Temperature Dependence Of Ionic Conductivity Research Articles

Coaxially spinning spiral coils into concentric microtubes to synchronize motion and temperature sensing for stretchable and wearable device

Wearable electronical sensors with the combination of multi-mode sensing, stretchability and stability have long been in pursuit for various applications, such as the strain and temperature sensing for health assessment and disease diagnosis. To design endurable dual-mode sensor without signal interference, in this study, a coaxial wet spinning process were suggested to spin helical fibers into concentric double-layer microtubes to synchronize motion and temperature sensing with negligible signal interference. The inner helical fiber showed a high temperature-dependent ionic conductivity for the sensitivity of 5.76 % °C−1 and detection limit of 0.1 °C. Its helical geometry ensured large stretchability and minimal strain-induced interference. The outer coating shell could serve as the strain sensor with a high gauge factor of 11.36–1512 (up to 300 % strain) and response time of 120 ms. When filling the microtubes with polydimethylsiloxane, the multi-mode sensos could stay stable sensing abilities up to 104 stretching-release cycles. Thus, this study not only offers a coaxial spinning approach for production of stretchable multicomponent fibers, but also shows an unprecedented alternative of dual-mode sensor for healthcare, rehabilitation, and sleep monitoring.

Estimation of Ionic Impurities in Poly(propylene Glycol) Diacrylate Monomers/Liquid Crystal E7 Mixtures Using Dielectric Spectroscopy

The study investigated the effect of the molecular weight of three difunctional poly(propylene glycol) diacrylates on the temperature-dependent ionic conductivity of these monomers and their blends with an eutectic nematic liquid crystal mixture (E7). The results revealed two distinct regions. At low temperatures, ionic conduction can be described by the Vogel–Tamman–Fulcher (VTF) equation, while at high temperatures, the conductivity data follow the prediction of the Arrhenius model. The Arrhenius and VTF parameters and their corresponding activation energies were determined using the least squares method. In addition, a conductivity analysis based on an ionic hopping model is proposed. Estimates of ion concentrations and diffusion constants were calculated. It was found that both the ionic concentration and the diffusion constant decrease with the increase in the molecular weight of the monomers. The static dielectric permittivity decreases in the following order: TPGDA, PPGDA540, and PPGDA900. This can be explained by the higher dipole moment of TPGDA, which is caused by an enhanced volume density of carbonyl groups.

Phase transitions of choline dihydrogen phosphate: A vibrational spectroscopy and periodic DFT study.

Choline dihydrogen phosphate, [Chol][H2PO4], is a proton-conducting ionic plastic crystal exhibiting a complicated sequence of phase transitions. Here, we address the argument in the literature around the thermal properties of [Chol][H2PO4] using Raman and infrared microspectroscopy. The known structure of the low-temperature crystal, which contains the anti-conformer of [Chol]+ and hydrogen-bonded dimers of anions, was used to do periodic density functional theory calculations of the vibrational frequencies. Raman spectra indicate that the solid-solid transition at 20 °C is linked to a conformational change to the gauche [Chol] conformer with a concurrent local rearrangement of the anions. The distinct bands of lattice modes in the low-frequency range of the Raman spectra vanish at the 20 °C transition. Given the ease with which metastable crystals can be produced, Raman mappings demonstrate that a sample of [Chol][H2PO4] at ambient temperature can contain a combination of anti- and gauche conformers. Heating to 120 °C causes continuous changes in the local environment of anions rather than melting as suggested by a recent calorimetric investigation of [Chol][H2PO4]. The monotonic change in vibrational spectra is consistent with earlier observations of a very small entropy of fusion and no abrupt jump in the temperature dependence of ionic conductivity along the phase transitions of [Chol][H2PO4].

Aliphatic Hyperbranched Polycarbonates Solid Polymer Electrolytes with High Li-Ion Transference Number for Lithium Metal Batteries.

In this work, hyperbranched polycarbonate-poly(ethylene oxide) (PEO)-based solid polymer electrolytes (HBPC-SEs) are successfully synthesized via a straightforward organo-catalyzed "A1"+"B2"-ring-opening polymerization approach. The temperature-dependent ionic conductivity of HBPC-SEs, composed of different polycarbonate linkages and various LiTFSI concentrations, is investigated. The results demonstrate that HBPC-SE with an ether-carbonate alternating structure exhibits superior ionic conductivity, attributed to the solubility of Li salts in the polymer matrix and the mobility of the polymer segments. The HBPC1-SE with 30 wt% LiTFSI presents the highest ionic conductivities of 2.15 × 10-5, 1.78 × 10-4, and 6.07 × 10-4 Scm-1 at 30, 60, and 80 °C, respectively. Compared to traditional PEO-based electrolytes, the incorporation of polycarbonate segments significantly enhances the electrochemical stability window (5V) and Li+ transference number (0.53) of HBPC-SEs. Furthermore, the LiFePO4/HBPC1-SE-3/Li cell exhibits exceptional rate capability and long-cycling performance, maintaining a discharge capacity of 130 mAh g-1 at 0.5C with a capacity retention of 95% after 300 cycles.

A tough, anti-freezing, and low-dehydration rate gelatin hydrogel with inverse temperature-dependent ionic conductivity

By using Cit3− and Cl− salts together in a gelatin hydrogel, an inverse temperature-dependent ionic conductivity behavior was observed. The developed hydrogel II exhibited excellent mechanical toughness, freezing tolerance and low dehydration rate.

Electrochemical investigations of PVdF-HFP-NaTFSI-[BMPYr][TFSI] polymer-salt-IL electrolyte for Na-rechargeable battery

Sodium-ion batteries (SIBs) are being aggressively pursued for potential use in energy storage systems due to the natural abundance and low cost of sodium. In the present investigation, structural, thermal and electrochemical properties of a ionic liquid based Na-ion conducting polymer-salt-IL electrolytes (IL-NCPEs) formed using copolymer poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) salt along with IL; 1-butyl-1-methypyrrolidinium bis(trifluoromethanesulfonyl)imide ([BMPYr] [TFSI]) is being reported. The samples were characterized using ionic conductivity, transference number measurement, thermal & electrochemical studies as a function of wt% IL. Incorporated [BMPYr][TFSI]-IL in the NCPE (i.e., PVdF-HFP + 10 wt% NaTFSI) modifies the different physicochemical properties such as complex formation, thermal, transport and electrochemical properties. The ionic conductivity of prepared IL-NCPEs has been found to increase with increasing the content of [BMPYr][TFSI]-IL and reaches to a maximum value of ∼0.85 mS/cm (at 30 °C). Also, the temperature dependent ionic conductivity obeys Arrhenius type thermally activated behaviour. For the optimized [BMPYr][TFSI]-IL, compatibility of IL-NCPEs with Na-metal electrode, high total ionic transference number (tionic ∼ 0.98), cationic transference number (tNa+ ∼ 0.31) and wide electrochemical stability (ESW ∼ 4.0 V) have been obtained. The above obtained properties of the prepared IL-NCPEs are promising for application in Na-rechargeable battery.

Non-Arrhenius Ionic Conductivity Behaviour in Antiperovskite Solid Electrolytes for Sodium Metal Batteries

Solid-state sodium metal batteries have been proposed as an alternative to lithium-ion batteries (LIBs) for next-generation applications due to the high abundance and wide distribution of sodium resources.1 Sodium antiperovskites (Na3OX, X = Cl, Br, or BH4) have recently attracted great interest as solid electrolyte candidates due to the relatively low processing temperature (<500 oC), reasonable ionic conductivity (up to 4.4 x 10-3 S cm-1 at room temperature), and great chemical stability against sodium metal anodes.2,3 Typical solid-state ionic conductors have temperature-dependent ionic conductivity that follows Arrhenius behaviour over a broad range of temperatures, corresponding to a constant activation energy Ea. However, this is not the case in Na3OBr, and instead a phenomenon resulting in a higher ionic conductivity and lower activation energy is observed to occur at 255 oC. Similar non-Arrhenius ionic conductivity phenomenon has also been reported in the potassium antiperovskite K3OI. It has been proposed that this behaviour originated from anion disordering, but conclusive experimental evidence to support this claim has not been reported.4 An understanding of the origin of this behaviour could enable the synthesis route to be optimised such that higher ionic conductivities could be achieved.In this work, we combined temperature-resolved bulk and local characterisation methods including Pawley and Rietveld refinements of synchrotron x-ray diffraction (XRD), pair distribution function (PDF), solid-state nuclear magnetic resonance (NMR) spectroscopy, and electrochemical impedance spectroscopy (EIS) to gain an insight into the origin of this non-Arrhenius behaviour. We found that this phenomenon does not originate from anion disordering, as previously speculated, because the lattice parameter of Na3OBr changed linearly with temperature and no major intensity changes were observed in the Na-Br and Na-O signals in the PDF patterns. Other supporting findings that lead us to this conclusion will be discussed in the presentation.References Wang, X. et al. Ultra-stable all-solid-state sodium metal batteries enabled by perfluoropolyether-based electrolytes. Nat. Mater. 21, 1057–1066 (2022).Zheng, J., Perry, B. & Wu, Y. Antiperovskite Superionic Conductors: A Critical Review. ACS Mater. Au 1, 92–106 (2021).Sun, Y. et al. Rotational Cluster Anion Enabling Superionic Conductivity in Sodium-Rich Antiperovskite Na3OBH4. J. Am. Chem. Soc. 141, 5640–5644 (2019).Zheng, J. et al. Antiperovskite K3OI for K-Ion Solid State Electrolyte. J. Phys. Chem. Lett. 12, 7120–7126 (2021).

Exploration of Variable Solvent Directed Self-Healable Supramolecular M(II)-Metallogels (M = Co, Ni, Zn) of Azelaic Acid: Investigating Temperature-Dependent Ion Conductivity and Antibacterial Efficiency.

Molecular self-assembly assisted self-healing supramolecular metallogels of azelaic acid with cobalt(II)-, nickel(II)-, and zinc(II)-based metal acetate salts were successfully fabricated. Individually, N,N'-dimethylformamide and dimethyl sulfoxide were immobilized within these distinctly synthesized soft-scaffolds of metallogels to attain their semisolid viscoelastic nature. Rheological experiments such as amplitude sweep, frequency sweep, and thixotropic measurements were executed for these metallogels to ratify their gel features. The different extents of supramolecular interactions operating within these solvent-directed metallogels were clearly reflected in terms of their distinct morphological patterns as investigated through field emission scanning electron microscopy. Comparative infrared (IR) spectral properties of metallogels along with individual metal salts and azelaic acid were analyzed. These experimental data clearly depict the significant shifting of Fourier transform (FT)-IR peaks of xerogel samples of different metallogels from the gel-forming precursors. The networks present within the soft-scaffold are evidently illustrated by the electrospray ionization-mass experimental data. The temperature-dependent ionic conductivity studies with these solvent-directed versatile metallogel systems were investigated through impedance spectroscopy. The temperature-dependent impedance spectroscopic studies clearly demonstrate that the ion-transportation within the gel matrix depends not only on the types of cations but also on the dielectric properties of the immobilized solvents. The antipathogenic effect of these metallogel systems has also been explored by testing their effectiveness against human pathogenic Gram-negative bacteria Klebsiella pneumoniae (MTCC 109) and Vibrio parahemolyticus, and Gram-positive bacteria like Bacillus cereus (MTCC 1272). These gel soft-scaffolds show no significant cytotoxicity against both the human neuroblastoma cell line-SH-SY5Y and the human embryonic kidney cell line-HEK 293.

Investigation on polyvinyl alcohol and sodium alginate blend matrix with ammonium nitrate conducting electrolytes for electrochemical applications

Polyvinyl alcohol (PVA) Sodium alginate (NaAlg) polymer composites were synthesized by solution casting technique and doping with ammonium nitrate (NH4NO3). The functionalization structure of the produced electrolytes was investigated using XRD and AC impedance spectroscopy. XRD confirms amorphous nature. The ionic conductivity of the electrolytes is evaluated using ac impedance measurements at temperatures ranging from 303 to 353 K. PVA: NaAlg: NH4NO3 (60:40:15 wt%) blend polymer electrolyte was observed to have the highest conductivity of 1.05 × 10−6 S cm−1. The Arrhenius plot appears to be obeyed by the temperature dependent ionic conductivity and is of non-debye type. Activation energy for best conducting electrolyte was 0.2364 eV. The dielectric relaxation of the polymer electrolyte has been studied, and the results are described. Relaxation time estimated from loss tangent analysis also affirms that value is low for highest conducting sample. Results of CV and LSV studies gave a plausible approach for electrochemical application.

Studies on a novel microporous electrospun poly(vinyl alcohol)‐based polymer electrolyte membranes for high‐performance battery applications

AbstractINTRODUCTIONSolid polymer blend electrolytes are scientifically interesting promising materials as electrolytes in advanced solid state electrochemical devices applications such as batteries, electrochemical display devices, smart windows, etc. The solid polymer blend electrolyte has several advantages including high energy density, a solvent free condition, structural stability, light weight, leak proof, good electrode electrolyte contact, ease of fabrication, easy processability and good mechanical properties.OBJECTIVESThe present research work deals with the study of composition and conductivity behavior of polymer blend electrolyte complex membranes based on PVA and PVP complexed with different weight percent KClO4 salt, prepared by electrospinning technique. The resultant polymer blend electrolytes have been characterized by XRD, FTIR and AC conductivity studies.METHODSPorous PVA based nanofiber membranes were prepared using a typical electrospinning technique with a horizontal arrangement. A stainless steel needle (24 G, outer diameter: 0.50 mm, inner diameter: 0.35 mm) was connected to an electrode of a high voltage power supply (Spellman, model CZE1000R) which could generate positive DC voltages up to 30 kV and a grounded stainless steel plate was placed at 10 cm distance from the needle tip to collect the nanofiber membranes.RESULTS AND DISCUSSIONA novel electrospun polymer electrolyte membranes comprising a blend of poly (vinyl alcohol) (PVA) and poly (vinyl pyrrolidone) (PVP) containing various concentrations of potassium perchlorate KClO4 salt are prepared using electrospinning technique. The structure and complexation of the polymer electrolyte membranes have been confirmed from X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectral studies. The ac conductivity studies are performed to measure the ionic conductivity of the polymer electrolyte complex systems in the temperature range 298‐353 K and it is also found that the temperature dependence ionic conductivity data seems to follows the Arrhenius relation. The influence of complex membranes composition on the ionic conductivity has been discussed. The maximum ionic conductivity value is obtained to be 9.1×10−4 S cm−1 at 298 K for PVA‐PVP‐KClO4 (50‐35‐15) polymer system with 15 wt.% KClO4 salt. Scanning electron microscopy studies have been performed and reported.CONCLUSIONSFree standing, flexible complex polymer electrolyte membranes based on various compositions of PVA‐PVP‐KClO4 have been prepared. The presence of amorphous regions due to complexation of polymer salt matrices has been confirmed from XRD and FTIR analysis. The maximum value of ionic conductivity has been obtained to be 9.1 × 10−4 S cm−1 at 298 K for PVA‐PVP‐KClO4 (50‐35‐15) complex polymer electrolyte system with 15 wt.% KClO4. The excellent performance, such as high values of ionic conductivity, of polymer blend electrolyte membranes suggest that the membranes can be used as the best candidate for high performance solid state batteries.

Electrochemical Characterization of Thiophosphate- Ionic Liquid Hybrid Lithium Electrolytes Against Li Metal

(Almost) solid-state batteries that utilize thiophosphate solid electrolytes (SE) are an exciting technology emerging as a potential alternative to lithium-ion batteries. When used alongside a lithium metal anode they can offer the high energy densities [1] required to meet the increasing demand for energy storage. However, they suffer from numerous issues which predominately occur at the cathode- or anode-SE interface. Issues include dendrite propagation through gaps, pores and grain boundaries of the solid electrolyte which can eventually puncture electrolyte crystallites and lead to cell failure. [2] Thiophosphate electrolytes are also unstable both chemically and electrochemically. As a result of the SEs having a low electrochemical stability window reduction or oxidation can occur at the anode or cathode interface, forming a resistive solid electrolyte interphase (SEI). [3] Finally, the ionic contact between Li metal anode and electrolyte is poor and thus high interfacial impedances can arise. These impedances can be dynamic which increase during stripping of the lithium and decrease during plating. [4] To solve some of the interfacial issues there is the option to add a small of amount of liquid electrolyte at the lithium metal-electrolyte interface. The liquid electrolyte can fill in the gaps and pores at the interface thus improving the ionic contact whilst allowing a more stable interface. Whilst the ionic contact can be improved the inherent instability of thiophosphate electrolytes against the liquid electrolyte means that a new interphase known as the solid-liquid electrolyte interphase (SLEI) can form. The presence of this interphase can therefore lower the energy density and round-trip efficiencies of cells which utilize hybrid electrolytes meaning that minimizing the SLEI resistance and maximizing total ionic conductivities is important in hybrid cells. [5]In this work a hybrid of the thiophosphate argyrodite Li6PS5Cl and the ionic liquid x-LiTFSI-1-butyl 1-methylpiperidinium TFSI (BMPipTFSI) with LiTFSI concentrations of 0.25 M and 0.5 M was studied. The choice of SE and liquid electrolyte boils down to the high ionic conductivity of the SE and the electrochemical and thermal stability of the ionic liquid. Temperature-dependent ionic conductivity measurements showed that hybrid systems exhibit lower in room temperature ionic conductivities and higher total activation energies. This hints at the presence of a SLEI forming between the LE and SE. To study how the SLEI resistances changes over time, ion blocking potential impedance spectroscopy measurements were performed. These measurements were performed at 10 °C to allow for the resistance contributions to be better resolved and showed a SLEI resistance of around 45-50 Ω cm2 for both hybrids. Over the period of 130 hours this resistance changed minimally (around 5 Ω cm2 on average) indicating good stability of the SLEI. To further test the suitability of this hybrid alongside lithium metal anodes impedance measurements in symmetrical lithium cells (Li0|LE|LPCL|LE|Li0) were undertaken. In this case galvanostatic impedance spectroscopy (GEIS) with an applied current density of ±0.4 mA cm-2 was used to probe the changes in resistance contributions in the system over the period of stripping (positive current) and plating (negative current). For cells with just SE a large change in the resistance owing to the electrochemical reaction (ECR) (Li0 ↔ Li+ + e-) occurred during stripping and plating indicating the dynamic nature of the ionic contact at the interface. For the hybrid electrolyte cells, this ECR resistance is decreased and becomes more stable however a larger interphase resistance is present. This resistance is a combination of the resistances of both the SLEI (the interphase between the LE and SE) and the SEI (the interphase between LE and Li anode) and it changes over stripping and plating showing that the S(L)EIs which are present are dynamic. Finally, post-mortem SEM/EDX of the surface of samples show a change in morphology and the presence of decomposition products from both the liquid and solid electrolytes. These studies show that the LPCL-BMPipTFSI hybrid is stable and improve ionic contact at the lithium metal anode interface. Further testing in half Li-S cells will determine the suitability of the use of the ionic liquid at the cathode side of the cell.

Transparent, self-adhesive, highly environmental stable, and water-resistant ionogel enabled reliable strain/temperature sensors and underwater communicators

Electronic skins have gained considerable attentions for their promising applications in flexible and wearable electronics. Nevertheless, it remains challenging to realize high performance underwater sensing due to the great differences between the aquatic environment and the land environment. Herein, we developed hydrophobic ionogel consisting of hydrophobic polymer network and ionic liquid with high transparency, good stretchability, temperature-dependent ionic conductivity, long-term environmental stability, and excellent adhesion property. These merits enabled the ionogel-based sensor to be employed as strain and temperature sensor, exhibiting excellent sensing performance, such as wide strain range (0.05−250%), rapid response (100 ms), good durability, broad operating temperature window (−60−100 °C), and high-precision thermosensation (0.05 °C). More interestingly, the superior water-resistance ability of the ionogel endowed the ion-conducting gels with tremendous sensing performance in aqueous environment, performing as a wearable sensor for underwater communication and aquatic animals research.

Ionic transport and segmental dynamics in poly(ethylene oxide) based polymer electrolytes: Dependence on molecular weight of host polymer matrix

We have investigated the ion transport and segmental dynamics in poly(ethylene oxide) (PEO) and sodium tetrafluoroborate (NaBF4) salt based solid polymer electrolytes as a function of molecular weight of PEO polymer matrix at a fixed salt concentration (EO/Na = 18) using broadband dielectric spectroscopy. The molecular weight (Mv) of PEO polymer matrix was varied from 1 × 105 to 6 × 105 g/mol. The ionic conductivity of the PEO based electrolytes obtained from the complex impedance plot showed a correlation with the glass transition temperature, crystallinity and ion diffusion coefficient. The AC conductivity spectra were analyzed by using the universal power law model, except the low frequency region, where the electrode polarization contribution was dominant. The temperature dependence of ionic conductivity and the hopping frequency followed the Vogel-Tammann-Fulcher (VTF) relation, indicating a coupling between the ion transport and the segmental dynamics of polymer chains. The segmental dynamics was investigated using the derivative dielectric constant spectra. The modulus spectra were well described by the Havriliak-Nigami and the Kohlrausch-Williams-Watts functions. The temperature dependence of the conductivity relaxation time also followed the VTF relation. The ion transport in PEO based polymer electrolytes with higher molecular weight was found more cooperative than that of the other polymer electrolytes.

Versatile solid polymer electrolytes from clickable poly(glycidyl propargyl ether) for lithium metal batteries

We present three new graft copolymers for the application as solid polymer electrolytes (SPEs) in solvent-free, all solid-state lithium metal batteries (LMBs), based on the clickable poly (glycidyl propargyl ether) platform. These fully amorphous polymers consist of an all-ether polymer backbone and different additional Li+-coordinating oxo-functionalities - diester, carbonate and phosphate ester - in the attached sidechain. We aim to address the fundamental question on the influence of Li+-coordination in such doubly functionalized systems having competing Li+-coordination functional groups. We prepared polymer nanocomposite SPEs based on these novel polymers mixed with a highly-dissociating lithium salt (LiTFSI) and TiO2 nanofillers, which improve the electrolyte-electrode compatibility. We perform an extensive and comparative investigation in terms of physicochemical and electrochemical properties including ionic conductivity, lithium transference number, lithium plating and stripping as well as the fabrication and cycling of LMBs utilizing lithium iron phosphate (LFP) cathodes. Thermal characterization is coupled with temperature-dependent ionic conductivity measurements and detailed IR spectroscopy to understand the mechanistic properties and selectivity of the Li+ coordination and conduction. Two of the nanocomposite SPEs show efficient battery cycling with initial capacities of ca. 150 mAh g−1 and a capacity retention of ca. 70–80 % after 100 cycles.

Investigation of structural and conductivity properties of poly(vinyl alcohol)‐based electrospun composite polymer blend electrolyte membranes for battery applications

AbstractSolid polymer electrolyte has attracted great interest for the next generation of electrochemical devices such as batteries, but the low ionic conductivity and poor stability has retarded their commercial acceptance for energy storage devices applications. To overcome these issues, strategies to develop composite polymer electrolytes (CPEs) are drawing interest. Nanocomposite solid polymer blend electrolyte membranes based on poly (vinyl alcohol) (PVA), poly (vinyl pyrrolidone) (PVP) of various compositions that contained potassium nitrate (KNO3) as a dopant salt, and Barium Titanate (BaTiO3) as a filler were prepared with various concentrations of filler using electrospinning technique. The structural and complex formations due to interaction of various groups of the prepared composite polymer electrolyte membranes were investigated using X‐ray diffraction (XRD) and Fourier transform infra‐red (FTIR) spectral analysis. The conductivity of the PVA‐PVP‐KNO3‐BaTiO3 polymer electrolyte systems was found to vary between 3.71×10‐9 and 1.99×10‐5 S cm‐1 at 298 K with the increase in filler concentration. The maximum room temperature ionic conductivity (1.99×10‐5 S cm‐1) has been obtained for 9 wt% BaTiO3 doped polymer electrolyte system. The addition of filler also enhanced the thermal stability of the electrolyte. The temperature dependence ionic conductivity of the prepared complexed polymer electrolyte systems appears to obey Arrhenius behaviour.

An insight into lithium-ion transport in germanium-doped lithium titanate anode through NMR spectroscopy and post-carbonization for anode applications in lithium-ion battery

Adapting toward lithium titanate as a negative electrode for lithium-ion batteries led to the safest and long-lasting battery technology, especially for electric vehicle applications. However, the poor conductivity and lithium-ion diffusion of lithium titanate have to be addressed for widespread usage in next-generation E-mobility. The lithium-ion motion inside lithium titanate and germanium-doped lithium titanate was investigated through pulsed-field gradient nuclear magnetic resonance spectroscopy and temperature-dependent ionic conductivity studies. The superior charge carrier mobility of germanium enhanced the lithium-ion diffusion in lithium titanate significantly to 1.48 × 10−8 cm2 s−1 in Li4Ge0.1Ti4.9O12 at 500 °C. While germanium improves the ionic diffusion, an ex situ carbon coating was adapted over the sample for electronic conductivity enhancement. Samples with two different carbon contents (5 and 10 wt. %) were examined for electrochemical analysis. Significant improvements in battery performance were observed on carbon-coated germanium-doped lithium titanate. The carbon-coated sample gave superior initial performance (191 and 178 mAh g−1 for 10 and 5 wt. % carbon at 0.1C) than the pristine lithium titanate and preserved the exceptional capacity retention over a thousand cycles at 1C rate.

Mechanism of electrotransport in superionic conductor Sr-=SUB=-0.7-=/SUB=-La-=SUB=-0.15-=/SUB=-Lu-=SUB=-0.15-=/SUB=-F-=SUB=-2.3-=/SUB=- with the fluorite-type structure

The ionic conductivity of the superionic conductor Sr0.7La0.15Lu0.15F2.3 with the fluorite-type structure (type CaF2, sp. gr. Fm3m) had measured by the impedance spectroscopy in the temperature range 385-794 K. Bulk crystals of a three-component solid solution (lattice parameter a=5.7726(1) Angstrem) had obtained from the melt by the directed crystallization technique. Temperature dependence ionic conductivity sigmadc(T) satisfies the Arrhenius--Frenkel equation with the activation enthalpy of the electrical conductivity Delta Hsigma=0.706± 0.05 eV. The value of sigmadc is 1.5·10-5 S/cm at 500 K. Based on the analysis of electrophysical and structural studies of fluorite-type solid solutions in SrF2-LaF3 and SrF2-LuF3 systems, the microscopic model of ion transport in the Sr0.7La0.15Lu0.15F2.3 crystal was proposed. The concentration and mobility of charge carriers were calculated: nmob=7.8·1020 cm-3 and μmob=1.2·10-7 cm2/Vs at 500 K. Keywords: superionic conductors, impedance spectroscopy, single crystals, fluorides, rare earth ions, fluorite structure.

Механизм электропереноса в суперионном проводнике Sr-=SUB=-0.7-=/SUB=-La-=SUB=-0.15-=/SUB=-Lu-=SUB=-0.15-=/SUB=-F-=SUB=-2.3-=/SUB=- со структурой флюорита

The ionic conductivity of the superionic conductor Sr0.7La0.15Lu0.15F2.3 with the fluorite-type structure (type CaF2, sp. gr. Fm-3m) had measured by the impedance spectroscopy in the temperature range 385–794 K. Bulk crystals of a three-component solid solution (lattice parameter a = 5.7726(1) A) had obtained from the melt by the directed crystallization technique. Temperature dependence ionic conductivity σdc(T) satisfies the Arrhenius–Frenkel equation with the activation enthalpy of the electrical conductivity Hσ = 0.706 ± 0.05 eV. The value of σdc is 1.5 10–5 S/cm at 500 K. Based on the analysis of electrophysical and structural studies of fluorite-type solid solutions in SrF2–LaF3 and SrF2–LuF3 systems, the microscopic model of ion transport in the Sr0.7La0.15Lu0.15F2.3 crystal was proposed. The concentration and mobility of charge carriers were calculated: nmob = 7.8 × 1020 cm–3 and μmob = 1.2 × 10–7 cm2/Vs at 500K.

Molecular dynamics and conduction mechanism of poly(vinyl chloride‐co‐vinyl acetate‐co‐2‐hydroxypropyl acrylate) terpolymer containing ionic liquid

AbstractDielectric spectroscopy (DS) measurements were performed to probe the segmental dynamics and ion mobility of poly(vinyl chloride‐co‐vinyl acetate‐co‐2‐hydroxypropyl acrylate) terpolymer dopped with different amounts of tetrabutylammonium tetrafluoroborate ([TBA] [BF4]) ionic liquid (IL). Differential scanning calorimetry (DSC) was also employed to trace the change in the glass transition temperature (Tg) at different loads of IL. The DSC measurements revealed a remarkable reduction in the PVVH Tg from 344 to 310 K just by adding 20 wt% of IL. The DS measurements revealed three relaxation processes named α, β1, and β2. The α‐process is related to the segmental motion of PVVH while the β1 and β2 are due to the restricted local dynamics of side chains. The segmental relaxation times (α‐relaxation) speed up with increasing the concentration of IL due to the plasticization effect of IL on polymer chains. The temperature dependence of α‐relaxation follows the Vogel‐Fulcher‐Tammann (VFT) relation with dynamic glass transition between 323 and 294 K in agreement with the DSC measurements. The β1 and β2‐relaxations have an Arrhenius temperature dependence. The temperature dependence of ionic conductivity obeys the VFT behavior indicating the coupling between the segmental motion of PVVH chains and ion transport. Polaronic tunneling is the predominant conduction mechanism in PVVH and its composites. The specific capacitance increases with increasing both the temperature and IL concentration.

Preparation of Li-Si-P-S-O-N Glasses: The Impact of Lipon Incorporation on Ionic Conductivity

Lithium glassy solid electrolytes (GSEs) are an alternative to liquid electrolytes in the development of solid-state batteries. Mixed oxy-sulfide nitride GSEs incorporate the useful properties of sulfide glasses, which show high ionic conductivity, of oxide glasses which display excellent chemical stability, and of nitride glasses which exhibit good electrochemical stability. In our investigation of these new GSEs, the following compositional series was explored Li2S + SiS2 + [(1-x)Li0.67PO2.83 + xLiPON]. Differential scanning calorimetry (DSC) was employed to determine the crystallization and glass temperatures of these GSEs. In addition, electrochemical impedance spectroscopy (EIS) was used to determine the temperature-dependent ionic conductivity of theses GSEs. X-ray Photoelectron Spectroscopy (XPS) was conducted on the glasses to further understand the chemical bonding environment of nitrogen. It was found that x = 0.2 displayed the highest ionic conductivity suggesting that nitrogen incorporation can be used to optimize mixed oxy-sulfide glasses.Support of this research by NSF Grant NSF-DMR-1936913 is acknowledged.