Supercapacitor composite

Shirshova N, Qian H, Shaffer MSP, Steinke JHG, Greenhalgh ES, Curtis PT, et al. Structural composite supercapacitors. Composites Part A Applied Science and Manufacturing. 2013 Mar 46(0) 96-10Z. 

Electrodeposition is a unique, versatile technique for fabrication of metal oxide, polymer, and composite electrodes for electrochemical supercapacitors. Composition, crystal structure, and morphology of the deposits can be easily manipulated by adjusting the electrodeposition parameters to achieve improved capacitive behavior. Current progress, however, is far from the commercial expectations for electrochemical supercapacitors. 

A supercapacitor composite electrode has been described (7). The composition is listed in Table 2.1. 

In the third paper by French and Ukrainian scientists (Khomenko et al.), the authors focus on high performance a-MnCVcarbon nanotube composites as pseudo-capacitor materials. Somewhat surprisingly, this paper teaches to use carbon nanotubes for the role of conductive additives, thus suggesting an alternative to the carbon blacks and graphite materials - low cost, widely accepted conductive diluents, which are typically used in todays supercapacitors. The electrochemical devices used in the report are full symmetric and optimized asymmetric systems, and are discussed here... 

Another interesting type of novel carbons applicable for supercapacitors, consists of a carbon/carbon composite using nanotubes as a perfect backbone for carbonized polyacrylonitrile. Multiwalled carbon nanotubes (MWNTs), due to their entanglement form an interconnected network of open mesopores, which makes them optimal for assuring good mechanical properties of the electrodes while allowing an easy diffusion of ions. 

Jurewicz K., Delpeux S., Bertagna V., Beguin F., Frackowiak E. Supercapacitors from nanotubes/polypyrrole composites. Chem Phys Lett 2001 347 36-40. 

HYBRID SUPERCAPACITORS BASED ON a-Mn02/CARBON NANOTUBES COMPOSITES... 

Another important aspect for a material to be used as electrode for supercapacitors is its electrochemical stability. In Figure 2, presenting the specific discharge capacitance versus the cycle number for the optimized a-Mn02-nl FO/CNTs composite in 2 molL 1 KNO3 (pH=6.5), it can be observed that the specific capacitance loss after 200 cycles is about 20%. 

Electronically conducting polymers (ECPs) such as polyaniline (PANI), polypyrrole (PPy) and po 1 y(3.4-cthy 1 cncdi oxyth iophcnc) (PEDOT) have been applied in supercapacitors, due to their excellent electrochemical properties and lower cost than other ECPs. We demonstrated that multi-walled carbon nanotubes (CNTs) prepared by catalytic decomposition of acetylene in a solid solution are very effective conductivity additives in composite materials based on ECPs. In this paper, we show that a successful application of ECPs in supercapacitor technologies could be possible only in an asymmetric configuration, i.e. with electrodes of different nature. 

In this paper, we report on the preparation of ECP composites based on carbon materials. In parallel with the development of the preparation processes and the electrochemical characterization of composites, we have performed an analysis of the supercapacitor cell design based on ECPs. 

Figure 4. Impedance spectra of a supercapacitor based on the PPy/CNTs composite before (a) and after performing 500 galvanostatic charge/discharge cycles (b).

Combined with appropriate amorphous carbon precursors graphite intercalation compounds could be used in one-stage process of production of carbon-carbon composites, which could possess attractive properties for such applications as supercapacitors elements, sorbents as well as catalyst supports and materials for energy- and gas-storage systems. 

Kumar, N.A., et al., Electrochemical supercapacitors based on a novelgraphene/conjugated polymer composite system. Journal of Materials Chemistry, 2012. 22(24) p. 12268-12274. 

In addition to mechanical reinforcement, the presence of nanocarbons in these hierarchical composites can also be used for piezoresistive structural health monitoring or damage evaluation by thermal imaging. Other functions of the nanocarbon, for example in structural supercapacitors, are likely to emerge in the near future. 

Fig. 11.9 Electrochemical properties of supercapacitors using the bare NiO and NiO/CNT (10 %) composite electrodes. The cyclic voltammetry(CV) behavior of (a) the bare NiO electrodes and (b) the NiO/CNT (10%) composite electrodes in 2M KOH aqueous solution (sweep rate, 10 mV/s) (reprinted with permission from Y. Lee etal., Synthetic Metals, 150, 2005,153-157).

Frackowiak E, Khomenko V, Jurewicz K, Lota K, Beguin F. Supercapacitors based on conducting polymers/nanotubes composites. Journal of Power Sources 2006 153 413-418. 

Debra R. Rolison is head of Advanced Electrochemical Materials at the Naval Research Laboratory (NRL). She received a B.S. in chemistry from Florida Atlantic University in 1975 and a Ph.D. in chemistry from the University of North Carolina at Chapel Hill in 1980 under the direction of Royce W. Murray. Dr. Rolison joined the Naval Research Laboratory as a research chemist in 1980. Her research at NRL focuses on the influence of nanoscale domains on electron- and charge-transfer reactions, with special emphasis on the surface and materials science of aerogels, electrocatalysts, and zeolites. Her program creates new nano structured materials and composites for catalytic chemistries, energy storage and conversion (fuel cells, supercapacitors, batteries, thermoelectric devices), and sensors. 

In the past five years, many ion conducting polymers and gel electrolytes have been investigated for EDLC application. Figure 15 shows the capacities of various carbon electrodes in SPE or gel electrolytes. The values listed in this figure do not satisfy the requirements for EV. However, it is expected that the requirements of supercapacitors for EV can be achieved by development of devices based on composite electrodes and gel electrolyte systems as described in this chapter. 

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