Chemistry and interface tailored lead-free relaxor thin films for energy storage capacitors
The goal of CITRES is to provide new energy storage devices with high power and energy density by developing novel multilayer ceramic capacitors (MLCCs) based on relaxor thin films (RTF). 

Energy storage units for energy autonomous sensor systems for the Internet of Things (IoT) must possess high power and energy density to allow quick charge/recharge and long-time energy supply. Current energy storage devices cannot meet those demands: Batteries have large capacity but long charging/discharging times due to slow chemical reactions and ion diffusion. Ceramic dielectric capacitors – being based on ionic and electronic polarisation mechanisms – can deliver and take up power quickly, but store much less energy due to low dielectric breakdown strength (DBS), high losses, and leakage currents. 

RTF are ideal candidates: (i) Thin film processing allows obtaining low porosity and defects, thus enhancing the DBS; (ii) slim polarisation hysteresis loops, intrinsic to relaxors, allow reducing the losses. High energy density can be achieved in RTF by maximising the polarisation and minimising the leakage currents. Both aspects are controlled by the amount, type and local distribution of chemical substituents in the RTF lattice, whereas the latter depends also on the chemistry of the electrode metal. 
 
In CITRES, we will identify the influence of substituents on electric polarisation from atomic to macroscopic scale by combining multiscale atomistic modelling with advanced structural, chemical and electrical characterizations on several length scales both in the RTF bulk and at interfaces with various electrodes. This will allow for the first time the design of energy storage properties of RTF by chemical substitution and electrode selection.

The ground-breaking nature of CITRES resides in the design and realisation of RTF-based dielectric MLCCs with better energy storage performances than supercapacitors and batteries, thus enabling energy autonomy for IoT sensor systems.