Chromium doping as a new approach to improve the cycling performance at high temperature of 5 VLiNi0.5Mn1.5O4-based positive electrode

LiCr2 gamma Ni0.5-gamma Mn1.5-gamma O4 (0 < Y <= 0.2) spinels have been synthesized by a sucrose-aided combustion method. Two sets of Cr-doped samples have been obtained by heating the "as-prepared" samples at 700 and 900 degrees C for 1 h. X-ray diffraction and thermogravimetric data show that pure and single phase spinels with similar lattice parameter have been synthesized. The homogeneity and the sub-micrornetric Particle size of the spinels have been shown by SEM and TEM. The main effect of the temperature is to increase the particle size from approximate to 60 to approximate to 500 nm, on heating from 700 to 900 degrees C. The study of the influence of Cr-dopant content and thermal treatment on the electrochemical properties at 25 degrees C and at 55,C has been carried out by galvanostatic cycling in Li-cells. The discharge capacity (approximate to 130 mAh g(-1)) does not noticeably change with the synthesis conditions; but the cycling performances are strongly modified. Key factors that control the cycling performances have been determined. The most highlighted result is that spinels heated at 900 degrees C with Y <= 0.1 have very high capacity retention at 55 degrees C (>96% after 40 cycles, cyclability >99.9% by cycle) indicating that metal doping is a new approach to prepare 5 V LiNi0.5Mn1.5O5-based cathodes with excellent cycling performances at high temperature. (C) 2008 Elsevier B.V. All Fights reserved.