High-performance Ni/Fe-codoped manganese hexacyanoferrate by scale-up synthesis for practical Na-ion batteries

Manganese hexacyanoferrate Prussian blue (Mn−PB) is regarded as promising cathode for sodium-ion batteries (SIBs) because of high energy density, low cost and facile preparation route. However, poor rate capability and short cycle life restrain practical applications of Mn−PB. In this work, a Na-rich Mn-based Prussian blue with codoped Ni and Fe (MnFeNi-PB) was prepared via a citrate sodium-assisted coprecipitation route. The Ni/Fe codoping significantly increases rate capability and cycling performance of the Mn−PB. Even at 100 C, the MnFeNi−PB exhibits a high capacity of 84.0 mAh g−1, with 72.8% capacity delivered relative to 0.1 C. The material also shows stable cycling with 65.6% capacity retained after 2000 cycles at a current density up to 5 C. Even under stringent circumstances, the MnFeNi−PB also exhibits a high capacity retention of 83.5% after 300 cycles at 45 °C and 92.1% after 700 cycles at −20 °C at 1 C. The enhanced rate capability and cycling performance is attributed to the increased electronic conductivity and stabilized crystal structure by Ni/Fe codoping. Scalable preparation of kilogram-grade MnFeNi−PB was realized using a 100 L reactor. Pouch-type Na-ion full battery with the MnFeNi−PB cathode shows stable cycling with 84.9% capacity retained after 200 cycles at 0.5 C/1 C current rate.