There is an urgent need to break through the trade-off between proton conductivity and ion selectivity of proton exchange membrane(PEM)in vanadium flow battery(VFB).Proton channels in PEM are the key to controlling th...There is an urgent need to break through the trade-off between proton conductivity and ion selectivity of proton exchange membrane(PEM)in vanadium flow battery(VFB).Proton channels in PEM are the key to controlling the ion sieving and proton conductivity in VFB.Herein,two types of proton channels are reconstructed in the hybrid membrane via introducing modified Zr-MOFs(IM-UIO-66-AS)into SPEEK matrix.Internal proton channels in IM-UIO-66-AS and interfacial proton channels between grafted imidazole groups on Zr-MOFs and SPEEK greatly improve the conductivity of the IM-UIO-66-AS/SPEEK hybrid membrane.More importantly,both reconstructed proton channels block the vanadium-ion permeation to realize enhanced ion selectivity according to the size sieving and Donnan exclusion effects,respectively.Moreover,the hybrid membrane exhibits good mechanical property and dimensional stability.Benefiting from such rational design,a VFB loading with the optimized membrane exhibits enhanced voltage efficiency of 79.9%and outstanding energy efficiency of 79.6%at 200 m A cm^(-2),and keeps a notable cycle stability for 300 cycles in the long-term cycling test.Therefore,this study provides inspiration for preparing next-generation PEMs with high ion selectivity and proton conductivity for VFB application.展开更多
For improvement of vanadium redox flow battery （VRB） performance, novel amphoteric semi- interpenetrating membranes （ASIPN） were prepared using poly（ether ether ketone） （PEEK） and polysul- fone （PSf）, the fo...For improvement of vanadium redox flow battery （VRB） performance, novel amphoteric semi- interpenetrating membranes （ASIPN） were prepared using poly（ether ether ketone） （PEEK） and polysul- fone （PSf）, the former bearing sulfonic groups and the latter imidazolium. These two groups form ionic crosslinks between PEEK and PSf; meanwhile, covalent cross links were built between PSf chains with ad- dition of N-（3-aminopropyl）-imidazole. The amphoteric nature of the membrane allows facile proton and anion transport; the IPN structure and the presence of imidazolium cation effectively suppress vanadium ion crossover through the membrane. Therefore, the ASIPN based VRBs show higher Coulombic efficiency and energy efficiency than that assembled with pristine SPEEK and Nation 212 membranes. Our work demonstrates that the ASIPN membranes are promising for VRB applications.展开更多
Vanadium flow batteries(VFBs)have drawn considerable attention as an emerging technology for largescale energy storage systems(ESSs).One of the pivotal challenges is the availability of eligible ion exchange membranes...Vanadium flow batteries(VFBs)have drawn considerable attention as an emerging technology for largescale energy storage systems(ESSs).One of the pivotal challenges is the availability of eligible ion exchange membranes(ICMs)that provide high ion selectivity,proton conductivity,and stability under rigorous condition.Herein,a‘side-chain-type’strategy has been employed to fabricate highly stable phenolphthalein-based cardo poly(arylene ether ketone)s(PAEKs)membrane with low area resistance(0.058Ωcm^(2)),in which flexible alkyl spacers effectively alleviated inductive withdrawing effect from terminal ion exchange groups thus enabling a stable backbone.The assembled VFBs based on PAEKs bearing pendent alkyl chain terminated with quaternary ammonium(Q-PPhEK)demonstrated an energy efficiency above 80%over 700 cycles at 160 mA/cm^(2).Such a remarkable results revealed that the side-chain-type strategy contributed to enhancing the ICMs stability in strong oxidizing environment,meanwhile,more interesting backbones would be woken with this design engaging in stable ICMs for VFBs.展开更多
The scarcity of wettability,insufficient active sites,and low surface area of graphite felt(GF)have long been suppressing the performance of vanadium redox flow batteries(VRFBs).Herein,an ultra-homogeneous multipledim...The scarcity of wettability,insufficient active sites,and low surface area of graphite felt(GF)have long been suppressing the performance of vanadium redox flow batteries(VRFBs).Herein,an ultra-homogeneous multipledimensioned defect,including nano-scale etching and atomic-scale N,O codoping,was used to modify GF by the molten salt system.NH_(4)Cl and KClO_(3) were added simultaneously to the system to obtain porous N/O co-doped electrode(GF/ON),where KClO_(3) was used to ultra-homogeneously etch,and O-functionalize electrode,and NH4Cl was used as N dopant,respectively.GF/ON presents better electrochemical catalysis for VO_(2)+/VO_(2)+ and V3+/V2+ reactions than only O-functionalized electrodes(GF/O)and GF.The enhanced electrochemical properties are attributed to an increase in active sites,surface area,and wettability,as well as the synergistic effect of N and O,which is also supported by the density functional theory calculations.Further,the cell using GF/ON shows higher discharge capacity,energy efficiency,and stability for cycling performance than the pristine cell at 140 mA cm^(−2) for 200 cycles.Moreover,the energy efficiency of the modified cell is increased by 9.7% from 55.2% for the pristine cell at 260 mA cm^(−2).Such an ultra-homogeneous etching with N and O co-doping through“boiling”molten salt medium provides an effective and practical application potential way to prepare superior electrodes for VRFB.展开更多
Vanadium flow battery （VFB） is a fast going and promising system for large-scale stationary energy stor- age. However, drawbacks such as low power density and narrow temperature window caused by poor catalytic activ...Vanadium flow battery （VFB） is a fast going and promising system for large-scale stationary energy stor- age. However, drawbacks such as low power density and narrow temperature window caused by poor catalytic activity of graphite felt （GF） electrodes limit its worldwide application. In this paper, bismuth, as a low-cost, no-toxic and high-activity electrocatalyst, is used to modify the thermal activated GF （TGF） via a facile hydrothermal method. Bismuth can effectively inhibit the side reaction of hydrogen evolution in wide temperature range, while promoting the V2＋/V3＋ redox reaction. As a result, the VFB assembled with Bi/TGF as negative electrode demonstrates outstanding rate performance under the current density up to 400 mAcm-2, as well as a long-term stability over 600 charging/discharging cycles at a high cur- rent density of 150mA cm-2. Moreover, it also shows excellent temperature adaptability from -10 ℃ to 50 ℃ and high durability for life test at the temperature of 50 ℃.展开更多
Vanadium flow battery(VFB)is one of the most promising energy storage technologies because of its superior safety,reliability and cycle life,but the poor electrochemical performance at high cur-rent density limits its...Vanadium flow battery(VFB)is one of the most promising energy storage technologies because of its superior safety,reliability and cycle life,but the poor electrochemical performance at high cur-rent density limits its commercial application.Herein,an advanced design of the dual-gradient carbon nanofibers/graphite felt(DG-CNFs/GF)composite electrode is firstly proposed for the next-generation VFB with high power density.Specifically,there is a macro gradient distribution of CNFs along the thickness direction of the electrode,meanwhile a micro gradient distribution of CNFs is also existed along the ra-dial direction of a single fiber,and both the macro and micro gradient structure are verified through the physicochemical characterizations.In addition,the DG-CNFs/GF with a dual-gradient structure exhibits an excellent electrocatalytic activity and a fast mass transfer characteristic.It is worth noting that the energy conversion efficiencies,cycling stability in addition to power density of VFB with DG-CNFs/GF are much better than those with commercial GF,which make the dual-gradient DG-CNFs/GF to be a promis-ing alternative.Most importantly,the accomplishment of this work will provide a promising development direction of the highly efficient electrode for the next-generation VFB with high power density.展开更多
The vanadium redox flow battery(VRFB)has been receiving great attention in recent years as one of the most viable energy storage technologies for large-scale applications.However,higher concentrations of vanadium spec...The vanadium redox flow battery(VRFB)has been receiving great attention in recent years as one of the most viable energy storage technologies for large-scale applications.However,higher concentrations of vanadium species are required in the H_(2)O-H_(2)SO_(4) electrolyte in order to improve the VRFB energy density.This might lead to unwanted precipitation of vanadium compounds,whose nature has not been accurately characterized yet.For this purpose,this study reports the preparation ofⅤ^((Ⅱ)),ⅤV^((Ⅲ)),Ⅴ^((Ⅳ))andⅤ^((Ⅴ))supersaturated solutions in a 5 M H_(2)SO_(4)-H_(2)O electrolyte by an electrolytic method,from the only vanadium sulfate compound commercially available(VOSO_(4)).The precipitates obtained by ageing of the stirred solutions are representative of the solids that may form in a VRFB operated with such supersaturated solutions.The solid phases are identified using thermogravimetric analysis,X-ray diffraction and SEM.We report that dissolvedⅤ^((Ⅱ)),Ⅴ^((Ⅲ))andⅤ^((Ⅳ))species precipitate as crystals of VSO_(4),V_(2)(SO_(4))3 and VOSO_(4) hydrates and not in their anhydrous form;conversely V^((Ⅴ))precipitates as an amorphous V_(2) O_(5) oxide partially hydrated.The measured hydration degrees(respectively 1.5,9,3 and 0.26 mol of H_(2)O per mol of compound)might significantly affect the overall engineering of VRFB operating with high vanadium concentrations.展开更多
Vanadium redox flow battery(VRFB)is one of the most promising large-scale energy storage systems,which ranges from kilowatt to megawatt.Nevertheless,poor electrochemical activity of electrode for two redox couples sti...Vanadium redox flow battery(VRFB)is one of the most promising large-scale energy storage systems,which ranges from kilowatt to megawatt.Nevertheless,poor electrochemical activity of electrode for two redox couples still restricts the extensive applications of VRFB.Compared with V^(2+)/V^(3+)redox reaction,V^(2+)/V^(3+)reaction plays a more significant role in voltage loss of VRFB owing to slow heterogeneous electron transfer rate.Herein,N-doped carbon materials derived from scaphium scaphigerum have been developed as negative electrocatalyst by hydrothermal carbonization and high-temperature nitridation treatments.The undoped carbon material hardly has electrocatalytic ability for V^(2+)/V^(3+)reaction.Based on this,N-doped carbon materials with urea as nitrogen source exhibit excellent electrocatalytic properties.And the material nitrided at 850°C(SSC/N-850)exhibits the best performance among those from700 to 1000℃.SSC/N-850 can accelerate the electrode process including V^(2+)/V^(3+)reaction and mass transfer of active ions due to the large reaction place,more active sites,and good hydrophilicity.The effect of catalyst on comprehensive performance of cell was evaluated.SSC/N-850 can improve the charge-discharge performance greatly.Utilization of SSC/N-850 can lessen the electrochemical polarization of cell,further resulting in increased discharge capacity and energy efficiency.Discharge capacity and energy efficiency increase by 81.5%and 9.8%by using SSC/N-850 as negative catalyst at 150 m A cm^(-2),respectively.Our study reveals that the developed biomass-derived carbon materials are the low-cost and efficient negative electrocatalyst for VRFB system.展开更多
The parasitic hydrogen evolution reaction(HER)in the negative half-cell of vanadium redox flow batteries(VRFBs)causes severe efficiency losses.Thus,a deeper understanding of this process and the accompanying bubble fo...The parasitic hydrogen evolution reaction(HER)in the negative half-cell of vanadium redox flow batteries(VRFBs)causes severe efficiency losses.Thus,a deeper understanding of this process and the accompanying bubble formation is crucial.This benchmarking study locally analyzes the bubble distribution in thick,porous electrodes for the first time using deep learning-based image segmentation of synchrotron X-ray micro-tomograms.Each large three-dimensional data set was processed precisely in less than one minute while minimizing human errors and pointing out areas of increased HER activity in VRFBs.The study systematically varies the electrode potential and material,concluding that more negative electrode potentials of-200 m V vs.reversible hydrogen electrode(RHE)and lower cause more substantial bubble formation,resulting in bubble fractions of around 15%–20%in carbon felt electrodes.Contrarily,the bubble fractions stay only around 2%in an electrode combining carbon felt and carbon paper.The detected areas with high HER activity,such as the border subregion with more than 30%bubble fraction in carbon felt electrodes,the cutting edges,and preferential spots in the electrode bulk,are potential-independent and suggest that larger electrodes with a higher bulk-to-border ratio might reduce HER-related performance losses.The described combination of electrochemical measurements,local X-ray microtomography,AI-based segmentation,and 3D morphometric analysis is a powerful and novel approach for local bubble analysis in three-dimensional porous electrodes,providing an essential toolkit for a broad community working on bubble-generating electrochemical systems.展开更多
A new amphoteric membrane was prepared by blending long-side-chain sulfonated poly(2,6-dimethyl-1,4-phenylene oxide)(S-L-PPO)and polybenzimidazole(PBI)for vanadium redox flow battery(VRFB)application.An acid-base pair...A new amphoteric membrane was prepared by blending long-side-chain sulfonated poly(2,6-dimethyl-1,4-phenylene oxide)(S-L-PPO)and polybenzimidazole(PBI)for vanadium redox flow battery(VRFB)application.An acid-base pair structure formed between the imidazole of PBI and sulfonic acid of S-L-PPO resulted in lowered swelling ratio.It favors to reduce the vanadium permeation.While,the increased sulfonic acid concentration ensured that proton conductivity was still at a high level.As a result,a better balance between the vanadium ion permeation(6.1×10^-9 cm^2·s^-1)and proton conductivity(50.8 m S·cm^-1)in the S-L-PPO/PBI-10%membrane was achieved.The VRFB performance with S-L-PPO/PBI-10%membrane exhibited an EE of 82.7%,which was higher than those of pristine S-L-PPO(81.8%)and Nafion 212(78.0%)at 120 m A·cm^-2.In addition,the S-LPPO/PBI-10%membrane had a much longer self-discharge duration time(142 h)than that of Nafion 212(23 h).展开更多
In the present paper, multi-walled carbon nanotubes（MWCNTs） are successfully assembled on graphite felt（GF） using sucrose pyrolysis method for the first time. The in situ formed pyrolytic carbon is chosen as the b...In the present paper, multi-walled carbon nanotubes（MWCNTs） are successfully assembled on graphite felt（GF） using sucrose pyrolysis method for the first time. The in situ formed pyrolytic carbon is chosen as the binder because it is essentially carbon materials as well as CNTs and GF which has a natural tendency to achieve high bonding strength and low contact resistance. The MWCNTs/GF electrode is demonstrated to increase surface area, reduce polarization, lower charge transfer resistance and improve energy conversion efficiency comparing with GF. This excellent electrochemical performance is mainly ascribed to the high electro-catalytic activity of MWCNTs and increasing surface area.展开更多
The electrolyte is one of the most important components of vanadium redox flow battery （VRFB）. and its stability and solubility determines the energy density of a VRFB. The performance of current positive elec- trol...The electrolyte is one of the most important components of vanadium redox flow battery （VRFB）. and its stability and solubility determines the energy density of a VRFB. The performance of current positive elec- trolyte is limited by the low stability of VO2＋ at a higher temperature. Phosphate is proved to be a very effective additive to improve the stability of VO2＋. Even though, the stabilizing mechanism is still not clear, which hinders the further development of VRFBs. In this paper, to clarify the effect of phosphate additive on the positive electrolyte stability, the hydration structures of VO2＋ cations and the reaction mechanisms of precipitation with or without phosphate in the supporting electrolyte of H_2SO_4 solutions were investigated in detail based on calculations of electronic structure. The stable configurations of com- plexes were optimized at the B3LYP/6-311 ＋ G（d,p） level of theory. The zero-point energies and Gibbs free energies for these complexes were further evaluated at the B3LYP/aug-cc-pVTZ level of theory. It shows that a structure of [VO_2（H_2O）_2]＋ surrounded by water molecules in H2S04 solution can be formed at the room temperature. With the temperature rises, [VO_2（H_2O）_2]＋ will lose a proton and form the interme- diate of VO（OH）_3, and the further dehydration among VO（OH）_3 molecules will create the precipitate of V_2O_5. When H_3PO_4 was added into electrolytes, the V-O-P bond-containing neutral compound could be formed through interaction between VO（OH）_3 and H_3PO_4, and the activation energy of forming the V-O-P bond-containing neutral compound is about 7 kcal tool-1 lower than that of the VO（OH）_3 dehydration, which could avoid the precipitation of V_2O_5 and improve the electrolyte stability.展开更多
SPES/PVDF blends were employed to prepare the ion exchange membranes for vanadium redox flow battery(VRB) application for the first time. The addition of the highly crystalline and hydrophobic PVDF effectively limited...SPES/PVDF blends were employed to prepare the ion exchange membranes for vanadium redox flow battery(VRB) application for the first time. The addition of the highly crystalline and hydrophobic PVDF effectively limited the swelling behavior of SPES. The vanadium ion permeability of SPES/PVDF membranes was one order of magnitude lower than that of Nafion 117 membrane and pristine SPES membrane. Single cells with SPES/PVDF composite membranes showed significantly lower capacity loss, higher coulombic efficiency and higher energy efficiency than that with Nafion117 and pristine SPES membranes. The blend membrane with 40 wt% of PVDF(denoted as S_(0.6) P_(0.4)) showed energy efficiency of 83.2% at 30 mA?cm^(-2), which was superior to that of the Nafion117 and SPES membranes. In the self-discharge test, S_(0.6) P_(0.4) membrane showed twice longer duration in open circuit decay than that with Nafion 117 membrane. With all the good properties and low cost, the SPES/PVDF membranes are expected to have excellent commercial prospects as ion exchange membranes for VRB system.展开更多
Electrode materials with good redox kinetics,excellent mass transfer characteristics and ultra-high stability play a crucial role in reducing the life-cycle cost and prolonging the maintenance-free time of the vanadiu...Electrode materials with good redox kinetics,excellent mass transfer characteristics and ultra-high stability play a crucial role in reducing the life-cycle cost and prolonging the maintenance-free time of the vanadium flow batteries(VFB).Herein,a nitrogen-doped porous graphite felt electrode(N-PGF)is proposed by growing ZIF-67 nanoparticles on carbon fibers and then calcinating and acid etching.The multi-scale structure of“carbon fiber gap(electrolyte flow),micro/nano pore(active species diffusion)and Nitrogen active center(reaction site)”in N-PGF electrode effectively increases the catalytic sites and promotes mass transfer characteristics.Reasonable electrode design makes the battery show excellent rate performance and ultra-high cycling stability.The peak power density of the battery reaches 1006 mW cm^(-2).During 1000 cycles at 150 mA cm^(-2),the average discharge capacity and average discharge energy of N-PGF increase substantially by 11.6%and 23.4%compared with the benchmark thermal activated graphite felt,respectively.More excitingly,after ultra-long term(5000 cycles)operation at an ultra-high current density(300 mA cm^(-2)),N-PGF exhibits an unprecedented energy efficiency retention(99.79%)and electrochemical performance stability.展开更多
The effect of bismuth (Bi) for both VO2+/VO2+ and V3+/V2+ redox couples in vanadium flow batteries (VFBs) has been investigated by directly introducing Bi on the surface of carbon felt (CF). The results show that Bi h...The effect of bismuth (Bi) for both VO2+/VO2+ and V3+/V2+ redox couples in vanadium flow batteries (VFBs) has been investigated by directly introducing Bi on the surface of carbon felt (CF). The results show that Bi has no catalytic effect for VO2+/VO2(+) redox couple. During the first charge process, Bi is oxidized to Bi3+ (never return back to Bi metal in the subsequent cycles) due to the low standard redox potential of 0.308 V (vs. SHE) for Bi3+/Bi redox couple compared with VO2+/VO2+ redox couple and Bi3+ exhibit no (or neglectable) electro-catalytic activity. Additionally, the relationship between Bi loading and electrochemical activity for V3+/V2+ redox couple was studied in detail. 2 wt% Bi-modified carbon felt (2%-BiCF) exhibits the highest electrochemical activity. Using it as negative electrode, a high energy efficiency (EE) of 79.0% can be achieved at a high current density of 160 mA/cm(2), which is 5.5% higher than the pristine one. Moreover, the electrolyte utilization ratio is also increased by more than 30%. Even the cell operated at 140 mA/cm(2) for over 300 cycles, the EE can reach 80.9% without obvious fluctuation and attenuation, suggesting excellent catalytic activity and electrochemical stability in VFBs. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
Ultrathin free-standing electrospun carbon nanofiber web（ECNFW） used for the electrodes of the vanadium flow battery（VFB） has been fabricated by the electrospinning technique followed by the carbonization process ...Ultrathin free-standing electrospun carbon nanofiber web（ECNFW） used for the electrodes of the vanadium flow battery（VFB） has been fabricated by the electrospinning technique followed by the carbonization process in this study to reduce the ohmic polarization of the VFB. The microstructure, surface chemistry and electrochemical performance of ECNFW carbonized at various temperatures from 800 to 1400 °C have been investigated. The results show that ECNFW carbonized at 1100 °C exhibits the highest electrocatalytic activity toward the V;/V;redox reaction, and its electrocatalytic activity decreases along with the increase of carbonization temperature due to the drooping of the surface functional groups.While for the VO;/VO;redox couple, the electrocatalytic activity of ECNFW carbonized above 1100 °C barely changes as the carbonization temperature rises. It indicates that the surface functional groups could function as the reaction sites for the V;/V;redox couple, but have not any catalytic effect for the VO;/VO;redox couple. And the single cell test result suggests that ECNFW carbonized at 1100 °C is a promising material as the VFB electrode and the VFB with ECNFW electrodes obtains a super low internal resistance of 250 mΩ cm;.展开更多
Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However...Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However,the widespread adoption of VFB s is hindered by the use of expensive Nafion membranes.Herein,we report a soft template-induced method to develop a porous polyvinylidene fluoride(PVDF)membrane for VFB applications.By incorporating water-soluble and flexible polyethylene glycol(PEG 400)as a soft template,we induced the aggregation of hydrophilic sulfonated poly(ether ether ketone),resulting in phase separation from the hydrophobic PVDF polymer during membrane formation.This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution.The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm^(2),and the VFB exhibited a Coulombic efficiency of 95.2%and a voltage efficiency of 87.8%.These findings provide valuable insights for the development of highly stable membranes for VFB applications.展开更多
Swelling-induced morpholine functionalized adamantane-containing poly(aryl ether ketone) (MAPEK) membranes were prepared for vanadium flow batteries. MAPEK membranes were prepared from chloromethylated polymer and mor...Swelling-induced morpholine functionalized adamantane-containing poly(aryl ether ketone) (MAPEK) membranes were prepared for vanadium flow batteries. MAPEK membranes were prepared from chloromethylated polymer and morpholine and further swelling-induced with hot phosphoric acid to obtain membranes with enhanced ionic conductivity. The swelling, selectivity, and ionic conductivity of MAPEK membranes were regulated by varying the swelling temperature. Selective swelling-induced microphase separation in MAPEK membranes, forming wider ion transport pathways and resulting in low area resistance. The unique rigid adamantane-containing backbone limited the swelling of membranes. Consequently, MAPEK membranes showed excellent selectivity and conductivity (vanadium ion permeability coefficient of MAPEK membranes was lower than 3.82 × 0−7 cm2min−1) (Nafion212 membrane, 42.5 × 0−7 cm2min−1), and MAPEK-150 membrane exhibited low area resistance (0.17 Ωcm2). The vanadium flow batteries (VFB) with MAPEK-150 membrane exhibited high energy efficiency (91.1% at 80 mAcm−2, 81.4% at 200 mAcm−2). Furthermore, MAPEK membranes showed good stability in VFB and oxidative electrolytes. The swelling-induced method utilized in this work is a versatile and facile method to enhance the conductivity of ion-exchange membranes.展开更多
As one of the most important components of the vanadium redox flow battery （VRFB）, the electrolyte can impose a significant impact on cell properties, performance and capital cost. In particular, the electrolyte com...As one of the most important components of the vanadium redox flow battery （VRFB）, the electrolyte can impose a significant impact on cell properties, performance and capital cost. In particular, the electrolyte composition will influence energy density, operating temperature range and the practical applications of the VRFB. Various approaches to increase the energy density and operating temperature range have been proposed. The presence of electrolyte impurities, or the addition of a small amount of other chemical species into the vanadium solution can alter the stability of the electrolyte and influence cell perfor- mance, operating temperature range, energy density, electrochemical kinetics and cost effectiveness. This review provides a detailed overview of research on electrolyte additives including stabilizing agents, im- mobilizing agents, kinetic enhancers, as well as electrolyte impurities and chemical reductants that can be used for different purposes in the VRFBs.展开更多
Carbon cloth modified by hydrothermal treatment in ammonia water is developed as the positive electrode with high electrochemical performance for vanadium redox flow batteries. The SEM shows that the treatment has no ...Carbon cloth modified by hydrothermal treatment in ammonia water is developed as the positive electrode with high electrochemical performance for vanadium redox flow batteries. The SEM shows that the treatment has no obvious influence on the morphology of carbon cloth. XPS measurements indicate that the nitrogenous functional groups can be introduced on the surface of carbon cloth successfully. The electrochemical performance of V(IV)/V(V) redox couple on the prepared electrode is evaluated with cyclic voltammetry and linear sweep voltammetry measurements. The N-doped carbon cloth exhibits outstanding electrochemical activity and reversibility toward V(IV)/V(V) redox couple. The rate constant of V(IV)/V(V) redox reaction on carbon cloth can increase to 2.27 x 10(-4) cm/s from 1.47 x 10(-4) cm/s after nitrogen doping. The cell using N-doped carbon cloth as positive electrode has larger discharge capacity and higher energy efficiency compared with the cell using pristine carbon cloth. The average energy efficiency of the cell using N-doped carbon cloth for 50 cycles at 30 mA/cm(2) is 87.8%, 4.3% larger than that of the cell using pristine carbon cloth. It indicates that the N-doped carbon cloth has a promise application prospect in vanadium redox flow batteries. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.21975267)the Central Guidance on Local Science and Technology Development Fund of Liaoning Province(No:2022JH6/100100001)。
文摘There is an urgent need to break through the trade-off between proton conductivity and ion selectivity of proton exchange membrane(PEM)in vanadium flow battery(VFB).Proton channels in PEM are the key to controlling the ion sieving and proton conductivity in VFB.Herein,two types of proton channels are reconstructed in the hybrid membrane via introducing modified Zr-MOFs(IM-UIO-66-AS)into SPEEK matrix.Internal proton channels in IM-UIO-66-AS and interfacial proton channels between grafted imidazole groups on Zr-MOFs and SPEEK greatly improve the conductivity of the IM-UIO-66-AS/SPEEK hybrid membrane.More importantly,both reconstructed proton channels block the vanadium-ion permeation to realize enhanced ion selectivity according to the size sieving and Donnan exclusion effects,respectively.Moreover,the hybrid membrane exhibits good mechanical property and dimensional stability.Benefiting from such rational design,a VFB loading with the optimized membrane exhibits enhanced voltage efficiency of 79.9%and outstanding energy efficiency of 79.6%at 200 m A cm^(-2),and keeps a notable cycle stability for 300 cycles in the long-term cycling test.Therefore,this study provides inspiration for preparing next-generation PEMs with high ion selectivity and proton conductivity for VFB application.
基金the financial supports from the National Key Research and Development Program of China (2016YFB0101203)China MOST (Ministry of Science and Technology) Innovation Team in Key Area (2016RA4053)+2 种基金the National Natural Science Foundation of China (21276252)Natural Science Foundation of Liaoning Province (2015020630)State Key Laboratory of Fine Chemicals (Panjin) (JH2014009)
文摘For improvement of vanadium redox flow battery （VRB） performance, novel amphoteric semi- interpenetrating membranes （ASIPN） were prepared using poly（ether ether ketone） （PEEK） and polysul- fone （PSf）, the former bearing sulfonic groups and the latter imidazolium. These two groups form ionic crosslinks between PEEK and PSf; meanwhile, covalent cross links were built between PSf chains with ad- dition of N-（3-aminopropyl）-imidazole. The amphoteric nature of the membrane allows facile proton and anion transport; the IPN structure and the presence of imidazolium cation effectively suppress vanadium ion crossover through the membrane. Therefore, the ASIPN based VRBs show higher Coulombic efficiency and energy efficiency than that assembled with pristine SPEEK and Nation 212 membranes. Our work demonstrates that the ASIPN membranes are promising for VRB applications.
基金the financial support of the National Natural Science Foundation of China(Nos.22075276,U19A2016,U22B6012)CAS Strategic Leading Science&Technology Program(A)(No.XDA21070000)+2 种基金Dalian High Level Talent Innovation Support Program(No.2020RD05)the Development of Scientic and Technological Project of the Jilin Province(No.20210101126JC)International Partnership Program of Chinese Academy of Sciences(No.121421KYSB20210028)。
文摘Vanadium flow batteries(VFBs)have drawn considerable attention as an emerging technology for largescale energy storage systems(ESSs).One of the pivotal challenges is the availability of eligible ion exchange membranes(ICMs)that provide high ion selectivity,proton conductivity,and stability under rigorous condition.Herein,a‘side-chain-type’strategy has been employed to fabricate highly stable phenolphthalein-based cardo poly(arylene ether ketone)s(PAEKs)membrane with low area resistance(0.058Ωcm^(2)),in which flexible alkyl spacers effectively alleviated inductive withdrawing effect from terminal ion exchange groups thus enabling a stable backbone.The assembled VFBs based on PAEKs bearing pendent alkyl chain terminated with quaternary ammonium(Q-PPhEK)demonstrated an energy efficiency above 80%over 700 cycles at 160 mA/cm^(2).Such a remarkable results revealed that the side-chain-type strategy contributed to enhancing the ICMs stability in strong oxidizing environment,meanwhile,more interesting backbones would be woken with this design engaging in stable ICMs for VFBs.
基金supported by the National Natural Science Foundation of China(No.51872090)Natural Science Foundation of Hebei Province(No.E2019209433,E2022209158)Colleges and Universities in Hebei Province Science and Technology Research Project(No.JZX2024026).
文摘The scarcity of wettability,insufficient active sites,and low surface area of graphite felt(GF)have long been suppressing the performance of vanadium redox flow batteries(VRFBs).Herein,an ultra-homogeneous multipledimensioned defect,including nano-scale etching and atomic-scale N,O codoping,was used to modify GF by the molten salt system.NH_(4)Cl and KClO_(3) were added simultaneously to the system to obtain porous N/O co-doped electrode(GF/ON),where KClO_(3) was used to ultra-homogeneously etch,and O-functionalize electrode,and NH4Cl was used as N dopant,respectively.GF/ON presents better electrochemical catalysis for VO_(2)+/VO_(2)+ and V3+/V2+ reactions than only O-functionalized electrodes(GF/O)and GF.The enhanced electrochemical properties are attributed to an increase in active sites,surface area,and wettability,as well as the synergistic effect of N and O,which is also supported by the density functional theory calculations.Further,the cell using GF/ON shows higher discharge capacity,energy efficiency,and stability for cycling performance than the pristine cell at 140 mA cm^(−2) for 200 cycles.Moreover,the energy efficiency of the modified cell is increased by 9.7% from 55.2% for the pristine cell at 260 mA cm^(−2).Such an ultra-homogeneous etching with N and O co-doping through“boiling”molten salt medium provides an effective and practical application potential way to prepare superior electrodes for VRFB.
基金financial support from the National Natural Science Foundation of China (No. 21576154)the Open Fund of The State Key Laboratory of Refractories and Metallurgy (No. G201809)the Shenzhen Basic Research Project (Nos. JCYJ20170412170756603 and JCYJ20170307152754218)
文摘Vanadium flow battery （VFB） is a fast going and promising system for large-scale stationary energy stor- age. However, drawbacks such as low power density and narrow temperature window caused by poor catalytic activity of graphite felt （GF） electrodes limit its worldwide application. In this paper, bismuth, as a low-cost, no-toxic and high-activity electrocatalyst, is used to modify the thermal activated GF （TGF） via a facile hydrothermal method. Bismuth can effectively inhibit the side reaction of hydrogen evolution in wide temperature range, while promoting the V2＋/V3＋ redox reaction. As a result, the VFB assembled with Bi/TGF as negative electrode demonstrates outstanding rate performance under the current density up to 400 mAcm-2, as well as a long-term stability over 600 charging/discharging cycles at a high cur- rent density of 150mA cm-2. Moreover, it also shows excellent temperature adaptability from -10 ℃ to 50 ℃ and high durability for life test at the temperature of 50 ℃.
基金This work was financially supported by the National Natural Science Foundation of China Youth Fund(No.21703263)Open project of State Key Laboratory of Heavy Oil Processing in China University of Petroleum(No.Y7F1911191).
文摘Vanadium flow battery(VFB)is one of the most promising energy storage technologies because of its superior safety,reliability and cycle life,but the poor electrochemical performance at high cur-rent density limits its commercial application.Herein,an advanced design of the dual-gradient carbon nanofibers/graphite felt(DG-CNFs/GF)composite electrode is firstly proposed for the next-generation VFB with high power density.Specifically,there is a macro gradient distribution of CNFs along the thickness direction of the electrode,meanwhile a micro gradient distribution of CNFs is also existed along the ra-dial direction of a single fiber,and both the macro and micro gradient structure are verified through the physicochemical characterizations.In addition,the DG-CNFs/GF with a dual-gradient structure exhibits an excellent electrocatalytic activity and a fast mass transfer characteristic.It is worth noting that the energy conversion efficiencies,cycling stability in addition to power density of VFB with DG-CNFs/GF are much better than those with commercial GF,which make the dual-gradient DG-CNFs/GF to be a promis-ing alternative.Most importantly,the accomplishment of this work will provide a promising development direction of the highly efficient electrode for the next-generation VFB with high power density.
基金financial support from the French National Research Agency(project ANR-17-CE05-0023)。
文摘The vanadium redox flow battery(VRFB)has been receiving great attention in recent years as one of the most viable energy storage technologies for large-scale applications.However,higher concentrations of vanadium species are required in the H_(2)O-H_(2)SO_(4) electrolyte in order to improve the VRFB energy density.This might lead to unwanted precipitation of vanadium compounds,whose nature has not been accurately characterized yet.For this purpose,this study reports the preparation ofⅤ^((Ⅱ)),ⅤV^((Ⅲ)),Ⅴ^((Ⅳ))andⅤ^((Ⅴ))supersaturated solutions in a 5 M H_(2)SO_(4)-H_(2)O electrolyte by an electrolytic method,from the only vanadium sulfate compound commercially available(VOSO_(4)).The precipitates obtained by ageing of the stirred solutions are representative of the solids that may form in a VRFB operated with such supersaturated solutions.The solid phases are identified using thermogravimetric analysis,X-ray diffraction and SEM.We report that dissolvedⅤ^((Ⅱ)),Ⅴ^((Ⅲ))andⅤ^((Ⅳ))species precipitate as crystals of VSO_(4),V_(2)(SO_(4))3 and VOSO_(4) hydrates and not in their anhydrous form;conversely V^((Ⅴ))precipitates as an amorphous V_(2) O_(5) oxide partially hydrated.The measured hydration degrees(respectively 1.5,9,3 and 0.26 mol of H_(2)O per mol of compound)might significantly affect the overall engineering of VRFB operating with high vanadium concentrations.
基金financially supported by the National Natural Science Foundation of China(No.51772097)Hebei Natural Science Fund for Distinguished Young Scholar(No.E2019209433)Training Program of Innovation and Entrepreneurship for Undergraduates(No.X2018156,North China University of Science and Technology)。
文摘Vanadium redox flow battery(VRFB)is one of the most promising large-scale energy storage systems,which ranges from kilowatt to megawatt.Nevertheless,poor electrochemical activity of electrode for two redox couples still restricts the extensive applications of VRFB.Compared with V^(2+)/V^(3+)redox reaction,V^(2+)/V^(3+)reaction plays a more significant role in voltage loss of VRFB owing to slow heterogeneous electron transfer rate.Herein,N-doped carbon materials derived from scaphium scaphigerum have been developed as negative electrocatalyst by hydrothermal carbonization and high-temperature nitridation treatments.The undoped carbon material hardly has electrocatalytic ability for V^(2+)/V^(3+)reaction.Based on this,N-doped carbon materials with urea as nitrogen source exhibit excellent electrocatalytic properties.And the material nitrided at 850°C(SSC/N-850)exhibits the best performance among those from700 to 1000℃.SSC/N-850 can accelerate the electrode process including V^(2+)/V^(3+)reaction and mass transfer of active ions due to the large reaction place,more active sites,and good hydrophilicity.The effect of catalyst on comprehensive performance of cell was evaluated.SSC/N-850 can improve the charge-discharge performance greatly.Utilization of SSC/N-850 can lessen the electrochemical polarization of cell,further resulting in increased discharge capacity and energy efficiency.Discharge capacity and energy efficiency increase by 81.5%and 9.8%by using SSC/N-850 as negative catalyst at 150 m A cm^(-2),respectively.Our study reveals that the developed biomass-derived carbon materials are the low-cost and efficient negative electrocatalyst for VRFB system.
基金financial support through a KekuléPh.D.fellowship by the Fonds der Chemischen Industrie(FCI)support from the China Scholarship Council(No.202106950013)。
文摘The parasitic hydrogen evolution reaction(HER)in the negative half-cell of vanadium redox flow batteries(VRFBs)causes severe efficiency losses.Thus,a deeper understanding of this process and the accompanying bubble formation is crucial.This benchmarking study locally analyzes the bubble distribution in thick,porous electrodes for the first time using deep learning-based image segmentation of synchrotron X-ray micro-tomograms.Each large three-dimensional data set was processed precisely in less than one minute while minimizing human errors and pointing out areas of increased HER activity in VRFBs.The study systematically varies the electrode potential and material,concluding that more negative electrode potentials of-200 m V vs.reversible hydrogen electrode(RHE)and lower cause more substantial bubble formation,resulting in bubble fractions of around 15%–20%in carbon felt electrodes.Contrarily,the bubble fractions stay only around 2%in an electrode combining carbon felt and carbon paper.The detected areas with high HER activity,such as the border subregion with more than 30%bubble fraction in carbon felt electrodes,the cutting edges,and preferential spots in the electrode bulk,are potential-independent and suggest that larger electrodes with a higher bulk-to-border ratio might reduce HER-related performance losses.The described combination of electrochemical measurements,local X-ray microtomography,AI-based segmentation,and 3D morphometric analysis is a powerful and novel approach for local bubble analysis in three-dimensional porous electrodes,providing an essential toolkit for a broad community working on bubble-generating electrochemical systems.
基金supported by the National Natural Science Foundation of China(U1808209)Fundamental Research Funds for the Central Universities(DUT18JC40)Liaoning Province Science and Technology Department(201601037)。
文摘A new amphoteric membrane was prepared by blending long-side-chain sulfonated poly(2,6-dimethyl-1,4-phenylene oxide)(S-L-PPO)and polybenzimidazole(PBI)for vanadium redox flow battery(VRFB)application.An acid-base pair structure formed between the imidazole of PBI and sulfonic acid of S-L-PPO resulted in lowered swelling ratio.It favors to reduce the vanadium permeation.While,the increased sulfonic acid concentration ensured that proton conductivity was still at a high level.As a result,a better balance between the vanadium ion permeation(6.1×10^-9 cm^2·s^-1)and proton conductivity(50.8 m S·cm^-1)in the S-L-PPO/PBI-10%membrane was achieved.The VRFB performance with S-L-PPO/PBI-10%membrane exhibited an EE of 82.7%,which was higher than those of pristine S-L-PPO(81.8%)and Nafion 212(78.0%)at 120 m A·cm^-2.In addition,the S-LPPO/PBI-10%membrane had a much longer self-discharge duration time(142 h)than that of Nafion 212(23 h).
基金financial support of the National Natural Science Foundation of China (project no. 51504231, 51504232, 51774262 and 21325628)Open Project of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization (project no. CNMRCUKF1704)
文摘In the present paper, multi-walled carbon nanotubes（MWCNTs） are successfully assembled on graphite felt（GF） using sucrose pyrolysis method for the first time. The in situ formed pyrolytic carbon is chosen as the binder because it is essentially carbon materials as well as CNTs and GF which has a natural tendency to achieve high bonding strength and low contact resistance. The MWCNTs/GF electrode is demonstrated to increase surface area, reduce polarization, lower charge transfer resistance and improve energy conversion efficiency comparing with GF. This excellent electrochemical performance is mainly ascribed to the high electro-catalytic activity of MWCNTs and increasing surface area.
基金supported by the National Natural Science Foundation of China(no.21773102)
文摘The electrolyte is one of the most important components of vanadium redox flow battery （VRFB）. and its stability and solubility determines the energy density of a VRFB. The performance of current positive elec- trolyte is limited by the low stability of VO2＋ at a higher temperature. Phosphate is proved to be a very effective additive to improve the stability of VO2＋. Even though, the stabilizing mechanism is still not clear, which hinders the further development of VRFBs. In this paper, to clarify the effect of phosphate additive on the positive electrolyte stability, the hydration structures of VO2＋ cations and the reaction mechanisms of precipitation with or without phosphate in the supporting electrolyte of H_2SO_4 solutions were investigated in detail based on calculations of electronic structure. The stable configurations of com- plexes were optimized at the B3LYP/6-311 ＋ G（d,p） level of theory. The zero-point energies and Gibbs free energies for these complexes were further evaluated at the B3LYP/aug-cc-pVTZ level of theory. It shows that a structure of [VO_2（H_2O）_2]＋ surrounded by water molecules in H2S04 solution can be formed at the room temperature. With the temperature rises, [VO_2（H_2O）_2]＋ will lose a proton and form the interme- diate of VO（OH）_3, and the further dehydration among VO（OH）_3 molecules will create the precipitate of V_2O_5. When H_3PO_4 was added into electrolytes, the V-O-P bond-containing neutral compound could be formed through interaction between VO（OH）_3 and H_3PO_4, and the activation energy of forming the V-O-P bond-containing neutral compound is about 7 kcal tool-1 lower than that of the VO（OH）_3 dehydration, which could avoid the precipitation of V_2O_5 and improve the electrolyte stability.
基金Funded by the Foundation of Sichuan Agricultural University(Nos.03572898 and 90214176)
文摘SPES/PVDF blends were employed to prepare the ion exchange membranes for vanadium redox flow battery(VRB) application for the first time. The addition of the highly crystalline and hydrophobic PVDF effectively limited the swelling behavior of SPES. The vanadium ion permeability of SPES/PVDF membranes was one order of magnitude lower than that of Nafion 117 membrane and pristine SPES membrane. Single cells with SPES/PVDF composite membranes showed significantly lower capacity loss, higher coulombic efficiency and higher energy efficiency than that with Nafion117 and pristine SPES membranes. The blend membrane with 40 wt% of PVDF(denoted as S_(0.6) P_(0.4)) showed energy efficiency of 83.2% at 30 mA?cm^(-2), which was superior to that of the Nafion117 and SPES membranes. In the self-discharge test, S_(0.6) P_(0.4) membrane showed twice longer duration in open circuit decay than that with Nafion 117 membrane. With all the good properties and low cost, the SPES/PVDF membranes are expected to have excellent commercial prospects as ion exchange membranes for VRB system.
基金supported by the National Natural Science Foundation of China(21576154)the Natural Science Foundation of Guangdong Province(2022A1515011999 and 2019A1515011955)the Shenzhen Basic Research Project(20200829101039001 and GXWD20201231165806004)。
文摘Electrode materials with good redox kinetics,excellent mass transfer characteristics and ultra-high stability play a crucial role in reducing the life-cycle cost and prolonging the maintenance-free time of the vanadium flow batteries(VFB).Herein,a nitrogen-doped porous graphite felt electrode(N-PGF)is proposed by growing ZIF-67 nanoparticles on carbon fibers and then calcinating and acid etching.The multi-scale structure of“carbon fiber gap(electrolyte flow),micro/nano pore(active species diffusion)and Nitrogen active center(reaction site)”in N-PGF electrode effectively increases the catalytic sites and promotes mass transfer characteristics.Reasonable electrode design makes the battery show excellent rate performance and ultra-high cycling stability.The peak power density of the battery reaches 1006 mW cm^(-2).During 1000 cycles at 150 mA cm^(-2),the average discharge capacity and average discharge energy of N-PGF increase substantially by 11.6%and 23.4%compared with the benchmark thermal activated graphite felt,respectively.More excitingly,after ultra-long term(5000 cycles)operation at an ultra-high current density(300 mA cm^(-2)),N-PGF exhibits an unprecedented energy efficiency retention(99.79%)and electrochemical performance stability.
基金the financial support from the China Natural Science Foundation(Grant nos.51403209,21406221,21206158,21476224,21406219 and 51361135701)the Outstanding Young Scientist Foundation,Chinese Academy of Sciences(CAS)+2 种基金Supported by the Key Research Program of the Chinese Academy of Sciences(KG2D-EW-602-2)Science and Technology Service Network Initiative(KFJ-EW-STS-108)Dalian Municipal Outstanding Young Talent Foundation(2014J11JH131)
文摘The effect of bismuth (Bi) for both VO2+/VO2+ and V3+/V2+ redox couples in vanadium flow batteries (VFBs) has been investigated by directly introducing Bi on the surface of carbon felt (CF). The results show that Bi has no catalytic effect for VO2+/VO2(+) redox couple. During the first charge process, Bi is oxidized to Bi3+ (never return back to Bi metal in the subsequent cycles) due to the low standard redox potential of 0.308 V (vs. SHE) for Bi3+/Bi redox couple compared with VO2+/VO2+ redox couple and Bi3+ exhibit no (or neglectable) electro-catalytic activity. Additionally, the relationship between Bi loading and electrochemical activity for V3+/V2+ redox couple was studied in detail. 2 wt% Bi-modified carbon felt (2%-BiCF) exhibits the highest electrochemical activity. Using it as negative electrode, a high energy efficiency (EE) of 79.0% can be achieved at a high current density of 160 mA/cm(2), which is 5.5% higher than the pristine one. Moreover, the electrolyte utilization ratio is also increased by more than 30%. Even the cell operated at 140 mA/cm(2) for over 300 cycles, the EE can reach 80.9% without obvious fluctuation and attenuation, suggesting excellent catalytic activity and electrochemical stability in VFBs. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
基金the financial support from the National Natural Science Foundation of China(Grant nos.21506210 and 51361135701)
文摘Ultrathin free-standing electrospun carbon nanofiber web（ECNFW） used for the electrodes of the vanadium flow battery（VFB） has been fabricated by the electrospinning technique followed by the carbonization process in this study to reduce the ohmic polarization of the VFB. The microstructure, surface chemistry and electrochemical performance of ECNFW carbonized at various temperatures from 800 to 1400 °C have been investigated. The results show that ECNFW carbonized at 1100 °C exhibits the highest electrocatalytic activity toward the V;/V;redox reaction, and its electrocatalytic activity decreases along with the increase of carbonization temperature due to the drooping of the surface functional groups.While for the VO;/VO;redox couple, the electrocatalytic activity of ECNFW carbonized above 1100 °C barely changes as the carbonization temperature rises. It indicates that the surface functional groups could function as the reaction sites for the V;/V;redox couple, but have not any catalytic effect for the VO;/VO;redox couple. And the single cell test result suggests that ECNFW carbonized at 1100 °C is a promising material as the VFB electrode and the VFB with ECNFW electrodes obtains a super low internal resistance of 250 mΩ cm;.
基金financially supported by Open Fund of Material Corrosion and Protection Key Laboratory of Sichuan Province of China(No.2020CL09)Hunan Key Laboratory of Applied Environmental Photocatalysis(No.2214503)。
文摘Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However,the widespread adoption of VFB s is hindered by the use of expensive Nafion membranes.Herein,we report a soft template-induced method to develop a porous polyvinylidene fluoride(PVDF)membrane for VFB applications.By incorporating water-soluble and flexible polyethylene glycol(PEG 400)as a soft template,we induced the aggregation of hydrophilic sulfonated poly(ether ether ketone),resulting in phase separation from the hydrophobic PVDF polymer during membrane formation.This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution.The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm^(2),and the VFB exhibited a Coulombic efficiency of 95.2%and a voltage efficiency of 87.8%.These findings provide valuable insights for the development of highly stable membranes for VFB applications.
基金supports from the National Natural Science Foundation of China(21444006,21706164)the State Key Laboratory of Fine Chemicals,Dalian University of Technology(KF2106)+3 种基金Liaoning Provincial Education Department(LJ2019005)Natural Science Foundation of Liaoning Province(2021-NLTS-12-01)Liaoning Revitalization Talents Program(XLYC1907029)Liaoning Provincial Science and Technology Department(2019-MS-261)is greatly appreciated.
文摘Swelling-induced morpholine functionalized adamantane-containing poly(aryl ether ketone) (MAPEK) membranes were prepared for vanadium flow batteries. MAPEK membranes were prepared from chloromethylated polymer and morpholine and further swelling-induced with hot phosphoric acid to obtain membranes with enhanced ionic conductivity. The swelling, selectivity, and ionic conductivity of MAPEK membranes were regulated by varying the swelling temperature. Selective swelling-induced microphase separation in MAPEK membranes, forming wider ion transport pathways and resulting in low area resistance. The unique rigid adamantane-containing backbone limited the swelling of membranes. Consequently, MAPEK membranes showed excellent selectivity and conductivity (vanadium ion permeability coefficient of MAPEK membranes was lower than 3.82 × 0−7 cm2min−1) (Nafion212 membrane, 42.5 × 0−7 cm2min−1), and MAPEK-150 membrane exhibited low area resistance (0.17 Ωcm2). The vanadium flow batteries (VFB) with MAPEK-150 membrane exhibited high energy efficiency (91.1% at 80 mAcm−2, 81.4% at 200 mAcm−2). Furthermore, MAPEK membranes showed good stability in VFB and oxidative electrolytes. The swelling-induced method utilized in this work is a versatile and facile method to enhance the conductivity of ion-exchange membranes.
文摘As one of the most important components of the vanadium redox flow battery （VRFB）, the electrolyte can impose a significant impact on cell properties, performance and capital cost. In particular, the electrolyte composition will influence energy density, operating temperature range and the practical applications of the VRFB. Various approaches to increase the energy density and operating temperature range have been proposed. The presence of electrolyte impurities, or the addition of a small amount of other chemical species into the vanadium solution can alter the stability of the electrolyte and influence cell perfor- mance, operating temperature range, energy density, electrochemical kinetics and cost effectiveness. This review provides a detailed overview of research on electrolyte additives including stabilizing agents, im- mobilizing agents, kinetic enhancers, as well as electrolyte impurities and chemical reductants that can be used for different purposes in the VRFBs.
基金supported by the Open Project Program of Jiangxi Engineering Research Center of Process and Equipment for New Energy,East China Institute of Technology(No.JXNE2015-14)Youth Foundation of Education Department of Hebei Province(No.QN2016183)the National Natural Science Foundation of China(No.51362002)
文摘Carbon cloth modified by hydrothermal treatment in ammonia water is developed as the positive electrode with high electrochemical performance for vanadium redox flow batteries. The SEM shows that the treatment has no obvious influence on the morphology of carbon cloth. XPS measurements indicate that the nitrogenous functional groups can be introduced on the surface of carbon cloth successfully. The electrochemical performance of V(IV)/V(V) redox couple on the prepared electrode is evaluated with cyclic voltammetry and linear sweep voltammetry measurements. The N-doped carbon cloth exhibits outstanding electrochemical activity and reversibility toward V(IV)/V(V) redox couple. The rate constant of V(IV)/V(V) redox reaction on carbon cloth can increase to 2.27 x 10(-4) cm/s from 1.47 x 10(-4) cm/s after nitrogen doping. The cell using N-doped carbon cloth as positive electrode has larger discharge capacity and higher energy efficiency compared with the cell using pristine carbon cloth. The average energy efficiency of the cell using N-doped carbon cloth for 50 cycles at 30 mA/cm(2) is 87.8%, 4.3% larger than that of the cell using pristine carbon cloth. It indicates that the N-doped carbon cloth has a promise application prospect in vanadium redox flow batteries. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
