Strong Tough Ionic Organohydrogels with Negative‐Thermopower via the Synergy of Coordination Interaction and Hofmeister Effect

Abstract Ionic thermoelectric (i‐TE) gels have attracted widespread attention in flexible electronics due to their flexibility, leakage‐free, low toxicity, and converting low‐grade waste heat into electricity. For practical application, it is strongly desirable to fabricate negative‐thermopower (n‐type) i‐TE gels with excellent mechanical performances, which is still a big challenge. Herein, a multi‐hierarchical network structure is proposed to simultaneously improve the TE and mechanical performance. Such structure including hierarchical hydrogen bonds, coordination bonds, and dense polymer chains is realized via the synergy of the coordination effect of polymer to cations and the Hofmeister effect of anions to polymer. As a result, the optimized gel exhibits not only negative thermopower up to −3.69 mV K⁻¹ with a conductivity of 0.15 S m⁻¹ at room temperature, but also outstanding tensile strength (>6.7 MPa), elongation at break (>1100%), and toughness (>43 MJ m⁻³), which is the toughest n‐type i‐TE gel reported to date. In addition, these n‐type i‐TE gels present good freeze tolerance (−58.53 °C) and dry resistance. Furthermore, the application potentials of the i‐TE device are proven in converting human thermal power into electricity. These findings provide a new way to obtain high‐performance n‐type i‐TE materials by synergistic anion and cation action on polymers.