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Designing and Thermal Analysis of Safe Lithium Ion Cathode Materials for High Energy Applications

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dc.contributor.advisor Wang, Lin-Shu en_US
dc.contributor.advisor Longtin, Jon en_US
dc.contributor.author Hu, Enyuan en_US
dc.contributor.other Department of Mechanical Engineering. en_US
dc.date.accessioned 2017-09-20T16:50:16Z
dc.date.available 2017-09-20T16:50:16Z
dc.date.issued 2015-12-01
dc.identifier.uri http://hdl.handle.net/11401/76437 en_US
dc.description 161 pg. en_US
dc.description.abstract Safety is one of the most critical issues facing lithium-ion battery application in vehicles. Addressing this issue requires the integration of several aspects, especially the material chemistry and the battery thermal management. First, thermal stability investigation was carried out on an attractive high energy density material LiNi0.5Mn1.5O4. New findings on the thermal-stability and thermal-decomposition-pathways related to the oxygen-release are discovered for the high-voltage spinel LixNi0.5Mn1.5O4 (LNMO) with ordered (o-) and disordered (d-) structures at fully delithiated (charged) state using a combination of in situ time-resolved x-ray diffraction (TR-XRD) coupled with mass spectroscopy (MS) and x-ray absorption spectroscopy (XAS). Both fully charged o--LixNi0.5Mn1.5O4 and d-LixNi0.5Mn1.5O4 start oxygen-releasing structural changes at temperatures below 300 °C, which is in sharp contrast to the good thermal stability of the 4V-spinel LixMn2O4 with no oxygen being released up to 375 oC. This is mainly caused by the presence of Ni4+ in LNMO, which undergoes dramatic reduction during the thermal decomposition. In addition, charged o-LNMO shows better thermal stability than the d-LNMO counterpart, due to the Ni/Mn ordering and smaller amount of the rock-salt impurity phase in o-LNMO. Newly identified two thermal-decomposition-pathways from the initial LixNi0.5Mn1.5O4 spinel to the final NiMn2O4-type spinel structure with and without the intermediate phases (NiMnO3 and α-Mn2O3) are found to play key roles in thermal stability and oxygen release of LNMO during thermal decomposition. In addressing the safety issue associated with LNMO, Fe is selected to partially substitute Ni and Mn simultaneously utilizing the electrochemical activity and structure-stabilizing high spin Fe3+. The synthesized LiNi1/3Mn4/3Fe1/3O4 showed superior thermal stability and satisfactory electrochemical performance. At charged state, it is able to withstand the temperature as high as 500°C without observable oxygen release. It shows comparable cyclability performance to the LNMO material with better rate capability. The undiminished high voltage capacity is due to the electrochemical activity of Fe in the system. Fe also plays the key role of stabilizing the system at Fe3O4 type spinel phase against further phase transformation to the rock salt phase, accounting for the superior thermal stability of LiNi1/3Mn4/3Fe1/3O4. Thermal analysis of the lithium-ion battery indicates the key role of electric current in contributing to a thermal runaway. FLUENT simulation on a 10-cell battery shows that under fast discharging conditions, the temperature level can easily reach the threshold of malfunction and the battery temperature features a large distribution of 18°C. Simple air cooling is not effective enough in addressing the problem. Designed air cooling or liquid cooling is required for the normal operation of lithium-ion batteries in vehicles. en_US
dc.description.sponsorship This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. en_US
dc.format Monograph en_US
dc.format.medium Electronic Resource en_US
dc.language.iso en_US en_US
dc.publisher The Graduate School, Stony Brook University: Stony Brook, NY. en_US
dc.subject.lcsh Mechanical engineering en_US
dc.subject.other battery safety, electronic structure, in situ technique, lithium-ion battery, material design en_US
dc.title Designing and Thermal Analysis of Safe Lithium Ion Cathode Materials for High Energy Applications en_US
dc.type Dissertation en_US
dc.mimetype Application/PDF en_US
dc.contributor.committeemember Hwang, David en_US
dc.contributor.committeemember Yang, Xiao-Qing en_US
dc.contributor.committeemember Wang, Jia. en_US

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