Low-temperature synthesis of graphite particles by chemical vapor infiltration and their electrochemical properties for lithium-ion battery

Abstract

Using pressure-pulsed chemical vapor infiltration technique, pyrolytic carbon (pyrocarbon) was deposited at low temperature below 1100°C from the source gases of C6H6 (6%)-H2 into Ni-foam as catalyst. Pyrocarbon could be deposited at 650 °C or higher. The crystallinity was increased with the temperature elevation up to 900°C. It was found by XRD and Raman spectroscopy that high crystalline pyrocarbon particles having mainly graphite phase were deposited at 800-900°C. However, low crystalline carbon was co-deposited under the condition of temperature above 900 °C. For the samples obtained at 900°C or lower, the charge-discharge behaviors were similar to that of high crystalline natural graphite. On the other hand, “sloping region” in charge-discharge curves were observed for the sample obtained at 1000 and 1100 °C, resulting from the co-deposition of low crystalline carbon. The sample obtained at 850 t showed the highest reversible capacity of 352 mAhg-1 at a current density of 30 mAg-1, and 8 % of the capacity was maintained even at 3000 mAg-1.