Browsing by Author "Azad, Atia"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Probing the Structure and Evolution of Anode Materials in Thermal Batteries
    (Cranfield University, 2020-11-30 13:39) Azad, Atia
    High-temperature thermal batteries use lithium-silicon alloys as the anode material. Li13Si4, Li7Si3 and Li12Si7 alloys are studied to determine if phase transitions occur or if the alloys become amorphous between room temperature and 500◦C (the typical operating temperature of thermal batteries). These alloys are synthesised by reacting lithium metal and silicon powder at elevated temperature inside an evacuated quartz ampoule. The samples’ structural changes are investigated at elevated temperatures using in situ powder neutron diffraction. This is carried out on the Polaris diffractometer at ISIS facility, Rutherford Appleton Laboratory, UK. The results of the neutron scattering experiment seem to imply that the alloys do not become amorphous at 500◦C and no phases transitions occur in the temperature range. Further work is required to determine if phase transitions occur below room temperature. The work so far has presented a simple method of synthesising these alloys and gives information on the lack of phase transitions between room temperature and 500◦C.
  • Thumbnail Image
    ItemOpen Access
    Synthesis and Characterisation of Lithium Silicides
    (Cranfield University, 2022-01-10T17:46:09Z) Azad, Atia
    Thermal batteries are primary (non-rechargeable) batteries. To activate the battery, a pyrotechnic heat source melts the solid electrolyte to a molten salt at high temperature (typically around 500°C). The battery activation starts by a pyrotechnic source such as Fe/KClO4. Thermal batteries are made from a positive electrode material such as FeS2, a molten salt electrolyte such as LiCl:KCl and a negative electrode material. Li13Si4 is the preferred anode material for thermal batteries. The electrolyte is mixed with a binder material. MgO is a typical binder. The positive electrode material attracted attention with the aim of having a high capacity, a high voltage and good thermal stability. Previous work focused on new cathode materials and investigated battery discharge mechanisms. The negative electrode material is of interest because the high temperature structures and phase transitions have not been studied in the current literature. In this work, lithium-silicon phases were synthesised by a solid-state reaction between lithium metal and silicon powder inside evacuated quartz ampoules. The phases were characterised by powder neutron diffraction, carried out on the Polaris diffractometer at ISIS facility, Rutherford Appleton Laboratory, UK, differential scanning calorimetry (DSC) and magnetic measurements on the superconducting quantum interference device (SQUID). The lithium-silicon phases are remarkably stable at high temperature and remains crystalline, with phase transitions only occurring below room temperature.