High performance flexible energy storage device based on copper foam supported NiMoO4 nanosheets-CNTs-CuO nanowires composites with core-shell holey nanostructure

Because of the intensified electrochemical activities,mixed metal oxides as a representative for pseudo-capacitive materials play a key role for high performance supercapacitor electrodes.Nevertheless,low ion and electron transfer rate and poor cycling performance in the electrode practically restrict further promotion of their electrochemical performance.In order to offset the defect,a novel copper(Cu)foam-supported nickel molybdate nanosheet decorated carbon nanotube wrapped copper oxide nanowire array(NiMoO4 NSs-CNTs-CuO NWAs/Cu foam)flexible electrode is constructed.The as-prepared elec-trode demonstrates a unique core-shell holey nanostructure with a large active surface area,which can provide a large number of active sites for redox reactions.Besides,the CNTs networks supply improved conductivity,which can hasten electron transport Through this simple and efficient design method,the spatial distribution of each component in the flexible electrode is more orderly,short and fast electron transport path with low intrinsic resistance.As a result,the NiMoO4 NSs-CNTs-CuO NWAs/Cu foam as an adhesiveless supercapacitor electrode material exhibits excellent energy storage performance with high specific areal capacitance of 23.40 F cm-2 at a current density of 2 mA cm-2,which outperforms most of the flexible electrodes reported recently.The assembled asymmetric supercapacitor demonstrates an energy density up to 96.40 mW h cm-3 and a power density up to 0.4 W cm-3 under a working voltage window of 1.7 V.In addition,outstanding flexibility of up to 100° bend and good cycling stability with the capacitance retention of 82.53％after 10,000 cycles can be obtained.     

Supercapacitive behaviors and their temperature dependence of sol–gel synthesized nanostructured manganese dioxide in lithium hydroxide electrolyte

In the present work, a nanostructured manganese dioxide material was synthesized by a sol–gel method starting with manganese acetate (MnAc₂·4H₂O) and citric acid (C₆H₈O₇·H₂O) raw materials, and characterized by X-ray diffraction, infrared spectroscopic and transmission electron microscope techniques. The electrochemical properties and the influence of temperature on supercapacitive behaviors of the nano-MnO₂ electrode in 1 M LiOH electrolyte were investigated using electrochemical methods. Experimental results show that the MnO₂ electrode can exhibit an excellent pseudocapacitive behavior in 1 M LiOH electrolyte, and a high specific capacitance of 317 F g⁻¹ can be obtained at a charge/discharge current rate of 100 mA g⁻¹ and at the temperature of 25 °C. We found that temperature has a crucial influence on the discharge specific capacitance of the electrode. The specific capacitance at 25 °C is higher than that at 15 or 35 °C.     

NiO-based composite electrode with RuO2 for electrochemical capacitors

NiO/RuO₂ composite materials were prepared for use in electrochemical capacitors (ECs) by co-precipitation method followed by heat treatment. X-ray diffraction (XRD) spectra indicated that no new structural materials were formed and ruthenium oxide particles were coated by NiO particles. RuO₂ partly introduced into NiO-based electrode had improved its electrochemical performance and capacitive properties by using electrochemical measurements. A maximum specific capacitance of 210 F/g was obtained for NiO-based composite electrode with 10 wt.% RuO₂ in the voltage range from −0.4 to 0.5 V in 1 mol/l KOH solution. By comparison of effect of modified modes on the specific capacitance, chemically modified composite electrodes had more stable cycling properties than those of physically modified electrodes. After 200 cycles, specific capacitance of NiO-based chemical composite electrode with 5 wt.% RuO₂ kept 95% above, while that of physical electrode was only 79% of initial specific capacitance.     

Facile synthesis of pseudocapacitive Mn3O4 nanoparticles for high-performance supercapacitor

In this work, a facile method to produce the ultrafine (4–14 nm) and mixed valence Mn₃O₄ nanoparticles from low-cost MnSiO₃ (manganese silicate) particles were introduced. The best NaOH concentration in hydrothermal treatment has been determined after a series of experiments. Also, the as-synthesized Mn₃O₄ material with good specific capacitance has been investigated attentively at a high mass loading (∼3 mg cm⁻²). The particles size and the pore size distribution is found to be refined and optimized, respectively. This increased the crystallinity and the capacitive contribution in the energy process. Thereby improving the rate capability and cycling stability, which result in significant improvement of specific capacitance (401 F g⁻¹ at 10 mV s⁻¹). The aqueous asymmetric supercapacitor device AC//Mn₃O₄ with a stable working voltage window up to 2.0 V has been fabricated, and it is found to have an energy density of 40.2 W h kg⁻¹ at 500 W kg⁻¹ power density. This could sustain 5000 cycles galvanostatic charge/discharge with 96.9% retention.