The growth of the markets of IoT and wearable electronics led to a demand for all-in-one energy harvesting & storage technologies integrated on clothing, with a myriad of applications ranging from Healthcare and Protection to Fashion and Defense.
Thermoelectric energy harvesting (EH) technology is a promising solution for wearables since it converts the low-grade wasted heat from the environment or human body into electrical energy. Supercapacitors (SCs) are a clean and safe electrochemical energy storage (ES) solution, owing to their high power density, fast charging and long cycle life. The hybridization of both technologies in a single all-in-one EH/ES device opens new horizons towards the next generation of self-powered wearable technologies.
This work reports the development of advanced thermally-chargeable textile SCs (TCSCs) using carbon nanotubes (CNTs), either unmodified or hybridized with transition metal oxides/sulfides as active electrode nanomaterials and a non-toxic solid-gel ionic polyelectrolyte.
The TCSCs efficiently converted the harvested thermal energy into electrical energy and simultaneously stored it. The CNT-based TCSC afforded an output potential of ~30 mV for ΔT = 25 K and a Soret coefficient  of 1.85 mV/K. The TCSCs based on the hybrid nanomaterials presented enhanced specific capacitance and potential window relative to the CNT-based TCSC owing to the simultaneous occurrence of non-faradaic and pseudocapacitive charge storage mechanisms. The role of the hybrid electrode materials in the thermally-triggered charging of the devices will be discussed, as well as in their energy storage ability.

Funding: Work financially supported by PT funds through FCT/MCTES (project PTDC/CTM-TEX/4126/2021).

Acknowledgments: Supported by PT funds through FCT/MCTES (projects UIDB/50006/2020, UIDP/50006/2020 and UIDB/04968/2020). CP and JST thank FCT for funding through Individual Call to Scientific Employment Stimulus (2021.04120.CEECIND/CP1662/CT0008) and PhD scholarship (SFRH/BD/145513/2019), respectively.