Nanocoating Achieving Hydrophobic Prussian Blue as Stable Cathode in Sodium-Ion Batteries

As a promising cathode material in sodium-ion batteries, Prussian blue (PB) suffers from humid sensitivity during electrode manufacturing, which leads to structural and electrochemical instability. Herein, we design a moisture-proof Prussian blue via surface modification of hydrophobic octadecylamine (ODA) chains with a thickness of ∼6 nm. The hydrophobic Prussian blue (PB@TA@ODA) exhibits excellent sodium storage performance, owing to its high stability in humid environments. After exposure to a humid environment for 7 days, PB@TA@ODA-7D can provide a reversible capacity of 145 mAh g–1 at 1 C and deliver 94 mAh g–1 at 30 C. After 100 cycles at 1 C, it still retains 111 mAh g–1. Further investigations show that the hydrophobic ODA chains can protect PB from H2O attacking the high-spin Fe, thus maintaining structural stability in a humid environment. The hydrophilic strategy proposed in this work can effectively promote the processability of PB in electrode manufacturing, which is crucial for its practical application in sodium-ion batteries.