Layered hybrid phase Li2NaV2(PO4)3/carbon dot nanocomposite cathodes for Li+/Na+ mixed-ion batteries

Abstract

Hybrid phase Li2NaV2(PO4)3 (H-LNVP) is one of the most promising cathode materials for Li+/Na+ mixed-ion batteries. Here we have successfully synthesized layered hybrid phase Li2NaV2(PO4)3/carbon dot (H-LNVP/CD) nanocomposites via a simple sol-gel and carbon thermal reduction method and its inserted-extracted mechanism is investigated. As a novel composite cathode, H-LNVP/CD nanocomposite cathode delivers 158 mA h g-1 of reversible capacity at 0.1C in a Li+/Na+ mixed-ion cell with the electrochemically active redox reactions of V3+/V4+ and V4+/V5+, which is far higher than single phase contrastive samples. The cell exhibits one main high voltage plateau with well-defined discharge voltage near 3.7 V, and a coulombic efficiency of approximate 100 percent at 10C. Because the carbon dots on the surface of layered H-LNVP nanoparticles can remarkably enhance their electronic conductivity, the cell still exhibits a higher specific capacity of about 89.4 mA h g-1 at 10C. These results are attributed to the nanocomposite structure of H-LNVP and CDs. This work will contribute to the development of Li+/Na+ mixed-ion batteries.