65133 2025 eng poster 0 -- -- -- Hard carbons (HCs) are promising anodes for sodium-ion batteries (SIBs) due to their high capacity and low cost. However, their broader use is limited by an incomplete understanding of sodium storage mechanisms. Internal porosity is key to high capacity, but tuning its chemical functionality remains challenging. In this study, we designed core–shell carbon materials featuring closed pores and tailored surface chemistry to distinguish reversible sodium storage from irreversible capacity losses associated with solid electrolyte interphase (SEI) formation. Our results reveal that external porosity can be clearly converted into internal porosity, leading to enhanced sodium storage performance, with capacities exceeding those of lithium in graphite. Advanced Automotive Battery Conference (AABC) 2025 Mainz, Germany 23.06.2025 26.06.2025 publish false true Shu-Han Wu eng uncontrolled Sodium-ion batteries eng uncontrolled Hard carbon eng uncontrolled Core-shell materials Angewandte Physik 3 Gefahrgutumschließungen; Energiespeicher Energie Elektrische Energiespeicher und -umwandlung Datei im Netzwerk der BAM verfügbar ("Closed Access") Präsentation 3.6 Elektrochemische Energiematerialien