Hybrid and symmetric supercapacitors, especially with water electrolyte, are modern chemical power sources and widely used as primary or backup power sources in different devices. In particular, such supercapacitors are used in the “eco-friendly” vehicles and vehicles with a hybrid motor. Therefore increasing the supercapacitor characteristics is the actual aim. Carbon nanomaterials are used as active substances of “−” electrode of hybrid supercapacitors and determination of different parameters influencing on they electrochemical activity has high actuality.
The aim of this investigation is the comparative investigation of the electrochemical activity of different carbon nanomaterials based on the morphology and specific surface for assessment of the opportunity to apply these materials as an active substance of pasted “−” electrode of the supercapacitor.
To achieve this aim following goals has been solved:
1) to investigate the physical and physical-chemical properties of different carbon nanomaterials;
2) to investigate the physical and physical-chemical properties of different carbon nanomaterials; 3) to carry out the comparative investigation according to materials’ morphology and specific surface.
In this investigation following carbon nanomaterials have been used:
1) CNF 55BR (УНВ 55БР). Consist of fibers with coaxial-cone morphology (cones inserted into one another). Producer − Institute of G.K. Boretsky, SD RAS (Novosibirsk). In generally material consists of filamentous structures, built from graphene plates inserting under a constant angle to fiber axis;
2) CNF 25 MR (УНВ 25МР). Feathery fibers. Producer - Institute of G.K. Boretsky, SD RAS (Novosibirsk). In generally material consists of feathery fibers with different diameters (to 100 nm);
3) MWCNT/CNF (МУНТ/УНВ). Producer – VSU (Vladimir). The product of CVD synthesis, consist of a mixture of multiwalled carbon nanotubes (MWCN) and carbon nanofibers (CNF) (formed by fiber with the hollow inside the channel, similarly CNF 55BR (УНВ 55БР);
4) MWCNT (T – M) (МУНТ (Т-М)). Multiwalled carbon nanotubes “Taunit - M”. Producer – “NanoTechCentre” Ltd (Tambov);
5) SWCNT (ОУНТ) Single of a few-walled carbon nanotube. Producer − «Tuball» (Novosibirsk);
6) Pirocarbon (Пироуглерод);
7) MWCNT (T–M) (МУНТ (Т-МД)). Multiwalled carbon nanotubes, functionalized by ozonated. “Taunit - MD”. Producer – “NanoTechCentre” Ltd (Tambov);
Samples characterization. Morphology has been investigated by SEM and TEM. The composition has been detected by IR, specific surface – by BET methods (nitrogen adsorption-desorption). Electrochemical properties have been investigated by 1) voltammetry; 2) galvanostatic charge-discharge cycling
The results of charge-discharge cycling show no direct correlation between specific surface of carbon nanomaterials and their specific capacities. Specific capacity (per gram of material) is shown in Fig. 1, specific capacity (per cm2 of the material specific surface) – on the Fig. 2. It was concluded, that part of the nanomaterial surface is available for the electrochemical process.
Figure 1 − Specific capacity of carbon nanomaterial samples, F/g
Figure 2 − Specific capacity of carbon nanomaterial samples, F/m2 of specific surface
Maximal specific capacity is characterized the samples SWCNT (ОУНТ) and MWCNT (T–M) (МУНТ (Т-МД)): 128.8 and 122.3 F/g, 0.358 and 0.382 F/m2 correspondently.