Nanostructured lithium manganese oxide cathodes obtained by a reduction of aqueous lithium permanganate with hydrogen

Nanostructured lithium manganese oxides have been synthesized by reducing aqueous lithium permanganate with hydrogen gas at 60degreesC in the presence and absence of lithium hydroxide followed by firing in vacuum at 250degreesC. The oxides have been characterized by wet-chemical analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and Brunauer-Emmett-Teller surface area and density measurements. The Li/Mn ratio in the samples increases from 0.47 to 1.09 with increasing amount of lithium hydroxide in the synthesis medium. X-ray diffraction indicates the sample to have spinel- or Li2MnO3-like structures. The samples exhibit high capacities of 250-300 mAh/g at 4-1.5 V with good rate capability in lithium cells. The capacity retention and the charge efficiency of the cathodes improve with increasing lithium content. (C) 2003 The Electrochemical Society.