Different amounts of LiCoO2 from waste lithium-ion batteries were dissolved in nitrite acid and the recovered Li and Co were used to modify Na0.67Fe0.5Mn0.5O2 cathode by a sol-gel method. Based on the results by X-ray diffraction, Li+/Co3+ ions were doped into Na0.67Fe0.5Mn0.5O2, with the smaller lattice parameters. The results by X-ray photoelectron spectroscopy show that the doping of Li/Co ions leads to the conversion of Mn3+ ions to Mn4+ ions, resulting in the less Jahn teller effect. The results by electrochemical tests indicate that the cycle stability and rate performance of the modified Na0.67Fe0.5Mn0.5O2 improve due to LiCoO2 modification. The sample with x of 0.105 (i.e., Na0.53Li0.105Co0.105(Fe0.5Mn0.5)0.79O2) possesses a capacity retention of 67% after 150 cycles at a current density of 1 C, and a specific capacity is 30 mA·h/g at 5 C.