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Nickel ferrite owns a lot of advantages as electrode materials for supercapacitor, such as high energy density and excellent theoretical capacity. Whereas, the electrochemical performances of NiFe 2 O 4 in terms of rate performance and cycle stability are not satisfactory due to the low conductivity. While carbon fiber is a kind of material with high conductivity. Hence, NiFe 2 O 4 @ slit modified hollow carbon fiber is obtained through the coaxial electrospinning method. The slits on hollow carbon fibers are beneficial to the contact of inner NiFe 2 O 4 nanoparticles with electrolyte. Results of electrochemical tests show that at a current density of 1 A/g, the specific capacitance of NiFe 2 O 4 @ slit modified hollow carbon fiber is calculated to be 225.4 F/g, higher than that of NiFe 2 O 4 nanoparticles of 134.8 F/g. Moreover, a better cycle and rate performances (100 % vs 80 %; 71.9 % vs 47.5 %) are achieved. This work displays that slit modified hollow carbon fiber can improve the electrochemical performance of NiFe 2 O 4 efficiently. [Display omitted] • Carbon fibers are introduced to enhance the rate and cycle performances of NiFe 2 O 4. • Slits are obtained utilizing Al 2 O 3 sacrificial hard templates. • Slits are beneficial to the contact of NiFe 2 O 4 and electrolyte. [ABSTRACT FROM AUTHOR]

• The partial S-doping NiFe 2 O 4 was obtained through a facile hydrothermal method. • The d-spacing of NiFe 2 O 4 was expended caused by partial S-doping. • The impact of partial S-doping to NiFe 2 O 4 is exposed by VASP analysis. • The optimal electrode exhibited the highest specific capacitance of 284 F/g. Nickel ferrite exhibits many advantages as electrode materials in the application of supercapacitor, such as high energy capacity and excellent cycle stability. Whereas, compared with identical-metal sulfides, the specific capacitance of NiFe 2 O 4 is still insufficient. Hence, to combine the superiorities of oxides and sulfides, partial sulfur doping NiFe 2 O 4 is obtained through hydrothermal synthesis method. Analyzed by Vienna Ab-initio Simulation Package (VASP) software and high-resolution transmission electron microscopy, the lattice parameters of NiFe 2 O 4 are confirmed to be expanded by introducing sulfur atoms, which is beneficial to electrochemical performances. At a current density of 1 A/g, the specific capacitance of partial sulfur doping NiFe 2 O 4 is calculated to be 284 F/g, higher than that of the original NiFe 2 O 4 of 182.2 F/g. Moreover, a maximum energy density of 21.14 Wh/kg is achieved at a power density of 375 W/kg. This work shows that partial sulfur doping could improve the electrochemical performance of NiFe 2 O 4. To sum up, this work provides an effective way to enhance the poor electrochemical performance of oxides, greatly encouraging the application of oxides in energy storage field. [Display omitted] [ABSTRACT FROM AUTHOR]