The transition metal oxides have a wide spectrum of physical and chemical functionalities, useful for many potential applications in energy technologies. However, the underlying physical mechanisms have been still unclear whether performance is intrinsic to materials themselves or attributed to extrinsic factors. The synthesis of phase pure materials has been a challenging task because their polymorphs are closely related to each other in a thermodynamic framework. Here, we report epitaxial stabilization of single crystalline oxides for energy applications and investigate their intrinsic functionalities. First, our epitaxial VO2(B) and TiO2(B) films offer excellent long-term stability with extremely high capacity for Li ion battery electrode. Second, we design and create unique cell geometry of micrometer-thick epitaxial nanocomposite films which contain yttria-stabilized ZrO2 (YSZ) nanocolumns. The ion conductivity of these nanocolumns is enhanced by over two orders of magnitude compared to plain YSZ films, showing the strong practical potential of these nanostructured films for use in much lower operation temperature ionic devices. Our successful epitaxy of oxides will open the door to study their fundamental properties for potential energy applications and understand their intrinsic physics.