Lithium ion conductivity of a lithium compound is known to be influenced by an inert, non-lithium ion conductor additive. This paper reports an investigation of the effects of boron nitride (BN) addition to the conductivity of lithium iodide (Lil). The Lil:BN stoichiometry and heat treatment parameters (temperature and time) have been used as variables. It will be shown that lithium conductivity is strongly dependent upon heat treatment parameters. The activation energy for lithium ion transport also decreases with the addition of BN. Further analysis of activation energy data suggests that lithium ion motion takes place through interfacial regions of Lil and BN phases.