Enhanced Thermoelectric Performance of PVA-Based Ionogels: Tailoring Crystallinity via Additives for Advanced Waste Heat Recovery

Ling-Chieh Lee; Shao-Huan Hong; Min-Su Kim; U-Ser Jeng; Chia-Hsin Wang; Shih-Huang Tung; Keun Hyung Lee; Cheng-Liang Liu

doi:10.1021/acsami.5c08724

Enhanced Thermoelectric Performance of PVA-Based Ionogels: Tailoring Crystallinity via Additives for Advanced Waste Heat Recovery

ACS Appl Mater Interfaces. 2025 Jul 2;17(26):38545-38557. doi: 10.1021/acsami.5c08724. Epub 2025 Jun 21.

Authors

Ling-Chieh Lee¹, Shao-Huan Hong¹, Min-Su Kim², U-Ser Jeng³, Chia-Hsin Wang³, Shih-Huang Tung⁴, Keun Hyung Lee², Cheng-Liang Liu^{1

5}

Affiliations

¹ Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan.
² Department of Chemistry and Chemical Engineering, Inha University, Incheon 22212, Republic of Korea.
³ National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
⁴ Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617, Taiwan.
⁵ Advanced Research Center for Green Materials Science and Technology, National Taiwan University, Taipei 10617, Taiwan.

PMID: 40543076
DOI: 10.1021/acsami.5c08724

Abstract

Converting low-grade waste heat into electricity is crucial for green energy. This study introduces an innovative approach using poly(vinyl alcohol) (PVA)-based ionogels incorporating 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) and specific additives: 2-carboxyphenylacetic acid (H), 2-sulfobenzoic acid (S), and 2-carboxyphenyl phosphate (P)). These additives enable successful tailoring of the crystallinity, leading to a substantial increase in the ionic figure-of-merit (zT_i), from 0.006 for the PVA ionogel to 0.27 for the ionogel with P additives. Furthermore, the P-additive ionogels exhibit excellent mechanical properties, with a tensile stress of 1.75 MPa and a strain of 460%. A four-pair ionic thermoelectric capacitor made from these ionogels generates 0.33 V and achieves a power output of 2.4 mW m^-2. This advancement significantly improves the thermoelectric performance of PVA ionogels, aiding in efficient waste heat utilization and sustainable energy development.

Keywords: ionic liquid; ionic thermoelectrics; ionogel; low-grade heat harvesting; thermopower.