Advanced Electrode Research Articles

Investigating the influence of copper benzene-1,2-dicarboxylate (Cu-BDC) and benzene-1,3,5-tricarboxylate ligands (Cu-BTC) on the electrochemical capacity of hybrid supercapacitors

The elevated energy demand and crises have rooted the urge to develop advanced electrode materials that can overcome the energy dilemma present all over the globe. Metal-organic frameworks (MOFs) have emerged as promising electrode materials in recent times due to their better electrochemical properties. Herein the metal ligand synergy produced in MOFs is observed for the same metal center (Cu) with different ligands i.e., benzene-1,3,5-tricarboxylate (1,3,5-BTC) and benzene-1,2-dicarboxylate (1,2-BDC). The hybrid device of the best performing MOF (Cu-1,3,5-BTC//AC) reveals the energy and power density of 88.32 Wh kg−1 and 680 W kg−1, respectively. Even at the highest current density of 15 A/g, the device retained the Es of 21.25 Wh kg−1 and Ps of 12,750 W kg−1. Furthermore, the semi-empirical approach was utilized for the evaluation of capacitive and diffusive contributions.

Rational design of hierarchical porous reduced graphene oxide/9,10-phenanthraquinone/porous carbon nanocomposites for high-performance supercapacitors

The development of advanced electrode material is crucial for promoting the application of new high-performance green energy storage devices and remains a great challenge. Herein, by introducing porous carbon (PC) or carbon nanotubes (CNTs) to further modify the redox-active 9,10-phenanthrenequinone (PQ) molecule non-covalently functionalized reduced graphene oxide (RGO), we have designed and synthesized RGO/PQ/PCs (RPPs) and RGO/PQ/CNTs-10 (RPC-10) nanocomposites using a simple one-step solvothermal method. Benefiting from the optimization of the hierarchical porous nanostructures and each composition further strengthens their respective advantages in the novel synthesized nanocomposites (RPPs and RPC-10), the RPPs and RPC-10 electrodes demonstrated significantly superior electrochemical energy storage performance over the RGO and RGO/PQ (RP) electrodes, especially for the RPP-10 electrode with a high specific capacitance of 343.5 F g−1 at 0.5 A g−1 and good rate capability (69.23 %, 0.5 − 40 A g−1). Furthermore, both the symmetric supercapacitor assembled with the optimal RPP-10 electrode and the hybrid supercapacitor assembled with the RPP-10 negative electrode and the NCSRC-24 positive electrode previously reported show excellent energy densities and ultra-long cycling stabilities. This result demonstrates that the synthesized novel RPP-10 nanocomposite is a highly promising candidate for new light-weight, sustainable, high-flexible and high-performance energy storage devices.

Nanoarchitectonics and electrocatalytic properties of platinum nanoparticles in weak polyelectrolytes‐based multilayer thin films

AbstractIn this study, the electrocatalytic behavior of platinum (Pt) nanoparticles (NPs) in a novel multilayered thin film is investigated for proton exchange membrane fuel cells (PEMFC) applications. The multilayer thin films are assembled by the alternate deposition of branched polyethylenimine (BPEI) and poly(acrylic acid) (PAA) from aqueous solutions through a layer‐by‐layer (LbL) technique. Two extreme assembly pH conditions critically influence the films' physical and morphological characteristics, subsequently affecting their electrochemical behavior. Manipulation of the assembly pH modifies the charge density of the weak polyelectrolytes (BPEI and PAA), leading to variations in physical, structural, and electrochemical properties. The LbL thin films assembled at a pH of 9.5 for BPEI and 4.5 for PAA exhibit significantly greater thickness compared to the same film with all components deposited at pH 4.5. This is attributed to in‐and‐out diffusion of the partially charged polyelectrolytes with coiled polymeric conformation (BPEI at pH 9.5 and PAA at pH 4.5). As‐assembled LbL thin films are used as nanoreactors for the deposition of Pt NPs. The nanoscale control over polymeric conformation and charge density significantly influences electrocatalytic performance. 9.5BPEI/4.5PAA thin films exhibit higher electrocatalytic activity relative to 4.5BPEI/4.5PAA systems. This improved performance in 9.5BPEI/4.5PAA multilayers is ascribed to the fact that more carboxylic acid groups of PAA are coated in an exponentially grown behavior, which provides more active sites available for Pt NPs to be deposited. The multilayer thin films containing uniformly dispersed Pt NPs can be an attractive and advanced hybrid electrode material with great promise for the proton exchange membrane fuel cells.

A 2D Metallic KCu4S3 Anode for Fast‐Charging Sodium‐Ion Batteries

AbstractThe search for advanced electrode materials to solve slow ion diffusion and poor conductivity issues has spurred the development of fast‐charging sodium‐ion batteries (SIBs). Herein, a 2D metallic anode, KCu4S3, is reported expertly crafted using a KSCN molten salt approach, laying the foundation for fast‐charging SIBs. It is found that the mixed metal‐valence states within this compound provide substantial advantages, particularly in enhancing the high‐rate capability and ensuring long‐term durability. The mechanism that appears to facilitate these benefits can be traced to the formation of NaCu2S2 intermediate, which assist in electron transfer during Na+ (de)intercalation. In situ observations confirm the sodiation products of NaCu2S2 and sodium polysulfide can recover to the original phase upon desodiation. Such distinctive characteristics endow KCu4S3 with remarkable electrochemical performances, including an impressive capacity of 355 mAh g−1 at 20 A g−1 and 100% capacity retention within 3000 cycles. Moreover, the full cell exhibits a high energy density of 332 Wh kg−1 and retains 92% of its capacity across 150 cycles at 1 A g−1. This work opens new horizons in the field of fast‐charging materials, making a significant step forward in shaping the future of SIBs.

Unveiling the Potential of Covalent Organic Frameworks for Energy Storage: Developments, Challenges, and Future Prospects

AbstractCovalent organic frameworks (COFs) are porous structures emerging as promising electrode materials due to their high structural diversity, controlled and wide pore network, and amenability to chemical modifications. COFs are solely composed of periodically arranged organic molecules, resulting in lightweight materials. Their inherent properties, such as extended surface area and diverse framework topologies, along with their high proclivity to chemical modification, have positioned COFs as sophisticated materials in the realm of electrochemical energy storage (EES). The modular structure of COFs facilitates the integration of key functions such as redox‐active moieties, fast charge diffusion channels, composite formation with conductive counterparts, and highly porous network for accommodating charged energy carriers, which can significantly enhance their electrochemical performance. However, ascribing intricate porosity and redox‐active functionalities to a single COF structure, while maintaining long‐term electrochemical stability, is challenging. Efforts to overcome these hurdles embrace strategies such as the implementation of reversible linkages for structural flexibility, stimuli‐responsive functionalities, and incorporating chemical groups to promote the formation of COF heterostructures. This review focuses on the recent progress of COFs in EES devices, such as batteries and supercapacitors, through a meticulous exploration of the latest strategies aimed at optimizing COFs as advanced electrodes in future EES technologies.

Structural, morphological, optical, and magnetic properties of NiO-added NiCo2O4 electrode materials synthesized by sol-gel, Co-precipitation and ultrasonication methods and their electrochemical supercapacitor response

In this study, NiO-added NiCo2O4 composite samples were prepared using three distinct synthesis methods to study the impact of synthesis technique and NiO addition on the electrochemical performance of NiCo2O4. The chosen methods, sol-gel, co-precipitation, and ultrasonication, represent a range of approaches that yield different particle structures and morphologies. The structural and morphological studies of composite samples were investigated using X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM), respectively. XRD analysis revealed the crystalline composition, revealing the presence of two distinct phases: NiO and NiCo2O4. The Rietveld analysis of the composite samples supports the dual phases in the samples. FESEM analysis confirms the change in size and shape of the particles with the synthesis procedure. Optical properties, measured via UV–visible absorbance spectra, demonstrated that the energy gap varied with the synthesis method. The sol-gel samples exhibited the highest energy gap at 2.20 eV. The magnetic properties were measured using the vibration sample magnetometer (VSM), and the results confirm that the synthesis procedure influences magnetic loops and coercivity. The electrochemical performance of the samples in a 3 M potassium hydroxide electrolyte revealed that the co-precipitation method produced the highest capacitance of 398 Fg-1 at a 10 mV/s sweep rate, indicating superior energy storage capacity compared to pure NiCo2O4. Adding NiO phase to the NiCo2O4 matrix is believed to enhance electrochemical performance by creating additional charge at the grain boundaries, leading to a synergistic effect and improved electron and ion transport. The exceptional electrochemical performance of these composite materials suggests that the synthesis methods and the addition of NiO play a critical role in determining the overall efficiency and applicability of battery-type supercapacitors. These findings pave the way for further research into optimizing synthesis parameters to enhance energy storage capacity and inspire the development of advanced spinel metal oxide composite electrodes for supercapacitors and other energy storage applications.

Nanostructured S@VACNTs Cathode with Lithium Sulfate Barrier Layer for Exceptionally Stable Cycling in Lithium-Sulfur Batteries

Lithium-sulfur technology garners significant interest due to sulfur’s higher specific capacity, cost-effectiveness, and environmentally friendly aspects. However, sulfur’s insulating nature and poor cycle life hinder practical application. To address this, a simple modification to the traditional sulfur electrode configuration is implemented, aiming to achieve high capacity, long cycle life, and rapid charge rates. Binder-free sulfur cathode materials are developed using vertically aligned carbon nanotubes (CNTs) decorated with sulfur and a lithium sulfate barrier layer. The aligned CNT framework provides high conductivity for electron transportation and short lithium-ion pathways. Simultaneously, the sulfate barrier layer significantly suppresses the shuttle of polysulfides. The S@VACNTs with Li2SO4 coating exhibit an extremely stable reversible areal capacity of 0.9 mAh cm−2 after 1600 cycles at 1 C with a capacity retention of 80% after 1200 cycles, over three times higher than lithium iron phosphate cathodes cycled at the same rate. Considering safety concerns related to the formation of lithium dendrite, a full cell Si-Li-S is assembled, displaying good electrochemical performances for up to 100 cycles. The combination of advanced electrode architecture using 1D conductive scaffold with high-specific-capacity active material and the implementation of a novel strategy to suppress polysulfides drastically improves the stability and the performance of Li-S batteries.

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.

Improving of the electrochemical performance of acacia wood porous carbon/MnO2 nanocomposite as an advanced electrode for supercapacitor and oxygen evolution reaction

Effective energy storage has now become increasingly critical as global energy demand has skyrocketed. Asymmetric supercapacitors using electrodes made of acacia wood-derived carbon doped with MnO2. A hydrothermal process was used to synthesize the AWPC/MnO2 composite. Techniques such as XRD, SEM, TEM, XPS, FTIR spectra, Ramman spectra, and N2 adsorption-desorption isotherms. We looked at the electrochemical properties of the materials we made in an electrolyte using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). A hydrothermal synthesis approach is used to graft MnO2 wire-like nanostructures onto acacia wood-derived activated carbon. Good electrochemical performance is shown by the carbon/MnO2 hybrid composite electrode, which has high specific capacitances of 301 F g−1 at 500 mA s−1, low Tafel slope of 54 mV dec−1, which is attributed to the synergistic influences between MnO2 and waste biomass-produced carbon. Moreover, an asymmetric supercapacitor operating in the voltage range of 1.8 V and exhibiting a high energy density of 25 Wh kg−1 at a power density of 450 W kg−1 demonstrates the significant potential of the activated carbon/MnO2 composite generated from synthesized biomass. The AWPC/MnO2's oxygen evolution reaction (OER) activity was checked to see how well the improved nanostructure could be used. The results offer a fresh perspective on the fabrication of electrochemical energy storage devices with outstanding performance.

Scalable flexible and stretchable high performance UV photodetector based on MoS2-WO3/Ag composite on a PU substrate by utilizing LIG electrodes

The rapid advancements in photodetector device technologies have captivated the optoelectronic industry owing to their strong features, such as wearability, stretchability, energy efficiency, scalability and cost-effectiveness. However, there is still scope for enhancement in device performance, reliability, and scalable fabrication. In this research work, we have proposed a novel strategy for fabricating stretchable ultraviolet (UV) photodetector (PD) on a polyethylene glycol solution-processed synthesis of MoS2-WO3/Ag composite-based nanocrystals onto a polyurethane (PU) substrate. Moreover, laser induced graphene (LIG) interdigitated electrode arrays for swift photogenerated charge extraction due to their high conductivity. The device displays high photoresponsivity, external quantum efficiency, and specific detectivity, measured at 6.84 A/W, 143 %, and 2.87×1011 Jones, respectively. Additionally, the device demonstrates a quick response time of 80 ms when exposed to 360 nm light, indicating its high speed. These essential advantages have a great potential for applications in real life and mass production. The integration of advanced materials and LIG electrodes enhances the device capability for next-generation stretchable, flexible and wearable electronic devices.

Synergetic Nitrogen‐Rich Nanocarbon Decoration and Metal Intercalation Enabled Low‐Crystalline V3O7 Hybrids for Boosting Capacitive Sodium Capture

AbstractFaradaic capacitive deionization (FCDI) with attractive ion‐capture capacity, outstanding durability, and potential compatibility in high‐salinity water has been recognized as the robust alternative to address the alarming freshwater scarcity. The further innovation of boosting electrode materials is the indispensable requisite for highly efficient FCDI application. Herein, a low‐crystalline nitrogen‐doped carbon quantum dots modified Mg2+‐pillar preintercalated V3O7 (i.e., NCQDs/Mg‐V3O7) heterostructure is assembled via an ingenious one‐spot hydrothermal avenue, and is investigated as the advanced FCDI electrode for desalination application. Taking advantages of the synergic effect of unique microstructure, improved electronic conductivity, and exceptional structural durability, the NCQDs/Mg‐V3O7 electrode delivers an admirable gravimetric adsorption capacity of 54.32 mg g−1 in a NaCl solution of 1500 mg L−1 and attractive cyclic durability. Further, density functional theory calculations verify the intense interface electron coupling interaction between tri‐components, enabling the significantly promoting Na+ capture capability. The synergy removal mechanism is clarified by ex‐situ X‐ray photoelectron spectroscopy and in‐situ Raman tests. Additionally, the average removal efficiency of hybrid electrode attains 93.75% in the simulated wastewater comprising the NaCl of 50 mg L−1 and diverse metal nitrates from 10 to 100 mg L−1 for each, certifying the great prospects for practical wastewater treatment.

Hollow fiber gas-diffusion electrodes with tailored crystal facets for tuning syngas production in electrochemical CO2 reduction

Electrochemical reduction of CO2 (CO2RR) in aqueous electrolytes not only relies on advanced gas diffusion electrodes (GDEs) to improve CO2 mass transportation but also efficient electrocatalysts to produce specific products. Herein, to produce syngas (CO and H2 mixture), a facet-orientated zinc nanosheet catalyst was electrodeposited on the Cu hollow fiber GDE via a controllable facile surfactant-assisted method. The introduction of cationic surfactant cetyl trimethyl ammonium bromide (CTAB) could manipulate the nucleation and crystal growth of zinc ions around the GDE during the electrodeposition process, leading to controlled changes in the surface free energy and tuned zinc crystal growth orientation. Consequently, the ZncNS-HF with the largest ratio of Zn (101)/Zn (002), resulted in a high current density of 73.3 mA/cm2 and a high syngas production rate of 1328.6 µmol/h∙cm2 at applied potential −1.3 V (vs. RHE). This comes from the hierarchical structure of HFGDE, which provides sufficient CO2 reaching the catalyst/electrolyte interface, and the well-connected zinc nanosheets contribute to a significant number of active sites for CO2RR. This is the first time to configure flow-through or gas-penetrated HFGDEs with zinc crystal facets controlled nanosheet catalysts for syngas production. This research demonstrates the high potential of nanoengineering catalysts for HFGDEs to achieve high production rates of syngas.

Catalyst deactivation during water electrolysis: Understanding and mitigation

Electrocatalyst deactivation poses a significant obstacle to transitioning water electrolysis technology from laboratory-scale to industrial applications. To inspire more effort on this topic, this contribution explores the structural factors contributing to catalyst deactivation, elucidating the underlying mechanisms with detailed case studies of hydrogen and oxygen evolution reactions. In particular, the in situ assessment and characterization techniques are highlighted, which can offer a collective understanding of catalyst deactivation. Building on these insights, recent advances in mitigating catalyst deactivation are introduced, from innovative catalyst designs to advanced electrode engineering. The review concludes by emphasizing the necessity for universal test protocols for deactivation and integrating evidence from diverse in situ measurements, aiming to provide introductive guidance examining the complexities of electrocatalyst deactivation.

Multistage structural self-supported electrode via structural engineering on carbon nanofibers for efficient hydrogen evolution reaction at high current density

Pt-based catalysts suffered from the wastage of active sites, resulting in unsatisfactory actual catalytic performance and poor durability as non-self-supporting catalysts for alkaline hydrogen evolution reaction (HER). In this work, we designed a self-supporting electrode material with multi-level structure that utilized carbon nanofibers anchored with cobalt to load and stabilize Pt nanoparticles (Pt@Co/CNFs) for achieving high activity and stability in alkaline HER. The carbon nanofibers served as a framework, with cobalt nanoparticles as an electron donor that can transfer electrons to the metal Pt to accelerating water splitting. In addition, the morphology of the multi-level structure surface was controlled by the content of the reducing agent to giving the material excellent superhydrophilic/underwater superaerophobic properties with ultra-low Pt load (0.29 mg cm−2), which was beneficial for HER. HER test results showed that Pt@Co/CNFs exhibited great catalytic activity, with η10 = 15 mV and η100 = 101 mV. Besides, the stable mechanical structure and the stability of the designed catalytic surface and electron donor in the multi-level structure gave the material exceptional stability. During the 100-hour stability test at 100 mA cm−2, the voltage change was only 50 mV. Besides, utilizing the Pt@Co/CNFs self-supporting electrode directly in the AEM water electrolysis system, a cell voltage as low as 2.18 V was achieved at 500 mA cm−2. Impressively, it demonstrated operational stability for over 200 h without noticeable decay. This work provides a promising approach for the development of advanced self-supporting electrode catalysts.

Mixed valence Mo2C-MoC/C catalyst enhances polysulfides conversion kinetics in lithium–sulfur batteries

Lithium-sulfur batteries have received extensive attention in the field of electrochemical energy storage systems due to their extremely high theoretical energy density (2600 Wh·kg−1) and low cost. However, poor electrical conductivity, shuttle effect, and volume expansion effect still need to be addressed. Here, we controllably synthesized hollow spherical Mo2C-MoC/C structure as the cathode material for lithium-sulfur batteries. Through high-temperature calcination, the synthesis of graphitized reticular carbon matrix and the loading of Mo2C and MoC nanoparticles with mixed valence of Mo2+ and Mo3+ were simultaneously achieved. The two synergistically improved the electronic conductivity and ensured excellent battery performance. From the experimental results, Mo2C-MoC/C structure strongly adsorbed polysulfides and promoted the conversion of polysulfides to lithium sulfide, accelerating the reaction kinetics and enhancing the battery performance. The initial discharge specific capacity of Mo2C-MoC/C electrode with 57.12 wt% sulfur content was 870.4 mAh·g−1 at 0.2 C, and remained at 770.7 mAh·g−1 at 0.5 C, which was significantly better than that of Mo2C/C/S. The rational design of the Mo2C-MoC/C structure in this study can be generalized to the advanced electrode materials of other Mo-based nanomaterials.

Work-function-prompted interfacial charge kinetics in hierarchical heterojunction flexible electrode for efficient capacitive deionization

The growing challenge of water scarcity has spurred extensive research into the development of advanced freestanding pseudocapacitive electrode materials. These electrodes, characterized by their controlled morphology, mechanical complexity, and enhanced desalination capabilities, are advancing water treatment technologies. Additionally, electrodes with interfacially influenced heterostructures demonstrate substantial potential to enhance electrochemical kinetics. However, their widespread adoption is hindered by intricate synthesis procedures and the necessity for multiple discrete components. Herein, the report introduces a cohesive approach that utilizes electrospinning and carbonization to create a freestanding, hierarchically porous nitrogen-doped carbon nanofiber network encapsulating FeNi3 alloy (FeNi3@CNFs) for desalination applications. The method enhances the interfacial effect, mitigates volume changes during sodium ion adsorption and desorption, and improves interfacial stability. By capitalizing on structural and compositional advantages, the novel FeNi3@CNFs electrode delivers outstanding electrochemical properties, including a high desalination capacity (46.47 mg g−1 at 1.2 V), rapid desalination rate (0.77 mg g−1 min−1), and enhanced cyclic durability. Computational analysis via Density Functional Theory shows that the work function prompts a surface charge redistribution at the FeNi3@CNFs heterojunction, optimizing the surface electronic structure and reducing the energy barrier for adsorption. The modification significantly boosts the diffusion kinetics of sodium adsorption. The study delineates a comprehensive methodology for fabricating high-performance heterostructured electrode materials that are effective for capacitive deionization.

Facile synthesis of MgO-carbon nanocomposites for advanced capacitive electrode materials

Facile synthesis of MgO-carbon nanocomposites for advanced capacitive electrode materials

A simple and effective approach to relieve stress and enhance cyclability of Si-based materials toward high-energy lithium-ion batteries

Silicon-based materials are promising anodes to keep up with the demands for next-generation lithium-ion batteries in the coming decades owing to their ultrahigh theoretical capacities. However, the severe volume changes and mechanical fractures during cycling greatly hinder their way to commercialization. So far, it still remains a great challenge to develop advanced Si-based electrodes with high mechanical stability and remarkable electrochemical properties. In this work, we propose a simple and effective strategy to encapsulate Si@SiOx particles into B, N co-doped carbon nanotubes (BNCNTs) to develop Si@SiOx@BNCNT electrode for enhanced lithium storage. The SiOx layer upon Si particle is designed to mitigate the volume expansion of Si and maintain the particle integrity. Finite element analysis demonstrates that BNCNTs with high mechanical strength can further relieve the internal stress induced by Si expansion upon lithiation. The double restraint effect from SiOx layers and BNCNTs on the Si particles contributes to excellent resistance to structural degradation, enabling high stability and desirable electrochemical performance of Si@SiOx@BNCNT electrode. This strategy provides great opportunities for the practical application of Si-based anodes in high-energy lithium-ion batteries.

Zirconium-based metal–organic frameworks/porous carbon hybrids as high-performance anode materials for highly stable lithium- and potassium-ion batteries

Metal-organic framework (MOF)-derived carbon materials have been widely investigated as advanced electrode materials. However, post-synthetic modifications suffer from certain limitations in morphology, surface area, and pore size control. Herein, we report a simple strategy to synthesize surface-confined Zirconium(Zr)-based MOF UiO-66-NH2 carbon hybrids (Zr-MOF@C; denoted as Zr-MOF, Zr-MOF@C10, Zr-MOF@C25, and Zr-MOF@C50) through a covalent assembly/amide linkage between the MOFs and hierarchical porous carbon (PC) in various proportions under solvothermal conditions. Zr-MOF@C hybrids have been utilized as the anode materials for lithium- (LIBs) and potassium-ion batteries (KIBs). In LIBs, the Zr-MOF@C10, Zr-MOF@C25 and Zr-MOF@C50 anodes delivered the discharge capacities of 126, 65 and 94 mA h g−1 at 100 mA g−1 after 100 cycles, respectively. In KIBs, the Zr-MOF@C10 and Zr-MOF@C25 exhibited the high discharge capacities of 78 and 70 mA h g−1 at 100 mA g−1 over 100 cycles. In addition, the Zr-MOF@C25 and Zr-MOF@C50 anodes exhibited an outstanding rate capability with a reversible capacity of ∼166 mA h g–1 vs. K/K+ and 176 mA h g–1 for Li/Li+, respectively, while well-maintained long-term cyclic stabilities of ∼57 mA h g–1 (Zr-MOF@C25 vs. K/K+) and ∼140 mA h g–1 (Zr-MOF@C50 vs. Li/Li+) at 1 A g–1 over 1000 cycles. The electrochemical kinetics studies revealed that Li+ and K+ storage efficiencies of all anodes were dominated by a surface-charge capacitive effect and diffusion-driven charge storage mechanism, respectively. These findings provide new insights for designing high-performance surface-confined MOF-based carbon composite materials for next-generation high-energy storage devices.

Constructing a mesoporous carbon nanobowls embedded with ultrafine CoSe2 Nanocrystals for High-Performance potassium ion battery electrode

In the quest for advanced electrode materials for potassium ion batteries (KIBs), an innovative anode featuring ultrafine CoSe2 nanocrystals embedded within mesoporous carbon nanobowls (CoSe2@MCNBs) is presented herein. Diverging from conventional hollow carbon nanospheres, the distinctive bowl structure is crafted to enhance the structural integrity and volumetric energy density of the electrodes. CoSe2@MCNBs synthesized using an iterative drop and dry method followed by selenization exhibit well-preserved morphology with a shell thickness of 20 nm. The successful integration of ultrafine CoSe2 nanocrystals into MCNBs imparts the nanobowls with the benefits of conventional hollow carbon-based composites, including abundant ion storage sites and high electrical conductivity. Simultaneously, the bowl structure boasts a higher packing density than the conventional hollow mesoporous carbon sphere (HMCS) structure, significantly augmenting the volumetric energy density of the fabricated electrode. Capitalizing on these advantages, the CoSe2@MCNB electrode displays exceptional cycling stability, achieving a reversible capacity of 523 mA h g−1 after 500 cycles at 0.5 A/g and an impressive rate capacity of 247 mA h g−1 at 2.0 A/g. This study demonstrates the strong potential of CoSe2@MCNB as an electrode material for the next generation of KIBs.