The lithium-ion battery has been extensively used as one of the most powerful energy storage devices, and its market is increasing by 10% annually. Among promising candidates for the high-performance cathode of the lithium-ion battery, disordered rock-salt structured cathode materials have attracted great attention due to their extended capacities and cost effectiveness over traditional cathode materials with the layered structure through the design of more accessible lithium-ion sites and low-cost transition metals. However, they have not yet been utilized owing to their low electronic/ionic conductivities and poor cycle life. To overcome the major hurdle for improving the electrochemical performance of the disordered rock-salt materials, we synthesize cation- and anion-doped disordered Li3NbO4 with rock-salt structures, Li1.3Nb0.43Ni0.27O2 and Li1.3Nb0.43Ni0.27O1.97F0.05, respectively, and decreased their particle sizes to reduce the Li-ion transport path. Enhanced electrochemical performances of the doped-disordered-rock-salt materials and their underlying mechanism have been addressed by cross-confirmation using various analysis techniques.