Obtention and characterization of lithium superionic conductors using the glass-ceramic method

Abstract

This paper proposes the glass-ceramics method for obtaining lithium ion (Li + ) solid electrolytes. This technique provides high chemical and microstructural homogeneity as well as low porosity. Glass samples were subjected to either single or double heat treatments, between 700 °C and 1000 °C, in order to obtain the glass-ceramics. Differential Scanning Calorimetry -DSC -results evidenced the possibility of fabricating these ceramics from glass in the system Li2O·Al2O3·TiO2·P2O5. Samples observed by Scanning Electron Microscopy -SEMshowed a finely grained microstructure which was homogeneously distributed and non-porous. X-ray Diffraction -XRD -patterns showed the formation of the high conducting phase LiTi2(PO4)3. A high ionic conductivity, in the order of 10 -3 S/cm at 1000 °C, was measured by Impedance Spectroscopy -IS. It suggests that the synthesis method used in this research is useful for fabricating lithium ion glass-ceramics and opens up a new alternative for manufacturing different electrical ceramics.

Methods for Lithium Ion NASICON Preparation: From Solid-State Synthesis to Highly Conductive Glass-Ceramics

“…This homogeneity is comparable to that obtained by the wet-chemical methods of synthesis. Furthermore, complex compositions and controllable microstructure can be achieved utilizing scalable techniques. , Ionic conductivities comparable or even better than those related to materials obtained by solid-state and chemical synthesis methods have been reported. ,,− Therefore, the following topic will discuss the main advances of lithium ion NASICON prepared as glass-ceramics. The influence of the NASICON composition on conductivity, as well as the parameters used for glass crystallization and the resulting microstructure, will also be widely discussed.…”

“…However, a typical MQC method is even more advantageous to ease shaping and allow control of the glass-ceramic microstructure by heating treatment. , This method also avoids contamination of the NASICON produced by the material arising from the wear of the grinding vessels, which is inherent in the HEM technique. The glass-ceramics obtained by MQC are crystallized directly in the final shape, ,,, that is, dispensing sintering. A porosity less than 5% is typically obtained …”

“…A review of the most promising advances in lithium ion NASICON glass-ceramics is summarized in Table . ,,,,− ,,,,,,,,,,,,,,,− In this table, T g is the glass transition temperature, and T x is the onset for glass crystallization. In summary, using germanium and titanium as B (IV) cation characterize almost all the NASICON glass-ceramics already explored.…”

“…However, cationic transport is usually limited in these materials. − Sulfide glasses present the best transport properties, showing typical lithium conductivity on the order of 10 –3 S cm –1 at room temperature . However, they are very unstable in environmental conditions, generating H 2 S by humidity exposure. , Oxide electrolytes are superior in chemical stability, ion selectivity, and thermal stability compared to polymers and sulfides. ,, In particular, the Na + Super Ionic Conductor (NASICON) is a class of phosphate-type electrolytes that can approach lithium conductivity in the same order of sulfides (10 –4 to 10 –3 S cm –1 ), ,,− while the chemical stability in air is maintained. ,, …”

“…This structure provides many possibilities for an A-mobile cation other than sodium (Li + , Ag + , K + , Cu + , etc. ), , which is conducted through structural channels in all three dimensions. , The variety and proportion of B (III) cations (e.g., Al 3+ , Cr 3+ , Fe 3+ , In 3+ ) and B (IV) cations (e.g., Zr 4+ , Ge 4+ , Hf 4+ , Sn 4+ ) change the net polarizability and lattice parameters and allows an extra quantity of mobile A (I) cation in the skeletal structure. , These conditions highly impact the cationic motion and conductivity by consequence, varying in a broad interval (on the order of 10 –8 to 10 –3 S cm –1 at room temperature). ,,− ,, …”