Cross-linked Polymer Electrolyte Research Articles

Stretchable Ionic-Liquid-Based Gel Polymer Electrolytes for Lithium-Ion Batteries

Stretchable cross-linked gel polymer electrolytes (C-GPEs) have been fabricated through electron-beam irradiation (EBI) of poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-co-HFP)]/triallyl isocyanurate (TAIC) blend films followed by adsorption of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm][TFSI]). It was found that polymer films containing 5 wt % cross-linker exhibit an excellent IL uptake value of 3.0 when irradiated at 75 kGy. The prepared C-GPEs have a high ion conductivity of 1.4 mS/cm at room temperature compared with a value of 0.7 mS/cm for P(VDF-co-HFP)/IL (1/3, m/m) blend gel. Morphological measurements indicate interconnected nanoporous structures in the films that can provide effective channels for ion immigration. Moreover, the C-GPEs show a high tensile strength of 10.6 MPa and an excellent elasticity, with almost full strain recovery after 100% stretch. In a LiFePO4/C-GPE/Li half-cell, the C-GPEs exhibit high electrochemical stability. There...

Light-cured polymer electrolytes for safe, low-cost and sustainable sodium-ion batteries

In this work we present a very simple preparation procedure of a poly(ethylene oxide) (PEO)-based crosslinked polymer electrolyte (XPE) for application in sodium-ion batteries (NIBs). The polymer electrolyte, containing NaClO4 as Na+ source, is prepared by rapid, energy saving, solvent-free photopolymerization technique, in a single step. Thermal, mechanical, morphological and electrochemical properties of the resulting XPE are thoroughly investigated. The highly ionic conducting (>1 mS cm−1 at 25 °C) polymer electrolyte is used in a lab-scale sodium cell with nanostructured TiO2 working electrode. The obtained results in terms of ambient temperature cycling behaviour (stable specific capacity of about 250 mAh g−1 at 0.1 mA cm−2 and overall remarkable stability, for a quasi-solid state Na polymer cell, upon very long term cycling exceeding 1000 reversible cycles at 0.5 mA cm−2 corresponding to > 5000 h of continuous operation) demonstrate the promising prospects of this novel XPE to be implemented in the next-generation NIBs conceived for large-scale energy storage systems, such as those connected to photovoltaic and wind factories.

Foldable and Rechargeable Zn-Air Batteries

In this work, we fabricate a solid-state, foldable, and rechargeable Zn-air battery which has similar discharge/charge curve after 100 times of repeated folding. Furthermore, the battery exhibits stable cycling performance after 100 times of folding. The foldable air cathodes are based on the directly grown bifunctional catalyst on the graphene coated carbon cloth. Random coating of graphene on the pretreated carbon cloth provides additional surface area to grow the catalyst while maintaining the electrically and mechanically interconnected 3D network in the air cathode. The directly grown catalyst on air cathode improves adhesion at air cathode/catalyst interface, preventing the de-attachment of catalyst during the continuous mechanical deformations. We grow manganese oxides (MnOx) on graphene coated carbon cloth as an active and low cost bifunctional catalyst for solid-state and rechargeable Zn-air batteries via simple immersion process. Solid-state electrolyte allows good flexibility and high safety without the need of costly sealing and the risk of electrolyte leakage. Cross-linked PAA-based electrolyte had given sufficient mechanical strength and conductivity (up to ≈0.46 S cm-1) to be used as solid-state electrolyte. Combining the advantage of MnOx grown on graphene coated carbon cloth and solid electrolyte result in the high performance all-solid-state, foldable, and rechargeable Zn-air batteries. The battery exhibits similar polarization curve and resistance at its fold and flat states. The fold battery is able to achieve to a power density of 32 mW cm-2, almost twice of the power density at its flat state. The cycling stability of the battery at its flat and fold state is better than the batteries with Pt/C on carbon cloth air cathode and the reported solid-state Zn-air batteries in the literature. Polyacrylic acid (PAA)-based electrolytes showed enhanced conductivity as compared to polyvinylalcohol (PVA) or polyethylene oxide (PEO)-based electrolytes due to their low crystallinity and high water retention, resulting in the high conductivity while maintaining desirable mechanical robustness. The obtained PAA-KOH solid electrolyte is transparent, free-standing, and flexible. Unlike gel electrolyte, the solid nature of crosslinked polymer electrolyte is able to prevent short circuit during continuous mechanical deformations. At the same applied current during polarization measurement, the folded battery has an almost similar discharge and charge voltage with the battery at its flat state. The polarization curve of the battery with MnOx-GCC air cathode is enhanced significantly as compared to the battery with GCC and MnOx-CC air cathodes, which only show slightly better performance than the battery with CC air cathode (i.e. without catalyst). At discharge voltage of 1 V, the batteries with GCC and MnOx-CC air cathode have low current (»2.0 and 2.2 mA), five times lower than the battery with MnOx-GCC air cathode. The small voltage gap (i.e. the difference between discharge and charge voltage) indicates an improved rechargeability of the battery with MnOx-GCC air cathode as compared to others batteries. Despite the similar discharge profile, the small footprint of the folded battery results in the high current per unit area. Thus, it has larger power density than the battery at its flat state. The folded battery delivers a power density as high as »32 mW cm-2, almost twice of power density at its flat state (»18 mW cm-2). Under the same device configuration, power density of battery with Pt/C-CC air cathode (»12 mW cm-2) is lower than the battery with MnOx-GCC air cathode, indicating the advantage of high loading density of thin MnOx layer on the dense and interconnected GCC. The battery with MnOx-GCC air cathode has higher discharge voltage and lower charge voltage than the batteries with MnOx-CC air cathode, agreeable to the measured polarization curve. It maintains the same voltages (i.e. discharge voltage of 1.3 V and charge voltage of 1.9 V) for about 170 cycles of discharge/charge test. On the other hand, voltage profile of the battery with Pt-C/CC air cathode degrades gradually over the time. At the end of 70th cycle, its discharge voltage reduces from 1.3 to 0.9 V while its charge voltage increases from 2.0 to 2.4 V, suggesting its low re-chargeability. Battery with MnOx-CC air cathode exhibits stable performance for up to 140 cycles. However, it has poorer discharge and charge voltages (i.e. 1.0 and 2.3 V) than the battery with MnOx-GCC and Pt/C-CC air cathodes. The battery with MnOx-GCC air cathode shows stable performance for up to 110 of discharge/charge cycles, 60 cycles lesser than the same battery at its flat state.

Optimizing ionic conduction of poly(oxyethylene) electrolytes through controlling the cross-link density

Combining polycondensation/hydrogenation allowed varying crosslink density in a controlled way. The obtained solvent-free and oligomer-free polymer electrolytes exhibit outstanding conductivities in a wide temperature range. In comparison with poly(oxyethylene) (PEO) based electrolytes, the conductivities of the new crosslinked polymer electrolytes are much higher at ambient temperatures. Furthermore, their conductivity maxima exceed the PEO ones and, to the best of our knowledge, are the highest known. Moreover, contrary to PEO electrolytes, they don’t creep after melting. The unsophisticated architecture and chemistry make easy the scale up of these promising polymer electrolytes.

Physically Cross-Linked Homopolymer Ion Gels for High Performance Electrolyte-Gated Transistors.

A new type of physically cross-linked solid polymer electrolyte was demonstrated by using a poly(vinylidene fluoride) (PVDF) homopolymer in a room-temperature ionic liquid. The physical origins of gelation, specific capacitance, ionic conductivity, mechanical property, and capacitive charge modulation in organic thin-film electrochemical transistors were investigated systematically. Gelation occurs through bridging phase-separated homopolymer crystals by polymer chains in the composite electrolyte, thereby forming a rubbery network. The resulting homopolymer ion gels are able to accommodate both outstanding electrical (ionically conductive and capacitive) and mechanical (flexible and free-standing) characteristics of the component ionic liquid and the structuring polymer, respectively. These ion gels were successfully applied to organic thin-film transistors as high-capacitance gate dielectrics. Therefore, these results provide an effective route to generate a highly conductive rubbery polymer electrolyte that can be used in widespread electronic and electrochemical devices.

A highly stretchable gel-polymer electrolyte for lithium-sulfur batteries

A stretchable gel-polymer electrolyte (GPE) based on polyepichlorohydrin terpolymer as a host polymer, a mixture of 1,3-dioxolane and 1,2-dimethoxyethane as plasticizers and lithium bis(trifluoromethane)sulfonimide (LiTFSI) as salt was developed and studied in detail. GPEs were prepared in a two-step process. The cross-linked polyepichlorohydrin network was developed using ethylene thiourea (ETU) and magnesium oxide (MgO) as cross-linkers. An immersion method was used for distribution of LiTFSI-salt in the network film. The effects of electrolyte uptake on mechanical and thermal properties of GPEs were studied in detail. Dynamic mechanical analysis (DMA) shows a GPE with a storage modulus higher than 0.6 MPa at ambient temperature (298 K). Differential scanning calorimetry (DSC) analysis was carried out on the GPE to demonstrate the change in glass transition temperature caused by the addition of two plasticizers. Impedance spectroscopy was used to study the ionic conductivity in the GPE. The highest ionic conductivity was found to be 2.4 × 10−4 S/cm at 298 K. The lithium-sulfur cells in conjunction with the elastomeric gel-polymer electrolyte showed characteristic cyclic voltammograms and charge-discharge plateaus indicating a two stage reduction process and a one stage oxidation process. The battery demonstrated initial specific capacity of 700–800 mA h/gsulfur which faded slowly with cycle number. Our present work could pave a new route to fabricate flexible rechargeable batteries with a cross-linked soft polymer electrolyte.

Ionic liquids in a poly ethylene oxide cross-linked gel polymer as an electrolyte for electrical double layer capacitor

Abstract In the present work, we developed a gel polymer electrolyte via the incorporation of a room temperature ionic liquid into a cross-linked polymer matrix. The cross-linked gel electrolyte was prepared using a free radical polymerization of methacrylate and dimethacrylate oligomers dissolved in 1-propyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide. Combining the advantages of the ionic liquids and of conventional polymers, the cross-linked gel polymer electrolyte was used both as a separator and as an electrolyte for a leakage-free and non-flammable EDLC supercapacitor. The quasi-all solid-state supercapacitors showed rather good capacitance, power and energy densities by comparison to a liquid electrolyte-based EDLC.

Deformable and flexible electrospun nanofiber-supported cross-linked gel polymer electrolyte membranes for high safety lithium-ion batteries

A deformable and flexible Li/CGPE/LiFePO4 cell based on CGPE-3 exhibited a high specific capacity and superior cycling stability for lithium-ion batteries.

Cross-Linked Solid Polymer Electrolyte for All-Solid-State Rechargeable Lithium Batteries

Semi-interpenetrated network Solid Polymer Electrolytes (SPEs) were fabricated by UV-induced cross-linking of poly(ethyleneglycol) diacrylate (PEGDA) and divinylbenzene (DVB) within a poly(ethyleneoxide) (PEO) matrix (Mv=5×106gmol−1), comprising lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI), at a molar ratio of EO:Li ∼30:1. The influence of the DVB content on the final SPE properties was investigated in detail. An increase of DVB concentration resulted in self-standing polymer electrolytes. The DVB cross-linker incorporation was found to decrease the crystallinity of the PEO matrix from 34% to 23%, with a decrease in the melting temperature (Tm) of the membrane from 50°C to 34°C. Moreover, the influence of the DVB concentration on the ionic conductivity was determined for polymer electrolytes with 0, 10, 20 and 45% DVB from room temperature (RT) to 80°C. The resulting SPEs showed a high electrochemical stability of 4.3V as well as practical conductivity values exceeding 10−4Scm−1 at 70°C. Cycling performance of these semi-interpenetrated SPE’s have been shown with a Li metal polymer battery and all solid -state Li sulphur battery.

Enhanced proton conductivity at low humidity of proton exchange membranes with triazole moieties in the side chains

Highly conductive, novel sulfonated poly(arylene ether) membranes with different amounts of triazole-introduced monomers (SPAE-TM) were prepared via conventional aromatic condensation reactions. The triazole-introduced monomer (TM) was used as a proton transfer moiety to increase the proton conductivities of polymer electrolyte membranes (PEMs). To compare the chemical, mechanical and thermal stabilities of non-crosslinked polymer electrolyte membranes (SPAE-TM10, SPAE-TM20), crosslinked polymer electrolyte membranes were prepared via the thermal crosslinking method (cSPAE-TM10, cSPAE-TM20). The SPAE-TM membranes exhibited excellent thermal stabilities, and the non-crosslinked SPAE-TM membranes showed satisfactory glass transition temperatures (Tg=250°C). The water uptakes and swelling ratios of the SPAE-TM membranes were successfully suppressed in comparison with the SPAE-TM0 membrane. The proton conductivities of all membranes were higher than those of Nafion 212 over a wide range of temperatures (0.211–0.256S/cm at 80°C, 100% R.H.). The SPAE-TM20 presented a proton conductivity that was 2.3 times higher than that of SPAE-TM0 at 80°C and 30% R.H.

Exceptionally stable polymer electrolyte for a lithium battery based on cross-linking by a residue-free process

Abstract In this paper, we report the synthesis of cross-linked copolymers of glycidyl methacrylate (GMA) and poly (ethylene glycol) methyl methacrylate (PEGMA) for use as solid polymer electrolytes (SPE). The cross-linking is performed with volatile ethylene diamine, thus preventing the accumulation of undesirable precursors in the final membrane. The structure of the cross-linked polymer electrolyte was investigated by 13C solid NMR and its physical properties were examined by DSC, TGA and stress-strain tests. The ionic conductivities were determined by AC Impedance, which showed that the SPEs have good conductivities (10−5 Scm−1) at 80 °C. The highest capacity measured with these polymers was 151 mAh g−1 at C/6 and 80 °C for a LFP/SPE/Lithium battery. The retention capacity is high, at 97% after 80 cycles at different rates of cycling. The Young's modulus of the membranes is as high as 1 GPa. The SEM images showed no evidence of lithium dendrites and no degradation after cycling. Therefore, the polymer is a good candidate for battery operation over a long time. Especially important is the ability of this polymer to prevent growth of dendrites on the Li-metal electrode.

Cross-Linked Polymer Electrolytes for Li-Based Batteries: From Solid to Gel Electrolytes

We report the preparation of solvent-free polymer electrolytes via a free radical copolymerization of methacrylate-based oligomers in the presence of LiTFSI. Properties of the electrolytes were then studied as a function of their compositions. Furthermore, the incorporation of a room temperature ionic liquid (RTIL) into the copolymer electrolyte to form a gel polymer electrolyte (GPE) is also reported. The high miscibility of the oligomers in the RTIL enables the preparation of the GPEs by a one-step method using the in situ free radical copolymerization. The GPEs have a dry aspect and are free-standing; they also exhibit an ionic conductivity close to 4 × 10–4 S cm–1 at 25 °C and to 1.45 × 10–3 S cm–1 at 65 °C. Furthermore, the GPEs have been used as electrolytes in a Li/Electrolyte/LiNi1/3Mn1/3Co1/3O2 battery. Specific capacities of 79 mAh g–1 and 118 mAh g–1 were reached at the C/5 and C/10 rate, respectively.

Polymer electrolytes based on vinyl ethers with various EO chain length and their polymer electrolytes cross-linked by electron beam irradiation

Polymer electrolytes based on vinyl ethers with various ethyleneoxy (EO) chain length (poly-1a (m = 3), poly-1b (m = 6), poly-1c (m = 10), and poly-1d (m = 23.5)) with lithium bis(trifluoromethanesulfonimide) (LiTFSI) were prepared, and effect of pendant EO chain length in the polymers on electrochemical and thermal properties was investigated. Glass transition temperature (T g) of all polymer electrolytes increased linearly with an increase in salt concentrations. Ionic conductivities of the polymer electrolytes increased with an increase in the pendant EO chain length of the polymers at the constant [Li]/[O] ratio, but in the polymer electrolyte of the poly-1d (m = 23.5) with the longest pendant EO chain length, ionic conductivity decreased in the low temperature range of −20 to 10 °C due to the crystallization of the pendant EO chain. The highest ionic conductivity, 1.23 × 10−4 S/cm at 30 °C, was obtained in the polymer electrolyte of the poly-1c (m = 10) with pendant EO chain length of 10 at the [Li]/[O] ratio of 1/20. It was found that the cross-linking of the polymer electrolyte, composed of poly-1c (m = 10) with LiTFSI at the [Li]/[O] ratio of 1/28, by electron beam (EB) irradiation may improve the mechanical property without affecting ionic conductivity, thermal property, and oxidation stability. Polymer electrolytes based on poly-1a (m = 3), poly-1b (m = 6), poly-1c (m = 10), and poly-1d (m = 23.5) and cross-linked polymer electrolytes were electrochemically stable until 4 V and thermally stable around 300 °C.

High Performance Cross-Linked Composite Gel Polymer Electrolyte Using Mesoporous and Reactive SiO2 Nanoparticles for Lithium-Ion Polymer Cells

The rapidly expanding use of rechargeable lithium-ion batteries has led to intensive research on electrolyte systems with high electrochemical performance. However, current lithium-ion batteries have risks associated with leakage and fire hazards due to the high flammability of the organic solvents. In addition, the polyolefin separators used in lithium-ion batteries may shrink and even melt at elevated temperatures, which may cause a short circuit between the two electrodes in cases where unusually high heat is generated. Therefore, there is a pressing need for safer and more reliable electrolyte systems. In this work, a cross-linked composite gel polymer electrolyte was prepared and applied to lithium-ion polymer cells as a safer and more reliable electrolyte. Mesoporous SiO2 nanoparticles containing reactive methacrylate groups as cross-linking sites were synthesized and dispersed into the fibrous polyacrylonitrile membrane. They directly reacted with gel electrolyte precursors containing tri(ethylene glycol) diacrylate, resulting in the formation of a cross-linked composite gel polymer electrolyte with high ionic conductivity and favorable interfacial characteristics. The mesoporous SiO2 particles also served as HF scavengers to reduce the HF content in the electrolyte at high temperature. As a result, the cycling performance of the lithium-ion polymer cells with cross-linked composite gel polymer electrolytes employing methacrylate-functionalized mesoporous SiO2 nanoparticles was remarkably improved at elevated temperatures as well as ambient temperature.

Nanohybrid Polymer Electrolytes with Enhanced Safety and Electrochemical Performance

Rechargeable Li/Na-ion batteries have been studied extensively for the electric and energy industries, but currently used liquid electrolytes have serious safety risks (combustion and explosion). Besides, nonuniform ion (Li+/Na+) deposition on the negative electrode upon cycling would eventually cause the cell to fail. Hence, the development of safe, stable, and long-life Li/Na-ion batteries is being intensively pursued to enable high-energy-density storage system applications. Solid polymer electrolyte (SPE) is attracting considerable attention to handle potential safety risk and regarded as a safer alternative to satisfy the needs for high-performance batteries. However, low conductivities and insufficient electrode-electrolyte interfaces still hinder the potential applications of SPEs. Here we have been targeting poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and devoted a large amount of research to modifying the polymer matrix, including copolymerization of PEGMEM and SMA (stearyl methacrylate), OV-POSS based graft polymer electrolyte with star-shaped structure and construction of cross-linked branching nanohybrid polymer electrolyte by functionalized nanoparticles with polymer chains. We focus on the exploring the interfacial design to enhance interaction between nanoparticles and the polymer matrix, and utilize microscopic and spectroscopic analyses to better understand the interfacial chemistry between particles and polymeric chains.

Solid polymer electrolytes containing poly(ethylene glycol) and renewable cardanol moieties for all-solid-state rechargeable lithium batteries

A series of self-crosslinkable polymers composed of different amounts of ionic conducting units (poly(ethylene glycol) methyl ether methacrylate) and crosslinkable units (2-hydroxy-3-cardanylpropyl methacrylate) obtained from a renewable resource, cardanol, were prepared for application to solid polymer electrolytes. Free-standing solid polymer electrolytes were prepared by mixing the polymers with lithium bis(trifluoromethanesulfonyl)imide followed by UV irradiation to induce reaction of the double bonds in the cardanol moiety, forming the cross-linked structures. The ionic conductivity of the solid crosslinked polymer electrolyte prepared from the polymers containing 8 mol% of the cross-linkable cardanol monomeric units was 1.9 × 10−4 S cm−1 at 60 °C, which is close to those of poly(poly(ethylene glycol) methyl ether methacrylate) in the waxy state. The all-solid-state lithium battery prepared using this solid polymer electrolyte without a separator exhibited stable cell operation, showing 81.4% of capacity retention after 100 charge-discharge cycles, and demonstrating that the self-crosslinkable polymer from the renewable resource is suitable for high-temperature and high-voltage lithium secondary battery applications.

Effect of Plasticization on Ionic Conductivity Enhancement in Relation to Glass Transition Temperature of Crosslinked Polymer Electrolyte Membranes

The relationship between glass transition (Tg) and ionic conductivity (σ) of an amorphous crosslinked polymer electrolyte membrane (PEM) was examined based on ion–dipole complexation between dissociated lithium cations and ether oxygen of poly(ethylene glycol diacrylate) and plasticization by succinonitrile (SCN). In a binary PEM consisting of a lithium salt/polymer network, Tg increased due to a strong ion–dipole interaction, whereas σ declined due to lower ion mobility coupled to reduced chain mobility. Above the threshold salt concentration of 7 mol %, dual loss tangent peaks were observed in dynamic mechanical studies, which may be ascribed to segmental relaxations of ion–dipole complexed networks and that of polymer chains surrounding the undissociated lithium salt acting like “fillers”. Upon SCN plasticization, these two peaks merged into one that was further suppressed below Tg of the pure network, whereas σ improved to the superionic conductor level. The role of plasticization on the ionic conduct...

Quaternized graphene oxide modified ionic cross-linked sulfonated polymer electrolyte composite proton exchange membranes with enhanced properties

A series of novel ionic cross-linked sulfonated poly(ether sulfone) (SPES)-based proton exchange membranes (PEMs) were successfully constructed by using quaternized graphene oxide (QGO) as the inorganic fillers and cross-linking agents. The ionic cross-linking networks were implemented by the interactions between the sulfonic acid groups of SPES and the quaternary ammonium groups of QGO. The influences of different loading contents of QGO on the properties of the ionic cross-linked composite membranes were studied. The composite membranes showed the enhanced mechanical properties and improved oxidative stabilities. Meanwhile, the swelling ratio, water uptake and methanol permeability of the ionic cross-linked SPES/QGO composite membranes were much lower than that of the pristine SPES membrane. The swelling ratio and water uptake of SPES-10-QGO composite membrane had the minimum values among all the composite membranes. In addition, although the proton conductivity of ionic cross-linked SPES membranes by QGO decreased, SPES-10-QGO still exhibited high proton conductivity of about 0.08Scm−1 at 80°C. All the results indicated that the ionic cross-linked composite membranes with balanced properties were the potential candidate materials for PEMs.

Ionic Liquid-Based Polymer Electrolytes via Surfactant-Assisted Polymerization at the Plasma-Liquid Interface.

We first report an innovative method, which we refer to as interfacial liquid plasma polymerization, to chemically cross-link ionic liquids (ILs). By this method, a series of all-solid state, free-standing polymer electrolytes is successfully fabricated where ILs are used as building blocks and ethylene oxide-based surfactants are employed as an assisted-cross-linking agent. The thickness of the films is controlled by the plasma exposure time or the ratio of surfactant to ILs. The chemical structure and properties of the polymer electrolyte are characterized by scanning electron microscopy (SEM), Fourier transformation infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). Importantly, the underlying polymerization mechanism of the cross-linked IL-based polymer electrolyte is studied to show that fluoroborate or halide anions of ILs together with the aid of a small amount of surfactants having ethylene oxide groups are necessary to form cross-linked network structures of the polymer electrolyte. The ionic conductivity of the obtained polymer electrolyte is 2.28 × 10(-3) S·cm(-1), which is a relatively high value for solid polymer electrolytes synthesized at room temperature. This study can serve as a cornerstone for developing all-solid state polymer electrolytes with promising properties for next-generation electrochemical devices.

Cross-linked Composite Gel Polymer Electrolyte using Mesoporous Methacrylate-Functionalized SiO2 Nanoparticles for Lithium-Ion Polymer Batteries.

Liquid electrolytes composed of lithium salt in a mixture of organic solvents have been widely used for lithium-ion batteries. However, the high flammability of the organic solvents can lead to thermal runaway and explosions if the system is accidentally subjected to a short circuit or experiences local overheating. In this work, a cross-linked composite gel polymer electrolyte was prepared and applied to lithium-ion polymer cells as a safer and more reliable electrolyte. Mesoporous SiO2 nanoparticles containing reactive methacrylate groups as cross-linking sites were synthesized and dispersed into the fibrous polyacrylonitrile membrane. They directly reacted with gel electrolyte precursors containing tri(ethylene glycol) diacrylate, resulting in the formation of a cross-linked composite gel polymer electrolyte with high ionic conductivity and favorable interfacial characteristics. The mesoporous SiO2 particles also served as HF scavengers to reduce the HF content in the electrolyte at high temperature. As a result, the cycling performance of the lithium-ion polymer cells with cross-linked composite gel polymer electrolytes employing methacrylate-functionalized mesoporous SiO2 nanoparticles was remarkably improved at elevated temperatures.