A novel gel electrolyte with lithium difluoro(oxalato)borate salt and Sb2O3 nanoparticles for lithium ion batteries

A new type of lithium difluoro(oxalate)borate salt was synthesized by solid state reaction method and has been incorporated into polyvinyledenefluoride–hexafluoropropylene (PVdF–HFP) skeleton. Ethylene carbonate (EC) and diethyl carbonate (DEC) mixture was used as plasticizing agent. Sb₂O₃ nanoparticle was used as the filler in the polymer host to prepare the nanocomposite polymer electrolytes (NCPE) for lithium ion batteries by solution casting technique. All the membranes were subjected to a.c. impedance, mechanical stability and morphological analysis. Among them 5 wt% Sb₂O₃ having NCPE exhibited enhanced conductivity of 0.298 mS cm⁻¹ at ambient temperature and Young's modulus increased from 1.32 to 2.31 MPa after the addition of Sb₂O_3. The conductivity enhancement is explained in terms of Vogel–Tamman–Fulcher (VTF) theory.     

Effect of lithium iodide addition on poly(ethylene oxide)-poly(vinylidene fluoride) polymer-blend electrolyte for dye-sensitized nanocrystalline solar cell

The effect of lithium iodide concentration on the conduction behavior of poly(ethylene oxide)-poly(vinylidene fluoride) (PEO-PVDF) polymer-blend electrolyte and the corresponding performance of the dye-sensitized solar cell (DSSC) were studied. The conduction behavior of these electrolytes was investigated with varying LiI concentration (10-60 wt % in polymer blend) by impedance spectroscopy. A "polymer-in-salt" like conduction behavior has been observed in the high salt concentration region. The transition from "salt-in-polymer" to "polymer-in-salt" conduction behavior happened at the salt content of 23.4 wt %, which is much lower than 50 wt % as generally reported. The electrolyte shows the highest ionic conductivity (approximately 10(-3) S cm(-1)) at the salt concentration above 23.4 wt %. From the evaluation of salt effect on the performances of corresponding DSSC, we find that increasing LiI concentration leads to increased short-circuit photocurrent density (Jsc) caused by enhanced I3(-) diffusion up to an LiI content of 28.9 wt %. Above this limitation, the Jsc decreases as a result of increased charge recombination caused by the further increased I3(-) concentration. The open-circuit voltage (Voc) increases gradually with LiI concentration owing to the enhanced I(-) content in DSSC. The optimized conversion efficiency is obtained at a salt content of 28.9 wt % in the "polymer-in-salt" region, with high ionic conductivity (1.06 x 10(-3) S cm(-1)). Based on these facts, we suggest that the changes of conduction behavior and the changes of I3(-) and I(-) concentrations in the electrolytes contribute to the final performance variation of the corresponding DSSC with varying LiI concentration.     

Quasi-solid-state dye-sensitized solar cells assembled with polymeric ionic liquid and poly(3,4-ethylenedioxythiophene) counter electrode

Poly(3,4-ethylenedioxythiophene) nanofibers (PEDOT-NF) with high catalytic activity were synthesized and employed as a counter electrode in dye-sensitized solar cells (DSSCs). A polymeric ionic liquid (PIL) was used as a gelling agent and an iodide source for making a highly conductive gel polymer electrolyte. A quasi-solid-state DSSC assembled with this PIL-based gel polymer electrolyte and PEDOT-NF counter electrode exhibited high conversion efficiency of 8.12% at 100 mW cm^− 2.     

A new promising high temperature lithium battery solid electrolyte

Lithium lanthanoid silicates find importance as a solid electrolyte in high temperature lithium batteries in view of its high ionic conductivity at high temperatures. An first ever attempt is made to synthesis a new high temperature solid electrolyte viz., lithium samarium holmium silicate by sol–gel process and it has been characterized by thermal analysis (TGA–DTA), X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Lithium ion conductivity of 0.8087 × 10⁻⁷ Ω⁻¹ cm⁻¹ at 25 °C was obtained and it increases with increasing temperature. For the first time a highest conductivity of 0.1095 × 10⁻² Ω⁻¹ cm⁻¹ was obtained at 850 °C which is high compared to other high temperature lithium battery solid electrolytes.     

Plastic–polymer composite electrolytes: Novel soft matter electrolytes for rechargeable lithium batteries

We present here a soft matter solid composite electrolyte obtained by inclusion of a polymer in a semi-solid organic plastic lithium salt electrolyte. Compared to lithium bis-trifluoromethanesulfonimide-succinonitrile (LiTFSI-SN), the (100 − x)%-[LiTFSI-SN]: x%-P (P: polyacrylonitrile (PAN), polyethylene oxide (PEO), polyethylene glycol dimethyl ether (PEG)) composites possess higher ambient temperature ionic conductivity, higher mechanical strength and wider electrochemical window. At 25 °C, ionic conductivity of 95%-[0.4 M LiTFSI-SN]: 5%-PAN was 1.3 × 10⁻³ Ω⁻¹ cm⁻¹ which was twice that of LiTFSI-SN. The Young’s modulus (Y) increased from Y → 0 for LiTFSI-SN to a maximum ∼1.0 MPa for (100 − x)%-[0.4 M LiTFSI-SN]: x%-PAN samples. The electrochemical voltage window for composites was approximately 5 V (Li/Li⁺). Excellent galvanostatic charge/discharge cycling performance was obtained with composite electrolytes in Li|LiFePO₄ cells without any separator.     

Organic/inorganic nanocomposite polymer electrolyte

The organic/inorganic nanocomposites polymer electrolytes were designed and synthesized. The organic/inorganic nanocom-posites membrane materials and their lithium salt complexes have been found thermally stable below 200℃. The conductivity of the organic/inorganic nanocomposites polymer electrolytes prepared at room temperature was at magnitude range of 10-6 S/cm.     

A BET model of the thermodynamics of aqueous multicomponent solutions at extreme concentration

The statistical mechanical basis of the use of Brunauer-Emmett-Teller isotherms to represent activities and other thermodynamic properties in extremely concentrated solutions was established by Ally and Braunstein (J. Chem. Thermodynamics1998, 30, 49–58) for a two-salt, single-solvent, mixture. Based upon the work of these authors, we have derived equations for solute and solvent activities in liquid mixtures containing a single solvent and indefinite number of solutes. New terms have been added to the model equations to express the effects of ternary ion interactions on the salt adsorption parameters. Solution composition is defined on the basis of salts, rather than ions, as components. As examples, the model is used to represent water activities in concentrated (lithium nitrate  +  potassium nitrate  +  water) and (lithium ion  +  sodium ion  +  chloride ion  +  nitrate ion  +  water) mixtures, and salt solubilities in (calcium chloride  +  calcium nitrate  +  water) mixtures.     

Photoinduced free radical polymerization of thermoset lithium battery electrolytes

Series of solid poly(ethylene oxide)-methacrylate electrolytes have successfully been manufactured with an aim to serve in a multifunctional battery both as mechanical load carrier as well as lithium ion conductor. The electrolytes produced, in a solvent free process with no post cure swelling, hold a broad range of both mechanical as well as ion conducting properties. The monomer and Li-salt mixtures have been irradiated with UV light, initiating free radical polymerization to obtain solid smooth, homogenous specimens to be utilized as ion conducting electrolytes. The storage modulus at 20 °C is ranging from 1 MPa to almost 2 GPa. The conducting ability of the electrolyte ranges from 5.8 × 10^?10 up to 1.5 × 10^?6 S/cm. These large variations in both mechanical properties as well as ionic conductivity are discussed, but also the versatility within the production technique is emphasized.     

A novel sandwiched membrane as polymer electrolyte for lithium ion battery

A novel kind of sandwiched polymer membrane was prepared by coating three layers of poly(vinyl difluoride) (PVDF), poly(methyl methacrylate) (PMMA) and PVDF, separately. Its characteristics were investigated by scanning electron microscopy, FT-IR, X-ray diffraction, and differential thermal analysis. It consists of two phases. The outer PVDF layers are porous, and the inner PMMA layer is solid. Since the PMMA has a good compatibility with the carbonate-based liquid electrolyte, the membrane can easily absorb the electrolyte to form a gelled polymer electrolyte (GPE). As a result, the evaporation peak of the liquid electrolyte is increased to 160 °C. Due to very low evaporation of the liquid electrolyte, LiCoO₂ shows good cycling behavior in the range of 4.4–3.0 V when this GPE is used as the separator and polymer electrolyte, and lithium as the counter and reference electrode. This unique sandwiched membrane is promising for application in scale-up lithium ion batteries with high safety and high energy density.     

Structural modifications of swift heavy ion irradiated PEN probed by optical and thermal measurements

The effects of swift heavy ion irradiation on the structural characteristics of Polyethylene naphthalate (PEN) were studied. Samples were irradiated in vacuum at room temperature by lithium (50 MeV), carbon (85 MeV), nickel (120 MeV) and silver (120 MeV) ions with the fluence in the range of 1×10¹¹–3×10¹²  ions cm⁻². Ion induced changes were analyzed using X-ray diffraction (XRD), Fourier transform infra red (FT-IR), UV–visible spectroscopy, thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Cross-linking was observed at lower doses resulting in modification of structural properties, however higher doses lead to the degradation of the investigated polymeric samples.     

Vapour pressure osmometry determination of water activity of binary and ternary aqueous (polymer + polymer) solutions

Precise water activity measurements at T = 308.15 K were carried out on several binary (water + polymer) and ternary {water + polymer (1) + polymer (2)} systems using the vapour pressure osmometry (VPO) technique. Polymers were polyethylene glycol 400 (PEG400), polyethylene glycol 6000 (PEG6000), polypropylene glycol 400 (PPG400), polyvinylpyrrolidone (PVP) and dextran (DEX). The water activity results obtained were used to calculate the vapour pressure of solutions as a function of concentration and the segment-based local composition models, NRTL and Wilson, were used to correlate the experimental water activity values. It was found that, for the polymer concentration range studied here, the values of the water activity obtained for the binary (water + polymer) solutions decrease in the order DEX > PVP > PEG6000 > PPG400 > PEG400. Furthermore, water activities of solutions of each polymer in the aqueous solutions of (5, 10, 15 and 20)% (w/w) other polymers investigated were also measured at T = 308.15 K. The ability of polymer (1) in decreasing the water activity of binary {water + polymer (2)} solutions was discussed on the basis of the (polymer + water) and {polymer (1) + polymer (2)} interactions.     

A dual–ion battery using diamino–rubicene as anion–inserting positive electrode material

A novel and non-polymeric anion-inserting electrode material has been designed and prepared for promoting research on molecular ion rechargeable batteries: 5,12-diaminorubicene (DARb). The apolar core structure of a rubicene molecule has been coupled to two amino-groups for producing an original conjugated primary diamine exhibiting low affinity for polar solvents such as common carbonate-based battery electrolytes. The electrochemical reactivity of this organic molecule has been probed in a dual-ion cell configuration (vs. Li) using six different electrolyte formulations in terms of solvent (PC, EC-DMC) and lithium salt (LiPF₆, LiClO₄, LiTFSI). This diamino-rubicene material systematically showed a reversible electroactivity and promising performances when using 1 M LiPF₆ in EC:DMC (1:1 vol.%) as the electrolyte, such as an average potential of ~ 3.4 V vs. Li⁺/Li⁰, an initial capacity of 115 mAh·g^− 1 and a good capacity retention over 60 cycles without any optimization.     

(Surfactant + polymer) interaction parameter studied by (liquid + liquid) equilibrium data of quaternary aqueous solution containing surfactant,polymer, and salt

(Liquid + liquid) equilibrium (LLE) data of quaternary aqueous system containing polyoxyethylene (20) cetyl ether (with abbreviation name Brij 58, non-ionic surfactant), diammonium hydrogen phosphate, and poly ethylene glycol (PEG) with three molar masses {M_W = (1000, 6000, and 35,000) g · mol^?1} have been determined experimentally at T = 313.15 K.Furthermore, the Flory–Huggins theory with two electrostatic terms (Debye–Hückel and Pitzer–Debye–Hückel equations) have been used to calculate the phase behavior of the quaternary systems and (surfactant + polymer) interaction parameter as well as interaction parameters between other species. Temperature dependency of the parameters of the Flory–Huggins theory has been obtained.Also an effort have been done to show that addition of PEG as well as increasing the temperature can shift the binodal curves of the ternary aqueous system containing surfactant and salt to lower mole fraction of salt. Also the effect of polymer molar mass on the binodal diagram displacement has been discussed.     

New lithium ion conducting polymer electrolytes based on polysiloxane grafted with Si-tripodand centers

New kind of polymer host for lithium cations has been synthesized by catalyzed hydrosilylation reaction involving hydrogen atoms of a polysiloxane and double bonds of vinyl tris-2-methoxyethoxy silane. The obtained macromolecule can be regarded as siloxane backbone grafted with silicon tripodand elements with very short polyether chains. A family of Li ion conducting polymer electrolyte membranes have been prepared by dissolving LiPF₆ in thus obtained polymer matrix. Exceptionally high room temperature specific conductivities, exceeding 10⁻³ S/cm at 25 °C, have been measured for the studied polymer electrolytes. It is proposed that polyether chains tend to self-assembly in the presence of Li cations and this highly organized arrangement of Li coordination sites creates pathways of high lithium conductivity along the polysiloxane backbones. In addition to that, strong shielding of Li-cations suppresses the formation of ion pairs, thus increasing the charge carrier concentration. The electrolytes can be easily formed into dimensionally stable, flexible membranes.     

A lotus root-like porous nanocomposite polymer electrolyte

A lotus root-like porous nanocomposite polymer electrolyte (NCPE) based on poly(vinylidene difluoride-co-hexafluoropropylene) [P(VDF-HFP)] copolymer and TiO₂ nanoparticles was easily prepared by a non-solvent induced phase separation (NIPS) process. The formation mechanism of the lotus root-like porous structure is explained by a qualitative ternary phase diagram. The resulting NCPE had a high ionic conductivity up to 1.21 × 10⁻³ S cm⁻¹ at room temperature, and exhibited a high electrochemical stability potential of 5.52 V (vs. Li/Li⁺), lithium ion transference number of 0.65 and 22.89 kJ mol⁻¹ for the apparent activation energy for transportation of ions. It is of great potential application in polymer lithium ion batteries.     

Laser Raman and ac impedance spectroscopic studies of PVA: NH4NO3 polymer electrolyte

Ion conducting polymer electrolyte PVA:NH₄NO₃ has been prepared by solution casting technique and characterized using XRD, Raman and ac impedance spectroscopic analyses. The amorphous nature of the polymer films has been confirmed by XRD and Raman spectroscopy. An insight into the deconvoluted Raman peaks of υ₁ vibration of NO₃^? anion for the polymer electrolyte reveals the dominancy of ion aggregates at higher NH₄NO₃ concentration. From the ac impedance studies, the highest ion conductivity at 303 K has been found to be 7.5 × 10^?3 S cm^?1 for 80PVA:20NH₄NO₃. The conductivity of the polymer electrolytes has been found to depend on the degree of dissociation of the salt in the host polymer matrix. The combination of the above-mentioned analyses has proven worth while and in fact necessary in order to achieve better understanding of these complex systems.     

Li2SO4-polyacrylamide polymer electrolytes for 2.0 V solid symmetric supercapacitors

A neutral polymer electrolyte comprised of lithium sulfate (Li₂SO₄) and polyacrylamide (PAM) was developed. The Li₂SO₄-PAM electrolyte film shows an ionic conductivity up to 10 mS cm^− 1 in 45%RH conditions. Solid double layer capacitors were demonstrated using CNT-graphite electrodes and Li₂SO₄-PAM solid electrolytes. The voltage window of the solid cell was about 2.0 V, identical to that of a Li₂SO₄ liquid cell used as baseline. The demonstrated voltage window is significantly larger than that reported for proton- or hydroxyl-conducting electrolytes, suggesting that the Li₂SO₄-PAM electrolyte is a promising system for high energy density supercapacitors. The solid device also demonstrated excellent rate capability (up to 5 V s^− 1) and good cycle life (beyond 10,000 charge/discharge cycles).     

LiTFSI as a plastic salt in the quasi-solid state polymer electrolyte for dye-sensitized solar cells

Ionic conductivity and the type of ions are important for the composite polymer electrolyte (CPE) of the dye-sensitized solar cells (DSSCs). Lithium bis(trifluoromethane sulphone)imide (LiTFSI for short) which is easy to dissociate, is added in the composite polymer electrolyte(CPE) as a plasticizer. The LiTFSI acts differently from the conventional LiClO₄. LiTFSI changes the conformation of the polymer chain and shows higher ionic conductivity than LiClO₄. That contributes to the improvement of the short current density of the DSSC. Furthermore, the DSSCs with LiTFSI modification show higher photovoltage than the LiClO₄. The anions of TFSI^? prohibit the interface recombination more effectively compared with the LiClO₄ as the electrochemical impedance spectroscopy indicated. With the LiTFSI modified electrolyte, the performances of the DSSCs under 1 Sun, AM1.5 are improved and reaches the highest of 4.82% at the LiTFSI:LiI = 0.116:1, much better than the original DSSC(3.6%) and the LiClO₄ modified CPE electrolyte DSSC(4.32%).     

Vinyl-Tris-(methoxydiethoxy)silane as an effective and ecofriendly flame retardant for electrolytes in lithium ion batteries

In this paper, we report a new flame retardant, vinyl-Tris-(methoxydiethoxy)silane (VTMS), for use in electrolytes of lithium ion batteries. Burning tests showed that the addition of VTMS at 5–15 vol.% into the currently used electrolyte could effectively reduce the flammability. As long as the added amount was below 10%, electrochemical performance such as reversible capacity and cycling showed little change. In addition, differential scanning calorimetry (DSC) in combination with X-ray photoelectron spectroscopy (XPS) disclosed that VTMS participated in the formation of the surface film on the cathode, which played a pivotal role in markedly improving the thermal stability of the LiCoO₂ cathode. This kind of ecofriendly compound provides a new promising direction for the development of organic additives to improve the safety of lithium ion batteries.     

Large-scale synthesis of silver nanoparticles using Ag(I)–S12 polymer through electron beam irradiation

Size-controlled large scale synthesis of silver nanoparticles was performed using Ag(I)–S12 inorganic-organic hybrid polymer with supramolecular structures though electron beam irradiation. The Ag(I)–S12 polymer was simply prepared by mixing dodecanethiol with the solution of silver salts. The silver nanoparticles with various sizes were prepared from Ag(I)–S12 polymer with an electron beam voltage from 0.3 MeV to 2 MeV, current from 0.06 mA to 0.48 mA, and/or irradiation time from 1 to 10 min. The morphology and chemical composition of the irradiated samples were characterized by transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR).