Regulating Thermogalvanic Effect and Mechanical Robustness via Redox Ions for Flexible Quasi-Solid-State Thermocells

TLDR

Wearable power supplies demand flexibility and durability, and thermoelectrochemical cells with high Seebeck coefficients can convert low‑grade heat to electricity, but conventional liquid‑based TECs suffer from leakage and packaging issues, while mechanical robustness remains a challenge. The authors propose a flexible quasi‑solid‑state TEC that simultaneously regulates thermogalvanic effect and mechanical robustness via multivalent redox ions. Redox ions in the hydrogel provide heat‑to‑electricity conversion and act as ionic crosslinks, creating a dual‑crosslinked structure with reversible bonds for effective energy dissipation. The optimized TEC achieves a Seebeck coefficient of 1.43 mV K⁻¹ and fracture toughness of 3555 J m⁻², enabling stable performance under harsh mechanical stimuli and demonstrating its potential as a flexible, durable energy supply for wearables.

Abstract

Abstract The design of power supply systems for wearable applications requires both flexibility and durability. Thermoelectrochemical cells (TECs) with large Seebeck coefficient can efficiently convert low-grade heat into electricity, thus having attracted considerable attention in recent years. Utilizing hydrogel electrolyte essentially addresses the electrolyte leakage and complicated packaging issues existing in conventional liquid-based TECs, which well satisfies the need for flexibility. Whereas, the concern of mechanical robustness to ensure stable energy output remains yet to be addressed. Herein, a flexible quasi-solid-state TEC is proposed based on the rational design of a hydrogel electrolyte, of which the thermogalvanic effect and mechanical robustness are simultaneously regulated via the multivalent ions of a redox couple. The introduced redox ions not only endow the hydrogel with excellent heat-to-electricity conversion capability, but also act as ionic crosslinks to afford a dual-crosslinked structure, resulting in reversible bonds for effective energy dissipation. The optimized TEC exhibits a high Seebeck coefficient of 1.43 mV K −1 and a significantly improved fracture toughness of 3555 J m −2 , thereby can maintain a stable thermoelectrochemical performance against various harsh mechanical stimuli. This study reveals the high potential of the quasi-solid-state TEC as a flexible and durable energy supply system for wearable applications.