Development of a Solid-State Ta-Doped Lithium Lanthanum Zirconium Oxide Electrolyte for All-Solid-State Lithium Batteries (ASSLBs)

Large, high-power batteries are necessary for electric vehicles. The safety of batteries is also crucial, as damaged batteries should not be combustible. Moreover, in some cases batteries need to operate a modestly high temperatures in the range of 100 - 150 0 C. All-solid-state lithium batteries (ASSLBs) can handle these requirements with ceramic electrolytes, lithium intercalation cathodes, and lithium metal anodes. Although ASSLBs using variations on this material set have been demonstrated, they tend to have low power, in part because of low ionic conductivity, as well as low rates of interfacial reaction between electrodes and electrolytes. Various strategies are being investigated to address the challenge of low power including operating at elevated temperatures, using doped electrolytes, increasing the contact area between the electrodes and the electrolyte, and through engineering of the interfaces between electrodes and electrolytes. Using tape casting followed by sintering, we are producing thin (~20µm) and dense Ta-doped Lithium Lanthanum Zirconium Oxide (LLZTO) films, and also LLZTO pellets. The challenge of Li-loss during sintering has been addressed by using suitable sintering aids and sacrificial Li source. We have characterized LLZTO films and pellets using techniques such as XRD, SEM, and SEM EXA. The electrochemical properties of the LLZTO electrolyte including ionic conductivity have been measured. This is the first step in the creation of a full cell with engineered electrodes and interfaces. An analytical model has been developed to examine the effect of thickness of anode, cathode, and current collector on energy density.