Heat-triggered self-powered thermal cells for autonomous fire sensing and emergency power generation

Fire safety in enclosed spaces is frequently compromised by power failures, creating an urgent need for self-powered monitoring systems. However, designing devices that simultaneously achieve high detection sensitivity and sufficient power drive remains a formidable challenge. Here, this work proposes an asymmetric thermal cell (ATC) that utilizes high-entropy-change driven mechanism and strategically designed redox couples of the FeCl₃/K₄[Fe(CN)₆] with opposite temperature coefficient. This design synergistically amplifies the output voltage by combination of the thermogalvanic effect and electrochemical potential. Crucially, this mechanism enables a single ATC to achieve 0.71 V (with a ∼33% thermal contribution at 90 °C) and sustain high-current discharge at 70–90 °C without a spatial temperature gradient, making it ideal for fire scenarios with nearly spatially uniform temperature across the device. Accordingly, the ATC delivering a high temperature coefficient of 2.8 mV/K, a peak power density of 11.34 W/m², and a high specific energy density of 87.7 mAh/g. A prototype of five series-connected ATC units successfully generated a stable 3.15 V output under simulated fire conditions, powering both an LED escape indicator and a wireless smoke alarm. This work offers a feasible way toward self-powered, heat-triggered emergency evacuation system that operate independently of external power grids.