Ni, Mo co-doped LiMn2O4 cathode materials for lithium-ion batteries were prepared using a high-temperature solid-state method. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM),and electrochemical impedance spectroscopy. The original material’s performance was significantly enhanced by co-doping. The sample with optimal composition, LiNi0.03Mo0.01Mn1.96O4, had a discharge capacity at1C of 114mAhg−1, which was 8.6% higher than that of undoped LiMn2O4. Importantly, this doped material exhibited significantly improved stability: after 300 charge–discharge cycles at 1C, its capacity retention was 91.2%, whereas the capacity retention of the undoped LiMn2O4 was only 61.9% after 300 cycles. SEM images and XRD patterns showed no obvious morphological changes in the co-doped material after cycling, implying that it had high structural stability. We suggest that this material’s significantly improved electrochemical performance was probably caused by reduced Mn3+ dissolution and decreased Li+ intercalation and de-intercalation resistances.