Diffusion Of Electrolyte Ions Research Articles

Hierarchical porous MXene film with diffusion path optimization for supercapacitor

MXenes have immense potential in electrochemical energy storage owing to their outstanding physicochemical properties such as their oxygen-containing groups that impart additional pseudocapacitance to acidic electrolytes. However, during electrode assembly, MXene nanosheets undergo restacking because of hydrogen bonding and van der Waals forces, which causes electrolyte ions to traverse long diffusion pathways between the long and narrow nanosheets. Exploiting the oxidative properties of Ti3C2Tx, a hierarchical porous MXene film with micro-, meso- and macroporous structures was successfully prepared using a simple hydrothermal oxidation and etching process to create micro- and mesoporous structures, followed by ice templating to prepare three-dimensional (3D) linked macroporous structures. Because these hierarchical pores have synergistic effects on electrochemical activity and electrolyte ion diffusion, the film attained a specific capacitance of 539F/g at a current density of 2 A/g when it was used as a supercapacitor electrode, which corresponds to one of the highest values reported for MXene-based electrodes. The film retained 83% of its specific capacitance when the current density was increased to 40 A/g, and exhibited excellent cycling stability. By using this multi-porous MXene design, synergistic improvement in ion diffusion was successfully realized and thus a new strategy to prepare high-performance supercapacitor electrode materials was developed.

FeSnO3/rGO nanocomposite electrode development for supercapacitor application

The manufacturing of electrode materials that are both highly efficient and cost-effective is crucial for energy storage systems. Because of their remarkable performance, nanocomposite materials are a good choice for creating energy storage systems. And the present study contains the fabrication of FeSnO3 and FeSnO3/rGO nanocomposite by hydrothermal approach. To assess electrochemical behavior of FeSnO3 and FeSnO3/rGO nanocomposite number of analytical tools such as galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry (CA) were employed. FeSnO3/rGO nanocomposite demonstrate specific capacitance (Csp) 1342.02 F/g and energy density (Ed) was 88.74 Wh/kg at a power density (Pd) of 345 W/kg at a current density of 1.0 A/g. The charge transfer resistance (Rct) of FeSnO3/rGO nanocomposite was found to be Rct = 0.43 Ω which was determined from Nyquist plot as well as showed cycling stability even after remains 5000th cycles. The addition of rGO increased the specific capacitance as well as surface area rise total number of active sites which allows electrolyte and electrode surface to make ideal connection for quick electrolyte ion diffusion. In accordance with the obtained findings, the FeSnO3/rGO nanocomposite is convincing capacitive electrode material for energy storage devices the future.

Plasma-assisted surface modification of MXene/carbon nanofiber electrodes for electrochemical energy storage

Inferior ion diffusion and relatively low electrochemically active sites of MXene-based electrodes make them becoming a major challenge to develop advanced electrode. Surface modification of electrodes using non-thermal plasma is a great way to suppress these challenges through providing more space for energy storage and facilitating the diffusion of electrolyte ions. Herein, the effect of nitrogen and oxygen plasma treatments on MXene/carbon nanofiber electrode is reported to enhance the electrochemical performance. In this work, Ti3C2Tx MXene/CNF composites were fabricated using a hybrid needleless electrospinning/plasma method for the electrochemical energy storage. Surface modification of the composites was performed by a DBD plasma reactor under N2 and O2 gases at low-pressure glow discharge as a two-step plasma treatment process. The results revealed that total pore volume and the surface area of the plasma-treated Ti3C2Tx/CNF composite increased considerably due to the N2 and O2 plasma treatments. It was found that the electrochemical active surface area of the N2/O2-plasma-treated Ti3C2Tx/CNF electrode enhanced by approximately two times compared to the non-treated one, leading to the specific capacitance of 162 F/g at 1 A g−1 in a 2 M KOH electrolyte. The increase in electrochemical activity arises from separate doping of N2 and O2 plasma, which not only improves the pore structure and wettability, but also modifies the electrical conductivity and capacitance of the electrode. The N2/O2-plasma-treated Ti3C2Tx/CNF electrode achieved excellent cycling stability with 124 % capacitance retention after 10,000 cycles, while the capacitance retention of the pure N2 and O2-plasma-treated Ti3C2Tx/CNF electrodes as well as the non-treated one were 111 %, 105 % and 98 %, respectively. Additionally, an asymmetric supercapacitor N2/O2-plasma-treated Ti3C2Tx/CNF//AC based on the N2/O2-plasma-treated Ti3C2Tx/CNF as a positive electrode and activated carbon (AC) as a negative electrode was successfully constructed, which demonstrated an energy density of 26.3 Wh kg−1 with a power density of 750 W kg−1 at the current density of 1 A g−1 with excellent capacitance retention (102 %) after 5000 cycles. This work provides a highly efficient method for the surface modification of MXene-based electrodes through non-thermal plasma treatment.

Superior performance of asymmetric supercapacitor based on Cu doped bismuth ferrite electrode

Electrochemical energy storage devices, like supercapacitors and batteries, are needed to meet the constantly increasing demands of portable energy devices. Many types of supercapacitor electrodes were synthesized and reported which include carbon-based materials, polymers, oxides and perovskites. In this work, we report on the fabrication of Cu doped bismuth ferrite (Cu-BiFeO3, Cu-BFO) nanoparticles via sol-gel procedure. In most of the doping cases the costly rare earth elements like La, Nd, Sm, Ce and Yb are used to replace Bi. Electrodes of Bi1-xCuxFeO3 where x have the values 0.0, 0.025, 0.05, 0.075, 0.1 and 0.15 were deposited on graphitic sheets. Optimum Cu doping value was found to be at x = 0.05. Cu2+ ions doping in place of Bi3+ ions will reveal the roles of oxygen vacancies, as determined from XPS. The estimated values of specific capacitance was found to be 732 F/g at 0.5 A/g for the electrode at x = 0.05 in three electrode system. 5%Cu-BFO//Carbon black asymmetric supercapacitor (ASC) device can be charged and discharged reversibly at cell voltage of 0.0 up to 1.5 V when using a 0.5 M Na2SO4 aqueous electrolyte. This configuration allows the ASC device to deliver a great energy density of 37.25 Wh/kg at a power density of 752 W/kg. The ASC device demonstrates excellent cycling stability, retaining 88.64 % of its initial specific capacitance after 5000 cycles. Increasing the Cu content up to 15 % causes instability in the crystal structure of BFO resulting on phase segregation into Bi2Fe4O9 along with BFO and deterioration in the electrode overall performance. XPS showed that replacement of Cu2+ in place of Bi3+ disturbs the neutrality and the chemical environment of the compound. Hence to achieve neutrality and ionic balance, oxygen vacancies increase and the Fe2+/Fe3+ ratio increases as well. Both oxygen vacancies and the change in the Fe ions ratio reduce electrochemical impedance and give rise to charge density. The homogenous distribution of the pores at x = 0.05 contributed greatly to its fast electrolyte ion diffusion that improved the observed capacitive properties. One has to mention here, that despite doping that contains ions with different ionic size and/or different oxidation state is unfavorable, to some extent, due to the changes they produce in the electronic structure and the chemical environment, nevertheless it is sometimes beneficial in creating new parameters in the structure that promote specific application like in the case of the current work, oxygen vacancies, increase in surface area and the mixed state valency.

Advanced 3D Micro‐Electrodes for On‐Chip Zinc‐Ion Micro‐Batteries

AbstractThe development of high‐performance planar micro‐batteries featuring safer, cost‐effective systems is crucial for powering smart devices such as medical implants, micro‐robots, micro‐sensors, and the Internet of Things (IoT). However, current on‐chip micro‐batteries suffer from limited energy density within constrained device footprints due to challenges in effectively loading high‐capacity active materials onto micro‐electrodes. Innovative designs for advanced micro‐electrodes are needed for on‐chip micro‐batteries. This work introduces advanced, highly porous 3D gold (Au) scaffold‐based interdigitated electrodes (IDEs) as current collectors, which enable effective loading of active materials (Zn and polyaniline) without compromising overall conductivity and significantly increase active mass loading. These 3D Au scaffold‐based micro‐batteries (3D P‐ZIMB) offer substantially higher energy storage performance (≈135% enhancement) compared to conventional micro‐batteries (C‐ZIMB) when materials loaded onto flat Au IDEs. Furthermore, the 3D P‐ZIMB demonstrates higher areal capacities (≈35 µAh cm−2) and areal energy (≈31.05 µWh cm−2) than most high‐performance on‐chip micro‐batteries, and it delivers a much higher areal power (≈3584.35 µW cm−2) than high‐performance on‐chip micro‐supercapacitors. In‐depth postmortem investigations reveal that the 3D P‐ZIMB avoids issues like material peeling, sluggish electrolyte ion diffusion, and dendrite formation on the anode, while maintaining identical material morphologies and structural characteristics. Therefore, this study presents a smart strategy to enhance the electrochemical performance of planar micro‐batteries and advance the field of on‐chip micro‐battery research.

Design and optimization of pore structure in three-dimensional micro-nano hierarchical SnOx supercapacitor electrodes for enhanced ion diffusion

This paper introduced a novel continuous electrochemical synthesis strategy to address the challenges of slow ion/electron transport rates and low electrode reaction efficiency in Sn-based electrode materials. This approach leveraged the induction and confinement of bubble templates to assist atoms deposition, generating micron-sized tin skeletons. Subsequently, these skeletons were transformed into a secondary nanoporous structure through dissolution-deposition etching effects. From liquid-phase ions to metal skeletons to porous oxides, the sequential material transformations realized the innovative design of three-dimensional (3D) hierarchical structures. This strategy ingeniously exploited the diffusion advantages of the electrolyte in the micro-nano hierarchical structure to achieve the diffusion enhancement of ions, thus solving the “dead surface” problem in the energy storage process. This study revealed the thermodynamic and kinetic feasibility of the constructed 3D micro-nano hierarchical structure through electrochemical evaluations and theoretical calculations, and elucidated the constitutive relationship in which the electrochemical performance of the electrode materials was enhanced with decreasing pore size. In addition, design optimization of pore structures and modelling exploration of pore size limit values were conducted based on density functional theory (DFT) simulations. These simulations demonstrated the advantages of hierarchical structures with controllable pore sizes in facilitating electrolyte ion diffusion, predicting an optimal pore size of 55 μm for 3D hierarchical porous SnOx electrodes. The integration of this innovative structural design with simulation insights offered significant implications for enhancing the sluggish electrode reaction kinetics of metal oxide electrode materials, advancing the controllable fabrication of high-performance energy storage devices.

Building mesoporous channels in lignin-derived microporous carbons to remold the electrochemical behaviors of supercapacitors

The mesoporous structure of the porous carbon electrodes could promote the in-pore diffusion of electrolyte ions. However, the effect of large mesopores with pore sizes larger than 20 nm in the microporous carbons on the diffusion of different electrolyte ions remains unclear. Herein, porous carbon electrodes with mesopores sizes of 23 nm and 40 nm, respectively, are prepared using the ZnO as a hard template. The electrochemical behavior of porous carbon electrodes with large mesopores and microporous carbon electrodes in different sulfate electrolytes are studied and compared. Electrochemical impedance spectroscopy (EIS) tests demonstrate that the wide and short diffusion path provided by large mesopores can reduce the hindrance of multivalent metal cations and SO42−, thus significantly improving the diffusion efficiency of the multivalent metal sulfate cations. Due to the small size and low valence of monovalent metal ions, it is difficult for large mesopores to promote the diffusion of monovalent metal sulfate ions. Therefore, the large mesopores have little impact on the diffusion of monovalent metal ions, whereas they significantly enhance the diffusion of multivalent metal ions.

Nickel-Copper Bimetallic Oxide Nanoparticles Prepared by Simple Coprecipitation Method as High Performance Electrode Materials for Asymmetric Supercapacitors.

Supercapacitors with transition bimetallic oxides as pseudocapacitive materials have been of wide concern for their excellent energy storage performance. In this work, a simple coprecipitation method was used to synthesize the precursor, followed by calcination to prepare Ni-Cu bimetallic oxide materials. The structure, morphology and properties of the materials prepared by different precipitating agents and different calcination temperatures of NCO-H2C2O4 precursor were investigated. The optimum precipitant was determined to be H2C2O4, and Ni-Cu nanoparticles with regular lamellar microstructure were obtained at the calcination temperature of 400 °C. The nanostructure and morphology provide a large active channel for the rapid diffusion of electrolyte ions, and the specific capacitance of NCO-H2C2O4-400 electrode material can reach 740.31 F/g Cs at 1 A/g. The investigation of charge storage mechanism shows that the contribution rate of capacitance and diffusion control is about 37.9% and 67.2%, respectively. The electrochemical test results of the asymmetric supercapacitors (ASC) constructed with NCO-H2C2O4-400 and activated carbon show that the specific capacitance, energy density, and power density of the capacitor are 52.66 F/g, 16.45 Wh/kg, and 759.51 W/kg, respectively. Even after 5000 charge/discharge cycles at 5 A/g, it can still keep 90.57% of its initial capacity. This work not only provides competitive electrode materials for energy storage devices but also provides a feasible strategy for producing complex transition metal oxide materials with high capacitance performance.

Improved-quality graphene films via the synergism of large nanosheet aligning and nanotube bridging for flexible supercapacitors

Scalable production of reduced graphene oxide (rGO) films with high mechanical-electrical properties is desirable as these films are candidates for wearable electronics devices and energy storage applications. Removing structural incompleteness such as wrinkles or voids in the graphene films, which are generated from the assembly process, would greatly optimize their mechanical properties. However, the densely stacked graphene sheets in the films degrade their ionic kinetics and thus limit their development. Here, a horizontal-longitudinal-structure modulating strategy is demonstrated to produce enhanced mechanical, conductive, and capacitive graphene films. Typically, two-dimensional large graphene sheets (LGS) induce regular stacking of graphene oxide (GO) during the assembly process to reduce wrinkles, while one-dimensional single-walled carbon nanotubes (SWCNT) bridge with graphene sheets to strengthen the multidirectional intercalation and reduce GO layer restacking. The simultaneous incorporation of LGS and SWCNT synergistically creates a fine microstructure by improving the alignment of graphene sheets, increasing continuous conductive pathways to facilitate electron transport, and enlarging interlayer spacing to promote electrolyte ion diffusion. As a result, the obtained graphene films are flat and exhibit signally reinforced mechanical properties, electrical conductivity (38727 S m-1), as well as specific capacitance (232 F g-1) as supercapacitor electrodes compared to those of original rGO films. Moreover, owing to the comprehensive improved properties, a flexible gel supercapacitor assembled by the graphene film-based electrodes shows high energy density, good flexibility, and excellent cycling stability (93.8% capacitance retention after 10 000 cycles). This work provides a general strategy to manufacture robust graphene structural materials for energy storage applications in flexible and wearable electronics.

A novel benzoquinone‐azo linked polymer‐based active electrode material for high‐performance symmetric pseudocapacitors

AbstractPseudocapacitors (PSCs) have attracted researcher's attention due to their potential electrochemical performance as the power source for electronic devices. However, to maintain the high electrochemical properties of pseudocapacitive materials becomes critical. Therefore, the active electrode materials design and synthesis is a challenging task. To tackle these problems, herein, we rationally designed new polymer based on benzoquinone with azo linker. The polymer AZO‐BQ‐P was synthesized and tested for their energy storage applications in combination with graphite foil (GF). In three‐electrode supercapacitor (SC) device, the AZO‐BQ‐P/GF electrode exhibits excellent specific capacitance (Csp) of about 306.27 F g−1 at 0.5 A g−1 current density and higher cycling stability. The pseudocapacitive performance of SC cells result from synergistic effect of AZO‐BQ‐P and GF and due to faster electrolyte ion diffusion and increased availability at electrode/electrolyte interfaces. Furthermore, AZO‐BQ‐P/GF electrode was employed to fabricate two‐electrode AZO‐BQ‐P/GF//AZO‐BQ‐P/GF symmetric SC device. The optimal SSC device shows a Csp reaching 200 F g−1 at 0.5 A g−1, which is an impressive value. Also, it exhibits remarkable cycling stability with 86.18% Csp retention after 5000 galvanostatic charging–discharging (GCD) cycles at 3 A g−1. The SSC device applying AZO‐BQ‐P/GF electrode delivers an excellent energy density (ED) of 25.00 Wh kg−1 at 900.00 W kg−1 power density (PD). Thus, the novel polymer design offers efficient electrode materials to enhance the pseudocapacitive electrochemical performance of the SSC device. This concept can be extended for fabricating other electrochemical systems and accelerate its applications for modern electronic devices.

Fast and green synthesis of battery-type nickel-cobalt phosphate (NxCyP) binder-free electrode for supercapattery

Binder-free electrodes are increasingly important in energy storage technologies owing to the direct growth of active material on conducting substrates without binders, providing a shorter conduction channel for rapid electron transport. Various methods have been employed to synthesize binder-free electrodes, but most approaches often prove time-consuming, and some require elevated synthesis temperatures. Herein, a rapid and eco-friendly microwave-hydrothermal method was introduced to fabricate the battery-type nickel–cobalt phosphate (NxCyP) binder-free electrodes for supercapattery. The use of microwave accelerates heating and reduces the activation energy of the reaction, resulting in shorter synthesis time and lower reaction temperature. The NxCyP electrodes were fabricated at different parameters, such as temperature (90–200 °C), time (5–20 min), and Ni:Co precursor ratios (4:0, 3:1, 2:2, 1:3, 0:4). The optimization study was carried out via Design Expert v13 software, and the optimized parameter was the temperature of 123.5 °C, duration of 10.5 min, and Ni:Co of 2:2, namely N2C2P binder-free electrode. The N2C2P electrode exhibited larger flake- and flower-like morphologies, providing more space for electrolyte ion diffusion and a larger surface area for faradaic reactions. Consequently, it demonstrated outstanding electrochemical performance by displaying a high specific capacity (1699.7C/g at 3 mV/s), superior capacity retention, and the lowest resistances than other NxCyP electrodes. As a result, the N2C2P//AC supercapattery was created by merging it with an activated carbon (AC) electrode, showing a superior energy density (213.0 Wh/kg) and high electrochemical stability with 92.9 % retention after 3000 cycles at 10 A/g.

Copper(II)-Tannic Acid@Cu with In Situ Grown Gold Nanoparticles as a Bifunctional Matrix for Facile Construction of Label-Free and Ultrasensitive Electrochemical cTnI Immunosensor.

Sensitive detection of cardiac troponin I (cTnI) is of great significance in the diagnosis of a fatal acute myocardial infarction. A redox-active nanocomposite of copper(II)-tannic acid@Cu (CuTA@Cu) was herein prepared on the surface of a glassy carbon electrode by electrochemical deposition of metallic copper combined with a metal stripping strategy. Then, HAuCl4 was in situ reduced to gold nanoparticles (AuNPs) by strong reductive catechol groups in the TA ligand. The AuNPs/CuTA@Cu composite was further utilized as a bifunctional matrix for the immobilization of the cTnI antibody (anti-cTnI), producing an electrochemical immunosensor. Electrochemical tests show that the immunoreaction between anti-cTnI and target cTnI can cause a significant reduction of the electrochemical signal of CuTA@Cu. It can be attributed to the insulating characteristic of the immunocomplex and its barrier effect to the electrolyte ion diffusion. From the signal changes of CuTA@Cu, cTnI can be analyzed in a wide range from 10 fg mL-1 to 10 ng mL-1, with an ultralow detection limit of 0.65 fg mL-1. The spiked recovery assays show that the immunosensor is reliable for cTnI determination in human serum samples, demonstrating its promising application in the early clinical diagnosis of myocardial infarction.

Self-discharge suppression by composite regenerated cellulose ion-selective separator for high-energy aqueous supercapacitors

Aqueous supercapacitors exhibit the advantage of high cycling stability, inherent safety and appealing energy density, and thus have long been considered an exceptional technology for efficient energy storage. However, in the absence of an electric field, the spontaneous transmembrane diffusion of ions leads to self-discharge or energy decay of supercapacitors. Herein, we propose a phase transformation strategy to design a porous regenerated cellulose and polyvinylidene difluoride composite separator with ion selectivity by utilizing cellulose dissolution regeneration with PVDF enhancement. Specifically, the anion selective property of PVDF screens the transmembrane diffusion of electrolyte ions, thereby suppressing the self-discharge of supercapacitors. The in-depth characterization indicated that the RC@PVDF separator applied to aqueous supercapacitors demonstrated high performance by maintaining a capacitance of 173 F g−1 after 20,000 cycles. After 24 h of self-discharge, the supercapacitor retained 59 % of its energy. In addition, the cross-linked network of regenerated cellulose provides critical properties for the ion-selective separator, including strong mechanical stability, excellent thermal stability (220 °C) and uniform pore structure (31 nm). This work is anticipated to provide considerable insight into the creative design of self-discharge suppression separators for long-term energy storage supercapacitors.

Electrochemical evaluation of low crystalline CoFe2O4@Reduced graphene oxide nanocomposite for hybrid supercapacitor application

The development of high-performance and cost-effective energy storage materials remains of significant scientific interest. Here, low-crystalline (LC) binary transition metal oxide (BTMO) CoFe2O4 is studied for its application in a hybrid supercapacitor. This disordered LC CoFe2O4 material was prepared by the co-precipitation method, and to improve the electron transport property of the LC CoFe2O4, a composite was prepared with reduced graphene oxide (RGO). LC CoFe2O4@rGO interconnected network enhances the electrolyte ion diffusion within the material. This CoFe2O4@RGO shows an electrochemical performance of 2247.82 mF cm−2 at a current density of 1 mA cm−2. The cyclic stability study is performed to CF@RGO 20 % electrode for 2000 cycles at 30 mA cm−2 current density. Further, to understand the charge storage mechanism, Dunn analysis is done, the capacitive and diffusion contributions to charge storage are studied. Besides, the charge transfer and diffusion characteristics of the material were studied using electrochemical impedance spectroscopy. So, these LC CoFe2O4@RGO based materials with improved ion diffusivity and flexibility in synthesis make them attractive candidates for the development of high-performance and cost-effective supercapacitor.

Waste-to-energy material: Winery-waste derived heteroatoms containing graphene-like porous carbon for high-voltage supercapacitor

Recycling industrial waste to produce energy and storage materials provides the best means of addressing its environmental impact and achieving economic benefits. This study used solid industrial winery waste to prepare an innovative heteroatom containing graphene-like porous carbon (HGPC) by simple heat treatment and chemical activation using KOH. The prepared N and S containing HGPC had a thin sheet-like structure, a high specific surface area (925.00 m2/g), and a micro-meso-porosity suitable for sustainable energy storage applications. A density functional theory investigation indicated that the synergistic effects of N and S co-doping enhanced both conductivity and electrolyte ion (Na+) diffusion kinetics in HGPC samples. When the solid winery waste-derived HGPC was used in a supercapacitor (SC) cell assembly with a diglyme-based electrolyte, it delivered an operating voltage window of 2.0 V, which was about twice as wide as those reported for symmetric SCs and compared well with those of asymmetric/hybrid SCs. In addition, it had a specific capacitance of 32 F/g (at the cell level) with a high energy density of 17.7 Wh/kg at a power density of 303.42 W/kg and excellent cycling stability over 10,000 charge/discharge cycles. This work shows that the solid winery waste-derived HGPC can be utilized for future SCs technology by replacing costly commercial YP-50F carbon to provide enhanced energy storage in a sustainable, green manner.

Hierarchical porous carbon originated from the directing associated with activation as high-performance electrodes for supercapacitor and Li ion capacitor

A template-directing methodology combined with post-activation methodology is developed to synthesize hierarchical porous carbon (HPC) with a unique nanocage-like morphology and exceptional structural integrity, utilizing light MgO nanocapsules as templates and coal pitch as precursor. The specific surface area and pore volume of HPC can be precisely adjusted by varying the mass ratio between the chemical activator and PC. This optimized pore structure significantly enhances the kinetics of electrolyte ion diffusion, which is a crucial point for the high-performance supercapacitors. The superior capacitive energy-storage behavior with respect to capacitance and rate capability (168 and 160 F g−1 at 1 and 100 A g−1) can be delivered by HPC electrode as compared to commercial activated carbon and pristine PC. The great compatibility to high gravimetric and areal capacitances (173 F g−1 and 1391 mF cm−2) can still be achieved even at 8 mg cm−2 for HPC electrode. Moreover, a full hybrid Li ion capacitor fabricated using HPC, delivers outstanding rate capability, excellent Ragone performance, and exceptional cyclability, establishing the potential of this material for advanced energy storage systems. The successful integration of template-directed synthesis with activation techniques presents a scalable approach to convert coal pitch into high-performance electrode materials.

Synthesis and Electrochemical Characterization of ZnMoS4 Nanorods on Nickel Foam Substrate for Advanced Hybrid Supercapacitor Applications.

A single-step hydrothermal method was utilized to grow ZnMoS4 (ZMS) nanorods uniformly. Initially, [MoS4]2- and Zn2+ ions interacted to create active nucleation centers, which then led to the formation of primary particles. These particles then underwent spontaneous aggregation and self-assembly on the nickel foam (NF) substrate, which served as a superior 3D interconnecting network template. This aggregation occurred nearly perpendicular to the NF and promoted the uniform growth of ZMS nanorods. The nanorods structure ensures efficient and rapid electrolyte accessibility and ion diffusion, resulting in an increased specific capacitance (Cs) of 2,116 Fg1- (846.4 C g-1) at 1 A g-1 and maintaining about 90% of their capacitance after 10,000 cycles of galvanic charge-discharge (GCD). In a hybrid supercapacitor configuration, ZMS@NF//AC@NF achieved a peak specific power of 7.2 kW.kg-1 and a specific energy of 40.3 Wh.kg-1. Remarkably, it preserved 93% of its initial capacitance after more than 20,000 cycles. These findings affirm the potential of binder-free ZMS nanorods as effective positive electrodes in advanced hybrid supercapacitors.

Nano ZIF-67/PBA derived core-shell sulfides or phosphides for enhanced electrochemical performance of supercapacitors

Metal-organic frameworks (MOFs) possess large specific surface area, high porosity, and adjustable pore size, exhibiting a broad prospect in the field of supercapacitors. However, the poor stability and conductivity of MOFs limited their application in energy storage. The structure of MOF composites and their derivatives are beneficial for storing electric charge and boosting the diffusion of electrolyte ions. In this study, we prepared heterostructured ZIF-67/Prussian blue analogues (PBA) derived sulfides and phosphides using the hydrothermal and solid-phase phosphating method, respectively. The ZIF-67/PBA composites with an average particle size of approximately 1100 nm, retained the rhombic dodecahedral shape of ZIF-67. Compared with MOF-derived phosphides, MOF-derived sulfides more completely retained the rhombic dodecahedron morphology of ZIF-67/PBA and demonstrated good electrochemical performance, especially ZPS-3. The unique core-shell nanostructure provides more active sites and suitable ion transport paths for reversible oxidation-reduction reactions. In three-electrode system, the ZPS-3 electrode exhibited a specific capacity of 603.9 F g−1 at a current density of 0.5 A g−1, superior rate performance, and excellent cycle stability. This study established a new synthesis paradigm for the development of MOF derivatives as a potential class of electrode materials for supercapacitors.

Hierarchical heterostructures of MXene and mesoporous hollow carbon sphere for improved ion accessibility and rate performance

The development of electrode materials with a hierarchically porous structure and good electrical connection is key to improving the charging-discharging rate and energy density of supercapacitors. However, the restacking issue of two-dimensional nanomaterials, such as MXene, seriously hinders the diffusion of electrolyte ions. Different from the extensively used sacrificing template method, a hierarchical heterostructure of electrically conducting mesoporous hollow carbon spheres (MHCS) and MXene composite electrode is designed and achieved through simple vacuum filtration without further template removing procedures. This direct preparation strategy not only effectively improves the specific surface area of the electrode but also enhances the abundant surface pores and good conductivity of MHCS, improving the penetration of the electrolyte solution and shortening the ion transport path, leading to a pronounced improvement in specific capacitance and rate performance of the electrodes. Additionally, the influence of sheath thickness of MHCSs on ion transfer rate is deeply discussed. The introduction of carbon nanotubes (CNTs) further improves conductivity and stability while maintaining good flexibility. Consequently, the MXene/MHCS/CNT film delivers a high specific capacitance (395F g−1 at 2 mV s−1), outstanding rate performance (70.9 % at 1000 mV s−1), and excellent cycling stability (98.3 % capacity retention after 10,000 cycles). Furthermore, the assembled symmetric supercapacitor provides a maximum energy density of 14.48 Wh kg−1. This work provides a quick and effective approach for constructing high performance 3D MXene architectures for fast ion transfer electrodes.

Cathode|Electrolyte Interface Engineering by a Hydrogel Polymer Electrolyte for a 3D Porous High-Voltage Cathode Material in a Quasi-Solid-State Zinc Metal Battery by In Situ Polymerization.

This work highlights the development of a superior cathode|electrolyte interface for the quasi solid-state rechargeable zinc metal battery (QSS-RZMB) by a novel hydrogel polymer electrolyte using an ultraviolet (UV) light-assisted in situ polymerization strategy. By integrating the cathode with a thin layer of the hydrogel polymer electrolyte, this technique produces an integrated interface that ensures quick Zn2+ ion conduction. The coexistence of nanowires for direct electron routes and the enhanced electrolyte ion infiltration and diffusion by the 3D porous flower structure with a wide open surface of the Zn-MnO electrode complements the interface formation during the in situ polymerization process. The QSS-RZMB configured with an integrated cathode (i-Zn-MnO) and the hydrogel polymer electrolyte (PHPZ-30) as the separator yields a comparable specific energy density of 214.14Whkg-1 with that of its liquid counterpart (240.38Whkg-1, 0.5MZn(CF3SO3)2 aqueous electrolyte). Other noteworthy features of the presented QSS-RZMB system include its superior cycle life of over 1000 charge-discharge cycles and 85% capacity retention with 99% coulombic efficiency at the current density of 1.0Ag-1, compared to only 60% capacity retention over 500 charge-discharge cycles displayed by the liquid-state system under the same operating conditions.