Chlorine-substituted spinels, Li1.06Mn2O4-zClz with 0 <= z <= 0.10, were prepared with a citrate gel method to investigate the effects of Cl-doping on the crystal structure and the properties as cathode material for lithium-ion batteries. Exclusive spinel phase were found in the prepared powders. The lattice parameter of spinel increases from 8.227 angstrom for z = 0 to 8.238 angstrom for z = 0.06 and becomes saturated for 0.06 < z < 0.10. It indicates chlorine has been successfully doped into the spinel structure. The sample with z = 0.06 shows better cycling performance than that of others. The initial specific discharge capacity of 123 mAh g(-1) and capacity loss rate of 0.21 mAh g(-1) cycle(-1) was measured for these samples. Variation in the crystal structure during charge/discharge was examined with in situ XRD. Two-phase coexistence was observed at voltage between 4.15 and 4.175 V. (c) 2005 Elsevier B.V. All rights reserved.