engleski

Ionic Transport in Mixed Network Former Li2O-P2O5-GeO2 Glass-Ceramics

In the recent years, novel glass-ceramic materials are being investigated for their potential application as solid electrolytes in batteries. The goal in such studies is to enhance the ionic conductivity of Li-ion batteries along with the improvement of stability and safety. Recently, glass systems with mixed glass network formers are being considered as promising materials for these requirements. In this work, mixed glass former system with the composition 40Li2O-(60-x)P2O5-xGeO2, x = 0- 25 mol% was chosen for the investigation of the effect of crystallization on electrical properties. It was previously found that in glass system with same composition the dc conductivity increases for three orders of magnitude. The observed effect is a result of gradual incorporation of GeO2 into phosphate network which leads to facilitated Li+ ions mobility. Therefore, our interest was to investigate how various steps of crystallization influence the electrical transport in these glasses. Depending on the composition and according to DTA curves, the temperature and time of heat-treatments were determined for each starting glass. With increasing GeO2 content single and multi-crystalline phase glass-ceramics were obtained and were structurally characterized by XRD, MAS NMR and SEM. Impact of structural changes on the electrical transport was explored in details with impedance spectroscopy. For GeO2-free glass-ceramic a slight increase in the electrical conductivity was evidenced in comparison to the non-treated glass. Further, conductivity decreases for heat-treated glasses containing up to 20 mol% of GeO2 which is related to the reduction of Li+ concentration in residual glass matrix since the Li-based crystalline phases were formed. On the other hand, for the glass-ceramic with the highest germanium content an increase in the conductivity is observed. This effect is probably due to the formation of well-defined crystallites which pronounces easy conduction pathways for Li+ ion transport within crystalline grains and along grain boundaries.

Glass-ceramics ; Electrical transport ; Structure ; Mixed glass former effect

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