Direct growth of mesoporous carbon-coated Ni nanoparticles on carbon fibers for flexible supercapacitors†
We demonstrated a facile solution method for direct growth of mesoporous carbon-coated nickel nanoparticles on conductive carbon blacks (CCBs) treated carbon fibers (CFs), using an oleate-assisted deposition/calcinations process. The obtained composite has a uniform Ni core of ∼5 to 10 nm, and a carbon surface layer of ∼2 nm, which avoids aggregation and pulverization of inner nanoparticles and serves as a protective layer of Ni cores from dissolution during electrochemical reactions. In addition, the oleate decomposition during calcination leads to the formation of mesopores, which enable sufficient interaction between electrolyte and inner active materials and provides a high surface area of 71 m2 g−1 for electrochemical reaction and efficient pathways for electrolyte diffusion. Moreover, the introduction of conductive carbon blacks to carbon fibers substrate significantly reduces the internal resistance and leads to enhanced electrochemical properties. These mesoporous carbon-coated nickel nanoparticles show a high capacitance of ∼700 F g−1 at 1 A g−1 current density. The excellent cycling stability over repeated folding cycles for single electrodes and the mechanical stability of different twisted and bent states for solid-state active carbon (AC)//Ni@C asymmetric supercapacitors (ASCs) suggest they are potential candidates for flexible energy storage.