Influence of AlPO4 Impurity on the Electrochemical Properties of NASICON‐Type Li1.5Al0.5Ti1.5(PO4)3 Solid Electrolyte

• Published in: ChemElectroChem Vol. 9; no. 24
• Main Authors: Campanella, Daniele, Krachkovskiy, Sergey, Faure, Cyril, Zhu, Wen, Feng, Zimin, Savoie, Sylvio, Girard, Gabriel, Demers, Hendrix, Vijh, Ashok, George, Chandramohan, Armand, Michel, Belanger, Daniel, Paolella, Andrea
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 27-12-2022
• Subjects: AlPO4; Aluminum phosphate; Corrosion resistance; Crystallites; Densification; Density functional theory; Electrochemical analysis; Electrolytes; Grain size; High temperature; Hot pressing; Impurities; Ion currents; LATP; Molten salt electrolytes; NMR; Nuclear magnetic resonance; Solid electrolytes; Stability
• ISSN: 2196-0216; 2196-0216
• DOI: 10.1002/celc.202200984

Densification of ceramic electrolytes is a key enabler in producing electrolyte pellets for solid‐state batteries. This requires understanding the correlation between the starting grain size of electrolytes, chemical phase evolution and degree of compaction which determine ion conductivity and chemical stability of solid electrolytes. In our work we were able to optimize the densification process of LATP at 700 °C with a high total ionic conductivity of 3.45×10−4 S cm−1 after hot pressing, balancing pristine LATP crystallite size and AlPO4 impurity formation. By combining several techniques such as in situ heating X‐ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR), we explored the formation mechanism of AlPO4 during the synthesis process of NASICON‐type Li1.5Al0.5Ti1.5(PO4)3 (LATP) electrolyte and we showed the effects of the annealing temperature on the crystal size of the material. Density functional theory (DFT) calculations on the chemical stability of the electrolyte imply a metastable behaviour of LATP furtherly enhanced by particle nano‐structuring at high temperature. Our results point to facile manufacturing of ceramic electrolytes towards energy dense and safe solid‐state battery technology.
Role of AlPO4 Impurity on Solid‐State Electrolytes: Mutual relation between grain size, phase evolution and compaction have an influence on total conductivity and stability of solid‐state electrolytes. The formation mechanism of AlPO4 impurity during the synthesis of LATP electrolyte is affected by the annealing temperature, which reflects on the crystal dimensions. Moreover, the metastable behaviour exhibited by LATP is furtherly improved by particle nano‐structuring at high temperature.