One-Dimensional Van Der Waals V₂Se₉ As a Conversion-Type Anode Material for Advanced Li Rechargeable Batteries

Volume expansion of active materials during lithium storage is one of the main issues in Li-ion batteries (LIBs) that should be addressed. In particular, large volume changes and particle cracking are problematic for electrode materials based on conversion reaction, which are considered attractive anode materials with high energy densities. In this study, a one-dimensional van der Waals (1D vdW) material, V 2 Se 9 , is proposed as a conversion-type anode material for LIBs. The V 2 Se 9 electrode material has a 1D chain molecular structure with vdW interactions between chains to form a bulk crystal structure. The spaces between the 1D chains act as structural buffers and provide short Li + diffusion paths that can improve the electrochemical performance of the electrode materials. The V 2 Se 9 electrode exhibits a high reversible capacity of 563.3 mAh g -1 at 100 mA g -1 and a high rate capability of 109.1 mAh g -1 at 3200 mA g -1 . The capacity retention of V 2 Se 9 electrodes is 83.72 % after 100 cycles. Synchrotron X-ray diffraction and X-ray absorption spectroscopy reveal the formation of Li 2 Se and V metal, indicating that Li ion storage occurs via the conversion reaction. The structural stability of V 2 Se 9 is demonstrated using SEM measurements of the discharged and charged V 2 Se 9 electrodes during cycling. These results demonstrate the reaction mechanism of V 2 Se 9 and highlight the potential of 1D vdW materials as high-performance anode materials in LIBs.