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　°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.　©　2017　Elsevier　Ltd