Oriented Formation of a Prussian Blue Nanoflower as a High Performance Cathode for Sodium Ion Batteries

Recently, the rational design and fabrication of Prussian blue (PB) cathodes with a unique morphology has been regarded as a promising way to improve the electrochemical properties for sodium ion batteries (SIBs). However, the shape-controlled preparation of PB still remains challenging up to now. Herein, we demonstrate an oriented self-assembly strategy to synthesize PB with three-dimensional (3D) flowerlike structures for the first time, experimentally realizing control of the flower size. And the formation mechanism of the flower structure is investigated through density function theory (DFT) calculations. It is found that the resulting PB nanoflowers perform because of superior inherent properties, which can afford low Fe(CN)6 vacancies and large specific surface areas. In addition, the special flowerlike PB exhibits superior rate capability (113 mAh g–1 at 1600 mA g–1) and excellent cyclic stability (close to 80% capacity retention after 400 cycles at 800 mA g–1). The enhanced performance can be attributed to the flowerlike structure at the nanoscale, which can provide robust structural integrity, enlarge the contact area between electrode and electrolyte, and improve the apparent diffusion coefficient of Na+ ions. In addition, the flower structures can retain their parent structure when undergoing multiple charge–discharge cycles, further confirming the structural stability.