NITROGEN AND FLUORINE DOPED GRAPHENE AND USE THEREOF

Abstract

A method is disclosed for preparation of nitrogen-doped graphene having these steps: a) providing a dispersion of fluorinated graphite; b) subjecting the dispersion of fluorinated graphite to sonication and/or mechanical treatment and/or thermal treatment; c) contacting the product from step b) with an azide reagent at a temperature within the range of 40 to 200° C.; d) separating the solid product formed in step c) from the mixture; e) dialyzing the product obtained in step d) against water. A nitrogen-doped graphene containing at least 8.9 at. % of nitrogen and up to 16.6 at. % of fluorine is yielded, wherein the at. % are relative to the total atoms present in the sample and determined by X-ray photoelectron spectroscopy (XPS) using an Al-Kα source; and having a density above 1.2 g/cm3 when pressed at 80 kN for 1 min. This nitrogen-doped graphene is particularly useful as a supercapacitor material.

Claims

1. A method for preparation of nitrogen-doped graphene which contains the following steps: a) providing a dispersion of fluorinated graphite; b) subjecting the dispersion of fluorinated graphite to sonication and/or mechanical treatment and/or thermal treatment; c) contacting the product from step b) with an azide reagent at a temperature within the range of 40 to 200° C.; d) separating the solid product formed in step c) from the mixture; e) dialyzing the product obtained in step d) against water.

2. The method according to claim 1, wherein initial content of fluorine in the starting fluorinated graphite is at least 40 at. %, more preferably at least 45 or at least 50 at. %, relative to the total atoms present in the sample and determined by X-ray photoelectron spectroscopy (XPS) using an Al-Kα source.

3. The method according to claim 1, wherein the dispersion prepared in step a) is a dispersion of fluorinated graphite in a polar organic solvent, preferably selected from dimethylformamide, dimethylsulfoxide, A′-methylpyrrolidone. glycols such as ethylene glycol, and mixtures thereof.

4. The method according to claim 1, wherein azide reagent is added in the form of powder to the mixture from step b), or in the form of a suspension in a polar solvent, wherein the polar solvent is preferably selected from dimethylformamide, dimethylsulfoxide, A-methylpyrrolidin. glycols such as ethylene glycol, and mixtures thereof.

5. The method according to claim 1, wherein the azide reagent is selected from metal azides and tri(C1-C4)alkylsilyl azides, preferably the azide reagent is selected from NaN 3, KN 3, LIN3, Pb(N3) 2, trimethylsilyl azide.

6. The method according to claim 1, wherein after contacting the product of step b) containing fluorinated graphite with the azide reagent, the mixture is subjected to heating to a temperature within the range of 70-170° C., even more preferably 100-140° C., wherein the heating is carried out for at least 4 hours, preferably for 4 hours to 20 days, even more preferably for at least 24 hours.

7. Nitrogen-doped graphene containing at least 8.9 at. % of nitrogen and up to 16.6 at. % of fluorine, wherein the at. % are relative to the total atoms present in the sample and determined by X-ray photoelectron spectroscopy (XPS) using an Al-Kα source, and having a density above 1.2 g/cm 3 when pressed at 80 kN for 1 min.

8. Nitrogen-doped graphene according to claim 7, containing at least 13.9 at. % of nitrogen and up to 5 at. % of fluorine, relative to the total atoms present in the sample and determined by X-ray photoelectron spectroscopy (XPS) using an Al-Kα source.

9. Nitrogen-doped graphene according to claim 7, containing at least 16 at. % of nitrogen and up to 5 at. % of fluorine, relative to the total atoms present in the sample and determined by X-ray photoelectron spectroscopy (XPS) using an Al-Kα source.

10. Nitrogen-doped graphene according to claim 8, containing 0.1 to 2 at. % of fluorine, relative to the total atoms present in the sample and determined by X-ray photoelectron spectroscopy (XPS) using an Al-Kα source.

11. Nitrogen-doped graphene according to claim 7, having a density of at least 1.4 g/cm 3 when pressed at 80 kN for 1 min.

12. A supercapacitor having an electrode formed from nitrogen-doped graphene according to claim 7.

13. An electrical cell comprising at least two electrodes, a separator and an electrolyte, characterized in that at least one electrode contains or consists of the nitrogen-doped graphene according to claim 7.

14. The electrical cell according to claim 13, wherein the electrolyte contains an ionic liquid.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0037] FIG. 1. X-ray photoelectron spectra of a) the starting fluorinated graphite and b) the product of Example 1.

[0038] FIG. 2. Combined thermogravimetric analysis and differential scanning calorimetry of the solid product isolated from the reaction of Example 1. The analysis was performed in normal atmosphere, up to 1000° C. at 5° C./min. Exothermic processes are “up” in the graph.

[0039] FIG. 3. Infra-red spectra of (a) the starting fluorinated graphite and (b) the product from Example 1.

[0040] FIG. 4. X-ray photoelectron spectra of the product of Example 2 (after 4 h of reaction in DMF).

[0041] FIG. 5. X-ray photoelectron spectra of the product of Example 3 (after 24 h of reaction in DMF).

[0042] FIG. 6. X-ray photoelectron spectra of a) the product from Example 4 and for comparison b) the product from Example 1.

[0043] FIG. 7. Scanning electron microscopy images of the film of the electrode material (prepared as described in Example 5) pasted on the aluminium foil a-c) before pressing and d-f) after pressing in between two metal plates with force 80 kN for 1 minute.

[0044] FIG. 8. Electrochemical characterization of the product from Example 1. a-b) cyclic voltammetry curves in EMIM-BF.sub.4 and TTE (9:1) electrolyte, at lower (panel a) and higher (panel b) scan rates; c) galvanostatic charge-discharge profiles at different current densities.

[0045] FIG. 9. Cyclic stability of the material produced from Example 1, showing the galvanostatic charge-discharge profiles during the beginning, the middle and final part of the testing for 10000 cycles.

[0046] FIG. 10. Galvanostatic charge-discharge profiles at different current densities of the procedure described in Example 6, in EMIM-BF.sub.4 and TTE (9:1) electrolyte.

[0047] FIG. 11. Galvanostatic charge-discharge profiles at different current densities of the procedure described in Example 7, in EMIM-BF.sub.4 and TTE (9:1) electrolyte.

[0048] FIG. 12. Galvanostatic charge-discharge profiles at different current densities of the procedure described in Example 8, in EMIM-BF.sub.4 and TTE (9:1) electrolyte.

EXAMPLES OF CARRYING OUT THE INVENTION

[0049] Materials and Methods:

[0050] Graphite fluoride (>61 wt % F), NaN.sub.3 (BioXtra), 1-Methyl-2-pyrrolidinone anhydrous, 99.5% and N,N-Dimethylformamide (≥98%) were purchased from Sigma-Aldrich. Acetone (pure) and ethanol (absolute) were purchased from Penta, Czech Republic. All chemicals were used without further purification. Ultrapure water was used for preparation of all aqueous solutions. FT-IR spectra were measured on an iS5 FTIR spectrometer (Thermo Nicolet), using the Smart Orbit ATR accessory with ZnSe crystal. A drop of a dispersion of the sample in ethanol or water was placed on a ZnSe crystal and left to dry and form a film in ambient environment. Spectral were recorded by summing 50 scans, with nitrogen gas was flowing through the ATR accessory during the measurement and also for the background acquisition. ATR and baseline correction were used for processing the collected spectra.

[0051] X-ray photoelectron spectroscopy (XPS) was performed on a PHI VersaProbe II (Physical Electronics) spectrometer, using an Al-Kα source (15 kV, 50 W). MultiPak (Ulvac-PHI, Inc.) software package was used for deconvolution of obtained data.

[0052] Images from transmission electron microscopy were obtained with a JEOL 2100 TEM, equipped with an emission gun of LaB.sub.6 type, operating at 160 kV. The samples were also analyzed with scanning electron microscopy using Hitachi SU6600 instrument with accelerating voltage of 5 kV. For these analyses, a small droplet of a material dispersion in ultrapure water (concentration approximately 0.1 mg/ml) was placed on a carbon-coated copper grid and left for drying.

[0053] Thermal analysis was performed with an STA449 C Jupiter Netzsch instrument.

[0054] Surface area analysis was carried out by N.sub.2 adsorption/desorption measurements at 77 K, using a volumetric gas adsorption analyser (3Flex, Micromeritics) up to 0.965 P/P.sub.0. Prior the analysis, the samples were degassed under high vacuum (10.sup.−4 Pa) at 130° C. for 12 hours, while high purity (99.999%) N.sub.2, and He gases were used for the measurements. The Brunauer-Emmett-Teller area (BET) was calculated with respect to Rouquerol criteria for N.sub.2 isotherm and assuming a molecular cross-sectional area of 16.2 Å.sup.2 for N.sub.2 (77 K).

[0055] A hydraulic press (Trystom spol. s.r.o., Olomouc) was used for pressing the films of the samples in between metallic plates.

[0056] Cyclic voltammetry (CV) and Galvanostatic Charge-Discharge (GCD) were performed on a Bio-Logic battery tester (BCS-810) controlled with the BT-Lab software (version 1.64).

[0057] The following passage defines the supercapacitor metrics which are used in the present document, and generally accepted in the field. Gravimetric specific capacitance (C.sub.s in F/g) and volumetric specific capacitance (C.sub.v in F/cm.sup.3) of the electrode material are calculated from galvanostatic charge-discharge curves according to the equations:

[00001]$C_s=2\times \frac{I.Math.t}{m.Math.V}\left[F/g\right];C_v=C_s\times \frac{m}{V_{el}}\mathrm{or}{C}_s\times d\left[F/{\mathrm{cm}}^3\right]$

[0058] Gravimetric energy density (E.sub.g), gravimetric power density (P.sub.g), volumetric energy density (E.sub.v) and volumetric power density (P.sub.v) are calculated according to the equations:

[00002]$E_g=\frac{1}{8}\times \frac{C_s.Math.V^2}{3.6}\left[\mathrm{Wh}/\mathrm{kg}\right];P_g=\frac{E_g}{t}\times 3600\left[W/\mathrm{kg}\right];E_v=\frac{1}{8}\times \frac{C_v.Math.V^2}{3.6}\left[\mathrm{Wh}/L\right];P_v=\frac{E_v}{t}\times 3600\left[W/L\right]$

wherein m (g) is the mass of active material in one electrode (including the mass of the binder and conductive additives), I (A) is the discharge current, t (s) is the discharge time, and V (V) is the potential change during discharge, V.sub.e1 (cm.sup.3) is the volume of electrode material on one electrode.

Example 1: Synthesis of Nitrogen-Doped Graphene 72 h Reaction

[0059] In a glass spherical flask, 1 g of graphite fluoride was dispersed in 40 ml of DMF. The flask was covered and left stirring for 2 days. Then, it was sonicated for 4 hours and left stirring overnight. In a glass beaker, 2 g of NaN.sub.3 was dissolved in 20 ml of DMF and then added to the graphite fluoride and/or few-layer fluorographene dispersion. The mixture was heated at 130° C. for 72 h in the hood with a condenser under stirring with teflon coated magnetic bar. After the end of heating, the reaction mixture was left to cool down and transferred to 50 ml falcon centrifuge tubes. The solid particles (the product) were separated from the solvent and by-products by centrifugation at 15000 rcf for ca. 10 mins. The supernatant was discarded, and the tube was refilled with the next washing solvent. The sample was homogenized by shaking for at least 1 minute to redisperse the precipitate in the new solvent. Washing was performed with different solvents: DMF (3×), acetone (3×), ethanol (3×), hot ethanol (1×), distilled water (3×) and hot distilled water (1×), then refilled back with distilled water. At the end, the dispersed solid was inserted in a dialysis bag (molecular weight cut-off 10 kDa) until the conductivity of the surrounding water stopped increasing above ca. 10 μS/cm and the conductivity inside the dialysis bag was ca. 5 μS/cm. The dispersion was finally removed from the dialysis bag and was stored for further use or dried.

[0060] X-ray photoelectron spectroscopy on the starting graphite fluoride and the product of Example 1 (FIG. 1) showed that the reaction with NaN.sub.3 resulted in the introduction of N atoms in the product, reaching 16.1 at. % after 72 h of reaction, and in significant loss of fluorine atoms from 50.5 at. % to 1.5 at. % (Table 1).

[0061] Thermogravimetric analysis under normal atmosphere showed a slow mass loss of the material up to ca. 450° C. and a rapid decomposition step between ca. 500° C. and 680° C. (FIG. 2).

[0062] The density of the material measured after depositing 4 mg of the material on an aluminum foil and pressing for 1 min at 80 kN was 2.7 g/cm.sup.3. A part of the same batch of this product was not dialyzed and when pressed under identical conditions, the density was ca. 1.5 g/cm.sup.3.

[0063] The FT-IR spectrum of the starting graphite fluoride (FIG. 3a) showed the bands from the C—F and CF.sub.2 bonds (1200 and 1310 cm.sup.3, respectively). On the contrary, the spectrum of the product (FIG. 3b) is dominated by the bands at 1560 and 1110-1180 cm.sup.3. These vibrations are typical for aromatic carbon and heterocyclic aromatic rings. Additional vibrational modes of the aromatic rings appearing at 1400 cm.sup.−1 can be ascribed to heteroatom substitution (such as in pyridinic configurations). The 1110-1180 cm.sup.−1 bands in the product overlap with the CF.sub.x vibrations in the staring fluorinated graphite, but as XPS confirmed, almost all F atoms (ca. 1.5 at. % residue) have been eliminated. These bands correspond to different modes of aromatic carbon and heterocycle ring stretching vibrations, in analogy with the 1560 and 1400 cm.sup.3 vibrations. The broad absorption above 3000 cm.sup.3 can be ascribed to stretching vibrations of N—H of primary or secondary amino groups (R.sub.2N—H, R—NH.sub.2), covalently attached perpendicularly to the graphene skeleton. In the same area —OH vibrations can also appear. The broad vibration at 1560 cm.sup.−1 could also contain signal from bending vibrations of primary amino groups.

[0064] The specific surface area was 59 m.sup.2/g, according to BET method, at N.sub.2 sorption equilibration time of 20 s.

TABLE-US-00001 TABLE 1 Atomic contents as obtained from X-ray photoelectron spectroscopy analysis for the starting graphite fluoride and for the product of Example 1 (72 h product). Atomic contents % C N O F Graphite fluoride 48.4 0 1.1 50.5 nitrogen-doped graphene, 72 h 79.1 16.1 3.3 1.5

Example 2: Synthesis of Nitrogen-Doped Graphene 4 h Reaction

[0065] The same procedure as in Example 1 was followed, but instead of heating the mixture at 130° C. for 72 h it was heated for 4 h.

[0066] The density of the material measured after dialysis and after depositing 4 mg of the material on an aluminum foil and pressing for 1 min at 80 kN was 1.4 g/cm.sup.3.

[0067] X-ray photoelectron spectroscopy on the product of this example (FIG. 4) showed that the reaction with NaN.sub.3 resulted in the introduction of N atoms in the product, reaching 8.9 at. % after 4 h of reaction, and in significant loss of fluorine atoms from 50.5 at. % of the starting fluorinated graphite down to 16.6 at. % (Table 2).

[0068] The specific surface area was 146 m.sup.2/g.

TABLE-US-00002 TABLE 2 Atomic contents as obtained from X-ray photoelectron spectroscopy analysis for the product of Example 2 (4 h product). atomic contents % C N O F nitrogen-doped graphene, 4 h 72.6 8.9 1.9 16.6

Example 3: Synthesis of Nitrogen-Doped Graphene 24 h Reaction

[0069] The same procedure as in Example 1 was followed but instead of heating the mixture at 130° C. for 72 h it was heated for 24 h.

[0070] The density of the material measured after dialysis and after depositing 4 mg of the material on an aluminum foil and pressing for 1 min at 80 kN was 1.4 g/cm.sup.3.

[0071] X-ray photoelectron spectroscopy on the product of this example (FIG. 5) showed that the reaction with NaN.sub.3 resulted in the introduction of N atoms in the product, reaching 13.9 at. % after 24 h of reaction, and in significant loss of fluorine atoms from 50.5 at. % of the starting fluorinated graphite down to 1.6 at. % (Table 3).

[0072] The specific surface area was 127 m.sup.2/g.

TABLE-US-00003 TABLE 3 Atomic contents as obtained from X-ray photoelectron spectroscopy analysis for the product of Example 3 (24 h product). atomic contents % C N O F nitrogen-doped graphene, 24 h 82.3 13.9 2.2 1.6

Example 4: Preparation of Nitrogen-Doped Graphene without Using Sonication, Centrifugation or Dialysis for Washing Comparative Example

[0073] In a glass spherical flask, 0.25 g of graphite fluoride was dispersed in 10 ml of DMF. The flask was covered and left stirring for 3 days. Then 0.5 g of NaN.sub.3 was added to the flask, and the sonication step described in the Example 1 was omitted. The mixture was heated at 130° C. for 72 hours in the hood with a condenser under stirring with teflon coated magnetic bar. After the end of heating, the reaction mixture was left to cool down and filtered on Si sintered glass with filter paper. Washing was performed on frita with DMF (3×) and distilled water (3×) and hot distilled water (1×). The conductivity of the filtrate was measured to check the purity of the product. If the conductivity was more than 100 μS/cm, then more washing steps with water were performed. The solid was finally redispersed in distilled water, and characterization was performed (conductivity, zeta potential, pH, concentration, infra-red and X-ray photoelectron Spectroscopy) and stored for further use. The dialysis step described in Example 1 was omitted.

[0074] The density of the material measured after depositing 4 mg of the material on an aluminum foil, and pressing for 1 min at 80 kN was 0.7 g/cm.sup.3.

[0075] X-ray photoelectron spectroscopy on the product of this example (FIG. 6) showed that the reaction with NaN.sub.3 resulted in the introduction of N atoms in the product, reaching 15 at. % after 72 h of reaction, and in significant loss of fluorine atoms from 50.5 at. % of the starting fluorinated graphite down to 4.6 at. % (Table 4).

TABLE-US-00004 TABLE 4 Atomic contents as obtained from X-ray photoelectron spectroscopy analysis for the product of Example 4 (no dialysis). atomic contents % C N O F nitrogen-doped graphene, no-dialysis 77.2 15 3.2 4.6

Example 5: Electrochemical Testing in a Two Electrode Symmetric Supercapacitor Full-Cell Using the Product from Example 1 72 h Product

[0076] The active material (nitrogen-doped graphene from Example 1) was homogeneously dispersed in N-methyl-2-pyrrolidone (p.a.≥99%, Sigma-Aldrich) with binder PTFE (Sigma-Aldrich) and conductive carbon (TimCal from MTI) at a ratio of 85:10:5 and sonicated for 4 hours to form homogenous paste. The slurry was pasted on a carbon-coated aluminium foil (Cambridge Energy Solutions, thickness 15 μm) with dr.'s blade technique (Erichsen, Quadruple Film Applicator, Model 360). The obtained film, containing flakes of the nitrogen-doped graphene, was examined with scanning electron microscopy (FIG. 7a-c) showing a thickness of 10-12 μm, with flakes oriented in random manner (FIG. 7b). Next, the film was dried at 120° C. in vacuum oven overnight, before two electrodes with diameter of 18 mm were cut and pressed in between two metal plates with force 80 kN for 1 minute (Trystom spol. s.r.o., Olomouc). After pressing, the film thickness reduced to 1.7 to 1.8 μm, whereby the lamellar structure was evident, and with high degree of orientation (FIG. 7d-f) in parallel to the aluminium foil. The two electrodes with diameter of 1.8 cm (loaded electrode material 1.4 and 1.3 mg respectively) were dried again at 120° C. under vacuum (40 mbar) for 6 hours and transferred (under vacuum) to glovebox (O.sub.2 and H.sub.2O content<2 ppm, under argon atmosphere). According to these values, the density of the produced film was 2.7 g/cm.sup.3. For assembly of the supercapacitor device, the two electrodes were placed in a sleeve (E1-Cell insulator sleeves equipped with Whatman® glass microfiber paper separator with thickness 0.26 mm). The separator membrane was soaked with 90-100 μl of electrolyte. A mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF.sub.4, from Sigma Aldrich,≥99.0 %(HPLC)) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE from Tokyo Chemical Industry, >95.0%) in ratio 90:10 was used as electrolyte, which were dried prior use with molecular sieves. The electrodes were enclosed inside the sleeve with stainless steel plungers, and whole device was tightened and connected to the battery tester for analysis.

[0077] Before testing the device, conditioning of the electrode materials was performed as follows:

[0078] Hold of potential for 5 minutes at 1.2 V, 20 cycles at current density 0.5 A/g up to 2 V, 20 cycles at current density 1 A/g up to 3.7 V.

[0079] Cyclic voltammetry (FIG. 8a,b) showed quasi-rectangular curves, with minor redox peaks, evident mainly at lower scan rates, which can be probably attributed to the nitrogen atoms. The galvanostatic charge/discharge (FIG. 8c) measurements showed practically linear and symmetric profiles (124 s charging, 118 s discharging at 1 A/g, 95% energy efficiency), which improved to 100% efficiency at 5 A/g (22 s charging, 22 s discharging) (Table 5). The performance of the device is described in Table 5 showing an unprecedented volumetric energy density of 169.8 Wh/L at a power density of 5.2 kW/L. The capacitance retention was 94% after 10000 cycles. The stability of the cell was also very high, keeping 100% of its capacitance after 10000 cycles (FIG. 9).

TABLE-US-00005 TABLE 5 Performance characteristics of the supercapacitor full-cells built from the product of Example 1 showing the current density, discharge time (t), gravimetric capacitance (C.sub.g), gravimetric energy and power densities (E.sub.g and P.sub.g respectively) as well as the volumetric capacitance, energy and power densities (C.sub.v, E.sub.v and P.sub.v respectively). Current density t C.sub.g E.sub.g P.sub.g C.sub.v E.sub.v P.sub.v A/g s F/g Wh/kg kW/kg F/cm.sup.3 Wh/L kW/L 2 118 127.6 60.6 1.8 357.3 169.8 5.2 10 22 124 56.5 8.4 347.2 144.9 23.7 20 10 117.6 51.4 15.6 329.3 121.5 43.7

Example 6: Electrochemical Testing in a Two Electrode Symmetric Supercapacitor Full-Cell Using the Product from Example 4 Comparative Example, No Dialysis

[0080] The experiment of Example 5 was repeated, using the product obtained from Example 4 (no sonication, no dialysis). The density of the films produced was 0.7 g/cm.sup.3. The galvanostatic charge/discharge measurements showed very good performance stability with increasing current density (from 2 A/g to 20 A/g) (FIG. 10 and Table 6). The gravimetric energy density was only slightly lower than in the case of the product from Example 1, but the volumetric energy density significantly dropped from 169.8 Wh/L to 35.4 at a power density of 1.3 kW/L for 2 A/g current density. The drop in the volumetric energy density is caused by the much lower packing density, due to low density caused in particular by omission of the dialysis step in preparation of the doped graphene.

TABLE-US-00006 TABLE 6 Performance characteristics of the supercapacitor full-cell built from the product of Example 4 showing the current density, discharge time (t), gravimetric capacitance (C.sub.g), gravimetric energy and power densities (E.sub.g and P.sub.g respectively) as well as the volumetric capacitance, energy and power densities (C.sub.v, E.sub.v and P.sub.v respectively). Current density t C.sub.g E.sub.g P.sub.g C.sub.v E.sub.v P.sub.v A/g s F/g Wh/kg kW/kg F/cm.sup.3 Wh/L kW/L 2 97.3 105.2 50 1.9 73.6 35.4 1.3 10 20 108 51.3 9.3 75.6 36.3 6.5 20 10.4 108 51.3 18.5 75.6 36.3 13.1

Example 7: Electrochemical Testing in a Two Electrode Symmetric Supercapacitor Full-Cell Using the Product from Example 2 4 h Product

[0081] The experiment of Example 5 was repeated, using the product obtained from Example 2 (4 h reaction). The density of the films produced was 1.4 g/cm.sup.3. The galvanostatic charge/discharge measurements showed low performance (FIG. 11 and Table 7). Both the gravimetric and volumetric data were significantly lower than Example 1.

TABLE-US-00007 TABLE 7 Performance characteristics of the supercapacitor full-cell built from the product of Example 2 showing the current density, discharge time (t), gravimetric capacitance (C.sub.g), gravimetric energy and power densities (E.sub.g and P.sub.g respectively) as well as the volumetric capacitance, energy and power densities (C.sub.v, E.sub.v and P.sub.v respectively). Current density t C.sub.g E.sub.g P.sub.g C.sub.v E.sub.v P.sub.v A/g s F/g Wh/kg kW/kg F/cm.sup.3 Wh/L kW/L 2 43 46.4 22 1.8 64.9 32.3 2.7 10 3.3 3.5 1.6 0.5 4.9 2.4 0.7

Example 8: Electrochemical Testing in a Two Electrode Symmetric Supercapacitor Full-Cell Using the Product from Example 3 24 h Product

[0082] The experiment of Example 5 was repeated, using the product obtained from Example 3 (24 h reaction). The density of the films produced was 1.4 g/cm.sup.3. The galvanostatic charge/discharge measurements showed performance close to Example 1 (72 h product) (FIG. 12 and Table 8). The significantly lower density though, resulted in significantly lower volumetric energy density than the 72 h product of Example 1 as measured in Example 5.

TABLE-US-00008 TABLE 8 Performance characteristics of the supercapacitor full-cell built from the product of Example 3 showing the current density, discharge time (t), gravimetric capacitance (C.sub.g), gravimetric energy and power densities (E.sub.g and P.sub.g respectively) as well as the volumetric capacitance, energy and power densities (C.sub.v, E.sub.v and P.sub.v respectively). Current density t C.sub.g E.sub.g P.sub.g C.sub.v E.sub.v P.sub.v A/g s F/g Wh/kg kW/kg F/cm.sup.3 Wh/L kW/L 2 108.6 117 54.3 1.8 152.0 81.4 2.7