A new oxysulfide spinel, LiAl0.15Mn1.85O3.97S0.03 with well-developed octahedral structure was synthesized by a sol-gel method using glycolic acid as a chelating agent. The electrochemical performance of the oxysulfide was studied compared with those of S-doped spinel, LiMn2O3.98S0.02 and Al-doped spinel LiAl0.24Mn1.76O4. The LiAl0.15Mn1.85O3.97S0.03 electrode shows no capacity loss in the 3 and 4 V region. The origin of no capacity loss of the electrode was investigated by XRD and HRTEM. The substitution of S for O in LiMn2O4 stabilized the structural integrity of the spinel host, which in turn increased electrochemical cyclability.