Lamellar agarose/graphene oxide gel polymer electrolyte network for all-solid-state supercapacitor

Abstract

The application of gel polymer electrolyte (GPE) in solid state supercapacitor (SSC) has attracted much attention due to its excellent mechanical properties and chemical stability. However, traditional polymer substrates have high crystallinity, resulting in sluggish lithium migration and low ionic conductivity. In this work, density functional theory calculations (DFT) firstly reveal that agarose molecules (a natural marine polysaccharide) can be assembled to highly-ordered lamellar network structure by hydrogen bonds forming (d’ = 0.454 nm) as GPE matrix combining with graphene oxide (GO) addictive. Specifically, radial distribution functions (RDFs) show that intensities of peaks (gLi-O(r)) at 0.189 nm are 45.2 and 54.8 for agarose and agarose/GO, respectively. This finding indicates an optimized agarose molecular configuration and a rapid lithium migration in agarose/GO GPE (Ag/GO-GPE) system. When Ag/GO-GPE was prepared, SSC assembled with Ag/GO2-GPE and activated carbon electrode has high ionic conductivity (73.8 mS cm−1) and a specific capacitance as high as 791.67 mF cm−2 at a current density of 5 mA cm−2. Moreover, the electrochemical performance of SSC based Ag/GO2-GPE is stable at a bending condition of 180°, resulted from the hydrogen bonds between agarose matrix and GO. In addition, Ag/GO2-GPE has an excellent mechanical strength (0.115 MPa) and flame retardant performance (heat release rates (HRR) of 11.08 kw/m2 and total heat release (THR) of 0.79 MJ m2). This research opens up a novel avenue to develop safe and efficient flexible wearable SSCs.