A novel border-rich Prussian blue synthetized by inhibitor control as cathode for sodium ion batteries

The performance of a Prussian blue cathode is affected by its structure and stability. Through the inhibitor and temperature control, the border-rich structure was obtained, which provides a good contact between electrode-electrolyte interfaces and increases the transmission path for Na+ ions. In addition, the as-prepared sample with rhombohedral phase demonstrated lower band gap and lower energy barrier for Na+ ions insertion. Benefiting from the kinetics optimization, the as-prepared electrode exhibited initial capacity of 120 mA h g−1 and maintained nearly 80% after 280 cycles at current density of 100 mA g−1. This electrode also exhibited good rate performance about 60 mA h g−1 at rate of 10 C. The structural stability is also related to the formation of the passivation layer during the charge-discharge process. The optimized passivation layer not only protects the electrode form the adverse side reactions at high voltage but also delivers low interface impedance. It can be inferred that the passivation layer plays a positive role in long cycling performance. When the as-prepared electrode was measured in an electrolyte with FEC additive, it exhibited a high capacity retention rate of 79% after 500 cycles.