High performance anode for sodium-ion batteries: Calcium pre-intercalated layered vanadium oxide/carbon composite
Sodium ion batteries (SIBs) are considered as a promising candidate in the field of large-scale power grids and power storage, owing to their abundant reserves and low price. As a promising intercalated SIBs electrode, vanadium-based compounds have multiple oxidation states, rich coordination polyhedron structure and open lattice frameworks. But those materials are prone to occur the irreversible electrochemical reactions and produce metastable structural materials in the process of electrochemical reaction, resulting in a rapid decrease in capacity. Herein, a novel bilayer-structured vanadium oxide (CaV 8 O 20 ·3H 2 O)/Carbon composite material with high specific capacity and long cycling life was synthesized. The CaV 8 O 20 ·3H 2 O in this research has overcome the shortcomings of most vanadium-based electrode materials. In the ex-situ mechanism of this study, it was proved that the insertion of calcium ions can effectively maintain the stability of the interplanar spacing of the material and carry out sufficient redox reactions. Combined with the results of electrochemical performance comparison and mechanism analysis, a uniform carbon coating can improve the electrochemical stability and specific capacity of CaV 8 O 20 ·3H 2 O by increasing the conductivity of the material and inhibiting adverse side effects. The reported V-based carbon composite anode material exhibited a remarkable electrochemical property with a capacity of 0.2 A g −1 and the capacity retention rate was 92.7% after 200 cycles, and the capacity retention rate was 72% after 450 cycles at a current density of 5.0 A g −1 . The novel pre-intercalation model may provide a new perspective for the development of vanadium-based materials in SIBs.
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