The reason can be swelling effects of electrolyte solvent, which could be observed when (partially) solvated Na + is the intercalating species into HTO-PA. We hypothesize this as the likely scenario, because we previously identified that Li + intercalates in partially solvated state in HTO-PA materials. While our ECD results are a first indication for an ion-solvent cointercalation mechanism for Na + in HTO-PA hosts, a precise determination of the charge storage mechanism has to be conducted in followup work. In conclusion, our work compared the electrochemical sodium intercalation performance of pristine and pillared/interlayer-expanded HTO host materials. We found that expanded HTO-PA exhibits an increased maximum sodiation capacity, and at the same time improved kinetics and electrochemical reversibility compared to pristine HTO. Electrochemical dilatometry revealed increased SEI formation/side reactions in pristine HTO in the first cycle. Moreover, a consistent, irreversible thickness increase of HTO-PA over five cycles is indicative of the intercalation of partially solvated Na + . The work is significant for the further improvement of titanatebased anode materials for sodium-ion batteries because it demonstrates the strong impact of nanoconfinement properties of the interlayer on the electrochemical sodiation properties.