Towards High-Energy Solid-State Lithium Batterieswith Garnet-type Electrolytes

The application of garnet-type electrolyte thin films was studied, targeting at solid-state batteries with high energy density. Firstly, the chemical stability window Li5La3(Zr,Ta)2O12 with the so-called high voltage cathode active material LiCoMnO4 was assessed in order to determine the temperature range for a successful combination. The materials showed different thermal stability for different compositions. Secondly, Li5La3(Zr,Ta)2O12 was deposited by a sputter deposition process as thin films. A depletion of lithium in the sputter target can occur after several depositions, which leads to decreasing Li content in the electrolyte thin films. Therefore, the target was enriched with LiOH∙H2O to compensate the lithium loss. Depositions carried out with a lithium rich target of Li5La3Ta2O12 showed the garnet structure on glass substrates after deposition at 500 °C, i.e. at significantly lower temperature compared to Li5La3Zr2O12. The garnet structure was observed on Au-coated EN 1.4767 substrates already at a substrate temperature of 400 °C, which is 300 K lower than comparable depositions of Li7La3Zr2O12, which is within the stability range of a combination of Li5La3Ta2O12 electrolytes and high-voltage spinels