We studied romanechite, (2 x 3) tunnel type manganese dioxide, as a positive electrode material for rechargeable lithium batteries. We synthesized the sample by soft chemical techniques, and its chemical composition was Ba0.18MnO2.10.0-0.42H(2)O. We obtained a first discharge capacity of 120 mAh g(-1) (energy density 264 mWh g(-1)). The capacity decreased with cycling. We examined the thermal behavior of this material, revealing its high thermal stability.