Advanced Energy Storage Materials Research Articles

Progress and Perspective of High‐Entropy Strategy Applied in Layered Transition Metal Oxide Cathode Materials for High‐Energy and Long Cycle Life Sodium‐Ion Batteries

AbstractLayered transition metal oxide (LTMO) cathode materials of sodium‐ion batteries (SIBs) have shown great potential in large‐scale energy storage applications owing to their distinctive periodic layered structure and 2D ion diffusion channels. However, several challenges have hindered their widespread application, including phase transition complexities, interface instability, and susceptibility to air exposure. Fortunately, an impactful solution has emerged in the form of a high‐entropy doping strategy employed in energy storage research. Through the implementation of high‐entropy doping, LTMOs can overcome the aforementioned limitations, thereby elevating LTMO materials to a highly competitive and attractive option for next‐generation cathodes of SIBs. Thus, a comprehensive overview of the origins, definition, and characteristics of high‐entropy doping is provided. Additionally, the challenges associated with LTMOs in SIBs are explored, and discussed various modification methods to address these challenges. This review places significant emphasis on conducting a thorough analysis of the research advancements about high‐entropy LTMOs utilized in SIBs. Furthermore, a meticulous assessment of the future development trajectory is undertaken, heralding valuable research insights for the design and synthesis of advanced energy storage materials.

Bacterial Cellulose Applications in Electrochemical Energy Storage Devices.

Bacterial cellulose (BC) is produced via the fermentation of various microorganisms. It has an interconnected 3D porous network structure, strong water-locking ability, high mechanical strength, chemical stability, anti-shrinkage properties, renewability, biodegradability, and a low cost. BC-based materials and their derivatives have been utilized to fabricate advanced functional materials for electrochemical energy storage devices and flexible electronics. This review summarizes recent progress in the development of BC-related functional materials for electrochemical energy storage devices. The origin, components, and microstructure of BC are discussed, followed by the advantages of using BC in energy storage applications. Then, BC-related material design strategies in terms of solid electrolytes, binders, and separators, as well as BC-derived carbon nanofibers for electroactive materials are discussed. Finally, a short conclusion and outlook regarding current challenges and future research opportunities related to BC-based advanced functional materials for next-generation energy storage devices suggestions are proposed.

Single-Nanometer Spinel with Precise Cation Distribution for Enhanced Oxygen Reduction.

Designing spinel nanocrystals (NCs) with tailored structural composition and cation distribution is crucial for superior catalytic performance but remarkably challenging due to their intricate nature. Here, an aggregation growth restricted hot-injection method is presented by meticulously investigating the fundamental nucleation and aggregation-driven growth kinetics governing spinel NC formation to address this challenge. Through controlled collision probability of nuclei during growth, this approach enables the synthesis of spinel NCs with unprecedented, single nanometer (1.2nm). Single-nanometer CoMn2O4 spinel via this method exhibits a highly tailored structure with a maximized population of highly active octahedral Mn atoms, thereby optimizing oxygen intermediate adsorption during oxygen reduction reaction (ORR). Consequently, it exhibits a remarkable half-wave potential of 0.88V in ORR and leads to a superior power density (170.9mW cm-2) in zinc-air battery, outperforming commercial Pt/C and most reported spinel oxides, revealing a clear structure-property relationship. This structure design strategy is readily adaptable for the precise synthesis and engineering of various spinel structures, opening new avenues for developing advanced electrocatalysts and energy storage materials.

Guiding nitrogen doped vanadium pentoxide nanoclusters on cobalt sulfide nano-flakiness as stable seamless interface anode toward highly energy density and durable asymmetric supercapacitors

Interaction of the interface-heterostructures is crucial to rapid ionic conductivity and highly energy density of electrode materials toward supercapacitors. Herein, a novel anode heterostructure is synthesized using cobalt sulfide (CoS) nanoflowers as a substrate for composite nitrogen doped vanadium pentoxide (denoted as N-V2O5@CoS) by combination of hydrothermal and calcination method. As expected, the N-V2O5@CoS electrode possesses superhigh specific surface area that significantly enhances the specific capacitance, and its unique porous interconnected structure not only reduces the volume effect during the cycles, but also greatly enhances the conductivity of electron transfer. The as-prepared N-V2O5@CoS electrode has a specific capacitance of up to 2413.6F/g at a current density of 1 A/g, and can still maintain 87.51 % of the initial capacitance after 5,000 cycles at a high current density of 10 A/g. More importantly, the partial density of states (PDOS) ares obtained through theoretical calculations reveal that the interaction of heterogeneous interfaces is contributed by the p-orbitals of C, O and S and d-orbitals of V and Co. In addition, asymmetric supercapacitor (ASC) with N-V2O5@CoS as the positive electrode and activated carbon (AC) as the negative electrode has a high voltage of 1.7 V, which achieves an outstanding energy density of 71.6 W h kg−1 at a power density of 849.8 W kg−1, showing excellent cycle stability (retain 90.6 % of the initial capacitance after 10,000 charge/discharge cycles). This paper offers novel paradigm for the doping of metal oxides and the development of heterostructures, which provides support for their use as advanced energy storage materials.

Encapsulation of Sn Sub‐Nanoclusters in Multichannel Carbon Matrix for High‐Performance Potassium‐Ion Batteries

AbstractSub‐nanoclusters with ultra‐small particle sizes are particularly significant to create advanced energy storage materials. Herein, Sn sub‐nanoclusters encapsulated in nitrogen‐doped multichannel carbon matrix (denoted as Sn‐SCs@MCNF) are designed by a facile and controllable route as flexible anode for high‐performance potassium ion batteries (PIBs). The uniformly dispersed Sn sub‐nanoclusters in multichannel carbon matrix can be precisely identified, which ensure us to clarify the size influence on the electrochemical performance. The sub‐nanoscale effect of Sn‐SCs@MCNF restrains electrode pulverization and enhances the K+ diffusion kinetics, leading to the superior cycling stability and rate performance. As freestanding anode in PIBs, Sn‐SCs@MCNF manifests superior K+ storage properties, such as exceptional cycling stability ( around 331 mAh g−1 after 150 cycles at 100 mA g−1) and rate capability. Especially, the Sn‐SCs@MCNF||KFe[Fe(CN)6] full cell demonstrates impressive reversible capacity of around 167 mAh g−1 at 0.4 A g−1 even after 200 cycles. Theoretical calculations clarify that the ultrafine Sn sub‐nanoclusters are beneficial for electron transfer and contribute to the lower energy barriers of the intermediates, thereby resulting in promising electrochemical performance. Comprehensive investigation for the intrinsic K+ storage process of Sn‐SCs@MCNF is revealed by in situ analysis. This work provides vital guidance to design sub‐nanoscale functional materials for high‐performance energy‐storage devices.

Encapsulation of Sn Sub-Nanoclusters in Multichannel Carbon Matrix for High-Performance Potassium-Ion Batteries.

Sub-nanoclusters with ultra-small particle sizes are particularly significant to create advanced energy storage materials. Herein, Sn sub-nanoclusters encapsulated in nitrogen-doped multichannel carbon matrix (denoted as Sn-SCs@MCNF) are designed by a facile and controllable route as flexible anode for high-performance potassium ion batteries (PIBs). The uniformly dispersed Sn sub-nanoclusters in multichannel carbon matrix can be precisely identified, which ensure us to clarify the size influence on the electrochemical performance. The sub-nanoscale effect of Sn-SCs@MCNF restrains electrode pulverization and enhances the K+ diffusion kinetics, leading to the superior cycling stability and rate performance. As freestanding anode in PIBs, Sn-SCs@MCNF manifests superior K+ storage properties, such as exceptional cycling stability ( around 331 mAh g-1 after 150 cycles at 100 mA g-1) and rate capability. Especially, the Sn-SCs@MCNF||KFe[Fe(CN)6] full cell demonstrates impressive reversible capacity of around 167 mAh g-1 at 0.4 A g-1 even after 200 cycles. Theoretical calculations clarify that the ultrafine Sn sub-nanoclusters are beneficial for electron transfer and contribute to the lower energy barriers of the intermediates, thereby resulting in promising electrochemical performance. Comprehensive investigation for the intrinsic K+ storage process of Sn-SCs@MCNF is revealed by in situ analysis. This work provides vital guidance to design sub-nanoscale functional materials for high-performance energy-storage devices.

Boosting Zn2+ Intercalation in High‐Performance Aqueous Zinc‐Ion Batteries with Coupling‐Induced Biphase Interface

AbstractEffectively addressing the trade‐off between fast charging kinetics and long cycle life of aqueous zinc ion batteries (AZIBs) has proven challenging due to JahnTeller distortion and high lattice strain induced by inserted Zn2+ ions in cathode structures. Herein, a hybrid cathode of NiCo2O4‐MnO2 with abundant electrochemical phase interfaces and interface coupling induced defects is developed via a simple electrochemical oxidation strategy to boost rich redox reactions. The formation of Ni─O─Mn and Co─O─Mn bonds promoted the electron transfer between the biphase interface, adjusted the electron density of the material body, effectively alleviated the electrostatic effect between Zn2+ embedding and the main frame, and further maintained the stability of the structure and alleviated the dissolution of manganese. The resulting NiCo2O4‐MnO2 cathode exhibited a high reversible specific capacity of 343.5 mA h g−1 at a current density of 100 mA g−1 and retained 95.5 % of its initial capacity after 1000 cycles at a current density of 1 A g−1. This discovery enriches insights into performance mechanisms at interfaces and paves the way for designing advanced energy storage materials.

Dynamic Imaging of Electrochemically Induced Transformations in Layered Tin Chalcogenide Catalysts.

Understanding the dynamic transformation processes of electrocatalysts during electrochemical reactions is crucial for the development of advanced materials for energy conversion and storage, yet it remains a challenge. Herein, we report the real-time monitoring of the dynamic transformation of a series of layered Sn chalcogenides during electrochemical reduction using a plasmonic imaging method. Taking SnSe2 as an example, we observed a strong firework-like emission diffusing outward from SnSe2 to the surrounding solution under a negative potential. The diffusion coefficient of the observed species is indicative of Sn nanoclusters rather than smaller ions. This study also extends to SnSe and SnS2 nanosheets, demonstrating the general applicability of plasmonic imaging for probing the stability and transformation mechanism of heterogeneous catalysts in electrocatalytic reactions. These insights provide a foundational understanding for designing more stable and efficient electrocatalysts for industrial applications.

Architecting hydrogen-bonded and π–π conjugated MOF@NiPc networks towards enhanced energy storage

High-capacity metal–organic framework materials is constrained by their poor electron transport and unstable in aqueous. Herein, a spherical cobalt–nickel-based metal–organic framework (CoNi-MOF) micro-architecture with 18-π aromatic electron system of nickel phthalocyanine (NiPc) nanorods has been designed. In this system, intermolecular hydrogen (H) bonds between O in CoNi-MOF and H in nickel phthalocyanine (NiPc), along with longitudinal π-π stacking structure, could improve electron transport and structuralstability of MOFs. Benefiting from the 3D electron transport highways and “locking” effect of H bonds along with longitudinal π-π stacking structure, the optimized CoNi-MOF@NiPc electrode exhibits remarkable specific capacity of 807.365C g−1 at current density of 1 A/g, along with great cycling stability with 96.19 % capacity retention after 5000 cycles at 5 A/g, which is superior to the individual components. Besides, CoNi-MOF@NiPc//AC hybrid supercapacitor has been fabricated, which displays a maximum energy density of 130.68 Wh kg−1 at 962.09 W kg−1 and excellent cyclability (93.58 % capacity retention after 10,000 cycles). This study opens a new avenue for the design of organic electrodes and provides a new insight into H bond and π-π stacking structure effect toward advanced energy storage materials.

Fabrication and characterization of zinc anode on nickel conductive cloth for high-performance zinc ion battery applications

The development of advanced materials for energy storage is critical to addressing global energy challenges. Zinc-ion batteries offer a promising solution due to their safety, cost-effectiveness, and environmental friendliness. In this study, we enhanced the conductivity of cotton by coating it with electroless nickel, followed by zinc electroplating, to create a flexible material suitable for zinc-ion battery applications. Cotton was coated with electroless nickel at temperatures ranging from 40°C to 60°C for 1 min to 13 min. Subsequently, zinc electroplating was performed with current densities of 0.02 A·cm‒2 for 60 min, 0.03 A·cm‒2 for 40 min, and 0.04 A·cm‒2 for 30 min. The resulting material was used to assemble a battery with an (NH4)2V10O25·8H2O (NVO) cathode. The Scanning Electron Microscope (SEM) confirms the electroless nickel-coating on cotton fabric at 50°C for 9 min resulted in a low electrical resistance of 15 ohms. Subsequent zinc electroplating at 0.03 A·cm‒2 for 40 min fully interconnected zinc particles. This research demonstrates the significant potential for further development in the field of textile materials for electrical conductivity. It also makes it possible to incorporate materials like silk cloth and other materials in battery components, which will help build more sustainable energy sources in the future.

(Invited) Plasma Designing of Hybrid 2D Graphene: A Green Approach for Future Energy Materials

The global research interest in two-dimensional (2D) materials and their derivatives has increased significantly, driven by the requirements of application-oriented materials for different sectors, including energy storage. Among the various classes of material groups, 2D layered materials have emerged as a critical research area due to their high aspect ratio, open edge boundaries, high surface-to-volume ratios, and mechanical and electrical properties. Graphene is a widely researched 2D class material with an atomically thin structure, excellent electronic properties, very high intrinsic mobility and exceptional thermal and electrical conductivity1. Even though the research on the electronic properties of graphene is explored very well and in a matured state, the studies on non-electronic properties are still in the budding phase. One of the significant obstacles to extending the studies of graphene to different fields is the cost-effective and environmentally friendly large-scale synthesis and processing of high-quality graphene. Thus, a cutting-edge approach for probing graphene structures at the atomic scale is required to produce high-quality graphene for next-generation applications. As an alternative progressive technique, plasma-enabled methods have emerged as safe and green approaches to tailor different graphene structures at the nanoscale. During graphene production, plasma assembles the nanostructures from gaseous into a solid form or converts solid precursor to graphitic form 2,3. Besides, plasma techniques open up the possibility of tailoring the properties by crafting heteroatoms to the graphene lattice, which is beneficial for energy storage applications4. Therefore, this paper introduces the advantages of plasma-enabled techniques in designing graphene-based materials with different morphologies and orientations and tailoring them at the nanoscale using heteroatoms. Such plasma-assisted techniques ensure the high structural quality of graphene and controllability in the hybrid morphologies, making them frontrunner energy storage applications. Plasma also offers the production of graphene directly on any substrate surface, gives a new direction to designing binder-free electrodes for energy-related applications, and could be used as a competitive alternative approach to the widely known wet chemical procedures to design advanced graphene electrode materials for next-generation energy storage devices.Reference Geim, A. K. Graphene: Status and prospects. Science (1979) 324, 1530–1534 (2009).Dias, A. et al. N-Graphene-Metal-Oxide(Sulfide) hybrid Nanostructures: Single-step plasma-enabled approach for energy storage applications. Chemical Engineering Journal 430, 133153 (2022).Jagodar, A. et al. Growth of graphene nanowalls in low-temperature plasma: Experimental insight in initial growth and importance of wall conditioning. Appl Surf Sci 643, 158716 (2024).Santhosh, N.M. et al. N-Graphene Nanowalls via Plasma Nitrogen Incorporation and Substitution: The Experimental Evidence. Nanomicro Lett 12, 53 (2020).

(Invited) Tailored Electrochemical Interfaces for Renewable Fuels Production

Tailoring the structure of the electrified interface and the electrocatalytically active sites at the atomic and molecular levels is key to elucidating the design principles to develop advanced materials for sustainable energy conversion and storage. This talk will focus on recent strategies to tune the structure-activity-selectivity relationships for oxygen, carbon dioxide/carbon monoxide and methane electrocatalysis to produce renewable fuels.First, I will present our work toward understanding and tuning the structure-property relations for oxygen evolution for the production of green hydrogen in proton exchange membrane water electrolysers. Then, I will show our model studies on well-defined Cu-based surfaces to understand structure-properties relations for the electrochemcial CO2 reduction reaction. We have investigated the effect of electrolyte, pH, and potential dependence for CO reduction on Cu single crystals as well as methods to evaluate the facet distribution on Cu-based catalysts. Finally, I will discuss some strategies for selective oxidation reactions such as partial oxidation of methane to produce liquid fuels such as methanol.

Artificial aluminum-doped SiO2 aerogel coating layer regulating zinc ions flow for highly reversible dendrite-free zinc anodes

As a sustainable, safe, and cost-effective alternative to conventional lithium-ion batteries, aqueous rechargeable zinc-metal-based batteries have attracted significant attention in large-scale energy storage. However, their practical application is hindered by zinc anode degradation, primarily dendrite growth and corrosion, which compromise battery performance and lifespan. Herein, we present an aluminum-doped silica (Al-SiO2) aerogel coating layer to address these issues. The aluminum-doped silica aerogel coating layer offers improved hydrophilicity and zinc ion adsorption capabilities because of its porous structure, high surface area, and functional groups. By facilitating uniform zinc ion deposition and providing a physical barrier against corrosion, the Al-SiO2 aerogel coating layer significantly mitigates dendrite formation and extends the electrochemical stability and operational lifespan of aqueous rechargeable zinc-metal-based batteries. Symmetric cell tests reveal that zinc anodes coated with Al-SiO2 can achieve stable cycling over 3000 h, indicating exceptional reversibility and rate performance, much better than that of the bare Zn anode. Furthermore, the Al-SiO2 aerogel-coated zinc anode coupled with MnO2 cathode forms a stable rechargeable full battery. This work contributes to the body of knowledge on advanced materials for energy storage, highlighting the potential of aerogel coatings as a scalable and effective solution for improving the performance and durability of zinc metal anode for aqueous rechargeable zinc-metal-based batteries.

Plasma-assisted synthesis of ultra-fine NiCo2O4/NiCo-layered double hydroxides nanoparticles-decorated electrospun carbon nanofibers with enhanced electrochemical performance

Nickel cobaltate/NiCo-layered double hydroxides (NiCo2O4/NiCo-LDH) as energy storage materials offer considerable potential for various applications. However, many of current methods for synthesizing NiCo2O4/NiCo-LDH suffer from long synthesis times, complex preparation process, and high temperatures and high pressures. In this study, we present a green, simple, and efficient approach known as assisted liquid-phase plasma electrolysis, which realizes the rapid fabrication of ultra-fine NiCo2O4/NiCo-LDH nanoparticle-decorated electrospun carbon nanofibers (NiCo2O4/NiCo-LDH/CNFs) composites. Ultra-fine NiCo2O4/NiCo-LDH nanoparticles (<70 nm) are uniformly deposited on the CNF surface. The CNFs are intertwined to form a highly conductive three-dimensional mesh structure, which synergizes the NiCo2O4/NiCo-LDH nanoparticles with a high specific capacitance in favor of ion/electron transport efficiency. In addition, the cooperative effect between the two phases of NiCo2O4 and NiCo-LDH further improves the electrochemical properties. The NiCo2O4/NiCo-LDH/CNFs composites exhibit a high specific capacitance of 1534.7 F/g at 1 A/g and a capacitance retention of 93.9 % after 5000 cycles. An assembled asymmetric supercapacitor using activated carbon and NiCo2O4/NiCo-LDH/CNFs composites achieves an energy density of 33.8 Wh/kg at a power density of 400 W/kg and a capacitance retention of 93.0 % after 5000 cycles. Notably, two series-connected NiCo2O4/NiCo-LDH/CNFs ASC supercapacitors can light up an LED bulb, which maintains a certain brightness even after 50 min. Hence, this work provides a new and efficient route for synthesizing carbon-based NiCo2O4/NiCo-LDH composites for use as advanced energy storage materials.

Strategic Fabrication of Au4Cu2 NC/ZIF‐8 Composite Via In Situ Integration Technique for Enhanced Energy Storage Applications

AbstractMetal–organic frameworks (MOFs), known for their extensive porosity and versatile crystallinity, play a crucial role in the development of advanced energy storage materials. However, their application is limited by stability and conductivity issues. This study addresses these challenges by integrating ultrasmall metal nanoclusters, specifically Au4Cu2 NC, synthesized using a mixed ligand strategy combining 2, 4‐Dimethyl benzene thiol (2,4‐DMBTH) and 1,2‐bis(diphenylphosphino)ethane (dppe). The bimetallic Au4Cu2 NC, characterized by Single Crystal X‐Ray Diffraction (SCXRD), is applied to zeolitic imidazolate framework‐8 (ZIF‐8) using both in situ and ex situ methods to explore their electrochemical and physicochemical properties in energy storage. The in situ Au4Cu2 NC/ZIF‐8 composite demonstrated a specific capacitance that is almost two times higher than its ex situ counterpart, attributed to homogeneous dispersion and hence enhanced conductivity. This in situ integration of atomically precise bimetallic nanoclusters on MOFs significantly boosts supercapacitor performance, offering a more effective and reliable solution for energy storage. Further, in practical applications, this device demonstrated an energy density of 87.2 Wh kg−1 at a power density of 1474 W kg−1, highlighting its robustness and potential for high‐performance energy storage applications. This approach effectively combats the issue of nanocluster aggregation on substrates, marking a significant progression in supercapacitor technology.

Enhancing electrochemical properties of bacterial cellulose-derived carbon nanofibers through physical CO2 activation

Carbon nanofiber (CNF) derived from carbonization of bacterial cellulose (BC), with a unique three-dimensional porous nanostructure, has received significant interest in electrochemical applications. In this study, CNF samples were physically activated in CO2 at different temperatures and durations. Raman spectroscopy and FTIR analysis showed that CO2 activation caused hexagonal lattice defects, disorder, and oxygen-related functional groups in an amorphous carbon structure. CNF surface morphology changed after physical activation, reducing fiber diameter to 55 nm and introducing mesopores. Through activation temperature and time adjustments, surface area (870.1 m2/g) and micropore surface area (535.6 m2/g) and pore volume (0.2148 cm3/g) increased. EDX elemental analysis showed that activated CNF had a carbon concentration of > 90 %, while XPS analysis showed surface functional groups like C-C (sp2) and C-C (sp3) hybridization, which could improve electrolyte ion adsorption and accessibility. Electrochemical properties improved owing to CO2 activation. The optimal activation condition of 800 ℃ for 60 min resulted in the highest specific area capacitance of 552 mF cm−2 at 1 mA cm−2. This activated CNF electrode retained capacitance nearly unchanged up to 3,000 cycles. It also achieved the highest energy density of 76.7 mWh cm−2 at 500 mW cm−2. This study demonstrates the efficacy of CO2 physical activation for enhancing the electrochemical properties of CNF electrodes. The findings also highlight the importance of tailoring activation conditions, providing valuable insights for the design of advanced energy storage materials.

Huge Electron Sponge of Polyoxometalate toward Advanced Lithium-Ion Storage.

The huge polyoxometalate, ({Mo368}), which can be prepared by a facile solution process and can be applied in lithium-ion storage applications as the anode. The large and open hollow nanostructure is promising to store a larger number of lithium ions and expedite the diffusion of lithium ions. A single {Mo368} nanocluster can transfer 624 electrons, referred to as a "huge electron sponge". Pure {Mo368} without any support materials exhibits very high capacities of 964 mA h g-1 with hardly any decay for 100 cycles at 0.1 A g-1 and still maintains 761 mA h g-1 after 180 cycles at 0.5 A g-1, indicating great cycling stability. The {Mo368} anode provides excellent rate performance and reversibility during the lithiation/delithiation processes, which are contributed by both the diffusion-controlled process and the capacitive process. The capacitive contribution can reach 71.7% at a scan rate of 2 mV s-1. The high DLi+ value measured by GITT confirms the fast reaction kinetics of the {Mo368} electrode. The {Mo368}//NCM111-A full cell is practically applied to light LED lamps. These investigations indicate that {Mo368} nanoclusters are advanced energy storage materials with high capacities, fast charge transfer, and low-cost mass production for lithium-ion storage. Moreover, {Mo368} should be considered a clean energy material because there is no production of environmental pollution during the charge/discharge processes.

Adjustable nanoarchitectonics of N-doping Yolk-Shell carbon spheres via “Pyrolysis-Capture” method for High-Performance supercapacitor

The energy storage capacity of porous carbon materials is closely tied to their surface structure and chemical properties. However, developing an innovative and straightforward approach to synthesize yolk-shell carbon spheres (YCs) remains a great challenge till date. Herein, we prepared a series of porous nitrogen-doped yolk-shell carbon spheres (NYCs) via a “pyrolysis-capture” method. This method involves coating the resorcinol–formaldehyde (RF) resin sphere with a layer of compact silica shell induced by 2-methylimidazole (ME) catalysis to produce a confined nano-space. Based on the confined effect of compact silica shell, volatile gases emitted from the RF resin and ME during pyrolysis can not only diffuse into the pores of the RF resin but can also be captured to form an outer carbon shell. This results in the tunable structures of NYCs materials. As the pyrolysis temperature rises, the shell thickness of NYCs reduces, the pore size expands, the roughness increases, and the N/O content of surface elements is enhanced. Notably, as an electrode material used forsupercapacitors,the optimized NYCs-800 exhibits excellent performance with a capacitance of 301.2F g−1 at the current density of 1 A/g and outstanding cycling life stability of 96.1% after 10,000 cycles. These results signify that controlling the surface structure and chemical properties of NYCs materials is an effective approach for constructing advanced energy storage materials.

Understanding the origins of reversible and hysteretic pathways of adsorption phase transitions in metal-organic frameworks

Phase behavior of nanoconfined fluids adsorbed in metal–organic frameworks is of paramount importance for the design of advanced materials for energy and gas storage, separations, electrochemical devices, sensors, and drug delivery, as well as for the pore structure characterization. Phase transformations in adsorbed fluids often involve long-lasting metastable states and hysteresis that has been well-documented in gas adsorption–desorption and nonwetting fluid intrusion-extrusion experiments. However, theoretical prediction of the observed nanophase behavior remains a challenging problem. The mesoscopic canonical, or mesocanonical, ensemble (MCE) is devised to study the nanophase behavior under conditions of controlled fluctuations to stabilize metastable and labile states. Here, we implement and apply the MCE Monte Carlo (MCEMC) simulation scheme to predict the origins of reversible and hysteric adsorption phase transitions in a series of practical MOF materials, including IRMOF-1, ZIF-412, UiO-66, Cu-BTC, IRMOF-74-V, VII, and IX. The MCEMC method, called the gauge cell method, allows to produce Van der Waals type isotherms with distinctive swings around the phase transition regions. The constructed isotherms determine the positions of phase equilibrium and spinodals, as well as the nucleation barriers separating metastable states. We demonstrate the unique capabilities of the MCEMC method in quantitative predictions of experimental observations compared with the conventional grand canonical and canonical ensemble simulations. The MCEMC method is implemented in the open-source RASPA and LAMMPS software packages and recommended for studies of adsorption behavior and pore structure characterization of MOFs and other nanoporous materials.

Metal oxide-based nanocomposites as advanced electrode materials for enhancing electrochemical performance of Supercapacitors: A comprehensive review

In recent years, the escalating use of nonrenewable fossil fuels has emerged as a significant threat to global sustainability, prompting the need for renewable, cost-effective, and eco-friendly energy storage solutions. Supercapacitors (SCs) are notable for their high power density (PD), cycle stability, and swift charge/discharge rates, although they fall short in energy density (ED) compared to traditional batteries. The performance of SCs is greatly influenced by the electrode materials used, highlighting the importance of material innovation in tackling the challenges posed by increasing fossil fuel consumption. Transition metal oxides (TMOs), known for their redox activity in energy storage, have been thoroughly investigated for their exceptional specific capacitance, which ranges from 100 to 2000F g−1, surpassing that of electrical double-layer capacitors (EDLCs). TMOs such as ruthenium oxide (RuO2), manganese oxide (MnO2), nickel oxide (NiO), cobalt oxide (Co3O4), tin oxide (SnO2), zinc oxide (ZnO), tungsten oxide (WO3), and vanadium pentoxide (V2O5) are widely researched for their high theoretical capacitance, affordability, and longevity. This review emphasizes the groundbreaking potential of metal oxide nanocomposites (NCs) formed by combining them with graphene, carbon nanotubes (CNTs), and polymers, leading to synergistic enhancements in electrical conductivity, surface area, and charge storage capacity. This thorough review not only presents an in-depth analysis of current research but also sheds light on potential future developments, contributing to the ongoing progress in the field of advanced electrode materials for energy storage.