Rate Properties and Elevated-Temperature Performances of LiNi(0.5-x)Cr(2x)Mn(1.5-x)O(4) (0 <= 2x <= 0.8) as 5 V Cathode Materials for Lithium-Ion Batteries

A series of Cr-substituted spinel cathodes LiNi(0.5-x)Cr(2x)Mn(1.5-x)O(4) (0 <= 2x <= 0.8) has been prepared and their electrochemical properties were characterized at different C rates and temperatures. Although the pristine Li[Ni(0.5)Mn(1.5)]O(4) showed a capacity loss from similar to 130 mAh g(-1) at 0.2C to similar to 10 mAh g(-1) at 10C at room temperature, LiNi(0.4)Cr(0.2)Mn(1.4)O(4) showed capacity retention similar to 93.8% after 400 cycles under the same conditions and LiNi(0.45)Cr(0.1)Mn(1.45)O(4) gave the best rate property. At 55 degrees C, LiNi(0.5)Mn(1.5)O(4) retained similar to 80.5% of its capacity after 50 cycles; 98, 92.1, and 91.7% capacities were still observed for LiNi(0.475)Cr(0.05)Mn(1.475)O(4), LiNi(0.45)Cr(0.1)Mn(1.45)O(4), and LiNi(0.4)Cr(0.2)Mn(1.4)O(4), respectively. Structural analyses and surface morphology changes show that although no second phase was detected during cycling, there is a surface rearrangement on the electrodes. Elemental analyses indicated that the Cr substitution helps to suppress the surface atomic rearrangement, which improves the electrochemical performance. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3491365] All rights reserved.