High Crystalline Prussian White Nanocubes as a Promising Cathode for Sodium-ion Batteries

Prussian blue and its analogues (PBAs) have been recognized as one of the most promising cathode materials for room-temperature sodium-ion batteries (SIBs). Herein, we report high crystalline and Na-rich Prussian white Na2CoFe(CN)(6) nanocubes synthesized by an optimized and facile co-precipitation method. The influence of crystallinity and sodium content on the electrochemical properties was systematically investigated. The optimized Na2CoFe(CN)(6) nanocubes exhibited an initial capacity of 151mAhg(-1), which is close to its theoretical capacity (170mAhg(-1)). Meanwhile, the Na2CoFe(CN)(6) cathode demonstrated an outstanding long-term cycle performance, retaining 78% of its initial capacity after 500 cycles. Furthermore, the Na2CoFe(CN)(6) Prussian white nanocubes also achieved a superior rate capability (115mAhg(-1) at 400mAg(-1), 92mAhg(-1) at 800mAg(-1)). The enhanced performances could be attributed to the robust crystal structure and rapid transport of Na ions through large channels in the open-framework. Most noteworthy, the as-prepared Na2CoFe(CN)(6) nanocubes are not only low-cost in raw materials but also contain a rich sodium content (1.87Na ions per lattice unit cell), which will be favorable for full cell fabrication and large-scale electric storage applications.