Interlayer Engineering Construction of 2D Nb2CTx with Enlarged Interlayer Spacing Towards High Capacity and Rate Capability for Lithium-Ion Storage

The Li + storage rate capability and diffusion dynamics in two-dimensional (2D) materials are mainly determined by the interlayer spacing of materials. Investigating the effects of interlayer spacing on Li + diffusion rate in 2D materials can provide a theoretical guidance for developing the high rate 2D materials for Li + storage. Herein, a novel approach that P-phenylenediamine (PPDA) electrostatically intercalated into Nb 2 CT x layers is employed to facilitate fast Li + diffusion dynamics and improve diffusion rate for Li + storage. The PPDA molecules existed between Nb 2 CT x layers have “support and dragline” effects on layers structure during Li + insertion/exaction. The PPDA-Nb 2 CT x not only enlarges interlayer spacing ( d =1.27 nm) to accelerate the Li + diffusion rate, but also enhances the layered structure stability due to the “support and dragline” effects of PPDA molecules. The PPDA-Nb 2 CT x exhibits the excellent capacity of 400 mAh g −1 at a current density of 0.1 A g −1 and displays a superior capacity retention as 70.2 % at 5.0 A g −1 compared with that of 0.5 A g −1 . The PPDA-Nb 2 CT x //AC lithium ions hybrid capacitor (LIHC) delivers an excellent power density of 2754.8 W kg −1 at an energy density of 58.3 Wh kg −1 and a capacity retention with 80.0 % at 1.0 A g −1 after 1000 cycles. The interlayer engineering based on electrostatic intercalation provides a novel perspective to expand interlayer spacing, possessing a theoretical guidance for developing the Li + storage materials with high-rate capability. Graphical Make room for the ions : The approach that the interlayer engineering of electrostatic intercalation PPDA between Nb 2 CT x layers can enlarge interlayer spacing and facilitate fast Li + diffusion dynamics. The PPDA-Nb 2 CT x with 1.27 nm interlayer spacing not only offers the abundant transport highways to accelerate Li + diffusion, but also maintains the stability of layered structure due to the “support and dragline” effects of PPDA molecules. The method provides a novel perspective to design 2D materials with the high-rate capability for Li + storage.