Surface/Chemically modified LiMn2O4 cathodes for lithium-ion batteries

LiMn2O4 spinel oxide has been surface/chemically modified with LixCoO2, LiNi0.5Co0.5O2,Al2O3, and MgO using a chemical processing procedure followed by heat-treatment at 300-800degrees C. The surface/chemically modified samples show much better capacity retention at both 25 and 60degreesC than does the unmodified LiMn2O4 (41% fade in 100 cycles at 60degreesC). Among the various compositions investigated, the LiNi0.5Co0.5O2-modified sample shows superior capacity retention with only 2.8% fade in 100 cycles at 60degreesC with around 110 mAh/g. The Al2O3-modified sample shows a higher capacity of 130 mAh/g, but with a faster fade (16% in 100 cycles at 60degreesC). The Li0.75CoO2-modified sample shows the best combination of capacity (124 mAh/g) and retention (8% fade in 100 cycles at 60degreesC). The modified samples also exhibit better capacity retention after aging at 55degrees C at 60-70% depth of discharge. (C) 2002 The Electrochemical Society.