NASICON-type lithium iron germanium phosphate glass ceramic nanocomposites as anode materials for lithium ion batteries

Abstract

New glass ceramic nanocomposites based on the Li1.6Fe0.6Ge1.4(PO4)3 (LFGP) are successfully synthesized, by crystallization of LFGP parent glass, and studied as anode materials for lithium ion battery (LIB). The appropriate temperature for crystallizing the LFGP parent glass is determined by Differential Scanning Calorimetry (DSC). XRD pattern asserted the amorphous essence of LFGP parent glass. XRD results also affirmed the creation of the NASICON phase in the investigated LFGP glass ceramics obtained by heat treatment (HT) for different durations. Additionally, the structure refinement parameters of LFGP glass ceramic samples are determined. Moreover, TEM, SEM and FTIR confirmed the creation of NASICON phase. The electrical conductivity of LFGP glass ceramic nanocomposites obtained by HT ≥ 6 h significantly increased up to 10−3 order. The galvanostatic cycling (GC) and cycling voltammetry (CV) techniques were implemented for the assembled batteries to investigate the specific capacity and redox reactions during Li+ ions insertion/extraction processes. Therefore, it is suggested that the improved storage capacity and capacity retention (97.9%) for the LFGP HT12h electrode after 50 cycles could be attributed to the synergistic action of cation vacancies formed in the NASICON structure and the glass material shells around the LFGP nanoparticles which prevent further oxidation of Ge into GeO2. Furthermore, the electrochemical impedance spectroscopy (EIS) estimations affirmed the excellent cyclic stability of the optimum LFGP anode owing to the enhanced ionic conductivity and fast diffusion rates of Li+ ions.