Mesoporous manganese oxides (MnO2) microspheres were synthesized by the first chemical deposition of manganese carbonate (MnCO3) precursors at room temperature and followed by the low-temperature calcinations under 300,350 and 400 degrees C. The obtained MnO2 materials exhibit the Akhtenskite type MnO2 crystalline microstructures and the microspherical morphologies with the diameter of about 1 mu m. The as-synthesized MnO2 microspheres under 300 degrees C exhibit the largest specific area (240.5 m(2) g(-1)) and the optimal mesopore volume (0.231 cm(3) g(-1)) than the other two samples under 350 and 400 degrees C (111.4, 106.3 m(2) g(-1); 0.055, 0.021 cm(3) g(-1)), which contribute to the optimal electrochemical performances for supercapacitors. Moreover, the as-synthesized MnO2 microspheres under 300 degrees C possess the highest tap density (1.156 g cm(-3)) than the other two samples (1.126, 1.043 g cm(-3)), leading to the more feasibility for practical applications in supercapacitors. The as-fabricated MnO2 electrode exhibits a high specific capacitance (129 F g(-1) at 0.25 A g(-1)) and high-rate capability (68 F g(-1) at 4A g(-1)). The as-assembled activated carbon (AC)//MnO2 hybrid capacitor exhibits a wide working voltage (1.8V), high power and energy densities (2197 W kg(-1) and 12.8W h kg(-1) at 4 A g(-1)), excellent cycling behavior (94.3% capacitance retention after 5000 cycles at 1 A g(-1)), and excellent capacitance recovery performances under different rates (0.25-4 A g(-1)) for tested 4500 cycles, indicating the promising prospective of the easily fabricated mesoporous MnO2 microspheres for practical applications in supercapacitors. (C) 2013 Elsevier Ltd. All rights reserved.