Improving electrochemical performance of poly(vinyl butyral)-based electrolyte by reinforcement with network of ceramic nanofillers

This study has concerned the development of polymer composite electrolytes based on poly(vinyl butyral) (PVB) reinforced with calcinated Li/titania (CLT) for use as an electrolyte in electrochemical devices. The primary aim of this work was to verify our concept of applying CLT-based fillers in a form of nano-backbone to enhance the performance of a solid electrolyte system. To introduce the network of CLT into the PVB matrix, gelatin was used as a sacrificial polymer matrix for the implementation of in situ sol–gel reactions. The gelatin/Li/titania nanofiber films with various lithium perchlorate (LiClO₄) and titanium isopropoxide proportions were initially fabricated via electrospinning, and ionic conductivities of electrospun nanofibers were then examined at 25 °C. In this regard, the highest ionic conductivity of 2.55 × 10⁻⁶ S/cm was achieved when 10 wt% and 7.5 wt% loadings of LiClO₄ and titania precursor were used, respectively. The nanofiber film was then calcined at 400 °C to remove gelatin, and the obtained CLT film was then re-dispersed in solvated PVB-lithium bis(trifluoromethanesulfonyl)imide (PVB-LiTFSI) solution before casting to obtain reinforced composite solid electrolyte film. The reinforced composite PVB polymer electrolyte film shows high ionic conductivity of 2.22 × 10⁻⁴ S/cm with a wider electrochemical stability window in comparison to the one without nanofillers.

     

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.     

用于锂离子电池的新型超支化聚醚-聚氨酯聚合物电解质

采用溶剂聚合法, 将一种自制新型超支化聚醚(PHEMO)与异氰酸酯在电解液中进行缩合反应, 生成了一种包含有电解液的新型超支化聚醚聚氨酯(PHEU)聚合物电解质. 利用傅里叶红外光谱(FTIR)、示差扫描量热分析(DSC)、热重分析(TGA)和交流阻抗谱等测试方法对PHEU的结构、热稳定性能和离子电导率进行了研究. 研究结果表明, 当电解液中锂盐的浓度为3 mol/L, 电解液的质量为骨架材料质量加和的3倍时, 电解质体系的室温电导率可达到6.12×10-4 S/cm; 电化学稳定窗口为2.2—4.0 V, 具有良好的热稳定性和优良的机械性能. 另外, 在这种新型的电解质中, 聚氨酯大分子将电解液小分子牢固地包裹在里面, 有效地防止了凝胶聚合物电解质的漏液问题, 从而可以提高电池的安全性能.     

多嵌段聚醚氨酯脲为基质的新型高分子固态离子导体

本文合成了一系列聚乙二醇型多嵌段聚醚氨酯脲，而且用这类聚醚氨酯甩与高氯酸锂制得了一种新型的高分子固态离子导体复合物。在室温和50℃之间，其电导率比聚环氧乙烷为基质的固体电解质的高一到二个数量级，它还具有优良的综合性能。因此，对于室温薄膜蓄电池来说，这种新型的固体电解质是一类良好的候选材料。     

Polymer electrolytes based on acrylonitrile-butadiene-styrene copolymer

One of the approaches to improving the ionic conductivity and the mechanical strength of a solid polymer electrolyte is to use polymers in modified forms, such as polymer blends, copolymers and cross-linked polymers. In this study, a new polymer electrolyte based on the acrylonitrile-butadiene-styrene (ABS) copolymer has been prepared. The ionic conductivity, electrochemical stability and interfacial characteristics of the polymer electrolyte in contact with a lithium electrode have been investigated. The temperature dependence of the conductivity below 20 °C can be described by the Arrhenius equation, and above 20 °C by the VTF equation. Lithium passivation appeared to have taken place in the system. The conductivity and electrochemical characteristics of the system are somewhat similar to those of PAN-based polymer electrolytes. Received: 9 December 1998 / Accepted: 9 March 1999     

基于一体化正极与电解质膜的高性能固态电池

Lithium ion batteries (LIBs) are becoming the most popular energy storage systems in our society. However, frequently occurring accidents of electrical cars powered by LIBs have caused increased safety concern regarding LIBs. Solid-state lithium batteries (SSLBs) are believed to be the most promising next generation energy storage system due to their better in-built safety mechanisms than LIBs using flammable organic liquid electrolyte. However, constructing the ionic conducting path in SSLBs is challenging due to the slow ionic diffusion of Li ion in solid-state electrolyte, particularly in the case of solid-solid contact between the solid materials. In this paper, we demonstrate the construction of an integrated electrolyte and cathode for use in SSLBs. An integrated electrolyte and cathode membrane is obtained via simultaneous electrospinning and electrospraying of a polyacrylonitrile (PAN) electrolyte and a LiFePO₄ (LFP) cathode material respectively, for the cathode layer, followed by the electrospinning of PAN to prepare the electrolyte layer. The resultant integrated PAN-LFP membrane is flexible. Scanning electron microscopy and energy dispersive X-ray spectroscopy measurement results show that the electrode and electrolyte are in close contact with each other. After the integrated PAN-LFP membrane is filled with a succinonitrile-bistrifluoromethanesulfonimide (SN-LiTFSI) salt mixture, it is paired with a lithium foil metal anode electrode, and the resultant solid-state Li|PAN-LFP cell exhibits limited polarization and outstanding interfacial stability during long term cycling. That is, the Li|PAN-LFP cell presents a specific capacity of 160.8 mAh∙g⁻¹ at 0.1C, and 81% of the initial capacity is maintained after 500 cycles at 0.2C. The solid-state Li|PAN-LFP cell also exhibits excellent resilience in destructive tests such as cell bending and cutting.     

离子导电聚合物电解质的研究*

本文对离子导电聚合物电解质的发展史、分类、导电机理、研究方法及离子导电聚合物电解质电导率提高的途径进行了综述分析,并讨论了今后工作的发展方向。     

High ionic conductivity P(VDF-TrFE)/PEO blended polymer electrolytes for solid electrochromic devices

Solid polymer electrolytes with excellent ionic conductivity (above 10(-4) S cm(-1)), which result in high optical modulation for solid electrochromic (EC) devices are presented. The combination of a polar host matrix poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) and a solid plasticized of a low molecular weight poly(ethylene oxide) (PEO) (M(w)≤ 20,000) blended polymer electrolyte serves to enhance both the dissolution of lithium salt and the ionic transport. Calorimetric measurement shows a reduced crystallization due to a better intermixing of the polymers with small molecular weight PEO. Vibrational spectroscopy identifies the presence of free ions and ion pairs in the electrolytes with PEO of M(w)≤ 8000. The ionic dissolution is improved using PEO as a plasticizer when compared to liquid propylene carbonate, evidently shown in the transference number analysis. Ionic transport follows the Arrhenius equation with a low activation energy (0.16-0.2 eV), leading to high ionic conductivities. Solid electrochromic devices fabricated with the blended P(VDF-TrFE)/PEO electrolytes and polyaniline show good spectroelectrochemical performance in the visible (300-800 nm) and near-infrared (0.9-2.4 μm) regions with a modulation up to 60% and fast switching speed of below 20 seconds. The successful introduction of the solid polymer electrolytes with its best harnessed qualities helps to expedite the application of various electrochemical devices.     

Synthesis of aminoalkylsilanes with oligo(ethylene oxide) unit as multifunctional electrolyte additives for lithium-ion batteries

Aminoalkylsilanes with oligo(ethylene oxide) units were designed and synthesized as multifunctional electrolyte additives for lithium-ion batteries. The chemical structures were fully characterized by nuclear magnetic resonance (NMR) spectroscopy and their thermal properties, viscosities, electrochemical windows, and ionic conductivities were systematically measured. With adding one of these compounds (1 vol. %, DSC3N1) in the baseline electrolyte 1.0 M LiPF₆ in EC: DEC (1:1, in volume), Li/LiCoO₂ half cell tests showed an improved cyclability after 100 cycles and improved rate capability at 5C rate condition. Electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopic (EDS) analysis confirmed the acid scavenging function and film forming capability of DSC3N1. These results demonstrated that the multifunctional organosilicon compounds have considerable potential as additives for use in lithium-ion batteries.     

Ionic conductivity in the crystalline polymer electrolytes PEO6:LiXF6, X = P,As, Sb

Ionically conducting polymers (salts dissolved in a polymer matrix) are of great interest because they uniquely exhibit ionic conductivity in a soft but solid membrane. As such, they are critical to the development of devices such as all-solid-state lithium batteries. The established view of ionic conductivity in polymer electrolytes is that this occurs in amorphous materials above their glass transition temperature and that crystalline polymer electrolytes are insulators. In contrast, we show that three crystalline polymer electrolytes, poly(ethylene oxide)(6):LiXF(6), X = P, As, Sb, not only conduct but do so better than the analogous amorphous phases! It is also shown that the conductivities of all three 6:1 complexes are similar, consistent with the dimension of the bottlenecks to conduction derived from their crystal structures. An increase in ionic conductivity with reduction of molecular weight of the crystalline polymer electrolyte (from 2000 to 1000) is reported and shown to relate to the increase in crystallite size on reducing molecular weight.     

Enhanced Lithium‐Ion Conductivity of Polymer Electrolytes by Selective Introduction of Hydrogen into the Anion

The anion chemistry of lithium salts plays a pivotal role in dictating the physicochemical and electrochemical performance of solid polymer electrolytes (SPEs), thus affecting the cyclability of all‐solid‐state lithium metal batteries (ASSLMBs). The bis(trifluoromethanesulfonyl)imide anion (TFSI^?) has long been studied as the most promising candidate for SPEs; however, the Li‐ion conductivities of the TFSI‐based SPEs still remain low (Li‐ion transference number: ca. 0.2). In this work, we report new hydrogen‐containing anions, conceived based on theoretical considerations, as an electrolyte salt for SPEs. SPEs comprising hydrogen‐containing anions achieve higher Li‐ion conductivities than TFSI‐based ones, and those anions are electrochemically stable for various kinds of ASSLMBs (Li–LiFePO₄, Li–S, and Li–O₂ batteries). This opens up a new avenue for designing safe and high‐performance ASSLMBs in the future.     

Lithiophilic Faceted Cu(100) Surfaces: High Utilization of Host Surface and Cavities for Lithium Metal Anodes

Lithium metal anodes suffer from poor cycling stability and potential safety hazards. To alleviate these problems, Li thin‐film anodes prepared on current collectors (CCs) and Li‐free types of anodes that involve direct Li plating on CCs have received increasing attention. In this study, the atomic‐scale design of Cu‐CC surface lithiophilicity based on surface lattice matching of the bcc Li(110) and fcc Cu(100) faces as well as electrochemical achievement of Cu(100)‐preferred surfaces for smooth Li deposition with a low nucleation barrier is reported. Additionally, a purposely designed solid–electrolyte interphase is created for Li anodes prepared on CCs. Not only is a smooth planar Li thin film prepared, but a uniform Li plating/stripping on the skeleton of 3D CCs is achieved as well by high utilization of the surface and cavities of the 3D CCs. This work demonstrates surface electrochemistry approaches to construct stable Li metal–electrolyte interphases towards practical applications of Li anodes prepared on CCs.     

一种新型物理交联型凝胶聚合物电解质的制备与表征

以甲氧基聚乙二醇甲基丙烯酸酯(MPEGM)和十六烷基聚乙二醇甲基丙烯酸酯(HPEGM)为单体, 三乙二醇二甲醚(TEGDME)为增塑剂, 与锂盐(高氯酸锂, LiClO₄)和光引发剂(安息香二甲醚, DMPA)复合制成光敏体系, 经紫外(UV)固化得到物理交联型凝胶聚合物电解质(GPE)薄膜. 用红外(IR)光谱、差热分析(DSC)、拉伸测试和交流阻抗(AC) 等方法对聚合物基体和电解质的性能进行了研究.结果表明: 当共聚物P(MPEGM-co-HPEGM)中HPEGM含量为50%(w)时, 十六烷基链段(C₁₆)在聚氧化乙烯(PEO)链段静电斥力的作用下发生聚集, 自组装形成了物理交联, 提高了共聚物的空间稳定性; 温度和电解质中各组分的含量对电导率均有较大的影响, 综合性能较好的电解质在30℃时电导率可达0.87×10^-3 S·cm^-1; 采用循环伏安法测得该电解质的电化学窗口为0~4.5 V (vs. Li/Li⁺), 可以满足锂离子电池的应用要求; 组装成的LiFePO₄/GPE/Li电池, 在30℃下以0.1 C和0.2 C倍率进行充放电测试, 首次放电容量分别为154.7和148.0 mAh·g^-1.     

Electrochemical deposition of germanium sulfide from room-temperature ionic liquids and subsequent Ag doping in an aqueous solution

A facile room-temperature electrochemical deposition process for germanium sulfide (GeS(x)) has been developed with the use of an ionic liquid as an electrolyte. The electrodeposition mechanism follows the induced codeposition of Ge and S precursors in ionic liquids generating GeS(x) films. The electrodeposited GeS(x) films were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and Raman and X-ray photoelectron spectroscopy (XPS). An aqueous-based Ag doping method was used to dope electrochemically grown GeS(x) films with controlled doping compared to the conventional process, which can be used in next-generation solid-state memory devices.     

Realisation of an all solid state lithium battery using solid high temperature plastic crystal electrolytes exhibiting liquid like conductivity

Replacement of volatile and combustible electrolytes in conventional lithium batteries is desirable for two reasons: safety concerns and increase in specific energy. In this work we consider the use of an ionic organic plastic crystal material (IOPC), N-ethyl-N-methylpyrrolidinium tetrafluoroborate, [C2mpyr][BF(4)], as a solid-state electrolyte for lithium battery applications. The effect of inclusion of 1 to 33 mol% lithium tetrafluoroborate, LiBF(4), into [C2mpyr][BF(4)] has been investigated over a wide temperature range by differential scanning calorimetry (DSC), impedance spectroscopy, cyclic voltammetry and cycling of full Li|LiFePO(4) batteries. The increases in ionic conductivity by orders of magnitude observed at higher temperature are most likely associated with an increase in Li ion mobility in the highest plastic phase. At concentrations >5 mol% LiBF(4) the ionic conductivity of these solid-state composites is comparable to the ionic conductivity of room temperature ionic liquids. Galvanostatic cycling of Li|Li symmetrical cells showed that the reversibility of the lithium metal redox reaction at the interface of this plastic crystal electrolyte is sufficient for lithium battery applications. For the first time we demonstrate an all solid state lithium battery incorporating solid electrolytes based on IOPC as opposed to conventional flammable organic solvents.     

LiBPON薄膜电解质的制备及电化学性能研究

应用磁控溅射法在N2气氛中制备LiBPON薄膜电解质,研究薄膜性能与沉积条件的关系,优化其制备条件.扫描电镜图显示其表面平整均匀致密,X射线衍射及交流阻抗测试分别表明该薄膜呈非晶态,室温离子电导率随溅射功率增大而减小,随N2压力增大而增大,最高达3.5×10-6S/cm;薄膜的沉积速率随溅射功率增大而增大,随N2压力增大而减小.N的结合对电解质的电化学性能有明显改善,作为薄膜锂电池电解质有良好的应用前景.     

Li1.5Al0.5Ge1.5(PO4)3基固体复合电解质的制备及锂离子导电行为

将聚氧化乙烯(PEO)和二(三氟甲基磺酰)亚胺锂(LiTFSI)混合(固定EO/Li摩尔比为13)后, 采用溶液浇注法制备了一系列不同Li_1.5Al_0.5Ge_1.5(PO₄)₃(LAGP)与PEO质量比的LAGP-PEO(LiTFSI)固体复合电解质体系. 结合电化学阻抗法、 表面形貌表征以及与惰性陶瓷填料(SiO₂, Al₂O₃) 性能的对比分析, 探讨了LAGP在固体复合电解质中的作用机理以及锂离子的导电行为. 结果表明, 在以LAGP为主相的固体复合电解质中, PEO主要处于无定形态, 整个体系主要为PEO与LiTFSI的络合相、 LAGP与PEO(LiTFSI)相互作用形成的过渡相和LAGP晶相. 其中LAGP作为主要的导电基体不仅起到降低PEO结晶度、 改善两相导电界面的作用; 同时自身也可以作为离子传输的通道, 降低锂离子迁移的活化能, 从而使离子电导率得到提高. 当LAGP与PEO的质量比为6:4时, 固体复合电解质的成膜性能最好, 离子电导率最高, 在30 ℃时为2.57×10^-5 S/cm, 接近LAGP的水平, 电化学稳定窗口超过5 V.     

Dense Sphene-type Solid Electrolyte Through Rapid Sintering for Solid-state Lithium Metal Battery

The sphene-type solid electrolyte with high ionic conductivity has been designed for solid-state lithium metal battery. However, the practical applications of solid electrolytes are still suffered by the low relative density and long sintering time of tens of hours with large energy consumption. Here, we introduced the spark plasma sintering technology for fabricating the sphene-type Li_1.125Ta_0.875Zr_0.125SiO₅ solid electrolyte. The dense electrolyte pellet with high relative density of ca. 97.4% and ionic conductivity of ca. 1.44×10^-5 S/cm at 30℃ can be obtained by spark plasma sintering process within the extremely short time of only ca. 0.1 h. Also the solid electrolyte provides stable electrochemical window of ca. 6.0 V(vs. Li⁺/Li) and high electrochemical interface stability toward Li metal anode. With the enhanced interfacial contacts between electrodes and electrolyte pellet by the in-situ formed polymer electrolyte, the solid-state lithium metal battery with LiFePO₄ cathode can deliver the initial discharge capacity of ca. 154 mA·h/g at 0.1 C and the reversible capacity of ca. 132 mA·h/g after 70 cycles with high Coulombic efficiency of 99.5% at 55℃. Therefore, this study demonstrates a rapid and energy efficient sintering strategy for fabricating the solid electrolyte with dense structure and high ionic conductivity that can be practically applied in solid-state lithium metal batteries with high energy densities and safeties.     

Current Scenario and Future Prospective of Ionic-Liquid Doped Polymer Electrolyte for Energy Application

Solid polymer electrolyte (SPE) films based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP) with salt and ionic-liquid (IL) are synthesized using the solution-cast technique and summarized in this review. Doping ILs or salts increases ionic conductivity up to the device level. This is further confirmed using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements. Polarized optical microscopy (POM) affirms that enhancement in ionic conductivity is due to increase in amorphous nature of film. The complex nature of polymer electrolyte films is confirmed using Fourier transform infrared (FT-IR) spectroscopy. Overall results show that doping IL into polyether matrix is advantageous material playing a dominant role in electrochemical devices.     

以水作相分离造孔剂制备P(VDF-HFP)/PMMA聚合物电解质膜

介绍了一种以水代替常用的有机物质作为相分离造孔剂制备混合型聚合物电解质的新方法.所研究的混合型聚合物为聚(偏二氟乙烯-六氟丙烯)和聚甲基丙烯酸甲酯的混合物.扫描电镜SEM图表明这种混合型聚合物膜具有蜂窝状结构,有利于膜电导率的增加.利用FTIR,XRD和DSC等方法研究了混合型聚合物电解质中两种聚合物间的相互作用.用电化学交流阻抗方法测得在30℃下P(VDF-HFP)/PMMA摩尔比为1:1的混合型聚合物电解质的离子电导率为0.804×10^-3S/cm.对照其它方法,本方法具有制备容易、成本较低和有利于环境保护等优点.