 92 Chudong‑ro, Bongdong‑eup, Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea
Nam Dong Kim
Institute of Advanced Composite Materials, Korea Institute of Science and Technology, 92 Chudong‑ro, Bongdong‑eup, Wanju‑gun, Jeollabuk‑do 55324, Republic of Korea

Corresponding Author: Nam Dong Kim

ndkim@kist.re.kr

Nano-Micro Letters, Vol. 17 (2025), Article Number: 185

Abstract

Fiber-shaped energy storage devices (FSESDs) with exceptional flexibility for wearable power sources should be applied with solid electrolytes over liquid electrolytes due to short circuits and leakage issue during deformation. Among the solid options, polymer electrolytes are particularly preferred due to their robustness and flexibility, although their low ionic conductivity remains a significant challenge. Here, we present a redox polymer electrolyte (HT_RPE) with 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (HT) as a multi-functional additive. HT acts as a plasticizer that transforms the glassy state into the rubbery state for improved chain mobility and provides distinctive ion conduction pathway by the self-exchange reaction between radical and oxidized species. These synergetic effects lead to high ionic conductivity (73.5 mS cm−1) based on a lower activation energy of 0.13 eV than other redox additives. Moreover, HT_RPE with a pseudocapacitive characteristic by HT enables an outstanding electrochemical performance of the symmetric FSESDs using carbon-based fiber electrodes (energy density of 25.4 W h kg−1 at a power density of 25,000 W kg−1) without typical active materials, along with excellent stability (capacitance retention of 91.2% after 8,000 bending cycles). This work highlights a versatile HT_RPE that utilizes the unique functionality of HT for both the high ionic conductivity and improved energy storage capability, providing a promising pathway for next-generation flexible energy storage devices.


Highlights:
1 Developed a versatile HT-based redox polymer electrolyte with exceptional ionic conductivity (73.5 mS cm−1) through self-exchange reaction-based ion hopping mechanism and enhanced polymer chain mobility.
2 Achieved superior electrochemical performance (25.4 Wh kg−1 at 25,000 W kg−1) in fiber-shaped energy storage devices without additional active materials by utilizing HT as both ionic conductor and redox-active species.

Keywords

Redox polymer electrolyte Hydroxy-TEMPO Ionic conductivity Self-exchange reaction Fiber-shaped energy storage devices
Kim, Jeong‑Gil, Jaehyoung Ko, Hyung‑Kyu Lim, Yerin Jo, Hayoung Yu, Min Woo Kim, Min Ji Kim, Hyeon Su Jeong, Jinwoo Lee, Yongho Joo, and Nam Dong Kim. 2025. “Organic Radical-Boosted Ionic Conductivity in Redox Polymer Electrolyte for Advanced Fiber-Shaped Energy Storage Devices”. Nano-Micro Letters 17 (March):185. https://doi.org/10.1007/s40820-025-01700-9.
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