Recent progress in aqueous based flexible energy storage devices

Flexible electronics are forefront technologies with the growing demand for future deformable and wearable applications, including the Internet of Things (IoT), healthcare devices, integrated artificial skins, and wearable electronics. Rapidly evolving devices are strongly pushing to develop flexible energy devices as a power source. Flexible energy storage devices based on an aqueous electrolyte, alternative battery chemistry, is thought to be a promising power source for such flexible electronics. Their salient features pose high safety, low manufacturing cost, and unprecedented electrochemical performance. In this review, we focus on pioneering works of flexible aqueous energy storage devices for flexible electronics, covering the material designs for essential components of the energy devices such as active materials, current collectors, aqueous electrolyte, and separator membranes. In addition, we touch flexible aqueous energy devices with various configurations like thin-film energy devices, fiber energy devices, and porous matrix energy devices. Also, we present recent advanced aqueous energy with transparent and stretchable features beyond flexibility. Further, the challenges facing the practical application of flexible aqueous energy storage devices and the perspective of the current hurdles are proposed.