With the ever-increasing demand for power sources of high energy density and stability for emergent electrical vehicles and portable electronic devices, rechargeable batteries (such as lithium-ion batteries, fuel batteries, and metal–air batteries) have attracted extensive interests. Among the emerging battery technologies, metal–air batteries (MABs) are under intense research and development focus due to their high theoretical energy density and high level of safety. Although significant progress has been achieved in improving battery performance in the past decade, there are still numerous technical challenges to overcome for commercialization. Herein, this mini-review summarizes major issues vital to MABs, including progress on packaging and crucial manufacturing technologies for cathode, anode, and electrolyte. Future trends and prospects of advanced MABs by additive manufacturing and nanoengineering are also discussed.

Large-size vertical β- ${Ga_{2}O_{3}}$ Schottky barrier diodes (SBDs) with various device areas were demonstrated on a Si-doped n-type drift layer grown by hydride vapor phase epitaxy (HVPE) on bulk Sn-doped (001) n-type β- ${Ga_{2}O_{3}}$ substrate. In this study, the devices have two circular contacts with a diameter of 1500 μm and 500 μm and two square contacts with dimensions of 1600×1600 μm² and 800×800 μm², corresponding to the area of 0.2×10^-2 cm² (the smallest device), 0.6×10^-2 cm², 1.8×10^-2 cm², and 2.6×10^-2 cm² (the largest device). The breakdown voltage (BV) was determined to be -261 V for the largest device and -427 V for the smallest device. Also, the ideality factor (η) of vertical ${Ga_{2}O_{3}}$ SBDs with different device areas exhibited the same value of 1.07, except for the largest device area of 2.6×10^-2 cm² with an ideality factor of 1.21. At an applied forward bias of V_F=2 V, the specific on-state resistance (R_onA) of all the ${Ga_{2}O_{3}}$ SBDs remains relatively low with values ranging from 1.43×10^-2 Ωcm² to 7.73×10^-2 Ωcm². The measured turn-on voltage (V_on) of all the SBDs remains low with a narrow distribution.

High-efficiency perovskite solar cells were fabricated using low thermal budget photonic-cured compact TiO₂ as the electron transport layer. The best device on glass substrate exhibited an efficiency of 15% with average efficiency of 12.7%, comparable to the devices with furnace-annealed TiO₂. Flexible devices were as efficient as 11.2%.

${\mathrm{Ni}}_{\mathrm{2}}\mathrm{Si}$ Ohmic contacts were fabricated via pulsed laser deposition on $\mathrm{n-}\mathrm{SiC}.$ The contacts electrical, structural, compositional, and surface morphological properties were investigated as a function of annealing temperatures ranging from 700 to $\text{950\hspace{0.05em}°}\mathrm{C}.$ The as-deposited and $\text{700\hspace{0.05em}°}\mathrm{C}$ annealed contacts were non-Ohmic. Annealing at $\text{950\hspace{0.05em}°}\mathrm{C}$ yielded excellent Ohmic behavior, an abrupt void free interface, and a smooth surface morphology. No residual carbon was present within the contact metallization or at the contact-SiC interface and the contact showed no appreciable thickness increase as a result of the annealing process. Our results demonstrate that aside from maintaining the desirable electrical integrity associated with Ni and Ni/Si Ohmic contacts, the ${\mathrm{Ni}}_{\mathrm{2}}\mathrm{Si}$ Ohmic contacts possessed improved interfacial, compositional, microstructural, and surface properties which are required for reliable high temperature and high power device operation.