Highly crystalline sodium manganese ferrocyanide microcubes for advanced sodium ion battery cathodes

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2019, Vol.7 (39), p.22248-22256
• Main Authors: Peng, Fangwei, Yu, Lei, Gao, Pengyue, Liao, Xiao-Zhen, Wen, Jianguo, He, Yu-shi, Tan, Guoqiang, Ren, Yang, Ma, Zi-Feng
• Format: Article
• Language: English
• Subjects: Batteries; Cathodes; Crystal defects; Crystal morphology; Crystal structure; Crystallinity; Crystals; Cycles; Electrical properties; Electrochemical analysis; Electrochemistry; Electrode materials; Electrodes; Ferrocyanide; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Iron cyanides; Manganese; Microstructure; Monoclinic lattice; Morphology; Pigments; Reaction kinetics; Side reactions; Single crystals; Sodium; Sodium-ion batteries
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c9ta08603j

The microstructure and morphology of the crystal play an important role in the physical and electrochemical properties of electrode materials. Here we report a highly crystalline microcube structure of Na-rich Prussian white Na 1.92 Mn[Fe(CN) 6 ] 0.98 for sodium ion battery cathodes. The obtained structure features high crystallinity of the monoclinic structure with an average cubic size of 3-5 μm. Because of the improvement on microstructural and electrical properties, the cathode design enables promising electrochemical performance. The electrode exhibits an outstanding rate performance with reversible capacities of 152.8 mA h g −1 (10 mA g −1 ), 128.1 mA h g −1 (100 mA g −1 ), 118.7 mA h g −1 (500 mA g −1 ) and 110.3 mA h g −1 (1000 mA g −1 ). It also exhibits a good cycling performance with a capacity retention of 82% after 500 cycles at 100 mA g −1 . More importantly, the XRD analysis reveals a highly reversible monoclinic-cubic-monoclinic structural evolution of the cathode upon Na + extraction/insertion. The good rate and cycling performance can be attributed to the robust crystal structure with few defects and fast Na + transfer kinetics. The high purity single crystal morphology can also reduce the side reactions on the electrode/electrolyte interface. Highly crystalline Na 1.92 Mn[Fe(CN) 6 ] 0.98 microcubes with superior performance for advanced sodium ion battery cathodes were prepared using EDTA-MnNa 2 as the precursor.