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Title

ELECTROCHEMICAL, TRANSPORT AND THERMAL INVESTIGATION OF NOVEL ELECTROLYTES AND ELECTRODES FOR LITHIUM-ION AND MAGNESIUM-ION BATTERIES

Creator

Benmayza, Aadil

Date

2014, 2014-12

Description

Energy conversion and energy storage are becoming indispensable in today’s society due to the increased demand for immobile and mobile power....
Show moreEnergy conversion and energy storage are becoming indispensable in today’s society due to the increased demand for immobile and mobile power. Cathode material is considered as the only source of energy in the electrochemical cell for secondary battery and thus the quantity of energy of the battery is largely determined by the type of the cathode’s chemistry and its amount used as well. Electrolyte has also a significant impact on the electrochemical performance of the battery. Its properties such as ionic conductivity and transference number play a substantial role in the transport of energy between the cathode and the anode. Moreover, the electrolyte can also limit the accessibility of the active charged ions into the active material through the formation of a Solid Electrolyte Interface (SEI). In addition to the importance of energy, safety is another critical element in the determination of the battery’s quality. Cathode material and non-aqueous electrolyte are two major dimensions of the safety in the design of secondary battery. For instance, in the presence of heat (due to thermal, mechanical, or electrical abuse), the electrolyte can ignite fire if the cathode material releases the oxygen. Therefore, the cathode materials and electrolytes are both central factors in the determination of battery energy and safety. Nowadays, lithium-ion batteries are widely used as power source in many applications; however, their maximum energy density (400Wh/Kg) is not sufficient enough to meet the demands of high power applications such as electric vehicles owing to the limited driving range caused by current lithium-ion batteries. Furthermore, safety concerns have been raised after several incidents have been reported recently. Therefore, improving the safety of lithium-ion battery systems through the formulation of non-flammable electrolytes and synthesizing stable electrodes are highly required for high thermal stability. In contrast, fulfilling the long driving range requires other battery systems that provide higher energy density. The large energy density of Mg metal (3832 mAh/cm3) opens a new horizon toward future potential energy storage system, which is a very promising candidate to overcome the long driving range issue and thus needs to be investigated for its potential use as rechargeable battery. In this present thesis, thermal stability of lithium-ion cells is examined through the use of Fluoro Ethylene Carbonate (FEC) as non-flammable co-solvent with Ethylene Carbonate (EC) on lithium-nickel-cobalt-aluminum-oxide cathode (LiNi0.8Co0.15Al0.05O2). This cathode chemistry was deliberately chosen because of its low thermal stability due to the oxidation of Ni+3 to Ni+4 upon charging. Additionally, optimization of the cathode composition (active material, conducting agent, binder) was examined for high energy and power. Lithium iron phosphate (LiFePO4) was chosen for this study because of its high thermal stability against the liberation of oxygen. Electrolytic properties of a magnesium organohaloaluminate electrolyte were investigated in order to understand their role and effect on the magnesium deposition process. Electrochemical and thermal study of bismuth material as a potential negative electrode for magnesium-ion cell under the use of magnesium organohaloaluminate electrolyte was also performed. Moreover, a thermal modeling was performed through the use of Isothermal-Micro-Calorimeter (IMC) technique to identify the sources of heat released during the magnesiation and demagnesiation of bismuth electrode.
Ph.D. in Chemical Engineering, December 2014
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