Search

ZnO/Co/C/reduced graphene oxide (RGO) composites are synthesized through carbonization of ZnCo-MOF-5/GO under an Ar/H2 flow. The abundant active sites (e.g., functional groups and lattice defects), copious heterointerfaces (among Co, ZnO, C, and RGO), and wrinkled architecture trigger multiple dipole polarization, interface polarization, and enhanced conductive loss. By adjusting the content of RGO, the electromagnetic parameters for ZnO/Co/C/RGO composites were effectively regulated. The minimum reflection loss (RLmin) of ZnO/Co/C/RGO-50 composites is −52.72 dB at 1.70 mm, and the EAB is 3.57 GHz. Futhermore, CST simulation results further confirm the remarkable RCS reduction capacity for ZnO/Co/C/RGO-50 composites. The reduction value of RCS is 22.84 dB m2, and effective absorption can reach the entire angle range. The superior microwave absorption property for ZnO/Co/C/RGO composites is benefited from cooperative action of dielectric loss (dipole polarization, interface polarization, conductive loss) and magnetic loss (natural resonance and exchange resonance). [ABSTRACT FROM AUTHOR]

Herein, an efficient one-dimensional (1D) N-doped Co/C nanotube absorber was designed by a cobalt source and solvent ratio comodulation strategy. First, we explored the influences of different cobalt sources (CoCl2, Co-(OAc)2, Co-(NO3)2, and CoSO4) on the morphology and microwave absorption (MA) property, which showed that CoCl2 facilitated the formation of nanotubes with a relatively uniform diameter and length. Notably, the Co/C nanotubes displayed an ultrawide effective absorption bandwidth (EAB) of 6.885 GHz at 2.2 mm when the filling ratio was only 8 wt %. Then, by adjusting the solvent ratio of isopropanol (IPA) and water, Co/C showed a strong absorption of −44.51 dB with an EAB of 5.44 GHz at 2.35 mm. The outstanding MA performance is ascribed to the synergistic effect of dielectric and magnetic components, which is conducive to optimizing the impedance matching, thus broadening the EAB. In addition, the 1D nanostructure is good for constructing three-dimensional (3D) conductive networks and enhancing conductive loss. Since Co nanoparticles are wrapped in carbon nanotubes (CNTs), the confinement effect can effectively prevent the agglomeration of ferromagnetic nanoparticles, adjusting the MA performance. It is worth mentioning that the maximum Radar cross section (RCS) value of Co/C can be reduced by 28.8 dB m2. Furthermore, the RCS values are all lower than −10 dB m2 from −90 to 90° and the minimum RCS value can reach −46.8 dB m2. This work provides a strategy for designing lightweight MA absorbers with strong RL and ultrawide EAB. [ABSTRACT FROM AUTHOR]

CeO2, an n-type semiconductor material, has been widely used in microwave absorption (MA) due to its unique structural features such as oxygen vacancies and interstitial atoms. In this paper, Co/CeO2/C composites were prepared by a hydrothermal method followed by a pyrolysis process. The effect of different pyrolysis temperatures (650–950 °C) on the MA property of the composites was investigated. When the pyrolysis temperature was 850 °C, the Co/CeO2/C-850 composite exhibited outstanding MA behavior in the frequency range of 2–18 GHz, displaying a minimum reflection loss (RLmin) of −45.22 dB and an effective absorption bandwidth (EAB) of 4.61 GHz at a thin thickness of 1.75 mm. The MA performance of the Co/CeO2/C composites is mainly attributed to the dielectric loss due to interfacial polarization originating from different interfaces and dipole polarization caused by the oxygen vacancies in CeO2. In addition, the introduction of Co nanoparticles not only provides the magnetic loss but also modulates impendence matching for the current magnetoelectric coupling system. [ABSTRACT FROM AUTHOR]

Porous C nanosheet/Cu2S composites were prepared using a simple self-template method and vulcanization process. The Cu2S nanoparticles with an average diameter of 140 nm are uniformly distributed on porous carbon nanosheets. When used as the anode of a potassium-ion battery, porous C nanosheet/Cu2S composites exhibit good rate performance and cycle performance (363 mAh g−1 at 0.1 A g−1 after 100 cycles; 120 mAh g−1 at 5 A g−1 after 1000 cycles). The excellent electrochemical performance of porous C nanosheet/Cu2S composites can be ascribed to their unique structure, which can restrain the volume change of Cu2S during the charge/discharge processes, increase the contact area between the electrode and the electrolyte, and improve the electron/ionic conductivity of the electrode material. [ABSTRACT FROM AUTHOR]

Nano-solid spherical Nb2O5/nitrogen-doped carbon (NC) composite is obtained by the hydrothermal method followed by a calcination procedure. The Nb2O5/NC composite exhibits good rate performance and sustainable cyclic stability (144 mAh g−1 at 1000 mAh g−1 upon 2000 charge–discharge cycles) as an anode material in Na-ion batteries (SIBs). The excellent performance of the Nb2O5/NC composite is attributed to its unique nanosphere structure, in which Nb2O5 nanocrystals embedded in porous NC matrix can restrain agglomeration of Nb2O5 nanocrystals and ensure electrolyte accessibility, and the NC matrix can provide effective active sites and increase ions/electrons transfer. This work offers a new method to fabricate nano-solid spherical Nb2O5/NC composite with good Na+ storage property, which can be extended for synthesizing other metal oxide/NC composite as SIB anode. [ABSTRACT FROM AUTHOR]

ZnS has acquired increasing attention for high‐performance PIBs anode because of its remarkable theoretical capacity, and redox reversibility for conversion reaction. However, the larger volume variation and delayed reaction kinetics for the ZnS in the discharge/charge processes lead to pulverization and severe capacity degradation. Herein, the trumpet‐like ZnS@C composite was synthesized by template method by using sodium citrate as carbon source followed by vulcanization process. As potassium ion batteries (PIB) anode, ZnS@C composite exhibits good rate performance and long life (stable reversible capacity of 107.8 mAh/g over 2000 charge‐discharge cycles at 5 A/g and high reversible capacity of 310 mAh/g at 0.1 A/g). The outstanding electrochemical performance of the ZnS@C composite is ascribed to its unique structure, which can mitigate the volume expansion of ZnS in the charge discharge process, expand the contact area between the electrode and electrolyte, and improve the conductivity of electrode materials by the introduction of carbon layer. This method of synthesizing trumpet‐like ZnS@C composite provides an important strategy for obtaining potassium ion batteries anode with long cycle. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have come into the limelight in the field of microwave absorption since they can be developed into porous carbon-based MOF derivatives with a variety of features, such as controlled defects, tunable structures, and variable compositions. In this paper, Cu3[Co-(CN)6]2 Prussian blue analogue (CuCo-PBA) precursors with a regular cubic morphology were synthesized by a simple co-precipitation method and converted into CuCo nanocube/N-doped carbon nanotube (CuCo/NCNT) derivatives by annealing them in argon. It was found that when the annealing temperature was 850 °C, the minimum reflection loss (RLmin) of CuCo/NCNT could reach −54.13 dB with an effective absorption bandwidth of 4.01 GHz. The excellent microwave absorption properties were attributed to the mutual synergy of conduction loss, interfacial polarization, magnetic resonance loss, and eddy current loss. Therefore, this work provides an effective preparation method for the design of lightweight carbon-based microwave-absorbing materials with heterogeneous interfaces using Prussian blue. [ABSTRACT FROM AUTHOR]

Nb2O5 possesses superior fast Li+ storage capability for LIB anodes, benefiting from its fast pseudocapacitive behavior and low volumetric change within the cycling processes. However, the poor electric conductivity for Nb2O5 restricts its reaction kinetics and rate property. Herein, Nb2O5/carbon (C) submicrostructures are fabricated by solvothermal method followed by calcination process. The Nb2O5/C submicrostructures exhibit outstanding rate behavior and cyclic performance (332 (194) mAh g−1 after 1000 cycles at 1 (5) A g−1). The superior electrochemical property is attributed to the distinctive structure for Nb2O5/C submicrostructures, in which Nb2O5 nanoparticles uniformly distributed within Nb2O5/C composite can protect Nb2O5 nanoparticles from agglomeration, and the porous carbon matrix can enhance electron/ion conductivity. This work furnishes a novel strategy for fabricating Nb2O5/C submicrostructures with superior Li+ storage performance, which can be potentially used to design other metal oxide/C submicrostructures for second battery anode. [ABSTRACT FROM AUTHOR]

Stabilizing Li‐rich layered oxides without capacity/voltage fade upon cycling is a prerequisite for a successful commercialization. Although the inhibition of structural and interfacial changes is identified as an effective strategy, the battery community always seeks for a technologically flexible method to make it really competitive among the cathode. Herein, the gradient W‐doping within Li1.2Mn0.56Ni0.16Co0.08O2 (LLMO) is proposed to relieve crystal disintegration and simultaneously enhance interfacial stability because of the formation of Li2WO4 coating layer on the material surface. This is mainly attributed to the scenario that partial Mn replacement by W can stabilize the LLMO structure and regulate the electrochemical activity of Mn element. The W‐doped LLMO (W@LLMO) possesses improved specific capacity and voltage stability (83.2% capacity retention and voltage retention of 94.9% after 200 cycles at 0.5 C). Besides, a practical pouch cell based on the W@LLMO cathode presents sufficient gravimetric energy density (318 Wh kg−1) and cycling stability (capacity retention of 87.7% after 500 cycles at 1.0 C). This study presents an effective method to design robust Li‐rich layered cathodes for next‐generation Li‐ion batteries. [ABSTRACT FROM AUTHOR]

ZnSe has got extensive attention for high‐performance LIBs anode due to its remarkable theoretical capacity and environmental friendliness. Nevertheless, the large volume variation for the ZnSe in the discharge/charge processes brings about rapid capacity fading and poor rate performance. Herein, ZnSe/C hollow polyhedrons are successfully synthesized by selenization of zeolitic imidazolate framework‐8 (ZIF‐8) with resorcinol‐formaldehyde (RF) coating. The protection of C layer derived from RF coating layer and Ostwald ripening during the process of selenization play important roles in promoting formation of ZnSe/C hollow polyhedrons. The ZnSe/C hollow polyhedrons exhibit good rate performance and long‐term cycle stability (345 mAh g−1 up to 1000 cycles at 1 A g−1) for lithium ion batteries (LIBs) anode. The improved electrochemical performance is benefit from the unique ZnSe/C hollow structure, in which the hollow structure can effectively avoid terrible volume expansion, and the thin ZnSe/C shell can not only provide adequate diffusion paths of lithium ions and but also enhance the electronic conductivity. [ABSTRACT FROM AUTHOR]

For the past few years, a new generation of energy storage systems with large theoretical specific capacity has been urgently needed because of the rapid development of society. Lithium–sulfur (Li−S) batteries are regarded as one of the most promising candidates for novel battery systems, since their resurgence at the end of the 20th century Li−S batteries have attracted ever more attention, attributed to their notably high theoretical energy density of 2600 W h kg−1, which is almost five times larger than that of commercial lithium‐ion batteries (LIBs). One of the determining factors in Li−S batteries is how to design/prepare the sulfur cathode. For the sulfur host, the major technical challenge is avoiding the shuttling effect that is caused by soluble polysulfides during the reaction. In past decades, though the sulfur cathode has developed greatly, there are still some enormous challenges to be conquered, such as low utilization of S, rapid decay of capacity, and poor cycle life. This article spotlights the recent progress and foremost findings in improving the performance of Li−S batteries by employing multifunctional metal phosphides as host materials. The current state of development of the sulfur electrode of Li−S batteries is summarized by emphasizing the relationship between the essential properties of metal phosphide‐based hybrid nanomaterials, the chemical reaction with lithium polysulfides and the latter′s influence on electrochemical performance. Finally, trends in the development and practical application of Li−S batteries are also pointed out. [ABSTRACT FROM AUTHOR]