The method of semi-localized crystalline orbital (SLCO) is presented to investigate the influence of homopolar binding on the cohesive energies of ionic crystals. The computations are performed for LiH crystal. As a result, it is shown that the discrepancy between the theoretical value of the cohesive energy of LiH crystal, which was calculated by Lundqvist, and the observed one is removed by taking homopolar binding into account. Furthermore, the relation between the energy band structure and SLCO is discussed and it is shown that SLCO corresponds to Wannier's functions of the valence and conduction bands for the case of LiH crystal where the valence and conduction bands are non-degenerate.