We studied romanechite, (2×3) 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 Ba0.18MnO2.10·0.42H2O. We obtained a first discharge capacity of 120mAhg−1 (energy density 264mWhg−1). The capacity decreased with cycling. We examined the thermal behavior of this material, revealing its high thermal stability.