Solution synthesis of VSe2 nanosheets and their alkali metal ion storage performance

Highlights: • Ultrathin VSe₂ hierarchical structure were synthesized using a facile solvothermal method. • The synthesis method provides a general idea to the rational growth of ultrathin nanosheets of other TMD materials. • The as-obtained products show good electrochemical performance toward the lithium and sodium ion storage. Vanadium diselenide (VSe₂) is a transition metal dichalcogenide with metallic conductivity, which makes it a potentially promising electrode material for electrochemical applications. However, the development of VSe₂ electrodes for such applications has been severely hampered by the difficulty of preparing nanosized products. In this work, a new facile solvothermal synthesis process is developed and optimized to synthesize ultrathin VSe₂ nanosheet assemblies. To obtain the ultrathin nanosheets, N-methyl pyrrolidone, which has similar surface energy to many transition metal dichalcogenides, was used as the solvent to limit the crystal growth along the c-axis direction. The resulting ultrathin VSe₂ nanosheets exhibit good performance toward alkaline ion (Li⁺ and Na⁺) storage, which can be significantly enhanced by carbon coating. Specifically, the carbon-coated VSe₂ nanosheets can deliver high capacities of 768 mA h g^-1 (Li⁺ storage) and 571 mA h g^-1 (Na⁺ storage) along with outstanding stability.