Investigation on the promising electrode materials for rechargeable sodium ion batteries

Renewable energy sources, such as wind and sun, have attracted ever-growing attention due to exhaustion of fossil fuels and environmental concerns. Due to the intermittent nature of the renewable energy, the utilization of these energy sources relies on the availability of largescale energy storage systems (ESS). In some applications, lithium ion batteries (LIBs) are not suitable candidates because of the low abundance of lithium resources and their high cost. In comparison, sodium is abundant and cheap, and also has similar physical and chemical properties to lithium. Thus, more and more investigations on sodium ion batteries (SIBs) have been emerging in recent years. For the commercial application, the electrode materials need to meet the requirements of non-toxicity, low cost, high specific capacity, and long cycle life. In this doctoral work, promising red phosphorus and Prussian blue analogues were chosen as the objects of study, although their cycling performance is not yet satisfactory. Through reducing the particle size and forming composites with conductive carbon, P/carbon nanotube (CNT) and P/graphene nanoplate (GnP) composites were synthesized. By alloying with other elements, FeP, CoP, and Sn4+xP3@(Sn+P) alloy compounds were prepared. Through optimizing the structure and combining the electrode materials with conductive polyporrole, a series of different Na-enriched Na1+xFeFe(CN)6 and multi-functional polypyrrole coated Na1.72MnFe(CN)6 composites were synthesized, respectively. Moreover, the influences of the morphology and the sodium storage mechanism of these electrode materials were investigated through various characterization techniques, including field emission scanning electron microscopy, transmission electron microscopy, synchrotron X-ray powder diffraction, Mössbauer spectroscopy, Raman spectroscopy, magnetic measurements, thermogravimetric analysis, X-ray photoelectron spectroscopy, and inductively coupled plasma analysis.