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Theoretical Analysis of the Electrochemistry and Power Generation in Thermally Activated Batteries

Sharafi, Mona | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41113 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Gobal, Fereydoun
  7. Abstract:
  8. Study the potential and internal resistance of the electrochemical cells in different states of charge are important for practical and usage. Measurement of these parameters in an electrochemical cell is inseparably bound to the electrochemical resistance, temperature and also geometric states of different parts of the cell. In This project we focus on power and resistance of one kind of batteries called thermally activated batteries. These batteries are active after receiving heat and they are inactive at room temperature. Two of the most important models of these batteries that are discussed in this project are LiSi/ LiCl- KCl / FeS2 battery ( with liquid - molten salt electrolyte ) and Na/ Beta Alumina/S battery ( with solid electrolyte ). The first one operates at the temperature range of 400 to 700 ℃ and the second battery operate at a temperature range of 300 to 350℃ . In both cells , different phases form in the course of discharge. This project gives an overview of the electrochemical processes and mechanism of the transient reactions in these batteries, electrochemical potential of each stage , ∆H and ∆S of each reaction . Also the dependence of Nernstian potential and content ( Partial molar ) of electrochemical active materials in battery is studied. Using Butler – Volmer equation and Ficks Diffusion laws and calculation of ohmic resistance of each battery , we study the internal resistance (electron – transfer resistance and mass – transfer resistance) and the dependencies of the Potential – Current , Power – Current , Resistance – Current for each cell is investigated . Existance of porousity in anode and cathode structure that provide high surface areas for electrochemical reactions are considered in calculations the too . The Results show that , limiting Current for LiSi/ LiCl-KCl/FeS2 cell is 10.098 A and for Na/ Beta Alumina/S cell is 50.65 A. power Corresponding to these currents are 12.35 and 64.38 Watt respectively
  9. Keywords:
  10. Power Generation ; Thermal Batteries ; Molten Salt

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