Synthesis Of Polypyrrole/nickel-based Composites And Their Performance In Supercapacitors

Supercapacitor plays an important role in high-performance driving power source because of its super capacity,fast charging/discharging efficiency,high power density and so on.At present,a variety of electrochemical active materials including carbon materials,conductive polymers and metal complexes are widely used as electrode materials for supercapacitors.However,a single electrode material usually has inherent defects such as low energy density and poor electrochemical performance.Researches shows that composite electrode materials made from different materials can take into account the characteristics of various materials simultaneously,and show excellent electrochemical performance than single material.In particular,the nanocomposites constructed by metal oxide and conducting polymer can have the high theoretical capacitance of pseudopotential material and high conductivity of polymers at the same time,and exhibit high electrochemical performance under unique structural characteristics.Therefore in this paper,the new type of composites with unique structure were designed and synthesized based on nickel-based material?cobalt nickel sulfide,nickel molybdate?and polypyrrole,and their electrochemical properties were studied.The specific contents are as follows:The core-shell composites of the Ppy nanotube surface modified by NiCo₂S₄nanoflakes were prepared by the environment-friendly hydrothermal method.The introduction of Ppy NTs as the skeleton effectively prevented the aggregation of NiCo₂S₄ nanoflakes,and caused a specific surface area of up to 217 m² g^-1.Electrochemical tests show that the composite has a high specific capacitance up to908.1 F g^-1 under 1 A g^-1 and cycle stability up to 87.7%after 2000 cycles,showing more excellent electrochemical performance than that of pure NiCo2S4.In addition,asymmetric supercapacitor equipment composed of Ppy@Ni Co₂S₄ composite as positive electrode possess a power density up to 50.82 Wh kg^-1 with a high power density of 160 W kg^-1 and cycling stability up to 126.6%after 2000 cycles.Because of its excellent electrochemical performance,Ppy@NiCo₂S₄ composites are considered to be ideal candidates for high-performance supercapacitors.Based on the Ppy tubes,the Ppy@NiMoO₄ tubular composites were synthesized through a simple hydrothermal treatment,showing excellent electrochemical performance than that of pure NiMoO₄.Then rGO/Ppy@NiMoO₄ three-dimensional conductive films were constructed by introducing the two-dimensional rGO.Under the different doping ratio of rGO,the capacitance of rGO/Ppy@NiMoO₄ with mixing 2%,5%and 15%of rGO is higher than that of the pure composite Ppy@NiMoO₄ without rGO.In particular,the specific capacitance of rGO/Ppy@NiMoO₄-2%is up to 1125.2F g^-1 with 1 A g^-1.With the increase of the amount for r GO doping,the capacitance performance of rGO/Ppy@NiMoO₄ gradually decreased.In the case of the film electrode successfully made by vacuum filtration,all-solid-state symmetric supercapacitors were assembled by using the rGO/Ppy@NiMoO₄-5%film as positive and negative electrode.The preparation of this film provides a new synthetic route with convenient and low cost for flexible electrode material and all-solid-state supercapacitor.