Enhanced Electrochemical Performance of Sodium Manganese Ferrocyanide by Na₃(VOPO₄)₂F Coating for Sodium-Ion Batteries

Abstract

Sodium manganese ferrocyanide Na x Mn­[Fe­(CN)6] y is an attractive cathode material for sodium-ion batteries. However, Na x Mn­[Fe­(CN)6] y prepared by simple coprecipitation of Mn2+ and [Fe­(CN)6]4– usually shows poor cycling performance, which hinders its practical application. In this work, electrochemical performance of a Na1.6Mn­[Fe­(CN)6]0.9 (PBM) sample prepared by the simple precipitation method was greatly improved by coating with Na3(VOPO4)2F (NVOPF) via a solution precipitation method. The as-prepared PBM@NVOPF with a coating quantity of 2.0% molar ratio showed enhanced rate capability and superior cyclic stability. The discharge capacities of PBM@NVOPF were 101.5 mA h g–1 (1 C) and 91.4 mA h g–1 (10 C), with a capacity retention of 84.3% after 500 cycles at 1 C, 20 °C. It also exhibited excellent cyclic stability at elevated temperature with an initial capacity of 109.5 mA h g–1 and a capacity retention of 78.8% after 200 cycles at 1 C, 55 °C. In comparison, uncoated PBM showed a discharge capacity of 105.7 mA h g–1 (1 C) and 76.7 mA h g–1 (10 C), with a capacity retention of only 42.0% after 500 cycles at 1 C, 20 °C. The high-temperature performance of bare PBM was very poor, and the capacity retention was only 35.7% after 40 cycles because of serious Mn/Fe dissolution which caused structural deterioration of PBM. NVOPF coating protected the PBM from suffering corrosion in the electrolyte, thus ensured the framework stability of PBM during long-term cycling and contributed to the excellent electrochemical performance.

Prussian Blue Analogues for Sodium‐Ion Batteries: Past, Present, and Future

“…Some inorganic materials have also been found that could also act as protective layers and conductors to enhance the electrochemical performance of PBA electrodes. For example, MnO 2 , [136] ZnO, [137] 2D MoS 2 , [138] Na 3 (VOPO 4 ) 2 F, [139] etc. have been reported that could form composites with PBAs, resulting in better rate and cycling performance.…”

Hexacyanoferrate‐Type Prussian Blue Analogs: Principles and Advances Toward High‐Performance Sodium and Potassium Ion Batteries

“…Ma's group reported a surface coating of NaMnHCF using Na 3 (VOP 4 ) 2 F (NVOPF), which is achieved by annealing a chemical precursor at 200 °C (in vacuum) ( Figure 16 a–f). [ 157 ] NVOPF is a well‐known NASICON‐type cathode having excellent rate capability and long‐term cycling stability. [ 160,161 ] Due to the high Na + conductivity and the uniform coating (30 nm) of NVOPF, the interface charge transfer is effectively enhanced, resulting in much better high‐rate performance of the NaMnHCF@NVOPF than the bare one although its low‐rate capacities are lower.…”

“…Reproduced with permission. [ 157 ] Copyright 2019, American Chemical Society. f) TEM image, g) electrochemical impedance, h) cycling performance, and i) rate performance of PB@PANI in nonaqueous NIBs.…”

Improved Cycling Performance of P2-Na0.67Ni0.33Mn0.67O2 Based on Sn Substitution Combined with Polypyrrole Coating

“…NaTMO 2 (TM = Fe, Co, Mn, Ni, Cr, etc. ), − polyanion-type materials, − and prussian blue analogues, − are widely investigated as cathode materials for SIBs. In particular, layered Na x TMO 2 compounds are intensely reported due to their easy synthesis methods and promising electrochemical properties. ,, …”