Ultrastrong, flexible thermogalvanic armor with a Carnot-relative efficiency over 8%

Body heat, a clean and ubiquitous energy source, is promising as a renewable resource to supply wearable electronics. Emerging tough thermogalvanic device could be a sustainable platform to convert body heat energy into electricity for powering wearable electronics if its Carnot-relative efficiency (η_r) reaches ~5%. However, maximizing both the η_r and mechanical strength of the device are mutually exclusive. Here, we develop a rational strategy to construct a flexible thermogalvanic armor (FTGA) with a η_r over 8% near room temperature, yet preserving mechanical robustness. The key to our design lies in simultaneously realizing the thermosensitive-crystallization and salting-out effect in the elaborately designed ion-transport highway to boost η_r and improve mechanical strength. The FTGA achieves an ultrahigh η_r of 8.53%, coupling with impressive mechanical toughness of 70.65 MJ m⁻³ and substantial elongation (~900%) together. Our strategy holds sustainable potential for harvesting body heat and powering wearable electronics without recharging.