Structure-modulation of flower-like VS2 via ammonium ion intercalation for high performance potassium-ion batteries

Transition vanadium sulfide is a promising anode material for potassium-ion batteries (PIBs), but the volume variation during charge-discharge cycling and low electric conductivity seriously hinder its applications. Herein, we designed a multilayer lamellar self-assembled flower-like vanadium sulfide with ammonium ion intercalation (VS 2 –NF) by a facile and inexpensive hydrothermal method to improve its electrochemical potassium ion storage performance. By introducing ammonia during the hydrothermal synthesis process, the structures of vanadium sulfide transformed to nanoflowers composed by ultrathin nanosheets from the initial nanosphere structures. The intercalation of ammonium ion enlarges the lattice fringes and induces anisotropic growth of vanadium sulfide, resulting in a large number of mesopores and increased specific surface area as well as the reactive sites of vanadium sulfide, which contribute to the enhanced potassium ion storage performance. Consequently, the structure-modulated VS 2 –NF exhibits a high specific capacity of 507 mAh g −1 after 50 cycles at a current density of 100 mA g −1 . This approach provides a new routine for the modification of other transition metal disulfides as anode materials for PIBs.