Suppression of lithium deposition at sub-zero temperatures on graphite by surface modification

Lithium deposition on graphite anodes is considered as a main reason for failures and safety for lithium ion batteries (LIB). Different amounts of carbon coating on the surface of natural graphite are used in this work to suppress the amount of lithium deposited at -10 degrees C. Pulse polarization experiments reveal relative polarization of graphite anodes at various temperatures and show that lithium deposition is accelerated at lowered temperatures. Electrochemical experiments, along with photographs, scanning electron microscopy (SEM) images and ex-situ X-ray diffraction (XRD) data suggest that carbon coating not only suppresses the lithium deposition but also enhances the formation of LiC6 at -10 degrees C. The homogeneous potential profile on the graphite surface attained by the carbon coating explains such an improved low temperature performance. as it allows efficient Solid Electrolyte Interface (SEI) film formation, which is a prerequisite for safety LIB. (C) 2011 Elsevier B.V. All rights reserved.