Strong Tough Thermogalvanic Hydrogel Thermocell With Extraordinarily High Thermoelectric Performance

Abstract

Thermocells can continuously convert heat into electricity, and they are widely used to power wearable electronic devices. However, they have a risk of leakage and poor mechanical properties. Although quasi‐solid ionic thermocells can overcome the issue of electrolyte leakage, the trade‐off between their excellent mechanical properties and high thermopower remains a major challenge. In this study, stretching‐induced crystallization and the thermoelectric effect are combined to propose a high‐strength quasi‐solid stretchable polyvinyl alcohol thermogalvanic thermocell (SPTC) with a large tensile strength of 19 MPa and high thermopower of 6.5 mV K−1. The SPTC exhibits a high stretchability of 1300%, ultrahigh toughness of 163.4 MJ m−3, and high specific output power density of 1969 µW m−2 K−2. These comprehensive properties are superior to those of previously reported quasi‐solid stretchable thermogalvanic thermocells. The use of SPTC‐based systems in wearable devices for energy‐autonomous strain sensors and health monitoring is demonstrated. This can facilitate the rapid implementation of sustainable wearable electronics in the Internet of Things era.

Exploring the local solvation structure of redox molecules in a mixed solvent for increasing the Seebeck coefficient of thermocells

“…Thermocells have various applications from self-powered liquid-cooling systems 3,4 to wearable devices converting body heat into electricity. 5–13…”

Highly Antifreezing Thermogalvanic Hydrogels for Human Heat Harvesting in Ultralow Temperature Environments

“…The emerging ionic TE materials have a relatively large Seebeck coefficient that is 2–3 orders higher than that of the traditional TE materials and also exhibit excellent flexibility and stretchability. − Therefore, the development of high-performance ionic TE materials is of great significance for waste heat collection and self-powered flexible electronics. As an important class of ionic TE materials, quasi-solid thermogalvanic hydrogels have relatively high Seebeck coefficients and can continuously realize TE power generation based on the thermogalvanic effect. − Additionally, introducing the thermogalvanic effect into hydrogels can not only achieve good flexibility, stretchability, and even self-healing properties but also prevent liquid leakage of electrolytes.…”

“…Figure S9 displays the maximum output power density (P max , eq ) and specific output power density (P max /ΔT 2 , eq ). The P max greatly increases from 2.01 to 15.4 mW/m 2 , and the related formulas are as follows: where A, σ, d, and R 0 are the cross-sectional area, conductivity, effective length, and internal resistance of the APTH, respectively. In addition, V oc = S c ΔT, so eq can be expressed as and then …”

“…Figure a exhibits the cyclic tensile stress–strain curves from 0% to 100% strain. During 500 times cyclic tensile strains, the APTH still maintains high mechanical stability without obvious hysteresis, which is attributed to the intersections of the PAAm and SA networks and noncovalent interactions that can effectively dissipate the energy during deformation, , including van der Waals forces and hydrogen bonds between the hydroxyl groups in SA and the amide groups in PAAm polymer chains. Additionally, the APTH also shows excellent TE stability after 500 cyclic tensile strains or with an increased stretched strain from 0% to 100%, or even after being placed in the air for 7 days (Note S4).…”

“…Figure S9 displays the maximum output power density (P max , eq ) and specific output power density (P max /ΔT 2 , eq ). The P max greatly increases from 2.01 to 15.4 mW/m 2 , and the related formulas are as follows: normalI scd = normalV oc / ( R 0 A ) = σ normalV oc / normald normalP max = normalV oc normalI scd / 4 = σ V oc 2 / 4 normald where A, σ, d, and R 0 are the cross-sectional area, conductivity, effective length, and internal resistance of the APTH, respectively. In addition, V oc = S c ΔT, so eq can be expressed as normalP max = ( σ normalS normalc 2 / 4 d ) · normalΔ normalT 2 and then normalP max / normalΔ normalT 2 = σ S c 2 / 4 normald …”