The reduction of sulfuryl chloride at Teflon-bonded carbon cathodes

Polarization and discharge curves were measured for sulfuryl chloride reduction at Teflon-bonded carbon cathodes fabricated using a number of different carbon powders. Lithium chloroaluminate was utilized as electrolyte solute. At moderate current densities, cathode polarization tends to normalize with respect to Brunauer, Emmett, Teller (B.E.T.) surface area of the carbon. Cathode life increases with increased porosity of the electrode. The porosity is required for good accommodation of product LiCl. A formulation incorporating both high B.E.T. area and porosity was developed and found to provide good electrochemical performance against lithium counter-electrodes. When sulfuryl chloride is reduced at the optimized cathode (against a lithium anode), the main products of reaction are LiCl (which is quantitatively) deposited within the electrode's pores) and SO2. This suggests the overall cell reaction: 2 Li-SO2Cl2 yields 2 LiCl-SO2. The addition of Cl2 or SO2 to the electrolyte causes decrease or increase of cathode polarization, respectively. This may be taken as evidence that the reduction, at moderate current densities, occurs through a Cl2 intermediate resulting from heterogeneous decomposition of SO2Cl2. Reduction of undissociated SO2Cl2 may occur at high current densities or after the active area of the electrode is significantly reduced through deposition of product LiCl.