Composition controlled nickel cobalt sulfide core– shell structures as high capacity and good ratecapability electrodes for hybrid supercapacitors
writer：Lei Zhang, Haitao Zhang*, Long Jin, Binbin Zhang, Fangyan Liu, Hai Su, Fengjun Chun, Qinghan Li, Jin
keywords：,
source：期刊
Issue time：2016年
Herein, we report a type of core–shell structured NixCo361xS4 (x = 1, 1.5 and 2) through tuning the ratios of Ni to Co by a simple two-step hydrothermal method. Scanning electron microscopy and transmission electron microscopy images of all the Ni–Co sulfides show high porosity and uniform spherical morphology. Moreover, this study demonstrates that controlling the appropriate ratio of Ni to Co in the core–shell structure is crucial for improving the electrochemical performance in a hybrid supercapacitor. Among them, NiCo2S4 with core–shell structure possesses the highest capacity of 155 mA h g611, whereas as Ni1.5Co1.5S4 shows the excellent rate-capability of up to 80% from 1 to 20 A g611 and cycling stability, which retains 74% after 2000 cycles. Therefore, tuning the metal element contents provides a feasible approach to achieving the desired high-rate performance and cycling stability of electrode materials in polynary metal sulfides for hybrid supercapacitors.