In this paper, some discussions are carried out based on several experimental results on the relationship between the interfacial structure of nano-granular films and their electronic or ionic conductivity characteristics. The studies showed that a film with excellent ionic implantation and electrochromic properties should, first of all, possess a structure on the nanoscale, together with high fraction of grain boundary and interfacial defects. The interfacial structure of nano-granular films could be changed from 'highly disordered' to 'highly ordered' through control of deposition parameters and post-deposition treatment. As a result, the ionic conductivity characteristics of films can be controlled, and the film structure and property can be designed and tailored according to application requirements.