PREPARATION OF CATHODE MATERIALS FOR LITH IUM BATTERIES BY MELT IMPREGNATION METHOD .4. PREPARATION OF STOICHIOMETRIC SPINEL LIMN2O4 AND NONSTOICHIOMETRIC SPINEL LIXMN2O4 AND ITS ELECTROCHEMICAL-BEHAVIOR

The spinel LixMn2Oz (z>4) has been prepared from MnO2 and LINO(3)(or L IOH) under N-2 or air by melt impregnation method. Nitrogen gas accele rates the release of excess organ from organ excess LiMn2Oz, causing t he formation of LiMn2O4. Stoichiometric spinel LiMn2O4 with initial ca pacity of 130 mAh . g(-1) at c.d. 0.4 mA . cm(-2) is prepared from IC. 12(lnternational Common Manganese Dioxide No. 12)-LiOH by two step be ating, 470 degrees C, 12 h in air and 700 degrees C, 24 h in M(2). It would be gradually transformed during the cycling to new compounds wit h the capacity of ca, 110-120 mAh . g(-1) , which is higher than that of oxygen rich spinel Li1.04Mn2O4.14 with excellent cyclability. The L i1.04Mn2O4.14 shows one quasi-S type discharge curve. The electrochemi cal reaction of it is composed of two homogeneous reactions with nearl y same potentials with those of LiMn2O4 with a homogeneous and a heter ogeneous reactions. Excellent cyclability of it would be due to the co ntinuous and small cell volume change during the cycling.