The spinel Li4Mn5O12 has been considered as a prospective 3 V cathode material for the next generation of lithium-ion batteries (LIBs) due to its high energy density and excellent cycling stability. However, the low operating voltage (similar to 3 V) makes Li4Mn5O12 impractical for high-energy high-power LIBs. To address this issue, Ni and Fe dual doped Li4Mn5-x-yNixFeyO12 has been prepared via a facile sol-gel method combined with post-heat-treatment. The effects of dual-cations doping on the crystal structure, morphology and electrochemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and galvanostatic charge/discharge analysis. As a result, Li4Mn4Ni0.5Fe0.5O12 exhibits the highest reversible specific capacity of 133 mAh/g at a specific current density of 25 mA/g after 100 cycles and exhibits a significantly improved high voltage performance with corresponding capacity of similar to 80 mAh/g at an average voltage of 4.7 V vs. Li/Li+ and similar to 122 mAh/g at above 4.0 V. These results indicate the dual doping of Ni and Fe can effectively improve both the operating voltage and reversible specific capacity of Li4Mn5O12 with excellent cycling stability, demonstrating a promising high-voltage cathode material for high-energy high-power LIBs. (C) 2015 The Electrochemical Society. All rights reserved.