Alteration in capacitive performance of Sn-decorated MnO2 with different crystal structure: An investigation towards the development of high-performance supercapacitor electrode materials

Hetero atom doped-MnO2 is considered as the promising supercapacitor electrode material due to its high capacitance properties. Depending on the way of MnO6 octahedra interlinking, it can form different types of crystal structure (α, β, γ, δ). The capacitance properties of MnO2 depend on the cation intercalation/de-intercalation and the type of crystallographic structures. This study emphasises the phase and interlayer spacing control synthesis of Sn-incorporated MnO2 (α, β, γ, δ crystal form) through a facile one-pot hydrothermal technique by using verities of starting materials. The specific capacitance of MnO2 depends on different crystal structure and the effect of hetero atom introduction. Sn-decorated β-MnO2 (β-SM) exhibits high specific capacitance of ~1957 F g−1 at 2 A g−1 in a three-electrode system. An asymmetric supercapacitor (ASC) is configured by intriguing high capacity β-SM as positive electrode and thermally reduced graphene oxide (TRGO) as negative electrode in the potential window of 1.4 V. The ASC delivers the maximum specific energy of ~29.79 W h kg−1 with a specific power of ~1625.31 W kg−1 at the current density of 2 A g−1. The ASC shows good cycle life of ~94% retention in specific capacitance after 10,000 charge-discharge cycles at 15 A g−1 current density