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

Abstract

The Fe-based Prussian blue (Fe-PB) composite is considered as one of the most potential cathode materials for sodium-ion batteries because of its abundant iron resources and high theoretical capacity. However, the crystal water and vacancy in the Fe-PB structure will lead to poor capacity and cycle stability. In this work, a Cu-modified Fe-PB composite (FeCu-PB@CuO) is successfully prepared through regulating the Fe-PB structure by Cu doping and engineering the surface by CuO coating. The density functional theory calculation results confirm that Cu preferentially replaces FeHS in the Fe-PB lattice and Cu doping reduces the bandgap. Our experiment results reveal that CuO coating can provide more active sites, inhibit side reactions, and potentially enhance the activity of FeHS. Due to the synergistic effect of Cu doping and CuO coating, FeCu-PB@CuO has a considerable initial discharge capacity of 123.5 mAh g–1 at 0.1 A g–1. In particular, at 2 A g–1, it delivers an impressive initial capacity of 84.3 mAh g–1, and the capacity decreasing rate of each cycle is only 0.02% over 1500 cycles. Therefore, the synergistic modification strategy of metal ion doping and metal oxide coating has tremendous application potential and can be extended to other electrode materials.

Air-Stable Prussian White Cathode Materials for Sodium-Ion Batteries Enabled by ZnO Surface Modification

“…The X-ray diffraction (XRD) patterns observed in the as-prepared samples are classified as characteristic monoclinic structures (Figure S1). This indicates that PW could remain the original monoclinic structure after ZnO coating but not become into cubic phase as reported in the literature . It is attributed to the utilization of anhydrous ethanol as a solvent in the synthesis process, which effectively mitigates the loss of sodium in the PW bulk phase.…”

“…The Nyquist plots were fitted with an equivalent circuit, as shown in the inset of Figure e–f, to obtain the impedance parameters ( R s and R ct ). R s and R ct are the ohmic resistance and the charge-transfer resistance in the cell, respectively. , The fitting results are presented in Table S3. Four electrodes exhibit similar Nyquist plots, and the overall resistance is dominated by the R ct .…”

“…As to Na x TMO 2 , it could maintain the original crystal structure during the heating. However, PW could suffer from sodium leaching into the aqueous solution and decomposition when the temperature exceeds 300 °C. − Thus, it is necessary to design a rational coating method to avoid the leaching of sodium ions in the solvent and the decomposition of PW at a high temperature.…”

Increasing Tap Density of Carbon-Coated Na3V2(PO4)2F3 via Mechanical Grinding: Good or Bad Idea?

“…Among the various phosphate, sulfate, pyrophosphate, and other polyanionic compounds investigated as positive electrode materials, Na 3 V 2 (PO 4 ) 2 F 3 (NVPF) stands out due to its high working potential and attractive reversible capacity (128 mAh g –1 for the reversible extraction of 2 Na + per formula unit at ∼3.9 V vs Na + /Na). − Additionally, the first 18650 prototypes built with carbon-coated NVPF (NVPF@C) at the positive electrode have demonstrated excellent rate performance and cycling stability, making this material ideal for high-power applications . However, as for PBA and the other polyanionic electrode materials, NVPF suffers from low tap density, which is one of the most important parameters when it comes to practical applications. ,, A low tap density (g/cm –3 ) reduces the amount of material that can be introduced in a defined volume, such as a cylindrical 18650 cell, leading to a poor volumetric energy density. Furthermore, it necessitates thick electrodes for high mass loading, which penalizes the power density.…”

Y-tube assisted coprecipitation synthesis of iron-based Prussian blue analogues cathode materials for sodium-ion batteries

“…22,23 Consequently, the realized capacity and cycle life of the material are compromised. Despite efforts to enhance electrochemical performance through various strategies, such as ion doping or optimizing the composition or framework structure of PBAs, [24][25][26][27][28][29] nanoparticle sizing, 9,14,30 designing porous structures or unique morphologies, 31 post-synthesis dehydration processing, [32][33][34] surface coating modications, 31,35,36 and optimizing electrolyte composition, [37][38][39] these measures are yet insufficient to fundamentally overcome the issues posed by vacancy defects and associated crystal water. At the heart of the matter, crystal vacancy defects and crystal water primarily form during the synthesis process.…”