Suppression mechanism of the self-discharge reaction in nickel-metal hydride batteries using a sulfonated polyolefin separator

The suppression mechanism of the self-discharge reaction in nickel-metal hydride batteries using a sulfonated polyolefin separator was investigated with sealed-type AA size cells. The experimental results indicate that a sulfonated polyolefin separator effectively suppresses the self-discharge reaction in nickel-metal hydride batteries by trapping nitrogen-containing redox shuttle substances. It is also found that a sulfonated polyolefin separator traps the shuttle substances as gaseous ammonia. In the experiment examining the influence of the amount of the shuttle substances on the self-discharge, the starting point of the self-discharge agreed well with the point at which the nitrogen adsorption capacity of a sulfonated polyolefin separator reached its maximum.     

锂离子电池用陶瓷聚烯烃复合隔膜

为改善聚烯烃微孔膜的耐热安全性,研究了用于锂离子电池的陶瓷聚烯烃复合隔膜ZrO2/SiO2/PP（聚丙烯）。 复合膜具有高度多孔性和良好液体电解液湿润性。 由于高的毛细吸附作用,通过吸附液态电解液,膜很易传导锂离子。 膜中ZrO2/SiO2的两性特征,将电解液中的酸性HF（氟化氢）消耗掉,而HF作为现在锂离子电池所用电解液中的杂质是不可避免的。 复合膜作为隔膜制备的碳/正极材料锂离子电池不仅具有优良的容量保持性、高温安全性,也显示良好的倍率放电性。     

聚烯烃锂离子电池隔膜的研究进展

随着信息技术时代的发展,锂离子电池被广泛应用,电池隔膜作为锂离子电池的重要组成部分越发引起大家的重视。聚烯烃锂离子电池隔膜由于其优异的机械性能和化学稳定性,以及相对廉价的特点,在锂离子电池发展初期就被研发应用,已成为锂离子电池隔膜的主流。本文综述了聚烯烃锂离子电池隔膜的制备方法,主要介绍了干法和湿法,及相关的产品。重点阐述了聚烯烃锂离子电池隔膜的性能需求和改性方法,主要包括隔膜的孔隙率、隔膜对电解液的亲和性以及热稳定性等方面。     

Sulfonated poly(phthalazinone ether sulfone) membrane as a separator of vanadium redox flow battery

To develop a novel and low-cost membrane as a separator of vanadium redox flow battery, sulfonated poly(phthalazinone ether sulfone) (SPPES) was prepared by sulfonating PPES with fuming sulfuric acid. By testing the sulfonation degree, intrinsic viscosity, and solubility of SPPES, the results showed that sulfonated polymers had higher intrinsic viscosities and excellent solubility in most polar solvents. IR analysis revealed that the –SO₃H group was successfully attached to SPPES backbone. DSC and TG results showed that SPPES exhibited higher T _g than that of PPES, and T _d at the first weight loss of SPPES was about 300?°C. The SPPES membrane (SP-02) showed a dramatic reduction in crossover of vanadium ions across the membrane compared with that of the Nafion membrane. Cell tests identified that VRB with the SPPES membrane exhibited a lower self-discharge rate, higher coulombic efficiency (92.82%), and higher energy efficiency (67.58%) compared with the Nafion system. Furthermore, cycling tests indicated that the single cell with SPPES membrane exhibited a stable performance during 100?cycles.     

锂离子电池凝胶聚合物隔膜的研究进展

作为锂离子电池重要组分,隔膜由多孔聚烯烃高分子材料组成;电解质体系由有机碳酸酯和六氟磷酸锂混合组成,虽具有高离子电导率,但因液态碳酸酯的易燃特性给锂离子电池带来了安全隐患。利用能够将液态电解质体系凝胶化的聚合物制备得到的凝胶聚合物隔膜,结合了液态电解质体系高电导率和固态电解质高安全性的优点。凝胶聚合物隔膜的研究从简单微孔凝胶聚合物隔膜开始,经历了引入少量纳米无机颗粒的掺杂凝胶聚合物隔膜,到引入大量纳米颗粒的凝胶陶瓷隔膜的发展历程。本文详细介绍这三种类型凝胶聚合物隔膜的物理化学特性,最后展望凝胶聚合物隔膜的发展趋势。     

Recent Development of Polyolefin‐Based Microporous Separators for Li−Ion Batteries: A Review

Secondary Li?ion batteries have been paid attention to wide‐range applications of power source for the portable electronics, electric vehicle, and electric storage reservoir. Generally, lithium‐ion batteries are comprised of four components including anode, cathode, electrolyte and separator. Although separators do not take part in the electrochemical reactions in a lithium‐ion (Li?ion) battery, they conduct the critical functions of physically separating the positive and negative electrodes to prevent electrical short circuit while permitting the free flow of lithium ions through the liquid electrolyte that fill in their open porous structure. Hence, the separator is directly related to the safety and the power performance of the battery. Among a number of separators developed thus far, polyethylene (PE) and polypropylene (PP) porous membrane separators have been the most dominant ones for commercial Li?ion batteries over the decades because of their superior properties such as cost‐efficiency, good mechanical strength and pore structure, electrochemical stability, and thermal shutdown properties. However, there are main issues for vehicular storage, such as nonpolarity, low surface energy and poor thermal stability, although the polyolefin separators have proven dependable in portable applications. Hence, in this review, we decide to provide an overview of the types of polyolefin microporous separators utilized in Li?ion batteries and the methods employed to modify their surface in detail. The remarkable results demonstrate that extraordinary properties can be exhibited by mono‐ and multilayer polyolefin separators if they are modified using suitable methods and materials.     

A membrane based on sulfonated polystyrene for a vanadium solid-salt battery

An ion exchange membrane (IEM) usually serves as a separator between the two half-cells and provides an ionic conduction path in redox flow batteries. The new vanadium solid-salt battery (VSSB) presents higher energy density than the traditional vanadium redox flow batteries (VRFBs). However, present IEMs are based on very expensive Nafion® membranes. In pursuit of lower cost, a membrane from sulfonated polystyrene (PE-01) is used for VSSB. In comparison with the traditional Nafion® 1135, PE-01 shows high energy efficiency with good cycling performance at current densities less than 10 mA cm^?2. This suggests that sulfonated polystyrene membrane is a promising candidate as separator for VSSB.     

Self-discharge in positively charged polypyrrole–cellulose composite electrodes

Self-discharge is one of the most critical issues to address to allow for industrialization of conducting polymer (CP) based electric energy storage devices. The present work investigates the underlying cause of self-discharge in positively charged polypyrrole (PPy), which is one of the most frequently studied CPs for such devices. The analyzed material is a composite of PPy and cellulose from Cladophora sp. algae forming a free standing paper-like material. From the time dependence of the potential decay as well as from independent spectroelectrochemical investigations the decay was attributed to a kinetically limiting Faradaic reaction, intrinsic to the polymer, forming a reactive intermediate that irreversibly reacts with its surroundings in a kinetically non-limiting following reaction. As such, nucleophilic addition of electrolyte nucleophiles is not found to be rate-determining. These results provide insight into the self-discharge phenomenon in p-doped CPs, and information regarding the potential range in which CPs can operate with insignificant self-discharge.     

Talcum-doped composite separator with superior wettability and heatproof properties for high-rate lithium metal batteries

Separator is supposed to own outstanding thermal stability, superior wettability and electrolyte uptake,which is essential for developing high-rate and safe lithium metal batteries(LMBs). However, commercial polyolefin separators possess poor wettability and limited electrolyte uptake. For addressing this issue, we put forward a composite separator to implement above functions by doping layered-silicate(talcum) into polyvinylidene fluoride(PVDF). With significant improvement of electrolyte absor...     

Preparation and Properties of Poly（ether ether ketone）/Carbon Nanotube Modified Polypropylene Janus Composite Separator北大核心CSCD

Lithium-ion batteries （LIBs）have attracted wide attention because of their broad prospects in electric vehicles. However,the safety problems and low multiplier performance of the commercial polyolefin separator limit their further development,due to the poor dimensional thermal stability and low electrolyte absorption rate. Poly（ether ether ketone）（PEEK）and carbon nanotube（CNT）are compounded to coat on polypropylene （PP） to prepare Janus composite separator （PP@C） through the phase inversion method. PP@C composite separator does not deform at 180 ℃ for 0. 5 h（only slight deformation）,illustrating excellent thermal stability. The electrolyte absorption rate of PP@C2 is 193. 8%. The electrolyte uptake rate of the PP@C2 composite membrane was 193. 8%,which was 64. 5% higher than the PP membrane,showing a superduper electrolyte permeability. As a result,the specific discharge capacity of LIBs assembled with PP@C2 composite separator is 157. 6 mA·h/g at 0. 2 C and 129. 8 mA·h/g at 2 C,showing good rate performance with the capacity recovery rate of more than 99%. This might be attributed to the ultra-high thermal stability of PEEK,the good affinity of the electrolyte,the high conductivity of CNT,as well as the uniform dispersion of Li+ ,so that the separator can have excellent electrochemical performance while improving safety. © 2022, Science Press (China). All rights reserved.     

氧化还原电池组等效电路模型

本文综合考虑氧化还原二次电池内部的电化学反应和电池组漏电电流,建立了氧化还原电池组的等效电路模型. 以1 kW额定输出功率的全钒液流储能电池组为例,测试电池组暂态响应和自放电曲线,确定了等效电路模型的重要参数,比较模拟结果与实验结果,计算电池组的内阻和自放电电流,可知漏电电流造成的容量损失约占系统总容量损失的60%左右.     

Heterogeneous fluorine-containing surface macro-, micro- and nanostructures in polymer films and their applications

The methods of heterogeneous macro-, micro- and nanostructure formation on the surfaces of polymer films via their modification with gaseous fluorine have been considered. The successive fluorination and sulfonation of polyolefin films allows the synthesis of heterounit bi- and polyfunctional molecular fragments, thereby providing controlled chemical structuring at the nanolevel within a macromolecular segment. The combined use of the above methods of polymer-surface modification and intermediate film deformation under uniaxial tension results in the formation of surface microzones with fluorinated and sulfonated structures. Fluorinated and sulfonated macro- and microzones are formed via mechanical fracture of the fluorinated layer before sulfonation or via shielding of the polymer surface before sulfonation according to a given pattern through photolithographic methods. The practical applications of polymer films with heterogeneous surface structures are discussed.     

高分子共混物中Friedel-Crafts烷基化反应原位增容与催化降解机理

采用GPC方法对共混组分的分子量、接枝率和降解度等数据进行分析, 发现AlCl₃催化剂对PS/POE共混物的作用表现在原位增容和催化降解两个方面. 结合Friedel-Crafts烷基化反应的特点细化反应过程, 发现PS/POE共混物在AlCl₃作用下发生接枝反应时, 有大量碳正离子出现, 而碳正离子周围的电子重排会导致分子链断裂, 从而引起共混组分出现大幅度降解. PS/POE/AlCl₃共混物中原位接枝与催化降解是一对竞争性反应, 同时存在, 并相互竞争.     

Metal catalysis to improve compatibility at PO/PET blends interfaces

Reactive blending of 70/30 by weight PET/polyolefin (PO) mixtures was carried out in a discontinuous mixer using a polyolefin functionalized with dialkyl maleates and potential transesterification catalysts to improve the formation of graft PO-PET copolymers. The yield of this reaction was evaluated by the analysis of FT-IR spectra of blends residual fraction after selective extractions of unreacted polyester. The building of a calibration curve and the analysis of the spectra by deconvolution was performed to evaluate the percentage of grafted PET. The results are discussed in terms of influence of the different catalysts and of polyolefin structure on the blends morphology.     

A redox‐active polythiophene‐modified separator for safety control of lithium‐ion batteries

A potential‐sensitive separator is prepared simply by incorporating a redox‐active poly(3‐butylthiophene) (P3BT) into the micropores of a commercial porous polyolefin film and tested for overcharge protection of LiFePO₄/Li₄Ti₅O₁₂ lithium‐ion batteries. The experimental results demonstrate that owing to the reversible p‐doping and dedoping of the redox‐active P3BT polymer embedded in the separator with the changes of the cathode potential from an overcharge state to a normal operating state, this type of separator can reversibly switch between electronically insulating state and conductive state to maintain the charge voltage of LiFePO₄/Li₄Ti₅O₁₂ cells at a safety value of ≤2.4 V, and thus protecting the cell from voltage runaway. As this type of the separators works reversibly and has no negative impact on the battery performances, it can be used as an internal and self‐protecting mechanism for commercial lithium‐ion batteries and other rechargeable batteries. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1487–1493     

Polymer/colloid dual-phase electrolyte membrane for rechargeable lithium batteries

In this work, a polymer/ceramic phase-separation porous membrane is first prepared from polyvinyl alcohol–polyacrylonitrile water emulsion mixed with fumed nano-SiO₂ particles by the phase inversion method. This porous membrane is then wetted by a non-aqueous Li–salt liquid electrolyte to form the polymer/colloid dual-phase electrolyte membrane. Compared to the liquid electrolyte in conventional polyolefin separator, the obtained electrolyte membrane has superior properties in high ionic conductivity (1.9 mS?cm^?1 at 30 °C), high Li⁺ transference number (0.41), high electrochemical stability (extended up to 5.0 V versus Li⁺/Li on stainless steel electrode), and good interfacial stability with lithium metal. The test cell of Li/LiCoO₂ with the electrolyte membrane as separator also shows high-rate capability and excellent cycle performance. The polymer/colloid dual-phase electrolyte membrane shows promise for application in rechargeable lithium batteries.     

球形氯化镁载体与四氯化钛反应的载钛过程研究

球形氯化镁载体型齐格勒-纳塔催化剂是目前常用的工业聚烯烃催化剂,由于制备工艺对催化剂性能影响很大,因此对此类催化剂制备过程的研究具有重要意义。本文利用自制球形氯化镁载体与四氯化钛反应制备球形聚烯烃催化剂,分析了载钛反应过程的中间产物。对球形氯化镁载体载钛过程中钛含量、比表面、比孔容、晶型等发生的变化进行分析,并研究了邻苯二甲酸二丁酯作为内给电子体在球形氯化镁载体载钛过程中的作用,为球形氯化镁载体型催化剂制备工艺的改进提供了重要参考依据。     

Comparison of redox initiated graft polymerisation and sulfonation for hydrophilisation of polyethersulfone nanofiltration membranes

Three polyethersulfone nanofiltration membranes, including two commercial membranes (NFPES10 and N30F) and one lab-made membrane (N71), were hydrophilised in view of an increased water flux and a reduction of membrane fouling.Non-modified as well as modified membranes were characterized using contact angle measurements, water fluxes and retention of sugars.At first, redox initiated graft polymerization was applied, and the influence of reaction time, initiator concentration and monomer concentration were investigated. It was observed that grafting always resulted in a significant reduction of the contact angle. The higher the reaction time, the lower was the contact angle, but the initiator and monomer concentration had no effect when above a threshold value. Grafting results in a decrease of the water flux, while the retention of raffinose increased.A comparison was made with the addition of sulfonated polyethersulfone to the polymer solution. By blending polyethersulfone and sulfonated polyethersulfon, a sufficiently high viscosity could be achieved. The influence of the blending ratio was investigated. The larger the fraction of sulfonated polyethersulfon, the more hydrophilic the membrane became. The addition of sulfonated polyethersulfon, however, has also an influence on the water flux and on the retention of sugars. An important conclusion is also that the membranes containing sulfonated polyethersulfone are significantly more hydrophilic than the ones that have been modified through the grafting technique.     

Pervaporation separation of water/ethanol mixture by sulfonated polysulfone membrane

For dehydrating a water/ethanol mixture by pervaporation, a sulfonated polysulfone membrane was prepared. The separation performance of water and ethanol are shown to strongly depend on the degree of substitution of polysulfone membrane. The degree of substitution increased with increasing chlorosulfonic acid in the casting solution, and the substitution reaction was achieved within 2 h. The water permeation rate and separation factor increased with increasing substitution of polysulfone membrane up to a substitution of 2.0. The effect of sulfonation on separation performance was due to the improvement of hydrophilicity of sulfonated membrane. It was found that the solubility of water/ethanol in the membrane was not the dominant factor for separation but it was rather the diffusion difference in the membrane. The diffusion difference between permeate through sulfonated membrane was the dominant factor for separating the water/ethanol mixture. The high performance of pervaporation membrane can be prepared by sulfonated polysulfone.     

Improvement of thermal stability of sulfonated polyphosphazenes by introducing a self‐crosslinkable group

We prepared sulfonated polyphosphazenes having various aryloxy substituents, and studied their thermal stabilities and membrane properties. Sulfonated polyphosphazenes were synthesized by the reaction of polydichlorophosphazene with sodium aryloxides and subsequent sulfonation with fuming sulfuric acid. With increasing the degree of sulfonation, the polymers showed higher proton conductivity, but suffered more from swelling in an aqueous solution. We introduced a hydroxymethylphenoxy group onto the phosphazene backbone as a self‐crosslinkable group by reaction of poly(dichlorophosphazene) and a sodium salt of 4‐hydroxymethylphenol. When a film of a sulfonated polymer having a methylol group was heated at 80 °C under vacuum for 1 h, it became insoluble in NMP, indicating the formation of a network structure. We investigated the crosslinking reaction of the polymers by DSC and FTIR. The crosslinking reaction proceeded only in the sulfonated polymers. Because the sulfonated polymers provide acidic protons, the methylol groups became more electrophilic and reacted with neighboring aromatic rings. A condensation reaction between themselves could also occur. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5850–5858, 2008