Layered Li-Mn-oxide with the O2 structure: A cathode material for Li-ion cells which does not convert to spinel

Layered sodium manganese bronzes having the P2 structure (Nau(2/3)[Li1/6Mn5 /6]O-2), were used to prepare layered lithium manganese oxides by ion excha nge of Na by Li using LiBr in hexanol. X-ray diffraction and chemical analy sis show that layered Li-2/3[Li1/6Mn5/6]O-2 has an O2 type structure. The a rrangement of manganese and oxygen atoms in this phase differs fundamentall y from that found in layered LiMnO2 (O3 structure), in orthorhombic LiMnO2, and in spinel Li2Mn2O4 so that conversion to spinel during electrochemical cycling is not expected. Li-2/3[Li1/6Mn5/6]O-2 as well as the related Li-2 /3[Li1/18Mn17/18]O-2 and Li-2/3[Mn0.85Co0.15]O-2 have a reversible charge c apacity of about 150 mAh/g. During cycling the new cathode materials do not convert to spinel, in contrast to the behavior of layered and orthorhombic LiMnO2. (C) 1999 The Electrochemical Society. S0013-4651(99)02-012-1. All rights reserved.