Volumetric Performance Research Articles

A microfluidic approach for controllable synthesis of TiO2 submicrospheres

TiO2 submicrospheres are used in dye-sensitized solar cells and Li-ion batteries to enhance energy conversion efficiency and volumetric performance. In this study, a microfluidic chip was designed for the realization of the continuous controllable synthesis of TiO2 submicrospheres. The chip utilizes two T-channels to discrete dispersed phases into droplets, and a Y-channel to fuse the two dispersed phase droplets. The droplets generation process, the influencing factors of droplet length and the fusion process of droplets were investigated. The effects of the flow rate ratio of titanium oxysulfate and ammonia solutions, microchannel geometrical profiles including the Y-channel entrance angle on the size of the synthesized TiO2 were studied. The length of the generated droplets was found to decrease with increasing continuous-phase flow rate, and increase with increasing dispersed-phase flow rate and microchannel cross-section area. When the flow rate ratio of titanium oxysulfate solution and ammonia solution was 1:1, the average diameter of TiO2 spheres synthesized was the smallest, around 300 nm. Increasing the microchannel cross-section and Y-channel entrance angle were beneficial in obtaining larger TiO2 submicrospheres. This proposed microfluidic strategy has the potential for applications required continuous synthesis of TiO2 submicrospheres with controllable sizes.

Computational Exploration of Adsorption-Based Hydrogen Storage in Mg-Alkoxide Functionalized Covalent-Organic Frameworks (COFs): Force-Field and Machine Learning Models.

Hydrogen is a clean-burning fuel that can be converted to other forms. of energy without generating any greenhouse gases. Currently, hydrogen is stored either by compression to high pressure (>700 bar) or cryogenic cooling to liquid form (<23 K). Therefore, it is essential to develop safe, reliable, and energy-efficient storage technology that can store hydrogen at lower pressures and temperatures. In this work, we systematically designed 2902 Mg-alkoxide-functionalized covalent-organic frameworks (COFs) and performed high-throughput (HT) computational screening for hydrogen storage applications at 111, 231, and 296 K. To accurately model the interaction between Mg-alkoxide sites and molecular hydrogen, we performed MP2 calculations to compute the hydrogen binding energy for different types of functionalized models, and the data were subsequently used to fit modified-Morse force field (FF) parameters. Using the developed FF models, we conducted HT grand canonical Monte Carlo (GCMC) simulations to compute hydrogen uptakes for both original and functionalized COFs. The generated data were subsequently used to evaluate the materials' gravimetric and volumetric storage performance at various temperatures (111, 231, and 296 K). Finally, we developed machine learning (ML) models to predict the hydrogen storage performance of functionalized structures based on the features of the original structures. The developed model showed excellent performance with a mean absolute error (MAE) of 0.061 wt % and 0.456 g/L for predicting the gravimetric and volumetric deliverable capacities, enabling a quick evaluation of structures in a hypothetical COF database. The screening results demonstrated that the Mg-alkoxide functionalization yields greater improvements in volumetric H2 storage capacities for COFs with smaller pores compared to those with larger (mesoporous) pores.

3D printing and micro-spring architecting to reconcile ultra-high areal and volumetric energy density in highly loaded supercapacitors

The rigorous demand for significantly enhanced performance gains in metrics of areal and volumetric energy density from futuristic energy storage devices is driving current technological endeavors towards the design of highly-loaded energy storage systems. The advancement of supercapacitors has faced a formidable challenge in reconciling ultra-high areal (>1 mWh cm−2) and volumetric performance (>10 mWh cm−3) due to the intricate issue of efficient mass transport in a highly loaded environment. Here, the capability of 3D printing technology to architect open frameworks is well leveraged in conjunction with material interface decoration to create a heavily loaded pseudocapacitive MnO2 electrode of low structural tortuosity and fast surface reaction. By harnessing the potential of self-assembly, a robust electrode composed of ubiquitous micro-springs is developed, permitting elastic strain engineering that exceptionally augmented the volumetric performance while preserving efficient mass transport pathways for reasonable kinetics. Coupling with these features, a groundbreaking achievement is attained as an individual supercapacitor unit now boasts an unprecedented ultrahigh areal energy density of 2.83 mWh cm−2 and volumetric energy density of 37.3 mWh cm−3. The proposed strategy provides an informative roadmap benefiting the construction of next-level electrochemical energy storage devices.

Scalable Self-Assembly of Composite Nanofibers into High-Energy-Density Li-Ion Battery Electrodes.

The application of nanosized active particles in Li-ion batteries has been the subject of intense investigation, yielding mixed results in terms of overall benefits. While nanoparticles have shown promise in improving rate performance and reducing issues related to cracking, they have also faced criticism due to side reactions, low packing density, and consequent subpar volumetric battery performance. Interesting processes such as self-assembly have been proposed to increase packing density, but these tend to be incompatible with scalable processes such as roll-to-roll coating, which are essential to manufacture electrodes at scale. Addressing these challenges, this research demonstrates the long-range self-assembly of carbon-decorated V2O5 nanofiber cathodes as a model system. These nanorods are closely packed into thick electrode films, exhibiting a high volumetric capacity of 205 mA h cm-3at 0.2 C. This surpasses the volumetric capacity of unaligned V2O5 nanofiber electrodes (82 mA h cm-3) under the same cycling conditions. We also demonstrate that these energy-dense electrodes retain an excellent capacity of up to 190.4 mA h cm-3(<2% loss) over 500 cycles without needing binders. Finally, we demonstrate that the proposed self-assembly process is compatible with roll-to-roll coating. This work contributes to the development of energy-dense coatings for next-generation battery electrodes with high volumetric energy density.

Microporous tungsten oxide spheres coupled with Ti3C2Txnanosheets for high-volumetric capacitance supercapacitors.

In the contemporary landscape of technological advancements, the burgeoning demand for portable electronics and flexible wearable devices has necessitated the development of energy storage systems with superior volumetric performance. Tungsten oxide (WO3), known for its high density and theoretical capacitance, is a promising electrode material for supercapacitors. However, low conductivity and poor cycling stability are still the key bottlenecks for its application. Herein, a novel composite comprising hollow porous WO3 spheres (HPWS) derived by template method was electrostatic self-assembled on the surface of the Ti3C2Tx nanosheets. The resulting electrodes exhibited ultra-high volumetric capacitance of 1930 F cm-3 at 1 A g-1 and rate capability of 46% at 50 A g-1, attributed to enhanced ion accessibility from microporous structure and electron transport from conductive network of Ti3C2Tx even at a high packing density of 3.86 g cm-3. Utilizing HPWS/Ti3C2Tx as the negative electrode and porous carbon as the positive electrode, the assembled asymmetric supercapacitor achieved an energy density of 31 Wh kg-1 at a power density of 650 W kg-1 with over 107% capacitance retention after 5000 cycles. This work provides a promising approach for developing next-generation supercapacitors with ultra-high volumetric capacitance.

Making 2D Materials Sparkle in Energy Storage via Assembly.

ConspectusTwo-dimensional (2D) materials such as graphene and MXenes offer appealing opportunities in electrochemical energy storage due to their large surface area, tunable surface chemistry, and unique electronic properties. One of the primary challenges in utilizing these materials for practical electrodes, especially those with industrial-level thickness, is developing a highly interconnected and porous conductive network. This network is crucial for supporting continuous electron transport, rapid ion diffusion, and effective participation of all active materials in electrochemical reactions. Moreover, the demand for efficient energy storage in advanced electronic devices and electric vehicles has led to the need for not only thicker but also denser electrodes to achieve compact energy storage. Traditional densification methods often compromise between volumetric capacitance and ion-accessible surface area, which can diminish rate performance. As versatile building blocks, 2D materials can overcome these limitations through the assembly into complex superstructures such as 1D fibers, 2D thin films, and 3D porous networks, a capability less attainable by other nanomaterials.This Account explores the pathways from exfoliated 2D nanosheets to densely packed, yet porous assemblies tailored for compact energy storage. Focusing on graphene and MXenes, we delve into the intricate relationships between surface structure, assembly behaviors, and electrochemical performance. We emphasize the crucial role of surface chemistry and interfacial interactions in forming stable colloidal dispersions and subsequent macroscopic structures. Furthermore, we highlight how solvents, acting as spacers, are instrumental in microstructure formation and how capillary force-driven densification is essential for creating compact assemblies. With precise control over shrinkage, the customized dense assemblies can strike a balance between high packing density and sufficient porosity, ensuring efficient ion transport, mechanical stability, and high volumetric performance across various electrochemical energy storage technologies.Furthermore, we highlight the importance of understanding and manipulating the surface chemistry of 2D materials at the atomic level to optimize their assembly and enhance electrochemical behaviors. Advanced in situ characterizations with high temporal and spatial resolution are necessary to gain deeper insights into the complex assembly process. Moreover, the integration of machine learning and computational chemistry emerges as a promising method to predict and design new materials and assembly strategies, potentially accelerating the development of next-generation energy storage systems. Our insights into the assembly and densification of 2D materials provide a comprehensive foundation for future research and practical applications in compact, high-performance energy storage devices. This exploration sets the stage for a transformative approach to overcoming the challenges of current energy storage technologies, promising significant advancements in 2D materials in the field.

Fabrication of RuO2-graphene/graphene thick-and-dense micro-hole array material by femtosecond laser for high volumetric rate performance

Nanostructured materials have a great application prospect in the next generation of electrochemical energy storage devices. However, there is a great obstacle for thick and dense electrodes with large tortuosity to simultaneously attain high areal and rate performance at the same time to meet the practical requirements. Herein, a simple electrostatic self-assembly method is adopted to anchor RuO2 onto graphene nanoflakes, the thick and dense film of RuO2-Graphene/Graphene(RuO2-G G-1) are prepared by filtration and mechanical compression, and then the micro-hole array structure was fabricated by femtosecond laser drilling, which shortened the diffusion path of hydrogen ion (H+). After etching, the pore diameter is 7 μm; the pore spacing is 40 μm and the array was regular. The mass loss of the electrode caused by etching was only 3 %, and the relative density of the electrode reached 79 %. Under the same thickness of the electrode, the pore electrode obviously reduces the ion resistance. The micro-hole array not only improves the areal and volumetric capacity of the RuO2-G G-1 electrode, but also improves the rate performance of the electrode., the rate capability increased from 65.6 % to 87.7 % at 20 A g-1. The study provides a powerful technique for the fabrication of dense and thick electrode in energy storage system.

Evaluation of Weight, area, and Volumetric Specific Capacitance Performance of high Graphene Content ZnFe2O4 Electrode for Supercapacitors

Evaluation of Weight, area, and Volumetric Specific Capacitance Performance of high Graphene Content ZnFe2O4 Electrode for Supercapacitors

Efficient Fabrication of Disordered Graphene with Improved Ion Accessibility, Ion Conductivity, and Density for High-Performance Compact Capacitive Energy Storage.

High-performance compact capacitive energy storage is vital for many modern application fields, including grid power buffers, electric vehicles, and portable electronics. However, achieving exceptional volumetric performance in supercapacitors is still challenging and requires effective fabrication of electrode films with high ion-accessible surface area and fast ion diffusion capability while simultaneously maintaining high density. Herein, a facile, efficient, and scalable method is developed for the fabrication of dense, porous, and disordered graphene through spark-induced disorderly opening of graphene stacks combined with mechanical compression. The obtained disordered graphene achieves a high density of 1.18gcm-3, sixfold enhanced ion conductivity compared to common laminar graphene, and an ultrahigh volumetric capacitance of 297Fcm-3 in ionic liquid electrolyte. The fabricated stack cells deliver a volumetric energy density of 94.2WhL-1 and a power density of 13.7kWL-1, representing a critical breakthrough in capacitive energy storage. Moreover, the proposed disordered graphene electrodes are assembled into ionogel-based all-solid-state pouch cells with high mechanical stability and multiple optional outputs, demonstrating great potential for flexible energy storage in practical applications.

Densification of Alloying Anodes for High Energy Lithium-Ion Batteries: Critical Perspective on Inter- Versus Intra-Particle Porosity.

High Li-storage-capacity particles such as alloying-based anodes (Si, Sn, Ge, etc.) are core components for next-generation Li-ion batteries (LIBs) but are crippled by their intrinsic volume expansion issues. While pore pre-plantation represents a mainstream solution, seldom do this strategy fully satisfy the requirements in practical LIBs. One prominent issue is that porous particles reduce electrode density and negate volumetric performance (WhL-1) despite aggressive electrode densification strategies. Moreover, the additional liquid electrolyte dosage resulting from porosity increase is rarely noticed, which has a significant negative impact on cell gravimetric energy density (Whkg-1). Here, the concept of judicious porosity control is introduced to recalibrate existing particle design principles in order to concurrently boost gravimetric and volumetric performance, while also maintaining the battery's cycle life. The critical is emphasized but often neglected role that intraparticle pores play in dictating battery performance, and also highlight the superiority of closed pores over the open pores that are more commonly referred to in the literature. While the analysis and case studies focus on silicon-carbon composites, the overall conclusions apply to the broad class of alloying anode chemistries.

Multi-recyclability of asphalt mixtures modified with recycled plastic: Towards a circular economy

Although asphalt pavements modified with recycled plastic have demonstrated enhanced performance, their recyclability remains under-explored, which is crucial under the scope of a circular economy. To address this, the present study investigates the multi-recyclability of asphalt mixtures, both with and without a recycled plastic modifier, at a recycling rate of 50 % over two cycles using an open-loop and a closed-loop model. The research utilised an innovative recycled plastic modifier made from hard waste plastics, incorporated into the mixture via the dry method. To ensure control over consistency and variables while also considering the novelty of the recycled plastic modifier, the reclaimed asphalt pavements (RAPs) were prepared using a loose asphalt mixture ageing protocol. Additionally, a rejuvenator made of vegetal derivatives was used as the recycling agent, considering the high recycling rate over each cycle. The comprehensive evaluation of volumetric and mechanical performance revealed that asphalt mixtures containing the recycled plastic modifier performed comparably to unmodified mixtures over two recycling cycles. Furthermore, all the recycled mixtures exhibited superior performance in resistance to rutting, moisture susceptibility, and fatigue compared to the conventional asphalt mixture. Overall, it can be inferred that the asphalt mixture modified with recycled plastic is capable of being recycled over multiple life cycles without compromising its mechanical and performance characteristics.

High volumetric performance of functional carbon material enabled by co-pyrolysis of mango branches and Faradaic active N-enriched doping

Restricted by the poor volumetric performance, biomass-based supercapacitors are challenging to meet the rapid development of miniaturization and portability of energy storage devices, and the Faraday active nitrogen-doping strategy proves to be an efficient approach to address this concern. This study successfully synthesizes functional carbon materials with significant Faraday activity through a straightforward and environmentally friendly co-pyrolysis method. Mango branches served as the primary raw material, NH4B5O8∙4H2O acted as a template, and NH4Cl and NH4B5O8∙4H2O were utilized as the multiple nitrogen-enriched agents. A surface micro-NH3 environment can be achieved by modulating the addition of NH4Cl, and the decomposed NH3 is adsorbed on the biomass surface by the electrostatic adsorption of NH4B5O8∙4H2O. MA1.5N1.5-T700 showcases a compact self-supported structure with micro/mesopores, boasting a substantial nitrogen content of 2.95 %. It achieves a notable volumetric capacitance of 320 F/cm3 (368 F/g) at 0.5 A/g and maintains an exceptional rate performance of 72.9 % at 20 A/g. The constructed symmetrical supercapacitor also reveals an ultra-high energy density of 13.01 Wh/L (14.95 Wh/kg) and an impressive capacitance retention of 94.03 % undergoing 10,000 cycles. This study offers theoretical insights into fabricating electrode materials for high volumetric energy density supercapacitors through the pyrolysis of forestry waste.

Achieving Exceptional Volumetric Desalination Capacity Using Compact MoS2 Nanolaminates.

Capacitive deionization (CDI) has emerged as a promising technology for freshwater recovery from low-salinity brackish water. It is still inapplicable in specific scenarios (e.g., households, islands, or offshore platforms) due to too low volumetric adsorption capacities. In this study, a high-density semi-metallic molybdenum disulfide (1T'-MoS2) electrode with compact architecture obtained by restacking of exfoliated nanosheets, which achieve high capacitance up to ≈277.5Fcm-3 under an ultrahigh scan rate of 1000mVs-1 with a lower charge-transfer resistance and nearly tenfold higher electrochemical active surface area than the 2H-MoS2 electrode, is reported. Furthermore, 1T'-MoS2 electrode demonstrates exceptional volumetric desalination capacity of 65.1mgNaClcm-3 in CDI experiments. Ex situ X-ray diffraction (XRD) reveal that the cation storage mechanism with the dynamic expansion of 1T'-MoS2 interlayer to accommodate cations such as Na+, K+, Ca2+, and Mg2+, which in turn enhances the capacity. Theoretical analysis unveils that 1T' phase is thermodynamically preferable over 2H phase, the ion hydration and channel confinement also play critical role in enhancing ion adsorption. Overall, this work provides a new method to design compact 2D-layered nanolaminates with high-volumetric performance for CDI desalination.

Activating Ion Channels in Collapsed Hydrogel Derived Densified MXene Films with Cellulose Nanofibers to Overcome the Areal Versus Volumetric Capacitance Trade-Off.

Concomitant achievement of all three performance pillars of a supercapacitor device, namely gravimetric, areal, and volumetric capacitance is a grand challenge. Nevertheless, its fulfilment is indispensable for commercial usage. Although, high compactness is the fundamental requirement to achieve high volumetric performance, it severely affects ion transportation in thick electrodes. Such trade-off makes it extremely challenging to realize very high areal and volumetric performance simultaneously. Here, a collapsed hydrogel strategy is introduced to develop MXene/cellulose nanofiber (CNF) based densified electrodes that offer excellent ion transportation despite a massive increase in areal mass loading (>70mg cm-2). Quasi-oriented MXene/CNF (MXCF) hydrogels are produced through an electric field-guided co-assembly technique. Ambient dehydration of these hydrogels incorporates numerous pores in the resultant compact electrodes due to crumpling of the MXene sheets, while CNF ensures connectivity among the locally blocked pores in different length scales. The resultant collapsed MXCF densified electrode shows a remarkably high areal capacitance of 16 F cm-2 while simultaneously displaying a high volumetric capacitance of 849.8 F cm-3 at an ultrahigh mass loading of up to 73.4mg cm-2. The universality of strategy, including the co-assembly of hydrogel and its collapse, is further demonstrated to develop high-performance asymmetric and wearable devices.

Research on the Mechanical, Thermal and Induction Healing Properties of Asphalt Wearing Course with Steel Fibers.

Induction healing technology can effectively repair microcracks in asphalt mixtures and is a promising maintenance technology for asphalt pavements. However, it requires the addition of steel wool fibers to asphalt mixtures and cannot be directly used to repair existing pavements. In order to improve the practicality of the induction healing technology, this article designs a wearing course asphalt mixture with induction healing function that is going to be paved above the existing road surface. The AC-10 asphalt wearing course for induction heating was prepared by adding steel fiber (SF). Analysis of the overall temperature of the surface revealed the unevenness of the temperature distribution, and the healing properties were investigated through protective heating that controlled the maximum temperature of the upper surface. The results show that the addition of SF can improve the high-temperature stability, low-temperature and intermediate-temperature crack resistance, and moisture stability of asphalt wearing courses; however, it has adverse effects on volumetric performance and skid resistance. The heating temperature increases with the increase in SF content, but higher maximum temperature heating rate causes worse heating uniformity and lower healing effect. The maximum heating rate of the sample with 10% SF reaches 3.92 °C/s, while its heating rate at minimum temperature is similar to that of the sample with 6% SF, which is only 0.7 °C/s, indicating the worst heating uniformity. The best healing effect occurs when the maximum temperature of the upper surface reaches 160 °C. The recommended optimal SF content is 6% of the asphalt volume. The asphalt mixture with 6% SF has an appropriate volume performance, moisture stability, and skid resistance; additionally, it has the best high-temperature stability, as well as low-temperature and intermediate-temperature crack resistance. Meanwhile, it also has uniform temperature distribution and efficient healing efficiency.

Influence of Non-Melting Waste Plastics on Volumetric Properties and Performance of Asphalt Mixtures

The main objective of the study is to evaluate the impact of using polystyrene (PS) and polyethylene terephthalate (PET) plastics as an additive in asphalt mixtures. For this purpose, volumetric modification, moisture susceptibility along with performance variation at high, intermediate, and low temperature conditions were evaluated. Initially plastics were subjected to calorimeter analysis for assessing their melting characterization. Both PS and PET are included as dry mix additives individually at dosage levels of 3%, 6%, and 9% by weight of asphalt binder. Further, the changes in thermal properties of plastics occurring during mixture preparation were correlated to better understand the volumetric modification. PS, owing to its glass transition and partial amorphous nature, exhibited minimum deviation (&lt;1%) from design air voids (4 ± 0.5%). PET was observed to increase the volumes of voids in mineral aggregate (VMA) and air void, owing to its crystalline nature. As regards performance, PS and PET modification enhanced the moisture resistance by 1.05 to 1.11 times the control mixture. The rutting tolerance index ( RTindex) value increased for all plastic modified mixtures from the indirect tensile asphalt rutting test (IDEAL RT) performed at 58°C. However, the intermediate temperature cracking tolerance index ( CTindex) at 19°C conveyed the high embrittled nature from plastic modification making the mixtures more susceptible to cracking. From the Gf versus l75 /m75 interaction diagram, it was conveyed that although addition of plastics improves the fracture toughness of asphalt mixtures, the ductile nature of mixtures is compromised. Also, PS and PET modification could not improve the ability of asphalt mixtures to resist thermal cracking, evaluated at −18°C.

MgO templated carbons: Effect of synthesis methodology on the morphology, surface chemistry and supercapacitor performances

Templating method is a widely adopted route to prepare porous carbon, while the effect of methodology on the structure and performances of the derived porous carbon was rarely focused. Herein, we employed a commercial MgO as template and catechol/formaldehyde as starting materials to prepare porous carbon by incipient impregnation method (the derived product denoted as MgC-I) and aqueous self-assembly method (the derived product denoted as MgC-S), respectively. Systematically analysis indicates that impregnation method favors the construction of two-dimensional structure, while, aqueous self-assembly method benefits formation of densified structure. Concerning to the surface chemistry, aqueous self-assembly method enables more residual oxygenic functionalities than that of impregnation derived ones. As electrode for supercapacitor in aqueous electrolyte, the MgC-S achieves superior volumetric performances including high specific volumetric capacitance of 319 F/cm3@1.0 A/g and large energy density of 27.9 Wh/L@1193 W/L, showing a potential for practical energy storage devices. Whereas, in organic electrolyte of 1.0 M TEANBF4/AN, the MgC-I electrode show a superior energy storage ability with energy density of 40.5 Wh kg−1@1350 W kg−1, the value is about six times higher than that of MgC-S based one. This study provides a reference for how to choose synthesis methods for preparing carbon materials with specific target.

Collapsed N&S dual-doped carbon nanocages as high-density anode for ultrahigh volumetric performance of Li-ion batteries

Compact lithium-ion batteries for miniaturized devices require high-volumetric-performance anodes. Either the graphite with high density or the porous nanocarbons with high gravimetric performance is limited in volumetric performance. Herein, we construct a series of anode materials, i.e. the collapsed carbon nanocages with different dopants, by capillarity compression, which achieves a high density of ∼0.97 g cm−3 but remains abundant micropores with increased active sites and enlarged interlayer distance. The N&S dual-doping redistributes the charges of sp2 carbon to an optimal status, leading to the high Li-ion capacity, meanwhile facilitates the wettability at the electrode/electrolyte interface, leading to the enhanced Li-ion diffusion coefficient. Accordingly, the collapsed N&S dual-doped carbon nanocages (cNSCNC) anode exhibits a record-high volumetric capacity of 1578 mAh cm−3 at 0.1 A g−1, excellent rate capability and cycling stability, thus achieving an ultrahigh volumetric energy density of 1087 Wh L−1 at 120 W L−1 for the cNSCNC//LiFePO4 full cell.

Vascular System Inspired 3D Electrolyte Network for High Rate and High Mass Loading Graphene Supercapacitor

AbstractHigh charge rate and high mass loading ability are of practical importance for high power and high volumetric performance supercapacitors but are always challenged by tortuous and sluggish ion diffusion in thick electrodes. Here, inspired by the hepatic vascular system, hierarchical 3D electrolyte networks are proposed to facilitate ion diffusion across laminar graphene films, resulting in a 14‐fold improved ion diffusion coefficient, better rate ability, and high mass loading ability for graphene supercapacitors. Such design enables graphene electrodes with high capacitance up to 236 F g−1, packing densities of 0.67–0.78 g cm−3 depending on structures; and core stack with 10 mg cm−2 mass loading exhibits a high energy density of 45.4 Wh L−1, which is among the state‐of‐the‐art graphene supercapacitors. This study provides a comprehensive investigation of structure‐related capacitive properties, guiding electrode design for high‐rate and high‐mass‐loading graphene supercapacitors. Moreover, such design also benefits solid‐state graphene supercapacitors by forming 3D gel electrolyte structures, which enable higher capacitance and better mechanical robustness, showing potential for flexible energy storage.

3D Dense Encapsulated Architecture of 2D Bi Nanosheets Enabling Potassium-Ion Storage with Superior Volumetric and Areal Capacities.

2D alloy-based anodes show promise in potassium-ion batteries (PIBs). Nevertheless, their low tap density and huge volume expansion cause insufficient volumetric capacity and cycling stability. Herein, a 3D highly dense encapsulated architecture of 2D-Bi nanosheets (HD-Bi@G) with conducive elastic networks and 3D compact encapsulation structure of 2D nano-sheets are developed. As expected, HD-Bi@G anode exhibits a considerable volumetric capacity of 1032.2 mAh cm-3, stable long-life span with 75% retention after 2000 cycles, superior rate capability of 271.0 mAh g-1 at 104 C, and high areal capacity of 7.94 mAh cm-2 (loading: 24.2mg cm-2) in PIBs. The superior volumetric and areal performance mechanisms are revealed through systematic kinetic investigations, ex situ characterization techniques, and theorical calculation. The 3D high-conductivity elastic network with dense encapsulated 2D-Bi architecture effectively relieves the volume expansion and pulverization of Bi nanosheets, maintains internal 2D structure with fast kinetics, and overcome sluggish ionic/electronic diffusion obstacle of ultra-thick, dense electrodes. The uniquely encapsulated 2D-nanosheet structure greatly reduces K+ diffusion energy barrier and accelerates K+ diffusion kinetics. These findings validate a feasible approach to fabricate 3D dense encapsulated architectures of 2D-alloy nanosheets with conductive elastic networks, enabling the design of ultra-thick, dense electrodes for high-volumetric-energy-density energy storage.