Lithium-ion batteries (LIBs) with high energy density are widely applied in portable electronics, electric automobiles, largescale energy grids, and other fields owing to the increasing demand for energy storage technologies. The commonly used insertiontype cathodes show small theoretical specific capacities, which has limited the rapid development of electric vehicles and smart grids. [1][2][3][4] Recently, lithium-sulfur (LiS) batteries with their theoretical energy density and specific capacity of 2600 Wh kg −1 and 1672 mAh g −1 have attracted much attention due to their potential to meet the requirements of practical applications. [5][6][7][8][9] In addition, elemental sulfur is abundant on the earth, non-toxic, and low in price. [10] Therefore, LiS batteries have great commercial value and are recognized as one of the most promising next-generation high-energy-density secondary batteries.Despite their advantages of high theoretical energy density and low cost, LiS batteries also face a series of obstacles, such as the intrinsic electronic/ionic insulating properties of sulfur and lithium polysulfides (LiPS), the inevitable shuttle effect of LiPS, large volume expansion, and the growth and pulverization of lithium dendrites as well. These issues seriously affect the electrochemical performance and reduce the actual energy density of LiS batteries. [11][12][13][14] To overcome the above challenges, many efforts have been devoted to the rational design of sulfur hosts, for instance, introducing conductive carbon/polymer composites or transition metal oxides/sulfides (TMOs/TMSs) as the sulfur hosts to promote their electrochemical redox kinetics. Based on these strategies, great success has been achieved, and some of them have even reached theoretical values. Nonetheless, it should be noted that LiS batteries with these well-established sulfur cathodes are usually evaluated under ideal conditions, especially with a low sulfur loading of less than 2 mg cm −2 and excess electrolyte. Hence, the actual energy density of the LiS batteries cannot reach the theoretical value or even catch up with the energy density of commercial LIBs. Therefore, the low actual energy density is still a major obstacle and needs to be solved urgently for the future commercialization of LiS batteries.To meet the demand for high energy density in LiS batteries, various aspects, including sulfur loading, the Lithium-sulfur batteries hold great potential for next-generation energy storage systems, due to their high theoretical energy density and the natural abundance of sulfur. Although much progress has been achieved recently, the low actual energy density of LiS batteries is still the key challenge in implementing their practical applications. Because the energy density greatly depends on the areal capacity of their sulfur cathodes, the sulfur content and sulfur loading play an important role in meeting the conditions necessary for practical applications. Therefore, escalating the areal capacity of sulfur cathodes is essential to ...

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The applications of alloy‐type anode materials for Na‐ion batteries are always obstructed by enormous volume variation upon cycles. Here, K+ ions are introduced as an electrolyte additive to improve the electrochemical performance via electrostatic shielding, using Sn microparticles (μ‐Sn) as a model. Theoretical calculations and experimental results indicate that K+ ions are not incorporated in the electrode, but accumulate on some sites. This accumulation slows down the local sodiation at the “hot spots”, promotes the uniform sodiation and enhances the electrode stability. Therefore, the electrode maintains a high specific capacity of 565 mAh g−1 after 3000 cycles at 2 A g−1, much better than the case without K+. The electrode also remains an areal capacity of ≈3.5 mAh cm−2 after 100 cycles. This method does not involve time‐consuming preparation, sophisticated instruments and expensive reagents, exhibiting the promising potential for other anode materials.

Aqueous Zn‐ion batteries (AZIBs) have attracted much attention due to their excellent safety, cost‐effectiveness, and eco‐friendliness thereby being considered as one of the most promising candidates for large‐scale energy storage. Zn metal anodes with a high gravimetric/volumetric capacity are indispensable for advanced AZIBs. However, pristine Zn metal anodes encounter severe challenges in achieving adequate cycling stability, including dendrite growth, hydrogen evolution reaction, self‐corrosion, and by‐product formation. Because all these reactions are closely related to the electrolyte/Zn interface, the subtle interface engineering is important. Many strategies targeted to the interface engineering have been developed. In this review, a timely update on these strategies and perspectives are summarized, especially focusing on the controllable synthesis of Zn, Zn surface engineering, electrolyte formulation, and separator design. Furthermore, the corresponding internal principles of these strategies are clarified, which is helpful to help seek for new strategies. Finally, the challenges and perspectives for the future development of practical AZIBs are discussed, including the conducting of in advanced in situ testing, unification of battery models, some boundary issues, etc. This review is expected to guide the future development and provi beacon light direction for aqueous zinc ion batteries.

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