7Li nuclear magnetic resonance studies of hard carbon and graphite/hard carbon hybrid anode for Li ion battery

✍ Scribed by H. Fujimoto; A. Mabuchi; K. Tokumitsu; N. Chinnasamy; T. Kasuh

• Publisher: Elsevier Science
• Year: 2011
• Tongue: English
• Weight: 694 KB
• Volume: 196
• Category: Article
• ISSN: 0378-7753
• DOI: 10.1016/j.jpowsour.2010.09.026

✦ Synopsis

The hard carbon is attractive for the Li ion battery because of its higher capacity than the theoretical value of 372 Ah kg -1 based on the composition of stage 1 Li-intercalated graphite, LiC 6 . However, since the Lidoping reaction occurs at the potential of around 0 V versus Li/Li + reference electrode, it is often pointed out the possibility of Li metal deposition on the surface of anode. From the viewpoint of the safety, it may be a moot point. In the present study, 7 Li NMR measurement was performed to estimate the degree of Li metal deposition on the surface of graphite and hard carbon anode. As a result, it is clarified that the Li metal deposition does not occur up to 110% over-discharge of the reversible capacity of hard carbon, whereas in the case of graphite anode, Li metal deposition occurred above 105% over-discharge of the capacity. From the 7 Li NMR spectroscopy, the safety limit of hard carbon is rather superior to that of graphite.