Influence of cellulose gel matrix on BMIMCl ionic liquid dynamics and conductivity

Fast field-recycling magnetic resonance relaxometry (FFC NMR) was applied to measure the spin-lattice relaxation time, T ₁, of protons in pure ionic liquid (IL) 1-butyl-3-methylimidazolium chloride (BMIMCl) and when confined in cellulose (Cell) ion gel (Cell/BMIMCl) at different temperatures and different Larmor frequencies. The rotational and translational contributions were taken to interpret the relaxation data of neat BMIMCl and were described by Woessner’s and Torrey’s theoretical models, respectively. The ionic liquid–cellulose matrix interaction detected in 10 wt% polymer-ion gel was interpreted on the basis of a dynamical process called reorientation mediated by translational displacements (RMTD), which allow explanation of the significant slowing of the dynamics of IL cations at cellulose surfaces. Two types of cation diffusion were identified in this gel: a long-range translational diffusion within large cavities of the Cell matrix and diffusion occurring at the polymer surface. The correlational time constants and self-diffusion coefficients of the BMIMCl ionic liquid in bulk-like state and interaction with the cellulose matrix surface were determined. The conductivity measurements performed for pure IL and that confined in the Cell/BMIMCl ion gel show that the gelation only results in a small decrease of the ionic conductivity.     

Self-diffusion of lithium cations and ionic conductivity in polymer electrolytes based on polyesterdiacrylate

The processes of ionic conductivity are studied in a polymer gel electrolyte synthesized based on polyesterdiacrylate and a low-molecular solvent ethylene carbonate. The self-diffusion coefficients of solvent molecules and Li⁺ cations are measured by the NMR with the pulsed magnetic field gradient. The Li⁺ self-diffusion coefficients increase with the increase in the solvent content and are independent of the diffusion time in the interval from 10 to 1600 ms. The latter values imply the absence of limitations for the translational mobility of lithium ions in the spatial range from 10⁻⁷ to 10⁻⁵ m. Based on the Nernst-Einstein equation, the ionic conductivities are calculated and compared with the experimental conductivities measured by the impedance method. These values coincide for high contents of solvent; for low ethylene carbonate concentrations, the calculated conductivities much exceed the experimental values.     

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。     

Effect of solvents on properties of polymer gel-electrolyte based on polyester diacrylate

New polymer gel electrolytes based on polyester diacrylates and LiClO₄ salt solutions in organic solvents are developed for lithium ion and lithium polymer batteries with a high ionic conductivity up to 2.7 × 10^?3 Ohm^?1cm^?1 at the room temperature. To choose the optimum liquid electrolyte composition, the dependence is studied of physico-chemical parameters of new gel electrolytes on the composition of the mixture of aprotic organic solvents: ethylene carbonate, propylene carbonate, and λ-butyrolacton. The bulk conductivity of gel electrolytes and exchange currents at the gel electrolyte/Li interface are studied using the electrochemical impedance method in symmetrical cells with two Li electrodes. The glass transition temperature and gel homogeneity are determined using the method of differential scanning calorimetry. It is found that the optimum mixture is that of propylene carbonate and λ-butyrolacton, in which a homogeneous polymer gel is formed in a wide temperature range of ?150 to +50°C.     

离子液体凝胶聚合物电解质的三元组分相互作用研究

采用Raman光谱、傅里叶转换红外光谱和X-射线衍射光谱研究N-甲基-N-丙基哌啶双三氟甲磺酸亚胺离子液体（PP13TFSI）和双三氟甲磺酸亚胺锂盐（LiTFSI）对PVDF-HFP聚合物聚合方式的影响,结果表明,PP13TFSI、LiTFSI和PVDF-HFP是共混存在的,同时加入PP13TFSI和LiTFSI会使聚合物的聚合方式由晶体结构转变为无定形结构. 通过对电解质及其各组分的线性扫描伏安曲线和热重曲线分析可知,溶剂N-甲基吡咯烷酮（NMP）容易残留在凝胶聚合物电解质（ILGPE）中,这会降低ILGPE的电化学稳定性和热稳定性. 作者对固态LiFePO₄|ILGPE|Li电池的倍率性能进行了研究,实验结果表明其具有较好的倍率性能,当电池倍率由C/10增大至2C,然后再回到C/10时,其容量可以恢复到原来的90.9%左右. 该研究结果对理解PP13TFSI和LiTFSI在ILGPE中的作用机理具有重要的意义.     

A novel process to prepare porous membranes comprising SnO2 nanoparticles and P(MMA-AN) as polymer electrolyte

We have successfully developed a new process to prepare porous poly(methyl methacrylate-co-acrylonitrile) (P(MMA-AN)) copolymer based gel electrolyte. The porous structure in the polymer matrix is achieved by adding SnO₂ nanoparticles which are mostly used as gas sensor materials. The quasi-aromatic solvent, NMP, has an electron-repulsion effect with the space charge layer on the surface of SnO₂ nanoparticles and forms a special gas–liquid phase interface. Once the cast polymer solution is stored at an elevated temperature to evaporate the solvent, gas–liquid phase separation happens and spherical pores are obtained. The ionic conductivity at room temperature of the prepared gel polymer electrolyte based on the porous membrane is as high as 1.54 × 10⁻³ S cm⁻¹ with the electrochemical stability up to 5.10 V (vs. Li/Li⁺). This method presents another promising way to prepare porous polymer electrolyte for practical use.     

聚乙烯吡咯烷酮基碘凝胶电解质的制备及在染料敏化太阳能电池中的应用

采用聚乙烯吡咯烷酮(PVP)和聚偏氟乙烯(PVDF)为凝胶剂, 以碘化锂和碘单质为碘源, 碳酸乙烯酯(EC)和碳酸丙烯酯(PC)为溶剂, 制备了染料敏化太阳能电池(DSSCs)用凝胶聚合物电解质(GPE). 使用拉曼光谱、 循环伏安曲线和交流阻抗谱等对GPE进行表征. 结果表明, 聚合物的配比与浓度及碘与碘化锂比例对该电解质性能有很大影响, 当聚合物质量分数为10%、 PVP与PVDF质量比为80∶20、 I₂浓度为0.042 mol/L且LiI与I₂摩尔比为30∶1时, 制备的GPE在室温下电导率达最大值(3.27 mS/cm). 使用该GPE组装的DSSCs在100 mW/cm²的模拟太阳光照射下, 开路电压为0.64 V, 短路电流为13.6 mA/cm², 填充因子为0.595, 能量转化效率为5.18%, 并在30 d内表现出了良好的稳定工作性能.     

Preparation of a novel polymer gel electrolyte based on N-methyl-quinoline iodide and its application in quasi-solid-state dye-sensitized solar cell

Using poly(acrylonitrile-co-styrene) as polymer host, 1,2-propanediol carbonate, dimethyl carbonate and ethylene carbonate as mixture solvent, N-methyl-quinoline iodide and iodine as the source of I⁻/I₃ ⁻, a novel polymer gel electrolyte with ionic conductivity of 5.12 × 10⁻³ S· cm⁻¹ at 25°C was prepared by sol-gel and hydrothermal methods. Based on the polymer gel electrolyte, a quasi-solid-state dye-sensitized solar cell was fabricated. The solar cell possess better long-term stability and light-to-electrical energy conversion efficiency of 4.04% under irradiation of 100 mW· cm⁻². The influences of polymer host, solvent, N-methyl-quinoline iodide and temperature on ionic conductivity of the polymer gel electrolyte and the performance of the dye-sensitized solar cell was discussed.     

Study of the role of ceramic filler in composite gel electrolytes based on microporous polymer membranes

The presented contribution aims at reconsidering the role of filler in affecting the ionic transport in composite gel electrolytes for Li-ion cells based on microporous polymer membranes. The gels have been prepared by swelling thin PVdF/HFP membranes either with conventional liquid electrolyte or with pure propylene carbonate solvent. The membranes contained dispersed submicron-size modified silica filler added in a wide range of weight ratios. The effect of filler content on the kinetics of liquid phase absorption and evaporation from the composite membranes, as well as on the conductivity of the corresponding gel electrolytes, has been studied and discussed in terms of the “colloidal” and “soggy sand” electrolyte concepts. It has been found that conductivity increase of composite gels is not directly correlated with the liquid electrolyte uptake. On this basis it is concluded that important part of ionic transport in this type of composite gel polymer electrolytes is realized on the filler grain boundaries, through overlapping space charge layers of the silica grains.     

含氟聚合物杂化电解质膜的结构分析

聚偏氟乙烯;共聚物;微孔膜;离子电导率;含氟聚合物杂化电解质膜的结构分析     

Lithium ion conduction and ion-polymer interaction in poly（vinyl pyrrolidone） based electrolytes blended with different plasticizers

Poly（ethylene oxide）, poly（vinyl pyrrolidone）（PEO/PVP）, lithium perchlorate salt（Li Cl O4） and different plasticizer based, gel polymer electrolytes were prepared by the solvent casting technique. XRD results show that the crystallinity decreases with the addition of different plasticizers. Consequently, there is an enhancement in the amorphousity of the samples responsible for the process of ion transport. FTIR spectroscopy is used to characterize the structure of the polymer and confirms the complexation of plasticizer with host polymer matrix. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. Among the various plasticizers, the ethylene carbonate（EC） based complex exhibits a maximum ionic conductivity value of the order of2.7279 10 4S cm 1. Thermal stability of the prepared electrolyte films shows that they can be used in batteries at elevated temperatures. PEO（72%）/PVP（8%）/Li Cl O4（8%）/EC（12%） has the maximum ionic conductivity value which is supported by the lowest optical band gap and lowest intensity in photoluminescence spectroscopy near 400–450 nm. Two and three dimensional topographic images of the sample having a maximum ionic conductivity show the presence of micropores.     

Computer simulation of dissociative equilibrium in aqueous NaCl electrolyte with account for polarization and ion recharging. Ionization mechanism

The Monte Carlo method in a system with periodic boundary conditions was used within the model with explicit account for many-bod interactions to calculate ion-water correlation functions and the mean force ion-ion potential for extremely dilute aqueous electrolyte. Many-body interactions result in a decrease in the first coordination number of ions by approximately one molecule. The same effect is observed in the case of hydration in water vapors. Partial displacement of molecules from the lower layer into the higher hydrate layers occurs mainly by means of interactions of dipoles induced on molecules. Many-body interactions enhance the stability of unrecombined ion pairs separated by solvent molecules (SSIP states). The depth of the minimum in the dependence of the ion-ion mean force potential with account for many-body interaction forces is several times higher than in primitive interaction models. The value of effective relative dielectric permeability of the solvent at short distances from the ions grows faster than 1/R. Due to solvent polarization, counterions are strongly repelled at distances corresponding to overlapping of their hydrate shells and are weakly attracted at large distances. Stability of ion pair SSIP states in liquid electrolyte is due to rearrangement of the molecular structure of the solvent in the interion space and is an entropy effect. This mechanism differs qualitatively from that observed under hydration in water vapor and the depth of the minimum corresponding to SSIP states is by an order of magnitude lower in liquid electrolyte as compared to that in saturated water vapor.     

Electrochemical Systems Based on Sol-Gel Silica Matrix Impregnated with Organic Solvent

Two electrochemical systems based on sol-gel silica matrix impregnated with organic solvent were prepared and studied. The first one is composed of tetramethylorthosilicate based material filled with ferrocene solution in polar solvent: propylene carbonate. Electrodes are immersed in this solid electrolyte during all stages of sol-gel process. Despite of the lack of the extra added salt, by using ultramicroelectrode, undistorted electrochemical signal corresponding to the electrooxidation of the ferrocene was obtained. Its diffusion coefficient within the sol-gel matrix depends on the time elapsed after gelation and it is not much below that in salt solution in the same solvent. The second system is based on graphite dispersion in hydrophobic sol-gel silicate matrix. This material was filled with mixture of liquid butylferrocene and hexadecane. After immersion in aqueous salt solution it serves as working electrode. The electrochemical signal corresponding to the electrooxidation of the butylferrocene within organic phase was obtained. Probably the electrode process occurs at three phase (carbon/organic phase/aqueous phase) junction and it is accompanied by anion transfer through the liquid-liquid interface.     

热塑性聚氨酯基聚合物电解质的制备与表征

采用非溶剂诱导相转化法（NIPS）制备了热塑性聚氨酯/醋酸纤维素（TPU/CA）新型聚合物隔膜。然后,将隔膜浸入液体电解质中得到TPU/CA凝胶聚合物电解质（GPEs）。研究TPU与CA的质量比对GPEs性能的影响。通过X射线衍射（XRD）、扫描电镜（SEM）、热重（TG）、差示扫描量热（DSC）、线性扫描伏安（LSV）、电化学阻抗（EIS）等对TPU/CA膜进行表征。结果表明,在共混隔膜中引入CA可以降低TPU的结晶度,增加隔膜的吸液率。其中,室温下TPU/CA = 7/3基电解质的离子电导率为1.04 mS·cm^-1,电化学窗口为5.1 V(vs. Li/Li⁺)。组装的电池LiFePO₄/TPU/CA/Li在0.5 C循环100次后,仍具有较高的放电比容量和较好的容量保持率,具有良好的循环稳定性。这些结果表明,这种新型的TPU/CA共混GPEs是锂离子电池的理想选择。     

Composite gel membranes: a new class of improved polymer electrolytes for lithium batteries

Novel composite, gel-type polymer electrolytes have been prepared by dispersing selected ceramic powders into a matrix formed by a lithium salt solution contained in a poly(acrylonitrile) (PAN) network. The electrochemical characterization demonstrates that these new types of composite gel electrolytes have high ionic conductivity, wide electrochemical stability and, particularly, high chemical integrity (no liquid leakage) even at temperatures above ambient. These unique properties make the composite gel membranes particularly suitable as electrolyte separators in lithium ion polymer batteries.     

凝胶型聚合物电解质的电导率与温度的关系

凝胶型聚合物电解质的电导率与温度的关系孙晓光，林云青，齐力，景遐斌，王佛松（中国科学院长春应用化学研究所长春１３００２２）关键词凝胶电解质，离子电导率，活化能无定形聚合物电解质电导与温度的依赖关系一般可用Ｖｏｇｅｌ－Ｔａｍｍａｎ－Ｆｕｌｃｈｅｒｃ（Ｖ...     

P(VdF-HFP)-基离子液体复合聚合物电解质的阴极稳定性及热稳定性

以聚偏氟乙烯-六氟丙烯P(VdF-HFP)聚合物为基体, 制备了含离子液体1-甲基-3-乙基咪唑六氟磷酸盐(EMIPF6)、用于锂离子电池的离子液体复合聚合物电解质[P(VdF-HFP)/LiPF₆/EMIPF₆/EC(碳酸乙烯酯)-PC(碳酸丙烯酯)]. 采用热重分析法以及燃烧实验测试了复合聚合物电解质的热稳定性. 离子电导率测试表明, 离子液体的存在显著改善了复合聚合物电解质的离子传输; 循环伏安测试表明, 添加剂EC和PC的加入提高了复合电解质的阴极稳定性, 制得的离子液体复合聚合物电解质在0.3-4.3 V 电压范围内稳定存在. Li₄Ti₅O₁₂ 和LiCoO₂为电极材料、P(VdF-HFP)/LiPF₆/EMIPF₆/EC-PC 为电解质的半电池表现出优良的循环性能, 0.1C充放电倍率下, Li/LiCoO₂和Li/Li₄Ti₅O₁₂半电池的可逆容量分别为130和144 mAh·g^-1. 但EC、PC在一定程度上降低了离子液体复合聚合物电解质的热稳定性.     

一种新型聚合物电解质的研制

合成了聚 (甲基丙烯酸甲酯 丙烯腈 甲基丙烯酸锂 ) (简记为PMAML)新型聚合物电解质基质材料 ,把它与聚偏氟乙烯 (PVDF)共混制备了凝胶化的聚合物电解质 .通过核磁共振波谱确定了PMAML的组份含量 ,并用扫描电镜观察了该聚合物基质膜的表面形貌 .利用交流阻抗技术测试了其电导率 ,室温下电导率可达2 5× 10 - 3S·cm- 1 .采用线性伏安扫描方法研究了该聚合物电解质的电化学稳定性 ,其电化学稳定窗口为4 5V .通过受限扩散实验测得电解质中离子的扩散系数为 8 12× 10 - 7cm2 ·s- 1 .组装的聚合物电解质锂离子电池首次充放电效率为 89% ,前 5次循环容量基本稳定 .     

塑料化薄膜锂离子电池的制造技术

通过比较不同聚合物骨架材料与增塑剂所制备的聚合物膜的性能 ,优选出合适的基质骨架材料和增塑剂 .在此基础上 ,探索了塑料化聚合物薄膜电极的工业化制造方法 ,优化了聚合物电解质隔膜与正负极极片的配比 ,探讨塑料化薄膜电极的复合方式 ,并对所制备的塑料化薄膜锂离子电池电性能进行了考察 ,结果表明 :薄膜塑料锂离子电池具备与液态锂离子电池相近的电化学性能 .     

New lithium-conducting gel electrolytes containing superbranched polymers

New polymer gel electrolytes containing superbranched polymers were developed. The gel electrolyte containing 20 wt % superbranched polymer, 6 wt % methylmethacrylate, 4 wt % triethyleneglycol dimethacrylate, and 70 wt % 1 M propylene carbonate solution of LiClO₄ was found to have a maximum conductivity of ～9 × 10^?4 S/cm at room temperature and an effective activation energy of conductivity of 18 kJ/mol. The physicochemical properties of the gel electrolyte were correlated with its composition using electrochemical impedance spectroscopy, thermomechanics, and differential scanning calorimetry. The glass-transition temperature of these electrolytes depended only on the liquid electrolyte content and decreased from ?80 to ?93°C when the concentration of 1 M LiClO₄/PC increased from 60 to 80 wt %. As the content of the superbranched polymer increased from 0 to 20 wt % at positive temperatures, the modulus of elasticity decreased, while the conductivity increased. When the content of the superbranched polymer increased at the expense of the liquid electrolyte, the conductivity of the system decreased.