This project is focused on the investigation of new cathode and solid electrolyte (SE) materials for applications in Li-ion all-solid-state batteries (ASSB). Here, powders of the active material (AM), carbon (to increase the electrical conductivity) and SE are sintered together as a cathode pellet, which is then topped by a layer of SE and, finally, attached to an anode; e.g. Li metal. ASSBs overcome safety issues (e.g. flammability of organic electrolytes) and result in robust and inert batteries that function at slightly elevated temperatures.

To date, only little is known on the detailed mechanisms of Li-ion transport in SE, the phases and interfaces forming during synthesis and operation, and how particle sizes of the starting materials influence both, the densification/sintering and electrochemical performance. We will use classical solid-state synthesis routes to produce new AM (e.g. LFP and higher voltage cathodes such as NMC and LMP) and SE (e.g. LSPO, LLZO, and LPS) materials and control their particle sizes. Spark Plasma Sintering (SPS), a novel processing technique, will then be applied to produce dense pellets of AM/SE cathode composites.

Powder XRD will be used to determine phase purity and particle sizes of both the pristine materials as well as the composites prepared by SPS. The powders and pellets will be used for electrochemical testing. Solid-state NMR will be utilised to gain insights into different chemical environments/phases on a local atomic scale, derive activation energies and learn about the underlying ion diffusion mechanism. In a next step, in situ NMR will be applied to study structural changes in real-time. EIS will be used to derive conductivities; the data will be combined with the NMR studies. Another crucial method will be electron microscopy on pellets/composites Contrast differences will give information on particle (size) distributions and phases present, while EDX will allow a quantification of the elemental composition.