Copper sulfides are broadly explored as the possible cathode materials for rechargeable magnesium batteries on account of their high theoretical capacity of 560 mAh g–1. However, the CuS cathodes usually suffer from serious capacity decay caused by structure collapse during the repeated magnesiation/demagnesiation process. Herein, we present a cuprous self-doping strategy to synthesize mesoporous CuS nanotubes with robust structural stability for rechargeable magnesium batteries and regulate their electrochemical magnesium storage behavior. Electrochemical results show that the mesoporous CuS nanotubes can exhibit high specific capacity, remarkable cycling performance, and good rate capability. The observed discharge capacity of the mesoporous CuS nanotubes could reach about 281.2 mAh g–1 at 20 mA g–1 and 168.9 mAh g–1 at 500 mA g–1. Furthermore, a remarkable ultralong-term cyclic stability with a reversible capacity of 72.5 mAh g–1 at 1 A g–1 is obtained after 550 cycles. These results demonstrate that the mesoporous nanotube structure and the simple cuprous self-doping effect could promote the practical application of copper sulfide cathode materials for rechargeable magnesium batteries.

Sheet-assembled hollow CuSe nanocubes are fabricated by a facile template-directed selenation method and exhibit record rate capability among the chalcogenide compounds reported so far.

Copper chalcogenides are of great interest as conversion-type cathode materials due to their large specific capacity for rechargeable magnesium batteries, yet are subjected to severe capacity fading brought about by structure collapse in repetitive charge-discharge cycling. Herein, single-crystalline and (110) preferentially oriented CuSe nanoflakes are designed via a temperaturecontrolled crystal growth route under microwave irradiation. The as-prepared CuSe nanoflake cathode materials can present high reversible capacity (204 mAh g −1 at 200 mA g −1 current density), outstanding rate capability, and remarkable long-term cycling stability (≈0.095% capacity decay per cycle at 1 A g −1 within 700 cycles). The multistep reversible conversion mechanism of the CuSe nanoflake cathode materials is evidenced by ex situ X-ray photoelectron spectroscopy and X-ray diffraction. Structure evolution investigation suggests that the single-crystalline CuSe nanoflakes can exhibit relatively durable structural stability. The desirable cycling stability can be ascribed to the excellent pulverization-tolerance of the CuSe nanoflake cathode materials endowed by the multistep reversible conversion mechanism and the single-crystalline feature. Furthermore, the preferentially-oriented (110) active plane is favorable for electrochemical reactions to ensure high specific capacity. This work can afford a crystal engineering strategy to fabricate high-performance conversion-type electrode materials for rechargeable magnesium batteries.

The weak van der Waals interactions of the one-dimensional (1D) chainlike VS4 crystal structure can enable fast charge-transfer kinetics in metal ion batteries, but its potential has been rarely exploited in depth. Herein, a thermodynamics-driven morphology manipulation strategy is reported to tailor VS4 nanosheets into 3D hierarchical self-assembled architectures including nanospheres, hollow nanospheres, and nanoflowers. The ultrathin VS4 nanosheets are generated via 2D anisotropic growth by the strong driving force of coordination interaction from ammonium ions under microwave irradiation and then evolve into 3D sheet-assembled configurations by adjusting the thermodynamic factors of temperature and reaction time. The as-synthesized VS4 nanomaterials present good electrochemical performances as the anode materials for sodium-ion batteries. In particular, the hollow VS4 nanospheres show a specific capacity of 1226.7 mAh g–1 at 200 mA g–1 current density after 100 cycles. The hierarchical nanostructures with large specific surface area and structural stability can overcome the difficulty of sodium ions embedding into the bulk material interior and provide more reactive materials at the same material mass loading compared with other morphologies. Both experiment and DFT calculations suggest that VS4 nanosheets reduce reaction kinetic impediment of sodium ion in battery operating. This work demonstrates a way of the morphological design of 2D VS4 nanosheets and application in sodium ion storage.

The conversion-type copper chalcogenide cathode materials hold great promise for realizing the competitive advantages of rechargeable magnesium batteries among next-generation energy storage technologies; yet, they suffer from sluggish kinetics and low redox reversibility due to large Coulombic resistance and ionic polarization of Mg 2+ ions. Here we present an anionic Te-substitution strategy to promote the reversible Cu 0 /Cu + redox reaction in Te-substituted CuS 1−x Te x nanosheet cathodes. X-ray absorption fine structure analysis demonstrates that Te dopants occupy the anionic sites of sulfur atoms and result in an improved oxidation state of the Cu species. The kinetically favored CuS 1−x Te x (x = 0.04) nanosheets deliver a specific capacity of 446 mAh g −1 under a 20 mA g −1 current density and a good long-life cycling stability upon 1500 repeated cycles with a capacity decay rate of 0.0345% per cycle at 1 A g −1 . Furthermore, the CuS 1−x Te x (x = 0.04) nanosheets can also exhibit an enhanced rate capability with a reversible specific capacity of 100 mAh g −1 even under a high current density of 1 A g −1 . All the obtained electrochemical characteristics of CuS 1−x Te x nanosheets significantly exceed those of pristine CuS nanosheets, which can contribute to the improved redox reversibility and favorable kinetics of CuS 1−x Te x nanosheets. Therefore, anionic Te-substitution demonstrates a route for purposeful cathode chemistry regulation in rechargeable magnesium batteries.