Graphene-based flexible all-solid-state supercapacitors
With the ever-increasing need for portable and wearable electronics, flexible all-solid-state supercapacitors (ASSSC) have attracted wide attention and show promising application as power sources due to their fast charge-discharge rate, high power density, low cost, easy fabrication, and excellent customizability and versatility. Graphene possesses extraordinary physical properties including large specific surface area and high electronic conductivity and has been viewed as an ideal active electrode material for supercapacitors. Thus far, graphene-based flexible macroscopic assemblies, such as graphene-based films (freestanding films or flexible substrate supported films) and graphene-based fibers have been created and extensively researched as active electrodes for flexible ASSSC. The electrochemical performance of supercapacitors is greatly determined by the structures and physicochemical properties of the active electrode materials, and the mechanical strength of the flexible electrodes largely determines the electrochemical performance of the ASSSC under mechanical deformations including stretching, bending, rolling, and folding. This submitted manuscript gives a up-to-date overview on the controllable fabrication of graphene-based film/fiber electrodes together with the involved scientific issues that need to be addressed, and the electrochemical/mechanical performances of the corresponding graphene-based flexible ASSSC (film-based and fiber-based ones) associated with the strategies that are generally utilized to improve the performances. As a final part, this contribution concludes with some challenges and prospects before graphene-based flexible ASSSC are really commercialized as power systems for wearable and portable electronics.