Synthesis of M1+xAlxTi2-x (PO4)3 (where M=Li or Na) Based Electrolyte Materials for Solid State Batteries and Study of their Electrochemical Properties

Abstract

As "Necessity is the mother of invention", energy is stored from primary sources and released out, for consumption when there is a shortage of energy, to balance the life of human beings. In the modern world, sensational research has been done to design storage devices. While considering cost and environmental aspects, the researcher is impatient to find a friendlier environment and portable energy storage devices. The desire for environment-friendly and portable energy storage devices has steered the thorough investigation for all-solid-state rechargeable batteries. Solid state batteries have got attention because of more energy security and long life. Phosphate-based ceramic electrolytes are promising candidates for solid state electrolyte- based lithium and sodium-ion batteries. Sodium-ion batteries can potentially hold energy comparable to that of commercial lithium-ion batteries. Li resources are limited whereas sodium is one of the most abundant elements in the Earth’s crust. Rechargeable sodium cells are the ideal alternative to lithium-ion batteries based on material abundance and standard electrode potential. In this work, phosphate-based solid state electrolytes as M1+xAlxTi2-x (PO4)3 where M= Li, Na, and x = 0.5, are synthesized by solid state reaction and ball milling method. The main objective of this study is to examine the ionic behavior, homogeneity, porosity, crystal structure, and band-gap and also to determine the charging and discharging rate of the prepared material. The crystal structure of synthesized powder is examined by the x-rays diffraction technique. X pert high score software is used to determine the phase of the prepared material. Synthesized material has a single crystalline phase same as NASICON type material with space group R3̅c. Microstructure analysis is done by using scanning electron microscopy. The porosity of solid-state electrolytes is determined by the Archimedes method. The charging and discharging rate are examined by electrochemical techniques (AC-impendence-conductivity, cyclic voltammetry). The ionic conductivities of both have the same exponential value with 2.09×10-3 and 1.96×10-3 at 25°C, respectively. Ultraviolet spectroscopy is done to examine the band-gap. Tauc plot is used to determine band-gap for Li1.5Al0.5Ti1.5 (PO4)3 and the Na1.5Al0.5Ti1.5 (PO4)3. Raman spectroscopy is used to determine the vibrational energy modes of the prepared material