Vanadium Oxide Pillared by Interlayer Mg2+ Ions and Water as Ultralong-Life Cathodes for Magnesium-Ion Batteries

Magnesium-ion batteries (MIBs) show great potential for large-scale energy storage because of the advantages of low cost and safety, but their application is severely hindered by the difficulty in finding desirable electrode materials. Herein, we develop a bilayer-structured vanadium oxide (Mg0.3V2O5·1.1H2O) with synergistic effect of Mg2+ ions and lattice water as the cathode material for MIBs. The pre-intercalated Mg2+ ions provide high electronic conductivity and excellent structural stability. The lattice water enables fast Mg2+ ions mobility because of its charge shielding effect. As a result, the Mg0.3V2O5·1.1H2O exhibits excellent rate performance and an unprecedented cycling life with capacity retention of 80.0% after 10,000 cycles. In addition, the Mg0.3V2O5·1.1H2O exhibits good electrochemical performance in full MIBs. This scalable Mg2+ host material is a promising candidate as a cathode for MIBs, and its high performance is expected to meet the requirements for large-scale storage applications.