Growing market demand from portable electronics to electric automobiles boosts the development of lithium-ion batteries (LIBs) with high energy density and rate performance. However, strong solvation effect between lithium ions (Li⁺) and solvent molecules in common electrolytes limits the mobility of Li⁺ ions in electrolytes. Consequently, anions dominate the charge conduction in electrolytes, and in most cases, the value of Li⁺ transference number (T⁺) is between 0.2 and 0.4. A low T₊ will aggravate concentration polarization in the process of charging and discharging, especially at high rate, which not only increases the overpotential but also intensifies side reactions, along with uneven deposition of lithium (Li) and the growth of lithium dendrites when lithium metal is used as anode. In this review, promising strategies to improve T₊ in liquid electrolytes would be summarized. The migration of Li⁺ ions is affected directly by the types and concentration of lithium salts, solvents, and additives in bulk electrolytes. Besides, Li⁺ ions will pass through the separator and solid electrolyte interphase (SEI) when transferring between anodes and cathodes. With this in mind, we will classify and summarize threads of enhancing T₊ from five aspects: lithium salts, solvents, additives, separators, and SEI based on different mechanisms, including covalently bonding, desolvation effect, Lewis acid-base interaction, electrostatic interaction, pore sieving, and supramolecular interaction. We believe this review will present a systematic understanding and summary on T₊ and point out some feasible threads to enhance battery performance by enhancing T₊.

A broadband metasurface antenna is proposed in this letter. The antenna is based on a nonperiodic metasurface. The modal behavior of the metasurface and the slot is analyzed using characteristic modes analysis (CMA). Three desired modes of the metasurface are found. Furthermore, the slot acts not only as a feeding structure but also as a metasurface-loaded antenna. By combining the three modes of the metasurface and the modes of the slot, the wide bandwidth is achieved under multimode resonance. To verify the design, the proposed metasurface antenna is simulated, fabricated, and tested. The results show that the proposed metasurface antenna achieves a wide impedance bandwidth above 79% and a wide 3 dB realized gain bandwidth of 77%.

A low profile dual-polarized metasurface antenna with high isolation and low cross-polarization is proposed in this paper. The proposed metasurface consists of an array of 4×4 patches. Through characteristic mode analysis (CMA), a pair of degenerate modes are identified to achieve the desired radiation features. By modifying the patches of the metasurface, the strongest mode current distributions of the two modes are moved from the center to the edge of the metasurface. One feed port can efficiently excite only one particular mode, and the other mode cannot be excited simultaneously. Each of the modes are differentially fed using two Y-shaped microstrip lines via two slots. As a result, both high isolation and low cross-polarization can be obtained. The simulation and experimental results show that the proposed antenna achieves not only a low profile of 0.05 λ0 (where λ0 is the free-space wavelength at the center resonant frequency) but also a broad impedance bandwidth of 36% and a high isolation of 53 dB. In particular, the enhanced cross polarization discrimination (XPD) is lower than -40 dB at the broadside, lower than -33 dB within ±30° of the main lobe, and lower than -28 dB within ±60° of the main lobe.

The high-resistive grain boundaries are the bottleneck for Li⁺ transport in Li₇La₃Zr₂O₁₂ (LLZO) solid electrolytes. Herein, high-conductive LLZO thin films with cubic phase and amorphous domains between crystalline grains are prepared, via annealing the repetitive LLZO/Li₂CO₃/Ga₂O₃ multi-nanolayers at 600 °C for 2 h. The amorphous domains may provide additional vacant sites for Li⁺, and thus relax the accumulation of Li⁺ at grain boundaries. The significantly improved ionic conductivity across grain boundaries demonstrates that the high energy barrier for Li⁺ migration caused by space charge layer is effectively reduced. Benefiting from the Li⁺ transport paths with low energy barriers, the presented LLZO thin film exhibits a cutting-edge value of ionic conductivity as high as 6.36 × 10⁻⁴ S/cm, which is promising for applications in thin film lithium batteries.