Na2NixCo1 − xFe(CN)6: A class of Prussian blue analogs with transition metal elements as cathode materials for sodium ion batteries

• Na2NixCo1 − xFe(CN)6 was used as a new type cathode for sodium ion batteries.
• The appropriate proportion of nickel and cobalt is 4:6.
• PBN0.4C0.6 exhibits a discharge capacity of 91.8 mAh g− 1 at 50 mA g− 1.
• Significantly increased rate performance with 68.5 mAh g− 1 at 800 mA g− 1

A new class of Prussian blue analogs, Na2NixCo1 − xFe(CN)6 (0 ≤ x ≤ 1) with various nickel-to-cobalt ratios (from pure nickel to pure cobalt with a 10% increase in Co content for each sample) was prepared and tested as cathode materials for sodium ion batteries. The Na2Ni0.4Co0.6Fe(CN)6 sample showed the best electrochemical performance, with an initial discharge capacity of 90 mA h g− 1 and reversible capacity of 80 mA h g− 1 after 100 cycles. Even at a higher rate of 800 mA g− 1, a good initial discharge capacity of 74 mA h g− 1 was obtained.