Phosphorous-enriched Carbons Increase Performance and Energy Density of Supercapacitors
11 April 2009
| Energy density of the P-carbon supercapacitors compared to commercial carbon (Norit). Credit: ACS. Click to enlarge. |
Researchers from Australia, Ukraine and Spain have found that phosphorus-rich microporous carbons (P-carbons) used in supercapacitors exhibit enhanced supercapacitive performance, are capable of stable operation at voltages larger than 1.3 V in H2SO4 and can support an energy density of up to 16 Wh/kg compared to around 5 Wh/kg for conventional commercial carbon. A paper on their work is published in the 15 April issue of the Journal of the American Chemical Society.
Although supercapacitors, which store energy in an electric field rather than obtaining it from a chemical reaction, can provide quick, massive bursts of energy—ideal for acceleration with an electric drive—their energy density is much lower than that of batteries. Much work is underway to either increase the energy density of supercapacitors (e.g., earlier post), enhance the discharge rate of batteries to approach that of supercapacitors (e.g., earlier post), or to combine supercapacitors and batteries in a single energy storage system, cost-effectively leveraging the best aspects of each (e.g., earlier post).
The team, led by Dr. Denisa Hulicova-Jurcakova at the University of Queensland (Australia), ARC Centre of Excellence for Functional Nanomaterials, prepared P-carbons by using phosphoric acid (H3PO4) activation of three carbon precursors: fruit stones (FS), styrene-divinylbenzene copolymer (SC) and bismelimido-diphenylmethane-divinylbenzene copolymer (BC). They used commercial microporous carbon Norit (Norit RB3) as a comparison.
In testing, they obtained significantly higher capacitance values from P-carbons than from P-free versions of the same carbons or Norit, with the best-performer (BC-P) possessing a capacitance of 220 F/g, compared to Norit at 140 F/g.
Most interesting and extraordinary is that the supercapacitors from P-carbons could operate at potentials larger than the theoretical decomposition potential of water (1.23 V)...BC-P provides almost rectangular shape voltammograms unlike Norit, which could not withstand 1.2 V as evidenced by the electrolyte decomposition peak above 1 V.
...The widening of the cell voltage has a great impact on the energy density of the supercapacitor as it is proportional to the square of the cell voltage. The combined effect of large capacitance and wide operational voltage of P-carbons results in energy densities 3 times larger than that of Norit and reaching 16.3 Wh/kg at the power density of 33 W/kg in BC-P. FS-P shows the most stable performance maintaining 8.2 Wh/kg at 3100 W/kg.
—Hulicova-Jurcakova et al. (2009)
The researchers believe that this is the first finding that carbons enriched with phosphorus groups and optimized porous structure have a uniquely high and stable performance in electrochemical energy storage devices such as supercapacitors.
Resources
Denisa Hulicova-Jurcakova, Alexander M. Puziy, Olga I. Poddubnaya, Fabian Suárez-García, Juan M. D. Tascón and Gao Qing Lu (2009) Highly Stable Performance of Supercapacitors from Phosphorus-Enriched Carbons. J. Am. Chem. Soc., 131 (14), pp 5026–5027 doi: 10.1021/ja809265m
I am hoping for the the "spin" or magnetic battery. 'The secret behind this technology is the use of nano-magnets to induce an electromotive force..."
http://www.sciencedaily.com/releases/2009/03/090311162807.htm
Posted by: SJC | 11 April 2009 at 09:51 AM
If this pans out, it could be really good news - you could have much more efficient regenerative braking systems at lower cost, and much smaller rail guns.
Posted by: mahonj | 12 April 2009 at 01:18 AM
With a 300% + increase in energy density, super-caps could become a winning solution when combined with rugged, much lower cost, high performance lead batteries such as the Firefly etc
Posted by: HarveyD | 15 April 2009 at 09:53 AM