The diffusion dynamics of a series of lithium sulfate substituted phosphate glass materials xLi(2)SO(4)center dot(1 - x)LiPO3 has been probed by quasielastic neutron scattering. Amorphous Li ion conductors are attractive as electrolyte materials for all-solid state batteries because they are highly isotropic and chemically stable. Local disorder is expected to reduce barriers to ion migration - leading to improved ionic conductivity relative to their crystalline counterpart - while minimizing unwanted electron transport. We report Li self-diffusion in these materials on a length scale comparable to the interatomic spacings, obtaining values D similar or equal to 55 +/- 4 x 10(-8) cm(2)/s at 450 K. Elastic neutron scattering measurements show an alteration of the phosphate chain backbone of the glass material.