Ruopian Fang

Aqueous batteries show great promise for large-scale applications owing to their low-cost, eco-friendliness, and non-flammability. However, their practicability in cold regions is hindered by electrolyte freezing and slow ion-transfer kinetics at sub-zero temperatures. In this study, we report the stable operation of aqueous batteries at sub-zero temperature by integrating high-efficiency photothermal current collectors with suspension electrodes. The Ketjen black-based photothermal current collectors can convert a broad spectrum of sunlight (98%, 200-2500 nm) into thermal energy, facilitating rapid heat generation. Concurrently, the high thermal conductivity of the suspension electrode enables fast dissemination of thermal energy throughout the battery. This configuration allows the cell’s core temperature to rapidly rise from −18°C to 20°C within 22 minutes under simulated solar irradiation. An integrated light concentrator and temperature regulation system is further developed to improve heating rates and ensure temperature stability of the cell under diverse climatic conditions. Consequently, the cell can maintain a stable temperature of 20°C throughout consecutive charge/discharge cycles under a fluctuating ambient temperature between −5°C to 5°C. This integrated photothermal battery design exhibits great potential for cold weather conditions, paving the way for the deployment of large-scale aqueous battery systems in polar areas.

Lithium (Li) metal anode have shown exceptional potential for high-energy batteries. However, practical cell-level energy density of Li metal batteries is usually limited by the low areal capacity (6 mAh cm ⁻² ). Such atomic-to-macroscopic trans-scale design is rationalized by quantifying the degradation dynamics of Li metal anodes. High-energy Li metal cells are prototyped under realistic conditions with high cathode capacity (>4 mAh cm ⁻² ), low negative-to-positive electrode capacity ratio (1:1), and low electrolyte-to-capacity ratio (5 g Ah ⁻¹ ), which shed light on a promising move toward practical Li metal batteries.

With its earth abundance and two-electron-transfer reaction mechanism, sulfur has been driving the rapid growth of metal–sulfur batteries. The practical performance of metal–sulfur batteries, however, is restricted by the notorious electrode processes of sulfur (such as low conductivity, intermediate loss, mass crossover, etc.). Sulfur conversion reactions can be stabilized and promoted through a surface immobilization strategy via physical confinement and chemical adsorption effects. As an emerging method in the field, covalent-bonding sulfur materials have demonstrated promise for metal–sulfur batteries. The covalent fixing of sulfur reinforces the molecular interactions between sulfur and the cathode matrix at the bulk level. In this review, we attempt to address the covalent fixing concept on the basis of the emerging studies related to covalent sulfur-containing compounds and composites in various rechargeable metal–sulfur batteries. Firstly, we briefly discuss the classification of sulfur fixing strategies and identify the uniqueness of covalently stabilized sulfur for metal–sulfur batteries. Secondly, we summarize the state-of-the-art covalent sulfur-based materials as well as their synthetic chemistry. Thirdly, we focus on lithium–sulfur batteries that feature cathodes with covalent sulfur active materials, including reaction mechanisms and material innovations. Advances in alternative alkaline metal–sulfur battery systems (sodium–sulfur and potassium–sulfur) involving covalent fixing of sulfur are also discussed. Finally, the prospective opportunities of applying the covalent fixing strategy to optimize the sulfur redox process are commented on. This contribution is anticipated to place the covalent fixing of sulfur into the spotlight and to encourage more efforts in this challenging cross-disciplinary area of organic/polymer chemistry, materials science, electrochemistry and energy technologies.

Lithium-sulfur (Li-S) batteries are highly appealing for the next-generation of energy storage because of their high energy density and low-cost features. However, the practical implementation of Li-S batteries has been hindered by fast performance degradation of the sulfur cathode, especially at a high cathode loading. Here, we propose a strategic design of binary graphene foam (BGF) as the cathode scaffold, with the incorporation of nitrogen-doped graphene and highly porous graphene. The nitrogen-doped graphene provides chemical adsorption sites for migrating polysulfides, and the highly porous graphene could increase the cathode conductivity and accelerate lithium ion transport. The freestanding foam-like cathode structure further offers a robust, interconnected, conductive framework to promote the redox reaction even at a high cathode loading. Therefore, the Li-S battery with the S/BGF electrode exhibits a high specific areal capacity over 10 mAh cm^–2 and good cycling stability over 300 cycles. This approach offers insights into multifunctional electrode structure design, with targeted functions for high-performance Li-S batteries.

Solid polymer electrolytes are of rapidly increasing importance for the research and development of future safe batteries with high energy density. The diversified chemistry and structures of polymers allow the utilization of a wide range of soft structures for all‐polymer solid‐state electrolytes. With equal importance is the hybrid solid‐state electrolytes consisting of both “soft” polymeric structure and “hard” inorganic nanofillers. The recent emergence of the re‐discovery of many two‐dimensional layered materials has stimulated the booming of advanced research in energy storage fields, such as batteries, supercapacitors, and fuel cells. Of special interest is the mass transport properties of these 2D nanostructures for water, gas, or ions. This review aims at the current progress and prospective development of hybrid polymer‐inorganic solid electrolytes based on important 2D materials, including natural clay and synthetic lamellar structures. The ion conduction mechanism and the fabrication, property and device performance of these hybrid solid electrolytes will be discussed.