The lithium intercalation effects on the electronic states and the chemical bonding of spinel Li x Mn2O4 (x=0,1,2) have been investigated by the DV-Xα molecular orbital method. It is found that charge transfer takes place mostly from the Li ions to the O ions, but not to the Mn ions, when Li is intercalated into either the tetrahedral site or the octahedral site surrounded by the O ions in the compounds. Also, it is shown that these lithium intercalation compounds are characteristic of the host skeleton frame of Mn and O ions, which can flexibly accommodate the intercalated Li ions while maintaining the original electronic states as much as possible through the suitable structure relaxation.