The Role of Graphene Oxide as a Filler and Lanthanum Nitrate as a Salt in Corn Starch-Based Solid Polymer Electrolytes

Solid polymer electrolytes (SPE) with high ionic conductivity are in great demand for the effective application of solid-state electrochemical devices. Therefore, this study aimed to improve ionic conductivity of corn starch (CS)-based SPE by incorporating lanthanum nitrate salt and graphene oxide (GO) as filler. The solution casting method was used to produce a thin SPE film, and X-Ray Diffraction (XRD) investigations found that the SPE structure had a higher degree of amorphousness during the addition of salt and GO. Furthermore, the Fourier Transform Infrared (FTIR) Spectroscopy data presented a change in the functional group alongside an increased intensity in the C-O-H group, signifying the formation of hydrogen bonds with GO and the cleavage of the CO-C chain due to the introduction of salt. The analysis conducted with the Scanning Electron Microscope (SEM) identified that the interaction with GO led to enhanced porosity, generating additional cavities in the SPE sample. The amorphous structure was confirmed through Differential Scanning Calorimetry (DSC), which showed a reduction in melting point with the incorporation of salt and GO. Increased ionic conductivity in SPE was observed in Electrochemical Impedance Spectroscopy (EIS) after GO incorporation. Ionic conductivity measured without the presence of filler was 9.95x10-7 S/cm while adding 1% of filler improved conductivity by 126.13% with a value of 2.25x10-6 S/cm. GO inclusion in CS-based SPE film enhanced the interaction between ions and polymer, promoting an increase in ionic conductivity. The results showed the possible applicability of electrochemical energy storage, such as lithium-ion batteries and supercapacitors.