A₂VO(SO₄)₂ (A = Li, Na) as Electrodes for Li-Ion and Na-Ion Batteries

We herein report the synthesis, crystal structure, and electrochemical performances of a new Li-based vanadium oxysulfate phase, Li₂VO­(SO₄)₂, whose structure is built on vanadyl-containing VO₅ square-based pyramids and SO₄ groups linked by vertices to form layers. Li₂VO­(SO₄)₂ presents a redox activity at 4.7 V vs Li⁺/Li⁰ with a reversible capacity of 50 mA·h/g, while the chemically similar but structurally different Na₂VO­(SO₄)₂ delivers a capacity of 60 mA h/g at 4.5 V vs Na⁺/Na⁰. Density functional theory calculations are also performed to rationalize our findings in terms of redox activity and phase stability.