Formation Mechanism of Amorphous Li₄GeO₄ Nanoparticles Synthesized by Induction Thermal Plasma for All-Solid-State Batteries

Abstract

Induction thermal plasma as an advanced synthesis method for amorphous nanoparticles attracts a lot of attention. Amorphous Li4GeO4 nanoparticles were synthesized by induction thermal plasma with different Li/Ge molar ratios and quenching gas flow rates. Transmission electron microscopy, X-ray diffraction, and Raman spectroscopy were conducted to understand the product morphology and chemical composition. The formation mechanism was investigated according to experimental results and thermodynamic analysis. The topological order of prepared nanoparticles was discussed in the short range and intermediate range based on O–Ge–O and Ge–O–Ge angle distributions, respectively. An enhanced amorphous degree of Li4GeO4 and a fraction of high-temperature-phase γ-Li4GeO4 were obtained in high Ge content and quenching rate conditions. The amorphous Li4GeO4 degree achieved around 65% with 10 L/min quenching gas injection. However, excessive Ge content and quenching rate also result in byproduct Li2GeO3 formation. The above results indicate that amorphous Li4GeO4 nanoparticles can be efficiently synthesized by induction thermal plasma with an appropriate Li/Ge molar ratio and quenching rate.