Challenges regarding thin film deposition of garnet electrolytes for all-solid-state lithium batteries with high energy density

In this work, we studied the deposition of garnet electrolyte thin films in order to realize an all-solid-state battery with high energy density. Therefore, in a first step we investigated the stability of the garnet Li5La3Ta2O12 with the spinel LiCoMnO4 in order to determine the temperature window for a successful thin film deposition on high-voltage spinels. A mixture of both materials showed a thermal stability up to 600 °C, so that all-solid-state batteries could be realized when the electrolyte is applied at a low deposition temperature. The second part of the work was the thin film deposition of Li5La3Ta2O12 by a sputter deposition process. When a stoichiometric Li5La3Ta2O12 sputter target was used, the surface of the target showed a depletion of lithium after several depositions, which leads to decreasing Li content in the thin films. In order to compensate the lithium loss we enriched the target with LiOH∙

Bulk and grain boundary Li-diffusion in dense LiMn2O4 pellets by means of isotope exchange and ToF-SIMS analysis

Lithium diffusion in LiMn2O4 pellets is studied by means of isotope exchange and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). A 6Li-enriched film deposited by Pulsed Laser Deposition (PLD) on a dense LiMn2O4 pellet with natural abundance of lithium isotopes is used to study the tracer diffusion of lithium. The measured profiles are analyzed by numerical models describing the 6Li tracer diffusion from the film into the pellet. Experiments in the Harrison type B regime of diffusion kinetics allow for the distinction and simultaneous determination of bulk and grain boundary diffusion coefficients. Changing the experimental conditions to reach Harrison type A behavior yields effective diffusion coefficients for lithium tracer diffusion in LiMn2O4. Activation energies for bulk and grain boundary diffusion were obtained from experiments at different temperatures. Our values are critically compared to previous studies