Beta-manganese dioxide nanoflowers self-assembled by ultrathin nanoplates with enhanced supercapacitive performance

Hierarchical porous β-MnO2 nanoflowers self-assembled by ultrathin (thickness less than 10 nm) nanoplates have been successfully fabricated at room temperature. Because of its high specific surface area (267 m2 g−1) and proper pore size distributions (average pore size, ca. 5.9 nm), the obtained 3D nanomaterials achieve enhanced capacitance as high as 296.3 F g−1 at a scanning rate of 2 mV s−1, which is ∼20 times of those of the traditionally prepared nanostructural β-MnO2 (e.g. 1D hollow β-MnO2 nanorods with ∼14.9 F g−1). Furthermore, it has an appreciable ability to deliver large energy densities at high rates (67.4% capacitive retention). The comparable property with α-MnO2 indicates that such low-cost porous β-MnO2 nanoflowers may also be a very promising candidate material for supercapacitors besides lithium battery material.