Intercalation reactions and carbide formation in graphite-lithium system

In the present work we have investigated a lithium-graphite system by DTA, DSC, heat flow calorimetric, and volumetric methods in a ''piston-cylinder apparatus'' under high pressures (23 kbar). For the first time, we have determined the enthalpies (Delta H-form) of LiC6 (1 stage) and LiC12 (2 stage) formation by the direct calorimetric method at 455 K. It was stated that the values are -13.9 +/- 1.2 kJ/mol Li and -24.8 +/- 1 kJ/mol Li, respectively. We have defined the enthalpies and temperatures of (3D) --> (2D) transitions in LiC6 (T = 711 +/- 5 K, Delta H-ph.tr. = 1.1 +/- 0.3 kJ/mol Li) and in LiCl2 (T = 472 +/- 5 K, Delta H-ph.tr = 1.45 +/- 0.2 kJ/mol Li). The rhombohedral modification of Li2C2 was explored at T = 293- 1000 K. Only one phase transition at T = 716 +/- 6 K (Delta(ph.tr.) = 5.56 +/- 0.09 kJ/mol Li2C2) was detected. The compressibility of Li2C2 was investigated at pressures up to 23 kbar and at room temperature. The change of molar volume (Delta V/V-0, %) was -2.07 +/- 0.07 (10 kbar) and -3.46 +/- 0.14 (22 kbar). We studied the carbide formation in Li-GICs at ambient and high pressure (P = 60 kbar) as well.