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Numerous studies have been made to design absorption–diffusion–integrated metasurface (ADIM) for the application of electromagnetic stealth. However, it is still a challenge to achieve an outstanding stealth effect and a simple structure simultaneously. In this article, we propose two simple hybrid copper–graphene units with similar absorptivity and a reflected phase difference of pi, which are utilized to construct a novel ADIM by using a simulated annealing algorithm with a scattering pattern prediction module. A sample with an overall size of 200 × 200 mm2 is designed, fabricated, and measured. Both simulation and experimental results are in good agreement, which fully demonstrate the design method. The proposed ADIM with only a single functional layer exhibits more than 20 dB radar cross section reduction from 7.5 to 13.5 GHz maintained to 20° oblique incidence, which could address this challenge successfully. Power loss density and surface current distributions of the proposed two units are given to provide a physical insight of the mechanisms. The proposed ADIM can enable a wide application in stealth cloak, microwave imaging, wave front manipulation, and so on. [ABSTRACT FROM AUTHOR]

Carbonaceous materials have been usually adopted as the anode for high energy density potassium‐ion hybrid capacitors (KICs) owing to their low voltage plateau, high conductivity, and excellent electrochemical compatibility. The improvements of their specific capacity and sluggish intercalation mechanism are still challenges to further boost the energy density of KICs while maintaining high power density and long cycle life. Herein, a N‐doped mesoporous carbon sphere array composite is developed by a dual‐templates method. The N‐doped carbon sphere array with interpenetrated macro‐ and meso‐pores facilitates the fast electron transport and rapid K+ diffusion. The uniformly introduced Co3O4 nanoparticles (NPs) confined in the array enable a kinetically boosted conversion reaction for excess and fast K+ storage. The partially oxidized Co NPs can efficiently enhance the conductivity of the entire composite. By introducing this optimized conversion capacity from encapsulated Co3O4 NPs, the composite with intercalation and conversion coupling mechanisms displays superior capacity and cycle life. The assembled KICs exhibit high energy/power densities (148 Wh kg−1/124 W kg−1) and great cycling performance (94% after 5000 cycles, 0.5 A g−1). This promising strategy demonstrates an example for carbonaceous composite anode with synergistic K+ storage hybrid mechanism toward high performance KICs. [ABSTRACT FROM AUTHOR]

This manuscript reports a 3D ordered amorphous and porous TiO 2 framework embedded with rGO sheets (TiO 2 @rGO), which is a great anode with low insertion barrier and fast kinetics in K-ion half-cells. When applying the TiO 2 @rGO as anodes in KICs, the KICs can give rise to high energy/power densities and great long-term service life. [Display omitted] TiO 2 is considered as a low cost, long-term stable, and safe anode for high power K-ion hybrid capacitors (KICs) due to its abundant reserve, small volume expansion rate, and sloping voltage plateau that avoids K-ion plating at high voltage polarization. However, the enhancement of its low capacity and sluggish kinetics caused by poor electroconductivity and high insertion barrier is still challenging to further develop high-performance KICs. Herein, the reduced graphene oxide (rGO) is embedded in the walls of 3D ordered macro-/mesoporous TiO 2 (termed as TiO 2 @rGO framework) to create intimate TiO 2 /rGO interfaces, ensuring the effectively electron transportation during potassiation/depotassiation of TiO 2 while maintaining rapid ions/electrolyte diffusion. Furthermore, the controlled amorphous TiO 2 framework can further lower the lattice insertion energies, contributing to a fast accommodation of K-ion. As expected, the amorphous TiO 2 @rGO framework (TiO 2 @rGO-1) exhibits a superior rate capability (148.8 mAh g−1 at 5 A g−1) and cycling stability (171.2 mAh g−1 at 1 A g−1 after 800 cycles). The assembled KICs can reach a high energy/power density of 125.2 Wh kg−1/4267.4 W kg−1 as well as a long-term lifespan. This tactic provides a reliable and general way to design a TiO 2 -based anode with fast kinetics toward high-performance KICs. [ABSTRACT FROM AUTHOR]

Because of the unique ability to combine high energy density with high power density, lithium-ion hybrid capacitors (LICs) have generated significant interest. Among the various anodes being explored for LICs, silicon (Si) stands out as a particularly promising anode material due to its high theoretical capacity. Nevertheless, the formidable challenge lies in the rapid capacity fade resulting from substantial volume expansion. Herein, a simple and efficient spray drying technique was used to fabricate a Si@rGO@NC composite with micro-nano structure. In this composite, Si nanoparticles are encapsulated between reduced graphene oxides (rGO) hollow spheres and a layer of carbon is coated on the surface of both the Si and the micron-sized composite particles, forming a rigid and mechanically stable structure. The composite combines the high activity of nano-Si with the industrially easy handling of micron-scale particles. Moreover, the rGO hollow spheres not only enhance the electrical conductivity but also buffer the volume expansion of the electrode and provide channels for the rapid transport of electrolyte/ions. Thanks to its advantageous structural features, the constructed LICs with activated carbon as cathode can achieve a Max. energy/power density of 253.1 Wh kg−1/10,824.1 W kg−1 and maintain 84.3 % of its initial capacitance after 8000 cycles. The micro-nano structured design concept of Si-based materials developed in our work could offer new insights and directions for the future development of Si-based energy storage devices. [Display omitted] • Si@N-doped carbon composite armed with rGO hollow spheres is prepared (Si@rGO@NC). • The Si@rGO@NC electrode shows high-rate capability in Li-ion half-cells. • Si@rGO@NC//AC LICs exhibit superior energy/power density and long lifespan. [ABSTRACT FROM AUTHOR]

Co 3 O 4 nanoparticles embedded in 3D ordered macro-/mesoporous TiO 2 have been synthesized through a in situ method form dual templates and the anode shows good electrochemical performance in Li-ion capacitor. [Display omitted] • Co 3 O 4 nanoparticles embedded in 3D ordered macro-/mesoporous TiO 2 are prepared. • The Co 3 O 4 @TiO 2 shows enhanced rate capability and cycling performance in LIBs. • The Co 3 O 4 @TiO 2 composite exhibits great electrochemical performance for LICs. Lithium-ion hybrid capacitors (LICs) have gained increasing focus owing to their high energy/power densities. The development of anodes with superior rate capability is an effective way to surmount the kinetic mismatch between anodes and cathodes, and thus, enhancing the energy/power densities. Herein, Co 3 O 4 nanoparticles embedded in three-dimensionally (3D) ordered macro-/mesoporous TiO 2 (Co 3 O 4 @TiO 2) are synthesized through an in situ method from dual templates. Differing from the composite prepared by loading active nanoparticles on support, Co 3 O 4 nanoparticles are embedded in TiO 2 framework, which can improve the stability of the electrode. Furthermore, the hierarchically porous structure of TiO 2 is in favor of the rapid diffusion of ions and electrolyte. As a result, The Co 3 O 4 @TiO 2 -2 composite with an optimized Co 3 O 4 content (~25 wt%) delivers a high capacity of 944.1 mAh g−1 after 100 cycles at 0.1 A g−1 and high-rate capability (405.7 mAh g−1 after 1000 cycles at 5 A g−1). The LIC assembled with Co 3 O 4 @TiO 2 -2 anode and activated carbon (AC) cathode delivers high energy/power densities (maximum, 87.9 Wh kg−1/10208.9 W kg−1) and great cycle stability (88.1%, 6000 cycles, 0.5 A g−1). [ABSTRACT FROM AUTHOR]

Achieving both high gravimetric and volumetric rate performances of the anode for lithium ion capacitors (LICs) is still a challenge. Herein, we propose a dense Li 3 VO 4 (LVO)/graphene aerogel (GA) composite as the two active components anode, the crystalline and particle size of LVO can be regulated in the GA that provides abundant heterogeneous nucleation sites to prevent the agglomeration and preferred growth of LVO. The dense LVO/GA exhibits significantly improved electrochemical performances. The gravimetric/volumetric specific capacity can reach up to 84.4 mAh g−1 and 63.3 mAh cm−3 at the very high current density of 16 A g−1, as well as the 85% capacity retention after 5000 cycles at 8 A g−1. This superior performance is contributed from the facilitated diffusion rate of confined LVO clusters in GA, the accelerated electron transport offered by the three dimensional (3D) graphene skeleton that closely surrounds LVO, and the fast electrochemical kinetics boosted by the combined dense structure. The LICs exhibit excellent energy/power densities (maximum 122.2 W h kg−1, 8.8 kW kg−1). We believe that this two active components design demonstrates an unparalleled function that the single active material cannot realize, and provide a promising road propelling the development of high performance LICs. • Dense Li 3 VO 4 /graphene aerogel is prepared based on heterogeneous nucleation. • Crystalline and particle size of LVO can be regulated in the graphene skeleton. • Both high gravimetric and volumetric rate performances can be achieved. • Lithium ion capacitors exhibit high energy/power densities and stability. [ABSTRACT FROM AUTHOR]

The main challenge for the emerging K-ion capacitors (KICs) is designing high-rate performance anode to match the fast kinetics of the cathode. In this work, we encapsulated MoS 2 nanosheets in N-doped mesoporous carbon nanowires (MoS 2 @MCNWs) by dual-templating method as high-rate anode. After the performance was optimized with respect to MoS 2 content, the preferred MoS 2 @MCNWs-2 (25 wt% MoS 2) electrode shows a superior rate capability (89.2 mAh g−1 at 10 A g−1). Furthermore, the constructed KIC demonstrates superior energy/power density (Max. 106.5 Wh kg−1/9703.9 W kg−1) with excellent cycling stability (97.6% of initial capacitance after 6000 cycles at 1 A g−1). The good electrochemical properties arise mainly from the one-dimensional (1D) nanostructure that can facilitate the transportation of electrons, the opened ordered mesopores on the carbon nanowires that can endow the rapid K-ion/electrolyte diffusion, and the ultrafine MoS 2 nanosheets embedded in carbon nanowires that can offer a lot of active sites. Furthermore, the doped N in carbon can afford additional adsorption sites for discharge products, promoting the durability of the electrode, which is confirmed by density function theory (DFT) calculations. This delicate design could offer a new avenue for the development of 1D-based anode with high-rate performance in metal-ion capacitors. [Display omitted] ● MoS 2 nanosheets were confined in N-doped mesoporous carbon nanowires (MoS 2 @MCNWs). ● MoS 2 @MCNWs electrode shows high-rate capability in K-ion batteries. ● MoS 2 @MCNWs//AC K-ion capacitors exhibit high energy/power density and long lifespan. [ABSTRACT FROM AUTHOR]

Featuring high theoretical capacity of Se and low cost of element K, potassium-selenium (K-Se) batteries are considered as prospective power storage equipment. However, their drawbacks including dramatic volume change of Se, shuttling effect and relatively low operation voltage (< 3 V) can result in short lifespan and low power density. Here, we report a novel type of K-Se capacitors employing Se confined in N-doped mesoporous carbon opal (Se@NMCO) as anode and activated carbon (AC) as cathode based on the K-Se electrochemical reaction mechanism. This prepared K-Se capacitors can achieve large energy and power density (127 Wh kg−1 and 11523 W kg−1) with super-long lifespan (maintaining up to 10, 000 cycles with a capacity retention of 91 % at 2 A g−1). The great performance may arise from the hierarchically porous structure of Se@NMCO, in which the well-ordered macropores can enhance the mass transport effectively and the mesopores can further guide the reactants to the active reaction sites. Additionally, opal nanostructure also plays an importance role in enhancing the K-storage performance. This ingenious design would open an avenue for developing super long-life devices on the basis of K-Se reaction mechanism. [Display omitted] • Se was successfully confined in N-doped mesoporous carbon opal (Se@NMCO). • Se@NMCO electrode shows great electrochemical performance in K-Se batteries. • Se@NMCO//AC K-Se capacitors exhibit high energy/power densities and long lifespan. [ABSTRACT FROM AUTHOR]