טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentLeviatan Tomer
SubjectDevelopment of an Oxide Based Electrode for Thermal
Batteries
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Shlomo Berger
Full Thesis textFull thesis text - English Version


Abstract

Thermal Batteries are pyrotechnically initiated molten salt batteries providing high power, extremely long shelf life (over 20 years), fast activation time, wide range of operational temperatures and high reliability. They are widely used in military and space applications. A Thermal Battery consists of a stack of cells. Each cell consists of an anode, a cathode, electrolyte and pyrotechnic pellets. The electrolyte consists of a solid salt mixture having a melting temperature in the range of 625-725°K. Activating the thermal battery ignites the pyrotechnic pellets which provide heat to melt the solid electrolyte and cause a high ionic mobility. Thermal batteries electrodes are required to deliver the electric current to the outside load with minimal losses at working temperatures as high as 9730K.  Solid CuO is potentially a good candidate of a thermal battery electrode due to its high thermal stability and good electric conductivity. Green compacts were prepared by cold pressing (150 ton hydraulic pressure) of CuO powders reaching a density of about 72% of the theoretical value (6.48gr/cm3).  The green compacts have a wide distribution of particles size that spans between 20mm and 100mm with an average value of about 47mm. XRD analysis confirms that the green compacts consist of a randomly oriented CuO crystalline phase having the octahedral unit cell structure. The electrical conductivity of the CuO green compacts was studied under a controlled atmosphere at temperatures between 2980K to 10500K under the applied voltage of 1V and frequencies between 42Hz and 1MHz using an impedance analyzer. The electrical measurements show that the electrical conductivity of the CuO green compacts is thermally activated. A major increase of the electrical conductivity (of about 600 times compared to the RT value) is recorded above 6230K at frequencies below 500 KHz reaching a maximum value at about 7230K.  At frequencies lower than 500 KHz, the electrical conductivity is mainly attributed to the mobility of ions. At frequencies higher than 500 KHz up to 5 MHz, the electrical conductivity is attributed to the mobility of electrons/holes. Single cell discharge results show that the CuO electrode has a higher voltage potential then commonly used Pyrite, of about 0.25 volts and the same electrical capacity. The resistance of the cell with the CuO electrode is higher by 50% compared to the cell with the Pyrite electrode. The potential application of the CuO electrode in thermal batteries is discussed in this work.