▎ 摘　　要

NOVELTY - Composite with high energy storage capacity for high energy storage devices comprises 65-95% graphene, and 3-33% graphitic carbon nitride coated onto mesoporous carbon. USE - The composite is useful in: high energy storage devices; and electrodes, transistors, strain actuators, ultrasensitive gas sensors, conductive thin films, gas barriers, reinforcing plastics and EDLC (all claimed). ADVANTAGE - The composite: has high energy storage capacity; has surface area of 150-1800 m2/g; provides the EDLC which has a specific capacitance of 50-300 F/g, an energy density of 65-150 Wh/kg and a power density of 200-140 KW/kg (claimed), and faster charging and discharging rate; has a bulk resistivity of 4-2200 Omega /cm and a calendared sheet resistance of 1.6-35 Omega /cm2; provides the EDLCs with higher pore accessibility, specific capacitance, a reasonable operating voltage; is obtained by the process which is economical manner by using raw materials i.e. graphite and urea which are inexpensive and abundant, thus the end product is made at room temperature, is scalable to large scale production, and produces graphene yields non-oxidized pure exfoliated graphene increasing it performance, eliminates use of any hazardous chemicals as it is a purely mechanical process, and is environmentally friendly; and provides the EDLCs which are biodegradable and safe as they do not employ any hazardous chemicals in the final product. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) preparation of composite with high energy storage capacity comprising (i) mechanical exfoliation of graphitic flakes to obtain non-oxidized pristine graphene flakes,(ii) polymeric condensation of N-rich urea precursor with mesoporous carbon in 9:1 ratio in aqueous solution followed by calcination to obtain graphitic carbon nitride coated onto mesoporous carbon, and (iii) sonicating the active material of step (i) and step (ii) followed by evaporation to obtain composite of graphene and graphitic carbon nitride coated onto mesoporous carbon; (2) an electrode formed from the composite comprising microetched current collectors with a first layer of highly conductive graphitic carbon, and a second layer of composite of graphene, graphitic carbon nitride coated onto mesoporous carbon; and (3) a high energy density electric double layer capacitance (EDLC) comprising at least a pair of electrodes each comprising current collectors with a first layer of highly conductive graphitic carbon and a second layer of composite of graphene, graphitic carbon nitride coated onto mesoporous carbon, separator along the length of the electrodes, and electrolyte of deep eutectic solvent comprising a mixture of choline chloride and ethane diol (ethaline), mixture of choline chloride and urea (Reline), mixture of choline chloride and methyl urea or mixture of choline chloride and glycerol with a redox couple.