The effect of cross-link density of phenolic resin precursor on the capacity of as-prepared carbon was investigated. The results show that a higher cross-link density of phenolic resin is beneficial to the charge capacity of the carbon, and the charge capacity of carbon prepared from phenolic resin with the highest cross-link density is greater than the theoretical capacity of carbonaceous materials. Moreover, the charge curves exhibit a potential plateau at approximately 1 V vs. Li/Li+, and the increase of charge capacity results mainly from the lengthening of this plateau. To explain this phenomenon, we proposed a mechanism that, except for the lithium intercalated between graphene layers, lithium is doped mainly at the edges of graphene layers rather than the surfaces of graphene layers, and it is the interaction between lithium and atoms at the edges that leads to the plateau at about 1 V.