Manganese dioxide nanosheet assemblies as electrode materials for electrocapacitive storage of magnesium ions

Flower-like nanosheet assemblies (NSAs) of MnO2 have been synthesized with adjustable thickness and crystallinity. MnO2 NSAs in the size of about 80 nm have poor crystallinity, but display a high capacitance of 341 F g−1 at the current density of 0.2 A g−1 in aqueous MgSO4 electrolyte, while 162 F g−1 and 174 F g−1 in Al2(SO4)3 and Na2SO4 solution at 0.2 A g−1, respectively. However, there is a decrease in capacitance for 120 nm MnO2 NSAs down...