Ultrafast Synthesis of Metal-Layered Hydroxides in a Dozen Seconds for High-Performance Aqueous Zn (Micro-) Battery

Synergistic Microstructure-driven Polarization and Conductive Loss in 3D Chrysanthemum-like MoC@NiCo LDH Composite for Ultra-high Microwave Absorption Performance

The development of efficient electromagnetic wave (EMW) absorbing materials relies on rational microstructures and loss mechanisms. This study innovatively proposes a design strategy based on micronano structural regulation─heterogeneous interface construction─synergistic loss optimization and fabricates a MoC@NiCo layered double hydroxide (LDH) composite material with a 3D chrysanthemum-like morphology. The petal-like microstructure enhances the multiple reflection and scattering effects of the incident EMWs, while heterogeneous interfaces further stimulate interface polarization. Meanwhile, density functional theory (DFT) guides the regulation of polarization and conduction loss synergy for efficient EMW energy attenuation. Experimental results show that the composite material, with a thickness of only 2.4 mm, has a minimum reflection loss (RLmin) of -57.9 dB, and an maximum effective absorption bandwidth (EABmax) covering 5.4 GHz, encompassing the entire C, X, and Ku frequency bands. Radar cross-sectional (RCS) testing further verifies the potential of the material to effectively attenuate EMWs in practical applications. This study provides theoretical basis and method guidance for the efficient design of absorbing materials through the synergistic regulation of polarization loss and conductivity loss and lays a theoretical foundation for the further design of EMW absorbing materials that meet more stringent practical application requirements.

Photolithographic Microfabrication of Microbatteries for On-Chip Energy Storage

Microbatteries (MBs) are crucial to power miniaturized devices for the Internet of Things. In the evolutionary journey of MBs, fabrication technology emerges as the cornerstone, guiding the intricacies of their configuration designs, ensuring precision, and facilitating scalability for mass production. Photolithography stands out as an ideal technology, leveraging its unparalleled resolution, exceptional design flexibility, and entrenched position within the mature semiconductor industry. However, comprehensive reviews on its application in MB development remain scarce. This review aims to bridge that gap by thoroughly assessing the recent status and promising prospects of photolithographic microfabrication for MBs. Firstly, we delve into the fundamental principles and step-by-step procedures of photolithography, offering a nuanced understanding of its operational mechanisms and the criteria for photoresist selection. Subsequently, we highlighted the specific roles of photolithography in the fabrication of MBs, including its utilization as a template for creating miniaturized micropatterns, a protective layer during the etching process, a mold for soft lithography, a constituent of MB active component, and a sacrificial layer in the construction of micro-Swiss-roll structure. Finally, the review concludes with a summary of the key challenges and future perspectives of MBs fabricated by photolithography, providing comprehensive insights and sparking research inspiration in this field.

Tailoring hierarchical MnO2 nanostructures on self-supporting cathodes for high-mass-loading zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) with MnO2 cathodes have promising application prospects; however, their performance is hindered by their low efficiency and insufficient life. By leveraging the nanomicellar properties of cetyltrimethylammonium bromide (CTAB), a hierarchical δ-MnO2 with 2D/3D structure was directionally grown on a modified carbon cloth (CC) collector for realizing high-mass-loading AZIBs. Experimental results reveal the synergistic effects of micro/nano hierarchically structured MnO2-CC heterointerfaces in accelerating the electron migration and transfer rate of Zn2+/H+. Functioning as a conductive skeleton and flexible substrate, CC efficiently improves the reaction kinetics and buffers the interfacial stress resulting from the structural evolution of MnO2 during the long-term electrode reaction. This phenomenon is investigated using advanced characterisation techniques, including X-ray absorption fine structure spectroscopy, Kelvin probe force microscopy, and theoretical simulations. The fabricated electrode exhibits superior electrochemical properties, such as high capacity (409.6 mA h g-1 at 0.1 A g-1) and reliable cycling performance (with 86.6% capacity retention after 2000 cycles at 1.0 A g-1). Even at a high mass loading of 6.0 mg cm-2, the battery retains 81.8% of its original capacity after 1300 cycles. The proposed interface engineering strategy provides valuable insights into realising high-loading and long-life AZIBs.

Breathable and Stretchable Epidermal Electronics for Health Management: Recent Advances and Challenges

Advanced epidermal electronic devices, capable of real-time monitoring of physical, physiological, and biochemical signals and administering appropriate therapeutics, are revolutionizing personalized healthcare technology. However, conventional portable electronic devices are predominantly constructed from impermeable and rigid materials, which thus leads to the mechanical and biochemical disparities between the devices and human tissues, resulting in skin irritation, tissue damage, compromised signal-to-noise ratio (SNR), and limited operational lifespans. To address these limitations, a new generation of wearable on-skin electronics built on stretchable and porous substrates has emerged. These substrates offer significant advantages including breathability, conformability, biocompatibility, and mechanical robustness, thus providing solutions for the aforementioned challenges. However, given their diverse nature and varying application scenarios, the careful selection and engineering of suitable substrates is paramount when developing high-performance on-skin electronics tailored to specific applications. This comprehensive review begins with an overview of various stretchable porous substrates, specifically focusing on their fundamental design principles, fabrication processes, and practical applications. Subsequently, a concise comparison of various methods is offered to fabricate epidermal electronics by applying these porous substrates. Following these, the latest advancements and applications of these electronics are highlighted. Finally, the current challenges are summarized and potential future directions in this dynamic field are explored.

Interstitial Oxygen Acts as Electronic Buffer Stabilizing High-Entropy Alloys for Trifunctional Electrocatalysis

Understanding the effect of elements' oxygen affinity is essential for comprehending high-entropy alloys' (HEAs) complete properties. However, the origin of HEAs' oxygen-containing structure and stability remains poorly understood, primarily due to their diverse components, hindering synthesis and analysis. Herein, the O-doping HEAs (HEA-O) have demonstrated outstanding performance and stability in electrolyzed water and Zinc-air batteries which can be reassembled after being stable for more than 1600 h when the zinc consumption is over. The experiment and DFT simulation demonstrate that Cr with strong oxygen affinity can introduce more oxygen into the system of HEAs. Consequently, interstitial oxygens act as electronic buffers making the binding energy of other metal elements move to a higher level. Additionally, O-doping lowers the d-band center promoting electrochemical activity and increasing vacancy formation energies of metal active sites leading to super stability. The study provides significant insights into the design and comprehension of interstitial oxygen-doped HEAs.

Realizing the Electrode Engineering Significance Through Porous Organic Framework Materials for High-Capacity Aqueous Zn-Alkaline Battery

Energy storage technologies are eminently developed to address renewable energy utilization efficiently. Porous framework materials possess high surface area and pore volume, allowing for efficient ion transportation and storage. Their unique structure facilitates fast electron transfer, leading to improved battery kinetics. Porous organic framework materials like metal-organic (MOF) and covalent organic (COF) frameworks have immense potential in enhancing the charge/discharge performances of aqueous Zn-alkaline batteries. Organic frameworks and their derivatives can be modified feasibly to exhibit significant chemical stability, enabling them to tolerate the harsh battery environment. Zn-alkaline batteries can achieve enhanced energy density, longer lifespan, and improved rechargeability by incorporating MOFs and COFs, such as electrodes, separators, or electrolyte additives, into the battery architecture. The present review highlights the significant electrode design strategies based on porous framework materials for aqueous Zn-alkaline batteries, such as Zn-Ni, Zn-Mn, Zn-air, and Zn-N2/NO3 batteries. Besides, the discussion on the issues faced by the Zn anode and the essential anode design strategies to solve the issues are also included.

Flash Joule Heating Synthesis of Layer-Stacked Vanadium Oxide/Graphene Hybrids within Seconds for High-Performance Aqueous Zinc-Ion Batteries

Vanadium oxides have been regarded as highly promising cathodes for aqueous zinc-ion batteries (ZIBs). However, obtaining high-performance vanadium oxide-based cathodes suitable for industrial application remains a significant challenge due to the need for cost-effective, straightforward, and efficient preparation methods. Herein, we present a facile and rapid synthesis of a composite cathode, consisting of layer-stacked VO2/V2O5 and graphene-like carbon nanosheets, in just 2.5 s by treating the commercial V2O5 powder via a flash Joule heating strategy. When employed as the cathode for ZIBs, the resulting composite delivers a comparable rate capacity of 459 mA h g-1 at 0.2 A g-1 and remarkable cycle stabilities of 355.5 mA h g-1 after 2500 cycles at 1.0 A g-1 and 169.5 mA h g-1 after 10,000 cycles at 10 A g-1, respectively. Further electrochemical analysis reveals that the impressive performance is attributed to the accelerated charge transfer and the alleviated structure degradation, facilitated by the abundant sites and a built-in electric field of the layer-stacked VO2/V2O5 heterostructure, as well as the excellent conductivity of graphene-like carbon nanosheets. This work introduces a unique approach for ultrafast and low-cost fabrication of high-performance vanadium oxide-based composite cathodes toward efficient ZIBs.

Boosting Zn2+ Storage Kinetics by K-Doping of Sodium Vanadate for Zinc-Ion Batteries

Na5V12O32 is an attractive cathode candidate for aqueous zinc-ion batteries (AZIBs) by virtue of its low-cost and high specific capacity (>300 mAh g-1). However, its intrinsically inferior electronic conductivity and structural instability result in an unfavorable rate performance and cyclability. Herein, K-doped Na5V12O32 (KNVO) was developed to promote its ionic/electronic migration, and thus enhance the Zn2+ storage capability. The as-produced KNVO displays a superior capacity of 353.5 mAh g-1 at 0.1 A g-1 and an excellent retentive capacity of 231.8 mAh g-1 after 1000 cycles at 5 A g-1. Even under a high mass of 5.3 mg cm-2, the KNVO cathode can still maintain a capacity of 220.5 mAh g-1 at 0.1 A g-1 and outstanding cyclability without apparent capacity decay after 2000 cycles. In addition, the Zn2+ storage kinetics of the KNVO cathode is investigated through multiple analyses.

Ni and Co Active Site Transition and Competition in Fluorine-Doped NiCo(OH)2 LDH Electrocatalysts for Oxygen Evolution Reaction

The oxygen evolution reaction (OER) performance of NiCo LDH electrocatalysts can be improved through fluorine doping. The roles of Ni and Co active sites in such catalysts remain ambiguous and controversial. In addressing the issue, this study draws upon the molecular orbital theory and proposes the active center competitive mechanism between Ni and Co. The doped F-atoms can directly impact the valence state of metal atoms or exert an indirect influence through the dehydrogenation, thereby modulating the active center. As the F-atoms are progressively aggregate, the eg orbitals of Ni and Co transition from e2 g to e1 g, and subsequently to e0 g. The corresponding valence state elevates from +2 to +3, and then to +4, signifying an initial increase followed by a subsequent decrease in the electrocatalytic performance. Furthermore, a series of F-NiCo LDH catalysts are synthesized to verify the eg orbital occupancy analysis, and the catalytic OER overpotentials are 303, 243, 240, and 246 mV at the current density of 10 mA cm-2, respectively, which coincides well with the theoretical prediction. This investigation not only provides novel mechanistic insights into the transition and competition of Ni and Co in F-NiCo LDH catalysts but also establishes a foundation for the design of high-performance catalysts.

Controlled three-dimensional leaf-like NiCoO2@NiCo layered double hydroxide heterostructures for oxygen evolution electrocatalysts in rechargeable Zn-air batteries

Rechargeable zinc-air batteries (ZABs) have garnered attention as a viable choice for large-scale energy storage due to their advantageous characteristics, such as high energy density and cost-effectiveness. Strategies aimed at improving the kinetics of the oxygen evolution reaction (OER) through advanced electrocatalytic materials or structural designs can significantly enhance the efficiency and longevity of ZABs. In this study, we introduce a three-dimensional (3D) leaf-vein system heterojunction architecture. In this structure, NiCoO2 nanowire arrays form the central vein, surrounded by an outer leaf composed of NiCo layered double hydroxide (LDH) nanosheets. All these components are integrated onto a substrate made of Ni foam. Notably, when tested in an alkaline environment, the NiCoO2@NiCo LDH exhibited an overpotential of 272 mV at a current density of 10 mA cm-2, and extended durability evaluations over 12 h underscored its robustness at 99.76 %. The rechargeable ZABs achieved a peak power density of 149 mW cm-2. Furthermore, the NiCoO2@NiCo LDH demonstrated stability by maintaining high round-trip efficiencies throughout more than 680 cycles (equivalent to 340 h) under galvanostatic charge-discharge cycling at 5 mA cm-2. The leaf-vein system heterojunction significantly increased the active sites of the catalysts, facilitating charge transport, improving electronic conductivity, and enhancing overall stability.

Insights into Nano- and Micro-Structured Scaffolds for Advanced Electrochemical Energy Storage

Adopting a nano- and micro-structuring approach to fully unleashing the genuine potential of electrode active material benefits in-depth understandings and research progress toward higher energy density electrochemical energy storage devices at all technology readiness levels. Due to various challenging issues, especially limited stability, nano- and micro-structured (NMS) electrodes undergo fast electrochemical performance degradation. The emerging NMS scaffold design is a pivotal aspect of many electrodes as it endows them with both robustness and electrochemical performance enhancement, even though it only occupies complementary and facilitating components for the main mechanism. However, extensive efforts are urgently needed toward optimizing the stereoscopic geometrical design of NMS scaffolds to minimize the volume ratio and maximize their functionality to fulfill the ever-increasing dependency and desire for energy power source supplies. This review will aim at highlighting these NMS scaffold design strategies, summarizing their corresponding strengths and challenges, and thereby outlining the potential solutions to resolve these challenges, design principles, and key perspectives for future research in this field. Therefore, this review will be one of the earliest reviews from this viewpoint.

Asymmetric Electrolytes Design for Aqueous Multivalent Metal Ion Batteries

With the rapid development of portable electronics and electric road vehicles, high-energy-density batteries have been becoming front-burner issues. Traditionally, homogeneous electrolyte cannot simultaneously meet diametrically opposed demands of high-potential cathode and low-potential anode, which are essential for high-voltage batteries. Meanwhile, homogeneous electrolyte is difficult to achieve bi- or multi-functions to meet different requirements of electrodes. In comparison, the asymmetric electrolyte with bi- or multi-layer disparate components can satisfy distinct requirements by playing different roles of each electrolyte layer and meanwhile compensates weakness of individual electrolyte. Consequently, the asymmetric electrolyte can not only suppress by-product sedimentation and continuous electrolyte decomposition at the anode while preserving active substances at the cathode for high-voltage batteries with long cyclic lifespan. In this review, we comprehensively divide asymmetric electrolytes into three categories: decoupled liquid-state electrolytes, bi-phase solid/liquid electrolytes and decoupled asymmetric solid-state electrolytes. The design principles, reaction mechanism and mutual compatibility are also studied, respectively. Finally, we provide a comprehensive vision for the simplification of structure to reduce costs and increase device energy density, and the optimization of solvation structure at anolyte/catholyte interface to realize fast ion transport kinetics.

Coupling of Adhesion and Anti-Freezing Properties in Hydrogel Electrolytes for Low-Temperature Aqueous-Based Hybrid Capacitors

Solid-state zinc-ion capacitors are emerging as promising candidates for large-scale energy storage owing to improved safety, mechanical and thermal stability and easy-to-direct stacking. Hydrogel electrolytes are appealing solid-state electrolytes because of eco-friendliness, high conductivity and intrinsic flexibility. However, the electrolyte/electrode interfacial contact and anti-freezing properties of current hydrogel electrolytes are still challenging for practical applications of zinc-ion capacitors. Here, we report a class of hydrogel electrolytes that couple high interfacial adhesion and anti-freezing performance. The synergy of tough hydrogel matrix and chemical anchorage enables a well-adhered interface between hydrogel electrolyte and electrode. Meanwhile, the cooperative solvation of ZnCl2 and LiCl hybrid salts renders the hydrogel electrolyte high ionic conductivity and mechanical elasticity simultaneously at low temperatures. More significantly, the Zn||carbon nanotubes hybrid capacitor based on this hydrogel electrolyte exhibits low-temperature capacitive performance, delivering high-energy density of 39 Wh kg-1 at -60 °C with capacity retention of 98.7% over 10,000 cycles. With the benefits of the well-adhered electrolyte/electrode interface and the anti-freezing hydrogel electrolyte, the Zn/Li hybrid capacitor is able to accommodate dynamic deformations and function well under 1000 tension cycles even at -60 °C. This work provides a powerful strategy for enabling stable operation of low-temperature zinc-ion capacitors.

Zinc-Bromine Rechargeable Batteries: From Device Configuration, Electrochemistry, Material to Performance Evaluation

Zinc-bromine rechargeable batteries (ZBRBs) are one of the most powerful candidates for next-generation energy storage due to their potentially lower material cost, deep discharge capability, non-flammable electrolytes, relatively long lifetime and good reversibility. However, many opportunities remain to improve the efficiency and stability of these batteries for long-life operation. Here, we discuss the device configurations, working mechanisms and performance evaluation of ZBRBs. Both non-flow (static) and flow-type cells are highlighted in detail in this review. The fundamental electrochemical aspects, including the key challenges and promising solutions, are discussed, with particular attention paid to zinc and bromine half-cells, as their performance plays a critical role in determining the electrochemical performance of the battery system. The following sections examine the key performance metrics of ZBRBs and assessment methods using various ex situ and in situ/operando techniques. The review concludes with insights into future developments and prospects for high-performance ZBRBs.