Constructing defect-rich unconventional phase Cu7.2S4 nanotubes via microwave-induced selective etching for ultra-stable rechargeable magnesium batteries

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 Cu7.2S4 nanotubes with rich lattice defects, which can proceed with ultra-longcycling stability over 1600 cycles with ultra-low capacity decay of 0.0109 % per cycle at 1.0 A g(-1). Furthermore, the Cu7.2S4 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 Cu7.2S4 nanowire, Cu7.2S4 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 Cu7.2S4 nanotubes to accommodate reversible Mg2+ storage for high-performance rechargeable magnesium batteries.