The Li+ ion-exchange reaction of K+-type alpha-K0.14MnO1.93 center dot 0-18H(2)O and its Co-doped alpha-K-0.14(Mn0.85Co0.15)O-1.96 center dot 0.21H(2)O with a large (2 x 2) tunnel structure has been investigated in a LiNO3/LiCI molten salt at 300 degrees C. The Li+ ion-exchanged products were examined by chemical analysis, X-ray diffraction, and scanning and transmission electron microscopic measurements. Almost all the K+ ions and the hydrogens of water molecules in the (2 x 2) tunnel of alpha-MnO2 and its Co-doped one were exchanged by Li+ ions in the molten salt, resulting in Li+-type alpha-MnO2 and its Co-doped one containing Li+ ions as well as Li2O (lithium oxide) in the (2 x 2) tunnel with maintaining the original hollandite structure. The electrochemical properties including charge-discharge cycling of the Li+ ion-exchanged alpha-MnO2 and its Co-doped samples have been investigated as insertion compounds in the search for new cathode materials for rechargeable lithium batteries. The Li+ ion-exchanged alpha-MnO2 and its Co-doped samples provided higher capacities than the K-type parent materials on initial discharge and charge-discharge cyclings, probably due to the structural stabilization with the existence of Li2O in the (2 x 2) tunnels. (c) 2007 Elsevier B.V. All rights reserved.