(777g) Impact of Carbon BET Pore Volume On Sulfur Cathode Capacity

The effect of carbon surface area on capacity is investigated in cathodes for lithium sulfur batteries.  Lithium sulfur batteries have high specific capacity (a theoretical capacity of 1672 mAh/g-S); however, additives like carbon are needed to overcome sulfur’s low electrical conductivity. Cathodes were prepared at 12.5wt% to 68wt% sulfur on activated carbon having BET surface areas of 1220 to 3200 m²/g.  The utilization of the sulfur ranged from 33% to 83% of the theoretical loading with a good correlation to the accessible pore volumes.  The data substantiate that sulfur can be successfully accessed on carbon supports through both intra-particle and inter-particle adsorption.

Nitrogen gas adsorption was performed to obtain specific surface area and pore volume for carbons based on BET adsorption theory; this method is commonly used for characterizing activated carbons. After the characterization, the activated carbons underwent a heat treatment in the presence of excess sulfur at 200°C for 6 hours and followed by 300°C for 3 hours. The goal was to allow sufficient time for sulfur pore penetration over the initial 6 hour period, then remove excess sulfur during the final 3 hours.