A vacancy-free sodium manganese hexacyanoferrate as cathode for sodium-ion battery by high-salt-concentration preparation

Sodium manganese hexacyanoferrate (MnPBA) is attracting wide attention as an ideal low-cost cathode material for sodium-ion batteries (SIBs) because of high specific capacity, three-dimensional open framework, and low cost. However, some issues, including high [Fe(CN)6]4- vacancy concentration, a large amount of structural water in lattice, and nano-scale particles, hinder the practical application. Here, the effects of coprecipitation process under high-salt-concentration solution were systematically investigated to prepare a vacancy-free MnPBA with micro-spherical particle morphology. The sample (PBAT-80), prepared at ageing temperature of 80 °C for ageing time of 20 h, achieved high yield of 100 g L−1 (w/v = weight of production / liter of solution) and theoretical reversible capacity of 170 mAh g−1. Moreover, the relationship between crystallinity and thermal stability of MnPBAs was further investigated and the different storage mechanisms of distinct water molecules were identified. These results will be attractive for commercial applications of SIBs in large-scale energy storage systems.