Long cycle life rechargeable lithium/titanium disulfide cells

Abstract

Lithium/titanium disulfide (Li/TiS/sub 2/) cells are being developed for long life rechargeable applications. The effects of cathode thickness, packing density, percent carbon, electrolyte type, and anode type on cycle life were evaluated. Cathode thickness was found to have the most dramatic effect on cycle life, followed by cathode packing density and electrolyte type. The cycle life of AA Li/TiS/sub 2/ cells increased substantially as the cathode thickness decreased. At 100% depth of discharge (DOD), over 600 cycles have been demonstrated at 500 mA discharge and 125 mA charge rates. At 50% DOD, 830 cycles have been achieved. AA cells have been discharged at rates up to 2.0 A while maintaining over 60% cathode utilization. Microcalorimetry experiments have been used to estimate a self-discharge rate of less than 1% per month for cycled cells at 25 degrees C. Safety testing indicates that fresh cells do not vent when crushed or externally short circuited but may vent after cycling. Heat tape tests showed that venting did not occur below 170 degrees C.< >