ZIF-8/ZIF-67-derived 3D amorphous carbon-encapsulated CoS/NCNTs supported on CoS-coated carbon nanofibers as an advanced potassium-ion battery anode

Although three-dimensional structural carbon network materials have shown good performance in potassium ion batteries (KIBs), they are intertwined and consist of one-dimensional carbon nanotubes or graphitic carbon. In this work, we report a novel integrated 3D amorphous carbon-encapsulated CoS/nitrogen-doped carbon nanotube/CoS-coated carbon nanofiber (AC@CoS/NCNTs/CoS@CNFs) network comprising independent 3D hierarchical structure units. The unique 3D ordered electrode bracket design reduces the ion diffusion path and improves the electronic conductivity and mechanical stability; in addition, the CoS nanoparticles participate in K+ insertion/extraction, which is advantageous for high-performance energy storage. Specifically, the AC@CoS/NCNTs/CoS@CNFs network is further evaluated as an anode for KIBs, delivering a capacity of 401 mA h g(-1) at 0.1 A g(-1) after 100 cycles with outstanding rate capabilities, which is better than that of other MOF-based anode materials for KIBs reported previously. In addition, the capacity is maintained at 130 mA h g(-1) at 3.2 A g(-1) after 600 cycles with excellent cycling stability. Thus, this work opens a new direction for the fabrication of 3D structured anodes for alkali metal ion battery applications.