Oxo ions (MO_4)~(n-)(M chemical bounds V, Cr, Mn and Mo) have been reduced in aqueous solutions with potassium borohydride to obtain the binary oxides MO_(2+ delta ). While the vanadium and manganese oxides are nanocrystalline, the chromium and molybdenum oxides are amorphous. The nanocrystalline VO_2 having a metastable structure and the amorphous CrO_2 and MoO_(2.3) transform to the thermodynamically more stable phase upon heating above 300-400 deg C. These metastable oxides after heating in vacuum at 200-300 deg C to remove water show good electrode performance in lithium cells. VO_2, CrO_2 and MoO_(2.3) show a reversible capacity o f, respectively, 290 mAh/g in the range 4-1.5 V, 180 MAh/g in the rnage 3.3-2.3 V, and 220 mAh/g in the range 3-1 V. MnO_2 obtained by this process does not show good elecrode properties.
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