Multi-metal doped high capacity and stable Prussian blue analogue for sodium ion batteries

Prussian blue analogues (PBA) are attractive positive electrode for sodium ion batteries due to their large interstitial sites and three-dimensional porous framework. However, they often suffer from irreversible phase transition upon charging and discharging, leading to fast capacity decay. In consideration that redox couples of Co2+/Co3+, Ni2+/Ni3+ and Fe2+/Fe3+ guarantee high capacity (similar to 150 mA h g(-1)), and Cu serves as a pillar to hold the PBA framework, here we synthesized a series of Cu, Co and Ni co-doped PBA, displaying high capacity and stable cycling performance with >98% capacity retention after 50 cycles.