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 Mg1.5VCr(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(electrode)(-1), 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 Fe2V3 and the low-lattice-strain pseudocapacitive (de)intercalation chemistry of MVCP.

Automated summary

By enhancing the electrochemistry and compensating for the carrier-hosting potential, researchers have successfully achieved high-energy Mg2+/Na+ hybrid batteries, significantly increasing the reversible capacity to over 1.75 times that of conventional aqueous batteries. Mechanism studies have revealed an unusual phase transformation of FVO and the pseudocapacitive (de)intercalation chemistry of MVCP.