Available online at www.sciencedirect.com SCIENCE@DIRECTe JaUINAl 01 POWER SOURCIS LiMn204 prepared by different methods at identical thermal treatment conditions: structural, morphological and electrochemical characteristics H. Gadjov a ,*, M. Gorova a , V. Kotzeva a , G. Avdeev a , S. Uzunova b , D. Kovacheva a a Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, II I 3 Sofia, Bulgaria b Central Laboratory of Electrochemical Power Sources, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria Nano-crystalline LiMnz04 materials were obtained by three different methods: thermal decomposition of mixtures of corresponding metal carbonates or nitrates, Pechini method and self-combustion reaction (SCR) method using common sugar-sucrose as a fuel. Phase composition, morphology, crystallite- and particle sizes of materials were studied by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Contrary to thermal decomposition of metal carbonates or nitrates mixtures, Pechini and SCR methods allowed synthesis of a single-phase product at 400°C, but the optimal temperature range for preparing of LiMnz04 spinel with good electrochemical properties was found to be 600-650°C. Both latter methods provided good control of the chemical composition and microstructure of the active material. The SCR method yields a fine LiMnz04 spinel, having high initial specific capacity of 116mA h/g and low capacity fade during cycling. The simple procedure of self-combustion method is time and energy saving, and thus is promising for commercial application. © 2004 Elsevier B.Y. All rights reserved. Lithium manganese oxide spinel LiMn204 is an interest- ing and promising cathode material for rechargeable lithium batteries [1-3]. In comparison with layered LiCo02 and LiNi02, its three-dimensional structure permits a reversible electrochemical extraction of the Li+ ions, at about 4 V ver- sus LilLi+, to A-Mn02 without lattice collapse [4]. Addi- tional advantages are the relatively high theoretical capacity (148 mA h/g), low cost with ease preparation and environ- mental harmlessness [5]. A problem to overcome for com- mercial application of this material is its fast capacity fading with charge/discharge cycling [6]. This fact has been related to instability of the active phase caused by several possible factors like a slow dissolution of the cathode material into the electrolyte, high value of the relative volume changes accompanying charge/discharge cycling, Jahn- Teller distor- tion effect in deeply discharged electrodes [7,8]. The sto- ichiometry, crystal structure and morphology of the active material are of essential importance for its electrochemical * Corresponding author. E-mail address:didka@svr.igic.bas.bg (H. Gadjov). 0378-7753/$ - see front matter © 2004 Elsevier B.V. All rights reserved. doi: 10.1 016fj .jpowsour.2004 .03 .027 properties. All these factors are closely related to the method of synthesis. Many procedures for preparation of spinel LiMn204 materials have been proposed in the literature during last years. The classical ceramic synthesis by a solid-state reac- tion between oxides [9,10] has been used extensively, but it requires prolonged heat treatment at relatively high tem- peratures (>700 0c) with repeatedly intermediate grinding. Moreover, this method does not provide good control on the crystalline growth, compositional homogeneity, morphol- ogy and microstructure. As a consequence, final products consist in relatively large particles (> 1 flm) with broad particle size distribution. In order to overcome these dis- advantages, various preparative techniques, known as well as "soft-chemistry" methods, have been developed. Such techniques are based on the processes of co-precipitation, ion-exchange or thermal decomposition at low tempera- ture of appropriate organic precursors obtained by sol-gel [11,12], xero-gel [13], Pechini [14,15], freeze-drying [16], emulsion-drying [17] methods. They lead to homogeneous spinel materials with small particle size but require expen- sive initial or intermediate reagents and involve complex preparative procedures.