Synthesis And Modification Of Spinel LiMn₂O₄by Pyrolysis Of Manganese Carbonate

Spinel LiMn2O4is considered as one of the most promising cathode material for lithium secondary batteries because of its abundance of manganese resource, low cost and environmental harmlessness. In this paper, spinel LiMn2O4was synthesized by pyrolysis of manganese carbonate, and Al3+, Mg2+were doped during the synthesis process of MnCO3to get LiAlxMn2xO4and LiMgxMn2-xO4(x=0.01,0.02,0.03,0.05,0.1). The cost was reduced and cycling performance of the material was improved. The morphology, crystal structure and electrochemical performance were analyzed by XRD, SEM, ICP, CV and electrochemical test.The influence of the reaction temperature, reactant concentration, stirring intensity, feeding rate and ageing time during the synthesis process of MnCO3was systematically investigated. The effect of the heating time and pyrolysis atmosphere during the pyrolysis of manganese carbonate was also analyzed. The LiMn2O4synthesized at the optimum condition shows fine spinel structure with uniform particle size and particle distribution. The first discharge capacity of LiMn2O4is127.6mAh/g, the initial charge-discharge efficiency is88.9%and the capacity retention during100cycles at1C is80.1%.The Al3+, Mg2+doped LiAlxMn2-xO4and LiMgxMn2-xO4via pyrolysis of manganese carbonate were synthesized. There is no apparent change for the XRD patterns of the doped MnCO3precursor and lithium manganese oxides. With the increase of the doping amount, the particle size of LiAlxMn2-xO4increases while that of LiMgxMn2-xO4decreases. With the doping of Al3+, the first discharge capacity of LiAlxMn2-xO4decreases to certain extent. But LiAlxMn2-xO4electrode exhibits superior cycling performance. The capacity retention increases from80.2%(for LiMn2O4) to95.9%(for LiAl0.05Mn1.95O4) at room temperature and from72.2%to90.7%at elevated temperature during100cycles at1C. Comparing to LiAlxMn2-xO4, LiMgxMn2-xO4shows smaller fading rate for the first discharge capacity and the cycling performance is improved. The first discharge capacities of LiMg0.01Mn1.95O4at room and elevated temperature (55℃) are113.2mAh/g and105.95mAh/g while the capacity retentions are85%and82.4%, respectively.