Fast Self‐Charging Flexible Device Based on Metal–Air Redox Reaction under Normal Humidity

Nowadays, self‐charging devices using clean energy have raised the potential of portable and wearable power generators. Herein, a novel moisture‐induced self‐powered device based on metal–air redox reaction has been designed which can work under normal humidity conditions. Through bridging two asymmetric electrodes including a carbon nanotube/polyaniline composite electrode and a metal electrode by filter paper with CaCl 2 , the 1D planar device can be simply fabricated. A single device can provide an open‐circuit voltage of over 1.3 V under normal humidity (40%) within 5 min (the maximum can be up to 1.42 V at 80% humidity) and the harvesting energy can be stored effectively. The device possesses great circularity and stability which can maintain steady and consistent output over at least 6 months. Due to the microelectrolyte, this device can prevent harmful leakage or deformation of the electrolyte completely. What is more, the device shows good extendibility. Three single devices in series using common electrodes can light up two light‐emitting diodes. Besides its application potential in self‐powered portable and wearable electronics, this device can provide a reference for utilization in medical devices due to the response signals under breath with different frequencies.