Synthesis And Supercapacitor Performance Of Multiple Sulfides With Hierarchical Structure

Along with the rapid development of science and technology, more and more researchers have been showing great interest in high performance electrochemical energy storage devices. Supercapacitor, as a king of electrochemical energy storage devices, has drawn particular attention because of its high energy density, long cycle life and fast charging and discharging. The electrochemical properties of the materials of supercapacitors are determined by materials composition, crystalline morphological and specific area. Thus, controllable syntheses of electrodes with desirable composition and special architecture are expected to have remarkable potential for generating high-performance supercapacitors. In this work, we have successful synthesized a series of new and hierarchical structured multiple sulfide electroactive materials using cobalt coordinated compounds under moderate condition. And these synthesized materials were used as electrode materials for supercapacitor, exhibited excellent and tunable electrochemical performance. The details are summarized briefly as follows:Firstly, single crystal of cobalt coordination compounds were obtained via the reaction of cobalt(II) sulfate with trimesic acid(H3TMA = 1, 3, 5-benzenetricarboxylic acid) by one-pot hydrothermal reaction. Nickel ion exchange was used to produce the Ni–Co hetero-metal compound with tunable chemical composition. Single-crystal to single-crystal transformation has been achieved. Using a nickel-exchanged compound as the precursor, we developed a simple chemical reaction to synthesize large-scale 3D hierarchical NixCo3- xS4(x = 0.15–0.42) microflowers under ambient conditions. The as-synthesized NixCo3-xS4 electrodes for supercapacitors exhibited excellent electrochemical performance and were tuned by adjusting the composition of products. This study provides a new synthetic route for high-performance electrode materials for supercapacitor.Secondly, large-scale, 3D hierarchically structured Co S1.097 microspheres were first fabricated using cobalt coordination compounds as precursors via a simple solvothermal reaction. The p H of the solvent system has been systematically investigated on the final products. In this study, a 3D hierarchically structured Co S1.097 microsphere has been successfully synthesized and used as electrodes for supercapacitors. Experimental results showed that the as-synthesized Co S1.097 electrode materials exhibited low specific capacitance and low rate capability. To obtain high-performance supercapacitor electrodes, a novel strategy to fabricate electrodes for supercapacitors by the synergistic effect of double metal ions is reported. Ni ion, as a helpful cation for supercapacitors, was introduced into Co S1.097 materials to prepare NixCo1-xS1.097(x = 0.10-0.48) electrode materials through different replacement durations and initial concentrations. And the specific capacitance and rate performance of these materials can be continuously enhanced and turned under the synergistic effect of double metal ions. The study provides a valuable reference to fabricate high-performance supercapacitor materials with unique morphology and desirable composition.At last, as well know that ternary sulfides possess higher capacitance and rate capability than an individual metal compound, but the electrochemical performance of these materials still could not satisfy our demand. Sheetlike graphene has been intensively investigated as a backbone to support electrode materials for high-performance supercapacitors because of its large surface area, high mechanical strength, and good electric conductivity. Therefore, 5 wt % reduced graphene oxide(r GO) was added to modify Co S1.097、 Ni0.22Co0.78S1.097、 Ni0.46Co0.54S1.097 and Ni0.48Co0.52S1.097 microflower through a facile hydrothermal reaction. As electrode materials for supercapacitor, the electrochemical performance of the hybrid electrodes was evaluated by CV and galvanostatic charge-discharge techniques. As the electrode materials for supercapacitor, the as-synthesized NixCo1-xS1.097- r GO exhibited enhanced specific capacitance and rate capability than the corresponding sulfide.