Intercalation Pseudocapacitance in 2D VS2/Ti3C2Tx MXene Hybrids for All‐Climate and Long‐Cycle Sodium‐Ion Batteries

Abstract

AbstractLayered transition metal dichalcogenides have great potential as anodes of sodium‐ion batteries (SIBs) due to their high theoretical specific capacity. However, the restacking severely limits their accessible sites, leading to undesirable specific capacity, cycle stability, and working temperature range. Herein, a hierarchical 2D VS2/Ti3C2Tx MXene hybrid is designed via a simple liquid‐mixing method, where VS2 is confined in the conductive Ti3C2Tx matrix with chemical connections built between them. The in situ transmission electron microscopy analyses reveal that the hybrid depends on a very fast and reversible intercalation/de‐intercalation process between VS2 and NaxVS2 (where x = 1) to store sodium. Theoretical calculations disclose that the Ti3C2Tx matrix remarkably enhances the charge transfer and alleviates the volume expansion of VS2 especially after Na+ is inserted. Consequently, such a rational design exhibits an intercalation pseudocapacitance‐dominant mechanism, with excellent specific capacity (522 mAh g−1 at 0.2 A g−1), rate capability (342 mAh g−1 at 10 A g−1), cycle life (116% after 3000 cycles), and also all‐climate workability (with high specific capacity and long‐term cycle stability even at 70 and −40 °C). This study may open up a new vision to design fast‐charging, long‐cycle, and all‐climate SIBs anodes based on the intercalation pseudocapacitance.