A highly efficient chelating agent assisted the synthesis of Prussian blue analogues as a cathode material for sodium ion batteries

Prussian blue analog (PBA) is a common cathode material in sodium-ion batteries, which has the advantages of low synthesis price and high theoretical capacity. However, too fast reaction during its synthesis process can cause its lattice defects, which can negatively affect the cycling performance and rate performance of the battery. Here we developed a new chelating agent for Prussian blue synthesis, and investigate the effects of crystal shape as well as elemental content on the electrochemical properties of prussian blue. It is found that with the increase of cysteine usage, the Fe2+ content in prussian blue gradually increased, the Na+ content increased accordingly, and the interstitial water content within the crystal decreased, the prepared PB-75 sample reaches a discharge capacity of 149.13 mA h g(-1) at a current density of 50 mA g(-1). After cycling for 500 times at a high rate of 500 mA g(-1), it maintains 78.34 % of the capacity. Compared to sodium citrate, the quantity of cysteine has been significantly reduced, while still achieving favorable electrochemical properties. The findings indicate that cysteine serves as an efficient chelating agent in the synthesis of low-cost, high-capacity, and long-cycle-life sodium cathode materials.