High‐Energy Aqueous Magnesium Hybrid Full Batteries Enabled by Carrier‐Hosting Potential Compensation

Underachieved capacity and low voltage plateau is ubiquitous in conventional aqueous magnesium ion full batteries. Such limitations originate from the electrochemistry and the low carrier-hosting ((de)intercalation) potential of electrode materials. Herein, via a strategy of enhancing the electrochemistry through carrier-hosting potential compensation, high-energy Mg²⁺ /Na⁺ hybrid batteries are achieved. A Mg_1.5 VCr(PO₄ )₃ (MVCP) cathode is coupled with FeVO₄ (FVO) anode in a new aqueous/organic hybrid electrolyte, giving reliable high-voltage operation. This operation enables more sufficient (de)intercalation of hybrid carriers (Mg²⁺ /Na⁺ ), thereby enhancing the reversible capacity remarkably (233.4 mA h g^-1 at 0.5 A g^-1 , 92.7 Wh kg^-1 _electrode , that is, ≥1.75-fold higher than those in conventional aqueous electrolytes). The relatively high Na⁺ -hosting potential of the electrodes compensates for the low Mg²⁺ -hosting potential and widens/elevates the discharge plateau of the full battery up to 1.50 V. Mechanism study further reveals an unusual phase transformation of FVO to Fe₂ V₃ and the low-lattice-strain pseudocapacitive (de)intercalation chemistry of MVCP.