Different from a conventional solid state reaction, a hydrothermal reaction mechanism is very difficult to illuminate and sometimes it remains undisclosed. Making an attempt to understand the hydrothermal phase formation process of o-LiMnO2 obtained between the reaction of spinel type Mn3O4 precursor and LiOH aqueous solution, the possible reaction route was postulated and experimentally testified. Firstly, the selective dissolution of Mn2+ from the tetrahedral site of [Mn-II](4a)(tet)[Mn-2(III)](8d)O-oct(4), which is considered as to be an ionic exchange reaction with Li+, and an additional Li+ intercalation into the host structure of precursor would give rise to the formation of meta-stable Li(2)Mn(2)O4 ([Li-1](4a)(tet)[Li-1](8c)(oct)[M-1](4a)(tet)[Li-1](8c)(oct)[Mn-2(III)]( 8d)O-oct(4))- Secondly, the phase would be simultaneously transformed to thermodynamically stable o-LiMnO2 phase under hydrothermal state during hydrothermal reaction. Through the above reaction process, the solid solution range of o-LiCoxMn1-xO2 was as large as x <= 0.14. and that of o-LiFexMn1-xO2, was x < 0.05. Co doped o-LiMnO2 has higher capacity and good cyclability upon cycling, being substantially more stable to cycle than the unsubstituted and Fe doped materials. (c) 2005 Elsevier B.V. All rights reserved.