Besides their use as host rock or geotechnical barrier in nuclear waste disposal sites, clay materials play a crucial role in advancing a carbon-neutral and sustainable energy system. The BARRIERS project, leveraging a strong collaboration between French and German research teams with complementary expertise in the fields of geophysics and geochemistry, aims to address future needs for efficient geophysical characterization tools for clay strata. Given their sensitivity to crucial properties like clay mineralogy, porosity, permeability, water content, and (surface) diffusivity, geoelectrical and electromagnetic exploration methods are promising tools for the characterization of clay formations. The project involves the development of novel experimental techniques and numerical modeling approaches to investigate the broadband dielectric response of clay materials and understand the underlying processes.