Polymer Electrolyte Matrix Research Articles

Ion Transport Enhancement Mechanism in Polymer/Ceramic Composite Electrolyte with High-Entropy Li-Garnet

Given the growing demand for electrification, delivering safe, high power, and high energy in lithium-ion batteries is a key challenge. One possible approach is incorporating Li-ion conductive ceramics into a polymer electrolyte matrix. Benefiting from both components, composite electrolytes may deliver high safety, improved ionic conductivity, enhanced electrochemical stability, and feasible construction for solid-state batteries. Specifically, it is crucial to understand and verify the ion transport enhancement mechanism in such a composite electrolyte, as the conductivity in the electrolytes directly affects the overall cell performance and the electrolyte design principles for these systems may change.In this work, we investigate the ion transport enhancement mechanism in composites made with a single-ion conducting (SIC) polymer electrolyte with high-entropy Li-garnet (HE-LLZO) micron-sized powders. We use broadband dielectric spectroscopy (BDS), thermal gravimetric analysis (TGA), rheology measurement and proton nuclear magnetic resonance (1H NMR) to understand the ion transport kinetics in the composites. At 30 °C, 30 wt% HE-LLZO composites with SIC polymer showed almost 8-fold enhancement in conductivity. The addition of HE-LLZO leads to the different degree of polymerization compared to that of the pure polymer, implying that the substantial amount of unpolymerized monomer facilitated the conductivity in the composites. To further investigate the reaction mechanism in the composites, Fourier transform infrared (FT-IR) spectroscopy results will be presented along with 1H NMR data. Electrochemical properties and cell performance will be compared to further illustrate the effects of HE-LLZO on the composite. Acknowledgements This work was supported as part of the Fast and Cooperative Ion Transport in Polymer-Based Materials (FaCT), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences at Oak Ridge National Laboratory under contract DE-AC05-00OR22725.

Polyether‐Derived Carbon Material and Ionic Liquid (Tributylmethylphosphonium iodide) Incorporated Poly(Vinylidene Fluoride‐co‐Hexafluoropropylene)‐Based Polymer Electrolyte for Supercapacitor Application

ABSTRACTPoly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP)‐sodium thiocyanate (NaSCN) solid polymer electrolytes containing different weight ratios of ionic liquid (IL)—tributylmethylphosphonium iodide (TBMPI) were prepared using solution‐cast approach. Electrochemical impedance data indicates that increasing ionic liquid into polymer electrolyte matrix increases ionic conductivity and the maximum value of ionic conductivity was obtained at 150 wt% TBMPI, having conductivity value of 8.3 × 10−5 S cm−1. The dielectric measurement supports our conductivity data. Ionic transference number measurement affirms this system to be predominantly ionic in nature, while electrochemical stability window (ESW) was found to be 3.4 V. Polarized optical microscopy (POM) along with differential scanning calorimetry (DSC) suggest suitability of TBMPI as plasticizer, while infrared spectroscopy (FTIR) confirms ion interaction, complexation, and composite nature. The thermogravimetric analysis (TGA) shows thermal stability of these ionic liquid‐doped polymer electrolytes (ILDPEs). Using maximum conducting ILDPE, a sandwiched supercapacitor has been fabricated which shows stable performance as high as 228 Fg−1 using cyclic voltammetry (CV).

Soy protein isolate–based gel polymer electrolyte for flexible solid-state supercapacitor

At present, the polymer matrices of most polymer electrolytes are derived from petroleum-based synthetic polymers. Herein, sustainable and renewable soy protein isolate (SPI) was grafted with methacrylic acid (MAA) and then cross-linked by ring-opening reaction with polyethylene glycol diglycidyl ether as cross-linking agent to obtain a biomass-based polymer electrolyte. Results show that when the added amount of MAA is twice the quality of SPI, gel polymer electrolyte displays the best comprehensive properties and presents the highest ionic conductivity of 5.24 × 10−3 S/cm. The flexible supercapacitor was fabricated by using SPI-based gel polymer electrolyte with activated carbon electrodes, which exhibited excellent specific capacitance (128.63 F/g) and energy density (9.52 Wh/kg) at 0.5 A/g with a decent capacitance retention of 93% after 5000 charge–discharge cycles. It can be ascribed that grafting modification of SPI improves the interface performance of electrode–polymer electrolyte. Furthermore, potassium iodide is introduced to form a redox polymer electrolyte to achieve a high-energy-density supercapacitor, which provides outstanding energy density of 24.40 Wh/kg at 1.0 A/g. This work demonstrates that sustainable and renewable biomass can be converted into matrix of polymer electrolyte for high performance supercapacitor based on aqueous polymer electrolyte.

Boron Surface Treatment of Li7La3Zr2O12 Enabling Solid Composite Electrolytes for Li-Metal Battery Applications.

Despite being promoted as a superior Li-ion conductor, lithium lanthanum zirconium oxide (LLZO) still suffers from a number of shortcomings when employed as an active ceramic filler in composite polymer-ceramic solid electrolytes for rechargeable all-solid-state lithium metal batteries. One of the main limitations is the detrimental presence of Li2CO3 on the surface of LLZO particles, restricting Li-ion transport at the polymer-ceramic interfaces. In this work, a facile way to improve this interface is presented, by purposely engineering the LLZO particle surfaces for a better compatibility with a PEO:LiTFSI solid polymer electrolyte matrix. It is shown that a surface treatment based on immersing LLZO particles in a boric acid solution can improve the LLZO surface chemistry, resulting in an enhancement in the ionic conductivity and cation transference number of the CPE with 20 wt % of boron-treated LLZO particles compared to the analogous CPE with non-treated LLZO. Ultimately, an improved cycling performance and stability in Li//LiFePO4 cells was also demonstrated for the modified material.

Multifunctional composite electrolytes for mechanically-robust and high energy density carbon fiber structural batteries

Mechanically robust electrolytes with high ionic conductivity play an essential role in carbon fiber (CF) structural batteries that simultaneously store energy and bear mechanical loads. However, multifunctional composite electrolytes are rarely developed, especially for air-stable and safe structural Zn-ion batteries. Herein, a composite electrolyte GF-SPE is designed and fabricated by integrating ionic conductive poly(ethylene glycol) diacrylate (PEGDA)-based solid-state polymer electrolyte (SPE) matrix and glass fiber fabric (GF) reinforcement, which simultaneously exhibits mechanical robustness and high ionic conductivity, facilitating homogeneous Zn electrodeposition without obvious side reaction, such as dendrite growth, corrosion et al. Therefore, the symmetric cells Zn//GF-SPE//Zn cell can cycle stably for more than 800 h at 1 mA cm−2. The carbon fiber structural battery fabricated with composite structural electrolyte GF-SPE delivers a high energy density of 19.35 Wh kg−1 based on the total mass of the whole device and cycling stability over 1,000 cycles in extreme environments. Furthermore, the high capacity of structural Zn-ions batteries can be maintained when they withstand flexural stress of over 120 MPa. The in-situ mechanical-electrochemical testing further confirms the priority of structural Zn-ion batteries.

High-Stability Composite Solid Polymer Electrolyte Composed of PAEPU/PP Nonwoven Fabric for Lithium-Ion Batteries.

Solid polymer electrolytes have attracted considerable attention, owing to their flexibility and safety. At present, poly(ethylene oxide) is the most widely studied polymer electrolyte matrix. It exhibits higher safety than the polyolefin diaphragm used in traditional lithium-ion batteries. However, it readily crystallizes at room temperature, resulting in low ionic conductivity, and the preparation process involves organic solvents. In this study, from the perspective of molecular design, solvent-free polyaspartate polyurea (PAEPU) and the cheap and easily available polypropylene (PP) nonwoven fabric were used as support materials for the PAEPU/PP composite solid polymer electrolyte (PAEPU/PP m -CPE). This CPE has good thermal stability, dimensional stability, flexibility, and mechanical properties. Among the different CPEs that were analyzed, PAEPU/PP10-CPE@20 had the highest ionic conductivity, which was reinforced with 10 g/m2 PP nonwoven fabric and the content of lithium salt was 20 wt %. Furthermore, PAEPU/PP10-CPE@20 exhibited the highest electrochemical stability with an electrochemical window value of 5.53 V. Moreover, the capacity retention rate of the Li//PAEPU/PP10-CPE@20//LiFePO4 half-cell was 96.82% after 150 cycles at 0.05 C and 60 °C, and the capacity recovery rate in the rate test reached 98.81%.

Quasi-Solid-State Na-O2 Battery with Composite Polymer Electrolyte.

Na-O2 batteries have emerged as promising candidates due to their high theoretical energy density (1,601 Wh kg-1), the potential for high energy storage efficiency, and the abundance of sodium in the earth's crust. Considering the safety issue, quasi-solid-state composite polymer electrolytes are among the promising solid-state electrolyte candidates. Their higher mechanical toughness provides superior resistance to dendritic penetration compared with traditional liquid electrolytes. The flexibility of the composite polymer electrolyte matrix allows it to conform to various battery configurations and considerably reduces safety concerns related to the combustion risks associated with conventional liquid electrolytes. In this study, we employed poly(ethylene oxide) (PEO) and sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as the polymer matrix and sodium ion-conducting agent, respectively. We incorporated nanosized NZSP (25 wt %) to create the composite polymer electrolyte membrane. This CPE design facilitates ion conduction pathways through both sodium salt and NZSP. By utilizing a liquid electrolyte infiltration method, we successfully enhanced its ionic conductivity, achieving an ionic conductivity of 10-4 S cm-1 at room temperature.

A-LLTO Nanoparticles Embedded Composite Solid Polymer Electrolyte for Room Temperature Operational Li-metal Batteries.

Solid-state batteries (SSBs) have the potential to revolutionize the current energy storage sector. A significant portion of the current development of electric vehicles and the electrification of various appliances relies on Lithium (Li)-ion batteries. However, future energy demands will require the development of stronger and more reliable batteries. This report presents a novel solid state electrolyte (SSE) composed of a self-healing composite solid polymer electrolyte (CSPE) matrix and aluminum-doped (Li0.33La0.56)1.005Ti0.99Al0.01O3 (A-LLTO) nanofillers. The CSPE contains Jeffamine ED-2003 monomer, Benzene-1,3,5-tricarbaldehyde (BTC)crosslinker dissolved in a 1:1 ratio of Dimethylformamide (DMF) to LiPF6, and a certain amount (x) of A-LLTO nanofillers (x=5, 7.5, 10, 12.5%). A CSPE containing x-amount of A-LLTO fillers (referred to as CAL-x%) demonstrates excellent ion-conducting properties and stable battery performance. The CAL-10% demonstrates 1.1×10-3Scm-1 of ionic conductivity at room temperature (RT). A-LLTO nanofillers dispersed uniformly within the polymer matrix form a percolation network, which is believed to improve ionic conductivity and the diffusion of Li+ ions. The CR-2032 cell, consisting of LiFePO4 (LFP)║CAL-10%║Li, at RT offers an initial discharge capacity of ≈165mAhg-1 at 0.1C rate for 120 cycles with 98.85% coulombic efficiency (C.E.).

Dynamic Covalent Amphiphilic Polymer Conetworks Based on End-Linked Pluronic F108: Preparation, Characterization, and Evaluation as Matrices for Gel Polymer Electrolytes.

We present the development of a platform of well-defined, dynamic covalent amphiphilic polymer conetworks (APCN) based on an α,ω-dibenzaldehyde end-functionalized linear amphiphilic poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG-b-PPG-b-PEG, Pluronic) copolymer end-linked with a triacylhydrazide oligo(ethylene glycol) triarmed star cross-linker. The developed APCNs were characterized in terms of their rheological (increase in the storage modulus by a factor of 2 with increase in temperature from 10 to 50 °C), self-healing, self-assembling, and mechanical properties and evaluated as a matrix for gel polymer electrolytes (GPEs) in both the stretched and unstretched states. Our results show that water-loaded APCNs almost completely self-mend, self-organize at room temperature into a body-centered cubic structure with long-range order exhibiting an aggregation number of around 80, and display an exceptional room temperature stretchability of ∼2400%. Furthermore, ionic liquid-loaded APCNs could serve as gel polymer electrolytes (GPEs), displaying a substantial ion conductivity in the unstretched state, which was gradually reduced upon elongation up to a strain of 4, above which it gradually increased. Finally, it was found that recycled (dissolved and re-formed) ionic liquid-loaded APCNs could be reused as GPEs preserving 50-70% of their original ion conductivity.

Rapid ion conduction enabled by synergism of oriented liquid crystals and Electron-Deficient boron atoms in multiblock copolymer electrolyte for advanced Solid-State Lithium-Ion battery

Liquid crystals (LCs) with characteristics of self-orientation have exhibited superiorities in construction of ordered ion channels for rapid Li-ion transport. Herein, reversible addition-fragmentation chain transfer (RAFT) polymerization is employed to synthesize a unique type of boron-containing LCs based ABCBA type multiblock copolymers for the first time. The composite block copolymer electrolytes (BCPEs) are fabricated by introducing the copolymer electrolytes into glass fiber separator via solution-casting method. Noteworthily, LCs can not only provide ordered ion channels for efficient ion conduction, but also ameliorate the mechanical strength. Meanwhile, the nitrile groups with high polarity from LCs are able to further facilitate lithium salt dissociation and reinforce electrochemical stability of the system. Crucially, boron elements with electron deficiency can anchor anions and adsorb impurities to endow BCPEs with boosted ion transport capability and sufficient electrochemical stability. Consequently, the well-designed electrolyte shows high ionic conductivity of 1.13 × 10−4 S cm−1 (30 °C), and broadened electrochemical stability window of 4.85 V. Impressively, the assembled Li/LiFePO4 cells and even Li/LiMnxFe1-xPO4 high-voltage cells exhibit remarkable performances. This work provides a synthetic strategy of structure-controlled polymer electrolyte matrix and illustrates that the BCPEs are definitely a category of satisfactory electrolyte candidate for high-performance solid-state lithium-ion batteries.

Low-cost and high-safety montmorillonite-based solid electrolyte for lithium metal batteries

Composite solid-state electrolyte have good interfacial compatibility and mechanical properties, but their safety (such as easy to catch fire) and economic cost are still problems. In present work, an composite solid-state electrolyte was prepared by inserting poly(vinylidene fluoride)-based polymer electrolyte matrix into the interlayer of a low cost clay mineral-montmorillonite. The composite electrolyte exhibited remarkable characteristics, including excellent flame retardancy, high room temperature ionic conductivity of 2.28 × 10−4 S cm−1, wide electrochemical stability window of 4.8 V, high lithium-ion transference number of 0.57 and good mechanical strength of 12.58 MPa. Furthermore, LiFePO4-based solid-state battery, utilizing this composite solid-state electrolyte, exhibited stable cycling with discharge specific capacity of 130 mAh g−1 for over 100 cycles at a rate of 0.5C at room temperature. This successful performance demonstrated the potential of utilizing low-cost and environmentally friendly raw clay mineral materials in high energy density solid-state battery applications.

Fluorinated Graphene Fillers for High-Performance Solid-State Lithium Batteries

Solid-state batteries (SSBs) are expected to revolutionize the field of energy storage due to their superior safety and high energy density, which result from the use of lithium metal as the negative electrode. However, the development of solid-state electrolytes (SSEs), the key component of SSBs, is quite crucial. SSEs have high thermal stability, high mechanical strength, and a wide electrochemical window but lack enough ionic conductivity; which is one of the most challenging aspects. Incorporating suitable active or inert fillers in the solid polymer electrolyte matrix is one of several methods adopted to improve the ionic conductivity of pure polymer SSEs. Two-dimensional graphene-based fillers are a promising option as they provide a high surface area for creating an abundant interface with the polymer matrix creating a continuous pathway for lithium-ion transport and simultaneously their robust nature improves the mechanical strength of the electrolyte. Pristine graphene is electronically conducting in nature owing to the continuous sp2 carbon linkages, but the electronic conductivity can be suppressed by disrupting the sp2 bonds by heteroatom functionalization on the graphene. This study investigates the heteroatom functionalization of graphene to obtain various graphene-based fillers such as graphene oxide (GO), reduced graphene oxide (rGO), and fluorinated graphene oxide (FGO) and their effectiveness when introduced into a polymer SSE matrix for LiNi0.8Co0.1Mn0.1O2-based SSBs. FGO filler outperforms others in terms of ionic conductivity, thermal stability, enhanced electrochemical potential window, and compatibility of the SSE. The optimized ratio of FGO fillers in SSE demonstrates excellent electrochemical performance, enabling long-term Li plating/stripping with small overpotential and stable cycling of Li/ LiNi0.8Co0.1Mn0.1O2 full cells. This work highlights the notable potential of FGO materials in improving the comprehensive properties of polymer SSEs and promoting the applications of polymer SSEs in high-performance SSBs.

Gelatin network reinforced poly (vinylene carbonate-acrylonitrile) based composite solid electrolyte for all-solid-state lithium metal batteries

Solid polymer electrolyte (SPE) has become one of the most promising candidate materials for building solid-state lithium batteries because of its excellent flexibility, expansibility and good interface compatibility with electrodes. However, SPE still has some problems such as low ionic conductivity at room temperature and narrow electrochemical window. Therefore, it is of great significance to develop polymer solid electrolyte with new structure to improve the comprehensive performance of the battery. In this work, Poly (vinylene carbonate-acrylonitrile) (PVN) was selected as the matrix of polymer electrolyte, and the network structure filled with biomass material gelatin was used as the skeleton. The composite solid polymer electrolyte (CSPE) composed of PVN, lithium bis (trifluoromethyl) sulfonimide (LiTFSI) and gelatin was prepared by simple solution casting method. The constructed PVN/LiTFSI/Gelatin (PLG) electrolyte has excellent ionic conductivity (3.47 × 10−4 S cm−1 at 60 °C) and wide electrochemical window (4.3 V). Li|10 %PLG CSPE|LiFePO4 battery has a capacity retention rate of 85 % after 1000 cycles of stable operation at 1C rate at 60 °C, and has excellent cycle performance and life. In addition, a low interface resistance enables highly reversible Li|Li symmetrical battery has a stably cycle of 1500 h at 0.1 mA cm−2 and has good interface compatibility. Therefore, PLG CSPE composite is a simple and effective strategy to obtain high-performance lithium batteries, which can realize the ultra-stable operation of solid lithium metal batteries.

Improving electrolyte performance: Nanocomposite solid polymer electrolyte films with cobalt oxide nanoparticles

AbstractThe present work gives an insight into the structural, thermal, and electrical analysis of novel nanocomposite solid polymer electrolyte films prepared using the solution casting technique by incorporating cobalt oxide nanoparticles into methyl cellulose‐magnesium acetate polymer electrolyte matrix. The impact of ceramic oxide on the complexation of the salt with the polymer chain is evident from FTIR analysis. The crystallinity of the electrolyte systems decreases upon the incorporation of nanofiller into the matrix. Electrochemical Impedance Analysis of the samples shows enhancement in the conductivity of the electrolytes. Nanocomposite electrolyte systems with 2 wt% (5.93 × 10−4 S/cm) and 3 wt% (5.77 × 10−4 S/cm) of cobalt oxide exhibit maximum room temperature ionic conductivity compared to other electrolyte systems. DSC thermogram reveals the creation of free volume in the matrix with the incorporation of the filler. A primary battery is fabricated using the nanocomposite electrolyte system with 3 wt% of the nanofiller, and its open circuit potential and discharge characteristics have been analyzed.Highlights Novel nanocomposite SPEs with cobalt oxide were prepared via solution casting. FTIR and XRD studies revealed modification in the microstructure. Cobalt oxide incorporation enhanced ionic conductivity of SPE. A primary battery fabricated using the highest conducting SPE.

Introduction of Al(III)‐Ion‐Based Solid Polymer Electrolyte Material for Energy Storage Device Applications

AbstractSolid phase electrolyte system PVIm‐R‐PEG‐AlCl3 is introduced for Al(III) ion‐based energy storage material. Here, we introduced [AlCl3Br]− counter anion system with N‐octyl‐polyvinyl imidazolium polymer matrix supported by PEG. Electrolyte material shows good thermal stability with a Glass transition temperature (Tg~148 °C), which provides a good working temperature range for material processing. PVIm‐R‐PEG‐AlCl3 shows electrochemical stability of 1.5 V and red‐ox properties, it has 96 % of ionic conduction against the Al metal. The conductivity of electrolyte material is found in the range of 10−5 S/cm at room temperatures and 10−4 S/cm at higher temperature (>40 °C). The polymer electrolyte matrix shows the mobility of 1.37×10−6 m2/Vs and drift ionic velocity of 3.42×10−4 m/s at 30 °C. The ionic movement of Al(III) ions inside the matrix follows correlated type hopping with the activation energy of 0.266 eV. This Al(III) ion‐based solid polymer electrolyte (SPE) is associated with a large amount of capacitance with a tiny electrode contribution.

(Invited) Ion Transport and Interface Resistance in Polymer-Based Composite Electrolytes and Composite Cathode

Solid-state electrolytes are promising to enable the next generation batteries with higher energy density and improved safety. However, each major class of solid electrolytes has intrinsic weaknesses. By combining different classes of solid electrolytes, such as a polymer electrolyte and an oxide ceramic electrolyte, one can potentially overcome the intrinsic weaknesses of each component and develop a composite electrolyte to achieve high ionic conductivity, good mechanical properties, good chemical stability, and adhesion with the electrodes.In this presentation, we show that the interfacial resistance strongly affects the ionic conductivity of polymer/oxide ceramic composite electrolytes, in both the ceramic-in-polymer design where ceramic particles are dispersed within the polymer electrolyte matrix as well as the polymer-in-ceramic design where a three dimensionally interconnected ceramic scaffold is developed. The quantification of the interfacial resistance, the origin of this resistance, as well as the strategies to minimize it are discussed.In a second case, we examine the effect of interfaces on ion transport in a polymer based composite cathode consisting of LiFePO4 (LFP), carbon and poly(ethylene oxide) (PEO) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The structure and dynamics of PEO and lithium ion mobility are studied by small angle neutron scattering and quasi-elastic neutron scattering. The results show that Li ion mobility in PEO/LiTFSI in the composite cathode is only 30% of the bulk electrolyte. This suggests a key bottleneck that limits the rate performance of polymer-based solid-state batteries originates from the sluggish ion transport in the polymer electrolyte confined in the cathode.

Construction of High-Strength Flame-Retardant Li-SPEEK-Modified PEG Gel Polymer Electrolytes for Lithium Batteries

The low mechanical performance and high flammability of gel polymer electrolytes limit their application. Here, we prepare a high-strength and nonflammable polymer Li-SPEEK (lithium sulfonated polyetheretherketone) to modify PEG (polyethylene glycol) and construct a PEG-Li-SPEEK cross-linked network as a polymer electrolyte matrix, with an overall improvement in electrochemical performance, mechanical properties, and flame retardancy. The PEG-Li-SPEEK-ls (PEG-Li-SPEEK cross-linked network after gelation of the liquid electrolyte) electrolyte achieves a conductivity of 1.62 × 10–4 S·cm–1 at 30 °C, a wider electrochemical window of 4.5 V vs Li+/Li, and a higher lithium-ion transference number compared to the PEG-ls electrolyte. The excellent mechanical properties allow the symmetric cell-containing PEG-Li-SPEEK-ls electrolyte to exhibit better cycling performance for over 300 h at a current density of 0.2 mA·cm–2. The LFP/PEG-Li-SPEEK-ls/Li cells deliver a maximum discharge capacity of 142.1 mAh·g–1 with a capacity retention of 98.1% after 50 cycles at 0.5 C and the Coulombic efficiency remains above 99.5% throughout the cycling process. In addition, the good carbon formation properties of Li-SPEEK give the electrolyte matrix satisfactory flame-retardant properties. Thus, we validate the excellent performance of Li-SPEEK for modifying conventional polymer electrolytes and improving their mechanical, electrochemical, and flame-retardant properties.

Boronic Ester Transesterification Accelerates Ion Conduction for Comb-like Solid Polymer Electrolytes

Polyether is a kind of ideal polymer matrix for solid polymer electrolytes (SPEs), but its inherent drawbacks (such as the semi-crystalline nature and strong complexation of lithium ions) still hinder their commercial application. The construction of comb-like SPEs effectively increases their functionalities and improves the comprehensive performance. Herein, we apply a dynamic boronic ester exchange strategy to simultaneously enhance the lithium-ion conduction and self-healing ability of the SPEs, thus effectively solving the current problems of polyether. The copolymer (GPA) containing side chains with poly(ethylene glycol) (PEG) and diol groups was obtained through reversible addition–fragmentation chain-transfer (RAFT) polymerization and hydrolysis, and PBA-M2070 containing the boronic acid group and flexible polyether segments was obtained via Schiff base reaction. Boronic ester bonds were formed by dehydration of the diol groups of GPA and the boronic acid groups of PBA-M2070. Dynamic exchange of the boronic ester bonds at the branched sites enhanced the side-chain motion, thus increasing the self-healing ability and electrochemical performance of the SPEs, as well as the cycling stability of assembled batteries. Benefiting from the dynamic boronic ester exchange and enhanced side-chain mobility, the SPEs exhibited self-healing within 10 min and an ionic conductivity of 1.58 × 10–5 S cm–1 at 30 °C. The assembled lithium metal batteries (LMBs) were operated stably at 0.5C for 300 cycles. The dynamic boronic ester exchange strategy used to enhance the LMBs properties provides new insight into the design of comb-like polymer electrolytes.

Ion Transport and Dielectric Studies on [PEO:TiO2]:NH4SCN Nanocomposite Polymer Electrolytes

AbstractAn improvement in ion transport behavior and dielectric properties of polyethylene oxide based polymer electrolytes have been investigated upon the dispersal of TiO2 nanoparticles. TiO2 nanoparticle is synthesized with the help of well‐known sol–gel technique. The different compositions of polymer electrolyte systems are prepared by the solution cast technique. Nanocomposite polymer electrolytes (NCPEs) films are synthesized by loading of nanoTiO2 particle in a pristine polymer electrolyte matrix. The structural and morphological behaviors of nanocomposite polymer electrolytes (NCPEs) have been subsequently characterized by XRD and SEM studies. The ionic behavior of synthesized NCPEs is ascertained by Wagner's polarization technique. AC and DC conductivity of polymer electrolyte films have been carried out using impedance spectroscopic techniques. Dielectric relaxation studies of polymer electrolytes are examined using impedance spectroscopic data. The conductivity relaxation mechanism of NCPEs has been concluded with the help of modulus formalism. DC conductivity of best ion‐conducting NCPEs at room temperature has been found to σ = 2.5 × 10−5 S cm−1. The electrode polarization effect has completely vanished in the dielectric and modulus formalism and the conductivity scaling data show a single master curve observed in ion dynamics. The change in ionic conductivity with frequency and temperature is studied by impedance spectroscopic investigations. The effect of salt on dielectric parameters of NCPEs is also extracted from impedance spectroscopic data to explore underlying ion dynamics.

In Situ Polymerization of Fluorinated Polyacrylate Copolymer Solid Electrolytes for High-Voltage Lithium Metal Batteries at Room Temperature

Poly(ethylene oxide) is a promising solid polymer electrolyte (SPE) matrix. However, its low ionic conductivity, narrow electrochemical window, and sluggish interfacial charge transfer limit its use in solid-state batteries at room temperature. Herein, we report the in situ polymerization of poly(2,2,3,4,4,4-hexafluorobutyl acrylate-copolymer-2-(2-(2-methoxyethoxy) ethoxy)ethyl acrylate) (P(HFBA-co-MEA)) with lithium bis(trifluoromethane sulfonamide) (LiTFSI) to form a fluorinated SPE (P(HFBA-co-MEA)/LiTFSI). When the molar ratio of HFBA to MEA is 1:1, P(HFBA1:1-co-MEA) exhibits a lower lithium-ion absorption energy (−4.602 eV) than that of PMEA (−4.372 eV), providing a fast transport pathway for lithium ions. The electron-absorbing properties of the −C–F group can reduce the lone-pair electron density around the ether-oxygen group and increase the electrochemical window of P(HFBA1:1-co-MEA)/LiTFSI to 4.9 V. In addition, P(HFBA1:1-co-MEA)/LiTFSI demonstrates excellent compatibility with lithium anodes, and the Li|P(HFBA1:1-co-MEA)/LiTFSI|LiNi0.5Co0.3Mn0.2O2 battery has a capacity retention of 62.3% after 170 charge–discharge cycles at 0.1C.