Melamine (MA) has some desirable functional groups convertible into solid electrolytes with enhanced ionic conductivity. Herein, a simple hydrothermal method is adopted to modify Li₂ZnTi₃O₈ (LZTO) with MA for optimizing the electrochemical behaviors. After hydrothermally heating at 200 °C for 12 hours, the modified products demonstrate excellent cycle stability, outstanding capacity performance and alleviated polarization. At a mass ratio of 1:0.05 for LZTO to melamine, the product reveals superior Li-ion diffusion, low impedance, and optimal rate performance (denoting capacities of 202.4, 196.3, 182.3, 174.4 and 165.3 mAh g-1 at 0.1, 0.2, 0.4, 0.8 and 1.6 A g-1). Combined the performance with structure and composition, the MA coating layer gradually evolves into solid electrolytes of Li₃N and LiNxOy with high ionic conductivity during lithiation, meanwhile the oxygen vacancies introduced in LZTO accompanied with the occurrence of LiNxOy facilitate electron and ion conductance, thus responsible for the promoted electrochemical performance of LZTO.
β‐SiC nanowires were synthesized at a temperature as low as 150°C by the reaction of Si and graphite induced by an additional reaction between Na and S. Characterization by X‐ray diffraction, high‐resolution transmission electron microscopy, IR spectra, and Raman spectra demonstrates the formation of curly β‐SiC nanowires with several millimeters in length and 50–70 nm in diameter. Also, a prominent peak at 387 nm is observed in the visible photoluminescence emission. Besides the temperature, the molar ratio of S to Si (or graphite) has significant influence on the synthesis of SiC at relatively low temperatures.
Hollow carbon spheres (HCSs) and HCS/ZnO@C composite are synthesized by the reaction of zinc with sucrose and glycerol, respectively. The electromagnetic parameters of the HCSs and HCS/ZnO@C composite are measured by a coaxial line method. Both the real and imaginary complex permittivities and the loss tangent for the HCS/ZnO@C composite are larger than those for the HCSs. The electromagnetic absorption properties of the HCS/ZnO@C composite are advantageous over those of the HCSs, not only in band width but also in absorber thickness.
Carbon spheres were rapidly synthesized at low temperature (300 °C) via the chemical metathesis reaction between CaC2, C2Cl4, and CCl4. X-ray diffraction and Raman results confirm the formation of hexagonal graphite with relatively low graphitization. Large quantities of carbon spheres can be observed by transmission electron microscopy in the products obtained within the reaction temperature range of 300−480 °C. The spheres with a surface area of 195.28 m2/g have a hydrogen storage capacity of 3.8 wt % at room temperature under a pressure about 10 MPa. The synergic carbon sources are likely responsible for the formation of the carbon spheres.
We develop a facile synthesis route to prepare Cu doped hollow structured manganese oxide mesocrystals with controlled phase structure and morphology using manganese carbonate as the reactant template. It is shown that Cu dopant is homogeneously distributed among the hollow manganese oxide microspherical samples, and it is embedded in the lattice of manganese oxide by substituting Mn(3+) in the presence of Cu(2+). The crystal structure of manganese oxide products can be modulated to bixbyite Mn2O3 and tetragonal Mn3O4 in the presence of annealing gas of air and nitrogen, respectively. The incorporation of Cu into Mn2O3 and Mn3O4 induces a great microstructure evolution from core-shell structure for pure Mn2O3 and Mn3O4 samples to hollow porous spherical Cu-doped Mn2O3 and Mn3O4 samples with a larger surface area, respectively. The Cu-doped hollow spherical Mn2O3 sample displays a higher specific capacity of 642 mAhg(-1) at a current density of 100 mA g(-1) after 100 cycles, which is about 1.78 times improvement compared to that of 361 mA h g(-1) for the pure Mn2O3 sample, displaying a Coulombic efficiency of up to 99.5%. The great enhancement of the electrochemical lithium storage performance can be attributed to the improvement of the electronic conductivity and lithium diffusivity of electrodes. The present results have verified the ability of Cu doping to improve electrochemical lithium storage performances of manganese oxides.
The electrode material is the key factor for developing asymmetric supercapacitors. A simple water-boiling treatment was adopted to fabricate a Mn3O4/Ni(OH)2 nanocomposite on a large scale, which exhibited a splendid electrochemical performance with a boiling time of 3 h, achieving a capacitance of 742 F g–1 at 1 A g–1. When assembling the asymmetric capacitor with the Mn3O4/Ni(OH)2 composite and activated carbon separately as positive and negative electrodes, a capacitance of 43 F g–1 was attained at 0.2 A g–1 with an energy density of 15.3 Wh kg–1 at a power density of 168.8 W kg–1. This simple, reproducible, ecofriendly, and large-scale fabrication method is practical for preparing other transition metal oxides for the purpose of use in asymmetric supercapacitors with superior properties.
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