Carbons play a critical role in all battery electrodes. In choosing a carbon, one must first define the role of the carbon: conductivity, electrolyte absorption, coating aid, process aid such as lubricity and rheology, powder flow, contributor to the electrode pore structure, oxygen reduction, cathoylte reaction sites, etc. For hard carbons, consider such physical properties as: aggregate and particle size, surface area, functional surface groups as defined by Boehm titration, structure, micro, meso, and macro pores, pH, absorptivity of liquids, conductivity, and contribution to electrode integrity. When considering graphitic carbons, the transition from single layer graphene to multi-layer graphenes to graphite to surface groups to graphene oxide is an important consideration. Of course, the discussion becomes more detailed when the carbon plays a role in the electrochemical reaction, such as in a lithium ion anode involving interaction, or when it serves as a catalytic site, such as for oxygen reduction or as a reaction site for sulfur reduction such as in lithium sulfur batteries.