Strategically-designed hierarchical polypyrrole-modified manganese-doped tin disulfide (SnS2) nanocomposite electrodes for supercapatteries with high specific capacity

Supercapatteries are novel energy storage devices possessing features of both supercapacitor and battery and evolved to meet the demand for portable electronic devices. An efficient electrode-active material is an important criterion for the fabrication of high performance supercapatteries. We hereby report the rapid synthesis of manganese (Mn)-doped tin disulfide (SnS2) by microwave-assisted hydrothermal method and further use it as an efficient electrode material (positrode) to fabricate a supercapattery. Dunn's kinetic method is adopted to estimate the contribution from the battery-type charge storage which confirm the electrode exhibits charge storage via diffusion-controlled mechanisms. The Mn-doped SnS2 electrode exhibits a specific capacity of 275.4 C g-1 at a scan rate of 10 mV s-1. The specific capacity is further increased by preparing nanocomposite electrodes with polypyrrole at different ratios. The polypyrrole-modified Mn-doped SnS2 electrode delivers a specific capacity of 539 C g-1 at a scan rate of 10 mV s-1. In order to understand its applicability in practical devices, a supercapattery cell is fabricated with polypyrrole-modified Mn-doped SnS2 as positrode and activated carbon as negatrode, which exhibits a mass specific capacity of 204.2 C g-1 along with an area specific capacity of 2.4 C cm-2 at a current density of 2 A g-1. The supercapattery cell possesses an energy density of 42.5 W h kg-1 with a corresponding power density of 2500 W kg-1 at a current density of 2 A g-1. This study proclaims that the polypyrrole-modified Mn-doped SnS2 is an efficient positrode for application in high-performance supercapatteries.