LiNixCoyMnzO2 cathode materials are technologically important for high-energy-density Li-ion batteries. However, poor electronic conductivity limits their practical use compared to conventional LiCoO2 cathodes. There are efforts to the use of multiwalled carbon nanotubes (MWCNTs) as a highly conductive agent, but they have poor dispersibility in most polar solvents. Here, we report a rheological behavior of functionalized graphene nanoribbons (GNRs) and their use for a high rate capability of a LiNi0.84Co0.12Mn0.04O2 cathode. The functionalized GNRs are prepared by chemical unzipping MWCNTs, enabling good dispersion in N-methyl-2-pyrrolidone. The improved dispersibility leads to the slurry with fluid-like behavior and an electrode with a uniform conductive network of carbon black/GNRs, improved cohesion strength, and decreased charge transfer resistance. As a result, the electrode shows the highest capacity retention compared to the electrode with only carbon black or carbon black/MWCNTs at a high 4 C-rate.