Printed flexible supercapacitor: Ink formulation, printable electrode materials and applications

Abstract

Flexible supercapacitors (FSCs) have attracted extensive attention due to their lightweight, easy integration, high power density, fast charge/discharge rate, and safe features. Printed FSC has provided an economical and simple solution for the fabrication of FSCs different from the traditional manufacturing methods. The successful preparation of printed FSCs mainly depends on the formulating of functional inks and designing of innovative electrode materials. Here, we reviewed the recent development of the ink's formulation principle, printable electrode materials, and integrated application of FSCs devices. The inks with excellent rheological properties, acquired by tuning the components (including binders, additives and solvents), are first introduced to match different printing techniques. The design of printable electrode materials is also highlighted, focusing on electrical double-layer capacitive carbons, pseudocapacitive materials (metal oxides, conducting polymer, etc.), and the newly emerging materials (MXenes, etc.). We concluded that 3D printing and new printable electrode materials will be key in successfully designing next-generation printed FSC with high energy and high power, and thus offer general guidelines to its integrated applications.