Architecture-preserving interfacial regulation via sulfonated graphene oxide for high-performance stretchable ionic thermoelectrics

Stretchable ionic thermoelectric (i-TE) materials capable of simultaneously delivering high thermopower and mechanical compliance are essential for harvesting low-grade heat in deformable, self-powered human-machine interfaces. In these systems, the electrical potential originates from the Soret-effect-driven asymmetric thermo-diffusion of ions. However, conventional strategies typically rely on bulk polymer modifications to regulate this asymmetry, which inherently couples ionic transport with the host polymer's structural properties, thereby limiting the independent optimization of electrochemical and mechanical performance. Here, we report a sulfonated graphene oxide (SGO)-mediated interfacial regulation strategy that modulates ionic transport without altering the host polymer framework. The incorporation of SGO nanosheets provides immobilized anionic sites that significantly enhance ion-mobility asymmetry, while simultaneous hydrogen-bonding and ion–dipole interactions reinforce the polymer network. When integrated into a polyacrylamide (PAM) network containing a deep eutectic solvent (DES), the resulting SGO-based eutectogel exhibits a high ionic Seebeck coefficient of 18.0 mV K−1, an ionic conductivity of 7.95 mS cm−1, and a dimensionless figure of merit (zTi) of 0.71. Beyond its TE performance, the eutectogel maintains 87% of its initial Seebeck coefficient even under 500% tensile strain and shows minimal degradation (< 10%) after 500 deformation cycles. The practical utility of this system was validated through a serialized 4 × 4 array module that successfully harvests low-grade waste heat from daily electronics to directly power a light-emitting diode and drive a small fan. This design offers a structurally simple yet versatile platform for high-performance i-TE systems operating in mechanically dynamic environments.