Naturgy, through Naturgy Innovahub, its vehicle focused on research into technologies linked to the energy transition, and the City of Energy Foundation (CIUDEN) attached to the Institute for a Just Transition (ITJ) under the Ministry for Ecological Transition and the Demographic Challenge (MITECO), have signed a collaboration agreement to develop a pioneering project in the field of energy storage based on second-life batteries from electric vehicles, which represents a milestone in the search for sustainable energy solutions.