IMPROVING ELECTROLYTES FOR LITHIUM-ION AND LITHIUM OXYGEN BATTERIES

Abstract

There is an ever increasing demand for fossil fuels. Lithium ion batteries (LIBs) can effectively reduce the production of greenhouse gases and lessen the need for fossil fuels. LIBs also have great potential in electric vehicle applications as an alternative to petroleum modes of transportation. Understanding the chemical reactions between the electrolyte and electrodes in LIBs is very crucial in developing batteries which can work over a wide temperature range and also give a wide potential window. The Solid Electrolyte Interface (SEI), formed by the reduction of solvent molecules on the surface of electrodes, is an important component of LIBs. The SEI is very essential to the performance of LIBs. One electron reduction pathway products of solvent molecules was investigated using lithium-naphthalenide. Methylene ethylene carbonate, a high temperature additive has been synthesized and its performance has been tested at 60oC. Lithium-Oxygen batteries have an energy density ten times greater than that of LIBs. However, lithium-oxygen batteries have rechargability problems associated with them. The most common electrolyte used in this type of batteries is LiPF6 in carbonate or ether based solvents. LiPF6 inherently decreases electrolyte stability, since LiPF6 can undergo thermal dissociation into PF5 and LiF. PF5 being a strong Lewis acid, can react with electron rich species. The thermal decomposition reactions of LiPF6 based electrolytes are studied in detail with regard to LIBs. The comprehensive study has been conducted on the thermal degradation of several electrolyte systems in the presence of Li2O2.