Balance Control of Capacity and Stability of the Bimetallic Prussian Blue Cathode for High-Performance Sodium-Ion Batteries

Prussian blue analogs (PBAs) are one of the most promising cathode materials for sodium-ion batteries (SIBs) due to their open three-dimensional backbone structure and well-developed sodium-ion diffusion channels. However, the practical application of PBAs still faces great challenges, such as a high content of anionic vacancies and poor structural stability. In this work, we synthesized nickel-manganese bimetallic PBAs by a simple coprecipitation method, and adjusting the ratio of nickel (electrochemically inert element) and manganese (electrochemically active element) can effectively control the charging and discharging depth of the battery. By precisely optimizing the ratio between the two, the charging and discharging performances can be reasonably adjusted, thus improving the overall efficiency and stability of the battery. As the cathode material of SIBs, bimetallic PBA shows excellent specific capacity, outstanding multiplicity performance, and long-term cycle stability. Especially, the capacity retention of the Ni_0.1Mn_1.9HCF electrode can be maintained as high as 70.5% (∼55.4 mAh g^-1) after 100 cycles at a higher current density of 500 mA g^-1. In addition, the cycling stability of all materials was further significantly improved in eutectic electrolytes. A novel and simple strategy can provide an effective method for the balance control of capacity and cycling stability of the PBA cathode for SIBs.