The internal resistance is the key parameter for determining power, energy efficiency and lost heat of a lithium ion cell. Precise knowledge of this value is vital for designing battery systems for automotive applications. Internal resistance of a cell was determined by current step methods, AC (alternating current) methods, electrochemical impedance spectroscopy and thermal loss methods. The outcomes of these measurements have been compared with each other. If charge or discharge of the cell is limited, current step methods provide the same results as energy loss methods.

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The lithium-rich limit of the electrolyte stability window of the fast-ion-conducting defect perovskite Li029La057TiO3 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 0> 1 0 cm2/s 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.

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