ZnFe2O4 nanoparticles-cotton derived hierarchical porous active carbon fibers for high rate-capability supercapacitor electrodes

ZnFe2O4 (ZFO) has attracted considerable attention for supercapacitors (SCs), but its performances are severely hindered by intrinsically low electronic conductivity, relatively low mechanical stability, and severe agglomeration during the charge-discharge process. Here, a novel cotton derived active carbon fiber (ACF) with hierarchical porous architecture is used as template/scaffold, ZnFe2O4 nanoparticles/active carbon fiber composites (ZFO-ACFs) are prepared, in which ZFO nanoparticles (∼20 nm) are confined into the larger nanopores (∼20 nm) of the cotton derived active carbon fiber (ACF) while the smaller nanopores (∼2.5 nm) still are preserved. The cotton derived ACF matrix not only controls the size of ZFO particles and avoids self-aggregation but also offers continuous electron pathway and rapid ion transport channel, and prevents the loss of active material (ZFO) during the electrochemical reaction. The ZFO-ACFs electrode exhibits high specific capacitance of 192 F g−1 (58.7 mAh g−1). Moreover, enhanced rate capability are also obtained.