Lithium-ion capacitors (LICs) are attracting increasing attention because of their potential to bridge the electrochemical performance gap between batteries and supercapacitors. LICs are still impeded by their inferior energy density, which is mainly due to the low capacity of the cathode. Graphene-based nanomaterials have been recognized as one of the most promising cathodes for LICs due to their unique properties, and exciting progress has been achieved.
Graphene, as a novel two-dimensional (2D) nanocarbon material, has many outstanding characteristics such as high theoretical SSA, astonishing electrical conductivity, tunable porosity and rich surface chemistry 
. It should be noted that graphene has comparable or even superior properties to other nanocarbon-based materials, making it an excellent candidate either as a high-performance active material or as an attractive flexible support to load other materials for applications in LIBs, SCs and hybrid devices 
. In particular, graphene-based nanomaterials have been verified as desired capacitor-type cathodes for LICs 
. According to the theoretical calculation, the specific capacitance of graphene can reach as high as 550 F g−1
based on the fully used SSA, significantly higher than that of commercial AC and other porous carbon materials 
. Moreover, the abundant edges, in-plane defects and large number of exposed surface atoms endow graphene with more electrochemical active sites for ion sorption/desorption 
. Thus, graphene and its composites demonstrate great appeal as capacitor-type electrodes with high capacity in LICs. As demonstrated in Figure 1
, graphene or reduced graphene oxide can be directly used as active materials by rationally regulating the structure and surface chemistry. Simultaneously, they can also serve as excellent substrates or building blocks to form 3D porous composites, leading to improved electrical conductivity and/or SSA of the obtained composites. Exciting achievements of graphene-based cathodes in LICs have been made, strongly demonstrating their potential in enhancing the performance of capacitor-type cathodes 
. Accordingly, some reviews about graphene-based anode materials for LICs have been reported 
Figure 1. Typical graphene-based cathode materials for LICs and their advantages and the remaining challenges.
2. Reduced Graphene Oxide as a Cathode Material
2.1. Reduced Graphene Oxide