Fig. 2 Continuous discharge curves of the test cells at 100 mA
all the operating parameters were kept constant to facilitate comparison of various carbons
samples. Cathode potential with reference to Ag/AgCl electrode was monitored at various time
intervals, and the result obtained is plotted in Fig. 2. From Fig. 2, it is understood that Black
Pearls 2000 performs better than acetylene black, the commonly used carbon in commercial dry cells
and the other carbon samples tested. Composite carbon stands better in performance next to Black
Pearls 2000. Thus, the test cell performance was found to follow the order: Black Pearls 2000 >
Composite Carbon > Vulcan XC 72 > Acetylene Black.
The above trend in discharge characteristics can be explained from the physical parameters of these
materials evaluated by surface area (Table 1) and related parameters. Black Pearls 2000 has the
highest surface area and pore volume than other carbon powders studied here. The reason attributed
for the improved electrochemical performance of the Black Pearls 2000 may be the increased
electrolyte uptake and retention of large amount of electrolyte [11, 12] an effect due to the
improved physical characteristics of the carbon powder. The better performance of composite carbon
can also be explained in a similar way, due to its higher surface area and larger total pore volume
than the Vulcan XC72 and acetylene black.
Furthermore, cathode mixture from a fresh battery with
R6 configuration was removed and reassembled in our test
cell, and the discharge characteristics were studied at 150- mA current load. This analysis was
made to compare and appreciate the discharge characteristics of our cathode mix synthesized with
Black Pearls 2000 and composite carbon mixture individually with the commercial R6 battery cathode
mix, the result of which is given in Fig. 3. Normally small electronic gadgets require around 150
mA for operation, and hence, for the same reason, this particular study has been performed at 150
mA. From Fig. 3, it is interesting to note that the cathode mix with Black Pearls
2000 and composite carbon exhibited better performance than the cathode mixture from the commercial
R6 battery.
Conclusion
The discharge behavior of various carbon powders, such as acetylene black, Vulcan XC72, Black
Pearls 2000, com- posite carbon consisting of 50% acetylene black and 50% Black Pearls 2000 mixed
with EMD were studied in test cells and compared. The performance of the cathode mixture from
commercial R6 battery was also compared with Black Pearls 2000 and with composite carbon mixed in
EMD. It was concluded that the cathode mixture with Black Pearls 2000, though more expensive, was
found to give superior cell performance than the popular acetylene black and commercial cathode
mixture. Composite carbon,
Table 1 Physical parameters of various carbon powders
No. Carbon type Surface area (m2/g) Particle size (nm)
Total pore volume (ml/g) Average pore radius (oA)
1 Acetylene black 59.00 40
0.0601 20.37
2 Black pearls 2000 1453.25 15
0.9290 12.78
3 Composite carbon 627.23 22
0.4184 13.34
4 Vulcan XC72 207.13 30
0.1899 18.34