Li0.44MnO2: an intercalation electrode with a tunnel structure and excellent cyclability

Abstract

Li_0.44MnO₂ possesses a complex tunnel structure composed of sheets of edge-sharing MnO₆ octahedra and columns of edge-sharing MnO₅ square pyramids both lying parallel to the c axis of the orthorhombic unit cell (space group Pbam). The sheets and columns corner share thus defining two types of tunnels. The smaller of these contains one Li⁺ ion site and the larger two pairs of Li⁺ sites. There are no less than five crystallographically distinct Mn sites. The lithium content of the host has been varied by chemical and electrochemical intercalation/deintercalation over the range Li_xMnO₂ ; 0.25<xV vs. Li⁺(1 m)/Li, at 0.5 mA cm^–2 corresponding to a capacity of 85–90 mA h g^–1 .