resting) of the intercalation process (Fig. ) and to calculate the apparent diffusion coefficient of Na + in HTO and HTO-PA (Fig. ). The voltage hysteresis of the (de)sodiation process in HTO-PA is reduced by ca. 100 mV compared to HTO up to about 60 % of the maximum sodiation capacity. Beyond this, a comparably small hysteresis is seen for both host materials. Moreover, the apparent Na + diffusion coefficient extracted from GITT data is improved by a factor of ca. 2 over the entire sodiation process. The results indicate improved kinetics of the sodiation process in pillared HTO-PA host materials. To evaluate the volumetric response of the HTO and HTO-PA host materials towards electrochemical (de)sodiation, we performed electrochemical dilatometry measurements over five consecutive cycles. After one full (de)sodiation cycle, the height of the HTO electrode irreversibly increased by ca. 12.5 %, while HTO-PA expanded by ca. 9 %. This indicates stronger solid electrolyte interphase formation and/or side reactions in pristine HTO. The expansion behavior of successive cycles shows smaller volumetric changes in HTO accompanied with fast degradation of performance. Contrarily, the dilatometric signal of HTO-PA is consistent over five cycles, with an irreversible increase of electrode thickness of about 4 -6 % per cycle.