Temperature Ionic Conductivity Research Articles

Poly(Arylene Alkylene)s with Tetrazole Pendants for Alkaline Ion-Solvating Polymer Electrolytes.

Alkaline ion-solvating membranes derived from a tetrazole functionalized poly(arylene alkylene) are prepared, characterized and evaluated as electrode separators in alkaline water electrolysis. The base polymer, poly[[1,1'-biphenyl]-4,4'-diyl(1,1,1-trifluoropropan-2-yl)], is synthesized by superacid catalyzed polyhydroxyalkylation and subsequently functionalized with tetrazole pendants. After equilibration in aqueous KOH, the relatively acidic tetrazole pendants are deprotonated to form the corresponding potassium tetrazolides. The room temperature ion conductivity is found to peak at 19 mS cm-1 in 5 wt. % KOH, and slightly declines with increasing KOH concentration to 13 mS cm-1 in 30 wt. % KOH. Based on an overall assessment of the mechanical properties, conductivity and electrode activity, 30 wt. % KOH is applied for alkaline electrolysis cell tests. Current densities of up to 1000 mA cm-2 were reached with uncatalyzed Ni-foam electrodes at a cell voltage of less than 2.6 V, with improved gas barrier characteristics compared to that of the several times thicker Zirfon separator.

Reasonable design a high-entropy garnet-type solid electrolyte for all-solid-state lithium batteries

Traditional garnet solid electrolyte (Li7La3Zr2O12) suffers from low room temperature ionic conductivity, poor air stability, high sintering temperature and energy consumption. Considering the development prospects of high-entropy materials with high structural disorder and strong component controllability in the field of electrochemical energy storage, herein, a novel high-entropy garnet-type oxide solid electrolyte, Li5.75Ga0.25La3Zr0.5Ti0.5Sn0.5Nb0.5O12 (LGLZTSNO) was constructed by partially replacing the Li and Zr sites in Li7La3Zr2O12 with Ga and Ti/Sn/Nb elements, respectively. The experimental and density functional theory (DFT) calculation results show that the high-entropy LGLZTSNO electrolyte has preferable room temperature ion conductivity, air stability, interface contact performance with lithium anode, and the ability to suppress lithium dendrites. Thanks to the improvement of electrolyte performance, the critical current density of Li/Ag@LGLZTSNO/Li symmetric cell was increased from 0.42 to 1.57 mA cm−2, and the interface area specific impedance (IASR) was reduced from 765.2 to 42.3 Ω cm2. Meanwhile, the Li/Ag@LGLZTSNO/LFP full cell also exhibits excellent rate performance and cycling performance (148 mA h g−1 at 0.1 C and 124 mA h g−1 at 0.5 C, capacity retention up to 84.8% after 100 cycles at 0.1 C), showing the application prospects of high-entropy LGLZTSNO solid electrolyte in high-performance all solid state lithium batteries.

Nanocomposite Solid Polymer Electrolytes with Polymer Blend (PVDF‐HFP/Pluronic) as Matrix and GO as Nanofiller: Preparation, Structural Characterization, and Lithium‐Ion Conductivity Analysis

AbstractNanocomposite solid polymer electrolytes (NSPEs) with PVDF‐HFP/Pluronic as blend polymer matrix, graphene oxide (GO) as nanofiller, and LiClO4 are reported. FTIR spectroscopy reveals the crystal phase transformation of PVDF‐HFP from nonpolar α phase to electroactive γ phase upon salt addition that suggests the ion‐dipole interaction between the salt and the matrix. Further, Pluronic not only hinders the PVDF crystallization that increases the amorphous character of the matrix but also interacts with the salt and hence assists in salt dissociation in the blend matrix. The dc conductivity of PVDF‐HFP/Pluronic/LiClO4 blend SPE improves with increasing the Pluronic content reaching 0.73 × 10−6 Scm−1 at room temperature with 60 wt.% Pluronic. The dispersion of GO in the same blend SPE leads to a significant jump in room temperature ion conductivity (≈1.2 × 10−6 Scm−1) with 0.4% GO. Temperature‐dependent ion conductivity of the NSPEs reveals an Arrhenius type thermally activated process. The dc polarization data indicates that the conductivity is predominantly due to ions. Impedance plots exhibit a distorted semicircle at higher frequency and a tilted spike at lower frequency. The spike is an indication of ion diffusion and electrode polarization effect. Further, GO also has enhanced the mechanical properties of the fabricated NSPEs.

Methyl cellulose-based solid polymer electrolytes with dispersed zinc oxide nanoparticles: A promising candidate for battery applications

Novel solid polymer electrolytes based on methyl cellulose (MC) and magnesium chloride (MgCl₂⋅6H₂O) have been prepared by a solution casting technique. The best conducting polymer electrolyte system has been doped with different amounts of zinc oxide (ZnO) nanoparticles to assess their effect on its properties. Structural studies by FTIR and XRD analysis have revealed complete complexation between the polymer host and the dopant. A polymer electrolyte system with 25 wt% of the salt exhibited the highest room temperature ion conductivity of 1.18 × 10⁻⁴ S cm⁻1 with excellent thermal and dielectric properties. The dispersal of ZnO nanoparticles therein served to enhance the conductivity. SEM micrographs reveal complete dispersion of the nanofiller on the electrolyte surface. A primary battery has been fabricated, and its open-circuit potential and discharge characteristics have been studied. Overall, the prepared electrolytes have excellent properties and may thus be promising candidates for energy storage devices.

High temperature ion conductivity and associated defects in oxygen-octahedral structures

The article presents a detailed study of the dielectric properties and conductivity of the SrTiO3 crystal in the temperature range 350 - 900 K in oxygen-free environment (Ar). The study has established that ionic conductivity that reaches a certain value is carried out by associated carriers. This is accompanied by a noticeable increase in the conductivity activation enthalpy Ha. The data are compared with those for LiNbO3:Zn, Mg crystals. Comparison unambiguously confirms the defects association at high values of ionic conductivity, at least for the case of oxygen-octahedral structures. We have found that the effect does not depend on the specific features of the crystal structure (perovskite in SrTiO3 or pseudoilmenite in LiNbO3). It also does not depend on the charge carrier type (O2− or Li+). We have found a temperature region in ionic conductors where both ionic associates and single carriers determine the character of ion transport. The upper temperature limit for the existence of associates (T**) is the temperature at which kT** > EC, where EC is the binding energy of the associate. At T > T**, the associates are destroyed and ionic conduction is again realized only by single carriers with a corresponding decrease in Ha.

Magnetic bistable organic ionic plastic crystal with room temperature ion conductivity comparable to NASICON and superionic conduction in a broad temperature window

A radical salt experiences crystal–crystal and crystal–plastic crystal phase transitions with magnetic bistability and negative thermal expansion, high room-temperature ion-conduction in crystal phase and superionic conduction in plastic crystal phase.

Semi-interpenetrating-network all-solid-state polymer electrolyte with liquid crystal constructing efficient ion transport channels for flexible solid lithium-metal batteries

The development of the solid-state polymer electrolytes (SPEs) for Li-ion batteries (LIBs) can effectively address the hidden safety issues of commercially used liquid electrolytes. Nevertheless, the unsatisfactory room temperature ion conductivity and inferior mechanical strength for linear PEO-based SPEs are still the immense obstacles impeding the further applications of SPEs for large-scale commercialization. Herein, we fabricate a series of semi-interpenetrating-network (semi-IPN) polymer electrolytes based on a novel liquid crystal (C6M LC) and poly(ethylene glycol) diglycidyl ether (PEGDE) via UV-irradiation at the first time. The LCs not only highly improve the mechanical properties of electrolyte membranes via the construction of network structure with PEGDE, but also create stable ion transport channels for ion conduction. As a result, a free-standing flexible SPE shows outstanding ionic conductivity (5.93 × 10−5 S cm−1 at 30 °C), a very wide electrochemical stability window of 5.5 V, and excellent thermal stability at thermal decomposition temperatures above 360 °C as well as the capacity of suppressing lithium dendrite growth. Moreover, the LiFePO4/Li battery assembled with the semi-IPN electrolyte membranes exhibits good cycle performance and admirable reversible specific capacity. This work highlights the obvious advantages of LCs applied to the electrolyte for the advanced solid lithium battery.

The effect of lithium salt type on ionic conductivity of poly(vinylidene difluoride)-based solid polymer electrolytes

Recently, research on solid polymer electrolytes (SPEs) for lithium-ion batteries (LIBs) has been actively carried out as an alternative to conventional liquid electrolytes that present safety issues such as flammability and explosion. However, the SPEs show relatively low ion conductivity, compared to the liquid electrolytes. In this study, a poly(vinylidene difluoride) (PVDF)-based SPE was prepared by introducing two different electrolytes; one is weak-binding lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt mixture with solvating plastic crystal succinonitrile (SN) and the other is lithium bis(fluorosulfonyl)imide (LiFSI) salts. Among the SPEs studied, the PVDF/LiFSI-containing SPE membrane exhibited the highest room temperature ion conductivity of 1 x 10−3 S/cm, characterized by electrochemical impedance spectroscopy (EIS).

The effect of concentration and ratio of ethylene carbonate and propylene carbonate plasticizers on characteristics of the electrospun PEO-based electrolytes applicable in lithium-ion batteries

In this study, plasticized electrospun fibers have been designed and fabricated as an electrolyte for lithium-ion batteries using electrospinning method. Polyethylene oxide (PEO) and lithium perchlorate were used as polymer matrix and lithium salt, respectively. Ethylene carbonate and propylene carbonate were applied to investigate the effects of the plasticizer concentration and various EC:PC ratios on the characteristics of the as-spun electrolytes. In addition, the influence of fiber orientation was examined on the ionic conductivity of the nanofibrous electrolytes. Results illustrated that compared with PC, EC can lead to a greater fraction of free ions, lower activation energy (Ea) and so more ionic conductivity. However, the highest room temperature ion conductivity of 0.171 mS·cm−1 was obtained for the as-spun electrolyte containing EC:PC (3:1) mixture. Moreover, with the increase of PC content, cycle stability of the electrospun electrolytes faded significantly. Furthermore, the ionic conductivity reduced from 0.212 to 0.020 mS·cm−1 with increasing of the fiber alignment. The results implied that the proposed nanostructured fibers can be a great candidate as free-solvent polymer electrolytes applicable in lithium-ion batteries.

Reversible amorphization under ac electric field and character of conductivity of TlInTe2 crystal at ionic conductivity temperature

Temperature dependence of x-ray diffraction (XRD) investigation of crystal over a wide temperature interval (300–570 K) reveals a sequence of phase transitions, including ferroelectric (300–370 K) and ionic conductivity (485–500 K) phase transitions (FPT and ICPT), which are caused by shifting and thermal activation of ions inside of Thomson cube cages of unit cells. The results of XRD versus temperature studies confirm our previous investigations of this crystal (Alekperov O Z et al 2018 J. Appl. Phys. 123 135701) by means of the impedance spectroscopy (IS) method. Temperature dependence of almost all the reflexes’ intensity in XRD data was investigated up to a few tens of Kelvin higher than the so called ionic conductivity (IC) temperature. Intensities of almost all reflexes decrease with increasing the temperature up to K, and reach a minimum at K, corresponding to the maximum of at FPT. The same strong decrease of intensity takes place for reflex 110 at K, which corresponds to Tl+ -ion activation along the chain direction of crystal. A small decrease of the 221 reflex intensity at IC temperature is also observed. The reflexes, intensities of which were almost not changed, are 220 and 440. Room temperature XRD measurements, which were performed in wide temperature interval under alternate electric field with amplitude and frequency 0.5 MHz applied along c-direction of the crystal . Our measurements show a partial amorphization of structure which relaxes back during a few days gradually to more perfect tetragonal structure with XRD reflex intensities higher than the initial reflexes. By analyzing the results of IS and conductivity measurements in wide- and narrow-gap semiconductors on the example of rubidium nitrate () and thallium indium telluride () crystals correspondingly, it was shown that the definition of super ionic conductivity is completely inapplicable, since a high conductivity in these semiconductors originates from increase of free electrons concentration.

Polymeric polyhedral oligomeric silsesquioxane ionic liquids based solid polymer electrolytes for lithium ion batteries

In this work, we have successfully synthesized a novel imidazolium polymeric ionic liquid containing polyhedral oligomeric silsesquioxane and use it as host polymer to develop novel solid polymer electrolytes with high room temperature ionic conductivity, good cycle performance and rate capability. The polymeric polyhedral oligomeric silsesquioxane ionic liquids based solid polymer electrolytes exhibit highest room temperature ion conductivity up to 4.82 × 10−4 S cm−1 and outstanding electrochemical stability up to 5 V relative to Li+/Li. Moreover, the Li/LiFePO4 cells containing the novel solid polymer electrolytes exhibit excellent cycle performance and rate capability, delivering an initial discharge capacity of about 151.8 mAh g−1 at a rate of 0.1 C at room temperature with excellent capacity retention after 100th cycles.

Nanostructured Li-Rich Fluoride Coated by Ionic Liquid as High Ion-Conductivity Solid Electrolyte Additive to Suppress Dendrite Growth at Li Metal Anode.

Blending additive with electrolyte is a facile and effective method to suppress anode dendrite growth in Li metal batteries (LMBs), especially when a LiF-rich solid electrolyte interface (SEI) is formed as a consequence of additive decomposition or deposition. However LiF still suffers from poor bulk ion conductivity as well as the difficult access to tailored nanostructure. Exploring new Li fluoride of high Li-ion conductivity as SEI component is still a big challenge in view of the lacking of desired structure prototype or mineral phase. Here, we propose a Li-rich Li3AlF6 derivative from cryolite phase as solid electrolyte additive, which is characterized by textured nanoporous morphology and ionic liquid coating. Its room temperature ion conductivity is as high as ∼10-5 S/cm with a low activation energy of 0.29 eV, the best level among fluoride-based solid electrolytes. These features guarantee a homogenization of Li+ fluxing through bulk and grain boundary of Li3AlF6-rich SEI and reinforce the effect on Li dendrite suppression. Li3AlF6 additive enables a stable cyclability of Li∥Li symmetric cells for at least 100 cycles even under a high areal capacity of 3 mA h/cm2 and a significant improvement on capacity retention for various LMBs based on LiFePO4, FeS2, and S cathodes.

1,2,3-Triazole mediated Li+-ion conductivity in poly(ethylene oxide) based electrolytes

Poly(ethylene oxide) (PEO) based electrolytes are of great importance for applications in electrochemical devices. Since their ion conductivity is severely hampered by crystallization, several approaches are carried out to enhance the low temperature ion conductivity of PEO such as the addition of polar solvents or the synthesis of more complex polymer architectures. In this study, solvent-like defects are introduced in the center of the PEO chain to reduce its crystallinity with the aim to enhance ion conductivity. The ion conductivities of four polymer electrolytes, containing either a 1,4-disubstituted 1,2,3-triazole (TR) or ortho-, meta- or para-disubstituted benzene defects are measured by impedance spectroscopy after addition of lithium perchlorate (LiClO4, EO:Li=50:1) to the polymer. The TR containing sample shows a 15 to 700 times higher ion conductivity at T=−10°C as compared to the benzene containing PEOs with different substitution pattern. This can be explained by the lower glass transition temperature of the TR containing electrolytes compared to the benzene containing electrolytes. Furthermore, the dependence of the ion conductivity on the LiClO4 concentration in the melt at T=70°C is studied for TR containing electrolytes and compared to the respective defect free PEO22 electrolytes. The electrolytes with the TR defect have higher conductivities in the concentration range (50:1≥EO:Li≥8:1) compared to the uninterrupted PEO22 revealing that the incorporation of a solvent-like defect with high dielectric constant into a PEO chain is an effective strategy to enhance the ion conductivity of PEO electrolytes. This is also supported by 7Li NMR spectroscopy showing that LiClO4 is soluble 1,2,3-triazole but insoluble in benzene. Additionally, 1,2,3-triazoles can also coordinate Li+-ions and, thus, actively contribute to the transport of the Li+-ions.

Extended x-ray absorption fine structure spectroscopy and x-ray absorption near edge spectroscopy study of aliovalent doped ceria to correlate local structural changes with oxygen vacancies clustering

This study provides atomic scale insight to understand the role of aliovalent dopants on oxygen vacancies clustering and dissociation mechanism in ceria system in order to enhance the performance of oxy-ion conductor. Dopants induced microscale changes in ceria are probed by extended X-ray absorption fine structure spectroscopy, X-ray absorption near edge spectra, and Raman spectroscopy. The results are explored to establish a correlation between atomic level structural changes (coordination number, interatomic spacing) → formation of dimer and trimer type cation-oxygen vacancies defect complex (intrinsic and extrinsic) → dissociation of oxygen vacancies from defect cluster → ionic conductivity temperature. It is a strategic approach to understand key physics of ionic conductivity mechanism in order to reduce operating temperature of electrolytes for intermediate temperature (300–450 °C) electrochemical devices for the first time.

Research Progress on Interface Properties of Inorganic Solid State Lithium Ion Batteries

The development of solid-state lithium offers a fundamental solution to safety concerns of liquid electrolyte for lithium battery, because of the non-flammability of solid electrolyte. With society's increasing demand for large size lithium ion batteries and a growing concern about the safety of batteries, the development of solid lithium battery is imminent. To prepare solid lithium battery with excellent performance, we should obtain solid electrolyte with high ambient temperature ion conductivity and make a good contact between electrode and solid electrolyte. Most studies have been focus on the prep- aration of solid electrolyte with high ambient temperature ion conductivity. Although the conductivity of recently discovered solid electrolyte are comparable with those observed for liquid electrolytes. The high-rate capability of solid-state lithium batteries is still poor. This fact tell us that the rate-controlling step is at the interface between the electrode and the electrolyte materials. Only a few researchers have studied the interface between the electrode and the electrolyte materials. This paper introduces some oxide and sulfide electrolyte with high ambient temperature ion conductivity briefly. We mainly analyze the reasons for the high impedance at the interface between electrode and solid electrolyte, and furthermore, we investigate the modification methods to reduce the interface resistance.

The Effect of LiCF<sub>3</sub>SO<sub>3</sub> Complexed MG30-PEMA Blend Solid Polymer Electrolyte

In this work, solid polymer electrolyte compose of blended 30% poly (methyl methacrylate) grafted natural rubber (MG30)-poly (ethyl methacrylate) (PEMA) polymer blend doped with Lithium trimethasulfonate (LiCF3SO3) films were prepared by solution casting technique. . FTIR analysis showed that the interactions between lithium ions and oxygen atoms occur at the carbonyl functional group C=O where there is shifting in wavenumber from 1728 cm-1of pure blend to lower wavenumber of blended MG30-PEMA on the MMA structure in both MG30 and PEMA. DSC analysis showed miscibility of polymer blend. From Electrochemical Impedance Spectrocopy analysis, ionic conductivity increase with the increasing of salt concentration. Maximum conductivity at room temperature is 9.20 x 10-6Scm-1was obtained when 30 wt% of LiCF3SO3was added into the system. Ionic conductivity temperature dependence plots found obeys the Arrhenius rule.

Switchable electrolyte properties and redox chemistry in aqueous media based on temperature-responsive polymers

Macromolecular ionomer solutions exhibiting macroscopic properties that change in response to temperature are referred to as thermally responsive polymer electrolytes (RPEs). Such materials provide a means to control electrochemical systems using an external stimulus that affects the polymer phase behavior and electrolyte properties. RPEs were synthesized with N-isopropylacrylamide, which governs the thermal properties, and varying fractions of acrylic acid, which provides ionic properties. These polymers undergo a thermally activated phase separation in aqueous solutions at a given temperature, thereby altering the ionic strength, pH, and conductivity of the electrolyte solution. In this article, we demonstrate how the molecular properties of RPEs, specifically the ionic composition, influence the temperature-dependent electrolyte properties and the extent to which these electrolytes can control the activity of redox electrodes. Materials with high ionic content provide the highest room temperature ion conductivity and redox activity; however, RPEs with low ionic content provide the highest “on–off” ratio in electrochemical activity at elevated temperatures.

Lithium Conducting, Polar-Polar Polymer Blend Electrolytes with Systematically Varied Mechanical Properties and Ion Conductivity

Highly polar polymers such as PEO (polyethylene oxide)1-5 and PVDF (polyvinylidene difluoride)6-10 are well known as potential candidates for solid -state and gel-type electrolytes in rechargeable lithium-ion batteries, although the high crystallinity of these semi-crystalline, polar polymers leads to large polymer crystallites or crystalline domains which significantly lower their room-temperature ion conductivities.1-10 Hybrid polar-polar polymer blends, on the other hand, were previously reported to reduce the crystallinity of both polymer component, if a proper window of blend ratio is chosen. 11-13 This approach is more favored than an inert additive approach, in which inactive components that are not beneficial to ion transport are introduced to the electrolyte systems. Abraham, et al., reported the high ion conductivity of a polymer blend electrolyte made up with poly(vinylidene fluoride-co-hexafluoropropylene) or PVDF-HFP, oligomeric poly(ethylene glycol) dimethyl ether and lithium salts. In addition, Han, et al, studied ion transport of nanoparticle modified PEO/PVDF blends for dye-sensitized solar cell13. Several other reports examined ion transport behaviors in PEO/P(VDF-HFP)/lithium perchlorate (LiClO4) blend electrolytes.12 , 14 , 15 However, none of these reports provided a systematic and detailed nanostructure-ion transport correlation of polar-polar polymer hybrid electrolytes.Herein we studied PEO-PVDF- LiTFSI (lithium bis(trifluoromethanesulfonyl) imide) based hybrid electrolytes with systematically tunable mechanical properties and room temperature ion conductivities. We examined the nano- morphology dependent ion transport of these important type of composite electrolytes and their behaviors in solid polymer electrolyte systems. Based on results from a variety of experiments including nanoidentation, wide-angle X-ray diffraction, energy filtered TEM, and temperature-dependent impedance spectroscopy, we demonstrate that the low temperature ion conductivity of PEO/PVDF/LiTFSI blend can be 3 times higher than their parent electrolytes because of the largely optimized nanomorphology and mitigated polymer crystallinity. At the same time, we also show that, the modulus and hardenss of these blend electrolytes can be systematically tuned with the polymer blend ratio.(The attached energy filtered composite TEM images show oxygen, fluorine, and nitrogen distribution as a function of PVDFwt% in PEO/LiTFSi electrolytes.)1. Lascaud, S.; Perrier, M.; Vallee, A.; Besner, S.; Prudhomme, J.; Armand, M., Macromolecules 1994, 27, 7469-7477.2. Vallee, A.; Besner, S.; Prudhomme, J., Electrochimica Acta 1992, 37, 1579-1583.3. Gorecki, W.; Jeannin, M.; Belorizky, E.; Roux, C.; Armand, M., J. Physics-Condensed Matter 1995, 7, 6823-6832.4. Agrawal, R. C.; Pandey, G. P., J. Physics D-Applied Physics 2008, 41.5. Marzantowicz, M.; Dygas, J. R.; Krok, F.; Nowinski, J. L.; Tomaszewska, A.; Florjanczyk, Z.; Zygadlo-Monikowska, E., J. Power Sources 2006, 159, 420-430.6. Jiang, Z.; Carroll, B.; Abraham, K. M., Electrochimica Acta 1997, 42, 2667-2677.7. Kim, K. M.; Ryu, K. S.; Kang, S. G.; Chang, S. H.; Chung, I. J., Macromolecular Chem Phys 2001, 202, 866-872.8. Saikia, D.; Kumar, A., Electrochimica Acta 2004, 49, 2581-2589.9. Ramesh, S.; Lu, S.-C., J Molecular Structure 2011, 994, 403-409.10. Abbrent, S.; Plestil, J.; Hlavata, D.; Lindgren, J.; Tegenfeldt, J.; Wendsjo, A., Polymer 2001, 42, 1407-1416.11. Abraham, K. M.; Jiang, Z.; Carroll, B., Chem Mater 1997, 9, 1978-1988.12. Jacob, M. M. E.; Prabaharan, S. R. S.; Radhakrishna, S., Solid State Ionics 1997, 104, 267-276.13. Han, H. W.; Liu, W.; Zhang, J.; Zhao, X. Z., Adv Funct Mater 2005, 15, 1940-1944.14. Deka, M.; Kumar, A., Bulletin of Materials Science 2009, 32, 627-632.15. Fan, L. Z.; Dang, Z. M.; Nan, C. W.; Li, M., Electrochimica Acta 2002, 48, 205-209. Acknowledgements A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, Office of Basic Energy Sciences, U.S. Department of Energy.

Improved thermal and electrochemical performances of PMMA modified PE separator skeleton prepared via dopamine-initiated ATRP for lithium ion batteries

In this work, PMMA layer was immobilized onto PE separator skeleton via surface-initiated ATRP based on dopamine pretreatment. The incorporated “active” layer made separator matrix could be swollen by electrolyte solution to some extent and show some properties of gel polymer electrolyte. Resulted separators were characterized by ATR-FTIR, SEM, contact angle and electrochemical methods. The prepared separators showed improved thermal stability. The electrolyte uptake and ionic conductivity were also elevated due to the improved affinity between separator and liquid electrolyte. The room temperature ion conductivity reached up to 1.19×10−3Scm−1. The stability of liquid electrolyte trapped in the separator was enhanced obviously. Cells assembled with such “active separators” showed better cycle performances. These results primarily showed that it was a promising way to prepare high performance PE based separators for lithium ion batteries.

Dielectric properties and electrical conductivity of Li0.07Na0.93Ta0.1Nb0.9O3 and Li0.07Na0.93Ta0.111Nb0.889O3 ferroelectric solid solutions

The dielectric properties and electrical conductivity of the ferroelectric perovskite solid solutions Li0.07Na0.93Ta0.1Nb0.9O3 and Li0.07Na0.93Ta0.111Nb0.889O3 have been studied at temperatures from 290 to 700 K and frequencies from 25 Hz to 1 MHz. In this temperature range, the solid solutions undergo a first-order ferroelectric phase transition. Li0.07Na0.93Ta0.111Nb0.889O3 (prepared from coprecipitated Ta2yNb2(1 − y)O5 pentoxides) has a markedly lower Curie temperature (by ∼75 K) and higher ionic conductivity and high-frequency dielectric permittivity in comparison with Li0.07Na0.93Ta0.1Nb0.9O3 (prepared from a mechanical mixture of Ta2O5 and Nb2O5).