Polymer Electrolytes For Lithium Ion Batteries Research Articles

Photocured Cationic Polyoxazoline Macromonomers as Gel Polymer Electrolytes for Lithium-Ion Batteries

In this work, we present a cationic vinylimidazolium-terminated poly(2-ethyl-2-oxazoline) (PEtOx) macromonomer as a key component of gel polymer electrolytes (GPE) for lithium-ion batteries. GPE production followed a scalable process based on UV curing of the cationic PEtOx macromonomer with polyfunctional acrylic comonomers dissolved in an organic electrolyte (LP30), affording electrolyte-swollen polymeric ionic liquid (PIL) networks with PEtOx side chains. Thus, cathodes coated with a GPE layer of less than 200 μm thickness were readily manufactured. The PIL brush-type GPE is highly insoluble but swellable in LP30 and exhibits pronounced electrolyte retaining ability against evaporation. At 160 °C, the weight loss of the GPE amounted to around 5%. This is 12% less compared to an LP30-soaked commercial Celgard separator. At room temperature, the ionic conductivity was 3.6 × 10–4 S/cm, surpassing that of a comparable Celgard/LP30 system. Contrary to LP30 in Celgard, conductivity measurements for the PIL brush GPE did not indicate any crystallization of the liquid electrolyte at subambient temperatures. This was confirmed by differential scanning calorimetry, suggesting improved ionic mobility in the GPE over a wide temperature range. The electrochemical stability window of the PIL brush GPE is wide enough and fits all common lithium-ion cathode materials. In fact, the GPE exhibited exceptional oxidative stability of 5.2 V vs Li/Li+. Half-cell cycling experiments using a lithium iron phosphate cathode revealed high capacity values of 150 mAh/g at a current rate of C/10. When the current was increased to C/2, the capacity decreased to 120 mAh/g and the cell reached 80% of its initial capacity (referred to C/2) after 180 cycles. Thus, according to the first physicochemical and electrochemical investigations, the PEtOx-based PIL brush GPE represents a promising candidate with respect to lithium-ion battery operation.

Plasticized 3D-Printed Polymer Electrolytes for Lithium-Ion Batteries

In the current research, we developed and printed by fused-filament fabrication polylactide-polyethylene-oxide blended membranes. The influence of relative content of polymers on the ease of extrusion and printing processes was studied. Ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethane-sulfonyl)imide (Pyr14TFSI) with dissolved LiTFSI salt was infused into the membranes to produce free-standing films of quasi-solid polymer electrolytes. The printed membranes were characterized by ESEM, DSC, XPS, NMR and EIS methods. Neat-printed PLA (polylactide) membrane exhibited poor wetting and low uptake of ionic liquid. However, the XPS tests of 3D-printed PLA-PEO membrane infused with LiTFSI solvated ionic liquid show evidence of the interaction between lithium cations with both, PEO (polyethylene oxide) and PLA. The measurements of diffusion coefficients by PGSE-NMR suggest that the Li+ ions are coordinated by the PEO segments in the polymer blend. Increase of the PEO content at the expense of PLA polymer, leads to more than one order of magnitude improvement of bulk conductivity, approaching 0.2 mS cm−1 at 60

Electrochemical behavior of BaTiO3 embedded spongy PVDF-HFP/cellulose blend as a novel gel polymer electrolyte for lithium-ion batteries

Herein, a microporous poly(vinylidene fluoride co-hexafluoropropylene)/cellulose/ BaTiO3 membrane with a sponge-like architecture has been prepared by spinning cum immersion precipitation route followed by hydrolysis with lithium hydroxide for the deacetylation of cellulose acetate. The fabricated composite membrane-based LiFePO4|Li cell achieves a high ionic conductivity of 1.36 mS cm−1 at 30 °C. Additionally, the electrochemical system exhibits a good discharge capacity of 150.1 mAh g−1 and excellent cycling stability with a capacity retention of 95% after 200 cycles at a 0.1C rate. The transference number of the system is computed to be 0.51. According to these findings, the proposed gel polymer electrolytes have a great potential for use in lithium-ion batteries.

Solvent-Free Procedure to Prepare Ion Liquid-Immobilized Gel Polymer Electrolytes Containing Li0.33La0.56TiO3 with High Performance for Lithium-Ion Batteries.

Based on the advantages of intrinsic safety, flexibility, and good interfacial contact with electrodes, a gel polymer electrolyte (GPE) is a promising electrolyte for lithium-ion batteries, compared with the conventional liquid electrolyte. However, the unstable electrochemical performance and the liquid state in a microscale limit the commercial application of GPE. Herein, we developed a novel gel polymer electrolyte for lithium-ion batteries by blending methyl methacrylate (MMA), N-butyl-N-methyl-piperidinium (Pyr14TFSI), and lithium salts in a solvent-free procedure, with SiO2 and Li0.33La0.56TiO3 (LLTO) additives. The prepared MMA-Pyr14TFSI-3 wt % LLTO electrolyte shows the best electrochemical performance and obtains a high ion conductivity of 4.51 × 10–3 S cm–1 at a temperature of 60 °C. Notably, the electrochemical window could be stable up to 5.0 V vs Li+/Li. Moreover, the batteries with the GPE also show excellent electrochemical performance. In the LiFePO4/MMA-Pyr14TFSI-3 wt % LLTO/Li cell, a high initial discharge capacity was achieved 150 mA h g–1 at 0.5C with a Coulombic efficiency over 99% and maintaining a good capacity retention of 90.7% after 100 cycles at 0.5C under 60 °C. In addition, the physical properties of the GPE have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) measurements, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetry (TG).

Exploring the Ion Solvation Environments in Solid-State Polymer Electrolytes through Free-Energy Sampling

The success of poly(ethylene oxide) (PEO) in solid-state polymer electrolytes for lithium-ion batteries is well established. Recently, in order to understand this success and to explore possible alternatives, we studied polyacetal electrolytes to deepen the understanding of the effect of the local chemical structure on ion transport. Advanced molecular dynamics techniques using newly developed, tailored interaction potentials have helped elucidate the various coordination environments of ions in these systems. In particular, the competition between cation–anion pairing and coordination by the polymer has been explored using free-energy sampling (metadynamics). At equivalent reduced temperatures, with respect to the polymer-specific glass-transition temperature, two-dimensional free-energy plots reveal the existence of multiple coordination environments for the lithium (Li) ions in these systems and their relative stabilities. Furthermore, we observe that the Li-ion movement in PEO follows a serial, stepwise pathway when moving from one coordination state to another, whereas this happens in a more continuous and concerted fashion in a polyacetal such as poly(1,3-dioxalane) [P(EO-MO)]. The implication is that interconversion between coordination states of the Li ions may be easier in P(EO-MO). However, the overarching observation from our free-energy analysis is that Li-ion coordination is dominated by the polymer (in either case) and contact-ion pairs are rare. We rationalize the observed higher increase in glass-transition temperature (Tg) with salt loading in polyacetals as due to intermolecular Li-ion coordination involving multiple polymer chains, rather than just one chain for PEO-based electrolytes. This interchain coupling in the polyacetals, resulting in the higher Tg, works against any gains due to variations in Li-ion coordination that might enhance transport processes over PEO. Further research is required to overcome the interdependence between local coordination and macroscopic properties to compete with PEO electrolytes at the same absolute working temperature.

Nanostructured Polymer Electrolytes for Lithium-Ion Batteries

Nanostructured Polymer Electrolytes for Lithium-Ion Batteries

Agent molecule modulated low-temperature activation of solid-state lithium-ion transport for polymer electrolytes

Low-temperature activation of lithium-ion migration is crucial for enabling the practical application of solid-state polymer electrolytes for lithium-ion batteries. In this study, we perform a series of first-principle calculations and demonstrate that certain types of neutral molecules (so-called agent molecules) accelerate solid-state lithium-ion migration when mixed with lithium salts. We find that the intermolecular interaction in a selected agent-molecule/lithium-salt binary system is governed by the strong coupling between lithium and oxygen atoms. Upon the addition of agent molecules, the anionic species surrounding the lithium of lithium salts is replaced by the agent molecules. The resulting weakened Coulomb energy coupling between lithium and oxygen atoms is determined to be a key factor in enabling fast lithium-ion migration via facile dissociation of lithium salts and subsequent formation of ion-hopping sites in the form of lithium-free oxygen-cages. The structure-based interpretation of agent molecules suggests that neutral molecules with functional groups which enhance chemical resonance can be selected as potential agent molecules. We believe that the results obtained in this study serve as a theoretical basis for the future development of solid-state polymer electrolytes, particularly toward mitigating the dependence of lithium-ion transport on the movement of polymer chains.

Transport of Propylene Carbonate-LiTFSI Electrolytes in P(VDF-HFP) Using Time-resolved ATR-FTIR Spectroscopy: Diffusion Coefficients and Molecular Interactions

The time-resolved attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is employed to investigated the transport mechanism of gel electrolytes by monitoring the diffusion behavior of propylene carbonate-lithium bis(trifluoromethylsulfonyl)imide (PC-LiTFSI) solution through poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) films. Fickian behavior has been observed for both TFSI- and PC. Higher temperature leads to faster diffusion of TFSI- and PC, which could be related to the increased free volume in P(VDF-HFP) matrix and rapid molecular movements upon heating. Various molecular interactions among LiTFSI, PC and P(VDF-HFP) have been recognized. During the diffusion process, PC molecules, in the form of small clusters, can firstly diffuse through the P(VDF-HFP) film and interact with P(VDF-HFP) by dipole-dipole interaction, acting as the plasticizer. Then, Li+ diffuses into P(VDF-HFP) with the help of ion-dipole interactions between Li+ and C=O of PC. Meanwhile, TFSI- diffuses through the polymer matrix in solvation states. In addition, slight ion-dipole interactions between Li+ and P(VDF-HFP) have been observed as well. Results in this work contribute to a better understanding of transport process in gel polymer electrolytes for lithium-ion batteries and support the development of improved gel polymer electrolytes by rationally regulating molecular interactions.

Water Domain Enabled Transport in Polymer Electrolytes for Lithium-Ion Batteries

Widespread commercial adoption of polymer electrolytes for lithium-ion batteries has been hindered by subpar transport properties, namely, ionic conductivities of <1 mS/cm at room temperature and s...

Lithium bis(trifluoromethanesulfonyl)imide blended in polyurethane acrylate photocurable solid polymer electrolytes for lithium-ion batteries

The increased demand of electronic devices promotes the development of advanced and more efficient energy storage devices, such as batteries. Lithium-ion batteries (LIBs) are the most studied battery systems due to their high performance. Among the different battery components, the separator allows the control of lithium ion diffusion between the electrodes. To overcome some drawbacks of liquid electrolytes, including safety and environmental issues, solid polymer electrolytes (SPEs) are being developed. In this work, a UV photocurable polyurethane acrylate (PUA) resin has been blended with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) up to 30 wt% LiTFSI content to reach a maximum ionic conductivity of 0.0032 mS/cm at room temperature and 0.09 mS/cm at 100 °C. Those values allowed applying the developed materials as photocurable SPE in Swagelok type Li/C-LiFePO4 half-cells, reaching a battery discharge capacity value of 139 mAh.g−1 at C/30 rate. Those results, together with the theoretical studies of the discharge capacity at different C-rates and temperatures for batteries with LiTFSI/PUA SPE demonstrate the suitability of the developed photocurable SPE for LIB applications.

Preparation and characterisation of chitosan extracted from shrimp shell (Penaeus monodon) and chitosan-based blended solid polymer electrolyte for lithium-ion batteries

A bioactive and non-toxic biopolymer-based electrolyte has gained attention in recent research for their potential applications in the fabrication of electrochemical devices. In this work, we extracted the chitosan successfully prepared from shrimp shells using Brine’s method. The solid polymer electrolyte comprising the blend of chitosan and agar–agar, plasticised with polyethylene glycol (PEG), as host polymer and lithium perchlorate (LiClO4) as a dopant is prepared by solution casting technique. Also, the effect of different weight percentage of the plasticiser PEG at a fixed ratio of perchlorate content is investigated. The obtained chitosan blended film is highly suitable as a electrolyte for electrochemical devices. The prepared polymer electrolyte is characterised using attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR), high-resolution scanning electron microscopy (HR–SEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy. The ATR–FTIR spectroscopy confirms the presence of particular functional groups present in chitosan and complex formation between blended polymers and lithium perchlorate. The surface morphology and amorphous crystallinity of chitosan and blended polymer electrolytes revealed from HR–SEM and XRD analysis. The ionic conductivity of the prepared materials is studied using AC impedance spectroscopy and compared. The highest ionic conductivity at room temperature obtained for the sample is 4.56 × 10−4 Scm−1 (CAP3). The mechanical properties of films have been studied using a Universal testing machine analysis. Wagner’s polarisation measurements have estimated the Li+ transport numbers of SPEs. Linear sweep voltammetry was performed on half-cell method to study the electrochemical stability window of the maximum ionic conductivity of SPEs.

Литий-ионды аккумуляторларға арналған полимерлі электролиттермен үш өлшемді құрылымды жабу әдістері

The paper considers various methods of conformal coating the three-dimensional structure of Ni foam with polymers as electrolytes in lithium-ion batteries. Polymethylmethacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and polyethylene oxide (PEO) were chosen as polymer electrolytes because of their good ionic conductivity and mechanical stability. Conformal coating was performed using two methods: drop coating, dip coating. The polymer-coated three-dimensional Ni foams were characterized by field-emission scanning electron microscopy (FE-SEM) to determine the more conformal coating method and testing the ionic conductivity of polymers. From this research, it could be concluded that the dip coating method allows a more conformal coating of the three-dimensional Ni foam structure and the polymers obtained by this method have a good value of ionic conductivity.

Synthesis and molecular dynamic simulation of a novel single ion conducting gel polymer electrolyte for lithium-ion batteries

Single ion conductor has been realized as a new path to reduce polarization and improve electrochemical performance of the lithium ion batteries (LIBs). In this work, a novel single ion conductor gel polymer electrolyte (SIGPE) was designed via free radical polymerization, co-electrospinning and plasticizing process. The molecular structure information of the single ion polyanionic salt P(MPEGA-AMPSLi) of the SIGPE is carefully verified. The SIGPE shows high ionic conductivity of around 2.8 × 10−5 S/cm at 25 °C, high lithium ion transference number of 0.75, wide electrochemical window of 4.7 V as well as a stable cycle performance at 25 °C and 60 °C. The plasticizing mechanism of the gel polymer electrolyte has also been modeled and studied theoretically by molecular dynamics simulation. The results display a positive effect of the plasticizing in promoting the ionization of Li ions, increasing the diffusion coefficient of Li ions from 8.05 × 10−11 cm2/s to 1.37 × 10−9 cm2/s.

Ionic liquid crystal induced morphological control of solid composite polymer electrolyte for lithium-ion batteries

A novel two-dimensional (2D) solid composite polymer electrolyte (SPE) was synthesized by co-assembling ionic liquid crystals [1-hexadecyl-3-methyl tetrafluoroborate ([C16mim]BF4)] and polycationic liquids [1-(hexyl methacrylate)-3-butyimidazolium tetrafluoroborate (PMOBIm-BF4)] along with the imidazolium moieties using a flexible spacer. Ionic liquid crystals were used to induce ion-conductive 2D pathways in the ionic liquid cationic polymer, and polymer cationic ionic liquids acted as ion-conductive media for lithium-ion batteries. Owing to its excellent thermal stability, non-inflammability, and high ionic conductivity, the PMPC0.5 electrolyte containing 3/1/0.5 ratio of polyMOBIm-BF4/PEGDA/[C16mim]BF4 exhibited anenhanced lithium-storage performance within a wide electrochemical window of up to 4.2 V vs. Li+/Li, and high ionic conductivity of 7.14 × 10−5 and 2.17 × 10−3 S cm−1 at 25 and 95 °C, respectively. The assembling ability of ionic liquid crystals can not only develop lamella structure and ordered channel for improved Li-ion transportation, but also could show efficient enhancement for ionic conductivity of the polyionic liquid. The Li/SPE/LiFePO4 coin cells using the PMPC0.5 as electrolyte delivered a specific capacity of 136.7 mAh g−1 in the first cycle and118.9 mAh g−1 in the 40th cycle at a rate of 0.1C.

A renewable and biodegradable nanocellulose-based gel polymer electrolyte for lithium-ion battery

Polymers, such as PVDF and PMMA, have been commonly adopted as host materials for gel polymer electrolytes (GPEs), leading to excessive consumption of fossil fuel as well as severe white pollution. Nanocellulose (NC) is a kind of renewable and biodegradable carbohydrate polymer so that its possible application in gel polymer electrolyte for lithium-ion battery is discussed in this paper. The NC membrane with a porous network is prepared by freeze-drying method. To further extend its application into GPE, glutaraldehyde (GA) is used as cross-link agent to enhance the performance of the membrane. Cross-linked by 6 wt% GA, the skeleton membrane exhibits satisfactory mechanical property and thermal stability. The GPE gives moderate electrochemical performance and reverse capability. The experimental results show that the introduction of nanocellulose provides a direction for the development of carbohydrate polymer applied in GPE.

High-performance gel polymer electrolytes using P(VDF-HFP) doped with appropriate porous carbon powders as the matrix for lithium-ion batteries

Porous carbon powders are prepared from raw material camellia oleifera shells by ball milling and pyrolysis processes. Poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)-based gel polymer electrolytes (GPEs) doped with different proportions of porous carbon powders are successfully fabricated using a classical inverse phase method, which is confirmed by X-ray diffraction, thermo-gravimetric analysis, and field emission scanning electron microscope. The results show that the porous GPE-3 membrane has a high liquid uptake ratio of about 104.3%, a high decomposition temperature of 435 °C, a rapidly stabilized interface impedance to 517.6 Ω after 5 days storage time, and a high ionic conductivity of 3.921 mS cm−1 at room temperature when the doping amount of porous carbon powders is 3.0 wt%. Furthermore, the assembled LiCoO2/GPE-3/Li coin cells can deliver a high initial discharge specific capacity of 152.7 mAh g−1 and an excellent initial coulombic efficiency of 97.27% at 0.1 C. These good properties indicate that the as-prepared GPE-3 can be used as a potential polymer electrolyte for lithium-ion batteries.

Cellulose Microcrystals with Brush-Like Architectures as Flexible All-Solid-State Polymer Electrolyte for Lithium-Ion Battery

Development of cellulose-based electrolytes can strongly reduce the cost of energy storage devices. However, the prepared cellulose-based electrolytes use high contents of liquid electrolytes, sacr...

Molecular Brush with Dense PEG Side Chains: Design of a Well-Defined Polymer Electrolyte for Lithium-Ion Batteries

Herein, we designed a series of well-defined bottlebrush-like macromolecules with short and densely grafted poly(ethylene oxide) (PEO) side chains through several controlled radical polymerization ...

Preparation and characterization of polypropylene supported electrospun POSS-(C3H6Cl)8/PVDF gel polymer electrolytes for lithium-ion batteries

Polyhedral oligomeric silsesquioxane has been successfully employed as organic-inorganic hybrid material in various potential applications for its good compatibility, thermal and mechanical stability. Commercial polypropylene (PP) separator supported gel polymer electrolyte (GPE) incorporating with polyhedral oligomeric silsesquioxane-chloropropyl (POSS-(C3H6Cl)8) and poly(vinylidene fluoride) (PVDF) was prepared by electrospinning, which had satisfying anode stability and high dielectric constant, contributing to the dissociation of lithium salts. The effects of POSS-(C3H6Cl)8 contents on the physical, mechanical, thermal and electrochemical properties of the PP supported GPEs were analyzed. The results showed that the GPE contained 10 wt% POSS-(C3H6Cl)8 presented optimal comprehensive performance, of which the porosity and electrolyte uptake were 63.0% and 271.4%, respectively. The tensile strength and elongation at break were 31.6 MPa and 39.0%, respectively. What’s more, the thermal endurable test displayed good dimensional stability, and the flame retarding test certified respectable inflaming retarding. The ionic conductivity at ambient temperature was 2.03 × 10−3 S/cm and the electrochemical stability window was 5.7 V or so, the interfacial impedance with Li electrode was 470.0 Ω. The cells assembled with the PP supported GPEs also possessed favorable cycling and rate performance, indicating that the PP supported GPEs acquired by electrospinning POSS-(C3H6Cl)8/PVDF dispersions have a promising application prospect for lithium-ion batteries.

The role of inorganic nanoparticle on ion conduction of epoxy-based solid polymer electrolytes for lithium-ion batteries

Recently, extensive efforts have focused on the development of solid polymer electrolytes (SPEs) requiring high mechanical performance without sacrificing ion conductivity. To develop such a SPE, we incorporate robust silica mesoporous particles (SMP) into the epoxy-based SPEs, and increasing the SMP content raises the glass transition temperature of the SPEs. This enables to increase the mechanical properties of the SPEs, supported by the microstructural investigation showing a highly compact structure. Ionic conductivities of these SPEs follow Vogel temperature dependence, and increasing the silica nanoparticle content leads to a slight decrease in the conductivity, consistent with the dielectric response investigation.