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Sodium‐metal batteries (SMBs) are regarded as key for next‐generation energy storage due to their high theoretical energy and potential cost‐effectiveness. However, Na‐metal systems remain challenged by several factors, including uncontrollable metallic dendrite growth for liquid systems and unstable solid electrolyte interphase (SEI) with most organic electrolytes, which limit the feasibility of SMBs. Here, the authors detail the interrelated degradation mechanisms. Afterward, the recent advances in improving the electrochemical performance of SMBs are highlighted. The strategies can be subdivided into the following taxonomy: The utilization of three‐dimensional (3D) conductive skeletons; the introduction of protective layers; the development of compatible electrolyte systems; and the employment of alloy anodes. Designing deposition substrates for the "'hostless"' Na has a great effect on reducing the current density and buffering the plating‐stripping volume expansion. The artificial interface approach would introduce efficient mechanical modulus or film‐forming type barriers, which can inhibit detrimental parasitic reactions. Improved solvent‐electrolyte combinations and additives tailored for Na will promise to suppress Na dendrite growth by obtaining a more stable SEI. The formation of alloy phase with Na can tune the bulk properties of the metal per se. Finally, the research challenges and possible development directions of SMBs are also discussed. [ABSTRACT FROM AUTHOR]

High‐performance lithium‐ion batteries (LIBs) are required for the rising energy storage demand, while their development depends mainly on cathode materials. Vanadium‐based compounds are considered to be promising due to the feasibility of multielectron reactions arising from the rich valence states of vanadium (+2 to +5). Herein, for the first time the electrochemical properties of a vanadium‐based fluoroxide, β‐KVOF3, as a cathode for LIBs, are reported. After optimization, a reversible capacity as high as 274 mAh g−1, a stable 300 cycles lifetime, and an energy density comparable to LiFePO4 (650 vs 550 Wh kg−1) are achieved. Experiments and simulation study of reaction mechanism illustrate that such performance originates from the reversible V3+/V5+ redox reaction, high structural stability of β‐KVOF3, and the pseudocapacitive process during charging and discharging. This study reveals that β‐KVOF3 is a promising cathode for Li‐ion storage and provides a new design idea for developing high‐performance LIBs cathode materials. [ABSTRACT FROM AUTHOR]

Low‐cost electrochemical energy storage systems (EESSs) are urgently needed to promote the application of renewable energy sources such as wind and solar energy. In analogy to lithium‐ion batteries, the cost of EESSs depends mainly on charge‐carrier ions and redox centers in electrodes, and their performance is limited by positive electrodes. In this context, this Minireview evaluates several EESS candidates and summarizes the known mixed polyanionic compounds (MPCs)—a family with robust frameworks and large channels for ion storage and migration. After comprehensive analysis, it is pointed out that a deeper exploration of MPCs may generate numerous novel crystallographically interesting compounds and excellent cathode materials for low‐cost energy storage applications. [ABSTRACT FROM AUTHOR]

Potassium-ion batteries are a compelling technology for large scale energy storage due to their low-cost and good rate performance. However, the development of potassium-ion batteries remains in its infancy, mainly hindered by the lack of suitable cathode materials. Here we show that a previously known frustrated magnet, KFeC2O4F, could serve as a stable cathode for potassium ion storage, delivering a discharge capacity of ~112 mAh g−1 at 0.2 A g−1 and 94% capacity retention after 2000 cycles. The unprecedented cycling stability is attributed to the rigid framework and the presence of three channels that allow for minimized volume fluctuation when Fe2+/Fe3+ redox reaction occurs. Further, pairing this KFeC2O4F cathode with a soft carbon anode yields a potassium-ion full cell with an energy density of ~235 Wh kg−1, impressive rate performance and negligible capacity decay within 200 cycles. This work sheds light on the development of low-cost and high-performance K-based energy storage devices. The abundance and low cost of potassium makes potassium batteries a promising technology for large scale energy storage. Here the authors apply a previously known frustrated magnet, KFeC2O4F, as the cathode in which the unique structure and Fe2+/Fe3+ redox enable excellent cycling stability. [ABSTRACT FROM AUTHOR]

Ca‐ion based devices are promising candidates for next‐generation energy storage with high performance and low cost, thanks to its multielectrons, superior kinetics, as well as abundance (2500 times lithium). Because of the lack of an appropriate combination of suitable electrode materials and electrolytes, it is unsuccessful to attain a satisfactory performance on complete Ca‐ion energy storage devices. Here, the multiion reaction strategy is defined to construct a complete Ca‐ion energy storage device and a capacitor–battery hybrid mechanism is deliberately adopted. Profiting from the elaborate design, it exhibits a high reversible capacity of 92 mAh g−1, unmatchable rate capability, and a high capacity retention of 84% over 1000 cycles under room temperature, which is the best performance of reported Ca‐based energy storage devices. [ABSTRACT FROM AUTHOR]

Due to the shortage of lithium resources, current lithium-ion batteries are difficult to meet the growing demand for energy storage in the long run. Rechargeable aqueous aluminum ion (Al3+) electrochemistry has the advantages of abundant resources, high safety, environmental friendliness, and high energy/power density. It is, therefore an ideal choice for alternative energy storage devices. However, Al3+-based technology is still in the preliminary stage, and there are various challenges. In reality, its kinetics and reversibility have long been disturbed by the strong electrostatic field of Al3+ and the parasitic side reactions of aqueous electrolytes. This paper first summarizes the history of aqueous aluminum ion batteries/capacitors (AAIBs/AAICs) and analyzes the challenges faced by cathode, anode, and electrolyte. Then, the state-of-the-art research progress, design strategies, and limitations of the cathode, anode, electrolyte, and Al3+-based energy storage devices are comprehensively introduced, and their structure, performance, and reaction mechanisms are discussed. Finally, the future design of AAIBs/AAICs with long life, high reversibility, and high energy/power density has been prospected, and promising research directions are pointed out. [ABSTRACT FROM AUTHOR]