Water‐Soluble Hybrid Graphene Ink for Gravure‐Printed Planar Supercapacitors

Abstract

AbstractFlexible printed all‐solid‐state graphene‐based planar supercapacitors have attracted great attentions for their potential applications in portable and wearable electronics. However, the limited ion accessible surface area and slow ion diffusion rate lead to low specific capacitance and poor rate performance. Increasing the diffussion of polyvinyl alcohol (PVA)‐based gel electrolyte into the printed graphene microelectrodes is a great challenge for improving its energy storage. In this work, the hydrophilic N‐doped graphene combining with the PVA‐H3PO4 gel electrolyte is attempted to assemble to a stabilized water‐soluble graphene@PVA‐H3PO4 hybrid ink formulation for gravure‐printed planar supercapacitors. Through optimizing the ink properties and investigating the physical interaction between the ink and gravure cells, graphene@PVA‐H3PO4 microelectrodes are successfully gravure printed. The improved accessibility of electrolyte ions to the active surfaces of graphene in the printed microelectrodes leads to the enhanced electrochemical performance of the flexible planar supercapacitors. The increased areal capacitance of 37.5 mF cm−2 is achieved at a scan rate of 5 mV s−1. The maximum energy density of 5.20 µWh cm−2 is obtained at the areal power density of 3.2 mW cm−2, corresponding to a volumetric energy density of 2.08 mWh cm−3.