To solve the problem of manganese dissolution, which damages spinel structure of LiMn2O4, Li+ extraction performances with persulfate at different temperatures were investigated by chemical analysis, and then XRD, FTIR, and XPS analyses were used to characterize the corresponding mechanism. Results showed that at high temperatures and after treatment with three kinds of persulfate, lithium ions were nearly extracted thoroughly with almost no manganese dissolution. Na2S2O8 was considered the most suitable for Li+ extraction. The lithium extraction/insertion was repeated several times, and the samples maintained considerably high lithium exchange capacity and fairly little manganese dissolution, indicating high cyclic stability and efficiency of the spinel structure. The extraction mechanism was based on the hydrolysis of persulfate, was accompanied by ion exchange and oxidation-reduction reactions, and involved radicals participating in the reactions. The sulfate radical generated by activated persulfate can effectively decrease manganese dissolution, making it possible for cyclic utilization of LiMn2O4.