Produção e caracterização de cerâmicas de Li0,5La0,5TiO3 e Na2Ti3O7 visando sua aplicação em bateria de estado sólido

Abstract

The rapid development of the electronics industry and the growing market for electric vehicles require the development of energy storage devices that are increasingly safe, efficient, lightweight, sustainable and cost-effective. In this sense, much emphasis has been given to the so-called solid-state batteries, which promise to revolutionize the concept of batteries by replacing the liquid electrolyte with a solid electrolyte. The ionic conductors Li0,5La0,5TiO3 and Na2Ti3O7 have great potential to replace the electrolytes that make up lithium batteries today and to compose the next generation of batteries. Therefore, this thesis aimed at the synthesis, sintering and electrical characterization of Li0,5La0,5TiO3 and Na2Ti3O7 ceramics in order to analyze the ionic conduction in these materials. The ceramic powders were produced by the polymeric precursor method and sintered by the conventional method in an electric oven and laser. Li0,5La0,5TiO3 and Na2Ti3O7 powders showed a single crystalline phase after being sintered at 1150 °C/2 h and 900 °C/2 h, respectively. The laser-sintered ceramics had a relative density of 98% for Li0.5La0.5TiO3 and 88% for Na2Ti3O7, with a single crystalline phase and processing time of less than 10 min. For Li0.5La0.5TiO3, ionic conductivity in the grain region of 0.5 mS.cm-1 at room temperature was obtained by both sintering methods. On the other hand, the grain boundary suffered a conductivity reduction of two orders of magnitude, in addition to a variation by a factor of five with the sintering method, which was attributed to changes in the microstructural characteristics (average grain size and thickness). The lasersintered Na2Ti3O7 ceramic showed a reduction of about 50% in the average grain size and an ionic conductivity of the grain at room temperature 58% (0.27 x 10-4 S.cm-1 ) higher than the conventionally sintered ceramic. Finally, the electrical response of the Na2Ti3O7 ceramic revealed 4 orders of magnitude jump in resistivity with increasing temperature identified as the PTCR effect (positive resistivity coefficient), reported for the first time.