• Energy Research

High-temperature structural materials face severe degradation challenges due to oxidation and corrosion, leading to reduced long-term stability and performance. This review comprehensively examines the interfacial migration mechanisms of reactive elements (REs) such as Ti, Al, and Cr in Ni/Fe-based alloys, emphasizing their role in forming and stabilizing protective oxide layers. We discuss how these oxide layers impede ion migration and mitigate environmental degradation. Key findings highlight the importance of selective oxidation, oxide layer healing, and the integration of novel alloying elements to enhance resistance under ultra-supercritical conditions. Advanced insights into grain boundary engineering, alloy design strategies, and quantum approaches to understanding charge transport at passive interfaces are also presented. These findings provide a foundation for developing next-generation high-temperature alloys with improved degradation resistance tailored to withstand extreme environmental conditions.

Solid electrolytes (SEs) are promising candidates for enhancing the energy density and safety of conventional lithium-ion batteries. Recently, lithium thioantimonate iodide argyrodites have been regarded as promising SEs because of their high ionic conductivities and air-stability. In this study, we utilized high-energy ball milling to synthesize Ge-substituted thioantimonate argyrodites and achieved an ionic conductivity of 16.1 mS cm –1 for Li 6.5 Sb 0.5 Ge 0.5 S 5 I, which is the highest value among the reported cold-pressed SE pellets. First-principles calculations reveal that concerted Li-ion migrations through the inter-cage paths substantially improve the ionic conductivity. Li 6.5 Sb 0.5 Ge 0.5 S 5 I shows good compatibility with LiNi 0.5 Co 0.2 Mn 0.3 O 2 -based all-solid-state batteries (ASSBs) after applying Li 3 YCl 6 as a catholyte, which exhibits a high discharge capacity of 164 mAh g –1 and good cycle stability. Ge-substituted thioantimonate argyrodites exhibit excellent air-stability, which facilitates reducing the synthesis and fabrication costs of ASSBs with hygroscopic P-based sulfide SEs. The superionic conductors with high air-stability reported in this study demonstrate substantial promise for the development of ASSBs.

Hybrid supercapacitors (HSCs) have garnered growing interest for their ability to combine the high energy storage capability of batteries with the rapid charge–discharge characteristics of supercapacitors. This review examines the evolution of HSCs, emphasizing the synergistic mechanisms that integrate both Faradaic and non-Faradaic charge storage processes. Transition metal oxides (TMOs) are highlighted as promising battery-type electrodes owing to their notable energy storage potential and compatibility with various synthesis routes, including hydro/solvothermal methods, electrospinning, electrodeposition, and sol–gel processes. Particular attention is directed toward Ti-, Co-, and V-based TMOs, with a focus on tailoring their properties through morphology control, composite formation, and doping to enhance electrochemical performance. Overall, the discussion underscores the potential of HSCs to meet the growing demand for next-generation energy storage systems by bridging the gap between high energy and high power requirements.

Grid-scale energy storage applications can benefit from rechargeable sodium-ion batteries. As a potential material for making non-cobalt, nickel-free, cost-effective cathodes, earth-abundant Na2/3Fe1/2Mn1/2O2 is of particular interest. However, Mn3+ ions are particularly susceptible to the Jahn–Teller effect, which can lead to an unstable structure and continuous capacity degradation. Modifying the crystal structure by aliovalent doping is considered an effective strategy to alleviate the Jahn–Teller effect. Using a sol–gel synthesis route followed by heat treatment, we succeeded in preparing an Mg-doped Na2/3Fe1−yMnyO2 cathode. Its electrochemical properties and charge compensation mechanism were then studied using synchrotron-based X-ray absorption spectroscopy and in situ X-ray diffraction techniques. The results revealed that Mg doping reduced the number of Mn3+ Jahn–Teller centers and alleviated high voltage phase transition. However, Mg doping was unable to suppress the P2-P’2 phase transition at a low voltage discharge. An initial discharge capacity of about 196 mAh g−1 was obtained at a current density of 20 mAh g−1, and 60% of rate capability was maintained at a current density of 200 mAh g−1 in a voltage range of 1.5–4.3 V. This study will greatly contribute to the ongoing search for advanced and efficient cathodes from earth-abundant elements for rechargeable sodium-ion batteries operable at room temperature.

Abstract Structural changes and their relationship with thermal stability of charged Li 0.33 Ni 1/3 Co 1/3 Mn 1/3 O 2 cathode samples have been studied using time-resolved X-ray diffraction (TR-XRD) in a wide temperature from 25 to 600 °C with and without the presence of electrolyte in comparison with Li 0.27 Ni 0.8 Co 0.15 Al 0.05 O 2 cathodes. Unique phase transition behavior during heating is found for the Li 0.33 Ni 1/3 Co 1/3 Mn 1/3 O 2 cathode samples: when no electrolyte is present, the initial layered structure changes first to a LiM 2 O 4 -type spinel, and then to a M 3 O 4 -type spinel and remains in this structure up to 600 °C. For the Li 0.33 Ni 1/3 Co 1/3 Mn 1/3 O 2 cathode sample with electrolyte, additional phase transition from the M 3 O 4 -type spinel to the MO-type rock salt phase takes place from about 400 to 441 °C together with the formation of metallic phase at about 460 °C. The major difference between this type of phase transitions and that for Li 0.27 Ni 0.8 Co 0.15 Al 0.05 O 2 in the presence of electrolyte is the delayed phase transition from the spinel-type to the rock salt-type phase by stretching the temperature range of spinel phases from about 20 to 140 °C. This unique behavior is considered as the key factor of the better thermal stability of the Li 1−x Ni 1/3 Co 1/3 Mn 1/3 O 2 cathode materials.

GNM electrodes exhibit superior electrochemical properties.

Gels are attracting materials for energy storage technologies. The strategic development of hydrogels with enhanced physicochemical properties, such as superior mechanical strength, flexibility, and charge transport capabilities, introduces novel prospects for advancing next-generation batteries, fuel cells, and supercapacitors. Through a refined comprehension of gelation chemistry, researchers have achieved notable progress in fabricating hydrogels endowed with stimuli-responsive, self-healing, and highly stretchable characteristics. This mini-review delineates the integration of hydrogels into batteries, fuel cells, and supercapacitors, showcasing compelling instances that underscore the versatility of hydrogels, including tailorable architectures, conductive nanostructures, 3D frameworks, and multifunctionalities. The ongoing application of creative and combinatorial approaches in functional hydrogel design is poised to yield materials with immense potential within the domain of energy storage.

Li-rich layered oxides utilizing reversible oxygen redox are promising cathodes for high-energy-density lithium-ion batteries. However, they exhibit different electrochemical profiles before and after oxygen redox activation. Therefore, advanced characterization techniques have been developed to explore the fundamental understanding underlying their unusual phenomenon, such as the redox evolution of these materials. In this review, we present the general redox evolution of Li-rich layered cathodes upon activation of reversible oxygen redox. Various synchrotron X-ray spectroscopy methods which can identify charge compensation by cations and anions are summarized. The case-by-case redox evolution processes of Li-rich 3d/4d/5d transition metal O3 type layered cathodes are discussed. We highlight that not only the type of transition metals but also the composition of transition metals strongly affects redox behavior. We propose further studies on the fundamental understanding of cationic and anionic redox mixing and the effect of transition metals on redox behavior to excite the full energy potential of Li-rich layered cathodes.