Iñigo Salazar Beitia is doing his last year 2019-2020 of the Physics Degree at the UPV/EHU. Previously, he did a training practice under the supervision of PhD. Maider Zarrabeitia in the framework of the summer internship program of CIC energiGUNE on the irreversibility of a sodium base electrode for a sodium-ion battery. Then he continued with the project for which he received a scholarship within the framework of the Basque Government´s Transition to the World of Work program. Currently, he’s developing his final degree work under the supervision of PhD. Maider Zarrabeitia and Professor Josu Mirena Igartua from the Department of Applied Physics II of the UPV/EHU on the improvement of the irreversibility of a sodium base electrode by physical methods for sodium-ion batteries.