A successive ionic layer adsorption and reaction (SILAR) method to fabricate a layer-by-layer (LbL) MnO₂-reduced graphene oxide assembly for supercapacitor application

A facile, cost effective and additive-free successive ionic layer adsorption and reaction (SILAR) technique is demonstrated to develop layer-by-layer (LbL) assembly of reduced graphene oxide (RGO) and MnO₂ (MnO₂-RGO_SILAR) on a stainless steel current collector, for designing light-weight and small size supercapacitor electrode. The transmission electron microscopy and field emission scanning electron microscopy images shows uniform distribution of RGO and MnO₂ in the MnO₂-RGO_SILAR. The LbL (MnO₂-RGO_SILAR) demonstrates improved physical and electrochemical properties over the hydrothermally prepared MnO₂-RGO (MnO₂-RGO_Hydro). The electrochemical environment of MnO₂-RGO_SILAR is explained by constant phase element in the high frequency region, and a Warburg element in the low frequency region in the Z-View fitted Nyquist plot. The equivalent circuit of the MnO₂-RGO_Hydro, displays the co-existence of EDL and constant phase element, indicating inhomogeneous distribution of MnO₂ and RGO by the hydrothermal technique. An asymmetric supercapacitor device is designed with MnO₂-RGO_SILAR as positive electrode, and thermally reduced GO (TRGO) as negative electrode. The designed cell exhibits high energy density of ∼88 Wh kg⁻¹, elevated power density of ∼23,200 W kg⁻¹, and ∼79% retention in capacitance after 10,000 charge-discharge cycles.