Nanoscale Morphology Control of Na-Rich Prussian Blue Cathode Materials for Sodium Ion Batteries with Good Thermal Stability

Sodium-ion batteries (SIBs) are normally investigated at room temperature (RT). However, the application of electrical vehicles (EVs) may work at high/low temperatures in a harsh environment. Herein, Na-rich Prussian blue (PB) is synthesized by controlling the Na+ ion concentration during the synthesis process. TGA, XRD, IR, and SEM are used to investigate the transition of the nanoscale structure and the surface morphology of PB at various Na contents. The electrochemical properties have been investigated at RT, 40 °C, 60 °C, and the high temperature of 80 °C. PB-4M exhibits a specific capacity of 130 mAh/g at RT and 120 mAh/g at 80 °C. At 80 °C, PB-4M can still deliver a reversable specific capacity of 57 mAh/g at 2 C after 500 charge–discharge cycles, which makes it possible to utilize PB as a commercial cathode in future EVs at high temperature.