Nanostructured anodic films on transition metals prepared using the electrochemical anodization method have recently attracted particular attention owing to their extraordinary properties and potential use in a variety of applications. Herein, we provide a thorough review of the anodization fabrication of anodic films with different nanostructures, including nanopores, nanotubes, nanoflowers, nanoneedles and nanowires on transition metals, focusing on the growth processes of nanostructured anodic films on three representative transition metals, namely, iron, copper and zinc. Specific consideration is given to the anodization behavior and formed film nanostructures of these transition metals. We conclude that electrolyte composition plays a key role in influencing the final morphologies of anodic films. Fluoride-containing solutions represent universal electrolytes for forming nanostructured anodic films on transition metals. The main applications of the resulting nanostructured anodic films, especially in energy-related fields, such as photoelectrochemical water splitting and supercapacitors, are also presented and discussed. Finally, we indicate the main challenges associated with the fabrication of anodic films with highly ordered nanostructures and the potential future directions of this field are indicated.

Although various hosts have been proposed to accommodate the Lithium (Li) metal to solve the uneven Li deposition and infinite volume change, the pulverization of the host or lithiophilic modification layer easily leads to structural damage and the poor cycling stability of the composite anode. Herein, we design a host of metal nitrides (Mo₂N and WN heterostructures) nanoparticles capsulated in the hollow carbon nanospheres, which can accommodate Li metal to form a stable composite anode. The lithiophilic Mo₂N guides uniform infusion and reduces the nucleation barriers of Li metal during electrochemical process. Note that the rigid WN matrix is uniformly composited with Mo₂N, which can suppress the pulverization of Mo₂N during the repeat Li plating/stripping, ensuring the stability of regulated deposition during long cycling. High mechanical strength, uniform surface potential distribution and good electrolyte wettability of the Li metal-based composite anode guarantee the rapid Li plating/stripping kinetics. Thus, the obtained composite anode can stably cycle 1400 h at 1 mA cm^-2 and 1 mA h cm^-2 in the symmetric battery. The assembled full cells with LiNi_0.8Mn_0.1Co_0.1O₂ (NCM811) also deliver high capacity retention under the high loading (8.6 mg cm^-2) or lean electrolyte (2 μL mg^-1) condition. This work suggests a promising host structure design to construct a highly stable lithium metal anode for practical applications.

Energy storage devices, e.g., supercapacitors (SCs) and zinc-ion batteries (ZIBs), based on aqueous electrolytes, have the advantages of rapid ion diffusion, environmental benignness, high safety and low cost. Generally, SCs provide excellent power density with the capability of fast charge/discharge, while ZIBs offer high energy density by storing more charge per unit weight/volume. Although the charge storage mechanisms are considered different, manganese dioxide (MnO₂) has proven to be an appropriate electrode material for both SCs and ZIBs because of its unique characteristics, including polymorphic forms, tunable structures and designable morphologies. Herein, the design of MnO₂-based materials for SCs and ZIBs is comprehensively reviewed. In particular, we compare the similarities and differences in utilizing MnO₂-based materials as active materials for SCs and ZIBs by highlighting their corresponding charge storage mechanisms. We then introduce a few commonly adopted strategies for tuning the physicochemical properties of MnO₂ and their specific merits. Finally, we discuss the future perspectives of MnO₂ for SC and ZIB applications regarding the investigation of charge storage mechanisms, materials design and the enhancement of electrochemical performance.

Lithium-ion batteries (LIBs) and ceramic fuel cells (CFCs) are important for energy storage and conversion technologies and their materials are central to developing advanced applications. Although there are many crosslinking research activities, e.g., through materials and some common scientific fundamentals employed for both LIB and CFCs, crosslinking scientific aspects to achieve a comprehensive understanding are missing. There is a lack of such a review to promote and guide further research and development in the crosslinking of LIBs and CFCs. Herein, we review the existing application of LIB materials in CFCs to discover the scientific advances of lithium-ion and proton transport cooperation and identify the new directions of Li-CFCs in the future. This review is the first to propose CFC advances, especially at low temperatures (300-600 °C) by applying LIB materials to practical devices and highlight the material properties and new device functions with enhanced performance, as well as the scientific mechanisms and principles. Furthermore, we seek to deepen the scientific understanding of materials science, ion transport mechanisms and semiconductor electrochemistry to benefit both the battery and fuel cell fields.

The demand for cryogenic applications has resulted in higher requirements for the low-temperature performance of energy storage systems. Lithium-metal batteries are the most promising energy storage systems. Lithium-metal anodes have the merits of high capacity and low potential. However, at low temperatures, especially sub-zero, the formation of lithium dendrites seriously hinders their applications. Herein, distinct from the traditional strategies of separating lithium metal from oxygen substances, we propose a new strategy to suppress dendrites by exposing lithium metal to air for short periods to generate a controlled oxidative protective layer in situ that is compact, homogeneous and mainly composed of Li₃N, Li₂O, LiOH and Li₂CO₃. Symmetrical and full cells are assembled. The air-pretreated Li metal symmetrical cell exhibits an excellent lifespan of up to 4500 h (1 mA cm^-2) at 30 °C and also shows a smaller voltage polarization of 20 mV at 1.0 mA cm^-2 at -20 °C. Importantly, the full cell using the air-pretreated Li metal as an anode and NCM811 as a cathode can charge-discharge normally at -20 and -40 °C. This work provides an efficient and facile approach for developing superior lithium-metal batteries for future utilization at a wide range of temperatures.

Sodium-ion batteries (SIBs) and capacitors (SICs) have been drawing considerable interest in recent years and are considered two of the most promising candidates for next-generation battery technologies in the energy storage industry. Therefore, it is essential to explore feasible strategies to increase the energy density and cycling lifespan of these technologies for their future commercialization. However, relatively low Coulombic efficiency severely limits the energy density of sodium-ion full cells, particularly in the initial cycle, which gradually decreases the number of recyclable ions. Presodiation techniques are regarded as effective approaches to counteract the irreversible capacity in the initial cycle and boost the energy density of SIBs and SICs. Their cyclic stability can also be enhanced by the slow release of supplemental sodium and high-content recyclable ions during cycling. In this review, a general understanding of the sodium-ion loss pathways and presodiation process towards full cells with high Coulombic efficiency is summarized. From the perspectives of safety, operability and efficiency, the merits and drawbacks of various presodiation techniques are evaluated. This review attempts to provide a fundamental understanding of presodiation principles and strategies to promote the industrial development of SIBs and SICs.