Co0.85Se hollow polyhedrons entangled by carbon nanotubes as a high-performance cathode for magnesium secondary batteries

Magnesium secondary batteries are suitable for large-scale applications owing to the low cost and dendrite-free features of the magnesium metal anode. Currently, exploration of high-performance cathodes is the main challenge of magnesium batteries, and rational structure design strategies are the cores of cathode material development. In the present study, a new approach is introduced combining hollow structure and conductive framework. ZIF-67 derived Co0.85Se hollow polyhedrons entangled by carbon nanotubes (Co0.85Se/CNTs) are fabricated and investigated as rechargeable magnesium battery cathodes. The hollow structure facilitates Mg2+ transportation and the CNT framework favors electron conduction, constructing active nanodomains for highly reversible magnesium storage reactions. Co0.85Se/CNTs shows a high capacity of 194 mAh g(-1) and a superior rate capability providing 95 mAh g(-1) at 1000 mA g(-1). Prominently, the rigid CNTs enhance the stability of the Co0.85Se/CNTs composite and improve the cyclability. A 76% capacity retention is maintained after 500 cycles at 200 mA g(-1), corresponding to a decay of 0.048% per cycle. This work highlights a micro-nanostructure favoring magnesium storage reaction reversibility and cyclability, which would enlighten rational electrode design for the storage of magnesium cations.

Automated summary

This study presents a new approach combining hollow structure and conductive framework in rechargeable magnesium battery cathodes, demonstrating high capacity and rate performance. The Co0.85Se hollow polyhedrons entangled by carbon nanotubes provide active nanodomains for highly reversible magnesium storage reactions, while also enhancing stability.