The interaction potential of the lowest triplet excited state, a(3)Sigma (+)(u), for Li-2 has been calculated using the ab initio method, QCISD(T) and the correlation-consistent valence polarised quintuple zeta basis set, cc-pV5Z. Equilibrium constants and vibrational levels for Li-7(2) are in good agreement with experimental determinations. The a(3)Sigma (+)(u) energy curve for Li-2 is characterised at the QCISD(T, full)/cc-pV5Z level of theory by the parameters D-e, D-o, R-o, omega (e), and omega (e)x(e) which are found to be 334.145 cm(-1), 301.989 cm(-1), 4.1686 Angstrom, 65.400 cm(-1) and 3.208 cm(-1), respectively.