Different amounts of LiCoO₂ from waste lithium-ion batteries were dissolved in nitrite acid and the recovered Li and Co were used to modify Na_0.67Fe_0.5Mn_0.5O₂ cathode by a sol–gel method. Based on the results by X-ray diffraction, Li⁺/Co³⁺ ions were doped into Na_0.67Fe_0.5Mn_0.5O₂, 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 Na_0.67Fe_0.5Mn_0.5O₂ improve due to LiCoO₂ modification. The sample with x of 0.105 (i.e., Na_0.53Li_0.105Co_0.105(Fe_0.5Mn_0.5)_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.