Manganese oxide and carbon hybrid materials have attracted intensive research attention as advanced electrode materials for energy storage. Herein, starting form metal-organic frameworks (MOFs), the nanocomposites of mixed-valent manganese oxide nanoparticles in-situ grown on ultrathin carbon sheets (MnOx-CSs nanocomposites) have been synthesized via a simple method. Benefiting from the unique structural merits, the nanocomposite obtained at 600 degrees C (MnOx-CSs-600) exhibits excellent performance for both supercapacitors (SCs) and lithium-ion batteries (LIBs). A high specific capacitance of 220 F g(-1) is achieved at the current density of 1 A g(-1). An asymmetric supercapacitor (ASC) based on the MnOx-CSs-600 nanocomposite cathode and activated carbon anode exhibits a high energy density of 27.5 W h kg(-1) at the power density of 225 W kg(-1). Moreover, the MnOx-CSs-600 nanocomposite displays a high reversible capacity of 1217.7 mA h g(-1) at 200 mA g(-1) after 160 cycles as an anode material for LIBs. Remarkably, the discharge capacity is still as high as 612.1 mA h g(-1) even at high current density of 2000 mA g(-1), indicating good rate capability. This synthetic strategy is quite simple, cost-effective and environmental friendly, which is highly promising for scaled-up production. (C) 2017 Elsevier Ltd. All rights reserved.