Enhanced Ion‐Selective Diffusion Achieved by Supramolecular Interaction for High Thermovoltage and Thermal Stability

Abstract

Thermoelectric (TE) generators capable of converting thermal energy into applicable electricity have gained great popularity among emerging energy conversion technologies. Biopolymer‐based ionic thermoelectric (i‐TE) materials are promising candidates for energy conversion systems because of their wide sources, innocuity, and low manufacturing cost. However, common physically crosslinked biopolymer gels induced by single hydrogen bonding or hydrophobic interaction suffer from low differential thermal voltage and poor thermodynamic stability. Here, we develop a novel i‐TE gel with supramolecular structures through multiple noncovalent interactions between ionic liquids (ILs) and gelatin molecular chains. The thermopower and thermoelectric power factor of the ionic gels are as high as 2.83 mV K−1 and 18.33 μW m−1 K−2, respectively. The quasi‐solid‐state gelatin–[EMIM]DCA i‐TE cells achieve ultrahigh 2 h output energy density (E2h = 9.9 mJ m−2) under an optimal temperature range. Meanwhile, the remarkable stability of the supramolecular structure provides the i‐TE hydrogels with a thermal stability of up to 80 °C. It breaks the limitation that biopolymer‐based i‐TE gels can only be applied in the low temperature range and enables biopolymer‐based i‐TE materials to pursue better performance in a higher temperature range.

Remarkable high-temperature ionic thermoelectric performance induced by graphene in gel thermocells

“…A parabolic profile was observed and manifested a maximum value of 3 J m −2 at 2.0 kΩ, i.e. , normalized energy density of 0.19 J m −2 K −2 , which was comparable to the reported values of 0.10 J m −2 K −2 (1 h, Wu), 43 0.006 J m −2 K −2 (4.2 h, Malik), 44 0.004 J m −2 K −2 (0.1 h, Chi), 45 and 0.0001 J m −2 K −2 (2 h, Ke) 46 (Table S2, ESI†).…”

“…4(c). A parabolic profile was observed and manifested a maximum value of 3 J m À2 at 2.0 kO, i.e., normalized energy density of 0.19 J m À2 K À2 , which was comparable to the reported values of 0.10 J m À2 K À2 (1 h, Wu), 43 0.006 J m À2 K À2 (4.2 h, Malik), 44 0.004 J m À2 K À2 (0.1 h, Chi), 45 and 0.0001 J m À2 K À2 (2 h, Ke) 46 (Table S2, ESI †). The life-span of a thermocell was tested in a quasicontinuous discharge mode at 323 K. A quasi-continuous discharge mode included the steps of the initial state, thermal charge in the open circuit, thermal discharge in I-V form, i.e., charge-discharge cycle, and being thermally charged back to high voltage in 3 min in the open circuit.…”

Design and Optimization Strategies for Flexible Quasi-Solid-State Thermo-Electrochemical Cells

“…Concentration difference effects focus on regulating the Seebeck coefficient, which requires a specific ion in the redox couple to combine with the additive to form a temperature-sensitive substance in order to enable the formation of concentration difference effects of ions at the hot and cold terminals of the electrodes. This effect has a great ability to regulate the Seebeck coefficient and can also change the direction of the redox reaction; however, the resulting conjugates may influence the rate of the redox reaction, resulting in irreversible side-reactions during the thermal cell cycling, which causes a decrease in the cycling performance and, finally, an attenuation of the output power [27,[41][42][43].…”

Facile Preparation of a Photo-Cross-Linked Silk Fibroin-Poly Ionic Liquid Hydrogel with Antifreezing and Ion Conductive Properties

“…Indeed, bioelectronics prepared by combining ILs with biopolymers in a certain way become an important member of smart materials, attributed to the excellent electrical conductivity of ILs. Natural biopolymers and their derivates, such as chitin/ chitosan, collagen/gelatin, cellulose, polylactic acid, etc., have been widely studied in complexes with ionic liquids for applications, including batteries, 15 fuel desulfurization, 16 thermoelectricity, 17 ion adsorption, 18 ion conduction, 19 etc.…”