The spinel LiMn2O4 cathode material has been considered as one of the most potential cathode active materials for rechargeable lithium ion batteries. The sodium-doped LiMn2O4 is synthesized by solid-state reaction. The X-ray diffraction analysis reveals that the Li1−x Na x Mn2O4 (0 ≤ x ≤ 0.01) exhibits a single phase with cubic spinel structure. The particles of the doped samples exhibit better crystallinity and uniform distribution. The diffusion coefficient of the Li0.99Na0.01Mn2O4 sample is 2.45 × 10−10 cm−2 s−1 and 3.74 × 10−10 cm−2 s−1, which is much higher than that of the undoped spinel LiMn2O4 sample, indicating the Na+-ion doping is favorable to lithium ion migration in the spinel structure. The galvanostatic charge–discharge results show that the Na+-ion doping could improve cycling performance and rate capability, which is mainly due to the higher ion diffusion coefficient and more stable spinel structure.