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A supercapacitor is a potential electrochemical energy storage device with high‐power density (PD) for driving flexible, smart, electronic devices. In particular, flexible supercapacitors (FSCs) have reliable mechanical and electrochemical properties and have become an important part of wearable, smart, electronic devices. It is noteworthy that the flexible electrode, electrolyte, separator and current collector all play key roles in overall FSCs. In this review, the unique mechanical properties, structural designs and fabrication methods of each flexible component are systematically classified, summarized and discussed based on the recent progress of FSCs. Further, the practical applications of FSCs are delineated, and the opportunities and challenges of FSCs in wearable technologies are proposed. The development of high‐performance FSCs will greatly promote electricity storage toward more practical and widely varying fields. However, with the development of portable equipment, simple FSCs cannot satisfy the needs of integrated and intelligent flexible wearable devices for long durations. It is anticipated that the combining an FSC and a flexible power source such as flexible solar cells is an effective strategy to solve this problem. This review also includes some discussions of flexible self‐powered devices. In this review, the unique mechanical properties, structural designs, and fabrication methods of each flexible component are systematically classified, summarized, and discussed based on the recent progress of flexible supercapacitors (FSCs). Further, the practical applications of FSCs are delineated, and the opportunities and challenges of FSCs in wearable technologies are proposed.

Sodium metal batteries are considered one of the most promising low-cost high-energy-density electrochemical energy storage systems. However, the growth of unfavourable Na metal deposition and the limited cell cycle life hamper the application of this battery system at a large scale. Here, we propose the use of polypropylene separator coated with a composite material comprising polydopamine and multilayer graphene to tackle these issues. The oxygen- and nitrogen- containing moieties as well as the nano- and meso- porous network of the coating allow cycling of Na metal electrodes in symmetric cell configuration for over 2000 h with a stable 4 mV overpotential at 1 mA cm −2 . When tested in full Na || Na 3 V 2 (PO 4 ) 3 coin cell, the coated separator enables the delivery of a stable capacity of about 100 mAh g −1 for 500 cycles (90% capacity retention) at a specific current of 235 mA g −1 and satisfactory rate capability performances (i.e., 75 mAh g −1 at 3.5 A g −1 ). The development of future Na metal batteries relies on the cycling stability of the metallic anode. Here, the authors propose a polypropylene separator functionalized with polydopamine and multilayer graphene to enable stable and prolonged Na metal cell cycling.

Micro-supercapacitors are important on-chip micro-power sources for miniaturized electronic devices. Although the performance of micro-supercapacitors has been significantly advanced by fabricating nanostructured materials, developing thin-film manufacture technologies and device architectures, their power or energy densities remain far from those of electrolytic capacitors or lithium thin-film batteries. Here we demonstrate graphene-based in-plane interdigital micro-supercapacitors on arbitrary substrates. The resulting micro-supercapacitors deliver an area capacitance of 80.7 μF cm −2 and a stack capacitance of 17.9 F cm −3 . Further, they show a power density of 495 W cm −3 that is higher than electrolytic capacitors, and an energy density of 2.5 mWh cm −3 that is comparable to lithium thin-film batteries, in association with superior cycling stability. Such microdevices allow for operations at ultrahigh rate up to 1,000 V s −1 , three orders of magnitude higher than that of conventional supercapacitors. Micro-supercapacitors with an in-plane geometry have great promise for numerous miniaturized or flexible electronic applications. Micro-supercapacitors offer the advantage of high power density over lithium batteries and high energy density over electric capacitors, but integration of these advantages is yet to be achieved. Wu et al . develop a graphene-based in-plane micro-supercapacitor with ultrahigh power and energy densities.

Exploring durable electrocatalysts with high activity for oxygen evolution reaction (OER) in acidic media is of paramount importance for H 2 production via polymer electrolyte membrane electrolyzers, yet it remains urgently challenging. Herein, we report a synergistic strategy of Rh doping and surface oxygen vacancies to precisely regulate unconventional OER reaction path via the Ru–O–Rh active sites of Rh-RuO 2 , simultaneously boosting intrinsic activity and stability. The stabilized low-valent catalyst exhibits a remarkable performance, with an overpotential of 161 mV at 10 mA cm −2 and activity retention of 99.2% exceeding 700 h at 50 mA cm −2 . Quasi in situ/operando characterizations demonstrate the recurrence of reversible oxygen species under working potentials for enhanced activity and durability. It is theoretically revealed that Rh-RuO 2 passes through a more optimal reaction path of lattice oxygen mediated mechanism-oxygen vacancy site mechanism induced by the synergistic interaction of defects and Ru–O–Rh active sites with the rate-determining step of *O formation, breaking the barrier limitation (*OOH) of the traditional adsorption evolution mechanism. Exploring highly active and durable Ru-based electrocatalysts for acidic water oxidation is challenging. Here authors reported an ion-exchange adsorption strategy to regulate oxygen vacancies and Rh dopant, with a corresponding fundamental investigation on the lattice oxygen oxidation and the oxygen vacancy site.

MXene is rising as a versatile two-dimensional material (2DM) for electrochemical energy storage devices. MXene has boosted the performance of supercapacitors thanks to its pseudocapacitive charge storage mechanism with electric double layer behavior. Further, MXene has helped batteries achieve high capacity while endowing fast charge-discharge by virtue of its suitable interlayer spacing and unique chemistry. Such achievements are a result of MXene's intrinsic properties like high electrical conductivity, defined layered structure and ability to sustain customizations, tailoring the electrodes towards a specific target. Not only that, MXene has showcased its merits by enabling supercapacitors and batteries to surpass the convention and venture into the territory of micro-supercapacitors (MSCs), hybrid capacitors and batteries beyond Li-ion. Herein, we present a topical review discussing the present status of MXene-based energy storage devices and corresponding challenges. By rational analysis, we also provide some key avenues for further research that may help overcome these shortcomings and enable this family of MXene materials attain its full potential.

Single‐atom catalysts (SACs) are efficient for maximizing electrocatalytic activity, but have unsatisfactory activity for the oxygen evolution reaction (OER). Herein, the NaCl template synthesis of individual nickel (Ni) SACs is reported, bonded to oxygen sites on graphene‐like carbon (denoted as Ni‐O‐G SACs) with superior activity and stability for OER. A variety of characterizations unveil that the Ni‐O‐G SACs present 3D porous framework constructed by ultrathin graphene sheets, single Ni atoms, coordinating nickel atoms to oxygen. Consequently, the catalysts are active and robust for OER with extremely low overpotential of 224 mV at current density of 10 mA cm−2, 42 mV dec−1 Tafel slope, oxygen production turn over frequency of 1.44 S−1 at 300 mV, and long‐term durability without significant degradation for 50 h at exceptionally high current of 115 mA cm−1, outperforming the state‐of‐the‐art OER SACs. A theoretical simulation further reveals that the bonding between single nickel and oxygen sites results in the extraordinary boosting of OER performance of Ni‐O‐G SACs. Therefore, this work opens numerous opportunities for creating unconventional SACs via metal–oxygen bonding. Nickel single‐atom catalysts bonded to oxygen sites on graphene‐like carbon nanosheets are synthesized as extraordinarily active and durable electrocatalysts for the oxygen evolution reaction, showing the oxygen production turn over frequency of 1.44 S−1 at 300 mV, and low overpotential of 224 mV at current density of 10 mA cm−2.

In response to the imperative of climate change, global governments are steering energy systems towards sustainability. However, this transition encounters challenges from climate, geopolitical, and economic factors. Decision-makers must craft adaptive policies to address these complexities. This study proposes a method, utilizing the Energy Trilemma Index, to adjust energy goals and policies. Drawing on World Energy Council data spanning 2000 to 2022 for 124 countries, the Analytic Hierarchy Process refines policies at strategic, indicator, and operational levels. Using China as a case study, the study recommends that decision-makers prioritize environmental investment, equitable resource distribution, and strengthened energy security.

Wireless millimeter-scale origami robots have recently been explored with great potential for biomedical applications. Existing millimeter-scale origami devices usually require separate geometrical components for locomotion and functions. Additionally, none of them can achieve both on-ground and in-water locomotion. Here we report a magnetically actuated amphibious origami millirobot that integrates capabilities of spinning-enabled multimodal locomotion, delivery of liquid medicine, and cargo transportation with wireless operation. This millirobot takes full advantage of the geometrical features and folding/unfolding capability of Kresling origami, a triangulated hollow cylinder, to fulfill multifunction: its geometrical features are exploited for generating omnidirectional locomotion in various working environments through rolling, flipping, and spinning-induced propulsion; the folding/unfolding is utilized as a pumping mechanism for controlled delivery of liquid medicine; furthermore, the spinning motion provides a sucking mechanism for targeted solid cargo transportation. We anticipate the amphibious origami millirobots can potentially serve as minimally invasive devices for biomedical diagnoses and treatments. Wireless millirobots are promising as minimally invasive biomedical devices. Here, the authors design a magnetically actuated amphibious millirobot that integrates spinning-enabled locomotion, targeted drug delivery, and cargo transportation by utilizing geometrical features and folding/unfolding capability of the Kresling origami.

Sulfurized polyacrylonitrile (SPAN) with a “solid‐solid” conversion mechanism in carbonated‐based electrolyte eradicating the polysulfides shutting issue is considered as an ideal cathode for stabilizing lithium–sulfur (Li‐S) batteries. However, the sluggish reaction kinetics and less sulfur content of the SPAN limit its practical application. Herein, the MoS2 doped SPAN (MoS2@SPAN) is demonstrated to rapidly accelerate the solid–solid conversion kinetics of SPAN for remarkably boosting high‐power and long‐life Li‐S batteries. Benefitting from the accelerated lithium‐ion (Li+) transfer rate, a fast ion transport channel and enhanced redox reaction kinetics of sulfur to Li2S2/Li2S is realized via MoS2 catalysis, and excellent electrochemical performance is achieved. Consequently, MoS2@SPAN delivers a high capacity of 626 mAh g−1 at 0.1 A g−1, and simultaneously shows ultralong cycling life of 500 cycles with only 0.089% capacity decay rate at 2 A g−1. Moreover, a superb capacity of 321 mAh g−1 at ultrahigh current density of 5 A g−1 is offered, outperforming most of the reported SPAN cathodes. This work provides a general and reliable strategy on the reliable design of SPAN cathode for high‐rate and long‐term Li‐S batteries. A MoS2 doped sulfurized polyacrylonitrile is designed to rapidly accelerate the solid‐solid conversion kinetics of sulfurized polyacrylonitrile for remarkably boosting high‐power and long‐life Li‐S batteries.

Zinc‐based batteries are a very promising class of next‐generation electrochemical energy storage systems, with high safety, eco‐friendliness, abundant resources, and the absence of rigorous manufacturing conditions. However, practical applications of zinc‐based rechargeable batteries are impeded by the low Coulombic efficiency, inferior cyclability, and poor rate capability, due to the instability of zinc anode. Herein, effective strategies for dendrite‐free zinc anode are symmetrically reviewed, especially highlighting specific mechanisms, delicate design of electrode and current collectors, controlled electrode|electrolyte interface, ameliorative electrolytes, and advanced separators design. First, the particular mechanisms of dendrites formation and the associated fundamentals of the stable Zn metal anodes are presented elaborately. Then, recent key strategies for dendrites prevention and hydrogen evolution reaction suppression are categorized, discussed, and analyzed in detail in view of the electrodes, electrolytes, and separators. Finally, the challenging perspectives and major directions of stable zinc anodes are briefly discussed for further industrialization and commercialization of zinc‐based rechargeable batteries. The fundamentals and key strategies of dendrite‐free stable zinc anodes for zinc‐based batteries are summarized symmetrically to address the issues of dendrites formation, severe hydrogen evolution reaction, and other side reactions, through elaborated electrode structure design, decorated separators, ameliorative electrolytes, and electrode|electrolyte interface. The key challenges and future perspectives are proposed with the goal of pursuing high performance and future industrialization.