Investigation on iron based Prussian blue cathode materials for sodium ion batteries

The global climate change and energy shortage have been critical issues during the past few decades, utilizing renewable clean energy through energy storage devices is considered as an effective way to address these problems. Since the advent of commercial lithium ion batteries (LIBs) from 1990, the LIBs have dominated the market of portable electronic devices and electrical vehicles in our daily life. Nevertheless, the increasing price of lithium might hinder their further large scale application because the uneven distribution and limited lithium resource on earth. To meet the requirements of large scale electric energy storage (EES), sodium ion batteries (SIBs) are considered as an ideal alternative, owing to the similar chemical and physical properties with LIBs, abundant sodium resources and the cheap price. Developing low cost cathode materials with potential to be mass produced, excellent rate capability and long term cycle life is needed for real application of SIBs in the future. Iron based Prussian blue analogues (Na2 xFeFe(CN)6, Fe based PBAs) are promising cathode materials for SIBs, due to low cost Fe resource and easy preparation method (co precipitation) with potential to achieve large scale production. Moreover, the high temperature calcination is not required during the synthesis process of Fe based PBAs, which could dramatically reduce their manufacturing cost. In this doctoral work, low cost Fe based PBAs are selected as the investigated target, the synthesis process, crystal structures, electrochemical performances, phase evolutions upon sodium ion (de)intercalations, and sodium storage mechanism have been studied, through various characterization methods, including powder X ray diffraction (PXRD), in situ synchrotron PXRD, scanning electron microscope (SEM), scanning transmission electron microscopy (STEM), Fourier transform infrared spectroscopy (FT IR), X ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), inductively coupled plasma (ICP) spectroscopy and theoretical calculations.