Anish Yerramilli M.S. Final Exam and Defense
Monday, August 13, 2012, 02:00 PM
M.E. Conference Room

Anish Yerramilli M.S. Final Exam and Defense 2pm, Monday, August 13th ME Conference Room Advisor: Susan James, Ph.D. Committee: Amy Prieto, Ph.D.; Mingzhong Wu, Ph.D. 

SYNTHESIS AND CHARACTERIZATION OF LITHIUM-ION CATHODE MATERIALS IN THE SYSTEM (1-x-y) LiNi0.8Co0.15Al0.05O2.xLi2MnO3.yLiCoO2 Abstract Energy storage technology has been dominated by lithium ion batteries, considered as the most promising technology with higher energy density compared to any other battery technologies. The market for lithium ion batteries has increased rapidly from 2007. Goals set by the U.S Department of Energy for hybrid electric vehicles have not been met by any of the existing cathode materials. The system (1-x-y) LiNi0.8Co0.15Al0.05O2.xLi2MnO3.yLiCoO2 is synthesized using a simple sol-gel synthesis. The materials LiNi0.8Co0.15Al0.05O2, Li2MnO3 and LiCoO2 were used as end points in a ternary composition diagram. Twenty eight cathode compositions spanning the entire ternary composition diagram were synthesized under the same conditions and characterized using X-ray diffraction (XRD) and an Arbin BT2000 battery testing system. XRD results showed a-NaFeO2 structure with a space group of R3m. The results from electrochemical testing revealed a wide range of electrochemical capacities and cyclabilities. The regions close to Li2MnO3 showed high capacities and cyclability. The material with composition Li1.5 Ni0.133Co0.358Al0.008Mn0.5 was having an initial discharge capacity of 216.3 mAh/g and retained this capacity even after multiple cycles in the voltage range of 4.6-2 V at a rate of C/15. Statistical analysis was done using SAS/STAT 9.2 with the ADX procedure to fit a general linear model with three linear terms and three two way interactions to map capacities and cyclabilities. This analysis was used to choose the composition with best capacity and cyclability. Inductively couple plasma (ICP) analysis was carried out on the chosen samples to find the error between calculated composition and the theoretical composition. XPS (X-ray photoelectron spectroscopy) was conducted for the chosen samples and the oxidation states of the elements were determined. The material with composition Li1.5 Ni0.133Co0.358Al0.008Mn0.5 was found to be the promising material for commercialization. Before going into the market additional changes like synthesis conditions and surface treatments should be conducted on the material.

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