Electrochemical investigation of gel polymer electrolytes based on poly(methyl methacrylate) and dimethylacetamide for application in Li-ion batteries

In the present work, gel polymer electrolytes (GPEs) were prepared using poly(methyl methacrylate) (PMMA), lithium perchlorate (LiClO₄) and dimethylacetamide as a plasticizer. Solution-casting technique was used to fabricate GPEs containing different weight percentage of PMMA. The degree of crystallinity of GPE samples was studied by X-ray diffraction (XRD) analysis. Fourier transform infrared (FT-IR) spectroscopy was applied to study the level of interactions between lithium salt and PMMA in the prepared GPEs. Electrochemical properties were studied by electrochemical impedance spectroscopy, linear sweep voltammetry and DC polarization techniques. Lithium ion conductivity of GPEs was determined by calculating the bulk resistance of polymer electrolytes from Nyquist plot. Increasing PMMA content of GPEs resulted in an improvement in the electrochemical potential window from 4.2 to 4.5 V. The highest lithium transference number (0.42) and also the best electrochemical properties were obtained for GPE containing 0.75 M LiClO₄ and 10 wt% PMMA. Scanning electron microscopy images of the optimized GPE showed a porous and heterogeneous surface structure which is desirable for application in Li-ion batteries.     

A novel sandwiched membrane as polymer electrolyte for application in lithium-ion battery

A novel kind of sandwiched polymer membrane was prepared, which consists of two outer layers of electrospun poly(vinyl difluoride) (PVDF) fibrous films and one inner layer of poly(methyl methacrylate) (PMMA) film. Its characteristics were investigated by scanning electron microscopy and X-ray diffraction. The membrane can easily absorb non-aqueous electrolyte to form gelled polymer electrolytes (GPEs). The resulting gelled polymer electrolytes had a high ionic conductivity up to 1.93 × 10⁻³ S cm⁻¹ at room temperature, and exhibited a high electrochemical stability potential of 4.5 V (vs. Li/Li⁺). It is of great potential application in polymer lithium-ion batteries.     

PEO-LITFSI-SiO2-SN System Promotes the Application of Polymer Electrolytes in All-Solid-State Lithium-ion Batteries

All-solid-state polymer lithium-ion batteries are ideal choice for the next generation of rechargeable lithium-ion batteries due to their high energy, safety and flexibility. Among all polymer electrolytes, PEO-based polymer electrolytes have attracted extensive attention because they can dissolve various lithium salts. However, the ionic conductivity of pure PEO-based polymer electrolytes is limited due to high crystallinity and poor segment motion. An inorganic filler SiO₂ nanospheres and a plasticizer Succinonitrile (SN) are introduced into the PEO matrix to improve the crystallization of PEO, promote the formation of amorphous region, and thus improve the movement of PEO chain segment. Herein, a PEO₁₈−LiTFSI−5 %SiO₂−5 %SN composite solid polymer electrolyte (CSPE) was prepared by solution-casting. The high ionic conductivity of the electrolyte was demonstrated at 60 °C up to 3.3×10⁻⁴ S cm⁻¹. Meanwhile, the electrochemical performance of LiFePO₄/CSPE/Li all-solid-state battery was tested, with discharge capacity of 157.5 mAh g⁻¹ at 0.5 C, and capacity retention rate of 99 % after 100 cycles at 60 °C. This system provides a feasible strategy for the development of efficient all-solid-state lithium-ion batteries.     

Design and Fabrication of PEO-HPMC@Ht Composite Solid-state Electrolytes in All-solid-state Lithium Battery

All-solid electrolyte instead of frequently-used inflammable electrolyte can enhance the security and energy density of batteries effectively. However, the low ionic conductivity lead to increased lithium dendrites and increased resistance of the cell at 30 °C. In this work, non-toxic and low-cost hydroxypropyl methylcellulose (HPMC) was introduced simultaneously with non-polluting hectorite (Ht) into polyoxyethylene (PEO) to obtain novel composite solid-state electrolytes (CSEs). The optimized CSEs has a high ionic conductivity (1.1×10⁻³ S/cm) at 30 °C. This work demonstrates that the novel PEO-HPMC@Ht CSEs are extremely promising.     

Tough Gel Electrolyte Using Double Polymer Network Design for the Safe,Stable Cycling of Lithium Metal Anode

The growth of lithium dendrites and low coulombic efficiency restrict the development of Li metal anodes. Polymer electrolytes are expected to be promising candidates to solve the issue, but ways to obtain a polymer electrolyte that integrates high ionic conductivity and high mechanical toughness is still challenging. By introducing a double polymer network into the electrolyte design to reshape it, a tough polymer electrolyte was developed with high conductivity, and stable operation of lithium metal anodes was further realized. The double network (DNW) gel electrolyte has high modulus of 44.3 MPa and high fracture energy of 69.5 kJ m⁻². The conductivity of DNW gel is 0.81 mS cm⁻¹ at 30 °C. By using this gel electrolyte design, the lithium metal electrode could be cycled more than 400 times with a coulombic efficiency (CE) as high as 96.3 % with carbonate‐based electrolytes.     

Ultraviolet-Cured Semi-Interpenetrating Network Polymer Electrolytes for High-Performance Quasi-Solid-State Lithium Metal Batteries

Solid polymer electrolytes with relatively low ionic conductivity at room temperature and poor mechanical strength greatly restrict their practical applications. Herein, we design semi-interpenetrating network polymer (SNP) electrolyte composed of an ultraviolet-crosslinked polymer network (ethoxylated trimethylolpropane triacrylate), linear polymer chains (polyvinylidene fluoride-co-hexafluoropropylene) and lithium salt solution to satisfy the demand of high ionic conductivity, good mechanical flexibility, and electrochemical stability for lithium metal batteries. The semi-interpenetrating network has a pivotal effect in improving chain relaxation, facilitating the local segmental motion of polymer chains and reducing the polymer crystallinity. Thanks to these advantages, the SNP electrolyte shows a high ionic conductivity (1.12 mS cm⁻¹ at 30 °C), wide electrochemical stability window (4.6 V vs. Li⁺/Li), good bendability and shape versatility. The promoted ion transport combined with suppressed impedance growth during cycling contribute to good cell performance. The assembled quasi-solid-state lithium metal batteries (LiFePO₄/SNP/Li) exhibit good cycling stability and rate capability at room temperature.     

Characterization and properties of ternary P(VdF-HFP)-LiTFSI-EMITFSI ionic liquid polymer electrolytes

Gel polymer electrolytes containing 1-ethyl-3-methylimidazolium-bis (trifluoromethyl-sulfnyl)imide (EMITFSI) ionic liquid were prepared for lithium ion batteries by solution casting method. Thermal and electrochemical properties have been determined for the gel polymer electrolytes. Proper addition of EMITFSI to the P(VdF-HFP)-LiTFSI polymer electrolyte improves the ionic conductivity and electrochemical window to 2.11 × 10⁻³ S cm⁻¹ (30 °C) and 4.6 V. In combination of the prepared ternary P(VdF-HFP)-LiTFSI-EMITFSI ionic liquid polymer electrolytes, Li₄Ti₅O₁₂ anode exhibited two extra voltage plateaus around 1.1 V and 2.3 V except the typical voltage plateau around 1.6 V by possible side reaction between ionic liquid and polymer. LiFePO₄ cathode exhibited high capacity above 140 mA h g⁻¹ and retention of 93.1% due to the suppressed polarization effect caused by enhanced ion transport properties. The high temperature of 80 °C didn't have significant impact on the cycling performance.     

Review on gel polymer electrolytes for lithium batteries

This paper reviews the state-of-art of polymer electrolytes in view of their electrochemical and physical properties for the applications in lithium batteries. This review mainly encompasses on five polymer hosts namely poly(ethylene oxide) (PEO), poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVdF) and poly(vinylidene fluoride-hexafluoro propylene) (PVdF-HFP) as electrolytes. Also the ionic conductivity, morphology, porosity and cycling behavior of PVdF-HFP membranes prepared by phase inversion technique with different non-solvents have been presented. The cycling behavior of LiMn₂O₄/polymer electrolyte (PE)/Li cells is also described.     

Eutectic-Based Polymer Electrolyte with the Enhanced Lithium Salt Dissociation for High-Performance Lithium Metal Batteries

The deployment of lithium metal anode in solid-state batteries with polymer electrolytes has been recognized as a promising approach to achieving high-energy-density technologies. However, the practical application of the polymer electrolytes is currently constrained by various challenges, including low ionic conductivity, inadequate electrochemical window, and poor interface stability. To address these issues, a novel eutectic-based polymer electrolyte consisting of succinonitrile (SN) and poly (ethylene glycol) methyl ether acrylate (PEGMEA) is developed. The research results demonstrate that the interactions between SN and PEGMEA promote the dissociation of the lithium difluoro(oxalato) borate (LiDFOB) salt and increase the concentration of free Li⁺. The well-designed eutectic-based PAN_1.2-SPE (PEGMEA: SN=1: 1.2 mass ratio) exhibits high ionic conductivity of 1.30 mS cm⁻¹ at 30 °C and superior interface stability with Li anode. The Li/Li symmetric cell based on PAN_1.2-SPE enables long-term plating/stripping at 0.3 and 0.5 mA cm⁻², and the Li/LiFePO₄ cell achieves superior long-term cycling stability (capacity retention of 80.3 % after 1500 cycles). Moreover, Li/LiFePO₄ and Li/LiNi_0.6Co_0.2Mn_0.2O₂ pouch cells employing PAN_1.2-SPE demonstrate excellent cycling and safety characteristics. This study presents a new pathway for designing high-performance polymer electrolytes and promotes the practical application of high-stable lithium metal batteries.     

The network gel polymer electrolyte based on poly(acrylate-co-imide) and its transport properties in lithium ion batteries

Poly (acrylate-co-imide)-based gel polymer electrolytes are synthesized by in situ free radical polymerization. Infrared spectroscopy confirms the complete polymerization of gel polymer electrolytes. The ionic conductivity of gel polymer electrolytes are measured as a function of different repeating EO units of polyacrylates. An optimal ionic conductivity of the poly (PEGMEMA₁₁₀₀-BMI) gel polymer electrolyte is determined to be 4.8 × 10^–3 S/cm at 25 °C. The lithium transference number is found to be 0.29. The cyclic voltammogram shows that the wide electrochemical stability window of the gel polymer electrolyte varies from −0.5 to 4.20 V (vs. Li/Li⁺). Furthermore, we found the transport properties of novel gel polymer electrolytes are dependent on the EO design and are also related to the rate capability and the cycling ability of lithium polymer batteries. The relationship between polymer electrolyte design, lithium transport properties and battery performance are investigated in this research.     

Electrical and Structural Properties of Poly (Methyl Methacrylate) Doped Potassium Iodide (KI) Solid Polymer Electrolyte

A high-conducting salt-doped polymer electrolyte layer has been created here for use in photocell technologies. The solution casting method is used to produce ion conducting film where poly (methyl methacrylate) (PMMA) is used as the host polymer and potassium iodide (KI) as the dopant. The conductivity and amorphic increases of the polymer electrolytes with the addition of salt concentrations helps in the enhancement of the charge transfer properties. Using electrochemical impedance spectroscopy (EIS), ionic conductivity is evaluated where maximum conductivity is 3.99 × 10⁻⁶ S cm^-1 at 20 wt% KI concentration. Polarized optical microscopy (POM) shows the reduction in crystallinity by salt doping, while Fourier transforms infrared spectroscopy (FTIR) shows the complexation as well as composite nature of the film. Ionic transference number (t_ion) measurement shows the predominantly ionic nature of this polymer electrolyte.     

High ionic conductivity of all-solid polymer electrolytes based on polyorganophosphazenes

A series of all-solid polymer electrolytes were prepared by cross-linking new designed poly(organophosphazene) macromonomers. The ionic conductivities of these all-solid, dimensional steady polymer electrolytes were reported. The temperature dependence of ionic conductivity of the all-solid polymer electrolytes suggested that the ionic transport is correlated with the segmental motion of the polymer. The relationship between lithium salts content and ionic conductivity was discussed and investigated by Infrared spectrum. Furthermore, the polarity of the host materials was thought to be a key to the ionic conductivity of polymer electrolyte. The all-solid polymer electrolytes based on these poly(organophosphazenes) showed ionic conductivity of 10⁻⁴ S cm⁻¹ at room temperature.     

基于静电纺丝和静电喷射技术的P(VDF-HFP)/Al2O3/P(VDF-HFP)复合隔膜的制备与电化学性能分析

通过静电纺丝和静电喷射技术, 将三氧化二铝(Al₂O₃)纳米颗粒沉积在两层聚四氟乙烯六氟丙烯[P(VDF-HFP)]静电纺丝隔膜之间, 制备出了具有“三明治”结构的P(VDF-HFP)/Al₂O₃/P(VDF-HFP)复合锂离子电池隔膜. 分析了隔膜的形态结构、 热收缩性能、 拉伸性能、 电化学性能以及隔膜在电池中的循环性能. 测试结果表明, 该复合隔膜比纯P(VdF-HFP)膜拥有更高的吸液率, 隔膜更容易吸收电解液从而形成凝胶聚合物电解质(GPEs). 该复合隔膜的拉伸强度在4 MPa左右, 相对应的断裂伸长率为261.57%. 复合隔膜在室温下的离子电导率为1.61×10^-3 S/cm, 且表现出了较高的电化学稳定性(电化学稳定窗口达到5.4 V). 在电池的循环测试中, 使用钴酸锂(LiCoCO₂)作为正极材料, 由该复合隔膜组装的电池的首次放电比容量达到了理想的水平, 为145 mA·h·g^-1.     

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.

     

单分散SiO2纳米颗粒复合凝胶电解质的应用

以单分散程度较高的SiO₂纳米颗粒(约130 nm)作为填料,聚偏氟乙烯-六氟丙烯(PVDF-HFP)作为聚合物基质,采用简便的物理共混法制备出了一种单分散SiO₂纳米颗粒复合凝胶聚合物电解质(MCGPEs)并将其应用于锂电池中。扫描电镜结果表明,SiO₂纳米颗粒在聚合物基体中分散均匀。与传统凝胶聚合物电解质(GPEs)和商业SiO₂颗粒复合凝胶电解质(CGPEs)相比,MCGPEs有着更高的电解液吸液能力和离子电导率,并且具备更强的锂离子迁移能力。此外,使用MCGPEs作为电解质的锂电池,在1.0C下历经300次循环后仍然保持了121.1 mAh·g^-1的较高比容量,表现出了优异的循环性能。同时,其倍率性能也十分优异,在10C倍率下获得了135 mAh·g^-1的比容量,远高于GPEs锂电池(76.2 mAh·g^-1)。     

高锂离子电导的有机-无机复合电解质的渗流结构设计

固态聚合物电解质被认为是解决传统液态锂金属电池安全隐患和循环性能的关键材料,但仍然存在离子电导率低,界面兼容性差等问题。近年来,基于无机填料与聚合物电解质的高锂离子电导的有机-无机复合电解质备受关注。根据渗流理论,有机-无机界面被认为是复合电解质离子电导率改善的主要原因。因此,设计与优化有机-无机渗流界面对提高复合电解质离子电导率具有重要意义。本文从渗流结构的设计出发,综述了不同维度结构的无机填料用于高锂离子电导的有机-无机复合电解质的研究进展,并对比分析了不同渗流结构的优缺点。基于上述评述,展望了有机-无机复合电解质的未来发展趋势和方向。     

A new composite polymer electrolyte based on poly(ethyleneoxide)/ polysiloxane/BMImTFSI/organomontmorillonite

Composite polymer electrolytes based on poly(ethylene oxide)-polysiloxane/l-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide/organomontmorillonite(PEO-PDMS/1L/OMMT) were prepared and characterized.Addition of both an ionic liquid and OMMT to the polymer base of PEO-PDMS resulted in an increase in ionic conductivity.At room temperature,the ionic conductivity of sample PPB100-OMMT4 was 2.19×10~3 S/cm.The composite polymer electrolyte also exhibited high thermal and electrochemical stability and may potentially be applied in lithium batteries.     

Safety-enhanced Polymer Electrolytes with High Ambient-temperature Lithium-ion Conductivity Based on ABA Triblock Copolymers

Liquid electrolytes used in lithium-ion batteries suffer from leakage,flammability,and lithium dendrites,making polymer electrolyte a potential alternative.Herein,a series of ABA triblock copolymers(ABA-x)containing a mesogen-jacketed liquid crystalline polymer(MJLCP)with a polynorbornene backbone as segment A and a second polynorbornene-based polymer having poly(ethylene oxide)(PEO)side chains as segment B were synthesized through tandem ring-opening metathesis polymerizations.The block copolymers can self-assemble into ordered morphologies at 200℃.After doping of lithium salts and ionic liquid(IL),ABA-x self-assembles into cylindrical structures.The MJLCP segments with a high glass transition temperature and a stable liquid crystalline phase serve as physical crosslinking points,which significantly improve the mechanical performance of the polymer electrolytes.The ionic conductivity of ABA-x/lithium salt/IL is as high as 10-3 S·cm-1 at ambient temperature owing to the high IL uptake and the continuous phase of conducting PEO domains.The relationship between ionic conductivity and temperature fits the Vogel-Tamman-Fulcher(VTF)equation.In addition,the electrolyte films are flame retardant owing to the addition of IL.The polymer electrolytes with good safety and high ambient-temperature ionic conductivity developed in this work are potentially useful in solid lithium-ion batteries.     

Effect of solvated ionic liquids on the ion conducting property of composite membranes for lithium ion batteries

We prepared the polyethylene oxide (PEO)-based composite membrane electrolytes which contained the specialized ionic liquids and the inorganic filler of Li₇La₃Zr₂O₁₂ (LLZO). Mixtures of ionic liquids and tetragonal inorganic fillers were used as additives to prepare composite electrolytes for an application of all solid-state lithium ion batteries (ASLBs). In order to improve the ionic conductivity of composite membranes, we studied the structural change and the electrochemical behaviors as a function of the amounts of solvated ionic liquids (ILs). The addition effect of solvated ILs showed the higher ionic conductivity such as 10^?4 S/cm at 55 °C by reducing the crystalline character of polymer based composite, resulting in the enhanced ion conducting property. The hybrid composite membranes were successfully made in flexible form, and have an excellent thermal and electrochemical stability. Finally, the electrochemical performance of the half-cell was evaluated, and it was confirmed that the ion-conducting characteristics were influenced and controlled by the effect of ILs.     

High ionic conductive PVDF-based fibrous electrolytes

The high ionic conductive polymer electrolytes were prepared based on poly(vinylidenefluoride) (PVDF) fibers modified via preirradiation grafting poly(methyl methacrylate) (PMMA). In these polymer electrolytes, the PVDF fibers served as the supporting phase providing dimensional stability, and PMMA acted as the gel phase helping for the trapping liquid electrolyte and substituting the nonconductive PVDF phase to provide contact with electrodes well thus increasing conductive area. The modified PVDF fibrous membranes were used as a polymer electrolyte in lithium ion battery after they were activated by uptaking 1 M LiPF₆/ethylene carbonate–dimethyl carbonate (1:1 vol) liquid electrolyte, which showed a much higher room-temperature ionic conductivity than the pristine PVDF fibrous membrane. The LiCoO₂-mesocarbon microbead coin cells containing the dual-phase fibrous membrane (degree of graft, 111.8%) demonstrated excellent rate performance, and the cell still retained about 86% of discharge capacity at 4C rate, as compared to that at 0.1C rate. The prototype cell showed good cycle performance.