Stretchable and Self-Healing Thermally Chargeable Hybrid Supercapacitors for Low-Grade Waste-Heat Harvesting

Abstract

Thermally chargeable supercapacitors (TCSCs) have emerged as a promising platform for harvesting low-grade waste heat; however, their practical implementation remains limited by electrolyte dehydration, poor mechanical durability, and low energy output. Herein, we report a stretchable and self-healing thermally chargeable hybrid supercapacitor (TCHS) comprising a redox-active NiMn-layered double hydroxide (NiMn-LDH) electrode and a hydroxyl-rich PSSH/SOR/PVA solid polymer electrolyte. Incorporation of d-sorbitol establishes a dynamic hydrogen-bonding network that enhances water retention (>90% after 60 h) while providing high ionic conductivity (6.09 mS·cm–1), autonomous self-healing (88% electrical recovery), and mechanical stretchability up to 350%. The hybrid thermal-charging mechanism combines ion-selective Soret diffusion within the electrolyte with redox-assisted thermoelectrochemical processes at the NiMn-LDH electrode. Under an applied temperature gradient, the hybrid device exhibits an ionic Seebeck coefficient of 2.06 mV·K–1, representing a 21.18% enhancement compared with the symmetric NF//NF configuration (1.70 mV·K–1). The enhanced thermoelectric response is attributed to the synergistic coupling of thermally driven ion migration and temperature-dependent interfacial redox processes. Under a temperature difference of 15 K, the device continuously harvested thermal energy and delivered a cumulative areal energy output of 8742 J·m–2 over 24 h, corresponding to a ∼29-fold improvement relative to the symmetric configuration. These findings demonstrate that integrating redox-active electrodes with mechanically robust polymer electrolytes provides an effective strategy for simultaneous thermal energy harvesting, charge storage, and flexible energy-conversion applications.