High-performance magnesium/sodium hybrid ion battery based on sodium vanadate oxide for reversible storage of Na+ and Mg2+

Magnesium ion batteries (MIBs) are a potential field for the energy storage of the future but are restricted by insufficient rate capability and rapid capacity degradation. Magnesium-sodium hybrid ion batteries (MSHBs) are an effective way to address these problems. Here, we report a new type of MSHBs that use layered sodium vanadate ((Na, Mn)V 8 O 20 ·5H 2 O, Mn-NVO) cathodes coupled with an organic 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) anode in Mg 2+ /Na + hybrid electrolytes. During electrochemical cycling, Mg 2+ and Na + co-participate in the cathode reactions, and the introduction of Na + promotes the structural stability of the Mn-NVO cathode, as cleared by several ex-situ characterizations. Consequently, the Mn-NVO cathode presents great specific capacity (249.9 mA h g −1 at 300 mA g −1 ) and cycling (1500 cycles at 1500 mA g −1 ) in the Mg 2+ /Na + hybrid electrolytes. Besides, full battery displays long lifespan with 10,000 cycles at 1000 mA g −1 . The rate performance and cycling stability of MSHBs have been improved by an economical and scalable method, and the mechanism for these improvements is discussed.