Novel Ultrathin Nanoflake Assembled Porous MnO₂/Carbon Strip Microspheres for Superior Pseudocapacitors

A novel hierarchical MnO₂/carbon strip (MnO₂/C) microsphere is synthesized via galvanostatic charge–discharge of a MnO@C matrix precursor where the carbon is from a low-cost citric acid. This hierarchical structure is composed of manganese oxides nanoflakes and inlaid carbon strips. The ultrathin nanoflakes assemble to form porous microspheres with a rippled surface superstructure. Due to its improved conductivity and remarkable increased phase contact area, this novel structure exhibits an excellent electrochemical performance with a specific capacitance of 485.6 F g^–1 at a current density of 0.5 A g^–1 and an area capacitance as high as 4.23 F cm^–2 at a mass loading of 8.7 mg cm^–2. It also shows an excellent cycling stability with 88.9% capacity retention after 1000 cycles. It is speculated that the present low-cost novel hierarchical porous microspheres can serve as a promising electrode material for pseudocapacitors.