Abstract : Sol-gel method which provides better electrochemical and physiochemical properties compared to the solidstate method was used to synthesize the material of LiFeyMn2-yO4. Fe was substituted to increase the structural stability so that the effects of the substitution amount and sintering temperature were analyzed. XRD was used for the structural analysis of produced material, which in turn, showed the same cubic spinel structure as LiMn2O4 despite the substitution of Fe3+. During the synthesis of LiFeyMn2-yO4, as the sintering temperature and the doping amount of Fe(y = 0.05, 0.1, 0.2)were increased, grain growth proceeded which in turn, showed a high crystalline and a large
grain size, certain morphology with narrow specific surface area and large pore volume distribution was observed. In order to examine the ability for the practical use of the battery, charge-discharge tests were undertaken. When the substitution amount of Fe3+ into LiMn2O4 increased, the initial discharge capacity showed a tendency to decrease within the region of 3.0~4.2 V, but when charge-discharge processes were repeated, other capacity maintenance properties turned out to be outstanding. In addition, when the sintering temperature was 800~850째C, the initial capacity was small but showed very stable cycle performance. According to EVS(electrochemical voltage spectroscopy) test,
LiFeyMn2-yO4(y = 0, 0.05, 0.1, 0.2) showed two plateau region and the typical peaks of manganese spinel structure when the substitution amount of Fe3+ increased, the peak value at about 4.15 V during the charge-discharge process showed a tendency to decrease. From the previous results, the local distortion due to the biphase within the region near 4.15 V during the lithium extraction gave a phase transition to a more suitable single phase. When the transition was derived, the discharge capacity decreased. However the cycle performance showed an outstanding result.
Key words : Lithium manganese oxide, Electrochemical voltage spectroscopy, Capacity fading.