Lithium ion batteries are a key technology of our time, recognized for example by the 2019 Nobel Prize in Chemistry. Current lithium ion batteries contain highly reactive and flammable organic electrolytes in combination with electrode materials that release oxygen upon overheating. This intrinsic safety issue drives the wish for safer all-solid-state batteries with inorganic electrolytes. Another big advantage of solid electrolytes is the possibility of employing lithium metal anodes which can boost the energy density of the cells. A variety of materials with different crystal structures may be used as electrolytes, such as perovskite-type LixLa0.66-x/3TiO3 (LLTO), NASICON-type Li1+xAlxTi2-xPO4 (LATP) and Garnet-type Li7-3xLa3GaxZr2O12 (LLZO). These materials have in common that the possible Lithium sites are only partly occupied, which allows fast transport of lithium ions from one lattice site to a neighbouring vacancy. Especially LLZO moved in the focus of research recently, due to its high ionic conductivity of 10-3 S/cm at room temperature and a sufficiently high chemical stability in the presence of metallic lithium.
In our group, we investigate the conduction mechanisms, as well as the defect chemistry of solid state electrolytes, with a focus on LLZO. Another current task is the optimization of the so far very sluggish lithium transfer kinetics between solid electrolyte and Li cathode materials like Li1-xCoO2, as well as measurement of lithium diffusion coefficients in electrode materials by electrochemical methods. Our long term goal is gaining a deeper insight into the rates and mechanisms of lithium transfer both at the electrode-electrolyte interface, as well as within the electrode material in order to enable safe solid state batteries with high performance.