Search

A method that combines disproportionation and magnesium-vapor-reduction in one step, which is different from traditional magnesium thermal reduction, was designed for synthesizing advanced silicon-based anode materials.

Uncontrollable dendrite growth hinders the direct use of lithium metal anode in batteries even though it has the highest energy density of all anode materials. Li and N atoms have strong interaction and could form Li–N bond, promising for regulating Li-ion flux during the plating/stripping process. Herein, we successfully prepared ultrathin graphitic carbon nitride (g-C3N4) nanosheets with a thickness of ~ 1 nm and formed a g-C3N4 thin layer over the lithium metal anode. The abundant nitrogen species within g-C3N4 nanosheets could form Li–N bonds to powerfully stabilize the lithium-ion flux and enhance the affinity of electrodes with electrolytes. On top of that, the thin layer could act as an artificial solid electrolyte interface (SEI) to suppress lithium dendrite growth and enable stable Li plating/stripping over 350 h at a high current density of 5 mA cm−2 with a low overpotential of about 50 mV. The reported work demonstrates a promising strategy of the functional artificial SEI design for Li metal anodes.

Lithium metal anodes (LMAs) possess the largest energy density among all anode candidates, while dendrite growth is a huge barrier in the direct application of LMAs in batteries. Herein, an ultrathin graphitic C3N4–poly(1,3-dioxolane) (CN–PDOL) composite interlayer was in situ synthesized by cationic ring-opening polymerization upon lithium metal anodes. Flexible PDOL could isolate electrolytes, remitting the corrosion reactions and consumption of electrolytes, while g-C3N4 nanoflakes could reduce the crystallinity of PDOL, increase ion-conductivity and uniform Li-ion fluxes. At a current density of 3 mA cm−2, the synergistic effect of CN and PDOL could enable 850 h stable Li plating/stripping behavior at an overpotential of 70 mV. In this work, a facile and accessible design of a composite buffer layer was developed for lithium metal anodes, which might be of interest to a broad community investigating surface modifications.

In this study, a green and natural biomass waste (pomelo peel) was utilized as eco-friendy and abundantly sustainable precursor to prepare low-cost and valuable porous nitrogen and boron dual-doped carbon aerogel (NB-PPCA). X-ray diffractometer, Raman spectrometer, scanning electron microscope, transmission electron microscope, pore size and surface area analyzer, Fourier transform infrared spectrometer, X-ray photoelectron spectroscopy were exploited to investigate its morphology and microstructure. It was subsequently employed as a coating on pristine separator in lithium sulfur (Li-S) battery. The coating could not only decrease the interface resistance between the cathode and the separator and thus improve the reaction kinetics of the Li-S battery, but also effectively sequester the polysulfides and restrain the “shuttle effect” inside the battery. The cell with coating on separator delivered a high specific capacity of 586.6 mAh g−1 after 500 cycles at 1 C, and it also exhibited good cycle stability and rate performance.

A novel structural hybrid material consisting of La0.5Ca0.5CoO3-δ nanocrystals anchored on reduced graphene oxide is developed as highly efficient bifunctional catalyst for oxygen reduction and evolution reaction in alkaline electrolyte. Nanostructural La0.5Ca0.5CoO3-δ particles, which are synthesized by a modified amorphous citrate precursor method in advance, are anchored homogeneously on the surface of reduced graphene oxide sheets through a simple chemical reduction process at ambient temperature. Although reduced graphene oxide or La0.5Ca0.5CoO3-δ alone possesses some catalytic activity, their hybrid presents a remarkable oxygen reduction catalytic activity, which is on a par with that of the commercial 20 wt% Pt/C. This La0.5Ca0.5CoO3-δ/ reduced graphene oxide hybrid also exhibits outstanding activity for oxygen evolution reaction which surpassed that of IrO2, allowing it to become a highly active non-noble metal bi-catalyst for both oxygen reduction and evolution reaction. More importantly, the same hybrid displays extremely excellent catalytic durability and superior cycling stability to the commercial Pt/C + IrO2 catalyst in the rechargeable zinc-air batteries, becoming one of the most promising bi-catalysts with low-cost. The unexpected bifunctional catalytic activities and surprisingly cycling life arise from synergetic effects between La0.5Ca0.5CoO3-δ and graphene. The rechargeable Zn-air battery with the hybrid as catalyst delivered a large peak power density of 223.6 mW cm−2 along with ultrastbale cyclability over 10,100 min at 5 mA cm−2.

The porous reduced graphene is prepared via an ethylene glycol assisted-hydrothermal method which is green, simple and nontoxic. The ethylene glycol assisted-hydrothermal reduced graphene (EG-RGO) delivers superior power density compared to those prepared without the assistant of ethylene glycol when used as cathode materials for the lithium ion capacitors. The EG-RGO electrode shows a high capacity of 172 mAh g− 1 at 0.1 A g− 1 and without capacity loss after 3000 cycles. Furthermore, the power density of the electrodes reaches 53.5 kW kg− 1 at the current density of 20 A g− 1 with an energy density of 240 Wh kg− 1. The high electrochemical performance of EG-RGO is attributed to the high electronic conductivity of the graphene.

The MnO/graphene hybrid nanocomposites were prepared by an in situ reduction method. The MnO2 nanorods were attached on the graphene oxides (GOs) to form the MnO2/GO nanocomposites, which were reduced to the MnO/graphene hybrid under argon atmosphere. As the anode material for the lithium ion batteries, the MnO/graphene electrodes delivered a high initial charge capacity up to 747 mAh g−1 and a stable capacity of 705.8 mAh g−1 after 100 cycles, which is much superior to pure MnO with initial charge capacity of 456 mAh g−1 and the stable capacity of 95.6 mAh g−1 after 100 cycles. The scanning electron microscope images of the MnO/graphene hybrid nanocomposites after cycling demonstrated that the graphene could prevent the MnO from aggregating during the charge/discharge process.

A facile thermal annealing method is demonstrated to fabricate the MnO 2 nanorods/graphene hybrid. The MnO 2 nanorods are well anchored on the graphene, confirmed by the scanning electron microscopy and transmission electron microscopy images. The hybrid annealed at 300 °C (MG-300) shows a high initial discharge capacity of 241 mAh g −1 at 0.1 C with a graphene loading rate of 9%. In addition, it shows good cycling stability and maintains a capacity of 158.3 mAh g −1 after 100 cycles in the potential window between 2 and 3.5 V. The MG-300 exhibits the best electrochemical performance among all the materials, which is due to the high electronic conductivity of graphene and the MnO 2 nanorods which is consisted of γ-MnO 2 and β-MnO 2 .

Carbon-coated Fe3O4 and pure Fe3O4 nanorods are synthesized via hydrothermal reaction and subsequent sintering procedure. The as-prepared products characterized by X-ray diffraction and scanning electron microscopy analysis indicate that carbon coating does not affect the structure and morphology of Fe3O4. Transmission electron microscope shows that Fe3O4 nanorods are homogeneously coated by carbon layer with a thickness of approximately 2 nm. The electrochemical properties measured by cyclic voltammetry, galvanostatic charge–discharge cycling and electrochemical impedance spectroscopy tests show that carbon-coated Fe3O4 (Fe3O4/C) nanorods present improved electrochemical performance due to the carbon layer. A specific capacitance of 275.9 F g−1 is achieved at a current density of 0.5 A g−1 in 1 M Na2SO3 aqueous solution for the Fe3O4/C nanorods in comparison to that of 208.6 F g−1 for pure Fe3O4.

A series of Co3O4 nanoplates/graphene nanosheets (GNS) composites are fabricated using a facile and green method by hydrothermal treatment and subsequent calcinations in air. The Co3O4 nanoplates with a length of 0.5–1 μm and width of 100–300 nm are homogeneously distributed on the surface of graphene nanosheets which are reduced under mild hydrothermal treatment as investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Electrochemical properties are tested by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The Co3O4 nanoplates/7.0 % GNS composite shows a maximum specific capacitance of 667.9 F g−1 at 1.25 A g−1 and 412.5 F g−1 at 5 A g−1 in 2 M KOH aqueous solution. The composite exhibits excellent cycling stability with 18.7 % of specific capacitance increased after 1,000 cycles.

Well-dispersed nanoporous La0.6Ca0.4CoO3 catalyst for metal–air batteries was synthesized by a modified amorphous citrate precursor method using Vulcan XC-72R as a pore-forming material. Nanostructural perovskite La0.6Ca0.4CoO3 with a specific surface area of over 210 m2/g was obtained at 650 °C in air. The electrochemical behaviors of the as-prepared La0.6Ca0.4CoO3 catalysts were studied on classical bilayer gas diffusion electrodes. Compared with the traditional amorphous citrate precursor method, the perovskite La0.6Ca0.4CoO3 prepared by this modified technique illustrated higher electrocatalytic activity mainly due to the high surface area and the novel nanostructure, which would provide potential applications in metal–air batteries and fuel cells. Keywords: Catalyst preparation, Perovskite La0.6Ca0.4CoO3, Bi-functional electrode

Methylsulfonic acid (MSA) as supporting electrolyte for vanadium redox battery was studied and evaluated by thermal stability test, cyclic voltammetry, linear sweep voltammetry, and charge-discharge technique. The results show that the V(V)-MSA solution has better thermal stability than the sulfuric acid solutions, which may be due to the formation of VO(CH3SO3)2 to prevent further condensation. The diffusion coefficient of V(IV) in MSA can reach up to (0.94–1.52) × 10−6 cm2 s−1, much higher than that in H2SO4 solution (1.40–2.20 × 10−7 cm2 s−1). Polarization curves show the improved reaction kinetics of V(IV)/V(V) in MSA solution, lower charge transfer resistance (5.61 Ω), larger exchange current density (4.57 × 10−3 A cm−2), and rate constant (4.74 × 10−5 cm s−1) compared with the H2SO4 solution. The vanadium redox batteries with the MSA electrolytes demonstrated excellent reversibility and high energy efficiency (83.1%), 2.7% higher than that in H2SO4 solution. The preliminary exploration shows that MSA has a promising application prospect in vanadium redox battery and is worthy for further study.