THE CORRELATION BETWEEN THE SURFACE-CHEMISTRY AND THE PERFORMANCE OF LI-CARBON INTERCALATION ANODES FOR RECHARGEABLE ROCKING-CHAIR TYPE BATTERIES

The correlation between the electrochemical properties of Li carbon in tercalation electrodes and their surface chemistry in solutions was in vestigated. The carbons investigated were primarily graphite and petro leum coke, and the solvent systems included methyl formate (MF), propy lene and ethylene carbonates, ethers and their mixtures. The surface c hemistry of the electrodes was studied using mainly diffuse reflectanc e Fourier transform infrared spectroscopy. The following aspects were studied: (i) the effect of temperature on the buildup of the surface f ilms; (ii) the effect of additives (e.g., CO2, crown ethers), (iii) th e behavior when the passive layer is built in one solution followed by cycling in another; and (iv) the effect of cosolvent in MF solutions. The results obtained further prove that the electrochemical behavior of these systems is surface film controlled. An understanding of the s urf ace chemistry of these electrodes enables judicious optimization o f carbon-solution systems for use in rechargeable Li batteries.