NOVEL SOLID-STATE ELECTROLYTES WITH IMPROVED ELECTRONIC PROPERTIES AS HYBRID IONICALLY CONDUCTING BATTERY MATERIALS

Abstract

As global energy consumption moves away from fossil fuel sources to alternative energy, the concern for energy storage is paramount. Through lithium ion batteries (LIBs), secondary battery storage has been secured for both large applications of electric vehicles, solar storage, and smaller items like personal cell phones and laptops. However, LIBs use flammable liquid electrolytes and due to engineering defects or dendritic short-circuits have the potential to swell, catch on fire, or even explode because of the volatile organic solvents within the battery. In the pursuit of new commercial lithium ion battery technologies that are safe, nonflammable, and highly conductive, solid-state electrolytes (SSE) are promising candidates for these critical innovations. To achieve SSEs with electrochemically and functionally desirable properties such as ease of manufacturing, good adherence to electrodes, and high ionic conductivities, continued efforts are devoted to improving electrolyte materials. The two main electrolyte types of interest are polymer electrolytes and ceramic electrolytes. Although polymer electrolytes have desirable physical flexibility to form good contact with electrode surfaces, they continually suffer from low ionic conductivities comparatively. Meanwhile ceramic electrolytes have high ionic conductivities (especially high cationic conductivities) but suffer from both poor electrode contact and brittleness. Single-ion conductive materials (like most ceramic conductors) are necessary to increase lifetime performance of batteries. An avenue to access these necessary attributes in LIB-SSEs is explored through novel boron-containing polymers and polymer-ceramic hybrids with the focus to synthesize a material with a high lithium transference number. By exploiting the Lewis basic nature of borane centers to form negatively charged polymer backbones, novel solid-state electrolytes were synthesized with the goal of creating only cation-conductive polymer networks by incorporating the anionic component within the polymer matrix. The synthesis, chemical and electrochemical characterization of these types of polymers and polymer-ceramic hybrids are analyzed by various techniques including x-ray diffraction, thermal gravimetric analysis, nuclear magnetic spectroscopy, gel permeation chromatography, electrochemical impedance spectroscopy and lithium transference number characterization.