Layered Na2Ti3O7/MgNaTi3O7/Mg0.5NaTi3O7 Nanoribbons as High-Performance Anode of Rechargeable Mg-Ion Batteries

We report on layered Na2Ti3O2/MgNaTi3O2/Mg0.5NaTi3O2 nanoribbons for reversible electrochemical Mg storage. First, Mg intercalation with irreversible Na+ deintercalation takes place in the first discharge process (Na2Ti3O7 + Mg2+ + e(-) -> MgNaTi3O7 + Na+). Then, reversible Mg2+ insertion-extraction occurs in subsequent cycling processes (MgNaTi3O7 <-> Mg0.5NaTi3O7 + 0.5Mg(2+) + e(-)). This reaction with repeatable 0.5 M Mg2+ occupying the sites of Na+ coordinated to seven oxygen atoms offers a theoretical capacity of 88 mA h g(-1) (78 mA h g(-1) in practical test with Mg2+ electrolyte). Furthermore, the MgNaTi3O7 was used to assemble full Mg-ion batteries (MIBs) with Mg(ClO4)(2)-diglyme electrolyte and V2O5 cathode. The cell delivers a reversible capacity of 75 mA h g(-1) corresponding to an energy density of 53 Wh kg(-1). This work displays the potential of layered Na2Ti3O2/MgNaTi3O7/Mg0.5NaTi3O7 as the anode of MIBs.