Dissertation
Dissertation > Industrial Technology > Electrotechnical > Independent power supply technology (direct power) > Battery

Preparation and Study on Properties at Elevated Temperature of Spinel LiMn2O4Cathode Materials

Author ChenFei
Tutor WangZhenBo
School Harbin Institute of Technology
Course Chemical Engineering and Technology
Keywords cathode material LiMn2O4 solidstate method elevated temperatureproperty doping
CLC TM912
Type Master's thesis
Year 2013
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This study focused on advancing the industrialization process of lithium ion batterycathode material spinel LiMn2O4to speed up the energy storage and power lithium-ionbatteries’ development. In this study, industrial raw materials had been employed tosynthesize spinel LiMn2O4, and committing to improving its elevated temperatureperformance.LiMn2O4has a relatively poor cycle performance about the capacity, especially atelevated temperature. Employing lithium carbonate and electrolytic manganese dioxideas raw material to synthesize LiMn2O4by solidstate method in this study, and conducteda more detailed study of the solid-phase method process parameters to identify the mainreason for its poor cycling performance. By doping, we synthesized LiMn2O4powderswith better performance. Obtained LiMn2O4sample showed well-defined spinel phase,good crystallinity and uniform particle distribution at the optimized synthetic conditions.At the charge-discharge rate of1C, its initial discharge capacities are115mAh/gand108mAh/g at room temperature and elevated temperature, after200cycles, thecapacity retention are92%and80%.LiMn2O4had a poor performance at elevated temperature, so it had been doped. Inthe experiments, LiMn2O4had been respectively doped fluorine, aluminum, cobalt ionwith different doping amount. The experimental results show that the initial dischargecapacity has declined after single ion doped. But, it obviously raised the cycleperformance at elevated temperature after doping aluminum ion. When the aluminumdoping amount is5%, the sample has a better performance, the initial dischargecapacities at1C rate are107mAh/g and101mAh/g at room temperature and elevatedtemperature, after200cycles, the capacity retention are94%and88%. In order to solvethe problem of declining initial capacity after single-ion doped, mixed ions had beendoped in the experiments. Fluorine and aluminum, fluorine and cobalt, fluorine,aluminum, and cobalt, three kinds of mixed ions had been respectively doped and theresults had been compared. The data shows doping mixed ions had been significantlyimproved the initial discharge capacity contrast to doping single ion, but the capacityretention declined at elevated temperature. The doping amount of fluorine and cobaltwere both1%shows a better performance, the initial discharge capacities at1C rate are both118mAh/g at room temperature and elevated temperature, after200cycles, thecapacity retention are90%and76%.Mixed ion doping not achieved the desired effect, may be the uneven mixing rawmaterials in the solid phase caused capacity retention declined, so wet mixing methodhad been employed. Comparing the effect of respectively doping boron, fluorine andcobalt, the results show the wet mixture cobalt-doped has a preferably performance.Doped with5%cobalt, the initial discharge capacities significantly improved, at1Crate, they are123mAh/g and121mAh/g at room temperature and elevated temperature,after200cycles, the capacity retention are92%and79%.At last, the rate performanceof LiMn2O4had been studied. Increasing the charge-discharge rate, the wet-mixing5%cobalt-doped and undoped LiMn2O4both show an excellent rate performance, thedischarge capacity and discharge plateaudecline are less, and the discharge plateau arestable at different rate.

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