GRAPHENE / CARBON COMPOSITIONS

Abstract

High surface area nano sized graphene and carbon compositions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart of Galvanostatic charge/discharge for the electrochemical characterization of the material prepared in example 1 with gravimetric capacitance in F/g (faraday/gram) versus current density in A/g (amps/gram).

FIG. 2 is a chart of volumetric capacitance with Current Density in A/g versus Volumetric Capacitance in F/cm³.

FIG. 3 is a chart of gravimetric energy in Wh/kg versus Current Density in A/g.

FIG. 4 is a chart, of Volumetric Energy in mWh/cm³ versus Current Density in A/g.

FIG. 5 is a chart of Gravimetric Power in kW/kg versus Current Density in A/g.

FIG. 6 is a chart of volumetric Power in W/cm³ versus Current density in A/g.

FIG. 7 is a chart of capacitance in F/g versus Current density in A/g.

FIG. 8 is a chart of energy density in Wh/Kg versus Current density in A/g.

DETAILED DESCRIPTION OF THE INVENTION

The instant invention deals with the addition of graphene into activated carbon. The carbon useful herein has an average size of between 10 nanometer and 100 microns and a BET surface area greater than about 300 m²/g. The graphene has a size between 30 nanometers and 50 microns and a BET surface of greater than about 300 m²/g. In addition, the graphene has an aspect ratio between about 25 and 25,000. The graphene to carbon ratio is between 0.5 and 10.

In FIGS. 1 to 6, 1 designates 100% YP50F; 2 designates 90% YP50F and 10% C750; 3 designates 80% YP50F and 20% C750; 4 designates 70% YP50F and 30% C750; 5 designates 60% YP50F and 40% C750; 6 designates 5.0% YP50F and 50% C7S0, weight ratios.

In FIGS. 7 and 8, 1 designates 100% xGnP Xg Sciences graphene; 2 designates 90% activated carbon and 10% xGnP; 3 designates 100% Kansai activated carbon; and 4 designates 100% YP50F activated carbon.

EXAMPLES

Example 1

Commercial activated carbon (ACTIVATED CARBON:YP-50F, 1500 m²/g, Kurary Chemical Company) and nanosized graphene: C-750, 750 m²/g, XG Sciences, Lansing, Mich.) were used as the active materials in this example. Carbon black (Super C, Timcal) and PVDF were used as conductive agents and polymeric binder, respectively. The paste consisting of typical weight ratio of active carbon:nano sized graphene:Super-C:PVDF=88:7:5 was coated on aluminum foil via a doctor blade method. Galvanostatic charge/discharge for electrochemical characterization was performed in 1M TEABF₄/acetonitrile electrolyte in the range of 0-2.5V.

While no synergic effect for the hydbridization of nano sized graphene with activated carbon was shown at low current density (<A/g), the capacitance of nano sized graphene/activated carbon electrode was increased over activated carbon alone electrode at high current density (>1A/g). The addition of 30% to 40% of nano sized graphene seems optimal to achieve the best synergic effect. See FIGS. 1 and 2.

Energy density was compared. The behavior of gravimetric energy density as a function of current density was similar to that of capacitance. However, the volumetric energy density of nano sized graphene/activated carbon electrode was higher than that of activated carbon electrode regardless of current density.

Power density was compared. Both gravimetric and volumetric powder density were increased for the nano sized graphene/activated carbon electrodes regardless of current density and nano sized graphene content due to excellent conductivity of the nano sized graphene. See also FIGS. 3 and 4.

Example 2.

Two commercial activated carbons were used as active component: YP-50F (1500 m²/g, Kuraray Chemical Company and MSP-20 (2200 m²/g, Kansai Chemical Company. Nanosized graphene (C-750, 750 m²/g, and multi-walled carbon nanotubes (230 m²/g, Hanwha Nanotech) were used as another active material and the binder, respectively. Activated carbon or the activated carbon/nano sized graphene was dispersed in isopropyl alcohol using a bath type sonicator for 60 minutes and carbon nano tubes was also separately sonicated in Isopropyl alcohol for 1 hour. The dispersed activated, carbon and the carbon nano tubes solutions were combined, followed by additional 60 minutes sonication. Then, the activated, carbon-carbon nano tubes and activated carbon/nano sized graphene-carbon nanotubes dispersion (ink) was filtered using a membrane filtration system. After drying at 80°C. under vacuum for 2 hours, the activated carbon-carbon nano tubes and activated carbon/nano sized graphene-carbon nano tube free standing paper were calendared on Ni foam. Electrochemical tests for 2016 coin cell with two identical activated carbon-carbon nano tube electrodes was done in 1M TEABF₄/acetonitrile electrolyte.

The specific capacitance and energy density of activated carbon/nano sized graphene-carbon nano tube electrode shows higher than that of activated carbon-carbon nano tube electrodes, which confirms the synergistic effect of the hybridization of activated carbon-nano sized graphene as co-active materials for electrochemical capacitors. See FIGS. 5 and 6.

Claims

1. A composition of matter comprising a combination of a high surface area nanosized graphite, and carbon wherein the nanosized graphite is selected from, the group consisting of nanosized graphene nanotubes and nanosized graphene nanoplatelets.

2. A composition of matter as claimed in claim 1 wherein the carbon is selected from the group consisting essentially of: a. activated carbon;b. carbon black, and,c. carbon nanofibers, and,d. carbon aerogels.

3. A process of manufacturing a composition as claimed in claim 3, said method comprising: i. dispersing graphene in a suitable solvent;ii. dispersing carbon in a suitable solvent.iii. combine and mix the products of i and ii to form a slurry;iv. filtering said slurry to provide a sheet form;v. drying the sheet formed in iv.;vi. calendaring said sheet to a desired thickness and surface finish.