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NEW SOLID AND LIQUID ELECTROLYTES FOR LITHIUM RECHARGEABLE BATTERIES
Title
NEW SOLID AND LIQUID ELECTROLYTES FOR LITHIUM RECHARGEABLE BATTERIES
Creator
Mei, Xinyi
Date
2016, 2016-12
Description
Currently, rechargeable lithium batteries are widely used in our consumer electronic products, including cell phones, laptop computers, and...
Show moreCurrently, rechargeable lithium batteries are widely used in our consumer electronic products, including cell phones, laptop computers, and cameras and so on. They have extraordinary potential for application in electric and hybrid electric vehicles by their high energy and power density[1]; however, the major challenges include the higher cost, safety issues related to the solvents and conductibility at lower temperatures are still waiting to be fixed. In this Ph.D. thesis, two types of rechargeable lithium batteries: lithium-ion batteries and lithium-sulfur batteries are discussed. Two different approaches are presented, in the direction of achieving an enhanced electrolyte system for rechargeable lithium batteries. One approach is based on the conventional poly (ethylene oxide) (PEO)-based solid polymer electrolyte (SPE) system. The key feature of this approach is the preparation of nanoparticle lithium salts (NPLS) and low lattice energy fluorinated di-lithium salts. The ionic conductivities of these PEO-based SPEs were markedly improved, due to a decrease in the glass transition temperature (Tg) of the polymer. For lithium-sulfur (Li-S) batteries, the polysulfide shuttle (PSS), caused by the dissolution of cathode polysulfide intermediates into the electrolyte, has delivered a mortal blow to nearly every attempt at obtaining a viable Li-S battery. So, another approach involved the strategic design and synthesis of a series of room temperature ionic liquids (RTILs) to prevent PSS: i) Three series of di-cationic ionic liquids (DILs) are synthesis and characterized. DILs-based electrolytes displayed excellent properties, such as non-flammability, high electrochemical stability and thermal stability. ii) Twelve new asymmetric fluorinated RTILs (FRTILs) were also introduced. The FRTILs based electrolytes showed even better properties than DILs-based electrolytes.
Ph.D. in Chemistry, December 2016
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SYNTHESIS AND INVESTIGATION OF NOVEL CATHODE MATERIALS FOR SODIUM ION BATTERIES
Title
SYNTHESIS AND INVESTIGATION OF NOVEL CATHODE MATERIALS FOR SODIUM ION BATTERIES
Creator
Sawicki, Monica
Date
2015, 2015-12
Description
Environmental pollution and eventual depletion of fossil fuels and lithium has increased the need for research towards alternative electrical...
Show moreEnvironmental pollution and eventual depletion of fossil fuels and lithium has increased the need for research towards alternative electrical energy storage systems. In this context, research in sodium ion batteries (NIBs) has become more prevalent since the price in lithium has increased due to its demand and reserve location. Sodium is an abundant resource that is low cost, and safe; plus its chemical properties are similar to that of Li which makes the transition into using Na chemistry for ion battery systems feasible. In this study, we report the effects of processing conditions on the electrochemical properties of Na-ion batteries made of the NaCrO2 cathode. NaCrO2 is synthesized via solid state reactions. The as-synthesized powder is then subjected to high-energy ball milling under different conditions which reduces particle size drastically and causes significant degradation of the specific capacity for NaCrO2. X-ray diffraction reveals that the lattice distortion has taken place during high-energy ball milling and in turn affects the electrochemical performance of the cathode material. This study shows that a balance between reducing particle size and maintaining the layered structure is essential to obtain high specific capacity for the NaCrO2 cathode. In light of the requirements for grid scale energy storage: ultra-long cycle life (>20,000 cycles and calendar life of 15 to 20 years), high round trip efficiency (> 90%), low cost, sufficient power capability, and safety; the need for a suitable cathode materials with excellent capacity retention such as Na2MnFe(CN)6 and K2MnFe(CN)6 will be investigated. Prussian blue (A[FeIIIFeII (CN)6]•xH2O, A=Na+ or K+) and its analogues have been investigated as an alkali ion host for use as a cathode material. Their structure (FCC) provides large ionic channels along the <100> direction enabling facile insertion and extraction of alkali ions. This material is also capable of more than one Na ion insertion per unit formula which holds great promise in increasing the energy density of the NIB. The electrochemical performance of the cathode material will be analyzed using cyclic voltammetry, and galvanostatic charge/discharge investigation.
Ph.D. in Materials Science and Engineering, December 2015
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