Jakub Leščinský is a first-year PhD student in the Department of Physical Chemistry at the Faculty of Science of Pavol Jozef Šafárik University in Košice, supervised by doc. RNDr. Andrea Straková Fedorková, PhD. His research focuses on lithium–sulfur batteries, particularly on the influence of polysulfides and additives on their stability and lifetime. He studies sulfur-based cathode materials, polysulfide migration, and strategies for cathode and separator modifications to improve cyclability and long-term performance. Alongside his research, he is involved in teaching activities at the department and has received several awards, including the Rector’s Prize of UPJŠ, 1st place in the Literary Fund competition, and top placements in student scientific conferences.