Li₅VF₄(SO₄)₂: A Prototype High-Voltage Li-Ion Cathode

A Li-rich polyanionic compound based on V³⁺ with a previously unknown structure, Li₅VF₄(SO₄)₂, has been developed as a high-voltage cathode material for Li-ion batteries. The solvothermal preparation of this material, crystal structure solution, and initial electrochemical characterization are presented. An analysis based on density functional theory electronic structure calculations suggests that a high voltage close to 5 V is required to extract two Li ions and to reach the oxidation state of V⁵⁺. However, the use of conventional carbonate-based electrolytes, which exhibit increasing degradation above a potential of 4.3 V, does not permit the full capacity of this compound to be achieved at this time.