Composite Solid Polymer Electrolyte Research Articles

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.

Effect of intermolecular interactions on the performance of UiO-66-laden solid composite polymer electrolytes

Solid composite polymer electrolytes have been proposed as high-performance solid electrolytes for next-generation energy storage devices. In particular, UiO-66 with monodispersed size (400 nm) and morphology and outstanding stability was introduced as a functional filler to modify the electrochemical properties of poly(ethylene oxide) (PEO) solid electrolytes with LiClO4 as the lithium salt. The desired physicochemical properties and electrochemical properties of the electrolyte was improved through microstructure regulation and the intermolecular interactions, as confirmed by X-ray diffraction, differential scanning calorimetry, optical microscopy and electrochemical characterisation. Owing to the intermolecular interactions, crystallisation of PEO was inhibited, and the ionic conductivity of the solid composite polymer electrolyte increased to 4.8 × 10−5 S cm−1 at 25 °C. Electrochemical stable window and lithium ion transference number (t+) were also observably enhanced. The assembled LiFePO4/PEO-LiClO4-UiO-66/Li solid-state lithium batteries exhibited excellent cycling and C-rate performances. The initial discharge capacity reached to 160 mAh g−1, and superior cycle stability with a capacity retention ratio of 83% after 200 cycles at 1C current and 80 °C was achieved. The discharge capacity at 5C was improved by 232%. This work provides new insights into boosting the performances of solid composite polymer electrolytes through intermolecular interactions.

Performance Enhancement of PVDF/LiCIO4 Based Nanocomposite Solid Polymer Electrolytes via Incorporation of Li0.5La0.5TiO3 Nano Filler for All-Solid-State Batteries

Experimental and computational techniques have been applied to investigate the influence of Li0.5La0.5TiO3 nanoparticles on the ionic conductivity of the poly(vinylidene fluoride) (PVDF)/LiClO4 nanocomposite solid polymer electrolyte. The theoretical evidence facilitated to suggest a plausible mechanism for Li-ion conduction across the PVDF/LiClO4/Li0.5La0.5TiO3 based solid polymer electrolytes. The solid composite polymer electrolyte with 30wt% of Li0.5La0.5TiO3 (LLTO) nanofiller exhibited an unprecedented ionic conductivity of 2.3687 × 10−3 S cm−1 at room temperature. The addition of LLTO nanoparticles to the polymer matrix enhanced its ionic conductivity by two orders of magnitude. The activation energy (Ea) and total transference number (t) were estimated to be 0.29 eV and 0.853, respectively. The interaction between the filler and polymer matrix has been inferred by the density functional theory (DFT)-IR analysis. The DFT calculations have been performed on the above system using the basis set of B3LYP-LANL2DZ. The calculated IR spectra were compared with the experimental FTIR data, which allowed us to propose accurate vibrational assignments and to clarify the complex IR vibration of the samples. All-solid-state Li2FeSiO4/CPVDF/LiClO4/LLTO graphite lithium cell has been fabricated using the highest Li-ion conducting PVDF/LiClO4/LLTO composite polymer electrolyte. The all-solid-state cell exhibits an excellent initial specific capacity of 87.13 and 73.24 mAh g−1 after 30 cycles, demonstrating higher capacity retention. The findings provide an avenue for exploring the simple all-solid-state lithium batteries, which are potential candidates for next-generation energy storage technology.

Solid polymer electrolytes based on the composite of PEO–LiFSI and organic ionic plastic crystal

In this work, composite membranes consisting of triethylmethylammonium bis(fluorosulfonyl)imide (N1222FSI), poly(ethylene oxide) (PEO) and lithium bis(fluorosulfonyl) imide (LiFSI) have been produced as solid polymer electrolytes (SPEs). The composite SPEs provide good mechanical property, high ionic conductivity at 50 °C, high electrochemical and thermal stability as well as superior interfacial compatibility with lithium metal. Moreover, Li/LiFePO4 cells containing the best-performing SPE exhibit high discharge capacity and excellent cycling performance. The results show that the novel composite SPEs might be promising electrolytes applied in all-solid-state lithium batteries.

A composite solid polymer electrolyte incorporating MnO2 nanosheets with reinforced mechanical properties and electrochemical stability for lithium metal batteries

The mechanical properties and electrochemical stability of a PEO based composite solid polymer electrolyte are enhanced by adding MnO2 nanosheets.

Hexagonal boron nitride induces anion trapping in a polyethylene oxide based solid polymer electrolyte for lithium dendrite inhibition

Lithium ion conductivity and mechanical strength of a PEO based composite solid polymer electrolyte are improved by adding h-BN.

Strong and Flexible Composite Solid Polymer Electrolyte Membranes for Li-Ion Batteries.

A composite solid polymer electrolyte (CSPE) is studied in this work to alleviate the concerns associated with poor mechanical strength of a solid polymer electrolyte (SPE) system composed of poly(ethyleneglycol)diacrylate, an electrolyte lithium bis(trifluoromethane)sulfonamide, and a plasticizer succinonitrile. CSPE is fabricated by incorporating the ingredients of SPE in the macroporous membranes of syndiotactic polystyrene to render flexibility and mechanical robustness with a 6-fold increase in tensile strength over SPE. The data from differential scanning calorimetry and wide-angle X-ray diffraction confirm the amorphous nature of the polymeric domains of SPE that produce high room-temperature ionic conductivity of ∼0.43 mS/cm. The flexible CSPE membranes are used as the electrolyte in Li-ion battery (LIB) half cells in conjunction with lithium iron phosphate as the counter electrode. The use of CSPE helps expand the electrochemical window of the cell to 5 V, indicating strong potential in the fabrication of flexible rechargeable LIBs.

AC conductivity studies of polyethylene oxide-garnet-type Li7La3Zr2O12 hybrid composite solid polymer electrolyte films

We have investigated both AC dielectric permittivity and ionic conductivity of hybrid composite solid polymer electrolyte (CSPE) films (~100 μm) comprised of sub-micron sized aluminum substituted cubic Li7La3Zr2O12 (LLZO) particles dispersed in polyethylene oxide-LiClO4 (PEO-LiClO4) matrix with [EO]:[Li] = 15:1. Homogeneous CSPE films with 50 wt% LLZO (PEO-LLZO-LiClO4) exhibit good flexibility and mechanical robustness up to 120 °C. The electrochemical potential stability window measured for these films was ~5.2 V vs. Li+/Li. The complex AC permittivity and conductivity were determined using the measured electrical impedance spectra in the range of 1 Hz to 300 kHz and found to be heavily affected by the electrode polarization in low frequency region. We have analyzed the data using an expression for complex AC conductivity that generalizes the power-law dependence taking into account the effect of electrode polarization and involving ionic and polymer segmental relaxation times in its description. This expression describes very well the observed behavior of AC dielectric permittivity and conductivity in the entire measured frequency region. The ionic and segmental relaxation times obtained from fitting the experimental data indicate a strong coupling between the ionic motion and segmental dynamics. Further, the observed temperature dependent conductivity follows the Vogel-Tammann-Fulcher (VTF) behavior implying a close correlation between ionic conductivity and segmental relaxation in these polymer electrolytes. The VTF model yields an activation energy of 0.32 eV for PEO-LiClO4 film, and 0.07 eV for PEO-LLZO-LiClO4 composite film, consistent with the observed enhancement in conductivity by two orders of magnitude at 30 °C upon the addition of LLZO particles.

Poly(ethylene oxide)-based composite solid polymer electrolyte containing Li7La3Zr2O12 and poly(ethylene glycol) dimethyl ether

We have synthesized a self-standing, flexible, highly ion conductive, and electrochemically stable composite solid polymer electrolyte (CSPE) composed of a poly(ethylene oxide) matrix, Li7La3Zr2O12 ceramic filler, and poly(ethylene glycol) dimethyl ether (PEGDME) plasticizer for all-solid-state Li-ion batteries. The CSPE containing 10 wt% PEGDME (CSPE10) shows the highest ionic conductivity of 4.7 × 10-4 S cm-1 at 60 °C. Additionally, all the CSPEs are stable up to 5.0 V vs. Li/Li+, and CSPE10 shows a high Li-ion transference number of 0.48 at 60 °C. When Li/CSPE/Li symmetric cells are cyclically polarized, the cell with CSPE10 shows the smallest overpotential because of the high ionic conductivity of CSPE10 and the low interfacial resistance between Li and CSPE10. The all-solid-state full cell with the Li/CSPE10/LiNi0.6Co0.2Mn0.2O2 configuration delivers an initial discharge capacity of 157 mA h g-1 at 0.1C at 60 °C. Even after 100 cycles at a higher C-rate of 0.5C, the full cell maintains high discharge capacity of 116 mA h g-1 corresponding to a capacity retention of ~86%. The full cell with a high LiNi0.6Co0.2Mn0.2O2 mass loading of 7.7 mg cm-2 shows an initial discharge capacity of ~160 mA h g-1 and maintains high discharge capacity of 140 mA h g-1 even after 60 cycles.

Simultaneously Boosting the Ionic Conductivity and Mechanical Strength of Polymer Gel Electrolyte Membranes by Confining Ionic Liquids into Hollow Silica Nanocavities

AbstractA central problem of solid polymer electrolytes is their inability to achieve robust mechanical strength with fast ionic conductivities required for commercialization of lithium metal batteries (LMBs). At present, state‐of‐the‐art offers superiority of one at the expense of the other. Here, this dilemma has been solved by fabricating mechanically robust solid composite polymer electrolytes (SCPEs) with superior ionic conductivity (0.5 mS cm−1 at 20 °C) by confining ionic liquids (ILs) in the hollow scaffold offered by hollow silica (HS) nanospheres with unique architecture. Mechanical robustness was verified by the performance of a Li||Li symmetric cell cycling for extended hours without short‐circuiting. In addition, SCPEs with HS have higher thermal and electrochemical stabilities than those without HS, due to strong interaction and coordination of HS nanoparticles with polymer and ionic liquids. Electrode compatibility and flexibility of the membrane could advance the LMBs technology.

A Composite Solid Polymer Electrolyte Containing Poly(propylene Carbonate) and Li1.5Al0.5Ge1.5(PO4)3 for All-Solid-State Li-Ion Batteries

During last ~30 years, lithium-ion batteries (LIBs) have been improved significantly in aspects of energy density and cyclability. In spite of several advantages of LIBs, the conventional LIBs still have suffered from the issues related to organic based electrolytes, such as leakage, volatility, flammability, and lithium dendrite formation through porous separator leading to internal short circuits. A solution is to replace the organic liquid electrolyte with suitable composite solid polymer electrolyte (CSPE). Poly(ethylene oxide) (PEO) based electrolytes are the most studied solid polymer electrolyte (SPE). However, narrow potential window, poor mechanical strength, low lithium transference number, and insufficient ionic conductivity are the major issues to be addressed in case of PEO. In contrast, poly(propylene carbonate) (PPC) has attracted tremendous attention as an alternative owing to its higher ionic conductivity, better lithium transference number, and wide potential window. The weak mechanical strength of PPC membranes is the main bottle neck to be addressed before it sees the limelight of practical application. Incorporation of a ceramic filler into PPC polymer is one of the promising way to improve the ionic conductivity as well as the mechanical strength of SPE. Among the ceramic fillers, NASICON type Li1.5Al0.5Ge1.5(PO4)3 (LAGP) possesses good stability to moisture, thermal stability, and electrochemical stability. In this work, we have studied the effects of LAGP incorporation in PPC matrix on the physical and electrochemical properties of CSPE for all-solid-state LIBs. The formation of LAGP phase was analyzed by XRD, SEM, and TEM. Furthermore, the thermal stability of prepared CSPE was evaluated using DSC and TGA. The CSPE exhibited higher ionic conductivity and mechanical strength compared with pure PPC, leading to improvement in electrochemical properties of all-solid-state lithium ion batteries composed of Li/CSPE/LiNi0.6Co0.2Mn0.2O2 (NCM622).

A highly ionic conductive poly(methyl methacrylate) composite electrolyte with garnet-typed Li6.75La3Zr1.75Nb0.25O12 nanowires

Composite solid polymer electrolytes, integrating advantages (inflammability and electrochemical stability) of inorganic parts and virtues (lower interfacial resistance, flexibility and handy preparation) of polymer matrix, present a promising prospect for safe high-energy solid-state lithium energy storage systems. Herein, one-dimensional garnet-typed Li6.75La3Zr1.75Nb0.25O12 nanowires are successfully synthesized, and the nanowires are complexed with poly(methyl methacrylate), lithium perchlorate to fabricate composite solid polymer electrolyte membranes via a facile solution-casting method. The ionic conductivity is sharply increased from 5.98 × 10−7 of filler-free solid electrolyte to 2.20 × 10−5 S cm−1 of composite solid polymer electrolyte at room temperature, because the interaction between nanowires and polymer chains provide more free volume and special ionic conductive channels. In the meantime, the composite solid polymer electrolytes exhibit the wide electrochemical window and good stability against lithium anode. The feasibility of composite solid polymer electrolyte is examined in LiCoO2/Li configuration at 0.2 C under 60 and 70 °C, the cells deliver discharge capacity of 134.6 and 143.6 mAh g−1 at first cycle and kept 92.3%, 71.8% retention after 80 and 65 cycles respectively. The results indicate that the as-prepared composite solid polymer electrolytes will be a promising candidate for solid-state lithium batteries in the future.

High-Performance Solid Composite Polymer Electrolyte for all Solid-State Lithium Battery Through Facile Microstructure Regulation.

Solid composite polymer electrolytes are the optimal candidate for all solid-state lithium batteries, because of their enhanced ionic conductivities, long-life cycle ability and compatibility to lithium anode. Herein, we reported a kind of solid composite polymer electrolyte comprised of poly(ethylene oxide), graphitic-like carbon nitride and lithium perchlorate, which was prepared by a facile solution blending method. Microstructure of the solid composite polymer electrolyte was regulated by thermal annealing and interaction among components and was characterized by XRD, DSC, FTIR-ATR, and ROM. The obtained solid composite polymer electrolyte achieved an ionic conductivity as high as 1.76 × 10−5 S cm−1 at 25°C. And the electrochemical stable window and the lithium ion transference number, t+, were also obviously enhanced. LiFePO4/Li solid-state batteries with the annealed PEO-LiClO4-g-C3N4 solid polymer electrolyte presented a high initial discharge capacity of 161.2 mAh g−1 and superior cycle stability with a capacity retention ratio of 81% after 200 cycles at 1C at 80°C. The above results indicates that the thermal annealing treatment and g-C3N4 as a novel structure modifier is crucial for obtaining the high-performance solid composite polymer electrolytes used in the all solid-state lithium battery.

Bifunctional ionic liquid and conducting ceramic co-assisted solid polymer electrolyte membrane for quasi-solid-state lithium metal batteries

Development of solid polymer electrolytes (SPEs) with high thermal and mechanical stability and fast ion conductivity is the key for high-performance lithium metal batteries (LMBs) with high safety. In this work, a flexible poly-(ethylene oxide) (PEO)-lithium bis(trifluoromethanesulfonyl)imide) (LiTFSI) SPE assisted with a bifunctional ionic liquid (IL) of tetrabutylphosphonium 2-hydroxypyridine (TBPHP) as well as a garnet-type fast-ion conducting ceramic of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) was fabricated via a solvent-free procedure and applied for the LMBs. It is found that the tetrabutylphosphonium cation (TBP+) and 2-hydroxypyridine anion (HP−) of IL effectively tuned the crystallinity of PEO and enhanced lithium ion (Li+) transference, respectively, and the TBPHP and LLZTO played a synergistic role in improving the performance of SPEs. Meanwhile, the density functional theory (DFT) study was performed to understand the interaction between TBPHP and LiTFSI. As a result, the obtained PEO8-LiTFSI-TBPHP-12.5% LLZTO composite SPE possessed a high ionic conductivity of 9.39 × 10−4 S cm−1 at 50 °C and a wide electrochemical stability window (more than 5 V) with significantly promoted uniform Li plating/stripping properties. The quasi-solid-state-LMBs assembled with LiFePO4 cathode also rendered excellent cycling stability with a high discharge capacity above 150 mA h·g−1 even after 100 cycles at 0.2 C and 50 °C. Besides, the fabricated flexible pouch cell showed excellent performance. It is expected that such a bifunctional ionic liquid and conducting ceramic co-assisted polymer composite could be a promising solid electrolyte for the next-generation of safe LMBs.

Influence of Humidity on the Performance of Composite Polymer Electrolyte-Gated Field-Effect Transistors and Circuits

In the domain of printed electronics (PE), field-effect transistors (FETs) with an oxide semiconductor channel are very promising. In particular, the use of high gate-capacitance of the composite solid polymer electrolytes (CSPEs) as a gate-insulator ensures extremely low voltage requirements. Besides high gate capacitance, such CSPEs are proven to be easily printable, stable in air over wide temperature ranges, and possess high ion conductivity. These CSPEs can be sensitive to moisture, especially for high surface-to-volume ratio printed thin films. In this paper, we provide a comprehensive experimental study on the effect of humidity on CSPE-gated single transistors. At the circuit level, the performance of ring oscillators (ROs) has been compared for various humidity conditions. The experimental results of the electrolyte-gated FETs (EGFETs) demonstrate rather comparable currents between 30%–90% humidity levels. However, the shifted transistor parameters lead to a significant performance change of the RO frequency behavior. The study in this paper shows the need of an impermeable encapsulation for the CSPE-gated FETs to ensure identical performance at all humidity conditions.

Tailoring Mesoporous Silica Nanoparticles and Thin Films: Synthesis, Characterization and Electrochemical Applications

Mesoporous silica materials have played great roles in widespread application areas like adsorption, catalysis, and separation due to their high surface area, large pore volume and tunable pore size and structure. One of the approaches for extending the application of mesoporous silica materials is tailoring their wall with various functional groups. However, the conventional post-grafting method results in lightly dense, heterogeneously distributed and less accessible functional groups. In our work, a new method that leads to dense and uniform functionalization of the wall without clogging of the pores has been employed. The hybrid silica-based materials are fabricated either through diblock copolymer templated sol-gel method or through electro-assisted self-assembly method. In the former case, since the template is self-assembled functional amphiphilic diblock copolymer, the selective removing of the hydrophobic block results in porous and PEO functionalized silica materials. Textural and structural properties of the hybrid porous materials will be presented. Furthermore, their application in the area of Li-ion battery as solid composite polymer electrolytes will be discussed. In the later case, surfactant templated mesoporous silica films have been fabricated on conductive substrates via electro-assisted self-assembly method. Hexagonally well-ordered and vertically oriented mesochannels with a diameter of 3nm are obtained in a large domain across the resulted films. The permeability, morphology and nanostructure of the films will be presented. Figure 1

Development of all-solid-state battery based on lithium ion conductive polymer nanofiber framework

A thin, flexible, and safe composite polymer electrolyte membrane composed of lithium ion conductive nanofiber framework and polymer electrolyte matrix is demonstrated as an innovative solid-state electrolyte for potential use in high-performance rechargeable all-solid-state lithium ion battery. Due to this unique structural integrity, the composite solid polymer electrolyte indicates excellent mechanical stability, remarkable improvements in the ion conductivity (approximately 10−4 S cm−1 at room temperature) and the lithium ion transference number (approximately 0.5), and the significant battery performance in terms of good charge-discharge cycling behavior and moderate rate capability. Finally, a high-voltage multi-stacked battery with the solid polymer composite electrolytes is developed and can readily produce a doubled cell potential of 6.8 V, promising future batteries operated at high-voltage with high energy densities.

Characterization of polymer/liquid crystal composite based electrolyte membranes for sodium ion battery applications

A novel PEO/E8 liquid crystal based composite solid polymer electrolyte membranes complexed with NaIO4 salt were prepared by the solution casting technique. The composite-salt complexations were examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, micro-Raman and X-ray photoelectron spectroscopy (XPS) studies. Differential scanning calorimetry (DSC) studies confirmed the decrease of percentage of crystalline portion in the matrix of electrolyte membranes upon that addition of NaIO4. The EIS studies evidenced for the increase of ionic conductivity of the electrolytes upon increase of NaIO4 concentration and in the present study, PEO/E8 electrolyte complexed with 10 wt% of NaIO4 demonstrated higher room temperature ionic conductivity of 1.05 × 10−7 S/cm.

Composite Solid Polymer Electrolyte with Garnet Nanosheets in Poly(ethylene oxide)

Solid electrolytes potentially provide safety, Li dendrites blocking, and electrochemical stability in Li-metal batteries. Large efforts have been devoted to disperse ceramic nanoparticles in a poly(ethylene oxide) (PEO) matrix to improve the ions transport. However, it is challengeable to create efficient framework for ions transport with nanoparticles. Here we report for the first time garnet nanosheets to provide interconnected Li-ions transport pathway in a PEO matrix. The garnet nanosheet fillers would not only facilitate ions transport but also enhance ionic conductivity in comparison with their nanoparticle counterparts. A composite solid polymer electrolyte containing 15 wt % garnet nanosheets exhibits a practically useful conductivity of 3.6 × 10–4 S cm–1 at room temperature. Besides, the composite electrolyte can robustly isolate Li dendrites in a symmetric lithium metal-composite electrolyte battery during reversible Li dissolution/deposition at a relatively low temperature of 40 °C. The symmet...

Polyethylene oxide/garnet-type Li6.4La3Zr1.4Nb0.6O12 composite electrolytes with improved electrochemical performance for solid state lithium rechargeable batteries

Next generation lithium batteries require new electrolytes with good safety, excellent ionic conductivity, high electrochemical stability and good cycling performance. Herein, we first report a solid composite polymer electrolyte comprises of Li6.4La3Zr1.4Nb0.6O12 fillers and polyethylene oxide matrix. The ionic conductivity of the solid composite electrolyte is significantly improved to 1.4 × 10−3 S cm−1 (60 °C) and the electrochemical window is enhanced to 5.2 V, respectively, by incorporation of Li6.4La3Zr1.4Nb0.6O12 powder at a weight ratio of 0.5:1 with respect to polyethylene oxide. The solid batteries employing the composite electrolytes are able to work at room temperature and have a capacity retention of 99% after cycle. The performance improvement is primarily due to the combined functions of each component in the composite: (i) the incorporation of fillers effectively decreases the crystallinity of PEO, providing more amorphous region for ion conduction; (ii) Li6.4La3Zr1.4Nb0.6O12 serves as a fast ion conductor in the composite and enhance the electrochemical stability; (iii) the polymer matrix forms intimate surface contact with fillers and electrodes, reducing the bulk and interfacial resistance. The composite polymer electrolyte in this work would be a competitive alternative for the next generation solid state lithium rechargeable batteries.