Graphene-based nanomaterials, which contain two-dimensional graphene sheets that consist of sp2-C atoms arranged in a hexagonal lattice, have exceptional electrical conductivity and mechanical properties, thereby showing promise for use in energy-related devices. Two different types of graphene nanomaterials were studied: one-dimensional graphene nanoribbons and three-dimensional graphene foams. The graphene nanoribbons have both abundant edges for chemical functionalization that improves their dispersibility and interfacial interaction with other materials, and high aspect ratio that affords percolation on a specific area at a smaller mass loading. They have been demonstrated to be an excellent choice for making conductive films with deicing and anti-icing capabilities (Chapter 1) and as a conductive additive for dendrite-free Li metal anodes in Li metal batteries and red P anodes in high energy density Li-ion batteries (Chapter 2). It was found that red P was not only a good candidate for anode materials, but a surprisingly powerful tool to improve battery safety by in situ detection of Li dendrites in an ordinary two-electrode battery system. The other graphene nanomaterial, the three-dimensional graphene foams prepared from polyacrylonitrile using the powder metallurgy method, exhibited high electrical conductivity and high mechanical strength that powdered graphene species cannot achieve, which enabled them to reinforce epoxy resin and enhance the electrical conductivity of the epoxy to an unprecedented level (Chapter 3).