High Capacity Surface-Modified LiCoO2 Cathodes for Lithium-Ion Batteries

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