Scalable Preparation of Mn/Ni Binary Prussian Blue as Sustainable Cathode for Harsh-Condition-Tolerant Sodium-Ion Batteries

Manganese-based Prussian blue has attracted enormous interest because of its high energy density, low cost, and easy synthesis. However, its practical use is limited for its poor rate capability and cycling performance. Here, a Mn/Ni binary Prussian blue was proposed to address this issue. The material with a 1:1 Mn/Ni ratio shows an optimized electrochemical performance when prepared via a Na2C2O4-assisted coprecipitation route at a high precursor salt concentration (0.5 mol L–1, named Mn0.5Ni0.5-0.5). Mn0.5Ni0.5-0.5 delivers a relatively high capacity of 69.4 mAh g–1 even at a current density rate up to 100 C (69% relative to 0.1 C) and a long cycle life with 85.3% capacity retained after 700 cycles at 5 C. The material functions well at both −20 and 45 °C at 1 C. Stable cycling can be realized after overcharge to 4.8 V (91.8%, 300 cycles at 1 C) and overdischarge to 1.2 V (89.7%, 300 cycles at 1 C). In addition, the coin cell group assembled by series/parallel-connected single cells also shows excellent cycling performance without any battery management system. A scalable preparation of kilogram-grade Mn0.5Ni0.5-0.5 is achieved, and the pouch-type full cell made from it also exhibits stable cycling.