fig6

Figure 6. Sodium-storage mechanism and structure-performance correlation of hard carbon electrodes. Ex situ XRD patterns of the R-HC-20 electrode collected at different electrochemical states (A); b-values of FR-HC and R-HC-x electrodes at 0.5 and 0.05 V, respectively (B and C); GITT voltage profiles and corresponding Na⁺ diffusion behavior of FR-HC and R-HC-x electrodes during sodiation/desodiation processes (D and E). EIS Nyquist plots of FR-HC and R-HC-x electrodes (F). In situ EIS spectra of the R-HC-20 electrode recorded at different discharge and charge states during the initial cycle (G and H). FR: Fresh reeds; XRD: X-ray diffraction; GITT: galvanostatic intermittent titration technique; EIS: electrochemical impedance spectroscopy.