Electrolytic Stability Limit and Rapid Lithium Insertion in the Fast‐Ion‐Conducting Li0.29La0.57TiO3 Perovskite‐Type Compound

The lithium‐rich limit of the electrolyte stability window of the fast‐ion‐conducting defect perovskite was found to be about 1.7 V vs. Li at 24°C.The coulometric titration curve was determined, indicating that reversible insertion/extraction of 0.14 additional Li, corresponding to the complete occupation of the vacant A‐sites, is possible. The galvanostatic intermittent titration technique was used to evaluate the chemical diffusion coefficient as a function of composition. It was very high, and varies less than a half‐order of magnitude over this stoichiometry range. Values of were found both for lithium insertion and for lithium extraction. To our knowledge this is one of the highest diffusion coefficients observed in a lithium‐conducting insertion‐reaction oxide.