Magnesium batteries could offer high energy density without compromising safety due to the use of non­dendritic Mg metal anode. However, the charge­ dense divalent Mg²⁺ also makes cation ingress into and diffusion within cathode materials kinetically sluggish. It is therefore intriguing that recently organic cathodes were reported to deliver high energy and power even at room temperature. Herein we reveal that previous organic cathodes likely all operate on an MgCl ­storage chemistry sustained by a large amount of electrolyte that significantly reduces cell­ level energy. We go on to demonstrate Mg batteries featuring an Mg²⁺­ storage chemistry using quinone polymer cathode, Cl­ free electrolytes, and Mg metal anode. Under lean electrolyte conditions, the organic cathode in cells on Mg ­storage chemistry deliver the same energy while using ca. one tenth of the amount of electrolyte needed for the MgCl ­based counterparts. With the right combination of organic cathodes and chloride ­free electrolytes, the observed specific energy (up to 243 Wh kg­^-1), power (up to 3.4 kW kg^-­1), and cycling stability (up to 87%@2500 cycles) of Mg ­storage cells consolidate organic polymers as promising cathode candidates for high­ energy Mg batteries.