Design and performance of high-efficiency flexible thermoelectric Mmaterials and devices

Design and performance of high-efficiency flexible thermoelectric Mmaterials and devices

Thermoelectric (TE) materials, realizing the conversions between heat and electrics, have grasped intensive interest in temperature control, power generation, wearable electronics, and low-grade (< 400 K) waste heat recycling. Particularly, flexible TEs (FTEs) exhibit exceptional mechanical properties, light weight features, and outstanding processing performance. However, some unavoidable shortcomings such as insufficient TE performances, high toxicity, high price, and tedious pre-/post-processing steps still exist. Thus, this thesis focuses on preparing high-efficiency flexible TE materials, optimizing their performances, and digging into internal theories. Furthermore, as-prepared materials are utilized to install TE devices, ensuring their practical applications. We initially developed a super-large 25×20 cm2 commercial-graphite produced p-type composite films, by one-step standard industrial hot-pressing process. The prepared composite films with an optimized power factor (S2σ) of 94 μW m-1 K-2 are highly flexible and industrially promising. Furthermore, we utilized the ultrafast and cost-effective hot-pressing method to fabricate an ionic liquid/phenolic resin/carbon fiber/expanded graphite hybrid n-type film. The expanded graphite as the major component enables high flexibility, the introduction of phenolic resin and carbon fiber enhances the shear resistance and toughness of the film, while the ion-induced carrier migration contributes to a high power factor of 38.7 μW m−1 K−2. At last, a graphene oxide hybrid ionic FTE film was prepared, showing high comprehensive TE performance of S of −76.7 mV K−1, S2σ of 85.9 μW m−1 K−2, and ZT of 0.086 at 383 K, which is competitive among existing ionic thermoelectric materials. Simultaneously, tensile strength of 219.7 kPa, elongation at break of 389 %, Young’s module of 84.1 kPa, toughness of 0.4 MJ m−3, and flexibility of 180° bending are performed in this film. The in-situ integrated 9-leg 25×25 mm2 flexible device generates a superior output voltage of 205 mV under a small temperature difference of 5.7 K. This work involves the comprehensive study in the FTE area, where the results will provide general and valuable guidance to the material preparation, performance enhancement, devices designation, and industrial amplification.

File reproduced in accordance with the copyright policy of the publisher/author.