The Synthesis and Characterization of Ionic Liquids for Alkali-metal Batteries and a Novel Electrolyte for Non-humidified Fuel Cells
Author | : Telpriore G. Tucker |
Publisher | : |
Total Pages | : 279 |
Release | : 2014 |
ISBN-10 | : OCLC:903902788 |
ISBN-13 | : |
Rating | : 4/5 (88 Downloads) |
Book excerpt: This thesis focused on physicochemical and electrochemical projects directed towards two electrolyte types: 1) class of ionic liquids serving as electrolytes in the catholyte for alkali-metal ion conduction in batteries and 2) gel membrane for proton conduction in fuel cells; where overall aims were encouraged by the U.S. Department of Energy. Large-scale, sodium-ion batteries are seen as global solutions to providing undisrupted electricity from sustainable, but power-fluctuating, energy production in the near future. Foreseen ideal advantages are lower cost without sacrifice of desired high-energy densities relative to present lithium-ion and lead-acid battery systems. Na/NiCl2 (ZEBRA) and Na/S battery chemistries, suffer from high operation temperature (>300C) and safety concerns following major fires consequent of fuel mixing after cell-separator rupturing. Initial interest was utilizing low-melting organic ionic liquid, [EMI+][AlCl4-], with well-known molten salt, NaAlCl4, to create a low-to-moderate operating temperature version of ZEBRA batteries; which have been subject of prior sodium battery research spanning decades. Isothermal conductivities of these electrolytes revealed a fundamental kinetic problem arisen from "alkali cation-trapping effect" yet relived by heat-ramping>140C. Battery testing based on [EMI+][FeCl4-] with NaAlCl4 functioned exceptional (range 150-180C) at an impressive energy efficiency>96%. Newly prepared inorganic ionic liquid, [PBr4+][Al2Br7-]:NaAl2Br7, melted at 94C. NaAl2Br7 exhibited super-ionic conductivity 10-1.75 Scm-1 at 62C ensued by solid-state rotator phase transition. Also improved thermal stability when tested to 265C and less expensive chemical synthesis. [PBr4+][Al2Br7-] demonstrated remarkable, ionic decoupling in the liquid-state due to incomplete bromide-ion transfer depicted in NMR measurements. Fuel cells are electrochemical devices generating electrical energy reacting hydrogen/oxygen gases producing water vapor. Principle advantage is high-energy efficiency of up to 70% in contrast to an internal combustion engine