Analysis of the Lithium Sulfur Dioxide System at ultra-high rate discharges

The major objective of this program was to study the effects of electrolytes in Li/SO2 cells, for use in high rate abusive discharge conditions. Five electrolytes were investigated based on previous differential thermal analysis (DTA) results. A standard type electrolyte using acetonitrile (AN) was included in the program for comparison. The work was performed at Duracell International Inc. using LO26SX cells made at the Lithium Systems Division in North Tarrytown, New York. The cells were filled and tested at the Laboratory for Physical Science in Burlington, Massachusetts. Two electrolytes, AN(standard) and AN/PC (90/10) were found satisfactory for use in high rate abuse discharge conditions. Cells with AN/AA (90/10) electrolyte were satisfactory when fresh but these cells evolved CO2 on storage at 55 C and 72 C which led to severe cell-leakage. The remaining electrolytes, AN/BL/DME (85/10/5), PC/DME (50/50) and BL/DME (50/50), were regarded unsatisfactory for use in Li/SO2 cells for high rate abusive discharge conditions. The use of copper foil as the anode substrate was studied in LO26SX cells filled with the standard AN electrolyte. These cells were effective in reducing the sharp voltage reversal during abusive forced discharge at 2.0A at -30 C. The abuse resistance of these cells was at least as good as that of the standard cells.