Hollandite-type (K0.01Li0.42)MnO2.08 and its Co-doped (K0.04Li0.34) (Mn-0.85 Co-0.15)O-2.07 have been synthesized by Li+ ion-exchange of alpha- K0.14Mn1-xCoxO2 center dot zH(2)O (x=0-0.15, z=0.15-0.21) in a LiNO3/LiCl molten salt at 300 degrees C and characterized by X-ray diffraction (XRD), chemical analysis, N-2-sorptmetric and electrochemical measurements. XRD measurements and chemical analysis indicated that almost all the K+ ions and hydrogens of the structural waters in the [2 x 2] tunnels of the precursor alpha-MnO2 were exchanged by Li+ ions in the molten salt, resulting in Li+-type alpha-MnO2 and its Co-doped one including Li+ ions as well as Li2O in the [2 x 2] tunnels. N-2-sorptmetric measurements revealed that the Li+ ion-exchanged products have a mesopore structure as well as a micropore one, in the range of 1-10 nm, and the BET surface area of the precursor alpha-K0.14Mn1-xCoxO2 decreased with Li+ ion-exchanging, probably due to the incorporation of Li2O molecules in the [2 x2] tunnels. The chemical diffusion coefficients of lithium for the Li+ ion-exchanged products increased by about one-order of magnitude with Li+ ion-exchanging. The Li+ ion-exchanged products provided higher initial discharge capacities and better recharge efficiencies than the parent materials, probably due to the structural stability with the existence of Li2O in the [2 x 2] tunnels. (c) 2008 Elsevier B.V. All rights reserved.