The Effect of Various Contents of PTFE on the electrochemical performanceof the Acetylen Black-Polytetrafluoroethylene Composite Cathode in Lithium-Thionyl Chloride Batteries

Lithium-thionyl chloride cell (Li-SOCl2) has a metallic lithium anode and a liquid cathodecomprising a porous carbon current collector filled with thionyl chloride. It delivers a voltage of3.6V and is cylindrical in shape, in 1/2AA to D size, with spiral electrodes for power applicationsand bobbin construction for prolonged discharge. Among of all primary batteries, lithium thionylchloride batteries have the highest voltage and energy, longest storage period, and the least selfdischargerate. Those batteries are suitable for such long-term applications as power for electricdevices and electric power, water and gas meters, and especially as a backup power source formemory ICs. The cathode is made of highly porous Teflon-bonded carbon black whose electronicconductivity is needed for the charge transfer to take place. Thionyl chloride cathodic reduction iscatalyzed by the cathode surface when a load is connected. The pores of the carbon cathode retainboth the reactants and the products of this process.It is well known that in case of discharge, reaction products of LiCl, SO2 and S are created causedby chemical reaction [1]. Lithium chloride and Sulfur in a solid phase deposited to porous carboncathode. Therefore, cathode should provide enough pore space until completion of discharge andefficient structural design is required because speed of reaction products deposition is differentaccording to discharge current. PTFE increases the mechanical strength of porous carbon cathodebut also decreases the electrical conductivity of positive electrode and it occupies the pores ofacetylene black, that it can cause a drastic failure in the performance of the battery [2].The chief objective of this work is to evaluate the effect of various contents ofpolytetrafluoroethylene on electrochemical performance of positive electrode in lithium thionylchloride battery. Polarization curves indicate that the performance of a Li/SOCl2 battery is sensitive to the Acetylen-Black: PTFE (AB/P) ratio in the cathode. All electrochemicalcharacteristics were measured by SCRIBNER 850E test station. The electrochemicalmeasurements were carried out in a designed test cell which made by PTFE and 316 stainlesssteel. An optimal value of 40 wt. % PTFE in Acetylen-Black was found to be the best to balancethe structural strength of cathode and the battery electrochemical performance based onpolarization curve and discharge profile.

کلیدواژه ها:

Li-SOCl2 battery ، PTFE ، Porous carbon cathode ، Polarization curve ، DischargeProfile