Investigation of Methods to Eliminate Voltage Delay in Li/SOCl2 Cells

摘要

A comparative study of thionyl chloride electrolytes containing LiAlCl4, Li2B10Cl10, or Li2B12Cl12 has been carried out by monitoring LiCl film growth on lithium samples stored in these electrolytes and by evaluating the startup and measuring the capacity of anode limited lithium/thionyl chloride cells. The film growth on lithium samples was monitored by galvanostatic pulse polarization, by weight gain analysis, and by examination under the scanning electron microscope. The film growth rate on lithium in Li2B10Cl10/SOCl2 was found to be comparable to that in pure SOCl2, about one tenth of that found in LiAlCl4/SOCl2. Storage for longer periods of time or higher temperatures caused thicker films to form. The polyhedral borate electrolyte produced smooth films on lithium with widely scattered crystals, instead of closely packed crystals as in LiAlCl4/SOCl2. Lithium/thionyl chloride cells containing Li2B10Cl10/SOCl2 started without delay at -20C, even after prolonged storage at elevated temperature. The polyhedral borate electrolyte also reduced self discharge by local cell reduction of the solvent against cell hardware connected to the anode.