Rate capability,peak power,and energy density are of vital importance for the capacitive energy storage(CES)of electrochemical energy devices.The frequency response analysis(FRA)is regarded as an efficient tool in stu...Rate capability,peak power,and energy density are of vital importance for the capacitive energy storage(CES)of electrochemical energy devices.The frequency response analysis(FRA)is regarded as an efficient tool in studying the CES.In the present work,a bi-scale impedance transmission line model(TLM)is firstly developed for a single pore to a porous electrode.Not only the TLM of the single pore is reparameterized but also the particle packing compactness is defined in the bi-scale.Subsequently,the CES properties are identified by FRA,focused on rate capability vs.characteristic frequency,peak power vs.equivalent series resistance,and energy density vs.low frequency limiting capacitance for a single pore to a porous electrode.Based on these relationships,the CES properties are numerically simulated and theoretically predicted for a single pore to a porous electrode in terms of intra-particle pore length,intra-particle pore diameter,inter-particle pore diameter,electrolyte conductivity,interfacial capacitance&exponent factor,electrode thickness,electrode apparent surface area,and particle packing compactness.Finally,the experimental diagnosis of four supercapacitors(SCs)with different electrode thicknesses is conducted for validating the bi-scale TLM and gaining an insight into the CES properties for a porous electrode to a single pore.The calculating results suggest,to some extent,the inter-particle pore plays a more critical role than the intra-particle pore in the CES properties such as the rate capability and the peak power density for a single pore to a porous electrode.Hence,in order to design a better porous electrode,more attention should be given to the inter-particle pore.展开更多
A new model of porous electrodes based on the Gibbs free energy is developed, in which lithium-ion(Liion) diffusion, diffusion-induced stress(DIS), Butler–Volmer(BV) reaction kinetics, and size polydispersity of elec...A new model of porous electrodes based on the Gibbs free energy is developed, in which lithium-ion(Liion) diffusion, diffusion-induced stress(DIS), Butler–Volmer(BV) reaction kinetics, and size polydispersity of electrode particles are considered. The influence of BV reaction kinetics and concentration-dependent exchange current density(ECD) on concentration profile and DIS evolution are numerically investigated. BV reaction kinetics leads to a decrease in Li-ion concentration and DIS. In addition, concentrationdependent ECD results in a decrease in Li-ion concentration and an increase in DIS. Size polydispersity of electrode particles significantly affects the concentration profile and DIS.Optimal macroscopic state of charge(SOC) should consider the influence of the microscopic SOC values and mass fractions of differently sized particles.展开更多
Understanding the mechanisms and properties of various transport processes in the electrolyte,porous electrode,and at the interface between electrode and electrolyte plays a crucial role in guiding the improvement of ...Understanding the mechanisms and properties of various transport processes in the electrolyte,porous electrode,and at the interface between electrode and electrolyte plays a crucial role in guiding the improvement of electrolytes,materials and microstructures of electrode.Nanoscale equilibrium properties and nonequilibrium ion transport are substantially different to that in the bulk,which are difficult to observe from experiments directly.In this paper,we introduce equilibrium and no-equilibrium thermodynamics for electrolyte in porous electrodes or electrolyte-electrode interface.The equilibrium properties of electrical double layer(EDL)including the EDL structure and capacitance are discussed.In addition,classical non-equilibrium thermodynamic theory is introduced to help us understand the coupling effect of different transport processes.We also review the recent studies of nonequilibrium ion transport in porous electrode by molecular and continuum methods,among these methods,dynamic density functional theory(DDFT)shows tremendous potential as its high efficiency and high accuracy.Moreover,some opportunities for future development and application of the non-equilibrium thermodynamics in electrochemical system are prospected.展开更多
The polyaniline/polysulfone(PAN/PSF) composite films were prepared by electropolymerization,and then CeO2-Pt particles were codeposited into this composite film to obtain the CeO2-Pt-modified polyaniline/polysulfone...The polyaniline/polysulfone(PAN/PSF) composite films were prepared by electropolymerization,and then CeO2-Pt particles were codeposited into this composite film to obtain the CeO2-Pt-modified polyaniline/polysulfone(CeO2-Pt/PAN/PSF) electrodes.Their morphol-ogy and chemical component were characterized by field emission scanning electron microscopy(FESEM) and energy dispersive X-ray spectroscopy(EDS),respectively.The results showed that the composite film had bi-layer structure with asymmetrical pores,and platinum and cerium oxide particles were homogeneously dispersed in the modified film electrodes.The cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) techniques were applied to investigate the electrocatalytic activity of the Pt-CeO2/PAN/PSF electrodes.It was indicated that appropriate amount of CeO2 could enhance the catalytic activity of Pt for methanol electro-oxidation.Chronoamperometry(i-t) measurements revealed that the Pt-CeO2/PAN/PSF electrode was relatively endurable for intermediate production.In addition,different mix-ing amounts of Pt and CeO2 nanoparticles were also investigated in detail.展开更多
Porous platinum electrodes were prepared by adding YSZ,as an active material,in platinum paste.Relationship between microstructure and electrochemical performance of O 2(g),Pt/YSZ electrode have been characterized by ...Porous platinum electrodes were prepared by adding YSZ,as an active material,in platinum paste.Relationship between microstructure and electrochemical performance of O 2(g),Pt/YSZ electrode have been characterized by SEM and cyclic voltammetry.Results showed that the microstructure of platinum electrode is a significant impact on the cyclic voltammetry.With the increase of platinum electrode's porosity,the area of three-phase boundary of O 2(g) /Pt/YSZ was increased.The electrochemical reactivity was also enhanced.These were presented as the increase of current density and cathode voltage in cyclic voltammetry.展开更多
In the development of Li-ion batteries(LIBs)with high energy/power density,long cycle-life,fast charging,and high safety,an insight into charge transfer reactions is required.Although electrochemical impedance spectro...In the development of Li-ion batteries(LIBs)with high energy/power density,long cycle-life,fast charging,and high safety,an insight into charge transfer reactions is required.Although electrochemical impedance spectroscopy(EIS)is regarded as a powerful diagnosis tool,it is not a direct but an indirect measurement.With respect to this,some critical questions need to be answered:(i)why EIS can reflect the kinetics of charge transfer reactions;(ii)what the inherent logical relationship between impedance models under different physical scenes is;(iii)how charge transfer reactions compete with each other at multiple scales.This work aims at answering these questions via developing a theory framework so as to mitigate the blindness and uncertainty in unveiling charge transfer reactions in LIBs.To systematically answer the above questions,this article is organized into a three-in-one(review,tutorial,and research)type and the following contributions are made:(i)a brief review is given for impedance model development of the LIBs over the past half century;(ii)an open source code toolbox is developed based on the unified impedance model;(iii)the competive mechanisms of charge transfer reactions are unveiled based on the developed EIS-Toolbox@LIB.This work not only clarifies theoretical fundamentals,but also provides an easy-to-use open source code for EIS-Toolbox@LIB to optimize fast charge/discharge,mitigate cycle aging,and improve energy/power density.展开更多
Graphite material was used as the electrode for an all-vanadium redox flow battery, and the electrode was modified by transition metallic ions to enhance its electrochemical behavior. An porous graphite composite elec...Graphite material was used as the electrode for an all-vanadium redox flow battery, and the electrode was modified by transition metallic ions to enhance its electrochemical behavior. An porous graphite composite electrode has high specific surface area and high current density. The electrode modified by transition metallic ions has improved catalysis behavior that can catalyze the V(Ⅱ)-V(Ⅴ) redox reaction showed by cyclic voltammograms. This article studied the impedance of the modified electrode by electrochemical impedance spectroscopy (EIS), and approved that the electrode modified by Co^2+ and Mn^2+ has a lower charge transfer resistance than the non-modified electrode. The effect of average particle size distribution is at lower frequencies that the slope of Warburg impedance is reduced by large particle size distribution. The voltage efficiency of the Co^2+ modified electrode test cell is 81.5%, which is higher than that of the non-modified electrode.展开更多
In this study, the effects of discharge rate and LiMn2O4 cathode properties (thickness, porosity, particle size, and solid-state diffusivity and conductivity) on the gravimetric energy and power density of a lithium...In this study, the effects of discharge rate and LiMn2O4 cathode properties (thickness, porosity, particle size, and solid-state diffusivity and conductivity) on the gravimetric energy and power density of a lithium-ion battery cell are analyzed simultaneously using a cell-level model. Surrogate-based analysis tools are applied to simulation data to construct educed-order models, which are in turn used to perform global sensitivity analysis to compare the relative importance of cathode properties. Based on these results, the cell is then optimized for several distinct physical scenarios using gradient-based methods. The comple-mentary nature of the gradient-and surrogate-based tools is demonstrated by establishing proper bounds and constraints with the surrogate model, and then obtaining accurate optimized solutions with the gradient-based optimizer. These optimal solutions enable the quantification of the tradeoffs between energy and power density, and the effect of optimizing the electrode thickness and porosity. In conjunction with known guidelines, the numerical optimization frame-work developed herein can be applied directly to cell and pack design.展开更多
Engineering failure of membrane electrode assembly caused by increasingly fuel poisoning in the high temperature polymer electrolyte membrane fuel cells fed with humidified reformate gases is firstly demonstrated here...Engineering failure of membrane electrode assembly caused by increasingly fuel poisoning in the high temperature polymer electrolyte membrane fuel cells fed with humidified reformate gases is firstly demonstrated herein this work. Based on the results of the in-situ environmental scanning electron microscope, electrochemical analyses, and limiting current method, a water-induced phosphoric acid invasion model is constructed in the porous electrode to elucidate the failure causations of the hindered hydrogen mass transport and the enhanced carbon monoxide poisoning. To optimize the phosphoric acid distribution under the inevitably humidified circumstance, a facile and effective strategy of constructing acid-proofed electrode is proposed and demonstrates outstanding stability with highly humidified reformate gases as anode fuel. This work discusses a potential defect that was rarely studied previously under practical working circumstance for high temperature polymer electrolyte membrane fuel cells, providing an alternative opinion of electrode design based on the fundamental aspects towards the engineering problems.展开更多
Anodic oxidation electrodeposition is the primary way to prepare lead dioxide anode. The regulation of the external circuit for the reaction is a unique advantage of electrocatalytic reaction, which can regulate cryst...Anodic oxidation electrodeposition is the primary way to prepare lead dioxide anode. The regulation of the external circuit for the reaction is a unique advantage of electrocatalytic reaction, which can regulate crystallization and accelerate the reaction process. In this study, lead dioxide coatings with uniform pore size distribution were quickly prepared on three different substrates by potential linear increase electrodeposition(PLIED). Morphology and structure analysis shows that the prepared electrodes have uniform porous morphology, and Ti/SnO_(2)/PLIED has the smallest grain size. Three electrodes all display well degradation performance to azophloxine and diclofenac sodium. Ti/PLIED, and Ti/SnO_(2)/PLIED are appreciated for degrading organics with a simple structure in low concentrations. At the same time,Ti/SnO_(2)/PLIED is more suitable for complex organics in high concentrations. Electrochemical activity tests indicate the different mechanisms of the PLIED electrodes that build the other degradation performance.Three PLIED electrodes show excellent electrical and electrochemical stability during the cycle degradation process. The results provide a reference for the subsequent anodic oxidation electrodeposition research and the regulating effect of the external circuit on coating properties.展开更多
Computational modeling methods,including molecular dynamics(MD)and Monte Carlo(MC)simulations,and density functional theory(DFT),are receiving booming interests for exploring charge storage mechanisms of electrochemic...Computational modeling methods,including molecular dynamics(MD)and Monte Carlo(MC)simulations,and density functional theory(DFT),are receiving booming interests for exploring charge storage mechanisms of electrochemical energy storage devices.These methods can effectively be used to obtain molecular scale local information or provide clear explanations for novel experimental findings that cannot be directly interpreted through experimental investigations.This short review is dedicated to emphasizing recent advances in computational simulation methods for exploring the charge storage mechanisms in typical nanoscale materials,such as nanoporous carbon materials,2 D MXene materials,and metal-organic framework electrodes.Beyond a better understanding of charge storage mechanisms and experimental observations,fast and accurate enough models would be helpful to provide theoretical guidance and experimental basis for the design of new high-performance electrochemical energy storage devices.展开更多
Three-dimensional(3D)grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions(Li-ions),thereby reducing the total transport distance of Li-ions and improving the...Three-dimensional(3D)grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions(Li-ions),thereby reducing the total transport distance of Li-ions and improving the reaction kinetics.Although there have been other studies focusing on 3D electrodes fabricated by 3D printing,there still exists a gap between electrode design and their electrochemical performance.In this study,we try to bridge this gap through a comprehensive investigation on the effects of various electrode parameters including the electrode porosity,active material particle diameter,electrode electronic conductivity,electrode thickness,line width,and pore size on the electrochemical performance.Both numerical simulations and experimental investigations are conducted to systematically examine these effects.3D grid porous Li_(4)Ti_(5)O_(12)(LTO)thick electrodes are fabricated by low temperature direct writing technology and the electrodes with the thickness of 1085μm and areal mass loading of 39.44 mg·cm^(−2) are obtained.The electrodes display impressive electrochemical performance with the areal capacity of 5.88 mAh·cm^(−2)@1.0 C,areal energy density of 28.95 J·cm^(−2)@1.0 C,and areal power density of 8.04 mW·cm^(−2)@1.0 C.This study can provide design guidelines for obtaining 3D grid porous electrodes with superior electrochemical performance.展开更多
The development of a simple, efficient and sensitive sensor for dissolved oxygen is proposed using a novel type of porous carbon composite membrane/glassy carbon electrode based on the low-cost common filter paper by ...The development of a simple, efficient and sensitive sensor for dissolved oxygen is proposed using a novel type of porous carbon composite membrane/glassy carbon electrode based on the low-cost common filter paper by a simple method. The resulting device exhibited excellent electrocatalytic activities toward the oxygen reduction reaction. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements demonstrated that the porous morphology and uniformly dispersed Fe;C nanoparticles of the PCCM play an important role in the oxygen reduction reaction. A linear response range from 2mmol/L up to 110 mmol/L and a detection limit of 1.4 mmol/L was obtained with this sensor. The repeatability of the proposed sensor,evaluated in terms of relative standard deviation, was 3.0%. The successful fabrication of PCCM/GC electrode may promote the development of new porous carbon oxygen reduction reaction material for the oxygen reduction sensor.展开更多
Sulphur(S)-template method based on conventional slurry-casting method has been developed to pro-duce porous silicon(Si)electrodes.The facile fabrication technology is suitable for current production line and expected...Sulphur(S)-template method based on conventional slurry-casting method has been developed to pro-duce porous silicon(Si)electrodes.The facile fabrication technology is suitable for current production line and expected to be widely applied to various electrode materials under large volume change during operation.Specifically,S particles as template agent are mixed with active material Si,carbon conductor and binder forming uniform slurry.After casting and drying,the electrodes are immersed in carbon disul-fide solution to remove S particles rapidly,generating pores in-situ at the original position of S particles.Electrochemical analysis shows that the pores inside electrodes are able to shorten lithium ion diffusion paths,reduce normal expansion rate and decrease formation of cracks in the Si electrode(2 mg_(Si)/cm^(2)),demonstrating a reversible capacity of 951 mAh/g at 0.5 A/g after 100 cycles(with a capacity retention of 99.5%)and a capacity of-826 mAh/g at 2 A/g.展开更多
Description of electrolyte fluid dynamics in the electrode compartments by mathematical models can be a powerful tool in the development of redox flow batteries(RFBs)and other electrochemical reactors.In order to dete...Description of electrolyte fluid dynamics in the electrode compartments by mathematical models can be a powerful tool in the development of redox flow batteries(RFBs)and other electrochemical reactors.In order to determine their predictive capability,turbulent Reynolds-averaged Navier-Stokes(RANS)and free flow plus porous media(Brinkman)models were applied to compute local fluid velocities taking place in a rectangular channel electrochemical flow cell used as the positive half-cell of a cerium-based RFB for laboratory studies.Two different platinized titanium electrodes were considered,a plate plus a turbulence promoter and an expanded metal mesh.Calculated pressure drop was validated against experimental data obtained with typical cerium electrolytes.It was found that the pressure drop values were better described by the RANS approach,whereas the validity of Brinkman equations was strongly dependent on porosity and permeability values of the porous media.展开更多
The bio-nanotechnological fabrication of high-surface-area carbons has attracted widespread interest in supercapacitor applications by using readily-available natural products as raw materials or bio-templates,and is ...The bio-nanotechnological fabrication of high-surface-area carbons has attracted widespread interest in supercapacitor applications by using readily-available natural products as raw materials or bio-templates,and is expected to refine on pore accessibility for compact energy storage. Here, a renovated design strategy of semi-biomass interpenetrating polymer network(IPN) derived carbon is demonstrated through physically knitting the biomacromolecule(sodium alginate, SA) polymeric chains into the highly crosslinked resorcinol-formaldehyde(RF) network and subsequent thermochemical conversion. Moleculelevel interlacing forces in such IPN efficiently relieve the RF skeleton shrinkage when producing carbon,while the other SA network addresses the macrophase separation issue to sacrifice as an in-knitted porogen and a morphology-directing agent. As a result, porous carbon globules are equipped with moss-like surfaces and interconnected pore architecture for high accessible electrode surface(1013 m^(2)/g), and efficient electrochemical responses are reached with the specific capacitance of 312 F/g at 1 A/g. Taking the advantage of 9 mol/kg NaClO_(4) complex-solvent electrolyte, the voltage window is extended to 2.4 V,endowing the two-electrode device with the high energy delivery of 32.3 Wh/kg at 240 W/kg.展开更多
Two‑dimensional MXenes with an enormous active surface area are considered to be significant cathode materials for Zn‑ion hybrid supercapacitors. However, the nanosheets are easily self-restacked during the assembly i...Two‑dimensional MXenes with an enormous active surface area are considered to be significant cathode materials for Zn‑ion hybrid supercapacitors. However, the nanosheets are easily self-restacked during the assembly into macroscopic porous electrodes, resulting in a significantly reduced effective surface area, hindering their applications in energy storage. Here, MXenes are subtly distributed on the surface of the sponge in a coral-like structure rather than participating in the assembly of the framework, which has suppressed the self-restacking of MXene effectively, improved the hydrophilicity of the sponge, and provided fast diffusion channels for electrolyte ions. Therefore, the MXene-TiC-reduced graphene oxide sponge exhibits excellent electrical conductivity, an enormous specific surface area with abundant accessible electroactive sites, and superior electrochemical performance. The resulting sponge demonstrates an outstanding specific capacity, up to 501 mAh g–1 at 0.2 A g–1 , with excellent capacity retention (90%) after 3100 cycles as Zinc-ion hybrid supercapacitor cathodes. Furthermore, it exhibits an elegant gravimetric energy density of 486 mWh g–1 at 415 mW g–1 , which has surpassed most leading MXene-based Zn-ion cathodes. This work provides a new synthetic idea for MXene-based macro-composites and paves a new avenue for designing next-generation flexible and portable porous electrodes with high gravimetric and rate performances.展开更多
High-performance solid polymer electrolyte (SPE) has long been desired for the next-generation high energy density and safe rechargeable lithium batteries. A SPE composed of 80 wt% lithium bis(trifluo-romethanesulf...High-performance solid polymer electrolyte (SPE) has long been desired for the next-generation high energy density and safe rechargeable lithium batteries. A SPE composed of 80 wt% lithium bis(trifluo-romethanesulfonyl)imide (LiTFSI), 20% poly(ethylene carbonate) (PEC) and a polyamide (PA) fiber membrane backbone was prepared by solution-casting method. This solid electrolyte exhibits quite high ionic conductivity and lithium ion transference number (t+), and excellent mechanical strength. The as-prepared solid electrolyte shows good wettability to porous electrodes during cycles, which is beneficial to form ionically conductive phase throughout porous electrodes. All-solid-state LiFePO4lLi cells assembled with the as-prepared solid electrolyte deliver a high initial discharge specific capacity of 125.7 mAh·g^-1 and good cycling stability at 55 ℃ (93.4% retention at 1C after 200 cycles), and superior cycle performance. Outstanding electrochemical performance can be mainly ascribed to the improved ionic conductivity in the entire porous electrodes due to the good wettability of SPE.展开更多
A comprehensive model considering all forms of polarization was developed. The model considers the intricate interdependency among the electrode microstructure, the transport phenomena, and the electrochemical process...A comprehensive model considering all forms of polarization was developed. The model considers the intricate interdependency among the electrode microstructure, the transport phenomena, and the electrochemical processes. The active three-phase boundary surface was expressed as a function of electrode microstructure parameters (porosity, coordination number, contact angle, etc.). The exchange current densities used in the simulation were obtained by fitting a general formulation to the polarization curves proposed as a function of cell temperature and oxygen partial pressure. A validation study shows good agreement with published experimental data. Distributions of overpotentials, gas component partial pressures, and electronic/ionic current densities have been calculated. The effects of a porous electrode structure and of vadous operation conditions on cell performance were also predicted. The mechanistic model proposed can be used to interpret experimental observations and optimize cell performance by incorporating reliable experimental data.展开更多
In this paper,floc sludge was transformed into porous carbon matrix composites by acidification and KOH activation at high temperature and used as an electrode material for application in capacitors.The effects of dif...In this paper,floc sludge was transformed into porous carbon matrix composites by acidification and KOH activation at high temperature and used as an electrode material for application in capacitors.The effects of different treatment processes on the electrochemical properties of sludge materials were compared.The results of electrochemical tests showed that the sludge electrode exhibited excellent energy storage performance after HNO3 acidification and KOH activation with a mass ratio of 3:1(KOH/C).The specific capacitance of the sludge electrode reached 287 F/g at a current density of 1 A/g.In addition,the sludge electrode material showed excellent cycle stability(specific capacity retained at 93.4%after 5000 cycles at 5 A/g).Based on XRD,FTIR,SEM,TEM,and BET surface analysis,the morphology of sludge electrode materials can be effectively regulated by chemical pretreatment.The best-performing material showed a 3D porous morphology with a large specific surface area(2588 m^(2)/g)and optimal pore size distribution,improving ion channels and charge conductivity.According to the life cycle assessment of floc sludge utilization,it reduced the resource consumption and toxicity risk by more than 90%compared with ordinary sludge disposal processes.This work provided a cost-effective and eco-friendly sludge reuse method and demonstrated the application potential of sludge-based materials in high-performance supercapacitors.展开更多
基金financial support from the National Science Foundation of China(22078190)the National Key R&D Plan of China(2020YFB1505802)。
文摘Rate capability,peak power,and energy density are of vital importance for the capacitive energy storage(CES)of electrochemical energy devices.The frequency response analysis(FRA)is regarded as an efficient tool in studying the CES.In the present work,a bi-scale impedance transmission line model(TLM)is firstly developed for a single pore to a porous electrode.Not only the TLM of the single pore is reparameterized but also the particle packing compactness is defined in the bi-scale.Subsequently,the CES properties are identified by FRA,focused on rate capability vs.characteristic frequency,peak power vs.equivalent series resistance,and energy density vs.low frequency limiting capacitance for a single pore to a porous electrode.Based on these relationships,the CES properties are numerically simulated and theoretically predicted for a single pore to a porous electrode in terms of intra-particle pore length,intra-particle pore diameter,inter-particle pore diameter,electrolyte conductivity,interfacial capacitance&exponent factor,electrode thickness,electrode apparent surface area,and particle packing compactness.Finally,the experimental diagnosis of four supercapacitors(SCs)with different electrode thicknesses is conducted for validating the bi-scale TLM and gaining an insight into the CES properties for a porous electrode to a single pore.The calculating results suggest,to some extent,the inter-particle pore plays a more critical role than the intra-particle pore in the CES properties such as the rate capability and the peak power density for a single pore to a porous electrode.Hence,in order to design a better porous electrode,more attention should be given to the inter-particle pore.
基金financial support by the National Natural Science Foundation of China (Grants 11472165, 11332005)
文摘A new model of porous electrodes based on the Gibbs free energy is developed, in which lithium-ion(Liion) diffusion, diffusion-induced stress(DIS), Butler–Volmer(BV) reaction kinetics, and size polydispersity of electrode particles are considered. The influence of BV reaction kinetics and concentration-dependent exchange current density(ECD) on concentration profile and DIS evolution are numerically investigated. BV reaction kinetics leads to a decrease in Li-ion concentration and DIS. In addition, concentrationdependent ECD results in a decrease in Li-ion concentration and an increase in DIS. Size polydispersity of electrode particles significantly affects the concentration profile and DIS.Optimal macroscopic state of charge(SOC) should consider the influence of the microscopic SOC values and mass fractions of differently sized particles.
基金sponsored by the National Natural Science Foundation of China(No.91834301,21808055)National Natural Science Foundation of China for Innovative Research Groups(No.)+1 种基金the Shanghai Sailing Program(18YF1405400)EU-FET project NANOPHLOW0(REP-766972-1)。
文摘Understanding the mechanisms and properties of various transport processes in the electrolyte,porous electrode,and at the interface between electrode and electrolyte plays a crucial role in guiding the improvement of electrolytes,materials and microstructures of electrode.Nanoscale equilibrium properties and nonequilibrium ion transport are substantially different to that in the bulk,which are difficult to observe from experiments directly.In this paper,we introduce equilibrium and no-equilibrium thermodynamics for electrolyte in porous electrodes or electrolyte-electrode interface.The equilibrium properties of electrical double layer(EDL)including the EDL structure and capacitance are discussed.In addition,classical non-equilibrium thermodynamic theory is introduced to help us understand the coupling effect of different transport processes.We also review the recent studies of nonequilibrium ion transport in porous electrode by molecular and continuum methods,among these methods,dynamic density functional theory(DDFT)shows tremendous potential as its high efficiency and high accuracy.Moreover,some opportunities for future development and application of the non-equilibrium thermodynamics in electrochemical system are prospected.
基金Project supported by the National Natural Science Foundation of China (20475077)
文摘The polyaniline/polysulfone(PAN/PSF) composite films were prepared by electropolymerization,and then CeO2-Pt particles were codeposited into this composite film to obtain the CeO2-Pt-modified polyaniline/polysulfone(CeO2-Pt/PAN/PSF) electrodes.Their morphol-ogy and chemical component were characterized by field emission scanning electron microscopy(FESEM) and energy dispersive X-ray spectroscopy(EDS),respectively.The results showed that the composite film had bi-layer structure with asymmetrical pores,and platinum and cerium oxide particles were homogeneously dispersed in the modified film electrodes.The cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) techniques were applied to investigate the electrocatalytic activity of the Pt-CeO2/PAN/PSF electrodes.It was indicated that appropriate amount of CeO2 could enhance the catalytic activity of Pt for methanol electro-oxidation.Chronoamperometry(i-t) measurements revealed that the Pt-CeO2/PAN/PSF electrode was relatively endurable for intermediate production.In addition,different mix-ing amounts of Pt and CeO2 nanoparticles were also investigated in detail.
文摘Porous platinum electrodes were prepared by adding YSZ,as an active material,in platinum paste.Relationship between microstructure and electrochemical performance of O 2(g),Pt/YSZ electrode have been characterized by SEM and cyclic voltammetry.Results showed that the microstructure of platinum electrode is a significant impact on the cyclic voltammetry.With the increase of platinum electrode's porosity,the area of three-phase boundary of O 2(g) /Pt/YSZ was increased.The electrochemical reactivity was also enhanced.These were presented as the increase of current density and cathode voltage in cyclic voltammetry.
基金the financial support from the National Science Foundation of China(22078190)the National Key R&D Plan of China(2020YFB1505802)。
文摘In the development of Li-ion batteries(LIBs)with high energy/power density,long cycle-life,fast charging,and high safety,an insight into charge transfer reactions is required.Although electrochemical impedance spectroscopy(EIS)is regarded as a powerful diagnosis tool,it is not a direct but an indirect measurement.With respect to this,some critical questions need to be answered:(i)why EIS can reflect the kinetics of charge transfer reactions;(ii)what the inherent logical relationship between impedance models under different physical scenes is;(iii)how charge transfer reactions compete with each other at multiple scales.This work aims at answering these questions via developing a theory framework so as to mitigate the blindness and uncertainty in unveiling charge transfer reactions in LIBs.To systematically answer the above questions,this article is organized into a three-in-one(review,tutorial,and research)type and the following contributions are made:(i)a brief review is given for impedance model development of the LIBs over the past half century;(ii)an open source code toolbox is developed based on the unified impedance model;(iii)the competive mechanisms of charge transfer reactions are unveiled based on the developed EIS-Toolbox@LIB.This work not only clarifies theoretical fundamentals,but also provides an easy-to-use open source code for EIS-Toolbox@LIB to optimize fast charge/discharge,mitigate cycle aging,and improve energy/power density.
基金This work was financially supported by the National Natural Science Foundation of China (No. 90510001).
文摘Graphite material was used as the electrode for an all-vanadium redox flow battery, and the electrode was modified by transition metallic ions to enhance its electrochemical behavior. An porous graphite composite electrode has high specific surface area and high current density. The electrode modified by transition metallic ions has improved catalysis behavior that can catalyze the V(Ⅱ)-V(Ⅴ) redox reaction showed by cyclic voltammograms. This article studied the impedance of the modified electrode by electrochemical impedance spectroscopy (EIS), and approved that the electrode modified by Co^2+ and Mn^2+ has a lower charge transfer resistance than the non-modified electrode. The effect of average particle size distribution is at lower frequencies that the slope of Warburg impedance is reduced by large particle size distribution. The voltage efficiency of the Co^2+ modified electrode test cell is 81.5%, which is higher than that of the non-modified electrode.
基金supported by the General Motors and University of Michigan Advanced Battery Coalition for Drivetrains (ABCD)
文摘In this study, the effects of discharge rate and LiMn2O4 cathode properties (thickness, porosity, particle size, and solid-state diffusivity and conductivity) on the gravimetric energy and power density of a lithium-ion battery cell are analyzed simultaneously using a cell-level model. Surrogate-based analysis tools are applied to simulation data to construct educed-order models, which are in turn used to perform global sensitivity analysis to compare the relative importance of cathode properties. Based on these results, the cell is then optimized for several distinct physical scenarios using gradient-based methods. The comple-mentary nature of the gradient-and surrogate-based tools is demonstrated by establishing proper bounds and constraints with the surrogate model, and then obtaining accurate optimized solutions with the gradient-based optimizer. These optimal solutions enable the quantification of the tradeoffs between energy and power density, and the effect of optimizing the electrode thickness and porosity. In conjunction with known guidelines, the numerical optimization frame-work developed herein can be applied directly to cell and pack design.
基金financially supported by the National Science Foundation of China, China (22179130, 91834301)the Foundation of the Key Laboratory of Chinese Academy of Sciences (CXJJ21S024)Dalian Institute of Chemical Physics, China (DICPI202023)。
文摘Engineering failure of membrane electrode assembly caused by increasingly fuel poisoning in the high temperature polymer electrolyte membrane fuel cells fed with humidified reformate gases is firstly demonstrated herein this work. Based on the results of the in-situ environmental scanning electron microscope, electrochemical analyses, and limiting current method, a water-induced phosphoric acid invasion model is constructed in the porous electrode to elucidate the failure causations of the hindered hydrogen mass transport and the enhanced carbon monoxide poisoning. To optimize the phosphoric acid distribution under the inevitably humidified circumstance, a facile and effective strategy of constructing acid-proofed electrode is proposed and demonstrates outstanding stability with highly humidified reformate gases as anode fuel. This work discusses a potential defect that was rarely studied previously under practical working circumstance for high temperature polymer electrolyte membrane fuel cells, providing an alternative opinion of electrode design based on the fundamental aspects towards the engineering problems.
基金the financial supports from the National Natural Science Foundation of China (No. 52270078)the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2021JM-012)+1 种基金the Welfare Technology Research Plan of Zhejiang Province (No. LZY21E080003)the Fundamental Research Funds for the Central Universities (No. xjh012020037)。
文摘Anodic oxidation electrodeposition is the primary way to prepare lead dioxide anode. The regulation of the external circuit for the reaction is a unique advantage of electrocatalytic reaction, which can regulate crystallization and accelerate the reaction process. In this study, lead dioxide coatings with uniform pore size distribution were quickly prepared on three different substrates by potential linear increase electrodeposition(PLIED). Morphology and structure analysis shows that the prepared electrodes have uniform porous morphology, and Ti/SnO_(2)/PLIED has the smallest grain size. Three electrodes all display well degradation performance to azophloxine and diclofenac sodium. Ti/PLIED, and Ti/SnO_(2)/PLIED are appreciated for degrading organics with a simple structure in low concentrations. At the same time,Ti/SnO_(2)/PLIED is more suitable for complex organics in high concentrations. Electrochemical activity tests indicate the different mechanisms of the PLIED electrodes that build the other degradation performance.Three PLIED electrodes show excellent electrical and electrochemical stability during the cycle degradation process. The results provide a reference for the subsequent anodic oxidation electrodeposition research and the regulating effect of the external circuit on coating properties.
基金funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(grant agreement no.714581)supported by the Fundamental Research Funds for the Central Universities(No.YJ201886)+1 种基金the National Natural Science Foundation of China(No.501902215)Sichuan Science and Technology Program(No.2020ZDZX0005)
文摘Computational modeling methods,including molecular dynamics(MD)and Monte Carlo(MC)simulations,and density functional theory(DFT),are receiving booming interests for exploring charge storage mechanisms of electrochemical energy storage devices.These methods can effectively be used to obtain molecular scale local information or provide clear explanations for novel experimental findings that cannot be directly interpreted through experimental investigations.This short review is dedicated to emphasizing recent advances in computational simulation methods for exploring the charge storage mechanisms in typical nanoscale materials,such as nanoporous carbon materials,2 D MXene materials,and metal-organic framework electrodes.Beyond a better understanding of charge storage mechanisms and experimental observations,fast and accurate enough models would be helpful to provide theoretical guidance and experimental basis for the design of new high-performance electrochemical energy storage devices.
基金This work is supported by the National Natural Science Foundation of China(Nos.51705334 and 51975384)the Shenzhen Science&Technology Projects(Nos.JCYJ20180305125025855 and JCYJ20200109105618137).
文摘Three-dimensional(3D)grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions(Li-ions),thereby reducing the total transport distance of Li-ions and improving the reaction kinetics.Although there have been other studies focusing on 3D electrodes fabricated by 3D printing,there still exists a gap between electrode design and their electrochemical performance.In this study,we try to bridge this gap through a comprehensive investigation on the effects of various electrode parameters including the electrode porosity,active material particle diameter,electrode electronic conductivity,electrode thickness,line width,and pore size on the electrochemical performance.Both numerical simulations and experimental investigations are conducted to systematically examine these effects.3D grid porous Li_(4)Ti_(5)O_(12)(LTO)thick electrodes are fabricated by low temperature direct writing technology and the electrodes with the thickness of 1085μm and areal mass loading of 39.44 mg·cm^(−2) are obtained.The electrodes display impressive electrochemical performance with the areal capacity of 5.88 mAh·cm^(−2)@1.0 C,areal energy density of 28.95 J·cm^(−2)@1.0 C,and areal power density of 8.04 mW·cm^(−2)@1.0 C.This study can provide design guidelines for obtaining 3D grid porous electrodes with superior electrochemical performance.
基金the National Natural Science Foundation of China (No.21273097)the project from the State Key Laboratory of Electroanalytical Chemistry (No.2013)the Science Foundation of Jilin Province (No.20130204003GX)
文摘The development of a simple, efficient and sensitive sensor for dissolved oxygen is proposed using a novel type of porous carbon composite membrane/glassy carbon electrode based on the low-cost common filter paper by a simple method. The resulting device exhibited excellent electrocatalytic activities toward the oxygen reduction reaction. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements demonstrated that the porous morphology and uniformly dispersed Fe;C nanoparticles of the PCCM play an important role in the oxygen reduction reaction. A linear response range from 2mmol/L up to 110 mmol/L and a detection limit of 1.4 mmol/L was obtained with this sensor. The repeatability of the proposed sensor,evaluated in terms of relative standard deviation, was 3.0%. The successful fabrication of PCCM/GC electrode may promote the development of new porous carbon oxygen reduction reaction material for the oxygen reduction sensor.
基金the National Natural Science Foundation of China(Nos.51904344,52172264)the Natural Science Foundation of Hunan Province of China(Nos.2021JJ10060,2022GK2033).
文摘Sulphur(S)-template method based on conventional slurry-casting method has been developed to pro-duce porous silicon(Si)electrodes.The facile fabrication technology is suitable for current production line and expected to be widely applied to various electrode materials under large volume change during operation.Specifically,S particles as template agent are mixed with active material Si,carbon conductor and binder forming uniform slurry.After casting and drying,the electrodes are immersed in carbon disul-fide solution to remove S particles rapidly,generating pores in-situ at the original position of S particles.Electrochemical analysis shows that the pores inside electrodes are able to shorten lithium ion diffusion paths,reduce normal expansion rate and decrease formation of cracks in the Si electrode(2 mg_(Si)/cm^(2)),demonstrating a reversible capacity of 951 mAh/g at 0.5 A/g after 100 cycles(with a capacity retention of 99.5%)and a capacity of-826 mAh/g at 2 A/g.
基金BMA is grateful to CONACYT for MSc scholarship No.468574 and for funding an academic visit to the University of Southampton.
文摘Description of electrolyte fluid dynamics in the electrode compartments by mathematical models can be a powerful tool in the development of redox flow batteries(RFBs)and other electrochemical reactors.In order to determine their predictive capability,turbulent Reynolds-averaged Navier-Stokes(RANS)and free flow plus porous media(Brinkman)models were applied to compute local fluid velocities taking place in a rectangular channel electrochemical flow cell used as the positive half-cell of a cerium-based RFB for laboratory studies.Two different platinized titanium electrodes were considered,a plate plus a turbulence promoter and an expanded metal mesh.Calculated pressure drop was validated against experimental data obtained with typical cerium electrolytes.It was found that the pressure drop values were better described by the RANS approach,whereas the validity of Brinkman equations was strongly dependent on porosity and permeability values of the porous media.
基金financially supported by the National Natural Science Foundation of China (Nos. 51772216, 21905207, 21875165 and 21703161)the Science and Technology Commission of Shanghai Municipality, China (Nos. 20ZR1460300, 14DZ2261100)+2 种基金Zhejiang Provincial Natural Science Foundation of China (No. LY19B010003)the Fundamental Research Funds for the Central Universitiesthe Large Equipment Test Foundation of Tongji University。
文摘The bio-nanotechnological fabrication of high-surface-area carbons has attracted widespread interest in supercapacitor applications by using readily-available natural products as raw materials or bio-templates,and is expected to refine on pore accessibility for compact energy storage. Here, a renovated design strategy of semi-biomass interpenetrating polymer network(IPN) derived carbon is demonstrated through physically knitting the biomacromolecule(sodium alginate, SA) polymeric chains into the highly crosslinked resorcinol-formaldehyde(RF) network and subsequent thermochemical conversion. Moleculelevel interlacing forces in such IPN efficiently relieve the RF skeleton shrinkage when producing carbon,while the other SA network addresses the macrophase separation issue to sacrifice as an in-knitted porogen and a morphology-directing agent. As a result, porous carbon globules are equipped with moss-like surfaces and interconnected pore architecture for high accessible electrode surface(1013 m^(2)/g), and efficient electrochemical responses are reached with the specific capacitance of 312 F/g at 1 A/g. Taking the advantage of 9 mol/kg NaClO_(4) complex-solvent electrolyte, the voltage window is extended to 2.4 V,endowing the two-electrode device with the high energy delivery of 32.3 Wh/kg at 240 W/kg.
基金Supported by the Fundamental Research Funds for the Central Universities and Heilongjiang Provincial Natural Science Founda-tion of China(Grant No.YQ2020E009).
文摘Two‑dimensional MXenes with an enormous active surface area are considered to be significant cathode materials for Zn‑ion hybrid supercapacitors. However, the nanosheets are easily self-restacked during the assembly into macroscopic porous electrodes, resulting in a significantly reduced effective surface area, hindering their applications in energy storage. Here, MXenes are subtly distributed on the surface of the sponge in a coral-like structure rather than participating in the assembly of the framework, which has suppressed the self-restacking of MXene effectively, improved the hydrophilicity of the sponge, and provided fast diffusion channels for electrolyte ions. Therefore, the MXene-TiC-reduced graphene oxide sponge exhibits excellent electrical conductivity, an enormous specific surface area with abundant accessible electroactive sites, and superior electrochemical performance. The resulting sponge demonstrates an outstanding specific capacity, up to 501 mAh g–1 at 0.2 A g–1 , with excellent capacity retention (90%) after 3100 cycles as Zinc-ion hybrid supercapacitor cathodes. Furthermore, it exhibits an elegant gravimetric energy density of 486 mWh g–1 at 415 mW g–1 , which has surpassed most leading MXene-based Zn-ion cathodes. This work provides a new synthetic idea for MXene-based macro-composites and paves a new avenue for designing next-generation flexible and portable porous electrodes with high gravimetric and rate performances.
基金financially supported by the National Natural Scientific Foundation of China(No.51532002)Beijing Natural Science Foundation(No.L172023)the National Basic Research Program of China(No.2015CB932500)
文摘High-performance solid polymer electrolyte (SPE) has long been desired for the next-generation high energy density and safe rechargeable lithium batteries. A SPE composed of 80 wt% lithium bis(trifluo-romethanesulfonyl)imide (LiTFSI), 20% poly(ethylene carbonate) (PEC) and a polyamide (PA) fiber membrane backbone was prepared by solution-casting method. This solid electrolyte exhibits quite high ionic conductivity and lithium ion transference number (t+), and excellent mechanical strength. The as-prepared solid electrolyte shows good wettability to porous electrodes during cycles, which is beneficial to form ionically conductive phase throughout porous electrodes. All-solid-state LiFePO4lLi cells assembled with the as-prepared solid electrolyte deliver a high initial discharge specific capacity of 125.7 mAh·g^-1 and good cycling stability at 55 ℃ (93.4% retention at 1C after 200 cycles), and superior cycle performance. Outstanding electrochemical performance can be mainly ascribed to the improved ionic conductivity in the entire porous electrodes due to the good wettability of SPE.
文摘A comprehensive model considering all forms of polarization was developed. The model considers the intricate interdependency among the electrode microstructure, the transport phenomena, and the electrochemical processes. The active three-phase boundary surface was expressed as a function of electrode microstructure parameters (porosity, coordination number, contact angle, etc.). The exchange current densities used in the simulation were obtained by fitting a general formulation to the polarization curves proposed as a function of cell temperature and oxygen partial pressure. A validation study shows good agreement with published experimental data. Distributions of overpotentials, gas component partial pressures, and electronic/ionic current densities have been calculated. The effects of a porous electrode structure and of vadous operation conditions on cell performance were also predicted. The mechanistic model proposed can be used to interpret experimental observations and optimize cell performance by incorporating reliable experimental data.
基金funding by National Natural Science Foundation of China(Grant No.51978643)Youth Innovation Promotion Association,CAS(2014037).
文摘In this paper,floc sludge was transformed into porous carbon matrix composites by acidification and KOH activation at high temperature and used as an electrode material for application in capacitors.The effects of different treatment processes on the electrochemical properties of sludge materials were compared.The results of electrochemical tests showed that the sludge electrode exhibited excellent energy storage performance after HNO3 acidification and KOH activation with a mass ratio of 3:1(KOH/C).The specific capacitance of the sludge electrode reached 287 F/g at a current density of 1 A/g.In addition,the sludge electrode material showed excellent cycle stability(specific capacity retained at 93.4%after 5000 cycles at 5 A/g).Based on XRD,FTIR,SEM,TEM,and BET surface analysis,the morphology of sludge electrode materials can be effectively regulated by chemical pretreatment.The best-performing material showed a 3D porous morphology with a large specific surface area(2588 m^(2)/g)and optimal pore size distribution,improving ion channels and charge conductivity.According to the life cycle assessment of floc sludge utilization,it reduced the resource consumption and toxicity risk by more than 90%compared with ordinary sludge disposal processes.This work provided a cost-effective and eco-friendly sludge reuse method and demonstrated the application potential of sludge-based materials in high-performance supercapacitors.