Low voltage
Negative electrode materials are traditionally constructed from graphite and other carbon materials, although newer silicon based materials are being increasingly used (see Nanowire battery). These materials are used because they are abundant and are electrically conducting and can intercalate lithium ions to store electrical charge with modest volume expansion (ca. 10%). The reason that graphite is the dominant material is because of its low voltage and excellent performance. Various materials have been introduced but their voltage is high leading to a low energy density. Low voltage of material is the key requirement; otherwise, the excess capacity is useless in terms of energy density.