DIRECT-FORMATION SELF-ASSEMBLY GRAPHENE FROM CELLULOSE NANOFIBER AQUEOUS SOLUTION
A self-assembled freestanding graphene membrane or graphene layer is formed from industrial graphene having a particle size from approximately 1 to 10 microns and cellulose nanofibers having a nanofiber size from approximately 1 to 9 microns. The self-assembled freestanding graphene membrane or graphene layer has a graphene to cellulose nanofiber mass ratio of approximately 12:1 to 20:1, an electrical conductivity of between approximately 5.8 and 7.2 S/cm, and a thermal conductivity of between 2000 and 3000 W m −1 K −1 . The freestanding graphene membrane or graphene layer is formed from an aqueous dispersion of graphene and cellulose nanofibers in a mass ratio of graphene to cellulose nanofibers of 20:1 to 10:1 deposited on a substrate followed by self-assembly and drying. A dopant of oxygen, nitrogen, sulfur, nickel, gold, silver, zinc, copper, magnesium, and boron may be precisely incorporated into the graphene membrane or layer.
1 . A self-assembled freestanding graphene membrane or graphene layer comprising:
industrial-grade pure graphene having a particle size from approximately 1 to approximately 10 microns; and
cellulose nanofibers having a nanofiber size from approximately 1-9 microns;
the self-assembled freestanding graphene membrane or graphene layer having graphene to cellulose nanofiber mass ratio of approximately 12:1 to 20:1 (graphene:cellulose) and an electrical conductivity of between approximately 5.8 and 7.2 S/cm and a thermal conductivity of between approximately 2000 and 3000 W m −1 K −1 ;
the freestanding graphene membrane or graphene layer formed from an aqueous dispersion of the graphene and the cellulose nanofibers in a mass ratio of graphene to cellulose nanofibers of 20:1 to 10:1 deposited on a substrate followed by self-assembly and drying.
2 . The self-assembled freestanding graphene membrane or graphene layer of claim 1 , further comprising a dopant including one or more of oxygen, nitrogen, sulfur, nickel, gold, silver, zinc, copper, magnesium, and boron.
3 . The self-assembled freestanding graphene membrane or graphene layer of claim 2 , wherein the dopant is added in the form of a doped graphene particle to the aqueous dispersion.
4 . A lithium metal battery anode comprising the self-assembled freestanding graphene membrane or graphene layer of claim 1 with an electroplated layer of lithium having a capacity of 4 mAh cm −2 to 10 mAh cm −2 formed thereon.
5 . A battery including the lithium metal battery anode of claim 4 .
6 . The battery of claim 5 , where the battery is a lithium pouch battery.
7 . A method of forming the self-assembled freestanding graphene-cellulose nanofiber membrane or layer of claim 1 , comprising:
forming an aqueous dispersion of graphene particles having a particle size of approximately 1 micron to approximately 9 microns with cellulose nanofibers having a nanofiber length of approximately 1 to approximately 9 microns at a mixing ratio of graphene particles and the cellulose nanofibers of approximately 20:1 to approximately 10:1;
mixing the aqueous dispersion;
depositing the dispersion on a substrate;
drying the dispersion to form the self-assembled freestanding graphene-cellulose nanofiber membrane or layer.
8 . The method of claim 7 , further comprising adding a dopant including one or more of oxygen, nitrogen, sulfur, nickel, gold, silver, zinc, copper, magnesium, and boron to the aqueous dispersion.
9 . The method of claim 8 , wherein the dopant is added in the form of a doped graphene particle to the aqueous dispersion.
10 . The method of claim 7 , wherein the depositing is by dispersion casting or doctor blade coating.
11 . The method of claim 7 , further comprising rolling following drying.
12 . The method of claim 7 , further comprising low temperature thermal treatment at a temperature of approximately 50-70° C. for a period of approximately 6 hours to 24 hours.
13 . The method of claim 7 , further comprising electroplating a lithium metal layer on the self-assembled freestanding graphene-cellulose nanofiber membrane or layer.