Preparation Of Nickel-based Bimetallic Sulfide Composites And Their Capacitive Properties

Supercapacitors have attracted much attention for their low cost,excellent performance,green environment and high working efficiency.Nickel-based metal sulphides are good electrode materials for supercapacitors because of their high electrochemical activity and theoretical capacity,however,nickel-based monometallic sulphide electrode materials are difficult to achieve satisfactory results in terms of electrical conductivity as well as electrochemical performance,and their wide forbidden band width limits the number of electron carriers and their utilization efficiency.The nickel-based bimetallic composites,on the other hand,may produce complementary and synergistic effects on the intrinsic characteristics and obtain more beneficial superelectric properties.Therefore,in this paper,two nickel-based bimetallic sulfide PPy@Fe Ni₂S₄@NF and PPy@Ni Co₂S₄@NF electrode materials based on nickel foam were successfully prepared using a two-step hydrothermal and static method.The composition,microscopic morphology and capacitive properties of the materials were investigated by a series of modern analytical and testing techniques.Details are as follows:（1）The PPy@Fe Ni₂S₄@NF electrode materials were successfully prepared by growing Fe Ni₂S₄nanosheets by hydrothermal method using nickel foam as the substrate,and then encapsulated with PPy materials by static method.The elemental composition and valence distribution of PPy@Fe Ni₂S₄@NF materials were studied by XRD,FT-IR,XPS,SEM and TEM tests,and the nanosheet-type structure of the material core-shell was observed.Electrochemical studies showed that the composite material presented a specific capacitance of 3908.5 F/g at a current density of 1 A/g and a value of 2313.8 F/g at a current density of 10 A/g.The charge transfer resistance of the electrode material,which was about 1.4Ω.The electrode material was repeated for 5000 CP tests at a current density of 10 A/g,and the final specific capacitance was 3181.1 F/g,which is 81.4%of the initial specific capacitance.The prepared materials were assembled as active electrodes with activated carbon to form capacitors with energy density and power density of 47.2 Wh/kg and 699.9 W/kg,respectively.（2）The PPy@Ni Co₂S₄@NF composites were prepared by growing Ni Co₂S₄nanowire arrays on the surface of nickel foam by hydrothermal method,and then coating them with PPy materials by static method.The elemental composition,valence distribution and nanowire structure of the PPy@Ni Co₂S₄@NF materials were characterized by XRD,FT-IR,XPS,SEM,and TEM analysis techniques.Electrochemical studies showed that the specific capacitance of the composite material was 5142.8 F/g at a current density of 1 A/g and 2669.1 F/g at a current density of 10 A/g,and the electrode material had a small charge transfer resistance of about 0.3Ω.The electrode material was repeated for 5000 CP tests at a current density of 10 A/g,and the final specific capacitance was 4783.8 F/g,which was93.0%of the initial specific capacitance.The prepared material was assembled as an active electrode with activated carbon to form a capacitor,which exhibited an energy density of 67.1Wh/kg and a power density of 800.0 W/kg.