Recently, magnesium-ion batteries (MIBs) have been under remarkable research focus owing to their appealingly high energy density and natural abundance of magnesium. Nevertheless, MIBs exhibit a very limited performance because of sluggish solid-state Mg2+ ion diffusion and high polarizability, which hinder their progress toward commercialization. Herein, we report a Mg2+/Li+ hybrid-ion battery (MLIB) with NaV3O8·1.69H2O (NVO) nanobelts synthesized at room temperature working as the positive electrode. In the hybrid-ion system, Li+ intercalates/deintercalates along with a small amount of Mg2+ adsorption at the NVO cathode, whereas the anode side of the cell is dominated by Mg2+ deposition/dissolution. As a result, the MLIB exhibits a much higher rate capability (i.e., 446 mA h g-1 at 20 mA g-1) than the previously reported MLIBs. MLIB maintains a high specific capacity of 200 mA h g-1 at 80 mA g-1 for 150 cycles, showing excellent stability. Moreover, the effect of different Li-ion concentrations (i.e., 0.5-2.0 M) in the electrolyte and cutoff voltage (ranging from 2 to 2.6 V) on the specific capacities are investigated. The current study highlights a strategy to exploit the Mg2+/Li+ hybrid electrolyte system with various electrode materials for high-performance MIBs.