Rechargeable magnesium (Mg) and calcium (Ca) metal batteries (RMBs and RCBs) are promising alternatives to lithium (Li)-ion batteries due to their significantly higher crustal abundance and energy density. However, RMBs and RCBs are still plagued by high overpotentials associated with parasitic reactions and sluggish kinetics resulting from strong electrostatic interaction with the solvation sheath and cathode hosts. Here we significantly reduce the overpotentials associated with the interfacial charge transfer through reorganization of the methoxyethyl amine-based chelants in the first solvation sheath of Mg²⁺, enabling stable and highly reversible cycling of Mg||Mg_0.15MnO₂ full cell with energy density of 412 Wh kg^-1 and Ca||Mg_0.15MnO₂ full cell with energy density of 471 Wh kg^-1. The barrier for solvation sheath reorganization can be tuned by molecular structure of the chelants and the design principle is generally applicable in a variety of ether solvents, thus providing a highly versatile electrolyte design strategy for divalent metal batteries.