Thermal and electrochemical studies of carbons for Li-ion batteries 2. Correlation of active sites and irreversible capacity loss

Thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) involving air oxidation of fluid coke, coal-tar pitch delayed coke and need le coke suggested that active sites are I,resent which can be correlated to the crystallographic parameters, L-a and L-c, and the d(002) spacing. This finding was extended to determine the relationship between active sites on carbon and their role in catalyzing electrolyte decomposition leading to i rreversible capacity loss (ICL) in Li-ion batteries. Electrochemical data f rom this study with graphitizable carbons and from published Literature wer e analyzed to determine the relationship between the physical properties of carbon and the ICL during the first charge/discharge cycle. Based on this analysis, we conclude that the active surface area, and not the total BET s urface area, has an influence on the ICL of carbo,ns for Li-ion batteries. This conclusion suggests that the carbon surface structure plays a signific ant role in catalyzing electrolyte decomposition. (C) 2000 Elsevier Science S.A. All rights reserved.