A wide range of manganese oxides is under study for possible use as the cathode of high energy density batteries. The spinel, LiMn2O4, although the most studied has a relatively low energy density and appears unstable under charge. This review emphasizes non-spinel oxides, in particular those with layer ed or tunnel structures that offer enhanced behavior in Lithium ion and lithium polymer cells. A major focus is on stabilizing these manganese oxide structures against conversion to the spinel phase.