Negative electrodes: Graphite

Graphite has been used as a negative electrode in most of the commercially available rechargeable lithium-ion cells. Lithium ions are intercalated within graphite on charging and deintercalated on discharging at extremely negative potentials of about −3 V against the standard hydrogen electrode. Many of the advantages of lithium-ion cells, such as high voltage and high energy density, are realized not by positive electrode, but by graphite negative electrode. The electrochemical intercalation reactions at graphite negative electrode consist of various processes such as surface reactions, interfacial charge transfer reactions, and lithium diffusion inside the host. Each of the elementary processes plays a vital role and greatly affects the charge and discharge characteristics of graphite negative electrodes. In this article, fundamental aspects of graphite negative electrodes are reviewed, focusing on (1) charge and discharge characteristics of graphite and other carbonaceous materials, (2) electrolyte decomposition and surface film formation, and (3) diffusion of lithium ions in graphite.