Wei-Bin Zhang

Facile fabrication and perfect cycle stability of 3D NiO@CoMoO4 nanocomposite on Ni foam for supercapacitors

An advanced binder-free electrode for high-performance supercapacitors has been designed by growing a three-dimensional (3D) NiO@CoMoO4 nanocomposite on Ni foam. Such a unique nanocomposite combined separately the advantages of the perfect cycling stability and rate capability of CoMoO4 and the high specific capacitance of NiO. Furthermore, the nanostructure of NiO@CoMoO4 could serve as an “ion reservoir” to store ions of the electrolyte, and give it a higher specific surface area and more active sites. As a result, this electrode exhibited remarkable specific capacitances (848 F g−1 at a current density of 0.5 A g−1), perfect cycle stability (100% of cycle efficiency after 3000 cycles) and excellent electrochemical performance compared to single oxide electrodes. And this work also demonstrates the feasibility of rational design of advanced integrated nanocomposite electrodes for high-performance supercapacitors.

Nickel vanadate and nickel oxide nanohybrid on nickel foam as pseudocapacitive electrodes for electrochemical capacitors

A novel self-supported electrode of nickel vanadate and nickel oxide nanohybrid on nickel foam with excellent pseudocapacitive properties was synthesized using a combination of a hydrothermal strategy and subsequent annealing treatment. The porous nanostructure not only provides a larger surface area for faradic reactions, but also allows the rapid transportation of electrolyte ions for improving rate capability. The electrode demonstrates outstanding capacitance, satisfying rate capability and good cycling stability, showing the coupling effects of nickel vanadate and nickel oxide. In this case, the electrode has an energy density of 46 W h kg−1 at a power density of 101 W kg−1, demonstrating the importance and great potential of nickel vanadate in the development of energy storage systems.

VO2: from negative electrode material to symmetric electrochemical capacitor

A novel negative electrode material of 3D irregular ellipsoidal VO2 with excellent pseudocapacitive properties is synthesized via a simple heat treatment method. The structural analysis and morphological features show the stable morphological basis of this material, which can favor electron transportation and electroactive species diffusion. The VO2 displays an excellent specific capacitance of 548 F g−1 at a current density of 0.5 A g−1, a wide potential window of −1.0 V to 1.0 V, an excellent energy density of 194.8 W h kg−1 at a power density of 400.5 W kg−1, and a rapidly reversible redox Faraday response. In addition, a VO2//VO2 symmetric supercapacitor has been assembled with a high potential window of 1.6 V, higher than traditional carbon-based cells. As a result, the VO2//VO2 symmetric supercapacitor can deliver a specific capacitance of 60 F g−1 at a current density of 0.25 A g−1 with a good energy density (21.3 W h kg−1 at a power density of 207.2 W kg−1) and stable power characteristics, which demonstrate the excellent performance of the VO2//VO2 symmetric supercapacitor and the great potential of using a VO2 electrode as the negative and/or positive electrodes for supercapacitors with a high comprehensive performance.

NiMoO4-modified MnO2 hybrid nanostructures on nickel foam: electrochemical performance and supercapacitor applications

A novel self-supported electrode of NiMoO4-modified MnO2 hybrid nanostructures on nickel foam has been designed and synthesized using a combination of hydrothermal syntheses. Based on the morphology, a possible mechanism that the surface modification of NiMoO4 not only prevents the MnO2 from dissolving in an alkaline electrolyte of KOH but also improves the capacity is proposed. Therefore, this electrode manifests a satisfying capacitance of 2525 F g−1 (within a potential range of −0.2–0.6 V at a current density of 0.5 A g−1), outstanding rate capability and excellent cycling stability. The reason that the hybrid NiMoO4-modified MnO2 electrode has excellent comprehensive performance is not only the coupling effect which between NiMoO4 and MnO2 but also the semiconductor surface recombination effect which improved the electrical conductivity. Moreover, an asymmetric supercapacitor has been assembled, where the hybrid NiMoO4-modified MnO2 and activated carbon act as the positive and negative electrodes, respectively, and a maximum specific capacitance of 135 F g−1 is demonstrated within a cell voltage between 0 and 1.6 V at a current density of 0.5 A g−1; thus, the supercapacitor exhibits a high energy density and stable power characteristics.

Fabrication of 3D Co3O4–Ni3(VO4)2 heterostructured nanorods on nickel foam possessing improved electrochemical properties for supercapacitor electrodes

Three-dimensional (3D) Co3O4–Ni3(VO4)2 heterostructured nanorods on nickel foam with excellent electrochemical behavior were synthesized by a facile strategy. A growth mechanism was proposed to explain the formation of the composite. The composite combined separately the advantages of the good rate capability of Co3O4 and the high specific capacitances of Ni3(VO4)2, and showed higher specific capacitances than Co3O4 and better rate capability than Ni3(VO4)2. A maximum specific capacitance of 1401 F g−1 and energy density of 31.2 Wh kg−1 were achieved at a current density of 0.5 A g−1, and 70.3% of this value was retained at a high current density of 8 A g−1. After 1000 cycles, 98.3% and 90.9% was retained at 0.5 A g−1 and 8 A g−1, respectively. The excellent electrochemical performance renders the composite a promising electrode for supercapacitors.

Electrochemical performance in alkaline and neutral electrolytes of a manganese phosphate material possessing a broad potential window

An underlying electrode material of manganese phosphate has been designed and synthesized, possessing wide potential windows (−0.9–0.7 V in neutral and −0.5–0.6 V in alkaline electrolyte), satisfying specific capacitances (203 F g−1 in neutral and 194 F g−1 in alkaline electrolyte), outstanding rate capabilities and excellent cycling stabilities. The morphological characteristics and electrochemical analyses indicate that the layered crystal structure offers many nano-paths and improves the diffusion of electrolyte ions, which can noticeably promote electrochemical performance. Furthermore, a Mn3(PO4)2//AC asymmetric supercapacitor and a Mn3(PO4)2//Mn3(PO4)2 symmetric supercapacitor have been assembled at a cell voltage between 0 and 1.6 V, and exhibit excellent electrochemical stabilities and stable energy and power characteristics, which reveal that this manganese phosphate material is promising for electrochemical energy storage applications.

Design and synthesis of one-dimensional Co3O4/Co3V2O8 hybrid nanowires with improved Li-storage properties

A new nanostructure of one-dimensional Co3O4/Co3V2O8 hybrid nanowires directly grown on Ti substrates with improved electrochemical Li-storage properties are successfully prepared by a simple hydrothermal strategy. The nanocomposites consist of the primary Co3O4 nanowires acting as the “core” and secondary Co3V2O8 nanocrystals as the “shell” layer, which form one-dimensional tentacle-like nanostructure. When used as potential anodes for lithium ion batteries, the Co3O4/Co3V2O8 hybrid nanowires exhibited an enhanced capacity with high initial discharge capacity of 1677 mA h g−1 at 200 mA g−1 and retained at 1251 mA h g−1 after 200 cycles. Even when the current reached 5000 mA g−1 the electrode can still maintain an average discharge capacity of 807 mA h g−1. The enhanced electrochemical performances are attributed to unique hybrid nanowire architecture and an improved synergistic effect of two electrochemically component, ranking the hybrid nanostructure as a promising electrode material for high-performance energy storage systems.

Solid-phase synthesis and electrochemical pseudo-capacitance of nitrogen-atom interstitial compound Co3N

Metal nitrides have great potential for electrochemical energy storage, but are relatively scarcely investigated. Herein, a novel metal nitride, Co3N, is prepared by nitridation using a Co3O4 precursor heated at 500 °C for 2 h in flowing NH3, and characterized by using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy dispersive spectroscopy (EDS) methods. Besides, the electrochemical properties of Co3N are investigated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). The as-prepared Co3N demonstrates remarkable electrochemical performance with a high specific capacitance of 112.3 F g−1 at a current density of 0.5 A g−1, good rate capability (72.4%, from 0.5 to 5 A g−1) and superior cycling stability (109.7% retention over 10 000 cycles at a current density of 2 A g−1). Finally, a Co3N//activated carbon (AC) asymmetric supercapacitor (ASC) is successfully assembled by using Co3N and AC as the positive electrode and negative electrode, respectively. The as-fabricated ASC device can achieve a maximum energy density of 12.1 W h kg−1 at a power density of 204.6 W kg−1, which shows that the Co3N material should be a potential electrode material for supercapacitors.

Nitrogen-doped micro-nano carbon spheres with multi-scale pore structure obtained from interpenetrating polymer networks for electrochemical capacitors

A chemical process was developed to prepare N-doped micro-nano carbon spheres with multi-scale pore structures via carbonization of N-PF/PMMA interpenetrating polymer networks, which contain melamine resin as the nitrogen source, PF as the carbon source, and polymethylmethacrylate (PMMA) as the pore-former. The N-content of N-doped micro-nano carbon spheres was controlled by adjusting the mass ratio of melamine and phenol before polymerization. The N-doped micro-nano carbon spheres as electrode materials possess appropriate pore size distribution, higher specific surface area (559 m2 g−1) and consistently dispersed nitrogen atoms with adjustable doping content. These distinct characteristics endow the prospective electrode materials with excellent performance in electrochemical capacitors. In particular, N-CS-IPN-4 exhibits the highest specific capacitance of 364 F g−1 at 0.5 A g−1 in 6 M KOH aqueous electrolyte in a three-electrode system. It also possesses superior rate capability (57.7% retention at current densities ranging from 0.5 to 50 A g−1) and excellent cycling performance at 2 A g−1 (100% retention after 10 000 cycles). All these results confirm that the N-doped micro-nano carbon spheres are promising electrochemical capacitor materials, which possesses the advantages of simple preparation procedure, multi-scale pore structures, higher specific surface areas, easy adjustment of N-content and excellent electrochemical properties.

Coprecipitation Reaction System Synthesis and Lithium-Ion Capacitor Energy Storage Application of the Porous Structural Bimetallic Sulfide CoMoS4 Nanoparticles

Lithium-ion capacitors (LICs) are noticed as a new-type of energy storage device with both capacitive mechanism and battery mechanism. The LICs own outstanding power density and energy density. In our work, an LIC was constructed by using a simple method to prepare a bimetallic sulfide of CoMoS4 nanoparticles as the anode and a self-made biochar [fructus cannabis’s shells (FCS)] with excellent specific surface area as the cathode. The CoMoS4//FCS LIC demonstrated that the range of energy density is from 10 to 41.9 W h/kg and the range of power density is from 75 to 3000 W/kg in the meantime, and it also demonstrated a remarkable cycling performance with the capacitance retention of 95% after 10 000 cycles of charging–discharging at 1 A/g. The designed CoMoS4//FCS LIC device exhibits a superior electrochemical performance because of the CoMoS4 loose porous structure leading to excellent dynamic performance, which is conducive to the diffusion of electrolyte and lithium ion transport, and good electric double layer performance of biochar with large specific surface area could be achieved. Therefore, this bimetallic sulfide is a promising active material for LICs, which could be applied to electric vehicles in the future.