| Recently, lithium ion batteries have been widely used in portable products, storageenergy of power station, electric vehicle, warship and many other devices. Therefore,numbers of scientific studies about the key compositions of lithium ion batteries havebeen reported, espacially on cathode materials. Among these cathode materials, spinelLiMn2O4is one of the most potential cathode materials in market development owingto its merits of inexpensiveness, easy preparation, environmental friendliness and goodsecurity. However, the cycling behavior of this material has been hindered by certainweaknesses such as the Jahn-Teller distortion, the solubility of manganese in organicelectrolyte, and the decomposition of electrolyte solution on the electrode. Thus, thepreparation of a well cycling performance cathode material (spinel LiMn2O4) by moltensalt method and ion doping was studied in this research.The MnCO3of fine particle size and well particle distribution was obtained vialiquid phase precipitation at the condition of solution0.8mol/L, pH=9, ageing for halfan hour whilst feeding. And then, the nanoscale Mn2O3obtained from calcinatingMnCO3was served as Mn source to prepare submicro spinel LiMn2O4by molten saltmethod mixed with Li2CO3and KCl. The calcination temperature and the calcinationtime were studied and analyzed as the crucial factors affecting the electricalperformance of LiMn2O4. The decomposition temperatures of the series of syntheticswere analyzed by TG/DTA, the phase compositions of the resultants were investigatedby XRD, and the morphologies of the final powders were studied by SEM. Besides, theelectrical properties of the spinel LiMn2O4were characterized by cell test station. Thestudy exhibited that the electrical property of the synthesized LiMn2O4performed thebest under the condition of calcinating at800℃for8h. Its initial charging anddischarging capacities were118.89mAh g-1and the attenuation rate of specific capacity after cycling for30times was5.85%.The study of the doping amounts of Fe3+into the cathode material of spinelLiMn2O4was carried out in this research as well. In this study, the electrical propertiesof different raw material ratio of LiFexMn2-xO4(x=0.02, x=0.05, x=0.10, x=0.15) wereinvestigated. The study showed the cycling performence improved obviously while thespecific capacity decreased somewhat when the spinel LiMn2O4doped with Fe3+.Among the doped resultants, LiFe0.05Mn1.95O4performed the best in electricalproperties, of which the initial charging and discharging capacities were98.91mAh g-1while the attenuation rate of specific capacity was1.51%which was distinctly betterthan the pure LiMn2O4. It was demonstrated that the cycling behavior could beimproved effectively when doped with Fe conducting the cycling tests at0.2C,0.5C,1C,2C and5C respectively. The tests showed the attenuation rates of cathode materialsdoped with Fe were evidently less than the non-doped counterparts, though they alldecreased increasingly with the elevating0.2C,0.5C,1C,2C,5C the rate performances.The study of the different doping amounts of F into the cathode material of spinelLiFe0.05Mn1.95O4-yFy(y=0.01, y=0.05, y=0.10, y=0.15) was also carried out in thisresearch. This study indicated that both the cycling behavior and specific capacity ofLiFe0.05Mn1.95O3.99F0.01performed comparatively well with the initial charging anddischarging capacities of114.9mAh g-1and the attenuation rate of specific capacityafter cycling for30times of2.06%which was less than non-doped with F-(5.85%).According to the researches, the cycling behavior and the charging and dischargingcapacities of spinel LiMn2O4can both get effectively improved by ions co-doping inthe preparation of this cathode material. |
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