Hybrid Mg/Li-ion batteries enabled by Mg2+/Li+ co-intercalation in VS4 nanodendrites

Hybrid Mg2+/Li+ batteries (MLIBs) are very intriguing energy storage devices that combine the advantages of Li and Mg electrochemical redox processes. However, the battery performances of MLIBs in previous researches are usually restricted by the fact that only Li+ ions are participated in the reactions on the cathodes. We propose that this obstacle can be overcome by significantly improving the diffusion/transfer kinetics of highly-polarized divalent Mg2+ ions in the cathode material, so that both Mg2+ and Li+ can be intercalated into the cathode material. Herein, we demonstrate that the electrochemical energy storage capability of MLIBs can be greatly improved by employing vanadium tetrasulfide (VS4) nanodendrites as cathode material. Benefited from the special one-dimensional atomic-chain structure, the VS4 nanodendrites are capable for the simultaneous reversible insertion/extraction of both Mg2+ and Li+ ions with fast diffusion kinetics, high capacity and long cycling stability. The MLIBs assembled with VS4 nanodendrites cathodes exhibit a high reversible capacity of ∼300 mAh g−1 at 500 mA g−1, and a high cycle stability with the capacity maintained at 110 mAh g−1 after 1500 cycles at 1000 mA g−1.