Highly efficient vanadium redox flow batteries enabled by a trilayer polybenzimidazole membrane assembly

A novel polybenzimidazole(PBI)-based trilayer membrane assembly is developed for application in vanadium redox flow battery(VRFB).The membrane comprises a 1μm thin cross-linked poly[2,2′-(p-oxydiphenylene)−5,5′-bibenzimidazole](OPBI)sandwiched between two 20μm thick porous OPBI membranes(p-OPBI)without further lamination steps.The trilayer membrane demonstrates exceptional properties,such as high conductivity and low area-specific resistance(ASR)of 51 mS cm^(−1) and 81mΩ cm^(2),respectively.Contact with vanadium electrolyte increases the ASR of trilayer membrane only to 158mΩ cm^(2),while that of Nafion is 193mΩ cm^(2).VO^(2+) permeability is 2.73×10^(-9) cm^(2) min^(−1),about 150 times lower than that of Nafion NR212.In addition,the membrane has high mechanical strength and high chemical stability against VO^(2+).In VRFB,the combination of low resistance and low vanadium permeability results in excellent performance,revealing high Coulombic efficiency(>99%),high energy efficiency(EE;90.8% at current density of 80mA cm^(−2)),and long-term durability.The EE is one of the best reported to date.

Review on current development of polybenzimidazole membrane for lithium battery

With the rapid development of portable technology,lithium batteries have emerged as potential candidates for high-performance energy storage systems owing to their high energy density and cycling stability.Among the key components of a lithium battery system,the separator plays a critical role as it directly influences the battery performance benchmark(cycling performance and safety).However,traditional polyolefin separators(polypropylene/polyethylene)are unable to meet the demands of highperformance and safer battery systems due to their poor electrolyte compatibility,thermal runaways,and ultimate growth of dendrites.In contrast,membranes fabricated using polybenzimidazole(PBI)exhibit excellent electrolyte wettability and outstanding thermal dimensional stability,thus holding great potential as separators for high-performance and high-safety batteries.In this paper,we present a comprehensive review of the general requirements for separators,synthesis technology for separators,and research trends focusing PBI membranes in lithium batteries to alleviate the current commercial challenges faced by conventional polyolefin separators.In addition,we discuss the future development direction for PBI battery separators by considering various factors such as production cost,ecological footprint,preparation technology,and battery component compatibility.By exploring these perspectives,we aim to promote the continued application and exploration of PBI-based materials to advance lithium battery technology.

Ionic potency regulation of coagulation bath induced by saline solution to control over the pore structure of PBI membrane for highperformance lithium metal batteries

In this study,we have explored the use of water as a non-solvent for tuning the microstructure of poly-benzimidazole(PBI)membranes,which are potential separators for lithium metal batteries(LMBs).The traditional method for membrane synthesis called nonsolvent-induced phase separation(NIPS),usually relies on hazardous and costly organic non-solvents.By dissolving sodium chloride(Nacl)in water,we could adjust the water ionic potency and the exchange speed of the non-solvent with the DMAC solution to change the micropore structure of the PBI membrane.With increasing Nacl concentration,the micro-pores in the PBI membrane transitioned from finger-like to sponge-like morphology.Compared to com-mercial separators like the Celgard separator,the PBI membrane with sponge-like micropores exhibited better regulation of lithium deposition and improved Li^(+) transportation capability due to its good wetta-bility with the electrolyte.Consequently,the PBI membrane-based Li/Li symmetric cell and Li/LiFePO_(4) full cell demonstrated superior performance compared to the Celgard-based ones.This research proposes an eco-friendly and scalable synthetic approach for fabricating commercial separators for LMBs,addressing the issue of lithium dendrite growth and improving overall battery safety and performance.

Gel-state polybenzimidazole proton exchange membranes with flexible alkyl sulfonic acid side chains for a wider operating temperature range(25–240 ℃)

High-temperature proton exchange membrane fuel cells(HT-PEMFC) possess distinct technical advantages of high output power, simplified water/heat management, increased tolerance to fuel impurities and diverse fuel sources, within the temperature range of 120–200 ℃. However, for practical automobile applications, it was crucial to broaden their low-temperature operating window and enable cold start-up capability. Herein, gel-state phosphoric acid(PA) doped sulfonated polybenzimidazole(PBI) proton exchange membranes(PEMs) were designed and synthesized via PPA sol-gel process and in-situ sultone ring-opening reactions with various proton transport pathways based on absorbed PA, flexible alkyl chain connected sulfonic acid groups and imidazole sites. The effects of flexible alkyl sulfonic acid side chain length and content on PA doping level, proton conductivity, and membrane stability under different temperature and relative humidity(RH) were thoroughly investigated. The prepared gel-state membranes contained a self-assembled lamellar and porous structure that facilitated the absorption of a large amount of PA with rapid proton transporting mechanisms. At room temperature, the optimized membrane exhibited a proton conductivity of 0.069 S cm^(-1), which was further increased to 0.162 and 0.358 S cm^(-1)at 80 and 200 ℃, respectively, without additional humidification. The most significant contribution of this work was demonstrating the feasibility of gel-state sulfonated PBI membranes in expanding HT-PEMFC application opportunities over a wider operating range of 25 to 240 ℃.

Synthesis of a new aromatic diacid containing pyridine ring and related polybenzimidazole

A new aromatic diacid monomer containing pyridine unit,4-phenyl-2,6-bis[4-（4-carboxyphenoxy） phenyl]pyridine 3,was successfully synthesized in three steps,starting from 4-hydroxyacetophenone.The corresponding pyridine-containing polybenzimidazole was prepared via polycondensation of 3 with tetraaminodiphenyl ether（TADE） in poly（phosphoric acid）（PPA）.The resulting polybenzimidazole exhibits excellent solubility,good thermal stabilities and high thermal resistance.

Sulfonated polybenzimidazole/amine functionalized titanium dioxide(s PBI/AFT) composite electrolyte membranes for high temperature proton exchange membrane fuel cells usage

The novel sulfonated polybenzimidazole(sPBI)/amine functionalized titanium dioxide(AFT) composite membrane is devised and studied for its capability of the application of high temperature proton exchange membrane fuel cells(HT-PEMFCs),unlike the prior low temperature AFT endeavors.The high temperature compatibility was actualized because of the filling of free volumes in the rigid aromatic matrix of the composite with AFT nanoparticles which inhibited segmental motions of the chains and improved its thermal stability.Besides,amine functionalization of TiO2 enhanced their dispersion character in the sPBI matrix and shortened the interparticle separation gap which finally improved the proton transfer after establishing interconnected pathways and breeding more phosphoric acid(PA) doping.In addition,the appeared assembled clusters of AFT flourished a superior mechanical stability.Thus,the optimized sPBI/AFT(10 wt%) showed 65.3 MPa tensile strength;0.084 S·cm^-1 proton conductivity(at 160℃;in anhydrous conditions),28.6% water uptake and PA doping level of 23 mol per sPBI repeat unit.The maximum power density peak for sPBI/AFT-10 met the figure of0.42 W·cm^-2 at 160℃(in dry conditions) under atmospheric pressure with 1.5 and 2.5 stoichiometric flow rates of H2/air.These results affirmed the probable fitting of sPBI/AFT composite for HT-PEMFC applications.

A new long-side-chain sulfonated poly(2,6-dimethyl-1,4-phenylene oxide)(PPO)/polybenzimidazole(PBI)amphoteric membrane for vanadium redox flow battery

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).

Synthesis of Poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] and Poly(2,5-benzimidazole) by Microwave Irradiation

A rapid way assisted by microwave irradiation was proposed to synthesize poly[2,2＇-（m-phenylene）-5,5＇-bibenzimidazole]（PBI） and poly（2,5-benzimidazole）（ab-PBI）.Synthesis of PBI in polyphosphoric acid is conducted for 20 h or even more.Under microwave irradiation,the polycondensations could be completed in polyphosphoric acid within 3 h from 3,3＇-diaminobenzidine tetrahydrochloride（DAB·4HCl·2H2O） and isophthalic acid for PBI,and from 3,4-diaminobenzoic acids（DABA） for ab-PBI,respectively.The conditions for the polymerization including the power of microwave irradiation,temperature,heating time,and concentrations of the reactants in polyphosphoric acid were optimized.The inherent viscosity of the polymers in concentrated sulfuric acid at 30 ℃ was 0.9766 dL/g for PBI,and 0.6480 dL/g for ab-PBI,respectively.Characterization of the polymer products was made by nuclear magnetic resonance（1^H NMR）,Fourier transform infrared spectra（FTIR） and thermogravimetric analysis（TGA）.

Synthesis and Photophysical Properties of Dy^(3+) and Gd^(3+) Polymeric Complexes with Functionalized Polybenzimidazole Containing β-Diketone Side Group

The polymeric ligand PBIa （functionalized polybenzimidazole containing β-diketone side group） was successfully synthesized via the reaction of polybenzimidazole （PBI） with 3-Br-acetylacetone in DM SO solvent using Nail as the deprotonation reagent. Its corresponding polymeric complexes of Dy^3＋ and Gd^3＋ were prepared and characterized by FT-IR, ^1H NMR, molar conductance measurements, and thermal analysis. The photoluminescence properties and the probable mechanism of the Dy and Gd complexes were studied. The measurement and analysis of the thermal properties showed that these were thermal stable.

Modified silicon carbide whisker reinforced polybenzimidazole used for high temperature proton exchange membrane

Polybenzimidazole containing ether bond（OPBI） was reinforced with silicon carbide whisker（m Si C） modified by 3-aminopropyltriethoxysilane（KH550）, and then doped with phosphoric acid（PA） to obtain OPBI/m Si C/PA membranes. These OPBI/m Si C/PA membranes have excellent mechanical strength and oxidative stability and can be used for high temperature proton exchange membrane（HT-PEM）. The tensile strength of OPBI/m Si C/PA membranes ranges from 27.3 to 36.8 MPa, and it increases at first and then decreases with the increase of m Si C content. The high m Si C content and PA doping level contribute to improving the proton conductivity of membranes. The proton conductivity of PBI/m Si C-10/PA membrane is 27.1 m S cm-1 at 170℃ without humidity, with an increase of 55.7% compared with that of OPBI/PA membrane. These excellent properties make OPBI/m Si C/PA membranes promising membrane materials for HT-PEM applications.

POLYCAPROLACTAM MODIFIED BY POLYBENZIMIDAZOLE

Three polycaprolactam samples modified by 0.05—0.50% polybenzimidazole （PBI） by weight were prepared. Their structure and mechanical properties were characterized by means of FT-IR, SEM, DTA, density tensile, impact and viscoelastic method. PBI delayed the superimposed polymerization-crystallization process of the activated anionic polymerization of caprolactam. The monomer casting （MC） nylons modified by PBI had lower crystallinities, lower T;and more nearly perfect spherulites than MC nylon itself, and showed a typical toughening effect.

Influence of solvent on ion conductivity of polybenzimidazole proton exchange membranes for vanadium redox flow batteries

Polybenzimidazole(PBI)is a kind of proton transport membrane material,and its ion conductivity is a key factor affecting its application in vanadium redox flow batteries(VRFBs).The casting solvent of PBI has a significant influence on the acid doping level of PBI membranes which is closely related to ionic conductivity.In this paper,3,3′-diaminobenzidine(DABz)and 4,4′-Dicarboxydiphenylether(DCDPE)were used as raw materials by solution condensation to prepare the PBI with ether bond groups.The chemical structure of PBI was determined by1H NMR and FT-IR,and the prepared PBI had good solubility which can be dissolved in a variety of solvents.The PBI proton exchange membranes were prepared by solution coating with 5 different solvents of N,N-dimethylformamide(DMF),N,N-dimethylacetamide(DMAc),dimethyl sulfoxide(DMSO),1-methyl-2-pyrrolidone(NMP),methane sulfonic acid(MSA).The effects of different solvents on the ion conductivity and physicochemical properties were discussed in detail.The results showed that the PBI membrane prepared by using MSA as solvent(the PBI+MSA membrane)exhibits high water uptake,acid doping level and low vanadium ion permeability.The VRFB assembled with the PBI+MSA membrane exhibited higher coulombic efficiency(CE)99.87%and voltage efficiency(VE)84.50%than that of the commercial Nafion115 membrane at100 m A·cm-2,and after 480 cycles,the EE value can still be maintained at 83.73%.The self-discharge time of a single battery was recorded to be as long as 1000 h.All experimental data indicated that MSA is the best solvent for casting PBI membrane.

Synthesis and Characterization of Poly [2,2-( m-phenylene) -5,5-bibenzimidazole] in 1-butyl-3-methylimidazolium Chloride

Poly[ 2, 2-（m.phenylene） -5, 5-bibenzimidazole] （mPBI） were synthesized by mixing 3, 3＇, 4, 4＇-tetraaminobiphenyl and isophthallc acid in 1 -butyl-3 -methyUmidazolinm chloride （ E BMIM] CI）. Intrinsic viscosity of mPBI polymers was 0.67 dL/g which was measured in 96% sulfuric acid. The polymer was characterized by Fourier transform infrared spectroscopy （FTIR）, nuclear magnetic resonance （ 1H-NMR ）, and thermogravimetric analysis （TGA）. The effects of polymerization conditions on the intrinsic viscosity of mPBI were investigated. It showed that the molecular weight of polymer mainly depended on pre-reaction time and reaction temperature. Comparison of structure and properties of mPBI synthesized in ionic liquids（ILs） and polyphosphoric acid was also reported. It indicates that the ionic liquids are a kind of good solvents in synthesis process of m_PBI and ionic liquids mainly affect molecular weight of mPBL

两性分子掺杂自支撑单离子传导聚合物电解质及其锂金属二次电池

制备高离子电导率的自支撑单离子传导聚合物电解质仍然面临挑战.本文中,我们通过聚[4,4’(二苯醚基)-5,5’-联苯并咪唑]侧链化学接枝丙烷磺酰(三氟甲基磺酰)亚胺锂,得到自支撑聚合物电解质(PBIg-LiPSI).PBI-g-LiPSI具有优异的成膜性能,实验发现,掺杂两性分子1-甲基-3-丙烷磺酰(三氟甲基磺酰)亚胺咪唑内盐(MeImPSI)后,离子电导率和^(7)Li核磁共振峰的化学位移都随着掺杂两性分子的质量分数呈线性递增.PBI-g-LiPSI/MeImPSI(25 wt%)凝胶自支撑单离子传导聚合物电解质的室温离子电导率是0.68 mS cm^(-1),锂离子迁移数是0.95.使用该电解质隔膜的金属锂对称电池在±0.5 mA cm^(-2)@2 mA h cm^(-2)运行2100小时未发生短路,金属锂二次电池可在1C下稳定循环500圈.本工作开发了一种用于金属锂二次电池的两性分子掺杂自支撑单离子传导聚合物电解质.

Synthesis of pyridine-based poly(N-arylenebenzimidazole sulfone)

Poly（N-arylenebenzimidazole pyridine sulfone）（PNABIPS） has been prepared via the aromatic nucleophilic displacement reaction of 2,6-bis（2-benzimidazoly）pyridine（BBP） with bis（4-fluorophenyl） sulfone.BBP was synthesized by reaction of 2,6- pyridinedicarboxylic acid with 1,2-phenylenediamine in polyphosphoric acid.The chemical structure of BBP was confirmed by FTIR, HRMS,^1H NMR and ^13C NMR.The characterization of the polymer was performed with FT-IR,^1H NMR,elemental analysis, GPC,XRD,DSC,TGA and solubility tests.The polymer was obtained in quantitative yield with M_n value 12,600 and M_w value 28,300,respectively.DSC and TGA measurements show that the glass transition temperature（T_g） is 312℃ and 5%weight loss temperature is 434℃ in nitrogen and 545℃ in air,respectively.In addition,the novel polymer exhibits good solubility,which can be dissolved in common organic solvent at room temperature.

Polybenzimidazole functionalized electrolyte with Li-wetting and self-fluorination functionalities for practical Li metal batteries

Rough Li plating,low ionic conductivity,and low thermal stability of conventional electrolytes post-primary challenges for achieving reliable high-capacity rechargeable lithium batteries,for which lithiummetal is frequently proposed as themost promising anode material.Conventional low-polarity commercial polypropylene/polyethylene separators fail to support the application of high-energy-density Li anodes due to their rigid physicochemical properties and the high reactivity of Li metal,leading to fatal dendrite formation and vigorous exothermic reaction with electrolytes.Herein,we develop a Li-wetting,flame-retardant binary polymer electrolyte by functionalizing poly(vinylidene fluoride)(PVDF)separators with nonflammable polybenzimidazole(PBI)to build safe room-temperature solid-state electrolyte membranes.A dendrite-free LiFePO4 cell with the solid polymer electrolyte(SPE)delivers a discharge capacity of 127 mAh g^(-1) at 25℃ with a capacity retention of 87.5%after 500 cycles at 0.5℃(0.15 mA cm^(-2)).Phase-field simulations and density functional theory calculations demonstrate that the negatively charged benzimidazole chains of PBI own superior affinity to lithium bis(trifluoromethanesulfonyl)imide(LiTFSI),and shares overlapping electron density with Li anode,giving rise to accelerated Li^(+)conduction at room temperature and uniform Li electrodeposition at the electrolyte/Li metal interface.The SPE is also flame-retardant since heat-resistant polytetrafluoroethylene and a dense,heat-blocking graphitized carbon layer are formed in intense heat throughdehydrogenation/fluorination of PVDF under the catalysis of Lewis base imidazole rings and the decomposition of benzimidazole rings in PBI.No such fire-resistant mechanism is ever reported in conventional electrolytes.

High Strength and Stable Proton Exchange Membrane Based on Perfluorosulfonic Acid/Polybenzimidazole

In this work,a series of high strength,thermal stable and antioxidant proton exchange membranes were designed with solution processible polybenzimidazole(PBI)as the matrix and perfluorosulfonic acid(PFSA)as the fortifier for proton exchange.Solution processible PBI was successfully synthesized by introducing 4,4’-dicarboxydiphenyl ether into the molecular chains of PBI.PFSA/PBI composite membranes were obtained by solution blending and film casting.PBI and PFSA/PBI composite membranes exhibited greatly enhanced tensile strength and Young’s modulus compared to PFSA.PFSA/PBI composite membranes are stable below 300℃ which are suitable for practical application in proton exchange membrane fuel cells.The PFSA/PBI composite membranes show good dimensional stability with low water uptake and swelling rate.The PFSA/PBI composite membranes also exhibit excellent antioxidation stability with less than 5%initial mass loss over 120 h in Fenton reagent.The proton conductivity of PBI is greatly enhanced by blending with PFSA and the proton conductivities of the composite membranes are increased with the raise of PFSA content and temperature.This work offers valuable insights into the exploration of PBI based high-performance proton exchange membranes.

Polybenzimidazole(PBI)and benzimidazole-linked polymer(BILP)membranes

Polybenzimidazoles(PBIs)and benzimidazole-linked polymers(BILPs)have exceptional thermal and chemical stability,and hence,their membranes were developed and used under harsh conditions.In this review,the formation,structures,and properties of these polymers are studied follow by the fabrication of membranes.Applications,such as gas separation,organic solvent nanofiltration,water treatment,pervaporation and proton exchange,are extensively reviewed.The relationship of membrane performance and structure is established,highlighting the importance of processing protocols and post treatments.Future directions are provided on the basis of the conclusions.