Process for producing graphene foam supercapacitor electrode

A process for producing a supercapacitor electrode, said process comprising:

• (a) preparing a graphene dispersion having multiple sheets of a starting graphene material dispersed in a liquid medium, and wherein said dispersion contains an optional blowing agent having a blowing agent-to-graphene material weight ratio from 0/1.0 to 1.0/1.0;
• (b) dispensing and depositing said graphene dispersion onto a surface of a supporting substrate to form a wet layer of graphene material, wherein said dispensing and depositing procedure includes subjecting said graphene dispersion to an orientation-inducing stress;
• (c) partially or completely removing said liquid medium from the wet layer of graphene material to form a dried layer of graphene material;
• (d) heat treating the dried layer of graphene material at a first heat treatment temperature from 80° C. to 3,200° C. at a desired heating rate sufficient to induce volatile gas molecules from said non-carbon elements or to activate said blowing agent for producing a layer of solid graphene foam, wherein said solid graphene foam is composed of multiple pores and pore walls, and said pore walls contain a pristine graphene material having essentially zero % of non-carbon elements, or a non-pristine graphene material having 0.001% to 5% by weight of non-carbon elements, and wherein said solid graphene foam has a physical density from 0.01 to 1.7 g/cm3, a specific surface area from 50 to 3,300 m2/g, a thermal conductivity of at least 200 W/mK per unit of specific gravity, and/or an electrical conductivity no less than 2,000 S/cm per unit of specific gravity;
• and
• (e) impregnating said multiple pores with a liquid or gel electrolyte to form a layer of pre-impregnated solid graphene foam, which is subjected to a step of compressing or roll-pressing that reduces a pore size, improves orientation of graphene planes, and squeezes excess electrolyte out of said pre-impregnated solid graphene foam for forming said supercapacitor electrode.