High Electrochemical Performance Research Articles

Effect of B2O3 on the structure, morphology, and electrochemical properties of hierarchical multilayer carbon nanofiber/MnO2/carbon nanofiber composites

One major challenge in capacitor development is achieving high capacitance and large energy density with rapid charge and discharge rates of minutes to seconds. This paper reports boron-containing trilayer structured MnO2/carbon nanofiber composites(PPMnB) as promising supercapacitor electrodes with high electrochemical properties under rapid charge and discharge conditions. Multilayer carbon nanofiber(CNF) composites are designed to maximize the advantages of CNF, MnO2, and boron functional groups when applying functionalized porous CNF containing transition metal composites to supercapacitor electrodes. The PPMnB electrode exhibits a high specific capacitance (215 Fg−1 at 1 mAcm−2), good rate capability (83 % capacity retention at 20 mAcm−2), high energy density (23.5 Whkg−1 at 400 Wkg−1), and good cycling stability (only 6.0 % loss after 10,000 cycles at 1 mAcm−2). In addition, the asymmetric capacitor of the PPMnB(25) and PPB(0) used as the positive and negative electrode shows excellent electrochemical performance, including an excellent energy density of 46.3 Whkg−1 at a maximum voltage of 1.4 V. High electrochemical performance is achieved through the combined effects of the hierarchical porosity of CNF, high electrochemical activity of MnO2, and increased electrical conductivity by boron functional groups in each layer.

Vanadium oxide nanospheres encapsulated in N-doped carbon nanofibers with morphology and defect dual-engineering toward advanced aqueous zinc-ion batteries

Vanadium-based electrodes are regarded as attractive cathode materials in aqueous zinc ion batteries (ZIBs) caused by their high capacity and unique layered structure. However, it is extremely challenging to acquire high electrochemical performance owing to the limited electronic conductivity, sluggish ion kinetics, and severe volume expansion during the insertion/extraction process of Zn2+. Herein, a series of V2O3 nanospheres embedded N-doped carbon nanofiber structures with various V2O3 spherical morphologies (solid, core–shell, hollow) have been designed for the first time by an electrospinning technique followed thermal treatments. The N-doped carbon nanofibers not only improve the electrical conductivity and the structural stability, but also provides encapsulating shells to prevent the vanadium dissolution and aggregation of V2O3 particles. Furthermore, the varied morphological structures of V2O3 with abundant oxygen vacancies can alleviate the volume change and increase the Zn2+ pathway. Besides, the phase transition between V2O3 and ZnXV2O5−m·nH2O in the cycling was also certified. As a result, the as-obtained composite delivers excellent long-term cycle stability and enhanced rate performance for coin cells, which is also confirmed through density functional theory (DFT) calculations. Even assembled into flexible ZIBs, the sample still exhibits superior electrochemical performance, which may afford new design concept for flexible cathode materials of ZIBs.

Fabrication of Asymmetric Supercapacitors (AC@GQDs//AC) with High Electrochemical Performance Utilizing Activated Carbon and Graphene Quantum Dots

Fabrication of Asymmetric Supercapacitors (AC@GQDs//AC) with High Electrochemical Performance Utilizing Activated Carbon and Graphene Quantum Dots

Universal self-assembly of graphene-based composites as free-standing hierarchical electrodes for high-performance aqueous hybrid capacitors

For the development of aqueous hybrid capacitors, it is essential to fulfill the role of active materials and concentrate on the device's performance. However, these goals are challenging because the conventional electrodes meet a heterogeneous distribution of active materials and large-portion passive components. We develop a universal method to prepare free-standing hierarchical graphene-based composited electrodes here. Compared to conventional electrodes, this hierarchical electrode can distribute active materials effectively, improve ion diffusion, increase charge transfer, reduce parasitic reactions, decrease passive components, etc., which facilitates fulfilling the role of active materials and increases the device performance. Typically, the hierarchical electrodes show higher capacity for Fe3O4, NiCo-LDH, PANI, and active carbon. In addition, the hierarchical electrodes can generate a high energy density of 43.7 Wh kg−1 (based on the whole electrodes instead of active materials). Also, the preparation method of hierarchical electrodes is facile, energy-saving, eco-friendly, etc., facilitating the practical application. Such a universal preparation method and high electrochemical performance hold great potential for developing high-performance energy storage devices.

Heterostructured MoO3@CoWO4 nanobelts towards high electrochemical performances via oxygen vacancies generation

Heterostructured nanomaterials tend to have a high proportion of oxygen vacancies (VO) due to the presence of heterogeneous interfaces. Herein, a new kind of heterostructured MoO3@CoWO4 nanobelts was successfully evaluated as fascinating cathode material. SEM and TEM analysis indicated that the MoO3 nanobelts were fully blanketed with CoWO4 nanodots. The generation of Vo species was confirmed by XPS and EPR data. By profiting both synergistic and Vo generation effects, MoO3@CoWO4 electrode displayed an excellent capacitance of 246 mAh·g−1 (1966 F·g-1at 0.5 A·g−1) with high-rate capability of 174 mAh·g−1 (1394 F·g−1 at 30 A·g−1) as well as superb stability of 94 % (over 15,000 cycles). Notably, all-solid-state device delivered a good energy value of 63.1 Wh·kg−1 at 375 W·kg−1. Interestingly, the supercapacitor device showed super-low self-discharge comportment of only 12.1 % during 24 h. Importantly, the generation of the VO defects could control the ions diffusion process and lead a sharp decrease in the self-discharge process.

Delocalized Isoelectronic Heterostructured FeCoOxSy Catalysts with Tunable Electron Density for Accelerated Sulfur Redox Kinetics in Li‐S batteries

AbstractHigh interconversion energy barriers, depressive reaction kinetics of sulfur species, and sluggish Li+ transport inhibit the wide development of high‐energy‐density lithium sulfur (Li−S) batteries. Herein, differing from random mixture of selected catalysts, the composite catalyst with outer delocalized isoelectronic heterostructure (DIHC) is proposed and optimized, enhancing the catalytic efficiency for decreasing related energy barriers. As a proof‐of‐content, the FeCoOxSy composites with different degrees of sulfurization are fabricated by regulating atoms ratio between O and S. The relationship of catalytic efficiency and principal mechanism in DIHCs are deeply understood from electrochemical experiments to in situ/operando spectral spectroscopies i.e., Raman, XRD and UV/Vis. Consequently, the polysulfide conversion and Li2S precipitation/dissolution experiments strongly demonstrate the volcano‐like catalytic efficiency of various DIHCs. Furthermore, the FeCoOxSy‐decorated cell delivers the high performance (1413 mAh g−1 at 0.1 A g−1). Under the low electrolyte/sulfur ratio, the high loading cell stabilizes the areal capacity of 6.67 mAh cm−2 at 0.2 A g−1. Impressively, even resting for about 17 days for possible polysulfide shuttling, the high‐mass‐loading FeCoOxSy‐decorated cell stabilizes the same capacity, showing the practical application of the DIHCs in improving catalytic efficiency and reaching high electrochemical performance.

Delocalized Isoelectronic Heterostructured FeCoOx Sy Catalysts with Tunable Electron Density for Accelerated Sulfur Redox Kinetics in Li-S batteries.

High interconversion energy barriers, depressive reaction kinetics of sulfur species, and sluggish Li+ transport inhibit the wide development of high-energy-density lithium sulfur (Li-S) batteries. Herein, differing from random mixture of selected catalysts, the composite catalyst with outer delocalized isoelectronic heterostructure (DIHC) is proposed and optimized, enhancing the catalytic efficiency for decreasing related energy barriers. As a proof-of-content, the FeCoOx Sy composites with different degrees of sulfurization are fabricated by regulating atoms ratio between O and S. The relationship of catalytic efficiency and principal mechanism in DIHCs are deeply understood from electrochemical experiments to in situ/operando spectral spectroscopies i.e., Raman, XRD and UV/Vis. Consequently, the polysulfide conversion and Li2 S precipitation/dissolution experiments strongly demonstrate the volcano-like catalytic efficiency of various DIHCs. Furthermore, the FeCoOx Sy -decorated cell delivers the high performance (1413 mAh g-1 at 0.1 A g-1 ). Under the low electrolyte/sulfur ratio, the high loading cell stabilizes the areal capacity of 6.67 mAh cm-2 at 0.2 A g-1 . Impressively, even resting for about 17 days for possible polysulfide shuttling, the high-mass-loading FeCoOx Sy -decorated cell stabilizes the same capacity, showing the practical application of the DIHCs in improving catalytic efficiency and reaching high electrochemical performance.

Synthesis of Mo 2C MXene with high electrochemical performance by alkali hydrothermal etching

Synthesis of Mo ₂C MXene with high electrochemical performance by alkali hydrothermal etching

A quasi‐solid polymer electrolyte‐based structural battery with high mechanical and electrochemical performance

AbstractStructural batteries are attractive for weight reduction in electric transportation. For their practical applications excellent mechanical properties and electrochemical performance are required simultaneously, which remains a grand challenge. In this study, we present a new scalable and low‐cost design, which uses a quasi‐solid polymer electrolyte (QSPE) to achieve both remarkably improved flexural properties and attractive energy density. The QSPE has a high ionic conductivity of 1.2 mS cm−1 and retains 91% capacity over 500 cycles in graphite/NMC532 cells. Moreover, the resulting structural batteries achieved a modulus of 21.7 GPa and a specific energy of 127 Wh kg−1 based on the total cell weight, which to our knowledge is the highest reported value above 15 GPa. We further demonstrate the application of such structural batteries in a model electric car. The presented design concept enables the industrialization of structural batteries in electric transportation and further applications to improve energy efficiency and multifunctionality.image

Polyaniline Films Fabricated by Pre‐Nucleation Electrodeposition Method with High Electrochemical Activity: Parameter Optimization and Analysis

AbstractElectrochromic polyaniline (PANI) films with high electrochemical performance have been intensively pursued for their potential applications in various fields. Here, the growth process of the PANI films synthesized by the pre‐nucleation electrodeposition method is analyzed and the optimal parameters with highest electrochemical activity are obtained. The PANI film fabricated under high current density of 10 mA cm−2 and impact time of 0.2 s shows the best electrochemical performance. It has a maximum active charge of 22.3 mC cm−2. The optimum electrochemical performance is attributed to the loose and porous structure. The PANI films fabricated under the optimal parameters also show the flattest structure and the smooth surface. It concludes a universal evaluation basis of the optimal conditions for the pre‐nucleation method. That is, in the nucleation stage, the potential curve shall peak rapidly and then fall slowly to the valley without any upward growth; when entering into the low current density growth stage, the potential shall fall rapidly to a certain value and grow at that potential smoothly. This work evokes a deeper understanding and controlling of the growth process of polymers.

Preparation of a High-Performance Asymmetric Supercapacitor by Recycling Aluminum Paper and Filter Components of Heated Tobacco.

In this study, Al paper and cellulose acetate (CA) filters derived from heated tobacco waste were successfully converted into current collectors and active materials for a supercapacitor device. Typically, heated tobacco contains electrically discontinuous Al paper. First, Al was extracted from the tobacco waste using HCl to produce Lewis acid (AlCl3). This acid was then used in an Al electrodeposition process utilizing the chloroaluminate ionic liquid reaction between the acid and the base (RCl) at room temperature. To enhance the conductivity, a supplementary coating of Al metal was applied to the Al paper through electrodeposition, thus re-establishing the electrical continuity of the discontinuous parts and forming an Al-coated current collector. Moreover, the CA filters were carbonized under a nitrogen atmosphere, yielding carbon precursors (C-CA) for the supercapacitor electrodes. To further enhance the electrochemical performance, nickel oxide (NiO) was incorporated into C-CA, resulting in C-CA@NiO with pseudocapacitance. The specific surface area of CA increased with carbonization and the subsequent incorporation of NiO. The as-synthesized C-CA and C-CA@NiO materials were applied to an Al-coated current collector to obtain C-CA- and C-CA@NiO-based electrodes, exhibiting stable electrochemical behavior in the voltage range of -1.0 to 0 V and 0 to 1.0 V, respectively. An asymmetric supercapacitor (ASC) device was assembled with C-CA@NiO and C-CA as the positive and negative electrodes, respectively. This ASC device demonstrated a high specific capacitance of 40.8 F g-1, while widening the operating voltage window to 2.0 V. The high electrochemical performance of the device is attributed to the successful Al electrodeposition, which facilitates the electrical conductivity and increased porosity of the C-CA@NiO and C-CA materials. To the best of our knowledge, this is a pioneering study in regards to the conversion of biomass waste into current collectors and active materials to fabricate a practical ASC device. Our findings highlight the potential of reusing Al paper and CA filters from heated tobacco waste as essential components of energy storage devices.

Supramolecular design strategy of cyclodextrin polymer-polyaniline/hollow carbon spheres with core-shell nanostructures for supercapacitor

Controllable polymerization is of great significance for the design of nanoscale devices with high electrochemical performances. In this study, cyclodextrin polymer (CDP)-functionalized polyaniline (PANI)/hollow carbon sphere (HCS) composites were prepared by an in-situ polymerization strategy. HCSs were used as carbon structural templates. CDP can be decorated with a controllable PANI layer owing to supramolecular interactions, effectively preventing the problem of secondary growth of PANI during the polymerization of aniline. Consequently, the integration promotes the more consistent growth of PANI on HCS and further ameliorates the capacitance performance of CDP-PANI/HCS. In a three-electrode system, the specific capacitance of PANI/HCS at 1 A g−1 was 390 F g−1, which can be increased to 569 F g−1 after CDP-induced polymerization. CDP-PANI/HCS shows a high energy density of 24.5 Wh∙kg−1 at a power density of 700 W kg−1, and the energy density still retains 15.5 Wh∙kg−1 even at a higher power density of 14000 W kg−1. Thus, the strategy established in this work has great potential for improving the growth of polymers via CDP-assisted polymerization.

Laser-induced reduction and pattern regulation of graphene oxide film with high biosafety for wearable micro-supercapacitors

A two-step laser process consisting of surface treatment and pattern scribing was developed to prepare micro-supercapacitors (MSCs) with high electrochemical performance and structural robustness. First, an ultrathin and uniform graphene oxide (GO) film was deposited onto a copper foil by electrophoretic deposition, after which a laser beam with a wavelength of 450 nm was used to remove the oxygen-containing functional groups and introduce porous structures into the GO film. Subsequently, another laser beam with a wavelength of 1064 nm was used to scribe the film to form finger-patterned electrodes. After being assembled into flexible MSCs, the volume specific capacity of the MSCs reached 1.94 F cm−3, and the power and energy densities reached 4 mW cm−3 and 0.172 mWh cm−3, respectively. After 7000 charge-discharge cycles, the device showed excellent cycling stability with a capacitance retention rate of ∼87.5%. Moreover, the MSCs could be bent into different forms with marginal capacitance loss, confirming their high structural tolerance. Remarkably, the laser-irradiated GO (L-GO) film showed high biosafety toward human empirical cells in the biotoxicity tests, indicating that the devices could be adopted as reliable micro-devices with high biosafety for fabricating wearable electronics on human skin.

Preparation of V2O5 nanobelt arrays/NiO nanosheet arrays composite as supercapacitor electrode material

V2O5 nanobelt arrays (VNBAs) is fabricated on Ni foam by using an easy hydrothermal route and then NiO nanosheet arrays (NNSAs) is grown on VNBAs by using a simple chemical bath deposition approach to form VNBAs/NNSAs composite. It is found that the monocrystalline VNBAs with a lamellar structure is uniformly distributed on nickel foam and the polystalline NNSAs with a close packed structure is closely covered on the VNBAs. CV, GCD, EIS and CA electrochemical techniques are used to test the supercapacitive properties of the VNBAs/NNSAs composite. The single electrode displays a high specific capacity of 875 F g−1, a good cycling stability of 96.1%, a small charge transfer resistance of 1.32 Ω and a rapid ion diffusivity of 2.5 × 10−8 cm2 s−1. The symmetric supercapacitor combined by the VNBAs/NNSAs displays a large energy density of 120.1 W h kg−1 at 400 W kg−1 and it retains 68.3 W h kg−1 at 8000 W kg−1. The VNBAs/NNSAs composite with high electrochemical performance is a potential supercapacitor electrode material.

Well-integrated bismuth trioxide nanotriangles on carbon cloth as a flexible faradic electrode for supercapacitor applications

The development of redox-active and binder-free materials using facile synthesis methods has attracted great attention in the fabrication of high-performance energy storage devices. In this work, we have used a simple electrochemical deposition method for the direct growth of bismuth trioxide nanostructures on carbon cloth (Bi2O3/CC) for electrochemical supercapacitors (SCs). The as-synthesized Bi2O3 electrode appeared to be triangle-shaped nanostructures with robust adhesion and good crystallinity on a flexible CC electrode. The binder-free Bi2O3/CC electrode has been directly used as an SC electrode, which demonstrated battery-type redox behavior with high electrochemical performance. The low charge transfer resistance (3.9 Ω) of the binder-free Bi2O3/CC electrode demonstrated a specific capacity of 105.5C/g at a current density of 1 A/g with good rate capability at 12 A/g. Moreover, Bi2O3/CC showed good cycling stability of 70.6 % after 2000 consecutive charge-discharge cycles. Considering the simple and direct growth of anode materials, this work could unlock the enormous potential for the development of negative electrode material in hybrid SCs with excellent energy storage properties.

An imidazole-philic dispersible ionic liquid provides ample proton transport channels and high proton performances for high temperature proton exchange membranes

Abundant proton transport channels in polybenzimidazole proton exchange membranes (PBI-PEMs) has been considered as the guarantee of high electrochemical performances for high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Porous structures are widely employed to create the channels. However, low mechanical properties of membranes results from chaotic aggregated pores hinders the application. In this study, the membrane of continuous micro-porous structure was innovatively fabricated via self-assembly of 1-Allyl-3-methylimidazolium chloride ([AmIm]Cl) in PBIs. The ionic liquid (IL) form continuous phases among PBI chains with inter-molecular distances less than 5 Å. The uniform porous structure enables tighter segment packing of polymer, creating uninterrupted PA channels that significantly enhanced proton transport efficiency without undermining the mechanical properties. The resulting micro-porous membrane displayed exceptional power density of 717.7 mW cm−2 at 160 °C, with 0.6 mg cm−2 Pt loading, accompanied by remarkable tensile strength of 12.4 MPa. Moreover, the catalyst layer exhibited superior oxygen diffusivity by optimizing the PA uptake. These results indicate that the micro-porous structure driven by the imidazole-philic dispersible ionic liquid is an effective strategy for designing high-performance PEMs.

Enhanced water retention in carbon nanotube sheets-sandwiched gas diffusion layer in polymer electrolyte membrane fuel cells operated under low humidity conditions

This study introduces the polymer electrolyte membrane fuel cell (PEMFC) using sandwiched-carbon nanotube (CNT) sheets into the gas diffusion layer (GDL). The CNT sheegts are synthesized via floating catalyst chemical vapor deposition and formed into sheets using the direct spinning technique. The sandwiched-CNT sheets PEMFC indicates high electrochemical performance across a range of relative humidity conditions, remarkably in non-humidified conditions of the cathode. This notable achievement can be attributed to the distinctive physical properties of the CNT sheets. In contrast to the microporous layers, the CNT sheets possess a nanoporous structure that enhances reactant diffusion, and appropriate hydrophobicity enhances the water retention capacity in GDL. These properties are confirmed by polarization curves, electrochemical impedance spectroscopy (EIS), quantitative capillary pressure, and water removal rate test in constant current mode at 0.4 A/cm2. In the non-humidified cathode condition, the peak power density of the sandwiched-CNT sheets PEMFC is 45% higher than conventional PEMFC. Moreover, it demonstrates significantly reduced ohmic resistance in EIS. The water retention capability of the PEMFC is assessed through quantitative capillary pressure and water removal rate test. Based on these assessments, we validate that the sandwiched-CNT sheets PEMFC exhibits high performance even under non-humidified cathode conditions.

Nanowire sulfide/carbon composite with high electrochemical performance in potassium-ion batteries

Transition metal chalcogenides (TMCs) have demonstrated great potential in energy storage devices due to their versatile structures and composite functionalities. However, the application of TMCs in potassium-ion batteries (PIBs) suffers from the issues of large volume expansion, polysulfide dissolution, and sluggish kinetics. To overcome these challenges, this work develops nano-flower-like MnS-Co3S4 confined in poly-pyrrole (PPY) carbon nanotube (denoted as MS-CS-PPY) as an excellent anode in PIBs. The nitrogen-doped PPY framework facilitates the interface electron transfer, confines active materials MS-CS effectively, and mitigates the volume change, thus resulting in boosted reaction kinetics and exceptional cycling stability. TMCs induce the surface capacitance and enable the chemical anchoring of the charge/discharge products during the potassium/de-potassium process. Moreover, this work reveals the potassium/de-potassium reaction mechanism, redox kinetics, and solid electrolyte interphase formation of MS-CS-PPY in different electrolytes through theoretical calculations and experimental studies. The solvation ability of electrolytes plays a vital role in manipulating the redox kinetics of the MS-CS-PPY anode material. This study offers feasible strategies for electrode design and electrolyte selection for developing TMCs negative electrodes in future PIBs.

Electrical bridging effects of dual-carbon microsphere frameworks in Si-based composite anodes for high-performance Li-ion batteries

Herein, the successful fabrication of a high-performance Si-based composite Li-ion battery (LIB) anode, comprising a dual-carbon framework of reduced graphene oxide (r-GO) and oxidized single-walled carbon nanohorns (o-NHs), was demonstrated using a simple and scalable spray-drying process followed by heat treatment (h-s-GO/Si/NH). The r-GO nanosheets in the h-s-GO/Si/NH anode acted as a robust spherical framework that facilitated the mechanical and electrical connection between the carbon-coated Si (c-Si) nanoparticles, homogeneous dispersion of c-Si and o-NH nanoparticles, and suppression of the volume expansion and pulverization that occur during lithiation/delithiation. Additionally, the o-NH nanoparticles incorporated in the h-s-GO/Si/NH composite served as electrical bridges between the r-GO nanosheets, resulting in enhanced electrical conductivity and effortless Li-ion shuttling. The h-s-GO/Si/NH composite anode exhibited high electrochemical performance with a very high initial gravimetric charge capacity (2961 mAh g−1 at 0.1 A g−1), stable initial Coulombic efficiency (80.6% at 0.2 A g−1), and high cycling stability (983 mAh g−1 at 0.2 A g−1 after 50 cycles). This study highlights the importance of the effective design of electrically conductive three-dimensional frameworks in Si-based composite anodes, which may contribute to the development of high-performance LIB anode materials.

3D heterostructure constructed by few-layer 1T MoS2 and MXene under high electrostatic fields for high-performance supercapacitors

Electrostatic spray deposition (ESD) is a promising technique for preparing high-quality heterostructure materials to achieve high electrochemical performance. Moreover, the materials obtained by ESD possesses well-dispersed, bonder-free and easy-control advantages. Herein, we firstly report that 1T MoS2/Ti3C2Tx heterostructure material is successfully constructed by few-layer 1T MoS2 and Ti3C2Tx MXene through ESD. The construction of heterostructure by high electrostatic fields is able to solve problem of agglomeration of layered materials, improve conductivity and stabilize 1T MoS2 to realize outstanding electrochemical performance of supercapacitor. As expected, the binder-free 1T MoS2/Ti3C2Tx heterostructure displays an excellent specific capacitance (1198 mF cm−2 at 3 mA cm−2), a high rate performance (45% as current density from 3 to 20 mA cm−2) and long-cycle life (73.8% capacity retention after 7000 cycles at 20 mA cm−2). More interestingly, a simple and efficient route to prepare 2D/2D heterostructure electrode for storing energy can be extended to other materials.