A dual-polarized hybrid 8-antenna array operating in the 2.6-GHz band (2550-2650 MHz) for 5G communication multi-input multi-output (MIMO) operation in the smartphone is presented. The proposed hybrid antenna array elements are symmetrically placed along the long edges of the smartphone, and they are composed of two different 4-antenna array types (C-shaped coupled-fed and L-shaped monopole slot) that exhibit orthogonal polarization. Therefore, coupling between the two antenna array types can be reduced, and the MIMO system performances are enhanced. A prototype of the proposed 8-antenna array is manufactured and measured. Good impedance matching (10 dB return loss or better), desirable cross polarization discrimination (XPD better than 15 dB) and acceptable isolation (better than 12.5 dB) are obtained. Envelope correlation coefficient (ECC) and channel capacity are also calculated to evaluate the MIMO performances of the proposed antenna array.

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An eight‐port antenna array designed for future 5G 2.6 GHz band (2550–2650 MHz) for multi‐input multi‐output (MIMO) in the smartphone applications is presented. In order to enhance the port isolation and reduce correlation between antennas, square loop radiating strip with orthogonal polarisation is employed. The proposed antenna array is composed of four pairs of uniform antenna elements that are symmetrically placed at the four corners of the main board, and each antenna pair includes a communal square loop and two independently coupled feeding strips. By exciting the square loop from the two feeding strips, respectively, two orthogonally polarised waves are generated. Thus, four horizontally polarised and four vertically polarised antennas are achieved in total. Due to this feature, coupling between antenna pairs is reduced and the MIMO performances are enhanced. A prototype of the proposed antenna array was fabricated, and the experimental results show good impedance matching and acceptable isolation measured across the bands of interest. The MIMO performances such as envelope correlation coefficient, mean effective gain, multiplexing efficiency and channel capacity are also calculated. Besides, simulations of the antenna shifted to 3.5 GHz are also performed. The consistent performances indicate that the proposed structure has good scalability and is promising for future 5G smartphone applications.

Room-temperature sodium-ion batteries have attracted great attentions for large-scale energy storage applications in renewable energy. However, exploring suitable anode materials with high reversible capacity and cyclic stability is still a challenge. The VS 4 , with parallel quasi-1D chains structure of V 4+ (S 2 2− ) 2 , which provides large interchain distance of 5.83 Å and high capacity, has showed great potential for sodium storage. Here, the uniform cuboid-shaped VS 4 nanoparticles are prepared as anode for sodium-ion batteries by the controllable of graphene oxide (GO)-template contents. It exhibits superb electrochemical performances of high-specific charge capacity (≈580 mAh·g −1 at 0.1 A·g −1 ), long-cycle-life (≈98% retain at 0.5 A·g −1 after 300 cycles), and high rates (up to 20 A·g −1 ). In addition, electrolytes are optimized to understand the sodium storage mechanism. It is thus demonstrated that the findings have great potentials for the applications in high-performance sodium-ion batteries.

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The as-obtained NiCo2O4@CoMoO4/NF-7 electrode exhibits superior electrocatalytic performance and extraordinary durability for OER, HER, and overall water splitting.

A hybrid ion capacitor (HIC) based on potassium ions (K + ) is a new high‐power intermediate energy device that may occupy a unique position on the Ragone chart space. Here, a direct performance comparison of a potassium ion capacitor (KIC) versus the better‐known sodium ion capacitor is provided. Tests are performed with an asymmetric architecture based on bulk ion insertion, partially ordered, dense carbon anode (hard carbon, HC) opposing N‐ and O‐rich ion adsorption, high surface area, cathode (activated carbon, AC). A classical symmetric “supercapacitor‐like” configuration AC–AC is analyzed in parallel. For asymmetric K‐based HC–AC devices, there are significant high‐rate limitations associated with ion insertion into the anode, making it much inferior to Na‐based HC–AC devices. A much larger charge–discharge hysteresis (overpotential), more than an order of magnitude higher impedance R SEI , and much worse cyclability are observed. However, K‐based AC–AC devices obtained on‐par energy, power, and cyclability with their Na counterpart. Therefore, while KICs are extremely scientifically interesting, more work is needed to tailor the structure of  “Na‐inherited” dense carbon anodes and electrolytes for satisfactory K ion insertion. Conversely, it should be possible to utilize many existing high surface area adsorption carbons for fast rate K application.

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