Confined growth of uniformly dispersed NiCo2S4 nanoparticles on nitrogen-doped carbon nanofibers for high-performance asymmetric supercapacitors

To pursue high-performance energy storage devices with both high energy density and power density, nitrogen-doped carbon nanofibers (CBC-N) derived from bacterial cellulose are used both as a three-dimensional template for space-confined hydrothermal growth of NiCo2S4, and as the highly conductive negative electrode material for asymmetric supercapacitor assembly. Notably, uniformly dispersed NiCo2S4 nanoparticles with only 3-5 nm are successfully immobilized on the surface of CBC-N fibers to form the CBC-N@NiCo2S4 composite, which effectively prevents the severe aggregation of NiCo2S4 nanoparticles and fully utilizes the outstanding electrochemical activity and capacity of NiCo2S4 as the pseudocapacitive electrode material. Benefiting from the conductive CBC-N fiber template with hierarchical architectures and its coupling with uniformly dispersed NiCo2S4 nanoparticles, the CBCN@NiCo2S4 composite exhibits high capacitance of 1078 F g(-1) at 1 A g(-1) and excellent capacity retention of 94.6% (918.5 F g(-1) at 5 A g(-1)). Furthermore, the asymmetric supercapacitor demonstrates high energy density of 42.6 Wh kg(-1) at power density of 1500 W kg(-1), and long-term cycling stability of 96.8% retention after 5000 cycles. Therefore, this work provides a new strategy to develop biomass-derived highperformance electrode materials for potential applications in supercapacitors. (C) 2017 Elsevier B.V. All rights reserved.