Research On Preparation Of Manganate Cathode Materials For Lithium Batteries With Electrolytic Manganese Anode Slime

In the production of electrolytic manganese, it will inevitably produce a large numberof high rate of manganese anode slime at the anode area, because of the complexcomposition and structure, the anode slime is not used properly, most part is stocked ashazardous wastes or sold cheap, a small part is used for additives of steel-making. Thisresearch focused on electrolytic manganese anode slime, used XRF, FAAS, XRD,SEM-EDS and TG-DTA to describe its surface physical and chemical characteristics. Thenwe came up with the process Washing-Roasting-Leeching to remove the impurity in theanode slime. Roasting temperature, leaching agent and its concentration, solid-liquid ratio,leaching time and other factors were considered to study the removal rate of impurity.Besides, a preliminary study on the mechanism of lead removal was also carried out, thepurified anode slime was then used to prepare manganese acid lithium anode materials,whose structure and electrochemical properties were then analyzed. The results showed:This study used XRF and FAAS to analyze element content in anode slime, and thenanalyzed the source of each element, the results showed that the anode slime mainly hadMn, Pb, Ca, Se, Sr and some other elements, manganese content was47%on average, lead7.46%. Mn,Ca, Se and Sr in the anode slime were from the electrolyte while Pb was fromdissolution of anode plate.XRD analysis showed that possible phases of the anode slime were K2-xMn8O16,MnO2, PbMn8O16, Pb2Mn8O16, etc., and aslo MnO2in the slime had a mixed crystalstructure of α-MnO2,β-MnO2,γ-MnO2,δ-MnO2;SEM-EDS analysis indicated that the MnO2was deactivated due to package of impurity elements, and formed a typical colloidalsystem, existing as a kind of dense "mineral" phase;TG-DTA/DTG analysis showed thatduring the temperature of0~573℃, water in δ-MnO2lattice desorbed, during573~655℃, MnO2began to lose oxygen and turned into Mn2O3, free alkali(OH-) in δ-MnO2lattice reacted with manganese oxide with lower valence state and produced alkalinemanganese salt, during655~850℃, bond energy of Pb-O,Mn-O both changed; during900~1000℃Mn2O3lost oxygen and turned into Mn3O4.Anode slime under different roasting temperature were characterized by XRD andSEM-EDS, the result showed that during500~800℃, MnO2turned into Mn2O3, when roasting temperature was higher than900℃, Mn2O3turned into Mn3O4;SEM analysisshowed that when it was higher than800℃, the dense structure of anode slime wasbroken, providing an effective way to remove lead.In this paper, orthogonal experiment was applied to determine the optimaltechnological conditions of leaching process: the best agent was NH4Ac, and theconcentration was2mol/L, the time was6h, liquid-solid ratio was8:1.Under thiscondition, the product had the best crystallinity, and the purity of Mn2O3was higher than95%.The purified electrolysis manganese anode slime was used to synthase lithiummanganite, the anode materials, through high temperature solid phase synthesis. XRD andSEM analysis showed that the prepared sample was LiMn2O4with spinel structure withhomogeneous distribution; it was also Fd3m space group.The lithium manganite material was then used as positive electrode, lithium thenegative to make lithium battery. The electrochemical properties test indicated that theprepared anode material LiMn2O4has the first charge and discharge capacity of100~110mA·h/g.