Ion Conducting Polymer Electrolyte Research Articles

Identifying ultrathin dielectric nanosheets induced interface polarization for high-performance solid-state lithium metal batteries

Solid-state lithium metal batteries (SSLMBs) with polymer electrolytes are promising due to enhanced safety and high energy density, but the low ionic conductivity of polymer electrolytes and the unstable interface of lithium metal anode hinder the development of SSLMBs. Herein, we propose a unique strategy to address these challenges by coupling ultrathin high-dielectricity Ca2Nb3O10 (CNO) nanosheets with PEO-based electrolyte. The interfacial polarization originating from the distortion of NbO6 octahedra along the vertical direction of CNO nanosheets is maximized and so the interaction between CNO and LiTFSI, which greatly supports the dissociation of LiTFSI and improves the ionic conductivity (2.0 × 10−4 S cm−1) of the composite polymer electrolyte, compared to that without CNO. The optimized interfacial polarization effect is thoroughly demonstrated by theoretical calculation and experimental results. Moreover, due to a homogeneous, robust and LiF-rich solid electrolyte interphase film with promoted Li+ ion transport being formed at the lithium metal interface, the superior cycling stability (90% capacity retention after 440 cycles at 0.5 C) and rate capability for LFP||Li full batteries are achieved. This design of composite polymer electrolyte with ultrathin dielectric nanosheet fillers demonstrates a new approach to the development of high-performance polymer electrolytes for SSLMBs.

Application of triblock copolymers in lithium-ion batteries based on solid electrolyte

In the future, all-solid Li-ion batteries are expected to gain widespread acceptance in larger markets due to their high safety and excellent electrochemical performance. However, it is important to acknowledge their drawbacks, including the inadequate compatibility between the electrode and electrolyte interface and the low ionic conductivity at room temperature. This paper reviews the specific methods and the latest research progress of triblock copolymers to solve the above problems. Block copolymerization is an effective way to enhance the efficiency and performance of electrolyte. Its advantage is that two or more monomers with different properties can be polymerized into the same structure, which is conducive to the ionic conductivity of polymer electrolyte. In the latest research results, straight-chain block copolymers have been synthesized, which have better physical and chemical properties compared to traditional comb block copolymers. However, the electrochemical properties of the straight-chain block copolymer electrolyte and the stability of the interface between the electrode and the solid electrolyte are rarely reported. Therefore, it is particularly important to systematically study the electrochemical properties and interface properties of block copolymer electrolytes. In the future, more attention should be drawn to not only improving the properties of SPEs but also building a stable interface with low interface resistance.

Chitosan as a suitable host for sustainable plasticized nanocomposite sodium ion conducting polymer electrolyte in EDLC applications: Structural, ion transport and electrochemical studies

The challenge in front of EDLC device is their low energy density compared to their battery counter parts. In the current study, a green plasticized nanocomposite sodium ion conducting polymer blend electrolytes (PNSPBE) was developed by incorporating plasticized Chitosan (CS) blended with polyvinyl alcohol (PVA), doped with NaBr salt with various concentration of CaTiO3 nanoparticles. The most optimized PNSPBE film was subsequently utilized in an EDLC device to evaluate its effectiveness both as an electrolyte and a separator. Structural and morphological changes were assessed using XRD and SEM techniques. The PNSPBE film demonstrated a peak ionic conductivity of 9.76×10−5 S/cm, as determined through EIS analysis. The dielectric and AC studies provided further confirmation of structural modifications within the sample. Both TNM and LSV analyses affirmed the suitability of the prepared electrolyte for energy device applications, evidenced by its adequate ion transference number and an electrochemical potential window of 2.86 V. Electrochemical properties were assessed via CV and GCD techniques, confirming non-Faradaic ion storage, indicated by the rectangular CV pattern at low scan rates. The parameters associated with the designed EDLC device including specific capacitance, ESR, power density (1950 W/kg) and energy density (12.3 Wh/kg) were determined over 1000 cycles.

Proton ion-conducting polymer electrolytes added with SiO2 nanoparticles: conductivity, dielectric, relaxation, and physical studies

Proton ion-conducting polymer electrolytes added with SiO2 nanoparticles: conductivity, dielectric, relaxation, and physical studies

Amorphous Magnesium-Doped Chitosan films as solid polymer electrolytes for energy storage device applications

Magnesium ion-conducting biodegradable solid polymer electrolyte (SPE) films of magnesium perchlorate [Mg(ClO4)2] doped Chitosan [CS] were prepared using the solution casting technique at room temperature. XRD study shows that amorphous nature of the polymer matrix increases upon doping. FTIR deconvolution confirm the complexation generated between the salt and the polymer. The current–voltage measurement exhibited electrochemical stability window for all samples above 2.14 V. The ionic transference number for the highest conducting sample was 0.99. The impedance analysis was done for each SPE film, and the sample with the highest concentration (40 wt%) exhibited the highest conductivity, 5.7 × 10-4 Scm−1. The prepared primary magnesium battery using the highest conducting SPE showed open circuit potential of 2.112 V. Due to its exceptional qualities, this prepared electrolyte may be a strong contender for energy storage systems.

Improving the ionic conductivity of polymer electrolytes induced by ceramic nanowire fillers with abundant lithium vacancies.

The addition of ceramic fillers is regarded as an effective strategy for enhancing the ionic conductivity of polymer electrolytes. However, particulate fillers typically fail to provide continuous conductive pathways and effective reinforcement. Herein, we report a ceramic nanowire filler with long-range interfacial conductivity and abundant lithium vacancies for a poly(ethylene oxide) (PEO)-based all-solid-state polymer electrolyte. LLZO nanowires (LLZO NWs) with a high aspect ratio are synthesized by combining sol-gel electrospinning and the multi-step process involving pre-oxidation, pre-sintering, and secondary sintering, resulting in a high tensile strength of the composite electrolyte (6.87 MPa). Notably, tantalum-aluminum co-substituted LLZO NWs (TALLZO NWs) release abundant lithium vacancies, further enhancing the Lewis acid-base properties, leading to a rapid ion migration speed (Li+ transfer number = 0.79) and significantly high ionic conductivity (3.80 × 10-4 S cm-1). Due to the synergistic effect of nanostructure modification and heteroatom co-doping, the assembled all-solid-state lithium-sulfur battery exhibits a high initial discharge capacity (776 mA h g-1 at 25 °C), remarkable rate capability, and excellent cycling performance (81% capacity retention after 200 cycles at 0.1C).

Investigation on the properties of PVDF matrix composite porous gel polymer electrolyte doped with lithium silicon gel

Gel polymer electrolytes are safer because they do not contain liquid phase components. On this basis, the introduction of inorganic fillers effectively overcame the problem of low ionic conductivity of polymer electrolyte at room temperature, and the constructed composite polymer electrolyte (CPEs) combined the advantages of inorganic fillers and polymer segments. In this paper, lithium silicon gel SiO2(Li+) was prepared by in-situ polymerization and sol-gel method, and doped in PVDF composite porous gel polymer electrolyte film prepared by immersion precipitation method. The electrochemical properties and surface topography of lithium iron phosphate were investigated by mounting a bonded lithium iron phosphate quasisolid lithium-ion battery. The experimental results show that the solid electrolyte film modified by SiO2(Li+) has good electrochemical and a certain reference value.

Development and Characterization of a New Solid Polymer Electrolyte for Supercapacitor Device

In this study, solid polymer electrolytes (SPEs) are based on methylcellulose (MC) used as a polymer host and sodium iodide (NaI) as a dopant. The SPE films are developed using different contents of ethyl carbonate (EC) as a plasticizer to enhance their properties via a solution casting method. The surface morphology of SPE films is shown using polarized optical microscopy (POM), which indicates the existence of amorphous patches due to the plasticizing effect of EC. The creation of a complex between MC, NaI, and EC was confirmed by Fourier transform infrared (FTIR) spectra. A tiny amount of EC applied to the MC-NaI polymer salt matrix increases the number of charge carriers and improves ionic conductivity. The ionic conductivity of the generated polymer electrolytes is examined using electrochemical impedance spectroscopy (EIS). The high-ion conducting PE of 5.06 × 10−3 S·cm−1 was found with the mixture MC + 50 wt% NaI + 10 wt% EC (room temperature). The linear speed voltammetry (LSV) test shows that the optimized polymer electrolyte can withstand decomposition up to 2.5 V. The optimized sample transmission numbers were calculated using a TNM (transference number measurement) approach, and the results show that 99% of the ions contribute to the conductivity, compared to only 1% of the electrons. A solid-state electrical double-layer capacitor (EDLC) was fabricated using the highest ion-conductive polymer electrolyte and graphene oxide (GO)-based electrodes. The galvanostatic charge-discharge (GCD) technique was performed, and the GCD graph shows the behavior of an ideal capacitor with a less Faradic process and a low ESR value. The GO-based cell’s columbic efficiency is 100%, and the system delivers the charge for a long duration. The EDLC cell demonstrates outstanding cyclability. The specific capacitance of the EDLC cell incorporated with MC + 50 wt. % NaI + 10 wt. % EC was found to be 154.66 F/g.

The impact of lithiated active binder on Li-ion battery charge–discharge and rate capability, Part II: Mesoscale modeling of LCO based Half-cell

Even though thick electrodes are essential to increasing the energy density of LIBs, high current rates cause them to lose power density due to high polarization and ion depletion in the pore spaces. Mixed active binders with lithiated bound charges can improve the battery capacity and voltage at high C-rates, even compared to similar high concentrated electrolyte. The lithiated binders also provide a more uniform spatial distribution of intercalation reaction current, electric potential, and open circuit potential. The LIB half cell is modeled at mesoscale by taking into account the diffusion–reaction physics of the bound charge mixed electrolyte in active carbon-binder-domain (CBD), that accounts the dissociation of anionic ligands. Electrolyte in separator and active CBD are coupled by Donnan theory at the interface, and the reaction interfaces are modeled by the standard Butler–Volmer equation. By means of a thermodynamically consistent model and its implementation in a FEM code, we investigate the impact of particle distribution, electrode thickness, and separator thickness for both standard binder and active binder mixed cathodes in terms of ion depletion, current density, and electric potential. This mathematical model can also be extended to the modeling of ion conducting polymer electrolytes, gel polymers, and other conductive materials for battery applications.

Durability and Performance of Poly(norbornene) Membranes and Ionomers in Alkaline Electrolyzers

Ion conducting polymer electrolytes provide an enabling technology for low-temperature alkaline electrolyzers. The critical parameters of solid polymer electrolytes include ionic conductivity, ion selectivity, chemical resistance and dimensional stability in the presence of excess water. High pH operation using anion conductive polymer electrolytes has several potential advantages over acid-based polymer devices including low-cost catalysts, hydrocarbon (non-perfluorinated) polymer, and low cost cell components.In this study, a family of hydroxide conducting, poly(norbornene) solid polymer electrolytes were synthesized and used in high-performance, durable membrane electrode assemblies for fuel cells and electrolyzers. In addition to membranes, covalently bonded, self-adherent, hydroxide conducting ionomers were used to form high-performance, durable membrane electrode assembly for water electrolysis. The self-adhesive ionomers and membranes are based on hydroxide conducting poly(norbornene) polymers. The effect of porous transport layer material and porosity was examined. High performance electrolysis with very low degradation rates was achieved using stainless steel and nickel porous transport layers and flow-channels

Ion Transport in Polymer/Inorganic Composite Electrolytes – a Comparison between Broadband Dielectric Spectroscopy and Impedance Spectroscopy

Significant efforts have been made to develop composite electrolytes combining polymer matrix with Li-ion conducting inorganic solids for feasible construction of solid-state batteries. However, the Li-ion transfer kinetics at the interface between polymer/inorganic electrolyte is unfavorable for Li-ion conduction in the composite electrolyte because of the interfacial resistance and the activation energy barrier for interfacial Li-ion transfer. The activation energy barrier for the Li-ion transfer reaction at the interface is correlated with the interaction between Li-ion and polymer matrix in the polymer electrolyte, interaction between Li-ion and anions in inorganic electrolytes and the interaction between polymer and inorganic electrolytes, therefore, the electrolyte composition significantly affects the interfacial charge transfer kinetics in composites.In this work, Li-ion transport properties in the composite electrolytes are investigated by using broadband dielectric spectroscopy (BDS) and impedance spectroscopy (IS). We particularly focus on Li-ion charge transfer at the polymer/inorganic interface from the dual ion conducting polymer to the single ion conducting polymer electrolytes with different Li-ion conducting salts such as LiN(SO2CF3)2 (LiTFSI) and (LiMTFSI) in vinyl ethylene carbonate (VEC) or polymerized vinyl ethylene carbonate (PVEC). The interfacial resistances of inorganic electrolytes Li0.34La0.56TiO3 (LLTO) in polymer electrolytes are elucidated. To further evaluate the polymer/inorganic electrolyte interfaces, various types of cell are assembled in a glove box filled with argon gas and characterized by a series of techniques such as BDS and IS. The Li-ion transfer kinetics at the interface significantly affects the Li-ion flux through the composite electrolytes and will be presented. In addition, we will present a systematic comparison between BDS and IS results in order to build connections between the two communities. 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.

Interfacial polymer architecture can control nanoparticle dispersion and rheological behavior of nanocomposites

Polymer nanocomposites (PNCs) have become essential components in many advanced materials applications, from solid state battery electrolytes to high-performance structural components. In PNCs, the large fraction of interfacial polymers determines their outstanding rheological performance; yet, strategies to control the structure and dynamics of the interfacial polymer has been very limited. Here, using poly(ethylene oxide)-silica model nanocomposite system, we propose a facile approach based on varying macromolecular architecture of interfacial polymers. We show that by changing the topology of the bound polymer from linear to star and hyperbranched, polymer-NP interaction as well as chain interpenetration in the interphases can be effectively altered without changing type or molecular weight of the polymer, or NP surface chemistry in attractive PNCs. Our results show that both dispersion and rheological behavior of PNCs depend highly on functionality and arm length of the polymers used at the interfaces. These results can be used to design ion-conductive molten polymer electrolytes with significantly improved mechanical properties suitable for solid-state battery applications.

LiNO3-poly(vinyl alcohol) polymer electrolytes and its applications in electrochemical capacitors with extended operating temperatures

An ion-conducting neutral pH polymer electrolyte based on LiNO3 and poly(vinyl alcohol) (PVA) was developed for solid electrochemical double layer capacitors (EDLCs). Structural characterizations of LiNO3-PVA electrolytes revealed amorphous structure with well-hydrated ions. The polymer electrolytes are functional over a wide range of temperatures even at −40 °C. Although increasing the concentration of ions can improve the ionic conductivity at and above ambient, it imposes adverse effects at lower temperatures likely due to the freezing of water surrounding the hygroscopic nitrate ions. The optimal electrolyte with relatively high ionic conductivity (ca. 40 mS cm−1 at ambient) and good temperature performance was applied for solid EDLC devices with multi-walled carbon nanotube electrodes. The solid EDLC showed comparable performance to its liquid baseline with excellent rate capability and wide voltage window of 1.6 V. It outperformed the liquid counterpart with lower leakage current and retained capacitive behaviour at −40 °C.

Fourier transform infrared studies of gel polymer electrolyte based on poly(acrylamide-co-acrylic acid) – Ethylene carbonate incorporated with water-soluble sodium sulfide

The incorporation of plasticizer to a solid polymer electrolyte have shown high conductivity, good thermal and chemical stabilities, long life and reduced costs. The improved conductivity is mainly contributed by higher ion diffusion coefficient and better ion mobility. However, little is known about the possible molecular interactions between plasticizer, polymer host and salt, particularly in explaining the mechanism pertaining to ion transport in the gel polymer electrolytes (GPEs). A flexible GPE based on poly(acrylamide-co-acrylic acid) (PAAm-PAA), ethylene carbonate (EC) and water-soluble sodium sulfide (Na2S) was developed. PAAm-PAA and Na2S are incorporated as the polymer backbone and the source of charge carriers, respectively, and EC acts as the plasticizer of the system. When 0.4 wt% of EC was added to PAAm-PAA-Na2S GPE, the ionic conductivity of polymer electrolytes increased from 5.11 × 10−2 S cm−1 to 6.92 × 10−2 S cm−1. The possible molecular interactions between PAAm-PAA, Na2S and EC and their correlation with ionic conductivity were investigated by Fourier transform infrared (FTIR) spectroscopy. Infrared spectroscopy showed that the intensities of the amide (CO, C–N), carboxylate (COO−) and sulfate (SO42−) bands increased with the addition of EC, and the position of the asymmetric bending (v4) of SO42− band down shifted from 677 cm−1 to 667 cm−1. These findings, the changes in shape, intensity, and position of the PAAm-PAA-Na2S-EC GPE, suggest a dipole-dipole interaction between (i) PAAm-PAA and distilled water, (ii) PAAm-PAA and EC and (iii) EC and distilled water. On the other hand, ion-dipoles interactions may occur between (i) Na+ cation and distilled water, (ii) Na+ cation and PAAm-PAA and (iii) Na+ cation and EC. It can be concluded that EC interacts with both PAAm-PAA and Na2S, and EC-Na+ complexes also appear in PAAm-PAA-Na2S-EC GPE. The increase in the conductivity of GPE is attributed to the high ion diffusion coefficient and mobility, which is attributed to the presence of EC.

Decoding Polymer Architecture Effect on Ion Clustering, Chain Dynamics, and Ionic Conductivity in Polymer Electrolytes.

Poly(ethylene oxide) (PEO)-based polymer electrolytes are a promising class of materials for use in lithium-ion batteries due to their high ionic conductivity and flexibility. In this study, the effects of polymer architecture including linear, star, and hyperbranched and salt (lithiumbis(trifluoromethanesulfonyl)imide (LiTFSI)) concentration on the glass transition (T g), microstructure, phase diagram, free volume, and bulk viscosity, all of which play a significant role in determining the ionic conductivity of the electrolyte, have been systematically studied for PEO-based polymer electrolytes. The branching of PEO widens the liquid phase toward lower salt concentrations, suggesting decreased crystallization and improved ion coordination. At high salt loadings, ion clustering is common for all electrolytes, yet the cluster size and distribution appear to be strongly architecture-dependent. Also, the ionic conductivity is maximized at a salt concentration of [Li/EO ≈ 0.085] for all architectures, and the highly branched polymers displayed as much as three times higher ionic conductivity (with respect to the linear analogue) for the same total molar mass. The architecture-dependent ionic conductivity is attributed to the enhanced free volume measured by positron annihilation lifetime spectroscopy. Interestingly, despite the strong architecture dependence of ionic conductivity, the salt addition in the highly branched architectures results in accelerated yet similar monomeric friction coefficients for these polymers, offering significant potential toward decoupling of conductivity from segmental dynamics of polymer electrolytes, leading to outstanding battery performance.

An insight into the suitability of magnesium ion-conducting biodegradable methyl cellulose solid polymer electrolyte film in energy storage devices

Biodegradable solid polymer electrolyte films based on methyl cellulose and magnesium acetate tetrahydrate [Mg(CH3COO)2.4H2O] are prepared using the conventional solution casting technique. Structural analysis of the electrolyte films confirmed the complexation of salt with the polymer matrix. The incorporation of salt into the polymer matrix resulted in the enhancement of the amorphousness of the matrix. The thermal properties of the electrolyte film are analyzed with the help of DSC and TGA thermograms. Impedance analysis of the films indicates the enhancement of the electrical conductivity of the system. The maximum room temperature ionic conductivity (2.61 × 10−5 S/cm) was observed for the 25wt% salt-doped sample. The highest conducting electrolyte system has an Electrochemical Stability Window (ESW) of 3.47 V. In the current work, a primary battery was assembled using the highest conducting polymer electrolyte system, and its open-circuit potential and discharge characteristics were also investigated.Graphical abstract

Design, production, and characterization of three-dimensionally-structured oxide-polymer composite cathodes for all-solid-state batteries

Inorganic all-solid-state batteries with oxide electrolytes show improved safety compared to conventional lithium-ion batteries due to the application of a non-flammable solid electrolyte. However, the currently applied production methods are unsuitable for creating oxide composite cathodes with a good interfacial contact between the solid electrolyte and the cathode active material, which limits the accessible discharge capacity. Thus, solid electrolyte matrix-supported all-solid-state batteries, for which a porous scaffold is filled with cathode active material, have recently seen increasing research interest. This publication introduces a scalable production route for a matrix-supported cell concept with a three-dimensionally-structured oxide-based composite cathode. Directed microstructures with different geometries were introduced into NASICON-type Li1.5Al0.5Ti1.5(PO4)3 oxide solid electrolyte layers via laser ablation. The obtained porous scaffold was infiltrated with various cathode slurries containing cathode active material and an ion-conducting polymer electrolyte to fabricate hybrid composite cathodes with an improved electrode-electrolyte interface. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed a high pore filling degree. A promising specific discharge capacity of 120.1 mAh·g−1 was achieved during electrochemical testing of a prototype all-solid-state battery with a LiNi0.6Mn0.2Co0.2O2 composite cathode and a lithium metal anode. Overall, this work serves as a proof-of-concept for the novel, matrix-supported cell design and provides insights into the production processes involved.

Humidity Effect on Ionic Conductivity of Composite Polymer Electrolytes

AbstractThe solid polymer electrolytes (SPE) based electrochemical devices are an area of attention for more than two decades. The ability of thin‐film preparation and leakage proof over the liquid counterpart are the key factors of SPE. In the present work, two different compositions, 80–20 and 85–15, of PVA:KI has been used as a host polymer complex. Where further 10 wt% of p‐Si dispersed with PVA:KI complexes. Polymer films have been prepared with standard solution cast techniques, which are further characterized for their electrical conductivity by Electrical Impedance Spectroscopy (EIS). Also, the humidity effect on the ionic conductivity of these thin films is calculated. It is observed that the ionic conductivity of these polymer electrolytes films increases with 58%, 74%, and 89% humidity. To understand the change in this ionic conductivity, the concentration and mobility of ions are also calculated, and it is found that the change in conductivity are predominately influenced due to the mobility of charge carriers.

Challenges of polymer electrolyte with wide electrochemical window for high energy solid‐state lithium batteries

AbstractWith the rapid development of energy storage technology, solid‐state lithium batteries with high energy density, power density, and safety are considered as the ideal choice for the next generation of energy storage devices. Solid electrolytes have attracted considerable attention as key components of solid‐state batteries. Compared with inorganic solid electrolytes, solid polymer electrolytes have better flexibility, machinability, and more importantly, better contact with the electrode, and low interfacial impedance. However, its low ionic conductivity, narrow electrochemical stability window (ESW), and poor mechanical properties at room temperature limit its development and practical applications. In recent years, many studies have focused on improving the ionic conductivity of polymer electrolytes; however, few systematic studies and reviews have been conducted on their ESWs. A polymer electrolyte with wide electrochemical window will aid battery operation at a high voltage, which can effectively improve their energy density. Moreover, their stability toward lithium metal anode is also important. Therefore, this review summarizes the recent progress of solid polymer electrolytes on the ESW, discusses the factors affecting ESW of polymer electrolytes, and analyzes a strategy to broaden the window from the perspective of molecular interaction, polymer structural design, and interfacial tuning. The development trends of polymer electrolytes with wide electrochemical windows are also presented.image

Hollow multishelled structural ZnO fillers enhance the ionic conductivity of polymer electrolyte for lithium batteries

Hollow multishelled structural ZnO fillers enhance the ionic conductivity of polymer electrolyte for lithium batteries