Effect of surface fluorination on the electrochemical behavior of petroleum cokes for lithium ion battery

Surface structure change and electrochemical behavior of fluorinated petroleum coke samples (petroleum cokes: petroleum coke and those heat-treated at 1860 degrees C. 2300 degrees C and 2800 degrees C, abbreviated to PC, PC1860, PC2300 and PC2800, respectively) have been investigated. Surface oxygen of petroleum coke was decreased by the fluorination using elemental fluorine. Raman and EPR spectroscopies revealed that surface fluorination increased surface disorder and lattice defects. F-19 NMR spectrum suggests that distribution of fluorine atoms in PC fluorinated 300 degrees C was similar to that in graphite fluoride with covalent C-F bonds. Surface areas of fluorinated petroleum cokes were nearly the same as those of non-fluorinated ones or only slightly increased by fluorination, except PC fluorinated at 300 degrees C. It is noted that first coulombic efficiencies of PC2300 and PC2800 were highly increased to 80-84% by the fluorination at 300 degrees C. These values of 80-84% were 12-18% hi-her than those of non-fluorinated PC2300 and PC2800. (c) 2004 Elsevier B.V. All rights reserved.