One-dimensional van der Waals transition metal chalcogenide as an anode material for advanced lithium-ion batteries

In response to the swiftly growing demand for batteries in the electric vehicle sector, it is necessary to develop novel anode materials with elevated energy and power density. As an alternative to conventional graphite anodes, conversion-based transition metal chalcogenide materials were proposed. However, the tremendous volume expansion and the poor kinetics associated with conversion-based transition metal chalcogenide electrodes limit their further application. In this study, we explore the application of one-dimensional van der Waals (1D vdW) Nb2Se9 as an anode material for Li-ion batteries (LIBs). The Nb2Se9 electrode, when tested at a current rate of 0.1 A g-1 over 100 cycles, exhibits a substantial reversible specific capacity of 542.2 mA h g-1. Even when subjected to a current density of 3.2 A g-1, it maintains a high capacity of 272.0 mA h g-1. Combined results of synchrotron X-ray absorption spectroscopy and scanning electron microscopy show that the one-dimensional Nb2Se9 phase is maintained after the accommodation of lithium ions. This result can be explained by the unique 1D vdW structure, which provides a short diffusion length and ample space to handle the volume expansion. Additionally, the substantial electron cloud of Se surrounding the Nb-Nb framework acts as a Se-Se buffer layer, protecting the one-dimensional structure. Therefore, Li ions can react with the externally exposed Se-Se buffer layer to form dispersed fragments, leading to superior structural stability. These results will not only enhance our understanding of the reaction mechanism within Nb2Se9 materials but also promote the potential utilization of 1D vdW materials as advanced electrode materials for Li-ion batteries. 1D vdW Nb2Se9 is a promising advanced anode material for LIBs due to superior electrochemical performance originating from its unique structural properties, which allow swift transport of Li ions and buffer the volume changes during Li-ion storage.