Achieving a superior Na storage performance of Fe‐based Prussian blue cathode by coating perylene tetracarboxylic dianhydride amine

Fe‐based Prussian blue (Fe‐PB) cathode material shows great application potential in sodium (Na)‐ion batteries due to its high theoretical capacity, long cycle life, low cost, and simple preparation process. However, the crystalline water and vacancies of Fe‐PB lattice, the low electrical conductivity, and the dissolution of metal ions lead to limited capacity and poor cycling stability. In this work, a perylene tetracarboxylic dianhydride amine (PTCDA) coating layer is successfully fabricated on the surface of Fe‐PB by a liquid‐phase method. The aminated PTCDA (PTCA) coating not only increases the specific surface area and electronic conductivity but also effectively reduces the crystalline water and vacancies, which avoids the erosion of Fe‐PB by electrolyte. Consequently, the PTCA layer reduces the charge transfer resistance, enhances the Na‐ion diffusion coefficient, and improves the structure stability. The PTCA‐coated Fe‐PB exhibits superior Na storage performance with a first discharge capacity of 145.2 mAh g−1 at 100 mA g−1. Long cycling tests exhibit minimal capacity decay of 0.027% per cycle over 1000 cycles at 1 A g−1. Therefore, this PTCA coating strategy has shown promising competence in enhancing the electrochemical performance of Fe‐PB, which can potentially serve as a universal electrode coating strategy for Na‐ion batteries. Perylene tetracarboxylic dianhydride amine layer has been successfully covered on the Fe‐based Prussian blue (Fe‐PB) surface for the first time, which increases the specific surface area and reduces crystal water with vacancies. Also, the coating layer enhances the transport ability of sodium ions with enhanced electronic conductivity, while inhibiting the dissolution of metal ions of electrodes. As a result, the as‐synthesized Fe‐PB have shown excellent cycling stability and impressive high capacity as sodium‐ion battery cathodes.