Supercapacitor has been recognized as a very promising new energy storage device due to its high power density and long cycle life. Carbon materials, metal oxides and conductive polymers are three more commonly utilized electrode materials for supercapacitors. The combination of the cycling stability of graphene and high capacity of metal oxide provides the graphene/metal oxide composite superiors performance. Consequently, significant research interest has been directed into the research of the graphene/metal oxide composite. In this paper, we present a review on the research progress of the graphene/metal oxide composite for supercapacitor application in term of the types of metal oxides, grapheme structure and preparation methods. Furthermore, the optimum synthesizing conditions and an outlook of the developing trend for the graphene/metal oxide composite are summarized.

Contents
1 Introduction
2 MnO₂/graphene composites
2.1 Solvothermal (hydrothermal) method
2.2 Electrochemical deposition
2.3 Chemical reaction
2.4 Self-assembly method
3 RuO₂/graphene composites
3.1 Sol-gel method
3.2 Solvothermal (hydrothermal) method
4 NiO/graphene composites
4.1 Chemical precipitation
4.2 Solvothermal (hydrothermal) method
4.3 Other methods
5 Co₃O₄/graphene composites
5.1 Chemical precipitation
5.2 Solvothermal (hydrothermal) method
5.3 Other methods
6 ZnO/graphene composites
7 Other metal oxides
8 Binary metal oxides
9 Conclusion