Li2MTi6O14 (M=Sr, Ba):: new anodes for lithium-ion batteries

Isostructural Li2MTi6O14 (M = Sr, Ba) materials, prepared by a solid state reaction method, have been investigated as insertion electrodes for lithium battery applications. These titanate compounds have a structure that consists of a three-dimensional network of corner- and edge-shared [TiO6] octahedra, 11-coordinate polyhedra for the alkali-earth ions, and [LiO4] tetrahedra in tunnels that also contain vacant tetrahedral and octahedral sites. Electrochemical data show that these compounds are capable of reversibly intercalating four lithium atoms in a three-stage process between 1.4 and 0.5 V vs. metallic lithium. The electrodes provide a practical capacity of approximately 140 mAh/g; they are, therefore, possible alternative anode materials to the lithium titanate spinet, Li4Ti5O12. The lithium intercalation mechanism and crystal structure of Li2MTi6O14 (M = Sr, Ba) electrodes are discussed and compared with the electrochemical and structural properties of Li4Ti5O12. The area-specific impedance (ASI) of Li/Li2SrTi6O14 cells was found to be significantly lower than that of Li/Li4Ti5O12 cells. (C) 2003 Elsevier Science B.V. All rights reserved.