Improved Reversible Capacity and Cycling Stability by Linear (N=O) Anions in Fe[Fe(CN)₅NO] as Sodium‐Ion Battery Cathode

Abstract

Prussian blue analogues (PBAs) are promising cathode materials for sodium‐ion batteries (SIBs) due to their tunable chemistry, open channel structure, and low cost. However, excessive crystal water and volume expansion can negatively impact the calendar lifetime of actual SIBs. In this study, a novel Iron nitroprusside (Fe[Fe(CN)5NO]) (PBN) was synthesized to effectively eliminate the detrimental effects of crystal water on the reversible capacity and cycling stability of PBA materials. Experiments and Density functional theory (DFT) calculations demonstrated that PBN has lower crystal water and volume expansion compared to Fe[Fe(CN)6] (PB). Also, N=O bond in PBN significantly reduces the diffusion potential of Na+ in the skeleton. Without any modification, the cathode material exhibited a capacity of up to 148.6 mAh g‐1 at 50 mA g‐1 while maintaining 102.9 mAh g‐1 after 200 cycles. This work expands our knowledge of the crystal structure of PBA cathode materials and facilitates the rational design of high‐quality PBA cathodes for SIBs.

Hollow Layered Iron-Based Prussian Blue Cathode with Reduced Defects for High-Performance Sodium-Ion Batteries

“…Lithium-ion batteries (LIBs) have emerged as crucial components within ESSs, given their high energy density, extended cycle life, and rechargeability. , However, the limited availability of lithium resources has been a drawback, hindering the further advancement of lithium-ion batteries. − Fortunately, sodium-ion batteries (SIBs) have garnered significant attention due to the abundance of sodium resources, coupled with their notable safety profile, robust rate capability, and commendable performance at low temperatures. , Leveraging the unique open framework structure, Prussian blue (PB) analogues offer plentiful sodium storage sites and expansive ion transport channels. This characteristic makes them highly suitable as cathode materials for SIBs. − PB analogues exhibit face-centered cubic structures, characterized by the molecular formula Na x M­[Fe­(CN) 6 ] 1– y ·* y · z H 2 O, where M represents transition metal elements such as Fe, Co, Ni, and Mn. Here, * denotes [Fe­(CN) 6 ] defects, and the parameters are defined as follows: the range of x is 0 < x < 2, and the range of y is 0 < y < 1. , According to the choice of M, the compound is referred to as M-based Prussian blue, abbreviated as M-PB.…”