The Li-air battery has attracted attention for several decades due to its high theoretical energy density (> 3400 Wh/kg). However, it has not been clearly demonstrated that the actual volumetric and gravimetric energy densities are higher than those of Li-ion batteries. In previous studies, generally quite a large amount of electrolyte was employed in preparing the Li-air cells. Usually the electrolyte was much heavier than the carbon materials in the cathode, which made the practical energy density of Li-air battery lower than that of Li-ion batteries. Therefore, the air cathodes with significantly lower amount of electrolyte need to be developed to achieve high specific energy density in Li-air batteries. In this study, we propose a core-shell structured cathode material with a gel-polymer electrolyte layer covering the carbon nanotubes (CNT). The CNTs were synthesized via a floating catalyst chemical vapor deposition (FCCVD) method. The polymeric layer corresponding to the shell was prepared by a Layer-by-Layer (LbL) coating method utilizing Li-Nafion and PDDA-Cl (poly(diallyldimethylammonium chloride)) together. Several bi-layers of Li-Nafion and PDDA on the CNTs surface were successfully prepared and characterized with XPS, FT-IR, and TGA. The porous structure of the CNTs was found to remain after LbL process, which was confirmed by a nitrogen adsorption/desorption profile and BJH pore size distribution analysis. The porous structure could act as the oxygen channels facilitating the transport of oxygen molecules to react with Li ions on cathode surface. These polymeric bi-layers could provide Li ion pathway after absorbing a small amount of ionic liquid electrolyte, 0.5M LiTFSI EMI-TFSI (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide). Compared with typical cathode where only liquid electrolytes were employed, the total amount of electrolyte in the cathode could be significantly reduced, thus the overall cell energy density could be increased. A Li-air battery with this core-shell structured cathode exhibited a high energy density, ~390 Wh/kg, which was assessed by directly weighing all cell components together including GDL (gas diffusion layer), an interlayer (a separator containing a mixture of LiTFSI, 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR-14) and PDDA-TFSI), lithium anode and LbL-CNTs cathode. The cycle life of an LbL-CNTs based cathode was found to be 31 cycles, which was not an excellent performance, but nearly twice better than that of CNTs cathode without polymer coats. Figure 1