The paper presents spectroscopic combinational scattering investigations of the molecular relaxation in LiNO3–LiClO4 and Li2CO3–Li2SO4 solid binary systems. It is found that the relaxation time for ν1(A) vibrations of NO3– anion in LiNO3–LiClO4 system is lower than in LiNO3 crystal. And the relaxation time for ν1(A) vibrations of CO32– anion in Li2CO3–Li2SO4 system is lower than in Li2CO3 crystal. The increase in the relaxation time is explained by the additional relaxation mechanism of the excited mode of nitrate and carbon ions which is observed in these systems. This mechanism is linked to the vibrations of other anions (ClO4– or SO42–) and a nucleation of the lattice phonon. Experiments show that the additional relaxation mechanism occurs due to the vibration difference which corresponds to the area of rather a high density of states of the phonon spectrum.