查看更多>>摘要：? 2022 Elsevier B.V.Transition metal sulfides (TMSs) present high theoretical capacity as anode materials for Lithium-ion batteries, and structural design of TMSs is proved to be an effective strategy to acquire satisfactory electrochemical performances. Herein, the hierarchical NiS2/CoS2@N,S-C nanospheres consisting of NiS2/CoS2 matrixes and N,S-codoped carbon outer layer (N,S-C) are fabricated. Additionally, NiS2/CoS2@N,S-C nanospheres with different core-shell structures appear in this study when the amount of nickle and cobalt is precisely controlled, which further confirms the different abilities of nickle and cobalt in tailoring and modulating structure. In particular, the NiS2/CoS2@N,S-C(Ni:Co=1:2) with yolk-shell property presents sufficient internal void space, which is conductive to the transport of Li+ and electron. Moreover, the protective N,S-codoped carbon layer and the porous sheet arrays provide the enhanced structural stability and increased active sites. Benefitting from the unique structure, the NiS2/CoS2@N,S-C(Ni:Co=1:2) anode with binary metal sulfide composition presents good cycling performance (795 mAh g?1 at 0.2 A g?1 after 100 cycles) and rate capability (469 mAh g?1 at 5 A g?1). This study provides a reference for the design and preparation of novel TMSs-based materials with different morphologies in the field of energy storage.
查看更多>>摘要：? 2022 Elsevier B.V.The hot tearing susceptibility (HTS) of Mg–xAl–yCa (x + y = 8) alloys with different Ca/Al ratios (namely 0.06, 0.34, 0.63, 1.04, 1.75, and 2.82) is experimentally investigated using a “T-shaped” hot tearing measuring system. Additionally, the HTS of the alloys is determined using an optimized version of the Clyne–Davies model in conjunction with the solidification parameters of the alloys. The results of the optimized model, i.e., the fact that the HTS decreases with the increase in the Ca/Al ratio, are in good agreement with both the numerical simulations and experimental results. Furthermore, the hot tearing curves, thermal analysis curves, and microstructure of the alloys show that with the increase in the Ca/Al ratio, the intergranular bonding before the hot tearing initiation changes from relying on a liquid film only to involving both intergranular bridging and the liquid film, which enhances the intergranular bonding ability. In addition, the increase in the eutectic phase content, number of dendrite skeleton voids, and dendrite gap width result in an increase in the number of feeding channels and a decrease in the flow resistance of the residual liquid phase, thus increasing its filling efficiency against tears. Therefore, in alloys with high Ca/Al ratios, the large grain size results in a reduction in both the number and total length of grain boundaries, thereby reducing the number of locations where hot tears may initiate. Therefore, the HTS of alloys with a high Ca/Al ratio is significantly reduced.
查看更多>>摘要：? 2022 Elsevier B.V.The purpose of the present study is to track the formation of the intermetallic phases that form in the binary Al-Mg system and investigate their orientation relationships to the parent Al and Mg elements. Therefore, two compositions Al60Mg40 and Al40Mg60 (wt%), which are very suitable for studying the diffusion of Al in Mg and Mg in Al were heated from room temperature up to elevated temperatures below the melting point. Powder metallurgy, including cold extrusion was used to create a large interface between the Al and Mg, which facilitates fast reaction kinetics. In order to observe the phase formation during heating and analyze the crystal structures, X-ray diffraction using synchrotron radiation was used. The use of high energy X-ray was extremely helpful, enabling the detection of small phase fractions and information on the orientation relationships between the Al and Mg and the intermetallic phases that formed. The γ-Al12Mg17phase was the first phase formed in both alloy compositions on annealing. Subsequently, the β-Al3Mg2phase was formed. After annealing at 400 oC for 2 h, the Al40Mg60 composition consisted of a very high amount of Al12Mg17 and a small amount of Mg phase while the Al60Mg40 composition consisted of mainly Al3Mg2 and a small fraction of Al12Mg17, indicating that thermodynamic equilibrium has been approximated. On further annealing at 400 oC for 12 h, both compositions formed only one phase, namely the Al12Mg17 phase in the Al40Mg60 composition and the Al3Mg2 phase in the Al60Mg40 composition. In this condition, a Pitsch-Schrader orientation relationship was found between the Mg and the γ-Al12Mg17 phase, the occurrence of which is discussed within the framework of literature models. No orientation relationship between either the Al or the Mg with the Al3Mg2 phase was found.
查看更多>>摘要：? 2022 Elsevier B.V.Heteroatom doping is an effective route to boost the capacitance performance of metal sulfides-based electrode materials. Herein, an array of hierarchical 3D mesoporous Cu doped CoSx@Co(OH)2 nanosheets (namely Cu/CoSx@Co(OH)2) is successfully prepared on Ni foam through a metal-organic-framework (MOF) mediated approach. The combination of compositional merits and tuned electronic properties induced by copper doping leads to superior capacitance performance. The optimal Cu doped electrode (Cu/CoSx@Co(OH)2-2) displays an ultrahigh specific capacitance and outstanding rate capability, which outperforms the best values obtained on other transition metal sulfide (TMS) electrodes. And the Cu/CoSx@Co(OH)2-2//activated carbon (AC) asymmetric two-electrode supercapacitor device exhibits a favorable energy density of 39.25 Wh kg?1 and outstanding cycle life. X-ray photoelectron spectroscopy (XPS) results reveal that the greatly decreased binding energy barriers of two redox pairs (Co2+/Co3+ and Cu+/Cu2+) are beneficial to higher electrochemical performance. Density function theory (DFT) results further disclose the Cu-doping effect and the benefit of nanocomposite formation on the energy storage performance. The results provide an inspiration to the optimization of TMS-based electrodes for high performance electrochemical energy storage systems.
查看更多>>摘要：? 2022 Elsevier B.V.Li-ion batteries (LIBs) are in increasing demand due to their application in a large variety of fields such as portable electronic devices and electric vehicles. However, the development of high-performance electrode materials with a long lifetime, excellent rate capability, and high safety is considered as a significant challenge in the advancement of LIBs. Recently, titanium niobium oxide (TNO) compounds have been considered as one of the most promising intercalation-type anode materials and highly potential alternatives to commercial graphite and Li4Ti5O12 anodes. This family of materials possess high theoretical capacities (377–402 mAh/g) resulting from their multiple redox couples (Ti4+/Ti3+, Nb5+/Nb4+, Nb4+/Nb3+), high safety, low volume changes during cycling, high working potential, and excellent cyclic stability. However, their low electronic/ionic conductivities would result in their poor rate performance. Various strategies such as ion doping, composite preparation with conductive materials, dimensional/morphological controlling, and defective structure engineering design have been proposed to improve the rate performance of TNO materials. In this review study, dimensional/morphological controlling, and defective structure engineering approaches are reviewed for enhancing the electrochemical properties of pure TNO anodes. In this context, the detailed findings of the most important recent literature on TNO anode materials are reviewed, from their optimal synthesis parameters, and the obtained morphological/structural features to their electrochemical properties. Furthermore, the challenges to the practical use of TNO anodes in full-cell LIBs are presented. Finally, the research gaps and the future perspective are proposed.
查看更多>>摘要：? 2022 Elsevier B.V.Hexaferrites that exhibit the intrinsic and strong magnetoelectric (ME) coupling effect have been considered the most promising candidate for single-phase multiferroics. Currently, the strong ME coupling effect in this system was widely reported in single crystal form, while it is rare in polycrystalline one. In this work, Y-type hexaferrite BaSrCo2Fe12-xAlxO22 (x = 0.0, 0.3, 0.6 and 0.9) ceramics were manufactured with conventional solid-state reaction. Their magnetic, dielectric, and ME coupling properties were systematically surveyed. It was revealed that Al doping could result in a high magnetic transition temperature of ~ 345 K for x = 0.9. Also, the ferroelectric polarization and abnormal magnetodielectric properties were significantly enhanced which could be maintained down to 200 K. Most interestingly, the sample x = 0.9 displayed strong direct and converse ME coefficients of ~ 400 ps/m and ~ 900 ps/m at 150 K, respectively. Therefore, these results reveal that Al doping can broaden our understanding of the Y-type hexaferrite in room-temperature multiferroics.
查看更多>>摘要：? 2022 Elsevier B.V.It is still a great challenge to design and fabricate electromagnetic wave absorbing materials with both excellent attenuation capability and effective absorption bandwidth (EAB). Herein, cooperatively coupling the magnetic nanoparticles with dielectric matrix, ternary MXene/MnO2/Ni composites were synthesized through a facile self-assembly method. The MXene (Ti3C2Tx) was served as backbone to effectively assemble MnO2 nanorods, which was further used to support the Ni nanoparticles. The relationship between Ni content and the electromagnetic wave absorption performance of the MXene/MnO2/Ni composites was discussed to maximize the attenuation and impedance matching. The optimized MXene/MnO2/Ni exhibited a strong reflection loss (RL) of ? 54.4 dB at 11.6 GHz and a wide EAB of 6.08 GHz (9.04–15.12 GHz). Importantly, a wide EAB of 12 GHz (6–18 GHz) can be tuned to low frequency range (C band) by the modification of Ni content. The combination of the dielectric loss and magnetic loss attributes to the comprehensively excellent absorption performance. In addition, the Ti3C2Tx matrix and the formation of interface between ternary assemblies will generate the interface polarization and scattering path to favor the attenuation of electromagnetic wave.
查看更多>>摘要：? 2022 Elsevier B.V.The proper N doping engineering and microstructure design are of essential importance to develop advanced carbon anodes for Li-ion batteries. Herein, a facile strategy was developed to fabricate hierarchical porous carbon with controllable pore structures, N doping content and configurations, which was easily realized via introducing zinc salt as recyclable activator and regulator in the precursors. The zinc salt could not only function as pore-forming agent to facilitate the formation of hierarchical porous defect-rich structure, but also act as N-confined reactor to preserve the N-containing intermediates and promote N doping in the carbon matrix during thermal conversion. Specifically, 21.7% N content (increased by 115%) which was mainly composed of pyridinic/pyrrolic N (88.6%) was achieved with the addition of Zn5(OH)6(CO3)2. Meanwhile, desirable mesopore-dominant hierarchical porous carbon with appropriate specific surface area was obtained. Benefiting from the unique microstructure and N functionalities, the NC-Zn5(OH)6(CO3)2 anode delivered a high reversible capacity of 564 mAh g?1 at 200 mA g?1 over 100 cycles, which was almost two times higher than those for NC, and remarkable long-term cycling stability with high coulombic efficiency around 100% after 1300 cycles at 1000 mA g?1. This work provides an intriguing and feasible avenue for the reasonable structure design of carbon material with superior electrochemical performance for sustainable energy storage.
查看更多>>摘要：? 2022 Elsevier B.V.Development of all-solid-state lithium-ion batteries (ASSLBs) with potentially high energy density and safety is critical for next-generation energy storage devices. In this work, a low-cost flexible Li2SnO3(LSO)-coupled PEO-based composite single-ion conducting polymer solid-state electrolyte (CSIPE) was prepared by a simple solvent-free solid-phase method. The obtained LSO-coupled CSIPE exhibited a high ionic conductivity of 5.59 × 10?4 S cm?1 at 60 °C with a high lithium ion transference number of 0.54 and an electrochemical stability window as high as 5.28 V. In addition, the results based on Vogel-Tammann-Fulcher (VTF) model and differential scanning calorimetry (DSC) measurements indicated that the presence of LSO reduced the activation energy for lithium ion migration and the crystallinity of the polymer matrix to provide channels and flexible polymer chains for the transportation of lithium ions. Moreover, the fabricated lithium metal anode based full cell worked stably for more than 100 cycles maintaining a high specific capacity of 127.1 mAh g?1 and a specific capacity retention ratio of 96.5% at a high cycling rate of 0.5 C. While, the CSIPE also demonstrated an excellent rate performance and outstanding adaptation to cathodes. Furthermore, the obtained LSO-coupled CSIPE remained stable even at a temperature as high as 322 °C without thermal runaway, and worked under different current densities for 450 h without short-circuiting, indicating good interfacial stability to ensure the safety of the batteries. It is expected that this LSO-coupled CSIPE is a promising substitute for liquid electrolytes with broad commercial prospects.
查看更多>>摘要：? 2022 Elsevier B.V.The development of non-noble metal electrocatalysts for oxygen evolution reaction (OER) has attracted widespread attention in the field of energy. Herein, we report a facile in-situ etching method to convert commercial stainless steel felt (SSF) into NiFe2O4 octahedral nanoparticles as an efficient and robust OER electrode. This preparation method of NiFe2O4 is different from the conventional ones, both nickel and iron elements come from the substrate itself without extra addition of precursors, as well as NiFe2O4 octahedral nanoparticles are self-grown directly on the substrate without binder. The treated SSF shows good water oxidation properties with low overpotential, small Tafel slope, and durable stability at 500 mA cm?2 for 200 h. Moreover, the effect of NaNO3 in the etchant is studied carefully, which plays the function of removal of chromium and promoting the formation of octahedral nanoparticles, resulting in the enhancement of conductivity and catalytic activity. This study presents a new preparation method for producing NiFe2O4 octahedral nanoparticles with the characteristic of low cost, simple process, wide raw material sources, and favorable OER activity, which demonstrates a good application prospect in the field of large-scale hydrogen production.
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