Thiourea Bismuth Iodide: Crystal structure, Characterization and High Performance as an Electrode Material for Supercapacitors

This paper reports on the synthesis, crystal structure and application of a novel hybrid bismuth-halide complex: (CN2SH5)3BiI6 (TBI) for supercapacitor applications, featuring merits including high areal capacitance, low cost, solution-processability and non-toxicity. Single crystal X-ray diffraction reveals that TBI crystallizes in the monoclinic system, with discrete [BiI6]3- octahedra as the inorganic motif. Utilizing TBI as the active supercapacitor electrode material with carbon cloth current collector and aqueous NaClO4 electrolyte, an electrode areal capacitance of 3.32 F/cm2 and a systemic specific capacitance of 1030 F/g was achieved when the device operates as an electric double-layer capacitor (EDLC). The supercapacitor device shows excellent capacitance retention even after 5,000 charge-discharge cycles. The powder XRD patterns, Raman spectroscopy and SEM images of TBI electrodes were compared before and after the cycling test to demonstrate the material stability and investigate the film morphology.