Overview on the intercalation reactions of lithium alloys into graphite

Lithium intercalates easily into graphite either by chemical way or by electrochemical way. This well-known reaction leads to the first stage LiC6 binary compound. However, it is more difficult to prepare a ternary compound by intercalation of a lithium alloy. This is mainly due to thermodynamical causes.Nevertheless, it has been observed that a few well-chosen alloys (Ca–Li and Eu–Li) are able to intercalate into graphite. Calcium and europium have been used for well defined reasons. Although in these alloys both metals present are able to intercalate by themselves, the intercalated sheets are poly-layered. This observation is entirely original, but it can be easily explained.On the other hand, it has been established that, using well-chosen lithium alloys, calcium and europium can also intercalate alone into graphite, leading to the corresponding binary phases. In these occasions, lithium appears essentially as a factor able to promote the melting of the second metal and its intercalation by a preliminary spreading of the graphene planes.