Defeating Mechanical-Thermoelectric Performance Conflict in Hydrogel Thermocells via Mechanical Orientation Boost: A Universal Strategy.

The advancement of high-performance hydrogel thermocells is constrained by a fundamental trade-off: strategies to enhance mechanical robustness, such as densifying polymer network or strengthening intermolecular interactions, often compromise thermoelectric performance due to a network-block effect that impedes ion transport. Here, we report a universal mechanical-orientation-boost (MeOB) strategy that defies this conventional conflict​ by mechanically prealigning polymer chains to create structurally anisotropic hydrogels. This orientation not only fortifies the polymer backbone but also establishes streamlined ion pathways, thereby simultaneously boosting both mechanical and thermoelectric performances. We validate this approach across three distinct hydrogel systems. Hydrogel thermocells optimized with this method exhibit unprecedented synergistic enhancements, with maximum performance gains of a 971% increase in tensile strength, a 1410% rise in fracture toughness, a 4682% improvement in fatigue threshold, alongside a 75% enhancement in Seebeck coefficient, a 172% boost in power factor and a 730% improvement in normalized power density, all while maintaining exceptional electrochemical stability. This work provides a universal route to designing high-performance, mechanically-robust thermocells for energy-autonomous electronics in the Internet of Things.