LiMn2O4, Li1.05Mn1.95O4, and Li1.05Mn1.95O3.95Cl0.05 are prepared by a solution-based process to investigate the influences of codoping of Li and Cl on the electrochemical performance and structural stability of Li1+x Mn2‑x O4‑y Cl y (x, y = 0, 0.05). Li1.05Mn1.95O3.95Cl0.05 features an improved cycling performance and rate capability compared with LiMn2O4 and Li1.05Mn1.95O4, which originate from the improved structural stability and the reduction in Mn dissolution into electrolyte by the codoping of Li and Cl. The improvement in the cycling performance of Li1.05Mn1.95O3.95Cl0.05 is more appreciable at a higher temperature. Further, the electrode resistance of Li1.05Mn1.95O3.95Cl0.05 is much lower than that of LiMn2O4 over the first charge, suggesting that LiMn2O4 with high electrode resistance is structurally unstable during cycling. Both the suppressed Mn dissolution and the reduced electrode resistance of Li1.05Mn1.95O3.95Cl0.05 are attributed to the reinforcement of MnO6 octahedral in Li1.05Mn1.95O3.95Cl0.05 framework by the strong ionic Mn–Cl bonds formed by the codoping of Li and Cl.