Cellulose films of approximately 5 μm thickness, reconstituted from ionic liquid media onto a poly‐ethylene‐terephthalate (PET) film with a 5, 10, 20, or 40 μm diameter microhole, show current rectification when immersed in aqueous NaCl. For “asymmetric cellulose deposits” this rectification, or ionic diode behaviour, is then investigated as a function of ionic strength and microhole diameter. Future applications are envisaged in sustainable cellulose‐based desalination, sensing, or energy harvesting processes.