Hydrogel　thermocells　can　directly　convert　low-grade　thermal　energy,　such　as　industrial　waste　heat,　solar　heat,　and　human　body　heat,　into　electrical　energy　through　redox　reactions.　However,　existing　hydrogel　thermocells　still　face　challenges　in　practical　applications,　including　low　output　power　density　and　poor　mechanical　properties.　Inspired　by　the　porous　network　structure　of　plant　roots,　a　nanoporous　hydrogel　thermocell　is　designed　through　the　synergy　of　co-nonsolvency　effect　and　Hofmeister　effect.　The　interconnected　nanoporous　network　structure　can　serve　as　efficient　ion-transport　channels,　enabling　the　hydrogel　thermocells　to　achieve　a　high　thermopower　of　4.13　mV　K−1,　a　superior　conductivity　of　11.07　S　m−1,　and　a　significantly　enhanced　normalized　output　power　density　of　5.34　mW　m−2　K−2.　Simultaneously,　the　densified　porous　network　skeleton　can　effectively　increase　the　mechanical　properties　of　the　hydrogel　thermocells,　with　a　tensile　strength　of　9.06　MPa　and　a　stretchability　of　1460　%.　After　connecting　20　thermocell　units　in　series,　it　can　output　a　voltage　above　2　V　to　directly　drive　electronic　devices,　demonstrating　tremendous　application　potential　in　the　fields　of　thermal-electric　energy　conversion　and　self-powered　flexible　technology.　©　2025　Elsevier　Ltd