Highly Compressible Cross-Linked Polyacrylamide Hydrogel-Enabled Compressible Zn–MnO2 Battery and a Flexible Battery–Sensor System

The fast advancement in flexible and wearable electronics has put up with new requirements on the energy storage device with improved tolerance to deformation apart from offering power output. Despite the tremendous progress in stretchable energy storage devices, the compressional energy storage devices have indeed received limited research attention. In this work, an intrinsically compressible rechargeable battery was proposed using the Zn-MnO2 chemistry and a cross-linked polyacrylamide hydrogel electrolyte. Interestingly, the battery exhibited not only good energy storage performances but also excellent tolerance against large compressional strain without sacrificing the energy storage capability. It was also found that the ionic conductivities of the hydrogel increased with the values of the compressional strain, leading to an enhanced electrochemical performance. More importantly, upon dynamic compression, the voltage output of the battery can be very stable and reliable. Consequently, the battery assembled using the hydrogel electrolyte can be used to power a luminescent panel even with a 3 kg load on top of it. It was also demonstrated that the flexible sensor powered by our compressible battery exhibited similar and stable sensory signals compared with the same sensor powered by two commercial alkaline batteries. Furthermore, because of the excellent mechanical property of our battery, a smart wristband fabricated by integrating two battery packs and the flexible piezoresistive sensor could be powered and used to monitor the pressure exerted, demonstrating the battery's potential as the wearable power source for the flexible and wearable devices.