Enhanced Energy Output Achieved in Ionic Thermoelectric Hydrogels via an Asymmetric Configuration

ABSTRACT Ionic thermoelectric (i‐TE) materials are characterized by their flexibility, non‐toxicity, and high thermopower, rendering them highly promising for powering wearable electronic devices. However, their current energy density remains relatively low, peaking at merely 12.4 J m −2 K −2 , insufficient to meet the energy demands of modern electrical devices. Here we present a novel strategy to enhance the energy density of i‐TE materials through the implementation of an asymmetric device configuration. In this approach, a polyelectrolyte, polydimethyl diallyl ammonium chloride (PDDAC), is deposited on one side of a polyvinyl alcohol (PVA) hydrogel, significantly boosting power output by leveraging the salinity gradient energy derived from a nonthermally driven diffusion process. Consequently, we achieved an impressive energy density of 52.5 ± 4.5 J m −2 K −2 , marking the highest value reported in this field to date. This substantial improvement is attributed to the synergistic coupling of salinity gradient energy with ionic thermoelectricity, which enhances the overall voltage and energy output by adding a voltage contribution from the salinity gradient to the ionic thermovoltage.