Improved capacitors containing novel electrodes are described. One electrode composition comprises mixed metal oxides of the transition metals nickel and cobalt in a molar ratio of 0.5:1 or greater, and optionally containing a binder and carbon nanotubes. The resulting capacitors can be characterized by superior properties including higher specific capacitance values at higher voltage scan rates than the prior art. Methods of forming the electrodes that produce superior results are also described.