Modified chemical synthesis of MnS nanoclusters on nickel foam for high performance all-solid-state asymmetric supercapacitors

Novel MnS nanoclusters were synthesized on nickel foam (NF) using a successive ionic layer adsorption and reaction (SILAR) method. MnS nanoclusters with different sizes were obtained by varying the number of deposition cycles. The crystal structure, chemical composition, and surface microstructure of the electrodes were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and high resolution transmission electron microscopy. The electrochemical behavior of the MnS nanoclusters was examined by cyclic voltammetry, galvanostatic charge-discharge, cycling test, and electrochemical impedance spectroscopy. The MnS nanoclusters prepared with 90 SILAR cycles showed the best supercapacitance in a 6 M KOH aqueous electrolyte with a specific capacitance of 828 F g(-1) at a scan rate of 5 mV s(-1) and cycling stability of 85.2% after 5000 charge-discharge cycles. Moreover, an asymmetric supercapacitor (ASC) was assembled with the as-prepared MnS electrode on NF as the positive electrode, hydrothermally prepared reduced graphene oxide (rGO) on NF as the negative electrode, and PVA-KOH gel as the electrolyte. The MnS@NF//rGO@NF ASC showed excellent electrochemical performance with maximum energy and power densities of 34.1 W h kg(-1) and 12.8 kW kg(-1), respectively. The ASC also showed a capacitive retention of 86.5% after 2000 charge-discharge cycles, highlighting its practical application for energy storage.