Study On The Preparation Of LiMn₂O₄by Rotor-Stator Reactor

In this paper, α-MnO2and β-MnO2were prepared utilizing low valence state MnSO4·H2O and (NH4)S2O8as the starting materials via hydrothermal method. MnO2of different crystal type were prepared by controlling oxidant, reactant concentration and reaction temperature. LiMn2O4was hydrothermally synthesized by using MnO2as manganese source and LiOHH2O as lithium source. Preparation of LiMn2O4by rotor-stator reactor under the precondition determined above. The main contents are as follows:Synthesis of MnO2intermediate via hydrothermal method. The effect of (NH4)S2O8and KBrO3as oxidants on the synthesis of MnO2was studied. Furthermore, the effects of hydrothermal temperature and reactant concentration on the crystal form and morphology of MnO2was investigated to optimize the reaction conditions. Two types of crystal type and morphology of MnO2were successfully prepared.Synthesis of LiMn2O4via hydrothermal method. LiMn2O4particles were synthesized by using homemade MnO2as manganese source and LiOHH2O as lithium source. Reactant concentration, Li/Mn ratio, hydrothermal temperature and addition of ethanol were studied to synthesis LiMn2O4particles which were of high purity, high crystallinity and high dispersibility.It was found that a-MnO2has advangtages over (3-MnO2in the synthesis of LiMn2O4through characterizations of XRD, SEM, TEM, crystal structure analysis and electrochemical performance test. The particle size of LiMn2O4prepared by α-MnO2is about1μm. Initial discharge capacity is107.84mAh/g in the rate of0.1C. The discharge capacity is90.35mAh/g after100cycles and the capacity retention is about83.78%. The particle size of LiMn2O4prepared by β-MnO2is about500nm. First discharge capacity is98.41mAh/g in the rate of0.1C. The discharge capacity is74.93mAh/g after100cycles and the capacity retention is about74.93%.In this paper, for the first time, LiMn2O4was prepared by rotor-stator reactor. The effects of rotation rates of rotor-stator, charging sequence, charging speed, heating temperature and circulation volume on purity, crystal1in ity, morphology and electrochemical performance of LiMn2O4were studied. The optimum conditions are obtained, that is1ml/min,2240r/min,80℃,600ml/min. Results of electrochemical performance test:the first discharge capacity was118.75mAh/g, after100cycles, discharge capacity was98.44mAh/g, and the retention rate was82.9%in the rate of0.1C.