Arrays of manganese oxide nanowires were electrodeposited into anodized alumina membranes. These nanowire arrays were investigated in terms of their structural and electrochemical properties as cathodes for high energy and high power density Li ion batteries. The nanowire arrays were assembled with a Li counter electrode and non-aqueous electrolyte to form secondary batteries. These cells were capable of multiple charge/discharge cycles, with a cathode specific capacity of approximately 300mAh/g. Though the cathodes were fabricated without any binder or conductive additives, the electrodes could be discharged at current densities up to 0.1mA/cm2 before the onset of any significant polarization.