No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

The surface of LiCoO 2 cathodes was modified with Al 2 O 3 , TiO 2 , and ZrO 2 by a chemical processing procedure followed by heat treatment at 300°C in air for 4 h. The surface-modified LiCoO 2 samples show much better capacity retention at both 25 and 60°C than the unmodified LiCoO 2 cathode to higher cutoff charge voltages of as high as 4.7 V vs. lithium. For example, Al 2 O 3 -modified LiCoO 2 shows approximately 180 mAh/g at 4.5 to 3.2 V with a capacity fade of only 8% in 100 cycles, compared to 32% for the unmodified LiCoO 2 . Transmission electron microscopic studies reveal that the guest materials are present as loose oxides ( Al 2 O 3 and ZrO 2 ) or as monolayers ( TiO 2 ) on the surface of LiCoO 2 particles. The improved capacity retention and the higher reversible capacity (180 mAh/g) of the surface-modified LiCoO 2 compared to the unmodified LiCoO 2 (140 mAh/g) could be due to a suppression of the chemical and structural instabilities of the charged Li 1 − x CoO 2 cathodes and/or reduction of interparticle stresses and strains. © 2003 The Electrochemical Society. All rights reserved.

No abstract