SPE Films Research Articles

Unveiling the Synergy of Polymer–Salt Compositions for Properties Enhancement of Solid Polymer Electrolytes Based on PEO/PVP Blend Polymer Matrix and LiTFSI Dopant Salt

Solid polymer electrolytes (SPEs) are ion-dipole complexes credited to their use in the design and development of widespread solid-state ion conducting innovative devices. Accordingly, herein, two sets of highly flexible, stretchable, and sticky type SPE films based on poly(ethylene oxide) (PEO)/ poly(vinyl pyrrolidone) (PVP) blend as host matrix of different compositional ratios (i.e., 25/75, 50/50, and 75/25 wt/wt%) with 30 and 50 wt% lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as ionic dopant salt, and also one sample of polymer-in-salt (PiS) comprised the 50/50 wt/wt% polymer blend matrix and 60 wt% salt, are prepared and characterized in detail. These SPEs are predominantly amorphous having substantial absorbance for ultraviolet-visible radiations and tunable wide range energy band gaps. The 20 Hz—1 GHz broadband dielectric permittivity, loss angle tangent, and electrical conductivity spectra explained a variety of polarization and structural relaxation processes and the mechanism of ion transport ruled by the compositional synergy of polymer and salt in these SPEs. The highest ionic conductivity with appreciable electrochemical performance of the SPE is found for the PEO-rich blend matrix with 50 wt% of LiTFSI dopant. We conclude the suitability of these enhanced promising propertiesSPEs for the development of futuristic ion-conducting energy storage as well as revolutionary iontronic devices.

Highly scalable and solvent-free fabrication of a solid polymer electrolyte separator via film casting technology

In order to develop competitive all-solid-state batteries, cost efficient and highly scalable manufacturing methods need to be identified and evaluated. In this work, the scalable production of a polymer solid electrolyte (SPE) separator was investigated to gain deep knowledge on how the process parameters influences product quality and reproducibility. In detail, a sustainable, solvent-free manufacturing route for the fabrication of SPE films based on a PEO based block copolymer through a novel, highly scalable film casting process was developed. The scalability, energy consumption and the SPE separator properties film thickness, density, ionic conductivity, polymer degradation and lithium salt distribution were evaluated in comparison to a reference calendering process. Compared to the considered reference process, the developed film casting process showed improved precision at higher throughputs regarding a constant film thickness below 30 μm and SPE density. The novel film casting process showed a significantly lowered energy consumption, which is of major importance with respect to production costs and sustainability. At the same time, the electrochemical performance was preserved with an ionic conductivity of approx. 0.2 mS cm−1 at 80 °C as well as a rate capability of approx. 60 mAh gLFP−1 at 1C discharge rate.

Selection of best composition of Na+ ion conducting PEO-PEI blend solid polymer electrolyte based on structural, electrical, and dielectric spectroscopic analysis

In this paper, we report the investigation on structural, electrical, dielectric properties, and ion dynamics of novel blend polymer electrolyte matrix (PEO-PEI) complexed with sodium hexafluorophosphate salt. All the solid polymer electrolyte films have been synthesized via solution cast method. The SPE films were characterized by the X-ray diffraction, field emission scanning electron microscope, impedance-dielectric spectroscopy, and thermogravimetric analysis. The morphology of the SPE alters with salt addition and confirms the blend polymer complex formation. The FTIR analysis evidenced the complex formation, and increase in the fraction of free ions is achieved. The ionic conductivity exhibits a maximum at the stoichiometric ratio O/Na = 10 and follows the Arrhenius behavior. The fraction of free ions is maximum for the SPE film with the highest ionic conductivity. The optimum electrolyte possesses a voltage stability window of about 4 V, excellent thermal stability up to 380 °C, and high ionic transference number (~ 1). The complex permittivity and conductivity have been simulated in whole frequency window to extract relaxation time and dielectric strength. The dielectric constant and relaxation time exhibited sequentially a maximum and minimum for the SPE film with the highest ionic conductivity. The loss tangent peak shifts toward high frequency with addition of salt, and it infers the faster ion dynamics in the polymer matrix. Then the ion transport parameters number density of charge carriers (n), ion mobility (μ), and diffusion coefficient (D) have been obtained by three methods (FTIR, impedance spectroscopy, and loss tangent method) and are in absolute correlation with the impedance results. An ion transport mechanism has been proposed based on experimental findings.

Lithium ion conduction in PVA-based polymer electrolyte system modified with combination of nanofillers

Nanocomposite solid polymer electrolyte films based on poly-vinyl alcohol were synthesized using solution cast technique. The effects of electric field on the ionic conductivity were investigated. The addition of nanofillers such as BaTiO3, SrTiO3, Al2O3, and MMT to PVA has been found to increase the DC electrical conductivity of the SPE films. The structural change induced in the sample due to the addition of nanofillers was investigated using DSC and XRD techniques. The XRD and DSC results show that amorphosity of the sample increased as the combination of nanofillers was added to the polymer matrix. The temperature dependence of the DC electrical conductivity was carried out between 298–323 K and varying the electric fields from 0 to 100 Vcm−1. The obtained results reveal that ionic conductivity of the electrolyte film increased non-linearly with electric field. The electric field and temperature-dependent conductivity of the polymer electrolyte films were explained using the mathematical model proposed earlier. The field factor and activation energy for the PVA-based system were evaluated.

Optimized nano-perovskite lanthanum cuprate decorated PVA based solid polymer electrolyte

ABSTRACTSolid polymeric electrolytes (SPEs) based on PVA/2wt% La2CuO4 with 5, 10 and 15 wt% of LiClO4 have been fabricated via solution intercalation technique. TEM result indicates that the size of nanoparticles (NPs) lies in the range 91–134 nm. The morphological behavior of PVA-SPEs probed by SEM; where the roughness of SPE films increased with increase in LiClO4 contents. The structural behaviors of SPEs have been elucidated by XRD, while ion-dipole interactions between components were evaluated by FTIR. The optical properties of SPEs investigated by UV-visible spectroscopy, where the outcomes showed increased refractive index from 1.74 to 2.41, whereas the band gap energy (Eg) is reduced from 5.26 to 3.32e V for PVA and PVA/2wt% La2CuO4/15wt%LiClO4, respectively. Electrical properties of the SPEs evaluated using LCR-meter at room temperature in frequency range 50 Hz–5 MHz. The ac-conductivity (σac) strongly depends on frequency and LiClO4 contents in SPEs and the maximum σac achieved is 2.82X10–5 Scm–1 for 15wt% LiClO4 doped PVA/La2CuO4 film. The current-voltage (I-V) data indicated non-ohmic behaviors at higher potential voltage region (> 6 V) and dc-conductivity (σdc) increased with increase in dosage of LiClO4 in SPEs through hopping ions mechanism. Thermal properties of the SPEs have been evaluated using DSC and TGA. The reduction in Tg of flexible SPEs with increase in LiClO4 content was observed due to amorphous portion dominates in SPEs.

Effectively improved ionic conductivity of montmorillonite clay nanoplatelets incorporated nanocomposite solid polymer electrolytes for lithium ion-conducting devices

Synergistic effects of lithium salt concentration and inorganic nanofiller incorporation on the ionic conductivity of polymer blend matrix based nanocomposite solid polymer electrolytes (NSPEs) have been examined. The montmorillonite (MMT) clay nanoplatelets incorporated NSPE films based on poly(ethylene oxide) and poly(methyl methacrylate) blend matrix with lithium tetrafluoroborate (LiBF4) ionic salt have been prepared by the solution-cast method followed by melt-press technique. The 1, 3, and 5 wt% MMT amounts along with 13.3 wt% LiBF4 amount as compared to the weight of polymer blend have been used for the preparation of NSPE films. X-ray diffractometer (XRD) and the Fourier transform infrared (FTIR) spectrometer have been employed for structural characterization of these NSPE films. The complex permittivity and ac electrical conductivity spectra are investigated by using the dielectric relaxation spectroscopy, whereas the electrochemical performance of these materials has been characterized by the electrochemical analyzer. The XRD patterns reveal that the NSPEs are predominantly amorphous and have the intercalated and exfoliated MMT platelets, whereas the relative changes in their FTIR spectra confirm the ion–dipolar–nanofiller interactions between the functional groups of the blended polymers, lithium ions, and the MMT nanoplatelets. The permittivity and conductivity spectra of these materials are analyzed for exploring the dominant contribution of electrode polarization and dipolar polarization in the low and high frequency regions, respectively, and the presence of relaxation processes associated with structural dynamics of the solid-state ion–dipolar complexes. It has been found that the NSPE of relatively fast polymer chain segmental dynamics exhibits higher ionic conductivity. The room temperature ionic conductivity of the 13.3 wt% LiBF4 containing SPE is found more than two times higher as compared to that of the SPE film having 9.7 wt% LiBF4. When the MMT is incorporated, the ionic conductivity of 13.3 wt% LiBF4 containing NSPEs enhances by about one order of magnitude at room temperature. The dc ionic conductivity of the 13.3 wt% LiBF4 containing SPE film is found 1 × 10–5 S/cm at 55 °C, whereas it is 1.65 × 10–5 S/cm at 27 °C for the 5 wt% MMT incorporated NSPE film. The significantly enhanced ionic conductivity with ions transference number close to unity, high electrochemical stability voltage window and good reversibility of these NSPE materials confirm their potential applications as ion conductor/separator for the development of all-solid-state ion conducting devices and the lithium-ion batteries.

Six-arm star polymer based on discotic liquid crystal as high performance all-solid-state polymer electrolyte for lithium-ion batteries

All-solid-state polymer electrolyte (SPE) matrices prepared by molecular design are still needed to be further perfected with excellent performance. In this paper, a controlled-structure discotic liquid crystal (DLC)-based six-arm star copolymer was designed and synthesized from a DLC initiator (2,3,6,7,10,11-hexakis(2-bromoisobutyryloxy)triphenylene) via the sequential atom transfer radical polymerization (ATRP) of styrene and poly(ethylene glycol) methyl ether methacrylate (PEGMA). Here, this class of discotic liquid crystal star polymer is applied as an SPE in LIBs for the first time. By solution casting, a suitable self-standing SPE film composed of the six-arm copolymer and lithium bis(trifluoromethanesulfonimide (LiTFSI)) can be easily formed, and the film shows long-range molecular orientation after annealing. It is confirmed that the electrolyte shows wide electrochemical window (5.1 V) and high lithium-ion transference number (0.37). Especially, the ionic conductivity (1.46 × 10−4, S cm−1, 30 °C) of the obtained SPE is more than 8 times higher than that of the corresponding linear copolymer electrolytes. Furthermore, the results of battery performance demonstrate that the polymer electrolyte displays eminently reversible electrochemical reaction and outstanding cycling performance. The present work not only shows the advantages of DLC-based star SPE for LIBs but also paves the way for the design of SPE with excellent performances.

Effect of Lithium Perchlorate on the Optoelectrical and Thermal Properties of Poly(Vinylpyrrolidone)/Nano-Cesium Aluminate Solid Polymer Electrolytes

ABSTRACTSolid polymer electrolyte (SPE) of polyvinylpyrrolidone (PVP) with varying amounts, namely, 5, 10, and 15 wt% of lithium perchlorate (LiClO4) as an electrolyte and 8 wt% cesium aluminum oxide (CsAlO2) nanoparticle have been fabricated by solution intercalation technique. The optoelectrical behaviors of the SPE films have been evaluated using UV–visible spectroscopy. The UV–visible spectral studies revealed the UV light-absorbing nature of NC films with considerable visible transparency. The chemical structure and morphological behaviors of PVP/8 wt% of CsAlO2–LiClO4 SPE films have been established by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, respectively. The AC conductivity of the SPEs was evaluated at room temperature by digital LCR meter in the frequency range 100 Hz–5 MHz. The thermal behaviors such as Tg and degradation patterns of the SPEs have been evaluated using differential scanning calorimetric analysis and thermogravimetric analysis, respectively.

Effects of the electrolyte content on the electrical permittivity, thermal stability, and optical dispersion of poly(vinyl alcohol)–cesium copper oxide–lithium perchlorate nanocomposite solid‐polymer electrolytes

ABSTRACTSolid‐polymer electrolytes (SPEs) in the form of poly(vinyl alcohol) (PVA) doped with various amounts (5, 10, and 15 wt %) of lithium perchlorate trihydrate (LiClO4·3H2O) and 2 wt % cesium copper oxide (Cs2CuO2) nanoparticles were fabricated by a solvent intercalation method. The obtained nanocomposites were evaluated for their chemical structure and microstructural and morphological behaviors via Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy methods, respectively. The obtained dielectric behaviors, alternating‐current conductivity, dielectric modulus, and dielectric relaxation of the SPEs depended on the volume fraction of the electrolyte. Linear behavior of the current–voltage characteristics for all of the SPE films was observed with a slight deviation at a higher voltage. The thermal behaviors of the PVA–Cs2CuO2–LiClO4 films were evaluated by differential scanning calorimetry and thermogravimetric analysis. The refractive index, band‐gap energy, and optical dispersion were examined with UV–visible spectroscopy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45852.

Effects of different inorganic nanoparticles on the structural, dielectric and ion transportation properties of polymers blend based nanocomposite solid polymer electrolytes

Nanocomposite solid polymer electrolyte (NSPE) films consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend (50/50wt%) as host polymer matrix with 20wt% lithium perchlorate (LiClO4) as dopant salt and 3wt% inorganic nanoparticles (i.e., Al2O3, SiO2, SnO2 or ZnO) as filler have been prepared by solution cast method followed by melt-press technique. The X-ray diffraction (XRD) study confirms that the electrolyte films without nanofiller and with Al2O3 and SiO2 nanofillers have predominantly amorphous structures, whereas the characteristic diffraction peaks of SnO2 and ZnO crystallites are observed in the respective NSPEs. Fourier transform infra-red (FTIR) spectra of these NSPE films confirm the formation of ion-dipolar coordination between the functional groups of polymers and the lithium ions throughout the material which completely suppressed the crystalline region absorption peaks of the PEO. The metal oxides of the nanoparticles mainly exhibit van der Waals type interaction with the polymers chains and the ions in the NSPE materials. Effects of a lithium salt as a dopant and the nanoparticles as fillers on the crystalline phase and thermal behaviour of PEO–PMMA blend in these electrolyte materials have also been examined by their differential scanning calorimetry (DSC) measurements.Dielectric and electrical dispersion behaviour of the NSPE films have been characterized by employing dielectric relaxation spectroscopy (DRS) over the frequency range from 20Hz to1MHz and at temperatures 27, 35, 45 and 55°C. The single relaxation peak appeared in the dielectric loss tangent spectra of these electrolytes confirms the ion-dipolar coordinated coupled cooperative chain segmental motion of the PEO and PMMA macromolecules. Lowering in the values of dielectric polarization strength and ionic conductivity has been observed for all the NSPE films as compared to that of the SPE film without nanofiller. A linear correlation between the crystallite sizes of different nanofillers and the dielectric permittivity of NSPE materials has been revealed. It is found that the cooperative polymers chain segmental dynamics becomes slower with the dispersion of nanoparticles in the ion-dipolar complexes which causes a decrease of ionic conductivity of the NSPE films. The correlation observed between the dielectric relaxation time and the ionic conductivity confirms that the ions transport occurs by intra- and inter-chain hopping in these PEO–PMMA blend based electrolytes. Temperature dependent values of relaxation time and dc ionic conductivity of the electrolyte films obey the Arrhenius relation and their activation energies are found in the range 0.22eV to 0.40eV which differ with the types of inorganic nanoparticles dispersed in the NSPEs. The comparative results confirm that the polymers chain segmental dynamics mask the effect of amorphous phase of these materials which contributes in the lithium ions transportation and their mobility. Linear correlation observed between the dielectric permittivity and ionic conductivity values of these NSPEs suggests that the strength of dielectric polarization also plays an important role for the ion transportation process in the solid ion-dipolar complexes. The room temperature ionic conductivity values of these NSPE films are found of the order of 10−5Scm−1 which confirms their suitability as potential candidates in the design and development of all-solid-state devices including the rechargeable lithium-ion batteries. Finally, these experimental results explain in depth the fundamental issues of nanomaterials science that confront the use of various kind of inorganic nanoparticles in the preparation of NSPEs, and the dependence of their ion transportation process on the amorphous phase, dielectric permittivity and the cooperative polymers chain segmental motion, especially for the polymers blend based electrolytes.

Copper–constantan nanoparticles impregnated PEO + PVP:Li+ blended solid polymer electrolyte films for lithium battery applications

Blended polymer composite films of PEO + PVP:Li+ and also embedded with copper–constantan nanoparticles (CC NPs) have been prepared by a solution casting method. Structural and electrical properties are carried out by XRD and impedance analyser. The XRD profiles of the prepared samples revealed their semi-crystalline nature. FT-IR and Raman analysis affirms the complex formation between the polymer and dopant ions. The surface morphological studies and the size evaluation of the inclusive CC NPs which were dispersed in the PEO + PVP:Li+ solid polymer electrolytes have been systematically analysed by SEM and TEM. The ionic conductivity enhancement is observed with increasing the CC NPs concentration in the PEO + PVP:Li+ SPE films. The CC NPs impregnated PEO + PVP:Li+ SPE films were found to result in enrichment of the ionic conductivity than PEO + PVP:Li+ SPE. The maximum obtained ionic conductivity is found to be 1.04 × 10−4 S/cm at the optimised concentration 4 wt% of CC NPs in the composite at RT. 4 wt% CC NPs contained PEO + PVP:Li+ SPE film display superior performance in terms of cell specifications. These results explore the present 4 wt% CC NPs impregnated PEO + PVP:Li+ electrolyte could be suggested as promising candidate for solid state electrochemical device applications.

Stable polymer electrolytes based on polyether-grafted ZnO nanoparticles for all-solid-state lithium batteries

Solid polymer nanocomposite electrolytes composed of polyethylene oxide (PEO) macromolecules, LiN(CF3SO2)2 (LiTFSI) and polyether-grafted nano-ZnO (designated ZnO(PEGME)), are prepared and characterized in comparison with the prototypical PEO–LiTFSI film and that doped with conventional acetate group modified ZnO nanoparticles (designated ZnO(Ac)). High resolution transmission electron microscopic (HRTEM) results show that ZnO nanoparticles are dispersed homogeneously in the present PEO–LiTFSI–ZnO(PEGME) films, while those particles in PEO–LiTFSI–ZnO(Ac) aggregate badly. Atomic force microscopic (AFM) analyses prove that after storage at room temperature for a month, PEO–LiTFSI forms large dendrites while only a small amount of tiny crystals can be observed in the PEO–LiTFSI–ZnO(PEGME) film. In contrast, ZnO(Ac) particles agglomerate around the PEO–LiTFSI dendrites and separate from the original phase. This is the first direct observation on the micromorphology of the SPE films after long-term storage, which elucidates why the PEO–LiTFSI–ZnO(PEGME) electrolyte is much more stable than its counterparts. Conductivity evolutions, Li+ transport number measurements and cycle performances of the above-mentioned three typical films in all-solid-state lithium batteries also suggest that the structural merits of the polyether-grafted nanoparticles render this type of SPEs attractive in the future applications.

A Study to Estimate Tritium Concentrations of 1 Bq/L or Lower in Water Samples

To measure low tritium concentrations in environmental water samples, it is necessary to enrich them by electrolysis. We attempted electrolytic enrichment under the following conditions: (1) A standard water cell and sample water cell are connected in series and enriched using solid polymer electrolytic film (SPE film). (2) The apparatus constant obtained from the standard cell was used to estimate the tritium concentration in the sample water. (3) SPE film was replaced and the electrolytic cell was dismantled, cleaned and set up for every run.We repeated electrolytic enrichments for three different water samples with four replicates per sample. Results confirmed that this method is valid for the estimation of tritium concentrations in environmental water samples.

Photo-polymerized films of lithium ion conducting solid polymer electrolyte for electrochromic windows (ECWs)

Abstract Films of solid polymer electrolyte (spe) have been prepared by the photo-polymerization of the monomer: 2-hydroxyethylmethacrylate (HEMA) simultaneously accompanied by chemical crosslinking with neopentyl glycol which is dissolved in a liquid electrolyte, namely, 1 M LiClO 4 in EC:PC binary solvent mixed in two different volume ratios. The spe films exhibit ionic conductivities greater than 10 −3 Scm −1 at 25°C. Thermal and structural characteristics of the films have been determined by DSC and XRD, respectively. The electrochemical redox behavior of an electrochromic device (PWECD) fabricated with an electrodeposited tungsten oxide film as the primary electrode, a prussian blue film as the counter electrode and a poly(HEMA) based electrolyte film as well as that of the individual components of the device has been examined by cyclic voltammetry. Transmission modulation of ∼60% ( λ =650 nm) shown by the PWECD renders it to be a promising candidate for electrochromic window applications.

Diffusion of dopants in B- and Sb-delta-doped Si films grown by solid-phase epitaxy

The diffusion of δ-function-shaped B- and Sb-dopant spikes in thin Si films grown by solid-phase-epitaxy [(SPE), growth of amorphous film by molecular-beam epitaxy (MBE) at room temperature and subsequent regrowth in situ] during annealing in vacuum is compared to diffusion in films grown by low-temperature (LT) MBE. Diffusion temperatures from 750 to 900 °C, and two-dimensional concentrations of 0.7–1.6×1014 cm−2 have been investigated. The diffusive behavior of dopants in SPE films is found to be qualitatively different from that in films grown by LTMBE. This is related to the vacancylike defects that are intrinsic to growth by SPE but not to growth by LTMBE. Dopant profiles widen significantly during SPE regrowth, making the achievement of δ-function dopant spikes impossible. After a vacuum anneal the diffusion coefficients for both n- and p-type dopants are lower in SPE films than the corresponding values in films grown by LTMBE by up to one order of magnitude. The diffused depth profile of the dopant in LTMBE films shows the characteristic deviation from a pure Gaussian that is expected due to the concentration dependence of diffusion, i.e., a flat top and steep shoulders. In contrast, dopant depth profiles of SPE-grown material show after diffusion a central spike and relatively flat shoulders. The width of the central spike is, after an initial transient that it was not possible to resolve, independent of diffusion time and temperature. This indicates that the SPE material is defective, with the defects acting as traps during diffusion.

Effects of Substrate-Surface Cleaning on Solid Phase Epitaxial Si Films

The effects of two substrate-surface cleaning procedures were studied for solid-phase epitaxy of chemical vapor deposited amorphous Si (a-Si) films with respect to crystalline quality. These a-Si films were deposited on Si (100) wafers after surface cleaning by HF-dipping or in-reactor gas etching. The a-Si films were then crystallized by furnace annealing. The film quality was estimated using several techniques, such as etch-pit density measurements. For the samples etched by HF-dipping, the film crystallinity became worse with increasing film thickness owing to a residual oxide layer at the deposited-film/substrate interface. As a result, the electron mobility decreases with increasing deposited film thickness. For in-reactor gas-etched samples, the residual at the interface was negligible, and the crystallinity of a SPE film was as good as that of bulk Si.