Síntese e caracterização de titanato de sódio dopado com lítio para eletrólitos de estado sólido

Abstract

The world has undergone major changes in new technologies, especially in the electronics industry, the insertion of hybrid and electric vehicles and the search for renewable energy sources. Demand for energy storage devices has grown exponentially. Lithium batteries are currently highlighted for this purpose, but the price of lithium and its limited abundance, leads the scientific community to look for alternatives in other chemical elements, such as sodium. Na+ ion-based materials have potential use in solid state batteries due to their ion diffusion ability which leads to high values of energy density and power. Thus, many studies have been developed from different synthesis methods, precursors and element combinations, enabling the use of these materials as electrodes and solid-state electrolytes in different types of energy storage devices. Microwaveassisted hydrothermal synthesis was used to synthesize doped sodium titanate with different lithium concentrations according to the stoichiometric formula: Na2-xLixTi3O7 (x = 0.0; 0.01; 0.05; 0.15; 0.25; 0.35 and 0.50). For the characterization of the samples different techniques were used. Among them: X-ray diffraction, Archimedes method and complex impedance spectroscopy. For the sample doped with 1% lithium ions (1% Li+) no appreciable structural change was obtained and Na2Ti3O7 was identified as the majority phase. From doping with 5% Li+, the formation of a second phase identified as NaLiTi3O7 was verified. The samples doped with 35 and 50% Li+ presented the NaLiTi3O7 phase as the majority. Doping until 25% Li+ contributed to an increase in electrical conductivity compared to pure sodium titanate (0% Li+). For samples doped with 35% and 50% Li+, a decrease in the material electrical conductivity of the material was obtained. The highest conductivity value achieved was around 10-4 S/m for the 5% Li+ sample. The electrical conductivity values achieved in this work (between 10-4 to 10-6 S/m) make them possible materials for use in solid-state electrolyte.