查看更多>>摘要：? 2022 Elsevier B.V.Manufacturing stable and thin air electrodes for flexible Zn-air batteries becomes increasingly important and remains challenge. Here, we report low-cost mechanical calendering to fabricate thin gas-diffusion layers (GDL), catalytic layers (CL) and then heat pressing together. Finally, cylindrical and other sizes of flexible air electrodes are produced without the use of commercially expensive carbon cloth or carbon papers. By assembling the flexible air cathodes with anode Zn-In-Bi alloy powders or Zn foils, alkaline gel electrolytes and membranes, two kinds of Zn-air cells are assembled for performance evaluation. Results reveal that the LR6 Zn-air cells show a capacity of 5300–5400 mAh and an energy density of 340 Wh·kg?1 at 100 mA, having a double discharge capacity compared to the same size alkaline ZnMnO2 cells. Under a high drain rate of 1000 mA, the capacity and utilization of the Zn alloy powder remain 2750 mAh and 372 mAh·g?1, respectively. The flexible pouch Zn-air cells exhibit excellent charge-discharge performance under conditions of each cycle with 10 min at 2 mA cm?2. The discharge voltage is maintained in the range of 1.25–1.30 V within 120 cycles while the charge voltage is 2.00–2.05 V. These results demonstrate that the thin air cathodes can satisfy the high bending requirements for cylindrical LR6 size cells and flexible pouch Zn-air cells, as well as have high mechanical stability and electrochemical performance. Electrochemical impedance spectroscopies of the air cathodes and Zn-air cells are also examined.
查看更多>>摘要：? 2022 Elsevier B.V.The performance of carbon-based materials as negative electrodes for supercapacitors can be effectively enhanced through the method like increasing the surface area and active sites as well as heteroatoms doping, while the limited capacitance caused by the surface adsorption mechanism restricts the further improvement of capacitance. Herein, we design hollow and porous FeP spheres (H-FeP) in-situ encapsulated into 3D honeycomb-like porous graphitic N, P-codoping carbon (PGNPC) by a unique post-annealing strategy. The post-annealing process acts as an efficient modification strategy in two aspects: the formation of a porous graphitic carbon framework during the catalytic reaction between iron oxide with carbon and the morphology changing from solid to hollow by introducing the Kirkendall diffusion process. With the synergetic effect of introducing hollow FeP into carbon, the N, P-codoping and 3D porous graphitic carbon framework ensure the as-prepared materials with enhanced performance for negative electrodes. Thus, H-FeP@PGNPC materials display outstanding specific capacitance (696 F g?1), high rate capacity and cycling stability. Using multi-shelled Mn3O4 encapsulated in rGO as the positive electrode, the assembled asymmetric supercapacitor exhibits high specific capacitance and energy density with negligible capacity loss (retain 90% after 5000 cycles).
查看更多>>摘要：? 2022In this study, the structure-properties relationship of magnesium matrix nanocomposites was studied. Using an accumulative extrusion (AE) process, the matrix was reinforced by adding 0.25, 0.5 and 1 wt% crystalline and amorphous silica nanoparticles separately. The mechanical behavior of nanocomposite strips was investigated by hardness and uniaxial compression tests. The results indicated that the Mg/0.5%SiO2-Am had the best room temperature compressive properties. An increase of 28.5% in compressive yield strength after extrusion and 235% after annealing was measured. Ultimate compressive strength (UCS) was increased by 20% without reduction in the nanocomposite ductility compared to the pure magnesium strip. FESEM and OM were used for microstructural analysis and revealed no visible cracks or distinct defects between magnesium layers after AE passes. It is found from the EDS analysis that the reinforcement distribution after the AE process was uniform with few agglomerates. Texture analysis using X-ray diffraction and EBSD after the AE process for samples reinforced with 0.5 wt% of amorphous and crystalline silica nanoparticles indicated a negligible difference in the basal plane orientation of the monolithic and nanocomposite magnesium strips after the AE process along extrusion direction. On the other hand, increasing the basal plane peak intensity after annealing for the sample reinforced with amorphous silica compared to the sample reinforced with crystalline silica indicated a weakening of basal texture. Furthermore, the EBSD analysis showed that amorphous silica nanoparticles are more effective than crystalline silica in grain refinement.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, BiOBr and BiOBr/ZnO were produced by using a simple hydrothermal method, and then were modified by a short-time low temperature plasma treatment using the gas of argon mixed with 3% hydrogen in pulsed mode with the fixed cycle discharge times. The related morphological, crystal, chemical, optical and photocatalytic properties were investigated. A three-dimensional flower-like structure of pure BiOBr and layered ultrathin nanosheets structure of BiOBr/ZnO can be observed. And the plasma treatment process at the discharge power of 100 W would not affect their basic morphologies. However, the changes in the surface chemical bonding has been identified, which indicates the presence of strong electronic interactions and strong chemical bonds caused by the plasma modification. The photodegradation rate has been greatly improved by mixing BiOBr with ZnO since the heterojunction structure was built during the hydrothermal process. Moreover, the photocatalytic activity can be further improved after the plasma treatment, it is attributed to the higher photogenerated carrier separation rate and narrow band gap due to the defects generated by the surface plasma effects.
查看更多>>摘要：? 2022Graphene reinforced copper composites (Gr/Cu) have considerable potential applications in many fields of modern industry. However, the present preparation methods are complicated, expensive, and time-consuming, which restricts the large-scale application. Therefore, it is vital to find an industrial method to prepare Gr/Cu composites with overall properties. In this work, Gr/Cu composites were prepared by combining electrodeposition of Gr/Cu powders, thermal reduction, and sintering (denoted as the EP-TS method). The composite shows outstanding overall properties when the current density is 62.5 mA/cm2 and the graphene oxide (GO) concentration in the electrolyte is 0.1 g/L. The addition of graphene promotes the nucleation process and refines the grains resulting in improved mechanical properties. During the process of electrodepositing and thermal reduction, the copper matrix is purified and most of the oxygen-containing functional groups of GO are removed. And the GO structure is partially repaired resulting in improved electrical properties. Compared with the one-step electrodeposition method, the graphene in the composites has fewer oxygen-containing functional groups which guarantee the thermal stability of the Gr/Cu composite. Our method provides a promising prospect for rapid mass production of graphene reinforced copper matrix composites with excellent overall properties, which has good compatibility with current copper industry technology.
查看更多>>摘要：? 2022 Elsevier B.V.The green and low-cost recycling of spent LiFePO4 (LFP) cathode materials has become an urgent problem to be solved. In this work, a completely green and easy scale-up recycling process is developed to recycle the cathode powders from spent LFP batteries. The optimal regeneration conditions are obtained by adjusting temperature, Li+ concentration and reductant dosage. Meanwhile, the mechanism of regeneration is investigated by microscopic characterization and electrochemical performance testing. The regenerated LFP shows a good discharge specific capacity of 148 mAh/g at 0.05 C, which exhibits around 96% the capacity of raw LFP. Additionally, the costs of the consumption only account for 19.8% the price of raw LFP, which indicates that this method has good prospect of economic returns. This regeneration method is low in cost, simple in process, mild in conditions and easy to scale up, providing technical supports for the sustainable development of lithium-ion battery industry.
查看更多>>摘要：? 2022 Elsevier B.V.Regulating charge distribution through heterostructure engineering is an encouraging approach to achieving efficient alkaline water electrolysis. Here, a Fe-doped Ni phosphides/Ni sulfide p-p heterojunction (NiFe-PS) for oxygen evolution reaction (OER) is constructed on nickel foam. It is shown that the built-in electric field at the interface of Fe-doped Ni phosphides/Ni sulfide facilitates the charge transfer and modifies the electronic properties of the catalyst, thereby enhancing its conductivity and catalytic activity. Profiting from the rational electronic structure modulation, the designed NiFe-PS electrode possesses excellent OER performance among phosphides with low overpotentials of 204 and 256 mV at current densities of 10 and 100 mA cm-2, respectively. Meanwhile, the prepared catalyst displays high stability in the long-term chronopotentiometric test (125 h @ 100 mA cm-2). Structural characterizations confirm that the outer phosphide layer can withstand long-term surface oxidation and operate as a robust shield to prevent oxidation of the inner sulfide, ensuring rapid electron transport within the catalyst throughout the OER process.
查看更多>>摘要：? 2022 Elsevier B.V.The compound GeTe, despite its simple stoichiometry, is rather unconventional and has been investigated both from a fundamental and technological perspective: it is of high interest for several technologies such as data-storage (phase change memories) and thermoelectricity. The understanding of GeTe growth is thus a key issue for technological applications and fundamental understanding. In this work, GeTe crystallization kinetics is compared to Ge/Te reactive diffusion kinetics using in situ X-ray diffraction measurements, as well as in situ transmission electron microscopy. GeTe crystallization from an amorphous solid solution exhibiting the stoichiometry of the compound GeTe is found to occur at the same temperature as for the reactive diffusion of an amorphous Ge layer on top of a polycrystalline Te layer. Furthermore, GeTe growth is of tridimensional type in the two cases, and can be modeled by the Johnson-Mehl-Avrami-Kolmogorov model. Using this model, the activation energies of nucleation and growth were determined for both crystallization and reactive diffusion. The results suggest that GeTe exhibits nucleation/reaction kinetics unusually low compared to atomic transport kinetics, contrasting with other germanides.
查看更多>>摘要：? 2022 Elsevier B.V.The crystal structure, electrical conductivity, thermal expansion behavior and electrocatalytic properties for oxygen reduction reaction of A-site deficient (La0.3Ca0.7)1?xFe0.7Cr0.3O3-δ (x = 0.01–0.05) perovskites were investigated in comparison with their stoichiometric counterpart (x = 0). The tolerance limit of the perovskite structure for A-site deficiency was x = 0.04 or so. The unit cell parameters decreased and oxygen nonstoichiometry (δ) increased with increasing A-site deficiency. The electrocatalytic activity was appreciably improved by introducing an A-site deficiency of x = 0.04, concomitant with a slight decrease of the electrical conductivity and thermal expansion coefficient. The porous electrode with x = 0.04 exhibited a polarization resistance of 0.044 Ω·cm2 at 800 °C, lowered by about 42% compared with the electrode with x = 0. Moreover, the introduction of the A-site deficiency enhanced the stability of the perovskite structure and electrocatalytic activity relative to cathodic polarization. The electrode with x = 0 showed segregation of calcium onto the surface and an increase of the polarization resistance by 0.106 Ω·cm2 after being cathodically polarized under 250 mA·cm-2 at 800 °C for 6 h. In contrast, surface calcium segregation was undetected for the electrode with x = 0.04 after being likewise polarized and the electrocatalytic activity of the polarized A-site deficient electrode was virtually undegraded. The improved stability of the structure and electrocatalytic activity of the A-site deficient electrode was tentatively explained with respect to its defect chemistry.
查看更多>>摘要：? 2022 Elsevier B.V.Anode materials play a critical role in enhancement of lithium-ion batteries (LIBs) toward high energy density. In this work, the hollow Cu2O nanospheres with surface {111} and {110} active facets and intraluminal Cu2O nanoparticles are synthesized using a simple and low-cost one-step method, and used as the anode materials for LIBs to achieve high performance. Some advanced spectroscopic characterization and electrochemical methods are employed for fundamentally understanding the relationship between structure/morphology/composition and electrochemical performance. Using these materials, the as-fabricated anodes can deliver an excellent specific capacity of 914.4 Ah.kg?1 at a current density of 1 C (375 A.kg?1) after 390 cycles, and even at a large current density of 10 C, the capacity retention is still as high as 356.7 Ah.kg?1. The enhancement in battery performance is attributed to the novel structure of Cu2O-HNs anode materials with high surface area, high surface active {111} and {110} facets and the intraluminal Cu2O nanoparticles. The outstanding electrochemical performance achieved in this work demonstrates a high potential of Cu2O-HNs to be applied as high-energy anode materials for practical lithium-ion batteries.
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