Highly Branched VS₄ Nanodendrites with 1D Atomic-Chain Structure as a Promising Cathode Material for Long-Cycling Magnesium Batteries

Rechargeable magnesium batteries have attracted increasing attention due to the high theoretical volumetric capacities, dendrite formation-free characteristic and low cost of Mg metal anodes. However, the development of magnesium batteries is seriously hindered by the lack of capable cathode materials with long cycling life and fast solid-state diffusion kinetics for highly-polarized divalent Mg²⁺ ions. Herein, vanadium tetrasulfide (VS₄) with special one-dimensional atomic-chain structure is reported to be able to serve as a favorable cathode material for high-performance magnesium batteries. Through a surfactant-assisted solution-phase process, sea-urchin-like VS₄ nanodendrites are controllably prepared. Benefiting from the chain-like crystalline structure of VS₄, the S₂ ^2- dimers in the VS₄ nanodendrites provide abundant sites for Mg²⁺ insertion. Moreover, the VS₄ atomic-chains bonded by weak van der Waals forces are beneficial to the diffusion kinetics of Mg²⁺ ions inside the open channels of VS₄. Through a series of systematic ex situ characterizations and density functional theory calculations, the magnesiation/demagnesiation mechanism of VS₄ are elucidated. The VS₄ nanodendrites present remarkable performance for Mg²⁺ storage among existing cathode materials, exhibiting a remarkable initial discharge capacity of 251 mAh g^-1 at 100 mA g^-1 and an impressive long-term cyclability at large current density of 500 mA g^-1 (74 mAh g^-1 after 800 cycles).