Lithium Cation Transference Numbers Research Articles

FFF/FDM 3D-Printed Solid Polymer Electrolytes Based on Acrylonitrile Copolymers for Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) are essential in modern electronics, particularly in portable devices and electric vehicles. However, the limited design flexibility of current battery shapes constrains the development of custom-sized power sources for advanced applications like wearable electronics and medical devices. Additive manufacturing (AM), specifically Fused Filament Fabrication (FFF), presents a promising solution by enabling the creation of batteries with customized shapes. This study explores the use of novel poly(acrylonitrile-co-polyethylene glycol methyl ether acrylate) (poly(AN-co-PEGMEA)) copolymers as solid polymer electrolytes for lithium-ion batteries, optimized for 3D printing using FFF. The copolymers were synthesized with varying AN:PEGMEA ratios, and their physical, thermal, and electrochemical properties were systematically characterized. The study found that a poly(AN-co-PEGMEA) 6:1 copolymer ratio offers an optimal balance between printability and ionic conductivity. The successful extrusion of filaments and subsequent 3D printing of complex shapes demonstrate the potential of these materials for next-generation battery designs. The addition of succinonitrile (SCN) as a plasticizer significantly improved ionic conductivity and lithium cation transference numbers, making these copolymers viable for practical applications. This work highlights the potential of combining polymer chemistry with additive manufacturing to provide new opportunities in lithium-ion battery design and function.

Влияние концентрации перхлората лития на числа переноса катиона лития в сульфолановых растворах

To increase the accuracy of determining the lithium cation transference numbers we proposed to measure them at different values of the polarizing voltage and extrapolate the calculated values to the zero value of the polarizing voltage. It was established that the lithium cation transference numbers increased linearly with the increasing concentration of LiClO4 solutions in sulfolane. It is assumed that the increase in the lithium cation transference numbers takes place due to the change in lithium perchlorate state in sulfolane solution and the mechanism of ion transfer. It was shown that the maximum cation conductivity was achieved at the concentration of lithium perchlorate sulfolane solution of about 2M.

(Invited) Design and Development of Novel Electrolytes for Batteries and Supercapacitors

Electrolytes are often forgotten parts of batteries and super capacitors compared to numerous review papers and textbooks describing properties of electrode materials. The intention of the present work is to fill the gap and bring electrolytes to the attention of the scientists working in the field of electrochemical energy conversion and storage devices. New challenges appearing on the nowadays battery and super caps market force researchers to design novel electrolytes often baring features not found in up to date studied systems. These challenges are aimed to be addresses and discussed. In the present work three types of electrolytes for application in modern batteries or super caps will be presented and discussed.Strategy on design of new Huckel type anions for electrolyte salts is presented in the context given by the review of legacy and state-of-the-art systems. Synthesis, conditions for handling, stability and electrochemical parameters of salts used or with a potential for use in lithium-ion cells are described. Effect of solvent mixtures, selection strategy of salts and solvents for battery mixtures for maximization of chosen parameters or for given application is explained.We are going to show how crystallographic studies allow for a better understanding of electrochemical properties of Huckel type salts. Comprehensive structure analysis of crystalline materials reveals valuable information about coordination ability of anions and provides the basis to develop the model of poly (ethylene oxide) electrolytes and liquid systems. Results revealing new aggregation modes at high concentrations of lithium salts involving releasing cations by self-assembly of anionic sub network will be presented.The discovering and understanding the phenomena related to the organization of such systems in the solid state is crucial for the elaboration of novel electrolytes and gives information about cation and anion coordination in electrolytes.Also we are going to present novel hybrid polymeric electrolytes with unmodified and surface modified fillers based on silica, alumina and titania of different grain size. Special emphasize will be put on proper choice of the filler leading to preparation of composite system with enhance conductivities and lithium cation transference number compared to unmodified polymeric electrolytes.At the end we are going to discuss properties of several proton conducting gel polymeric electrolytes with various solvent ratios, to be used as electrolytes in super capacitor applications. The influence of the gel composition on the ionic conductivity, temperature behavior and electrochemical properties has been studied in a large temperature range (-40 to 80 °C)..

(Keynote) Development of Novel Lithium and Sodium Salts Based on Huckel Type Anions

Lithium salts are essential components of all electrolytes used in lithium-ion batteries. In our group in co-operation with CIC (Michel Armand) and Chalmers University (Patrik Johansson) various salts based on heterocyclic compounds with five-membered rings, such as 4, 5-dicyanoimidazole or 4, 5-dicyanotriazoles derivatives were obtained and investigated. The novel, promising concept of the application of new anions is based on the application of so called “Hückel anions”. The name came from the transposition of the Hückel rule predicting the stability of the aromatic systems. One of the most common examples of this type of anions is 4,5-dicyano-triazole (DCTA). This particular structure is completely covalently bonded and shows very stable 6p (or 10p electron if CN bonds are involved in calculations) configuration. It can be produced from commercially available precursor and even more importantly does not comprise fluorine atoms. Salts of this type of anion were found to exhibit high (~300oC) thermal stability. LiDCTA was successfully tested in PEO matrices systems as a promising, improved electrolyte for lithium ion batteries. Unfortunately DCTA failed as a component of the EC/DMC (1:1) battery electrolyte. Our idea was to design structure that would not have disadvantages of big bulky anions causing high viscosity when dissolved in organic solvents, therefore a decrease in conductivity. Also, ions of new salts should not form agglomerates after dissolution, due to ion pairs’ and triplet’s which negatively affect ionic conductivity of an electrolyte, and high transference number of a lithium cation. Molecular modelling studies showed that benzimidazolide and imidazolide anions show a typical behaviour of heterocyclic anion alternatives to PF6 -: if tailored correctly they offer more dissociative lithium ion pairs compared to LiPF6 -, but are not as electrochemically stable. The data obtained for the benzimidazolides, indicate that with very small alterations, such as the positioning of –CN substituent’s on the heterocycle, ion pairing can be changed drastically. With equal predicted properties for analogous imidazolides and benzimidazolides, the difference in anion size is an important variable for choosing an appropriate lithium salt. Overall the potential of using cyano chemistry to create new lithium salts with excellent electrochemical stabilities and ion pairing properties is evident. The previously recognized improvement of both the electrochemical stability and the lithium ion pair dissociation ability, by increasing the number of cyano groups, is apparent also for the benzimidazole salts and further strengthened by the predictions made for P (CN) 6 -. However, an increase in the number of –CN groups leads to a larger anion size and require increased synthesis efforts. Electrochemical properties of the systems doped with 4, 5-dicyano-2-trifluoromethyl imidazole lithium salt (LITDI) were most intensively studied. Crystallographic studies allowed for a better understanding of electrochemical properties of TDI salts. Despite of these studies more detailed examination of the interactions between [Li(glyme)]+ complex cations and weakly Lewis basic anions are still necessary to gain further insight into the ion coordination structure and transport mechanism in liquid and polymeric electrolytes containing LITDI as a dopant. In this presentation some recent results which enable us to design new electrolyte systems will be highlighted. As an example the new class of ionic liquid systems in which lithium salt is introduced into the solution as a lithium cation−glyme solvate. This modification leads to the reorganization of solution structure, what entails release of free mobile lithium cation solvate and hence leads to the enhancement of ionic conductivity and lithium cation transference numbers. This method enables also even three-fold increase of salt concentration in ionic liquids or dissolution of salts previously insoluble in some ionic liquids. As a further extension of the previously mentioned studies we have introduced a new family of fluorine-free solid polymer electrolytes for use in sodium battery application. Systems are based on three novel sodium salts: sodium pentacyanopropenide (NaPCPI), sodium 2,3,4,5-tetracyanopirolate (NaTCP) and sodium 2,4,5-tricyano-1,3-imidazolate (NaTIM) which were dissolved in poly (ethylene oxide) to simulate viable solid-polymer electrolytes for sodium-ion batteries. Salts were selected with respect to their fluorine-free composition and diffuse negative charges and in consequence offered special „tailored“ structure leading to better performance in electrolyte sytems. Due to this “liquid-like” high conductivities (> 1 mS cm-1) were obtained above 70 ˚C for solid-polymer electrolytes. All presented salts showed high thermal stability and suitable electrochemical stability windows up to 5V. Finally some examples of the lithium-ion and sodium –ion batteries using newly design anions will be presented and discussed.

LiTDI based lithium-ion cells electrolyte compositions

Electrolyte compositions for future lithium-anode batteries involving silicon-composite anodes are studied in this paper. The lithium salt of TDI (4,5-dicyano-2-trifluoromethanoimidazole) was used due to its high lithium cation conductivity, the low concentrations needed for good electrolyte performance (material savings), as well as its extraordinary stability against high temperatures, electrochemical potentials, and moisture, which is unmatched by other commercially available salts. A systematic investigation of the dependence of ionic conductivity on the concentration of SEI-stabilizing additives in LiTDI-based electrolytes was performed. Subsequently, the best conductive electrolyte compositions were used in half-cells involving silicon composite anodes and tested in long-term high-rate charge-discharge cycling.For all the studied systems, including electrolytes at low concentrations (0.31molkg−1), the ionic conductivity at room temperature (20°C) was above 4mScm−1. Lithium cation transference numbers were measured for the most promising samples, almost exclusively exhibiting values above 0.5. Pure electrolytes, 0.31 and 0.63molkg−1 LiTDI in EC:DMC (1:2 weight ratio), have shown anode discharge capacities as high as 1500 and 900mAhg−1, respectively. In particular, a 0.63molkg−1 concentration left little room for improvement, showing very good stability by maintaining the same (or higher) capacity for the first 125 cycles. SEI-stabilizing additives improved the cycling stability in terms of plot smoothness.

Ternary mixtures of ionic liquids for better salt solubility, conductivity and cation transference number improvement.

We hereby present the new class of ionic liquid systems in which lithium salt is introduced into the solution as a lithium cation−glyme solvate. This modification leads to the reorganisation of solution structure, which entails release of free mobile lithium cation solvate and hence leads to the significant enhancement of ionic conductivity and lithium cation transference numbers. This new approach in composing electrolytes also enables even three-fold increase of salt concentration in ionic liquids.

New Fluorine-Free Polycyano Fully-Conjugated Aliphatic Anions for Applications in Battery Electrolytes

Lithium-ion batteries are nowadays the most popular energy storage technology. A raising number of research investigates the development of modern batteries, while the market of secondary lithium batteries is still growing. This creates problems with disposal of expired batteries, as many electrolyte components comprise fluorine. Most of lithium-ion batteries research focuses on development of electrode materials. However, apart from electrodes, a key component of Li-ion batteries is electrolyte. Electrolyte limits critical battery properties, such as safety, thermal stability, battery lifetime and internal resistance of a cell. Conventional electrolytes consist of lithium salt, solvent (or solvents mixture) and additives. Since both solvents and additives are well developed and not problematic, in this work we have focused on lithium salts. Among all lithium salts that can be used in large scale manufacturing, LiPF6 is used almost exclusively. Even considering all its advantages, LiPF6has numerous drawbacks, too. These include low thermal stability, moisture sensitivity and toxic and corrosive products evolution upon decomposition [1,2]. In the recent years many studies on new lithium salts have been published, however none of them has been introduced widely to the market so far [3-7]. Therefore, there is a substantial need for new ideas in this field. Our approach was to design new anions for lithium salts tailored particularly for Li-ion battery electrolyte. The concept that we have chosen were anions based on aliphatic chain with conjugated double bonds, that allows π-electrons as well as negative charge delocalization. The chain was fully substituted with nitrile electron withdrawing groups. Application of this ideas should lead to a highly stable and weakly-coordinating anion. As a result we have synthesized two novel lithium salts: lithium pentacyanopropenide (LiPCP) and lithium hexacyano-3-azapentadienide (LiHCAP). Both salts show excellent thermal stability (up to 280 and 350 °C respectively) as proven with means of TGA and DSC. Electrochemical stability tests have shown 4.5 V window width for all salts. Conductivity of the electrolytes containing those new salts have been examined in propylene carbonate and typical battery mixtures. In both cases outstanding conductivity values has been reached, with 10 mS cm-1 have been observed at the room temperature. Lithium cation transference numbers have been investigated as well, giving satisfactory results. Finally, to evaluate compatibility with electrode materials, cycling experiments have been performed both with commercial and custom made electrodes. In conclusion, we have synthesized and thoroughly tested two members of a new class of lithium salts for applications in non-aqueous electrolytes for modern batteries. Obtained results exhibited clearly that LiPCP and LiHCAP would be successfully applied in lithium-ion batteries improving their performance, safety and environmental friendliness.

LiTDI and solvent mixture based electrolytes for lithium-ion cells

Electrolyte optimization for both best performance and low use of materials is described in this paper. Electrochemical performance and material utility are reported to achieve the goal of optimal combinations of salt concentration and solvent ratios for several solvent mixtures. A lithium 4,5-dicyano-2-trifluoromethanoimidazolide (LiTDI) salt was used for its thermal stability, ease of handling (stable in the presence of air and moisture) and high ionic conductivity at low concentration in solvents. Solvent mixtures were chosen based on industrial practice and performance at low temperature. The conductivity dependence of salt concentration is reported. In all systems, low concentration onset and a broad range of high conductivity was observed. Lithium cation transference numbers were measured for highly conductive samples and used as the secondary parameter in the optimization procedure. Both high ionic conductivity and transference number values were recorded, even for samples with low salt content: 0.3molkg−1 LiTDI in 1EC:2EMC (σ=4.18mScm−1, TLi+=0.544) and 0.4molkg−1 LiTDI in EC:DMC:EMC (σ=4.69mScm−1, TLi+=0.455). Cycling with anodic material was also carried out, showing good capacity for retention of the mixtures chosen containing average salt concentrations. Hence, material savings in comparison to other commercially available lithium salts is possible.

Functionalized polystyrene based single ion conducting gel polymer electrolyte for lithium batteries

Lithium poly(4-styrene sulfonyl (phenylsulfonyl)imide) (PSSPSI) was synthesized through the Hinsberg reaction. Since the bis(sulfonyl)imide anion is immobilized in the polymer chain, the lithium cation transference number was measured to be 0.87. The weight average number molecular weight (Mw) was found to be 105,343 determined by gel permeation chromatography (GPC). A gel polymer electrolyte membrane, comprising of PVDF and PSSPSI, was successfully prepared with the ionic conductivity of 1.1×10−3Scm−1 at room temperature. The membrane exhibits a wide electrochemical window up to 4.5V (vs. Li+/Li) and is thermally and mechanically stable. The material is well suited for applications in lithium-ion batteries.

Imidazole Anions as Electrolyte Components: Ionic Liquids, Lithium Salts, Additives

Lithium-ion cells are still the fastest developing energy storage technology. Most of the research and development power is directed towards electrode materials evolution due to their main influence on cell capacity. Electrolyte, central component connecting the electrodes, needs bigger focus due to its limitations, which also define the limitations of the cell. These are: electrochemical stability (cathode material choice limitation), thermal stability (limiting applications of the cell or enforcing use of cooling devices) and conductivity/lithium cation transference number (limiting maximum current of the cell), to mention just the most important. As solvents and lithium cation are constant part of the electrolyte, the only variable is the anion. It affects all properties mentioned above, as well as plays the critical part in ionic liquids (ILs) synthesis.As weakly-coordinating anions commercially available are known for their multiple disadvantages (notably PF6 -anion), there is a substantial need for new ideas in the field. The concept we have chosen to obtain new anions led to synthesis of heterocyclic compounds with electron withdrawing groups. The most successful member of this family so far is the LiTDI salt [1,2,3].As LiTDI is still optimized for better performance and to maximize its parameters [4], there is a room for new applications of such anions, like forming ILs [5] or use in salt form as functional additives. Increasing electrochemical stability or forming more stable SEI are among prospective use of such additives.In this very presentation we will show newest results of investigation of imidazole anions used in lithium salts – both as main electrolyte and additives. We will also show novel application of this anions’ class in ILs.As for LiTDI in liquid electrolyte, the most important achievement is the optimization of the electrolyte composition using combination of solvent ratio and salt concentration. As a result, the substantial saving of the salt use was obtained without sacrificing any electrochemical or stability parameters. Depending on solvent mixture, it can be as much as 66% savings of the material, contributing to lower overall cost of the cell.TDI and PDI anions used in ILs also behave very well. Electrochemical and thermal stability for TDI anion-based ILs is up to 4.75 V vs Li and 260˚C, respectively. Also the typical ionic conductivity decrease after lithium salt addition to the pristine IL was substantially limited as it can be seen on the Figure 1. At 20˚C conductivity for PMImTDI and BMImTDI both pristine and after salt addition is in 4-5 mS cm-1range.Also use of LiTDI analog as SEI stabilizing additive resulted in positive outcome. Series of electrolyte were tested, similarly to the experiments mentioned above, for their ionic conductivity, lithium cation transference number, electrochemical stability window and SEI stability over time.

A Polyamide Single‐Ion Electrolyte Membrane for Application in Lithium‐Ion Batteries

AbstractA bis(sulfonyl)imide incorporated, high‐molecular‐weight gel single‐ion polyamide polymer electrolyte (LiPA) is designed and synthesized by using a polycondensation reaction followed by exchange of H+ with Li+ ions. All the bis(sulfonyl)imide anions are immobilized in the polymer chains, which gives rise to a substantially higher lithium cation transference number of 0.88 than the corresponding values of conventional liquid‐based electrolytes or dual‐ion gel polymer electrolytes of inorganic salts, and also provides smooth channels for Li+ ion transport in the polymer matrix. A gel single‐ion polymer electrolyte membrane, comprised of polyvinylidene fluoride (PVDF) and LiPA, is successfully prepared with an ionic conductivity of 3.8×10−4 S cm−1 at room temperature, well suited for applications in lithium‐ion batteries. Good battery performance of the membrane is demonstrated in an assembled Li‐ion battery cell at both room temperature and at elevated temperature.

The Effect of the Enantiomeric Organization of the Solid Polymeric Electrolyte on the Ion Transport Properties Thereof

Solid Polymeric Electrolytes (SPEs) are systems which exhibit relatively high (in comparison to other solid-state systems) ionic conductivity at temperatures below 100ºC. The typical applications in which such systems can be used are electrochromic devices, fuel cells and lithium batteries. Usually, the SPE for the last above-mentioned applications consists of lithium salt dissolved in poly(ethylene oxide)- PEO. Optionally, various compounds, like ceramic powders, plasticizers or anion receptors are added to the electrolyte in order to enhance its ion transport properties. As the lithium cation conductivity of the solid-state electrolyte is several orders of magnitude lower in comparison to liquid systems (in which conductivity is at the level of about 10-2-10-3 S/cm), SPE-containing batteries can be used only in applications in which high energy density, low power density as well as low self-discharge of the battery is needed. To make the range of the possible applications for SPE-containing batteries, the lithium cation conductivity of such systems should be enhanced. One of the approaches to this problem is orientation of the electrolyte. It was proved that mechano-, electro-, or magnetoorientation of the electrolyte results in improvement of the transport properties thereof. Similar observations was made when orientation of the polyoxythylene chains by synthesis of liquid crystals and synthesis of crystalline solvates of the salts was tested. The enantioorientation of the electrolyte in the molecular level was proposed by Armand. This type of the organization of the membrane is realized by the use of the lithium salt bearing chiral anion, i.e. given enantiomer of the anion which has at least one asymmetric carbon Such application resulted in noticeable increase of the ionic conductivity, especially between 30 and 60°C. The studies conducted by Armand were, however, limited to PEO-potassium 10-camphorsulfonate system and the one in which asymmetric potassium salt of the assymeric imide of the triflic and 10-camphorsulfonic acid was used. It is worth to stress that the increase of the conductivity in the 30-60°C temperature range is very interesting when application of the SPE-containing battery as power source for peacemaker or (bio)sensor is taken into consideration. We decided to study systems containing amidates, being in which the amine part contain at least one assymeric atom of the carbon, and the acidic part comes from triflic (trifluoromethanesulfonic) acid. The tendency of such anion to ion pairing is similar to this of the triflate anion (CF3SO3 -). The important argument for this decision was that part of the amine can contain aromatic group. Paillard proved that the aromatic group can interact with the polymer matrix. Due to this, use of salt with anion containing phenyl ring in its structure should lead to the system of high lithium transference number. Therefore, it should be interesting to compare properties of the systems containing salts which anion contain (or do not contain) phenyl ring in its structure. In the presentation, the effect of chirality on the ion transport properties of the SPE will be presented. It will be shown that the organized systems (containing enantiomeric anion) exhibit better ion transport properties (lithium cation transference number and overall conductivity) in comparison to the ones which contain racemic mixtures of the enantiomers. Also the dependency between the chemical structure of the salt used and effect observed will be discussed.

New trivalent imidazole-derived salt for lithium-ion cell electrolyte

Lithium-ion cells utilize almost exclusively monovalent lithium salts as main electrolyte component. Apart from scarce works on sulfonyl imide derivatives, even in terms of basic parameters little is known about multivalent lithium salts' behavior in electrolytes. Here we present the new trivalent lithium salt dedicated to electrolytes for lithium-ion cells. Trilithium 2,2′,2″-tris(trifluoromethyl)benzotris(imidazolate) (Li3BTI) synthesis and its performance in PC and EC:DMC solutions is described in this paper. The structure and stability of this new lithium salt was fully characterized by NMR and Raman techniques as well as thermal methods. Basic electrochemical parameters of electrolytes based on this salt were done by linear sweep voltammetry, lithium cation transference number and conductivity measurements. The salt was designed specifically to manifest extraordinarily high lithium cation transference number (0.73 in EC:DMC 1:1 ratio mixture). However this new salt exhibits also thermal stability of 160 °C and electrochemical stability up to 4.5 V vs Li, as well as conductivities of the 1 mS cm−1 order of magnitude in liquid electrolytes. Promising compatibility results of the obtained electrolyte against Si/C composite anodes are also reported in this paper.

Optimization of the lithium-ion cell electrolyte composition through the use of the LiTDI salt

Optimization of electrolyte composition for future traction batteries is presented in this paper. Extensive systematic studies of electrochemical performance, material utility and subsequently cost are reported in order to obtain optimal combination. Lithium salt of TDI anion (4,5-dicyano-2-trifluoromethanoimidazole) is used due to its superior thermal stability (compared to other commercially available lithium salts), stability in case of moisture presence, electrochemical stability and possible material savings when used in electrolyte. Critical selection of solvent mixtures is made with respect to the price of components.Conductivity dependence of salt concentration is shown. For all studied systems the increased conductivity region is observed in the salt low and broad concentration range of 0.3 to 0.8molkg−1. The structural and rheological explanation of the mentioned feature is performed. Lithium cation transference numbers are measured for highly conductive samples and used as the secondary parameter in the optimization procedure. The highest values are recorded for the very low salt content: 0.31molkg−1 LiTDI in EC:DMC (1:2 weight ratio) (σ=5.09mS cm−1, tLi+=0.622) and 0.4molkg−1 LiTDI in EC:DMC:DME (8:16:1 weight ratio) (σ=6.17mS cm−1, tLi+=0.648) giving the opportunity to substantial material savings in batteries.

Liquid electrolytes based on new lithium conductive imidazole salts

In the present paper new generation of imidazole-derived lithium salts (LiTDI—lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide, LiPDI—lithium 4,5-dicyano-2-(pentafluoroethyl)imidazolide and LiHDI—lithium 4,5-dicyano-2-(n-heptafluoropropyl)imidazolide) applied in a model liquid electrolyte, with propylene carbonate used as a solvent, is described. Room temperature ionic conductivities measured by Impedance Spectroscopy are as high as 10 −2 to 10 −3 S cm −1 for the 0.1–1 mol dm −3 salt concentration range. Lithium cation transference numbers calculated using the Bruce–Vincent method exceed 0.4 at salt concentration equal to 1 mol dm −3. Interface resistance measurements showed good stability at high—0.5 mol dm −3 or low—0.01 mol dm −3 salt concentrations. Ionic associations were estimated using Fuoss–Kraus semiempirical method revealing relatively low association rates. The effect of anion structure on ionic interactions and electrochemical characteristics of the studied electrolytes is discussed.

Lithium transference number measurements and complex abilities in anion trapping triphenyloborane–poly(ethylene oxide) dimethyl ether–lithium trifluoromethanesulfonate composite electrolyte

In this paper we report the combined, positive effect of triphenyloborane (BPh 3) additive on conductivity and lithium cation transference numbers in poly(ethylene oxide) dimethyl ether (PEODME)–lithium trifluoromethanesulfonate (LiCF 3SO 3, LiTf) electrolytes. The transport mechanism is discussed on the basis of impedance measurements, restricted diffusion t + measurements, ionic association semi-empirical quantitative estimation and spectroscopic studies. A substantial increase in the lithium transference number values in triphenylborane enriched composite electrolytes was observed in comparison with the pure PEODME–LiCF 3SO 3 electrolyte. This effect is assisted by ionic conductivity enhancement.

The effect of type of the inorganic filler and dopant salt concentration on the PEO–LiClO 4 based composite electrolyte–lithium electrode interfacial resistivity

In the present paper the effect of the type of inorganic filler on the composite polymeric electrolyte–lithium electrode interfacial behavior is analyzed. Studies are performed in the wide LiClO 4 concentration range using poly(ethylene oxide)dimethyl ether (PEODME) as an electrolyte matrix. It is demonstrated that both the formation and the growth of the resistive layers at the polymer electrolyte–lithium electrode interface are determined by the salt concentration range and depend also on the type of the filler used. It is demonstrated that for salt concentrations lower than 10 −3 mol kg −1 or higher than 1 mol kg −1 addition of filler results in the suppression of the growth of the resistance of the interfacial layer. This effect has been related to an increase in lithium cation transference number observed in these salt concentration ranges in composite electrolytes compared to the pure PEODME–LiClO 4 analogues. The effect of the filler on conductivity, microstructure and thermal characteristic of electrolytes studied is also discussed.

The effect of salt concentration on the PEO–LiClO 4–lithium electrode interfacial resistivity

In the present paper the effect of the salt concentration on the formation and growth of the resistive layers at the polymer electrolyte–lithium electrode interface is analyzed. The studies are performed for poly(ethylene oxide)dimethyl ether (PEODME) doped with LiClO 4 electrolytes. It is shown that the rate of growth of the resistivity of interfacial layers depends on the concentration of the added salt and increases as the salt concentration increases. We have related this effect to the decrease in the lithium cation transference number and the increase in the fraction of ionic aggregates occurring with an increase in the salt concentration in polymeric electrolytes. The observed phenomena seem to be important from the viewpoint of application of polymeric electrolytes in lithium or (and) lithium ion batteries.

Determination of lithium transference number in PEO-DME–LiClO 4 modified with alumina powders of various surface acidity

The effect of alumina additives bearing various surface groups on conductivity and lithium cation transference numbers in poly(ethylene oxide) dimethyl ether (PEO-DME)–LiClO 4 electrolytes is examined. It is demonstrated that an increase in the conductivity and lithium transference number in composite electrolytes compared to pure PEO-DME–LiClO 4 electrolyte is observed in the limited salt concentration range. Both quantities seem to depend mostly on ionic species mobility. Also, their salt concentration dependence resembles that of viscosity of electrolytes studied. The conduction mechanism is discussed on the basis of conductivity, transference numbers and ionic association studies.

Effects of Novel Boric Acid Esters on Ion Transport Properties of Lithium Salts in Nonaqueous Electrolyte Solutions and Polymer Electrolytes

Three novel polymerizable anion receptors based on boric acid esters have been synthesized. The addition of these monomers appreciably enhanced the ionic conductivity of certain electrolyte solutions comprised of an aprotic organic solvent of low polarity and a lithium salt of low dissociation ability. Analysis of the viscosity and pulse-field-gradient spin−echo (PGSE) NMR results in association with the ionic conductivity data revealed that the conductivity enhancement originated from the increase in the degree of dissociation, resulting from the addition of these anion receptors. The 11B NMR spectra of dimethoxyethane electrolyte solutions with added boric acid ester monomers substantiated the finding that the ionic dissociation was facilitated by strong interaction between the Lewis-acidic anion receptor and Lewis-basic anions. The polymerizable anion receptor of the catechol borate derivative was cross-linked with a polyether macromonomer containing different lithium salts. The ionic conductivity could be correlated with glass transition temperatures of the polymer electrolytes by the WLF equation. The ionic conduction behavior of the boron polymer electrolytes was compared with that of the reference polymer electrolytes, and the lithium cation transference number was clarified to be higher for the former. The polymer electrolytes showed similar conduction behavior to that of the electrolyte solutions containing the anion receptor monomers.