LiCr0.18Mn1.82O4 spinel has been successfully synthesized by glycine-nitrate method. As a cathode material for lithium batteries it shows initial discharge capacity of 107.1 mAh/g and capacity retention of 93.3% after ten cycles.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Cvjetićanin, Nikola

Jugović, Dragana

Mitrić, Miodrag

Pavlović, N.

Stojković, Ivana

English

Repository of the Vinča Nuclear Institute (VinaR)

    PHYSICAL CHEMISTRY 2004   Proceedings    of the 7th International Conference on Fundamental and Applied Aspects of Physical Chemistry    Volume I and II         September 21-23, 2004 Belgrade, Serbia and Montenegro      PHYSICAL CHEMISTRY 2004  Proceedings   of the 7th International Conference on Fundamental and Applied Aspects of Physical Chemistry      Volume I and II       Editors A. Antić-Jovanović and S. Anić  ii                             ISBN 86-82457-12-x Title: Physical Chemistry 2004. (Proceedings) Editors A. Antić-Jovanović and S. Anić  Published by: The Society of Physical Chemists of Serbia, Student-ski trg 12-16, P.O.Box 137, 11001 Belgrade, Serbia and Montenegro Publisher: Society of Physical Chemists of Serbia  Printed by: "Jovan" Printing and Published Comp; 300 Copies; Number of Pages: x + 906; Format B5; Printing finished in September 2004.  Text and Layout: Aleksandar Nikolić    300 – copy printingiii PHYSICAL CHEMISTRY 2004.  G–19–P  SYNTHESIS OF LiCrxMn2-xO4 (x~0.18)  BY GLYCINE-NITRATE METHOD I. Stojković1, D. Jugović2, M. Mitrić3, N. Pavlović4 and N. Cvjetićanin11Faculty of Physical Chemistry, University of Belgrade, Studentski Trg 12-16, P.O. Box 137, Bel-grade, 2Institute of Technical Sciences, Serbian Academy of Sciences, Knez Mihajlova 35/IV, Bel-grade, 3The Vinča Institute of Nuclear Sciences,Laboratory for Theoretical and Condensed Matter Physics,P.O. Box 522, Belgrade, 4The Military Technical Institute of the SCG Army, Katanićeva 15, Belgrade, Serbia and Montenegro  Abstract  LiCr0.18Mn1.82O4 spinel has been successfully synthesized by glycine-nitrate method. As a cathode material for lithium batteries it shows initial discharge capacity of 107.1 mAh/g and capacity retention of 93.3% after ten cycles. Introduction  LiMn2O4 is a promising cathode material for ion-lithium batteries because it delivers high voltage, good capacity and it is a low cost and non toxic material. Unfor-tunately LiMn2O4 spinel shows considerable decrease in capacity during electro-chemical charging-discharging on the 4V plateau. Recently several dominant modes of capacity fade have been proposed: Mn-dissolution and concomitant Li-for-Mn ion ex-change at the end-of-discharge, and development of microstrain between two cubic phases formed during cycling [1,2]. The largest improvement in preventing capacity fade has been achieved by substitution of some manganese by other metal cations. These more robust spinels have higher average oxidation state of remaining  manga-nese (>3.5+). This leads to a lower theoretical capacity because of the lower number of lithium ions that can be extracted from the spinel structure before all manganese is oxidized. Not only the choice of Mz+ metal cation type but also its amount “x”, is im-portant for obtaining LiMxMn2-xO4 cathode material with adequate initial capacity and high capacity retention. Cr3+ is among the cations whose substitution for manganese gives best performance increase especially for x = 0.175 [1,3,4]  LiMxMn2-xO4 spinels are usually prepared by time and energy consuming solid state reaction, starting from carbonates and/or oxides [1-3,5]. In this work we tried to synthesize LiCrxMn2-xO4 (x~0.18) powder material by rapid glycine-nitrate method developed before for synthesis of  YBa2Cu3O7-x ceramics [6]. Experimental  1 M aqueous solutions of LiNO3, Mn(NO3)2·4H2O and Cr(NO3)3·9H2O were prepared from p.a. chemicals. They were mixed in appropriate ratio so the total vol-ume was 30-40 ml. Glycine was added in the mixture either as a solid or as a water solution. Its role was to serve both as a fuel for combustion and as a complex ant to prevent inhomogeneous precipitation of individual components prior to combustion. Amount of glycine was such to make glycine-to-nitrate molar ratio equal to 1.2. Pre-cursor solution was placed in a covered glass beaker and heated in an oven at 200oC  523PHYSICAL CHEMISTRY 2004.  G–19–P  until spontaneous ignition occurred. Ash resulting from combustion was heated at 800oC for 4 hours.  The XRPD experiments were done with the CuKα1, 2 radiations in 15-70o 2θ range with the 0.05o step and 2 seconds exposition time.  Electrochemical experiments were performed in a cell filled with argon. Elec-trolyte was 1 M LiClO4 in PC and EC mixture (1:1 mole ratio). Before dissolving p.a. LiClO4 was dried under vacuum at 120-140oC for at least 2 hours. PC and EC were distilled twice under vacuum, and both times middle ⅔ fraction was collected. Work-ing electrode was made from synthesized material, “Vulcan” carbon black and PVDF mixed in 90:5:5 weight percent ratio and deposited on platinum foil from slurry pre-pared in N-Methyl-2-Pyrrolidone. Active cathode material weighted 3.9 mg and was spread over 1.7 cm2 of Pt-foil surface area. Two glass tubes filled with lithium metal were used as double counter electrode. Results and Discussion  All reflections of obtained XRPD pattern correspond to pure spinel phase. Small shifts in 2θ values exist for all reflections comparing to LiMn2O4 diffraction pattern. Lattice parameter a = 8.223 Å has a lower value than for LiMn2O4 (a = 8.241-8.249 Å)[1,2,7]. This lattice contraction indicates that chromium-ion is incorporated into spinel manganese oxide [8] and a more complex oxide LiCr0.18Mn1.82O4 is formed.  For potential application the most important thing is to have acceptable elec-trochemical behavior of obtained cathode material. So we checked cycling characteris-tics of LiCr0.18Mn1.82O4 by charging electrochemical cell to 4.3 V and discharging to 3.3 V. Quite high current rate C/3 has been chosen. Current density was 112 µA/cm2. Ten cycles have been recorded. Fig.1 shows relationship between discharge capacity and cycle number for our LiCr0.18Mn1.82O4 comparing to LiMn2O4  prepared by solid state reaction and cycled at C/15 current rate [1]. Discharge capacity of LiCr0.18Mn1.82O4 synthesized by glycine-nitrate method changes from 107.1 in the first to 99.9 mAh/g in the tenth cycle. LiMn2O4 [1] although cycled with five times lower current rate de-creases a discharge capacity from 108.6 to 73.3 mAh/g in the first ten cycles. The ca-pacity retention of LiCr0.18Mn1.82O4 is 93.3% comparing to that of only 67.5% for LiMn2O4. As a conclusion it may be said that LiCr0.18Mn1.82O4 is successfully synthe-sized by a rapid combustion method delivering very good cyclability as a cathode ma-terial for lithium batteries.    524PHYSICAL CHEMISTRY 2004.  G–19–P    Figure 1. Discharge capacity of LiCr0.18Mn1.82O4 (glycine-nitrate method) and                 LiMn2O4 (solid state reaction [1]) versus cycle number.  References  [1] M. C. Tucker, J.A. Reimer, E.J. Cairns, J. Electochem. Soc., 2002, 149(5), A574. [2] Y. Shin, A. Manthiram, J. Electochem. Soc., 2004, 151(2), A204. [3] C. Sigala, D. Guyomard, Verbaere, Y. Piffard, M. Tournoux, Solid State Ionics, 1995, 81, 167. [4] C-H. Lu, Y. Lin, H-C. Wang, J. Mater. Sci. Lett., 2003, 22, 615. [5] R. Koksbang, J. Barker, H. Shi, M. Y. Saïdi, Solid State Ionics, 1996, 84, 1. [6] L. R. Pederson, G. D. Maupin, W. J. Weber, D. J. McReady, R. W. Stephens, Mat. Lett., 1991, 10, 437. [7] D. Jugović, M. Mitrić, N. Cvjetićanin, M. Miljković, V. Jokanović, D. Uskoković, Ma-ter. Sci. Forum, 2004, 453-454, 387.  [8] M. C. Tucker, J.A. Reimer, E.J. Cairns, J. Electochem. Soc., 2001, 148(8), A951.  525

Synthesis of LiCrxMn2-xO4 (x~0.18) by glycine-nitrate method

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Synthesis of LiCrxMn2-xO4 (x~0.18) by glycine-nitrate method

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