Manganese-based cathode materials have attracted significant interest in zinc-ion batteries (ZIBs) due to their high theoretical capacity, affordability, and environmentally friendly nature. Recently, Na2Mn3O7 (NMO) has emerged as a promising electrode material for ZIBs owing to its unique triclinic crystal structure which consists of infinite parallel [Mn3O7]2⁻ layers. This layered framework includes a vacancy at one of the seven Mn sites, which plays a crucial role in facilitating the insertion and accommodation of incoming Zn2+ ions, despite their relatively large ionic radius. This structural feature allows for efficient zinc intercalation, transforming NMO into a Zn-Mn-based system electrochemically. In this study, the focus is on investigating the mechanism of self-ion exchange occurring in NMO, utilizing an electrolyte composed of 2M ZnSO4 and 0.1M MnSO4, exhibiting a reversible capacity of ~240 mAh g-1 at C/10 rate with a coulombic efficiency of ~99%. The self-ion exchange mechanism and structural changes during the battery operation investigated using ex-situ X-ray diffraction and X-ray photoelectron spectroscopy analysis. The reversible phase transformations between hydrated and partially dehydrated states suggests a robust mechanism for Zn2+ ion insertion and extraction, contributing to the stability and performance of the Zn-Mn electrode material in zinc-ion battery applications.