Ultrathin Smart Energy-Storage Devices for Skin-Interfaced Wearable Electronics

The emergence of on-skin electronics with functions in human–machine interfaces and on-body sensing calls for the development of smart flexible batteries with high performance. Electrochromic energy-storage devices provide a visual indication of the capacity through a real-time change in color without any additional power supply. In this study, dual-function battery and supercapacitor devices for skin-interfaced wearable electronics are developed by a simple and scalable transfer printing method, featuring a thickness of less than 50 μm. Supercapacitive and battery-type devices with areal capacities of 113.4 mF cm–2 and 6.1 μAh cm–2, respectively, are achieved by assembling electrochromic cathodes, hydrogel film electrolyte, and zinc anode. The high flexibility of the ultrathin energy devices endows them with good conformity on arbitrarily shaped surfaces, including elastic human skin, further enhancing the capability of intrinsically non-stretchable thin-film electronics. Our results provide a pathway for the development of versatile electronic skins and next-generation wearable electronics.