Maximum Room Temperature Ionic Conductivity Research Articles

Borax cross-linked guar gum hydrogel-based self healing polymer electrolytes filled with ceramic nanofibers towards high-performance green energy storage applications

An inventive concept towards the implementation of green energy-storing devices is the synthesis of hydrogel-based gel electrolytes from biopolymers imbued with self-healing capabilities. However, these electrolytes have drawbacks, such as low mechanical stability due to inadequate cross-linking and limited ionic conductivity compared to synthetic polymers. This work develops and characterizes a flexible self-healing hydrogel polymer electrolytes (HPEs) based on guar gum (GG) hydrogel for use in energy storage devices. Hydrogel is prepared with silicon dioxide (SiO2) nanofibers dispersed into borax-bonding cross-linked guar gum. Propylene carbonate (PC) and diethyl carbonate (DC) in equal amounts and lithium perchlorate (LiClO4) are used as plasticizers and salt, respectively. It has been found that adding nanofibers to the hydrogel and spreading them there considerably increases the ionic conductivity as evaluated by ac impedance spectroscopy. When the nanofiber concentration is 5 wt% (wt%), the hydrogel electrolytes reach their maximum room temperature ionic conductivity of 4.3 × 10−3 S cm−1. XRD, FTIR, SEM, and XPS investigations are used to explain the enhanced conductivity caused by the dispersion of nanofibers. Nanofibers also improve the self-healing abilities of materials, as demonstrated by the fact that hydrogels loaded with 5 wt% nanofibers recover from deformation more quickly than hydrogels with lower nanofiber contents. Additionally, the dispersion of nanofibers enhances the hydrogel's mechanical and thermal properties. According to electrochemical investigations and linear sweep voltammetry (LSV) graphs, hydrogel electrolytes are stable up to 4.7 V. When compared to nanofiber-free hydrogels, nanofiber-integrated hydrogel electrolytes show more excellent interfacial stability. The developed self-healing hydrogel-based polymer electrolytes exhibit outstanding promise for a range of energy storage systems, opening the way for creating high-performance and environmentally friendly energy storage solutions.

Improving electrolyte performance: Nanocomposite solid polymer electrolyte films with cobalt oxide nanoparticles

AbstractThe present work gives an insight into the structural, thermal, and electrical analysis of novel nanocomposite solid polymer electrolyte films prepared using the solution casting technique by incorporating cobalt oxide nanoparticles into methyl cellulose‐magnesium acetate polymer electrolyte matrix. The impact of ceramic oxide on the complexation of the salt with the polymer chain is evident from FTIR analysis. The crystallinity of the electrolyte systems decreases upon the incorporation of nanofiller into the matrix. Electrochemical Impedance Analysis of the samples shows enhancement in the conductivity of the electrolytes. Nanocomposite electrolyte systems with 2 wt% (5.93 × 10−4 S/cm) and 3 wt% (5.77 × 10−4 S/cm) of cobalt oxide exhibit maximum room temperature ionic conductivity compared to other electrolyte systems. DSC thermogram reveals the creation of free volume in the matrix with the incorporation of the filler. A primary battery is fabricated using the nanocomposite electrolyte system with 3 wt% of the nanofiller, and its open circuit potential and discharge characteristics have been analyzed.Highlights Novel nanocomposite SPEs with cobalt oxide were prepared via solution casting. FTIR and XRD studies revealed modification in the microstructure. Cobalt oxide incorporation enhanced ionic conductivity of SPE. A primary battery fabricated using the highest conducting SPE.

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 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

Structural, thermal, and electrochemical studies of biodegradable gel polymer electrolyte for electric double layer capacitor

A quasi-solid-state supercapacitor is fabricated using a biodegradable gel polymer electrolyte (GPE), and graphene nano-platelets (GNPs) capacitive electrodes. The GPE film comprises biodegradable polymer cellulose acetate (CA), ionic liquid, 1-ethyl-3-methylimidazolium thiocyanate (EMImSCN) and dopant salt potassium thiocyanate (KSCN). The polymeric gel films are prepared using the standard “solution cast technique” and characterized by using X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Thermogravemetric analysis (TGA), Impedance spectroscopy, and Linear sweep voltammetry techniques. The synthesized GPE exhibits maximum room temperature ionic conductivity ∼1.2 x 10−3 S cm−1 and an electrochemical stability window of ∼2.4 V. The electrical double layer capacitor (EDLC) is configured by sandwiching the GPE film between two graphene nanoplatelets (GNPs) electrodes. The performance of the EDLC cell is evaluated in terms of specific capacitance, rate, and pulse power by using cyclic voltammetry, and electrochemical impedance measurement techniques.

Electrical, electrochemical and structural studies of a chlorine-derived ionic liquid-based polymer gel electrolyte.

In the present article, an ionic liquid-based polymer gel electrolyte was synthesized by using poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) as a host polymer. The electrolyte films were synthesized by using the solution casting technique. The as-prepared films were free-standing and transparent with good dimensional stability. Optimized electrolyte films exhibit a maximum room-temperature ionic conductivity of σ = 8.9 × 10−3 S·cm−1. The temperature dependence of the prepared polymer gel electrolytes follows the thermally activated behavior of the Vogel–Tammann–Fulcher equation. The total ionic transference number was ≈0.91 with a wider electrochemical potential window of 4.0 V for the prepared electrolyte film which contains 30 wt % of the ionic liquid. The optimized films have good potential to be used as electrolyte materials for energy storage applications.

Li+ and Oxidant Addition To Control Ionic and Electronic Conduction in Ionic Liquid-Functionalized Conjugated Polymers

Conduction of ions and charge (electrons) often follow distinct materials design rules, presenting a significant challenge for the development of homogeneous materials that are good at both. The fundamental interactions that dictate ionic and electronic conduction in mixed conductors are still unclear. Here, we characterize the ionic and electronic conduction of a class of mixed polymeric conductors in which ionic liquid groups are tethered to an electron-conducting conjugated polymer backbone. A model conjugated polymeric ionic liquid, poly{3-[6′-(N-methylimidazolium)hexyl]thiophene}BF4– (P3HT-IM), is synthesized and shown to have significant long-range ordering. Chemical oxidation of the polymer results in a room-temperature electronic conductivity of 10–2 S cm–1. The polymer is also capable of dissolving Li+ salt up to a concentration of rsalt = 1 [moles of salt]/[moles of monomer]. The polymer displays a monotonic increase in ionic conductivity with salt concentration, reaching a maximum room-temperature ionic conductivity of 10–5 S cm–1 at the highest concentration of rsalt = 1. Notably, this is among the first studies to characterize both ionic conductivity and electronic conductivity of an ionic liquid-functionalized conjugated polymer upon the addition of an oxidant and salt. All-atom molecular dynamics (MD) simulations indicate that the imidazolium side chains promote the formation of a percolated network of solvation sites at high salt concentrations, which facilitates ion transport. Pulsed-field gradient nuclear magnetic resonance diffusivity measurements and MD indicate a lithium transference number around 0.5, suggesting that the percolated solvation network promotes lithium transport in a way that is unique from many ion-conducting systems. These results suggest that the addition of diffuse, ionic liquid-like groups to a conjugated polymer backbone serves as an effective design approach to facilitate simultaneous lithium-ion conduction and electronic conduction in the absence of a solvent.

Structural, electrical and electrochemical studies of ionic liquid-based polymer gel electrolyte using magnesium salt for supercapacitor application

In the present studies, the effect of ionic liquid 1-Ethyl-2,3-dimethylimidazoliumtetrafluoroborate (EDiMIM)(BF4) on ionic conductivity of gel polymer electrolyte using poly(vinylidene fluoride-co-hexafluoropropylene) [PVdF(HFP)] and magnesium perchlorate [Mg(ClO4)2] as salt was investigated. The maximum room temperature ionic conductivity for the optimized system was found to be of the order of 8.4 × 10–3 S cm−1. The optimized composition reflects Vogel-Tammann-Fulcher (VTF) behavior in the temperature range of 25 °C to 100 °C. The X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy studies confirm the uniform blending of ionic liquid, polymer, and salts along with the enhanced amorphous nature of the optimized system. Dielectric and modulus spectra studies provide the information of electrode polarization as well as dipole relaxation properties of polymeric materials. The optimized electrolyte system possesses a sufficiently large electrochemical window of the order of 6.0 V with stainless steel electrodes.

Properties of Gel Polymer Electrolyte Based Poly(Vinylidine Fluoride-сo-Hexafluoropropylene) (PVdF-HFP), Lithium Perchlorate (LiClO<sub>4</sub>) and 1-Butyl-3-Methylimmidazoliumhexafluorophosphate [PF<sub>6</sub>

This study reported the preparation and characterization of gel polymer electrolyte (GPE) using poly (vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP), lithium perchlorate (LiClO4) and 1-butyl-3-metilimmidazoliumhexafluorophosphate [PF6]. The GPE were prepared by solution casting technique. [Bmim] [PF6] ionic liquid is used as an additive for the purpose of increasing the ionic conductivity of GPE. Morphological analysis showed that the electrolyte gel polymer sample had a smooth and flat surface with the addition of [Bmim] [PF6] and no phase separation effect was observed. This shows the compatibility between PVdF-HFP and [Bmim] [PF6]. ATR-FTIR analysis showed that C-F bond related peaks experienced peak changes in terms of intensity and peak shifting. This proves the interaction of the imidazolium ion with the fluorine atom through the formation of coordinate bonds. Ionic conductivity analysis showed that PVdF-HFP-[Bmim][PF6] samples reached a maximum room temperature ionic conductivity value of 2.44 × 10-4 S cm-1 at 60 wt.% [Bmim] [PF6]. When 20 wt.% of LiClO4 added to the system, the ionic conductivity increased one magnitude order to 2.20 × 10-3 S cm-1.

Studies on ionic liquid based nanocomposite gel polymer electrolyte and its application in sodium battery

A nanocomposite gel polymer electrolyte system comprising porous membrane of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/TiO2 immobilizing a liquid electrolyte of sodium trifluoromethanesulfonate (NaCF3SO3) in 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMImCF3SO3) ionic liquid is reported in the paper. The porous gel polymer electrolyte membranes are prepared by phase-inversion technique. The electrolyte membranes are characterized by various physical and electrochemical techniques. The TiO2 nanoparticles display interaction with the anion (CF3SO3−) of the liquid electrolyte and enhance amorphicity in the polymer network. The optimized membrane displays maximum room temperature ionic conductivity as ~0.4 mS cm−1 with improved electrochemical stability window of ~4.3 V and Na+ ion transport number as ~0.27. A proto-type sodium battery using the optimized membrane is fabricated and characterized. The battery delivers a stable open circuit potential of ~2.2 V and shows a discharge capacity ~200 mA h g−1 at 25 mA g−1 drain current.

Structural and electrochemical studies of bromide derived ionic liquid-based gel polymer electrolyte for energy storage application

In the present studies, poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), ionic liquid {1-Ethyl-3-methylimidazolium bromide} (EMIM)(Br), and magnesium perchlorate Mg(ClO4)2 as salt were used to synthesize free standing electrolyte films by using solution cast technique. The prepared electrolyte films were investigated by using various structural and electrochemical techniques like scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) as well as ionic and temperature dependence studies. It has been observed that addition of ionic liquid significantly increases the properties like ionic conductivity, thermal stability, transparency etc. The maximum room temperature ionic conductivity for the optimized system was found to be of the order of 2.05 × 10−2 S cm−1 which is suitable for device fabrication point of view. The optimized electrolyte films are suitable for supercapacitor application.

Sodium ion conducting nanocomposite polymer electrolyte membrane for sodium ion batteries

The paper reports effect of dispersion of titanium dioxide (TiO2) nanofiller on the sodium ion conducting nanocomposite polymer electrolyte membranes consisting of TiO2 dispersed membranes of poly(vinylidenedifluoride-co-hexafluoropropylene) (PVdF-HFP) soaked in a liquid electrolyte of sodium hexafluorophosphate (NaPF6) in ethylene carbonate (EC) and propylene carbonate (PC). The TiO2 dispersed membranes have been prepared by phase inversion technique. The structural and morphological properties of the polymer electrolyte membranes have been investigated using x-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The membranes have been found to be highly porous with maximum porosity ~ 72% and liquid electrolyte uptake ~ 270%. Ionic conductivity of the electrolyte membranes containing different concentrations of TiO2 has been measured by complex impedance spectroscopy. The maximum room temperature ionic conductivity has been found to be ~ 1.3 × 10−3 S cm−1. The ionic conductivity measured with temperature has been found to follow VTF behavior. The ion transport numbers of the membranes have been studied using dc polarization, complex impedance, and cyclic voltammetry. The membranes have been found to be predominantly ionically conducting with Na+ transport number ~ 0.31. The electrochemical stability window of the membranes has also been measured using cyclic voltammetry and found to be 3.5 V.

PVC/PEMA‐based blended nanocomposite gel polymer electrolytes plasticized with room temperature ionic liquid and dispersed with nano‐ZrO2 for zinc ion batteries

Nanocomposite gel polymer electrolytes (NCGPEs) comprising of the solution of zinc trifluoromethanesulfonate [Zn(OTf)2] in 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) ionic liquid entrapped in poly(vinyl chloride)/poly(ethyl methacrylate) blend and dispersed with zirconia (ZrO2) nanofiller has been prepared via simple solution casting method. The free standing film of the composite gel polymer electrolyte system exhibited the maximum room temperature ionic conductivity of 3.63 × 10−4 Scm−1 at 3 wt% nanofiller concentration with the accomplishment of highest zinc ion transference number of 0.66. The interaction and complexation among various constituents of the resultant NCGPEs has been confirmed from X‐ray diffraction (XRD) and Attenuated total reflection‐Fourier transform infrared (ATR‐FTIR) spectroscopic studies. Differential scanning calorimetry (DSC) and thermogravimetric (TG) analyses further corroborates the improved thermal behavior of ZrO2 added gel polymer electrolytes as compared with that of filler‐free gel electrolytes. The porous morphology of the thin films was observed by scanning electron microscopy (SEM) whereas the electrochemical properties of the NCGPEs were studied utilizing linear sweep voltammetry (LSV) and cyclic voltammetry (CV). POLYM. COMPOS., 40:3402–3411, 2019. © 2019 Society of Plastics Engineers

Ion transport studies in nanocomposite polymer electrolyte membrane of PVA–[C4C1Im][HSO4]–SiO2

The paper reports the effect of SiO2 nano-filler on structural, thermal, and ion transport properties of polymer electrolyte system comprising polyvinyl alcohol (PVA) and 1-butyl-3-methylimidazolium hydrogen sulfate [C4C1Im][HSO4] ionic liquid. The addition of SiO2 nano-filler results into enhancement in amorphicity and thermal stability and lowering of glass transition temperature of the membranes. A detailed investigation of possible interactions among the constituents PVA, [C4C1Im][HSO4] and SiO2, and cation–anion and anion–anion pairs of [C4C1Im][HSO4] in the polymer electrolyte and their dissociation due to SiO2 filler has been carried out in the membranes using Fourier transform infra-red (FTIR) and Raman spectroscopy. The membranes show maximum room temperature ionic conductivity as 9.9 × 10−3 S cm−1 for 6 wt.% of the nano-filler which is about four times higher than the membrane without nano-filler and an order higher than pure [C4C1Im][HSO4]. With temperature, the ionic conductivity shows VTF behavior in the temperature range 40–120 °C. On the basis of FTIR and ion transport results, a model for ion transport in the membranes is proposed.

Experimental investigation of nano filler TiO2 doped composite polymerelectrolytes for lithium ion batteries

A composite polymer electrolyte system based on PEMA/PVAc/LiClO4/EC with different wt% of nano filler TiO2 was prepared by solution casting technique.The structural investigations of the prepared polymer electrolyte membranes were carried out using X-ray diffraction and Fourier Transform infrared spectroscopictechniques. The electrical measurements were performed at various temperatures 303–363 K using ac impedance technique. The maximum room temperature ionic conductivity of 2.745 × 10−3 S/cm was obtained for the polymer electrolyte membrane with 10 wt% TiO2. The temperature dependent ionic conductivity plot exhibited VTF behaviour. The porous nature of the membranes was verified from the SEM and AFM images. The thermal investigations performed on the samples by DSC technique displayed prominent endothermic peaks which revealed that the samples with the incorporation of filler had undergone a transition tothe amorphous phase at lower temperatures. The thermal stability of the film (F3) of maximum ionicconductivity was found to be 260 °C by means of TG/DTA analysis. The wide electrochemical stability window of –2.1 V to +2.1 V and the cyclability & reversibility of the maximum ion conducting sample at ambient temperature were confirmed by carrying out the electrochemical characterizations such as linear sweep voltammetry and cyclic voltammetry respectively.

Effect of Al2O3 nanofiller on the electrical, thermal and structural properties of PEO:PPG based nanocomposite polymer electrolyte

A new series of nanocomposite polymer electrolyte (NCPE) system comprising of polyethylene oxide (PEO) and polypropylene glycol (PPG) as blended polymer host, zinc trifluoromethanesulfonate [Zn(CF3SO3)2] as dopant salt and nanocrystalline alumina [Al2O3] as filler was prepared by solution casting technique. The present system consisting of five different compositions of 87.5 wt% (PEO:PPG)–12.5 wt% Zn(CF3SO3)2 + x wt% Al2O3 [where x = 1, 3, 5, 7 and 9, respectively] has been thoroughly characterized by various analytical techniques such as electrical impedance spectroscopy, X-ray diffraction (XRD) studies, differential scanning calorimetry (DSC), scanning electron microscopic (SEM) analysis and linear sweep voltammetry (LSV). The maximum room temperature ionic conductivity exhibited by the NCPE was found to be 2.1 × 10−4 S cm−1 for 3 wt% loading of Al2O3 which is an order higher than that of the optimized filler-free zinc salt doped polymer electrolyte system at 298 K. The evidence of a decrease in the degree of crystallinity responsible for the enhanced conductivity was revealed by the XRD data and further confirmed by DSC and SEM results. Moreover, the electrochemical stability window of the highly conducting electrolyte matrix has been experimentally determined by linear sweep voltammetry and found to be 3.6 V which is fairly adequate for the construction of zinc primary batteries as well as zinc-based rechargeable batteries at ambient conditions.

Playing with ionic liquids to uncover novel polymer electrolytes

Solid polymer electrolytes (SPEs) based on chitosan and fourteen ionic liquids (ILs) were synthesized by solvent casting method. All ILs had in common a 1-ethyl-3-methylimidazolium cation ([C2mim]+). Therefore, this study focuses on the influence of the anion on the thermal, morphological, and electrochemical properties of the SPEs. The samples were analyzed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), complex impedance spectroscopy (ionic conductivity) and cyclic voltammetry. The SPEs displayed an amorphous morphology, a thermal stability higher than the one obtained for the pure chitosan matrix (>140°C), a maximum room temperature (T=25°C) ionic conductivity of 1.61×10−3Scm−1 and a wide electrochemical window of ~4.0V.

Electrical characterization of nano-composite polymer gel electrolytes containing NH4BF4 and SiO2: role of donor number of solvent and fumed silica

Nano-composite polymer gel electrolytes were synthesized by using polyethylene oxide (PEO), ammonium tetrafluoroborate (NH4BF4), fumed silica (SiO2), dimethylacetamide (DMA), ethylene carbonate (EC), and propylene carbonate (PC) and characterized by conductivity studies. The effect of donor number of solvent on ionic conductivity of polymer gel electrolytes has been studied. The mechanical strength of the gel electrolytes has been increased with the addition of nano-sized fumed silica along with an enhancement in conductivity. Maximum room temperature ionic conductivity of 2.63 × 10−3 and 2.92 × 10−3 S/cm has been observed for nano-composite gel electrolytes containing 0.1 and 0.5 wt% SiO2 in DMA+1 M NH4BF4+10 wt% PEO, respectively. Nano-composite polymer gel electrolytes having DMA have been found to be thermally and electrically stable over 0 to 90 °C temperature range. Also, the change in conductivity with the passage of time is very small, which may be desirable to make applicable for various smart devices.

All-Solid State Na-Ion Batteries Na2-2dFe2-D(SO4)3|Na3-XMxP1-XS4 (M=Ge4+,Ti4+, Sn4+) (x=0,0.1) | Na2Ti3O7

Sodium ion batteries attracted large research community because of earth-abundance and low cost of sodium. Though significant advances have been made in the development of Na-ion cathodes and anodes, a major impediment to the commercial viability of rechargeable Na-ion batteries is the lack of an effective electrolyte. Current Na-ion electrolytes are mostly based on the same fundamental chemistry as Li-ion electrolytes – a mixture of cyclic and linear organic carbonates with a Na-salt. Such organic solvent-based liquid electrolytes are flammable and have limited electrochemical windows. A promising alternative architecture is all-solid-state Na-ion rechargeable batteries utilizing non-flammable ceramic Na superionic conductor electrolytes. Na solid electrolytes such as -alumina and NAtrium Superionic CONductors (NASICON) are well-studied, but they typically exhibit reasonable ionic conductivities only at higher temperatures. Here we report the synthesis, characterization of materials that from our parallel computational studies appeared to be promising components of all-solid state rechargeable Na-ion batteries with high rate capabilities. Recently it is reported that the cubic phase of Na3PS4 (c-Na3PS4, space group: I4-3m) is a promising solid electrolyte with a room temperature Na+ ion conductivity of 0.2mS/cm. In order to increase the ionic conductivity further we prepared Na3-xMxP1-xS4 (M=Ge4+,Ti4+, Sn4+) (x=0,0.1) using mechanical milling followed by annealing at 250°C. Maximum room temperature ionic conductivity of 0.25mS/cm was observed for Sn doped NaP3S4. In situ high temperature XRD showed that all the compounds are stable up to 400°C.When it comes to identifying cathode materials for such a NIB , a considerable fraction of research activity still focuses materials analogous to those that work well in Li-ion batteries containing costly transition metals such as Co, which appears problematic for various reasons: differences in reaction mechanisms of the Na analogues to the Li transition metal oxides, different structural requirements for Na+ mobility, the fact that a cost advantage of Na over Li will only translate into low cost batteries. Hence, research on transition metal electrode materials for Na-ion batteries will have to concentrate on abundant transition metals (essentially Fe, Ti, Mn, and possibly Cr, V). On the other hand, O3- NaFeO2, and P2-type Nax[Fe0.5Mn0.5]O2 utilizing the Fe4+/Fe3+ redox couple are known to suffer from limited reversible capacity and low operating potential. Here we report the preparation of Na2+2dFe2-d(SO4)3 by mechanical milling of Na2SO4 and FeSO4 followed by annealing at 400ºC in an argon environment. The Na2-2dFe2-d(SO4)3 formed an alluaudite-type structure in space group C2/c with lattice constants a=12.654(1)Å, b=12.761(9)Å, c=6.503(5)Å, β=115.52(1)º close those previously reported for d =0.12.For anode transition metal oxides the number of low potential lithium insertion compounds is rather limited owing to the competition of insertion vs conversion reactions, the former being only favored for early 3d metal (Ti, V) oxides. Along that line, NaxVO2 was recently found to reversibly react with Na at ca. 1.5 V but sensibly lower operation voltages would be needed for enhanced energy density. Titanium-based systems are considered as best alternatives. Hence, Na2Ti3O7 was prepared from anatase TiO2 and anhydrous Na2CO3 mixtures with 10% excess of the latter with respect to stoichiometric amounts. These mixtures were milled and treated at 800ºC for 20 h with intermediate regrinding. X-ray diffraction pattern indicated the formation of pure crystalline phase as shown in the figure with space group P121/m.Based on the synthesized and characterized materials we assembled all-solid state sodium-ion batteries combining the alluaudite-type cathode with Na3PS4 as the solid electrolyte and Na2Ti3O7 as the anode. Favourable rate performance of the all solid state sodium-ion battery was demonstrated at room temperature. Figure 1

Effects of Nano Alumina and Plasticizers on Morphology, Ionic Conductivity, Thermal and Mechanical Properties of PEO-LiCF3SO3 Solid Polymer Electrolyte

In this contribution, a solid polymer electrolyte (SPE) was prepared by a ball milling method followed by a hot pressing process. The SPE used poly(ethylene oxide) (PEO) doped with trifluoromethanesulfonate (LiCF3SO3) as a host matrix. Nano alumina (Al2O3) was used as filler, and dioxyphthalate (DOP) and polyethylene glycol (PEG) applied as plasticizers. Various concentrations of lithium salts, nano alumina and plasticizers (5, 10, 15 and 20wt%) were studied. The morphology, ionic conductivity, thermal and mechanical properties of the SPE were also examined. The ionic conductivity increased from 10−7 to 10−6Scm−1 upon the addition of lithium salt. The PEO-15wt% (LiCF3SO3) solid polymer electrolyte exhibited maximum room temperature ionic conductivity. Significantly, the addition of nano alumina and plasticizers into PEO-LiCF3SO3 SPE enhanced the ionic conductivity to 10−5 and 10−4Scm−1, respectively. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies indicated that the conductivity increase was due to the decrease of crystallinity upon the addition of lithium salt, nano alumina and plasticizers into the SPE system. The mechanical properties of PEO tended to decrease with the addition of lithium salts, nano alumina and plasticizers. Nevertheless, durable film with high flexibility could be formed with a potential use as an efficient electrolyte in lithium and other rechargeable batteries.