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Two-dimensional (2D) nanocarbons have attracted considerable researching interest in electrochemical energy storage owing to their large surface area and shortened ion-diffusion distance. Herein, we propose a versatile co-activation strategy for preparing porous carbon nanosheets by employing easily available petroleum asphalt as the precursor. Besides KOH, introducing of NaOH as the co-activating reagent not only realized the morphological change from microparticles to nanosheets, but also altered the textural properties of the products, which is totally different from the traditional template route, offers a new possibility towards 2D nanocarbons. The large specific surface area and highly-developed micropores combined with its unique structural advantages, make it a very promising electrode material for high-rate supercapacitor in ionic liquid electrolyte. For instance, the porous carbon nanosheets deliver a large specific capacitance (169 F/g 1 A/g), superior rate capability (72.8% capacitance retention at 50 A/g), and good cycling stability after 5000 cycles. Moreover, the energy density can reach to 52.3 Wh/kg even at an ultrahigh power density of 43.75 kW/kg, which have shown great potential for applications in electrochemical energy storage devices such as supercapacitors.

A facile solvothermal method is used to fabricate hierarchical core-shell nanostructures based on praseodymium, nickel and cobalt oxides supported on nickel foam. The Pr6O11 nanoparticles were first grown on the nickel foam and then utilized as a backbone for anchoring NiO, Co3O4 and NiCo2O4 nanostructures to form a core-shell structure. The core-shell electrodes exhibit superior electrochemical performance than single Pr6O11 nanoparticles electrodes. A superior specific capacitance of 1635 F/g at a current density of 0.5 mA/cm2 with good cycling stability was obtained for the Pr6O11@NiCo2O4 electrode. Moreover, a solid-state supercapacitor was fabricated by assembling Pr6O11@NiCo2O4 electrodes using KOH/PVA as the solid electrolyte. The as-prepared solid-state device demonstrated impressive energy density of 6.6 W h/kg and a power density of 150 W/kg. This optimal performance could be attributed to the high conductive nickel foam current collector and synergistic effects generated from the core-shell architecture of NiCo2O4 and the Pr6O11 nanoparticles.

This work explores the compound Li1+z/3Ni1/2-z/2Ti1/2+z/6O2 (z = 0, 0.1, 0.2, 0.3, 0.4, 0.5) and compares the electrochemical performance difference with z to the proposed percolation network. X-ray diffraction combined with Rietveld refinements show that rock-salt structure is obtained by the simple sol-gel process, and the lattice parameters are increased with the increasing level of Li-excess. Micromorphology observation reveals that particles are irregular and the size is distributed within 100 nm. In addition, a detailed reaction mechanism is examined by X-ray photoelectron spectroscopy and cyclic voltammetry, which exhibits the evolution of Ni, Ti and O in the initial charge-discharge process and confirms that they all make contributions to capacities. Electrochemical performance test shows that the discharge capacities increase with the amount of Li and Li1.17Ni0.25Ti0.58O2 delivers the discharge capacities up to 223.9 mAh g−1. At the current density of 400 mA g−1, it still provides a large capacity of 120 mAh g−1. Furthermore, Li1.17Ni0.25Ti0.58O2 has the highest lithium ion diffusion coefficient among all samples.

In order to enhance the electrochemical properties of nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode material, lithium-ion conductor shell was coated on the surface of the material through a facile wet chemical route. The morphologies, structures and chemical compositions of the samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, energy dispersive spectrometer and X-ray photoelectron spectroscopy. The result shows that the particle surface was uniformly coated by a very thin LaPO4 layer. Electrochemical measurements proved that the LaPO4-coated sample exhibited excellent cycling performance. The capacity retention of LaPO4-coated sample was 91.2% at 1 C after 100 cycles, which was higher compared with that of the pristine sample (76.4%). Moreover, the rate performance of the coated sample was greatly enhanced especially at 2, 5 and 10 C rate. The LaPO4-coated sample showed smaller charge transfer resistance and higher diffusion coefficient of lithium ions compared with those of the pristine sample.

In this study, a transparent memristor with a configuration of Au/SnO2/FTO is fabricated by a simple solution process at low temperature and further utilized to mimic biological synapses. A series of significant synaptic functions, including nonlinear transmission characteristics, spike-rate-dependent plasticity (SRDP), short-term plasticity (STP) and long-term plasticity (LTP) are emulated. The transition from short-term to long-term plasticity is also investigated in the device by repeated stimulation. The nonlinear rectification characteristic in the current memristor is attributed to the Schottky barrier at the Au/SnO2 interface. By controlling the oxygen vacancy migration induced under electrical input, the barrier at the interface can be modified, giving rise to the different synaptic functions. These results suggest that the proposed Au/SnO2/FTO memristor in this study is a promising synaptic device for artificial neural network applications.

The polycrystalline samples of undoped BiFeO3, Ce doped BiFeO3 (Bi0.9Ce0.1FeO3) and Zr dpoped BiFeO3 (BiFe0.9Zr0.1O3) were prepared by rapid liquid phase sintering technique. The effects of A-site substitution with Ce and B-site substitution with Zr on the structure, defects and multiferroic properties of BiFeO3 ceramics were comparative investigated. Undoped and doped BiFeO3 samples are well crystallized in perovskite structure, whilst Ce and Zr doping results in slight distortion in the lattice structure. With Ce and Zr doping, the average grain sizes decrease. Positron annihilation lifetime measurements reveal that there are vacancy-type defects in the three samples, and Bi0.9Ce0.1FeO3 sample has the maximum open volume and concentration of the vacancy defect among those three samples. Both Ce and Zr doping can improve the leakage current, ferroelectric and magnetic properties, whereas Zr doping exhibited better ability. The better electric properties in BiFe0.9Zr0.1O3 may be due to the effective reduction of oxygen vacancies, Fe2+ and impurity phases by Zr doping. The cause for better magnetic properties in BiFe0.9Zr0.1O3 sample may be that the insertion of Fe vacancies and nonmagnetically active Zr4+ ions in antiferromagnetic Fe sublattice can effectively suppress the spiral spin modulation structure.

Lithium sulfide (Li2S) is regarded as a promising cathode material for lithium ion batteries since it can be well paired with lithium–free anodes. However, the low electronic conductivity of Li2S and the shuttle effect of lithium polysulfides are the two biggest obstacles for commercial applications of Li2S cathode. Herein, a bifunctional host with high electronic conductivity and high adsorption of lithium polysulfides, CNT threaded porous carbon nitride nanoflakes, is designed and prepared for Li2S cathode. Ultrafine Li2S particles are infiltrated into the bifunctional host to form a three-dimensional Li2S/porous carbon nitride/carbon nanotube composite (3D Li2S/p–C3N4/CNT) by facile liquid infiltration and evaporation. The as–prepared 3D Li2S/p–C3N4/CNT exhibits a high initial discharge capacity of 997.5 mAh g−1 at 0.2 A g–1, superior rate capability of 432.3 mAh g−1 at 2.0 A g–1 over 600 cycles and good cycling stability. The excellent electrochemical performance of 3D Li2S/p–C3N4/CNT can be attributed to the high conductivity network of CNT and ultrafine Li2S, and the strong polar adsorption of porous carbon nitride nanoflakes.

Li-excess disordered rock-salt cathode material, Li 1+z/3 Ni 1/2-z/2 Ti 1/2+z/6 O 2 (Z = 0, 0.1, 0.2, 0.3, 0.4, 0.5) compounds have been synthesized via a facile sol-gel method. The X-ray diffraction (XRD) indicates that the obtained phase of the Li-excess materials is rock-salt. Morphology and microstructure observation shows that the particles size of this material is well distributed within the range of 100 nm. Cells are examined at room temperature with the voltage range of 2.5–4.5 V and the sample Li 1.1 Ni 0.35 Ti 0.55 O 2 delivers the highest capacity of about 116.5 mAh g −1 at 20 mA g −1 . The exploration of the lithium mobility in this system indicates that 0-transition metal diffusion channels do form when increasing the amount of Li. Furthermore, combining XRD after cycle, their structure evolution in these cation-disordered Li-excess materials was investigated.

The fuel discharging efficiency of direct borohydride fuel cell (DBFC) depends on both the anodic catalyst activity and borohydride hydrolysis. In this paper, Co 3 O 4 anodic catalysts prepared from different cobalt sources used in DBFC have been investigated. It showed that the catalytic performance of Co 3 O 4 was associated with its microstructure that relied on the precursor. The maximum power densities obtained was 40, 62 and 28 mW cm −2 of DBFC with Co 3 O 4 catalyzed anode from CoCl 2 (marked DBFC-A), Co(NO 3 ) 2 (marked DBFC-B) and Co(CH 3 COO) 2 (marked DBFC-C), respectively. The Co 3 O 4 -A has the highest number of electron transfer ( n = 7.06 ) which is close to the theoretical value ( n = 8 ), and DBFC-A showed good voltage stability with specific capacity of 720 mAh.g −1 . A rapid voltage attenuation occurred in DBFC-B with the specific capacity of 330 mAh.g −1 because Co 3 O 4 from Co(NO 3 ) 2 has the higher catalytic activity for both borohydride oxidation reaction (BOR) and hydrolysis which lead to the lower fuel utilization efficiency.

The construction of heteroatom-doped hierarchical carbon frameworks has attracted significant research attention as high-performance electrode materials for supercapacitors. Herein, a facile one-step Mohr’s salt-assisted KOH activation strategy has been developed for the production of S-doped hierarchical carbon frameworks with large specific surface area from sustainable spruce bark. We found Mohr’s salt plays multiple roles during the synthesizing process by simultaneously acting as an S source, the template to generate mesopores, and the co-activator beyond KOH. As the electrode for supercapacitors, the high specific capacitance of 281 and 156 F g−1 can be achieved in aqueous electrolyte and ionic liquid electrolyte at 1 A g−1, respectively. More importantly, the electrode also displays excellent rate capability where a high capacitance can be maintained at large charge-discharge operation. Moreover, the supercapacitor device also demonstrated an energy density is high up to 66.26 Wh kg−1 at the power density of 875 W kg−1 in ionic liquid electrolyte. These results acquired could offer a versatile way to convert renewable biomass into value-add porous carbon for electrochemical energy-storage applications.

A cathode material LiNi0.8Co0.1Mn0.1O2 coated with ionic conductor Li3VO4 was prepared through a wet-chemical method. The crystalline phase, chemical valence state and the microstructure of Li3VO4-coated material were investigated by X-ray diffraction, energy dispersive spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. The existence of the Li3VO4 coating layer on the surface of sphere particle was validated, and the electrochemical performances of the samples were investigated. The 3 wt% Li3VO4-coated sample exhibited the most remarkable cycling capability at 1 C after 100 cycles, with a retention value of 83.54%. Moreover, the rate performances of all Li3VO4-coated samples were significantly enhanced at high rates (2, 5 and 10 C). Electrochemical impedance spectroscopy and cyclic voltammetry performance analyses revealed that the excellent electrochemical performance of the Li3VO4-coated sample is ascribed to the improved lithium ion conductivity and the suppression of the chemical reaction between the electrode material and electrolyte.

Similar to the three-dimensional perovskites, two-dimensional (2D) layered lead halide perovskites constitute a particular class of semiconductor materials in the family of perovskites. This article reports syntheses of needle-like bundles of 2D perovskite (C6H5CH2NH3)2PbI4 by a two-step processing technique. The concentration of C6H5CH2NH3I precursor has a great influence on the product, structural and compositional analyses prove the phase and stoichiometry of 2D perovskite (C6H5CH2NH3)2PbI4 with high crystallinity for the needle bundles synthesized with concentration of C6H5CH2NH3I higher than 25 mg/mL. Intensive studies on the growth mechanism of the products were carried out; we believe the involvement of C6H5CH2NH3+ group determines the layered structure and the final morphology of the products. Photoluminescence measurement show that the needles possess a band-edge emission peak centering around 540 nm and a narrow full width at half maximum of about 30 nm.

Excess additives in laser ceramics compromise the physical nature and degrade the laser performance, and should be diminished properly in order to improve the quality of the laser ceramics. In this work, highly transparent Yb:Y2O3 ceramics were fabricated by using low-level ZrO2-MgO as double-sintering aid and vacuum sintering. Morphology and particle size of the ball-milled ceramic powders were studied by using transmission electron microscopy (TEM) and Rietveld refinement. Phase composition, microstructure and optical transmittance of the sintered ceramic samples were investigated by using X-ray diffractometer (XRD), scanning electron microscopy (SEM) and UV-VIS-NIR spectrometer. The optimized additive concentrations were found as low as 0.8 wt% for ZrO2 and 0.075 wt% for MgO, and the corresponding Yb:Y2O3 ceramic sample fabricated had the transparency as high as 79.4% at 1200 nm and 81.5% at 2000 nm. A possible sintering mechanism was proposed and discussed in this paper. It is expected that the elevated laser performance will be produced in this low-level additive induced Yb:Y2O3 transparent ceramics.