Heteroatom Chemistry Volume 13, Number 6, 2002 Intermetallic Lithium Compounds with Two- and Three-Dimensional Polyanions— Synthesis, Structure, and Lithium Mobility Rainer P ¨ ottgen, 1 Zhiyun Wu, 1 Rolf-Dieter Hoffmann, 1 Gunter Kotzyba, 3 Henning Trill, 2 J¨ urgen Senker, 3 Dirk Johrendt, 4 Bernd D. Mosel, 2 and H. Eckert 2 1 Institut f ¨ ur Anorganische und Analytische Chemie and SFB 458, Westf ¨ alische Wilhelms-Universit¨ at M ¨ unster, Wilhelm-Klemm-Straße 8, 48149 M¨ unster, Germany 2 Institut f ¨ ur Physikalische Chemie and SFB 458, Westf¨ alische Wilhelms-Universit¨ at M ¨ unster, Schlossplatz 4/7, 48149 M ¨ unster, Germany 3 Department Chemie, Ludwig-Maximilians-Universit ¨ at M ¨ unchen, Butenandtstraße 5-13 (Haus D), 81377 M ¨ unchen, Germany 4 Institut f ¨ ur Anorganische Chemie und Strukturchemie, Lehrstuhl II, Heinrich-Heine-Universit ¨ at D¨ usseldorf, Universit ¨ atsstrasse 1, D-40225, D ¨ usseldorf, Germany Received 25 March 2002 ABSTRACT: Intermetallic lithium compounds are potential candidates as anode materials for battery applications. We report on the synthesis, crystal struc- tures, and chemical bonding of lithium–transition metal–stannides and indides. These structures are composed of two- or three-dimensionally infinite polyanions formed by the transition metal and tin (indium) atoms. Besides the crystal chemistry we re- port on magnetic properties, 7 Li solid state NMR, and 119 Sn M¨ ossbauer spectroscopy data in order to elucidate structure-property relations for this fam- ily of intermetallics. C  2002 Wiley Periodicals, Inc. Heteroatom Chem 13:506–513, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10095 Correspondence to: Rainer P¨ ottgen; e-mail: pottgen@uni- muenster.de. Contract grant sponsor: Fonds der Chemischen Industrie. Contract grant sponsor: Deutsche Forschungsgemeinschaft. Contract grant number: SFB 458. c  2002 Wiley Periodicals, Inc. INTRODUCTION Lithium-based battery materials enable the devel- opment of cells with potentials up to 4 V, which can store large amounts of energy [1]. A sudden en- ergy burst might cause local heating to high tem- peratures. This causes problems if the temperature rises above the melting point of lithium (454 K) when elemental lithium is used as anode material. Also the shape change of lithium anodes is puzzling. The reduced lithium may grow in the form of den- drites, fibers, and whiskers during the electrodepo- sition process, probably causing disconnection and electrical insulation or even electrical shortening be- tween the electrodes. Such problems can be avoided by using binary or ternary intermetallic lithium compounds, which have higher melting points. The intermetallics, how- ever, carry two disadvantages: (i) because of the al- loying element the density increases and (ii) the lithium activity decreases. So far, only the phase diagrams of the bi- nary systems are well established [2,3]. Most 506