Abstract
Cathode properties of two layered manganese dioxides 
, where A is the pillaring alkali cations) having different crystal structures were compared in 3 V Li secondary batteries. The materials were prepared from the mixture of 
, LiOH, and MnO at 800 and 1050°C, respectively. The 800°C‐prepared 
has a trigonal 
space group with an O3‐type oxide‐packing pattern, whereas the 1050°C material has an orthorhombic Cmcm symmetry with a P2‐type oxide‐packing pattern. The gallery space where the pillaring cations and water molecules reside is wider in the case of the 800°C material. Due to the higher mobility of pillaring cations in the 800°C material and similarity in the oxide‐packing pattern (O3‐type) to the spinel phases, the pillaring cations are easily leached out during cell cycling, which ultimately leads to a lattice collapse and structural transition to the spinel‐related phases. By contrast, as the 1050°C material has rather immobile pillaring cations and its oxide‐packing pattern (P2‐type) is far different from that of the spinel phases, this cathode shows better cycling performance, with its structural integrity being well maintained. © 2000 The Electrochemical Society. All rights reserved.