An advanced high-rate capability sodium-ion anode: Few-layered NbSe2 with a mechanism of parallel running intercalation and conversion.

[Display omitted] • Compared with bulk NbSe 2 , few-layered wgef-NbSe 2 nanosheets presented shortened activation cycles, lower reaction polarization, better cyclic stability, and accelerated ion diffusion kinetics. • The continuous and intensive charge accumulation region between the NbSe 2 interlayers ensures a strong adsorption tendency of Na+ in virtue of forming a certain Coulombic force. • The interlayers possess a lower Na+ diffusion barrier, which is as low as 0.18 eV, guaranteeing NbSe 2 to achieve rapid reaction kinetics. • During the sodiation, Coulomb force causes the shrinkage of the d -spacing of some specific lattice planes of the NaNbSe 2 intermediate. However, the other planes are immune to the Coulomb force, showing the expansion of d -spacing. • Wgef-NbSe 2 exhibits an intercalation and conversion parallel running mechanism that promises the high structural robustness and high theoretical capacity. The unique superconductivity and charge density wave transition characteristics of NbSe 2 make it worthy of exploring its electrochemical performance and potential applications in the field of batteries. Herein, the bulk NbSe 2 was successfully exfoliated into few-layered NbSe 2 nanostructures by wet grinding exfoliation approach, which solved the issues of its long activation period and poor cycle stability. The strong Nb-Se bond in the plane and weak van der Waals force between the adjacent layers could render the fast Na+ diffusion, provide abundant reaction sites and multi-directional migration paths, thus accelerate the ionic conductivity. The theoretical calculations verified the high Na+ adsorption tendency between the NbSe 2 interlayers stemming from the continuous region of charge accumulation. Thanks to the unique electronic and two-dimensional few-layered structures, the exfoliated NbSe 2 exhibited a high cyclic stability with a capacity of 502 mA h g−1 over 2800 cycles at 10 A/g. In addition, the reaction mechanism was studied by in - situ X-ray diffraction and other tests, indicating a reaction mechanism containing of simultaneous intercalation (N b S e 2 ↔ N a x N b S e 2 ↔ N a N b S e 2 ↔ N a 1 + x N b S e 2) and conversion processes in NbSe 2. This parallelly running mechanism not only alleviates the volume change but also ensures a high specific capacity. Additionally, different lattice planes of the NaNbSe 2 intermediate in the intercalation process experience varying degrees of contraction and expanding in d -spacing due to the influence of Coulombic force. [ABSTRACT FROM AUTHOR]