Interstitial Water Improves Structural Stability of Iron Hexacyanoferrate for High-Performance Sodium-Ion Batteries

Abstract

Prussian blue analogues (PBAs) are considered one of the promising cathodes for sodium-ion batteries because of their low cost and tunable structure. As an intrinsic characteristic, the influence of structured water in PBAs on the electrochemical properties is still controversial. Herein, low-vacancy iron hexacyanoferrate with different interstitial water contents is synthesized through the citric acid-assisted single iron source method. Ex situ Fourier transform infrared and X-ray diffraction characterization reveals that the interstitial water can stably exist in the Prussian blue framework during repeated cycling. The longstanding interstitial water can reduce the volume change during the Na + insertion/extraction process, resulting in improved cycling stability. Thanks to the low Fe(CN) 6 4− vacancies and pillar role of interstitial water in the crystal framework, the HW-PB exhibits a high reversible capacity of 117 mAh g −1 and excellent long cycle performance with a capacity retention of 91% after 1380 cycles. This work broadens the understanding of the relationship between the interstitial water in PBAs and Na-storage performances, providing guidance for the precise synthesis of high-quality PBAs.

Synergistic Modification of Fe-Based Prussian Blue Cathode Material Based on Structural Regulation and Surface Engineering

“…52-1907), demonstrating that the two samples are in the pure phase. The diffraction peak splitting of Fe-PB suggests that the crystal structure transforms from cubic to monoclinic. ,,− However, the FeCu-PB@CuO composite returns to the cubic structure after incorporating Cu. In addition, the XRD peaks of FeCu-PB@CuO shift to a high diffraction angle (Figure b), which indicates that the Na in FeCu-PB@CuO is less than that in Fe-PB.…”

Fluffy-Like Cation-Exchanged Prussian Blue Analogues for Sodium-Ion Battery Cathodes

“…As shown in Figure 4a, the redox peaks are observed at 3.15/ 2.63, 3.36/3.24, and 3.84/3.64 V for the PB-Ni-1d cathode, corresponding to the insertion/extraction of Na + processes. The redox peaks 3.36/3.24 and 3.84/3.64 V are attributed to the redox reaction of low-spin Fe 2+ connected to C. 39 Moreover, good consistence at 3.15/2.63 V can be observed in CV curves for the second cycle to the third cycle, which demonstrates a highly reversible redox reaction and excellent cycling reversibility. The charge/discharge curves (Figures 4b and S5) of HS-PB and PB-Ni (PB-Ni-1d, PB-Ni-2d, and PB-Ni-3d) are in accord with the features of CV curves, which indicates reliable charge−discharge platforms and good stability.…”

Guest water hinders sodium-ion diffusion in low-defect Berlin green cathode material

“…7,14 Clearly, the presence of water mitigates some of the associated strain by preventing a large volume change during cation insertion/extraction process resulting in improved cycling stability. 15 However, the relationship between the A-site cation and interstitial water has not been explored in detail for [Fe(CN) 6 ]-vacancy free PBAs. In some cases studies have reported that reducing the water content in PBAs leads to more stable cycling performance, whereas others report that the presence of water leads to a higher capacity.…”