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• The defect-rich VS 4 nanosheets are obtained via microwave-induced fabrication method. • The sulfur vacancies promote the desorption of Mg2+. • V3+ self-doping maintains the structural stability of the active material. • Cation-anionic synergistic redox achieve a high specific capacity. Vanadium sulfide (VS 4) demonstrates the most prospect as the cathode materials for rechargeable magnesium battery due to its special one-dimensional linear crystal structure. However, VS 4 cathode still suffers from sluggish kinetics, irreversible structural change, short cycle life, and low capacity. Herein, a microwave-induced synthesis method is presented to fabricate VS 4 nanosheets with rich sulfur vacancies and high V3+/V4+ ratio. When serviced as the cathode material for rechargeable magnesium battery, the VS 4 nanosheets display excellent electrochemical performances with large specific capacity of 701 mAh/g at 200 mA g−1 current density. In addition, the VS 4 nanosheets cathodes also show long-term operating stability over 600 cycles at 1.0 A/g current density with only 0.3 % capacity decay per cycle. Our experimental results show that the improved electrochemical reaction kinetics is ascribed to the defect-rich structure and the reversible anionic redox reactions between S2−/S 2 2− of the VS 4 nanosheets. This work offers a meaningful way to design high-performance Mg2+ ion storage cathode materials with favorable diffusion kinetics. [ABSTRACT FROM AUTHOR]

The defect-rich unconventional phase Cu 7.2 S 4 Nanotubes are fabricated by a facile microwave-induced selective etching method. Benefitting from the unique one-dimensional crystal structure and lattice defect-rich hollow structure, the Cu 7.2 S 4 nanotubes exhibit high reversible capacity and remarkable cycling stability. [Display omitted] • The defect-rich Cu 7.2 S 4 nanotubes are fabricated for the first time. • The unique microwave-induced selective etching method is demonstrated. • The record cycling stability is achieved over the Cu 7.2 S 4 nanotube cathode. • The multistep reaction kinetics of the Cu 7.2 S 4 nanotube cathode are confirmed. Copper sulfide is promising great potential for capable cathode in rechargeable magnesium batteries. However, divalent Mg2+ diffusion in its host lattice is subject to high lattice strain and mechanical stress mainly due to strong Coulombic interaction. Herein, a microwave-induced selective etching strategy is reported to construct non-stoichiometric-phase robust Cu 7.2 S 4 nanotubes with rich lattice defects, which can proceed with ultra-long-cycling stability over 1600 cycles with ultra-low capacity decay of 0.0109 % per cycle at 1.0 A g−1. Furthermore, the Cu 7.2 S 4 nanotube cathode can also exhibit a large specific capacity of 314 mAh g−1 at 0.1 A g−1 as well as an excellent rate capability of 91.7 mAh g−1 at 1.0 A g−1. The present electrochemical performances greatly surpass those of Cu 7.2 S 4 nanowire, Cu 7.2 S 4 nanoparticle, and conventional phase CuS nanotubes and at least are comparable to the conversion-type cathode materials reported so far. The generated lattice defect combined with the optimized robust nanotube structure can effectively buffer lattice strain and mechanical stress to provide a favorable diffusion kinetic. Our designed microwave-induced selective etching system demonstrates significant superiority in morphology, phase, and defect engineering of Cu 7.2 S 4 nanotubes to accommodate reversible Mg2+ storage for high-performance rechargeable magnesium batteries. [ABSTRACT FROM AUTHOR]