Development of high capacity composite anode materials for rechargeable lithium/sodium ion battery

Renewable energy resources such as solar energy and wind energy can be used in generating electric instead of traditional fossil fuels. These sources of energy are not constant, however. Low-cost rechargeable lithium ion batteries and sodium ion batteries can be used as energy storage devices to smooth out the intermittency of the renewable energy, besides acting as new, clean, and portable energy resources themselves, which can be applied in mobile phones, laptop computers, electric cars, etc. My Master’s thesis work is focused on the study of anode materials for LIBs and NIBs. The obtained materials are Si/C/Fe/Sn nanocomposite and Sn/SnO2@C composite nanofibers as anode materials for the lithium ion battery and FeP/graphite as anode material for the sodium ion battery. The Si/Fe/Sn/Carbon composite was prepared by the simple high energy ball milling method. Based on the X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy results, the obtained frogspawn-like composite is a composite of silicon crystals embedded in an amorphous matrix. The frogspawn-like structure can deliver outstanding electrochemical performance, since the amorphous matrix can efficiently accommodate the volume changes; the “spawn” has electrically conductive shells continuously connected to each other, which are beneficial for improving the electrical conductivity of silicon; and the continuous carbon network can restrict the agglomeration of silicon and tin during prolonged cycling. The initial capacity of the Si/Sn/Fe/C composite tested in lithium bis(fluorosulfonyl)imide (LiFSI) electrolyte is 1274 mAh g-1, and even after 1000 cycles, the capacity remains high at 620 mAh g-1, which is excellent.