Intercalation of lithium into graphite and other carbons

Abstract

Lamellar graphite-lithium compounds of the first, second, third and fourth stages which are respectively brass-yellow, steel-blue, dark-blue and black had been prepared by the two following methods: 1. (a) by heating graphite and lithium at 400°C in a copper or stainless-steel tube; 2. (b) by compressing lithium powder with crushed natural graphite under an argon atmosphere in a glove-box. The reaction begins at room temperature. An homogeneous product is obtained by annealing the pellet at 200°C in vacuum or in argon. Whereas the first method leads only to the first stage compound LiC 6 which is stoichiometric, pure phases of any stage may be obtained according to the composition of the initial mixture by the second method. The analysis of pure phases shows that the compounds of stages n > 1 present large variations of the stoichiometry. The unit cells of first stage LiC 6 and second stage LiC 12 compounds belong to P6/mmm space group with respective parameters a = 4.305 ± 0.001 Å, c = 3.706 ± 0.01 Å and a = 4.288 ± 0.002 Å, c = 7.065 ± 0.02 Å. Lithium intercalates also into soft and hard carbons, including fibers, like the heavy alkali metals.