Cation-Doped Ionic Thermoelectric Ionogels With Nonlinear Temperature-Voltage Response Characteristics

As next-generation quasi-solid-state ionic thermoelectric materials, ionogels show great potential in low-grade waste heat recovery and efficient energy management, with their thermoelectric performance stemming from cation-anion diffusion rate differences under thermal gradients. In this study, a PVDF-HFP-based ionogels, achieving a thermopower of 23.7 mV K^-1 and a power density of 102.8 µW m^-2 K^-2 by manipulating ion-ion interactions is developed. Interestingly, precise control of the temperature difference, leading to nonlinear temperature-voltage characteristics. By doping a series of cations with different properties such as charge quantity and ionic radius, the ion-ion interactions are analyzed to explore the influencing mechanism on the nonlinear feature arising from the dynamic reconstruction of ion concentration. This feature facilitates thermal switching for overheat protection in electronics. A device with 18 ionogel units is fabricated, achieving 2.09 V output and dynamically controlling an LED. This work reveals the role of cation doping in regulating thermoelectric properties from the perspectives of ion-ion interactions and demonstrates the application of ionogels in thermal management via nonlinear thermal response.