Highly conductive KNiF3@carbon nanotubes composite materials with cross-linked structure for high performance supercapacitor

A series of KNiF3@carbon nanotubes (CNTs) are synthesized via a facile solvothermal method and applied as supercapacitor electrodes. The addition of carbon nanotubes can significantly overcome the rate capability defect of bare KNiF3 and improve the specific capacity to a certain extent, which mainly owing to the increase of conductivity and electron/ion transports capacity. In addition, the cross-linked structure of carbon nanotubes and the evenly anchoring of KNiF3 nanoparticles can increase the stability of the composites. As a result, the optimal candidate KNiF3@CNTs-8 (the content of carbon nanotubes is 8 mg and the mass fraction is 1.0%) shows highest specific capacity (821.4 C g(-1) at 1 A g(-1)) and capacity retention (83.6% at 16 A g(-1)). The asymmetric supercapacitor AC//KNiF3@CNTs-8 delivers extremely high energy density of 63.7 Wh kg(-1). More importantly, the ASC device shows ultra-long cycling stability, with 95.9% capacity retention after 5000 cycles. These results prove that KNiF3@CNTs can be a promising material for supercapacitor.