The use of Polyvinylpyrrolidone (PVP) as Electrocatalyst in Lithium/Thionyl Chloride (Li/SOCl2) cells

Lithium/thionyl chloride (Li/SOCl2) battery, which is high energy density, high operation voltage, long storage life, and wide operation temperature range (−55∼85°C), has been widelyused to power various electronic devices for industrial and military applications [1,2]. During the discharge of the Li/SOCl2 battery, the electrode reaction of battery is as follows: Li  Li+ + e 2SOCl2 + 4e 4Cl− + SO2 + S In the above reaction, the Li+ ions around the lithium electrode migrate to the carbon electrodesurface and react with the Cl− anion: Li+ + Cl−  LiCl Due to the low solubility of lithium chloride crystallite in SOCl2 electrolyte, as the discharge goeson, the amount of lithium chloride crystallites deposited on the carbon electrode is increased. It can affect the performance of the battery. One possible approach to enhance the cell performance is the addition of catalyst molecules which must be readily oxidizable/ reducible and acceleratethe rate of electron transfer. In our report, the high energy of Li/SOCl2 battery may due to therate enhancement of SOCl2 reduction reaction and the retardation deposition of lithium chloride crystallite by adding a polymer called Polyvinylpyrrolidone. Polyvinylpyrrolidone (PVP), alsocommonly called polyvidone or povidone, is a polymer made from the monomer Nvinylpyrrolidone[3], PVP have been used as catalysts to catalyze lithium/thionyl chloride (Li/SOCl2) cell. The catalytic activity of PVP derivatives to Li/SOCl2 cell is evaluated by theelectrochemical techniques of the cell whose electrolyte contains the PVP. The catalytic effectsof PVP polymer on the reduction of thionyl chloride at carbon electrode have been evaluated in three electrode system by cyclic voltammetric techniques[4].A two-step electron transfer process, mechanism is proposed and proved by the cyclic voltammetry. Fig.1 is a comparative cyclic voltammograms (CVs) of the Li/SOCl2 cellwith/without 2 mg PVP in 1 M LiAlCl4/SOCl2. The results of cyclic voltammetry show that theadding of PVP improves the reduction rate of SOCl2, This maybe due to the reason that the Li+ ion is easily to coordinate with PVP

کلیدواژه ها:

Polyvinylpyrrolidone ، Lithium thionyl chloride cell ، Catalyst ، Cyclic voltammetry