Safe, high-performance, moisture-activated batteries for powering next-generation Internet-of-Things devices.

Conventional batteries are heavy, nonconformal, and toxic, while energy harvesters offer low/variable power, rendering them unsuitable for emerging wearable, robotic, and other Internet-of-Things (IoT) devices. Here, we introduce a nontoxic, thin-film battery superior to several commercial batteries inspired by advances in water harvesting techniques. It scavenges ambient moisture to serve as its electrolyte, combining features of an energy harvester with attractive features of a battery (stable and high power). It functions in a wide range of environments and offers an open-circuit voltage of ~1.6 volts, specific capacity of ~52 milliampere-hours per gram, and specific energy of ~81 milliwatt-hours per gram. Unique pangolin skin-mimicking design imparts high flexibility, stretchability, and fill factor to the battery, ensuring conformability without compromising on capacity. Experimental and computer simulation studies reveal the distinctive materials and design features responsible for the battery's impressive performance. Examples of a wireless wearable pulse oximeter and surveillance monitor with a unique kill switch that secures it from unauthorized access demonstrate the versatility of the battery to power various IoT devices.