Combined electrochemical and DFT investigations of iron selenide: a mechanically bendable solid-state symmetric supercapacitor - data

Enhancing energy storing capability with the aid of unique nanostructured morphologies is beneficial for the development of the energy-storing capability of supercapacitors. However, the developing earth-abundant and low-cost transition metal selenides (TMSs) with enhanced charge transfer capabilities and good stability is still a challenge. Herein, state-of-the-art iron selenide with a nanoflake surface architecture, synthesized with the aid of a simple, industry-scalable and ionic layer controlled chemical approach, namely the successive ionic layer adsorption and reaction (SILAR) method, is presented. The iron selenide electrode yields a capacitance of 671.7 F g-1 at a 2 mV s-1 scan rate and 434.6 F g-1 at 2 mA cm-2 current density through cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) studies, respectively, with 91.9% cyclic retention after 4000 cycles. The developed bendable solid-state supercapacitor reveals a remarkable power density of 5.1 kW kg-1 with outstanding deformation tolerance, including its use in a practical demo to run a small fan, demonstrating its capability for advanced energy storage applications. A complementary first-principles density functional theory (DFT) approach was used in combination with the experimental supercapacitive performance to achieve an understanding of the electronic structure. The data underpinning the research are available in the .xlsx format (can be viewed either by MS Office or Libre Office) comprising 10 datasheets, which are named after the figure numbers. The experimental XRD, XPS, Electrochemical charge-discharge curves, galvanostatic charge-discharge (GCD) profiles are provided. Data for the optimized structures are available in CONTCAR format of the VASP simulation program. The optimised structure of the bulk and clean surfaces are provided as VASP CONTCAR files, which can be viewed either by MS Office or WordPad and displayed using VESTA software. The projected density of states and quantum capacitance data is also given and can be plotted with any plotting software.