Use of carbon filaments in place of carbon black as the current collector of a lithium cell with a thionyl chloride bromine chloride catholyte

Submicron carbon filaments (ADNH, Applied Sciences Inc.) used in place of carbon black as porous reduction electrodes (i.e., current collectors) in plate and jellyroll configurations in carbon limited lithium batteries with the BCX (bromine chloride in thionyl chloride) catholyte gave a specific capacity (at 2 V cut-off) of up to 8700 mAh/g of carbon, compared with a value of up to 2900 mAh/g of carbon for carbon black. The high specific capacity for the filament electrode is partly due to the filamentsʹ processability into sheets as thin as 0.2 mm with good porosity, acceptable mechanical properties and without binder, and partly due to the high catholyte absorptivity and high rate of catholyte absorption of the filament electrode. Use of solvent-cleansed filaments in place of as-received filaments in making electrodes increased the packing density, thus decreasing capacity per g of carbon. The BCX catholyte acted as a cleanser anyway, due to the thionyl chloride in it. The specific capacity per cm3 of carbon and that per unit density of carbon were also increased by using carbon filaments in place of carbon black, provided that the filament electrode was not pressed after forming by slurry filtration. Though no binder was needed for the filament plate electrode, it was needed for the filament jellyroll electrode. The Teflon™ binder increased the tensile strength and modulus, but decreased the catholyte absorption and rate of absorption. The filament electrode exhibited 405 less volume electrical resistivity than the carbon black electrode, both without a binder.