Lithium phosphorous oxynitride ion-conducting glasses, prepared by radio-frequency magnetron sputtering, were a key constituent for the first all-solid-state (thin film) lithium batteries on the market, thanks to a particular combination of properties. Indeed, this solid electrolyte is compatible with both high voltage cathodes and the lithium metal anode, has negligible electronic conductivity and a good ionic conductivity. In the context of the development of new all-solid-state systems, it can now become a useful tool used to mitigate interfacial electrode/electrolyte reactivity. The origins of its outstanding ionic conductivity compared to their crystalline counterparts as well as the interplay between structure and ionic transport in this electrolyte has remained so far somewhat elusive. In this study, we have applied for the first time to this class of materials a methodology based on impedance spectroscopy (EIS) analyses to isolate the distinct energetic contributions to the ionic conduction process namely, the enthalpies for defect formation and migration. The variation of these enthalpies as a function of the nitrogen content is correlated with structural aspects unveiled by Solid-State Nuclear Magnetic Resonance (SS-NMR) and X-ray Photoelectron Spectroscopy (XPS) depth profiling. Our results indicate that the amorphous structure generates a striking decrease of the enthalpy related to defect formation, while the nitrogen incorporation in the material tends to decrease the enthalpy of migration.