Solid Electrolyte Membranes Based on Li2O-Al2O3-GeO2-SiO2-P2O5 Glasses for All-Solid State Batteries.

Rechargeable Li-metal/Li-ion all-solid-state batteries due to their high safety levels and high energy densities are in great demand for different applications ranging from portable electronic devices to energy storage systems, especially for the production of electric vehicles. The Li1.5Al0.5Ge1.5(PO4)3 (LAGP) solid electrolyte remains highly attractive because of its high ionic conductivity at room temperature, and thermal stability and chemical compatibility with electrode materials. The possibility of LAGP production by the glass-ceramic method makes it possible to achieve higher total lithium-ion conductivity and a compact microstructure of the electrolyte membrane compared to the ceramic one. Therefore, the crystallization kinetics investigations of the initial glass are of great practical importance. The present study is devoted to the parent glasses for the production of Li1.5+xAl0.5Ge1.5SixP3-xO12 glass-ceramics. The glass transition temperature Tg is determined by DSC and dilatometry. It is found that Tg decreases from 523.4 (x = 0) to 460 °C (x = 0.5). The thermal stability of glasses increases from 111.1 (x = 0) to 188.9 °C (x = 0.3). The crystallization activation energy of Si-doped glasses calculated by the Kissinger model is lower compared to that of Si-free glasses, so glass-ceramics can be produced at lower temperatures. The conductivity of the glasses increases with the growth of x content.

Phase Composition, Density, and Ionic Conductivity of the Li7La3Zr2O12-Based Composites with LiPO3 Glass Addition.

The glass-ceramic composite electrolytes based on tetragonal Li7La3Zr2O12 (t-LLZ) and cubic Al-doped Li7La3Zr2O12 (c-LLZ) with the LiPO3 glass additive have been prepared. The electrical conductivity and microstructure of the t-LLZ/LiPO3 and c-LLZ/LiPO3 composites have been investigated. The phase evolution of electrolytes has been studied using XRD, SEM, and Raman spectroscopy. It was indicated that the impurities formation depends on the composition of the composite. The phase composition of the solid electrolytes determines their thermal properties, which have been studied by the DSC method. The relative density of the obtained composite electrolytes was established to be higher than one of the sintered t-LLZ and c-LLZ. The Li+ conductivity of the t-LLZ-based composites gradually increased from 4.6 × 10-7 S cm-1 (undoped t-LLZ) to 2.5 × 10-6 S cm-1 (t-LLZ/5 wt % LiPO3 composite) at 25 °C. The highest total conductivity of the c-LLZ/LiPO3 composites has been achieved by introducing 1 wt % additive (0.11 mS cm-1 at room temperature), whereas further doping resulted in the impurities formation.