Mechanism of ionic conduction and electrochemical intercalation of lithium into the perovskite lanthanum lithium titanate

✍ Scribed by O. Bohnke; C. Bohnke; J.L. Fourquet

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 938 KB
• Volume: 91
• Category: Article
• ISSN: 0167-2738
• DOI: 10.1016/s0167-2738(96)00434-1

✦ Synopsis

The ionic conductivity and electrochemical intercalation properties of La2,9_I Li,*TiO, solid solutions (for 0.07 5 x 5 0.13) have been studied. These compounds present a perovskite-type structure (ABO,) with cation deficiency at the A-sites. The purely ionic conductivity was confirmed and the mechanism of ionic conduction investigated using impedance spectroscopy techniques. We find that the temperature dependence of conductivity can be modelized by a Vogel-Tamman-Fulcher (VTF)-type relationship. In these materials, where the high ionic conductivity may originate from the presence of vacancies in the A-sites of the perovskite structure, the VTF behavior would suggest a mechanism of conduction involving the tilting of the TiO, octahedra. The lithium intercalation was also investigated in LiClO,(M)-PC electrolyte using galvanostatic discharge and charge at very low rates (one Li/250 and / 1500 h) in order to approach the equilibrium. It was shown that the lithium intercalation leads to the presence of a plateau around 1.5 VlLi in the discharge curve, it is partly reversible and the capacity of the electrode is not very high. A maximum lithium uptake of 0.15 was found. The diffusion coefficient of lithium in the intercalated material was determined by impedance spectroscopy at room temperature and found to range from lOm8 cm2 s-' to 10m9 cm's_' as intercalation proceeds. Since the experimental impedance spectroscopy data performed at room temperature follow a Warburg behavior at low frequency, the intercalation seems to proceed in a single-phase process although a plateau is observable in the discharge curve.