Ionic Conductivity Values Research Articles

Molecular dynamics simulation study of sodium ion structure & dynamics in water in ionic liquids electrolytes using 1-butyl-3-methyl imidazolium tetrafluoroborate and 1-butyl-3-methyl imidazolium hexafluorophosphate

In this paper, we have performed an all-atom molecular dynamics simulation to understand the structure and dynamics of Na+ ions in water mixed Ionic liquids (Water in Ionic liquid). Two ionic liquid (IL) systems consist of (1) 1-butyl-3-methylimidazolium [BMIM] tetrafluoroborate [BF4] and (2) 1-butyl-3-methylimidazolium [BMIM] hexafluorophosphate [PF6] were considered in this work. We understand various inter-molecular structures and dynamic and thermodynamic behaviours of Na+ ions in the water-mixed IL systems. The water (H2O) mole fractions (x) varied from 0.33 to 0.71. The neat ILs [BMIM][BF4] and [BMIM][PF6] pairwise radial distribution functions show a decrease with an increase in x. The [BMIM][PF6] exhibits a strong coordination structure with Na+ ions across the entire range of x values. The rdf between the pairs of Na+-[PF6] presents a significant interaction compared to Na+ and [BF4]. The Na + ions manifested greater coordination with H2O In H2O-[BMIM][PF6] compared to H2O-[BMIM][BF4]. The self-diffusion coefficient (D) values of Na + ions increase with the rise in x in both ILs. The D values of Na + ions are 10-fold higher in [BMIM][BF4] than [BMIM][PF6]. The ionic conductivity values are higher for [BMIM][BF4]. Overall, this paper unveils molecular-level insights for understanding the behavior of Na+ ions in the water in ionic liquid systems.

Preparation and opto-electrical characterization of poly(ethylene oxide) based polymer blends for electrochemical applications

Solid polymer electrolyte blends with varied compositions of poly(ethylene oxide) (PEO)/carboxymethyl cellulose (Na-CMC) in 10/90, 50/50, and 90/10 compositions have been successfully prepared by means of the solution cast technique at room temperature. The modification of the structural, optical, and electrical properties of the prepared blend samples was studied by employing XRD, FTIR, UV-Vis, and electrical impedance spectroscopy methods. X-ray diffraction studies revealed that the crystalline nature gradually transforms into amorphous as the Na-CMC content increases in the sample. The variation of bands noticed in the Fourier transform infrared spectroscope characteristic spectrum of the blends reveals the formation of complexes between the individual polymers. The analysis of optical properties using a UV-Vis spectrometer in the wavelength range of 900–1100nm, shows a gradual decrease in the optical indirect energy band gap with an increase in Na-CMC content in the blend. The study of the electrical properties of the blend carried out in the frequency range 50 Hz–1MHz and temperature range 303K–338K, using an electrical impedance analyzer reveals that, the dielectric constant and loss decrease with the rise in frequency, exhibiting the usual behavior of the polymers. AC conductivity is found to increase with an increase in temperature. The highest value of ionic conductivity is found to be 6.06 × 10−3Scm−1 for the blend with a 10/90 composition.

Zwitterionic Polymer Ionogel Electrolytes Supported by Coulombic Cross-Links: Impacts of Alkali Metal Cation Identity.

Zwitterionic (ZI) polymers enable the formation of noncovalent cross-links within ionic liquid electrolytes (ILEs) to create nonflammable, mechanically robust, and highly conductive ionogel electrolytes. In this study, ZI homopolymer poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] scaffolds are synthesized in situ within lithium and/or sodium salt-based ILEs to construct a series of ionogels that contain between 3 and 15 wt % poly(MPC). Room-temperature ionic conductivity values of these ionogels are found to vary between approximately 1.3 and 2.2 mS cm-1. For sodium only and 1:1 lithium/sodium equimolar mixed salt ionogels containing 6 wt % poly(MPC), the ionic conductivity is found to improve by 14% compared to the neat ILE due to the presence of the ZI scaffold. Moreover, comparing the elastic modulus values of lithium- versus sodium-containing ionogels revealed a difference of up to 1 order of magnitude [10.6 vs 111 kPa, respectively, for 3 wt % poly(MPC)]. Molecular dynamics simulations of ionogel precursor solutions corroborate the experimental results by demonstrating differences in the lithium/ZI monomer and sodium/ZI monomer cluster size distributions formed, which is hypothesized to influence the scaffold network cross-link density obtained upon photopolymerization. This work provides insights into why ZI polymer-supported ionogel properties that are relevant for the development of safer electrolytes for lithium-ion and sodium-ion batteries depend upon the chemical identity of the alkali metal cation.

Variation of electrochemical performance of Li2ZrCl6 halide solid electrolyte with Mn substitution for all-solid-state batteries

All-solid-state batteries (ASSLBs) have gained attention as a next-generation battery technology. Halide solid electrolytes may be a candidate material for next-generation batteries due to their high stability in combination with cathode-active materials and good deformability. However, the halide solid electrolyte exhibits low ionic conductivity compared to other solid electrolytes, such as oxide and sulfide solid electrolytes. In this study, in order to improve the ionic conductivity, a strategy is presented to increase the ionic conductivity by changing the Li + concentration and metal charge by doping Mn2+ in the trigonal Li2ZrCl6. Mn-doped Li2ZrCl6 is synthesized by high-energy ball-milling. Structural analysis is conducted by powder X-ray diffraction, 7Li-Nuclear magnetic resonance, Raman spectroscopy and X-ray photoelectron spectroscopy. Electrochemical performance is evaluated using electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge-discharge measurement. Each value of ionic conductivity in the bare and optimized compositions is 0.4 mS cm−1 and 0.8 mS cm−1, respectively. The activation energy of Li2ZrCl6 and 5 mol% Mn doped Li2ZrCl6 is 0.342 and 0.326 eV. Galvanostatic charge-discharge is conducted to confirm cycling performance. The initial discharge capacity for Li2ZrCl6 and 5 mol% Mn-doped Li2ZrCl6 are 171.6 and 185.6 mAh g−1, respectively.

On the prospects of using B4C3 as a potential electrode material for lithium-ion batteries

Lithium-ion batteries (LIBs) served as promising energy-storage solutions for various applications, from portable electronics to electric-vehicles. There is a growing demand for high-performance electrode materials with improved storage capacity, high cyclic stability, low energy barriers, reduced material toxicity, and cost-effectiveness. This study explores the electrochemical feasibility of B4C3 monolayer as an anode material for LIBs using density functional theory (DFT) computations and molecular dynamic (MD) simulations. The optimum anodic nature of B4C3 is reported based on its structural, electronic, diffusion, storage behaviour, and lithiation studies. The adsorption sites for Li atoms were systematically explored. The lithium saturation requires the adsorption of 29 lithium atoms on B4C3 while preserving stability confirmed by Ab-initio molecular dynamics (AIMD) simulations and ensuring favorable transport characteristics during the lithiation process based on Hirshfeld charge analysis and steric interaction calculations. The storage capacity of the host B4C3 is calculated as 2770.2 mAhg−1 which is notably higher than that of graphite anode. The computed value of open circuit voltage is 0.62 V per Li. The value of diffusion coefficient and ionic conductivity σ is 0.7 × 10−8 m2/s and 0.78 S/m respectively which predicts excellent overall anodic operation of the material. The transition barrier of the Li ions in the material is determined through Cl-NEB, which shows the lowest value of 0.06 eV along the x-axis.

PVDF-HFP Based, Quasi-Solid Nanocomposite Electrolytes for Lithium Metal Batteries.

Composite polymer electrolytes are systems of choice for future solid-state lithium metal batteries (LMBs). Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is among the most interesting matrices to develop new generation quasi-solid electrolytes (QSEs). Here it is reported on nanocomposites made of PVDF-HFP and pegylated SiO2 nanoparticles. Silica-based hybrid nanofillers are obtained by grafting chains of poly(ethylene glycol) methyl ether (PEG) with different molecular weight on the surface of silica nanoparticles. The functionalized nanofiller improves the mechanical, transport and electrochemical properties of the QSEs, which show good ionic conductivity values and high resistance against dendrite penetration, ensuring boosted long and safe device operation. The most promising result is obtained by dispersing 5wt% of SiO2 functionalized with short PEG chains (PEG750, Mw = 750gmol-1) in the PVDF-HFP matrix with an ease solvent-casting procedure. It shows ionic conductivity of 0.1mScm-1 at 25°C, more than 250h resistance to stripping/plating, and impressive results during cycling tests in LMB with LiFePO4 cathode.

Ionic Thermoelectric Generators in Vertical and Planar Topologies Based on Fluorinated Polymer Hybrid Materials with Ionic Liquids.

Ionic thermoelectrics (TEs), in which voltage generation is based on ion migration, are suitable for applications based on their low cost, high flexibility, high ionic conductivity, and wide range of Seebeck coefficients. This work reports on the development of ionic TE materials based on the poly(vinylidene fluoride-trifluoroethylene), Poly(VDF-co-TrFE), as host polymer blended with different contents of the ionic liquid, IL, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI]. The morphology, physico-chemical, thermal, mechanical, and electrical properties of the samples are evaluated together with the TE response. It is demonstrated that the IL acts as a nucleating agent for polymer crystallization. The mechanical properties and ionic conductivity values are dependent on the IL content. A high room temperature ionic conductivity of 0.008 S cm-1 is obtained for the sample with 60 wt% of [EMIM][TFSI] IL. The TE properties depend on both IL content and device topology-vertical or planar-the largest generated voltage range being obtained for the planar topology and the sample with 10 wt% of IL content, characterized by a Seebeck coefficient of 1.2 mV K-1. Based on the obtained maximum power density of 4.9 µW m-2, these materials are suitable for a new generation of TE devices.

Incorporating LLTO ceramic into PVDF/PEO polymer electrolyte for lithium-ion capacitor

Hybrid supercapacitors are a prominent energy storage option for electric vehicles because they have high power and energy densities. Electrolyte plays a major role in hybrid supercapacitor performance. Our report is on a ceramic composite polymer electrolyte made from poly (vinylidene fluoride) (PVDF)/poly (ethylene oxide) (PEO)/ Lithium Lanthanum titanate (LLTO), which we analyzed for its structure, thermal behavior, and electrical characteristics. The different weight percentages (10 wt%, 20 wt%, 30 wt% and 40 wt%) of LLTO were incorporated into the PVDF/PEO polymer blends to study the performance of the electrolyte by FTIR, microscopic analysis, TGA, and impedance spectroscopy. Based on the results, 40 wt% of LLTO containing CPE showed high liquid electrolyte uptake behaviour (275 %) and a high ionic conductivity value (3.94 mS/cm). In addition, incorporating LLTO affects the PVDF/PEO polymer backbone and enhances the amorphicity of polymer blends. This result enhances the polymer segmental motion and reduces the relaxation time. We fabricated hybrid supercapacitor coin cells using 10 wt% and 40 wt% of LLTO containing composite polymer electrolyte and tested them. The 40 wt% LLTO-containing CPE-based hybrid supercapacitor possesses a high specific capacitance value (182F/g) and a long cycle life (upto10000 cycles).

Rapid cooling method for synthesis of high conducting rhombohedral phase stabilized LiZr2(PO4)3 solid electrolyte

LiZr2(PO4)3 (LZP) solid electrolyte shows excellent stability with Li metal anode and other electrode materials but suffers due to poor ionic conductivity at ambient temperatures. It synthesizes as a low conducting (10−8 S cm−1) triclinic phase at room temperature (RT), which undergoes a phase transition to a high conducting (10−5 S cm−1) rhombohedral phase at around 60 °C. Partial substitution of Zr4+ in LZP with La3+, Sr3+, Al3+, etc. is found to stabilize this high conducting phase at RT. In this work, rhombohedral phase stabilized LZP samples are prepared via the method of rapid cooling, wherein the samples are sintered at high temperatures for relatively short durations of time followed by rapid cooling/quenching to RT. Sample properties are characterized using XRD, SEM, and impedance spectroscopy (IS) techniques. Pristine LZP which was quenched to RT after sintering for 1200 °C/5h exhibited a high RT ionic conductivity value of 0.9 × 10−5 S cm−1. This high ionic conductivity value for pristine LZP has never been reported before. Pristine LZP is mostly found to possess ionic conductivity value in the range of 10−8–10−7 S cm−1 at RT.

Manipulating ionic conductivity through chemical modifications in solid-state electrolytes prepared with binderless laser powder bed fusion processing

Additive manufacturing of solid-state batteries is advantageous for improving the power density by increasing the geometric complexity of battery components, such as electrodes and electrolytes. In the present study, bulk three-dimensional Li1+x Al x Ti2−x (PO4)3 (LATP) electrolyte samples were prepared using the laser powder bed fusion (L-PBF) additive manufacturing method. Li3PO4 (LPO) was added to LATP to compensate for lithium vaporization during processing. Chemical compositions included 0, 1, 3, and 5 wt. % LPO. Resulting ionic conductivity values ranged from 1.4 × 10−6–6.4 × 10−8 S cm−1, with the highest value for the sample with a chemical composition of 3 wt. % LPO. Microstructural features were carefully measured for each chemical composition and correlated with each other and with ionic conductivity. These features and their corresponding ranges include: porosity (ranging from 5% to 19%), crack density (0.09–0.15 mm mm−2), concentration of residual LPO (0%–16%), and concentration and Feret diameter of secondary phases, AlPO4 (11%–18%, 0.40–0.61 µm) and TiO2 (9%–11%, 0.50–0.78). Correlations between the microstructural features and ionic conductivity ranged from −0.88 to 0.99. The strongest negative correlation was between crack density and ionic conductivity (−0.88), confirming the important role that processing defects play in limiting the performance of bulk solid-state electrolytes. The strongest positive correlation was between the concentration of AlPO4 and ionic conductivity (0.99), which is attributed to AlPO4 acting as a sintering aid and the role it plays in reducing the crack density. Our results indicate that additions of LPO can be used to balance competing microstructural features to design bulk three-dimensional LATP samples with improved ionic conductivity. As such, refinement of the chemical composition offers a promising approach to improving the processability and performance of functional ceramics prepared using binderless, laser-based additive manufacturing for solid-state battery applications.

Well‐Dispersed Polydopamine In Situ Coated Lithium Montmorillonite Nanofillers Composite Polyethylene Oxide‐Based Solid Electrolyte for All‐Solid‐State Lithium Batteries

In lithium batteries, composite solid electrolytes gain their reputation owing to their great safety, excellent mechanical properties, and remarkably improved electrochemical performance. Herein, composite polyethylene oxide (PEO)‐based solid electrolytes with well‐dispersed in situ polydopamine‐coated lithium montmorillonite (PDA@LiMMT) nanofillers are successfully fabricated. The involvement of PDA@LiMMT retards significantly the crystallization of PEO, addressing a manifest enhancement in the ionic conductivity of the modified composite solid electrolyte. A conducive ionic conductivity value of 3.06 × 10−4 S cm−1 at 60 °C is reached, while the electrochemical window widens to 4.7 V. The assembled Li/solid polymer electrolytes/LiFePO4 battery exhibits a 158.2 mA h g−1 high discharge specific capacity at a current density of 0.5C; besides, the capacity retention rate keeps 86% after 200 cycles. The enhancement of the cycle stability of the solid‐state batteries highlights the excellent interfacial stability between the modified solid electrolytes and the lithium electrode, which originates from lithiophilicity of PDA.

Investigation of Raman spectra and ionic conductivity of composites based on NaClO4 and KClO4 salts obtained by mechanoactivation

The work is aimed at studying the effect of mechanical activation on the structure and electrical conductivity of the NaClO4 – and KClO4 – basedcomposites. Based on the result of the analysis of the DSC curves of the (1–x) NaClO4 – x Al2O3 and (1–x) KClO4 – x Al2O3 composites measured while heating and cooling the samples, it was established that the enthalpy of phase transitions in them decreased with an increase in the concentration of the nanosized dopant. A complication of all active vibrational contours corresponding to internal vibrations of the molecular anion in the composites with increasing Al2O3 concentration and a shift of the band of the fully symmetric stretching vibration v1 (A) to a low-frequency region was revealed by Raman spectroscopy. Based on electrochemical impedance spectroscopy data, it was determined that for the 0.4NaClO4 – 0.6Al2O3 system subjected to mechanoactivation, the values of specific ionic conductivity increased by two orders of magnitude as compared to that of pure NaClO4, while for the 0.4KClO4 – 0.6Al2O3 system, the values of specific ionic conductivity increased by three orders of magnitude as compared to the initial salt at T = 320 °C.

TlSn2F5, a SnF2-based solid electrolyte with high ionic conductivity and electrochemical stability for all-solid-state fluoride ion batteries.

Fluoride-ion batteries (FIBs) offer better theoretical energy densities and temperature stability, making them suitable alternatives to expensive Li-ion batteries. Major studies on FIBs operating at room temperature focus mainly on MSnF4 (M: Ba and Pb) solid electrolytes due to their favourable ionic conductivity values. PbSnF4 is the best fluoride ionic conductor known to date. However, it exhibits poor electrochemical stability. The present work demonstrates the development of TlSn2F5 through a single-step mechanical milling method. TlSn2F5 exhibits a better ionic conductivity value compared to the earlier reported various solid electrolytes, such as BaSnF4, KSn2F5, and La0.9Ba0.1F2.9, commonly considered for FIBs. Ionic transport number measurement using the dc polarization method indicates that TlSn2F5 is an ionic conductor. Furthermore, 19F NMR spectra measured at various temperatures demonstrate that the rise in conductivity with temperature is attributed to the rapid transport of fluoride ions. The present study indicates that TlSn2F5 can be utilized as a potential solid electrolyte for fabricating FIBs.

New ionic mesogens with high ionic conductivity based on a cyanoborate building block and lipophilic or hydrophilic counter ions

Ionic liquid crystals based on immobilised, low nucleophilic cyanoborates are designed forming SmA bilayer phases with the lowest density in ionic sections leading to considerable ion conductivity values. Structural details vary with the cation nature.

Exploring the effects of defect concentrations and distribution on Li diffusion in Li3OBr solid-state electrolyte using a deep potential model

Anti-perovskite solid-state electrolytes with high ionic conductivity have been reported to have the potential to replace conventional liquid electrolytes.

Solidification of a Silica-Based Solid Composite Electrolyte for Lithium-Ion Batteries Induced By UV Irradiation

The use of solid electrolytes in lithium-ion batteries (LIBs) instead of their liquid counterparts may significantly increase their energy density. Of particular interest are solid composite electrolytes (SCEs) which can be synthesized by incorporating ionic liquids (ILs, salts with a melting point lower than 100 °C) into a solid matrix. This class of SCE can have a wide electrochemical stability window and is typically non-flammable.Chen et al.1 developed an SCE with excellent ionic conductivity, consisting of a mesoporous silica monolith which encloses an IL electrolyte (solid nanocomposite electrolyte or nano-SCE). It is formed from a precursor solution which does not contain acids such as formic acid or HCl, meaning that it can be impregnated into porous electrodes without causing damage to the latter. However, its gelation process is long and variable (5-9 days), and is considerably affected by its presence within the electrode. As such, the nano-SCE has poor manufacturability and is not compatible with the continuous roll-to-roll processing typically used for LIB manufacturing. The manufacturability of the nano-SCE can be significantly improved by making its solidification process instantaneous upon subjection to an external trigger.As such, organic modification was used to produce silica-based precursor solutions capable of triggered solidification, for instance by irradiation with UV light. This solidification process takes a few minutes to complete and does not depend on pH, rendering it particularly versatile. The aging of the precursor solutions was studied with 29Si, 1H, and 13C NMR spectroscopy, which revealed that the alkoxysilane precursor molecules condensed into larger soluble structures over the course of five weeks. The aged precursor solutions remained stable over an indefinite period of time. When a photo-initiator is added to these solutions and they are irradiated with UV light, the soluble structures are linked together, resulting in the formation of silica nanoparticles which subsequently aggregate into a porous matrix which encapsulates the ionic liquid electrolyte (ILE).The adaptation does not compromise the functional properties such as ionic conductivity or electrochemical stability. As determined with Raman spectroscopy, the extent of organic modification and amount of ILE can be optimized to decrease the interaction of lithium ions with the other ions as compared to the neat ILE. The increased Li+ mobility means that the SCE can reach higher ionic conductivity (2.7 mS cm-1 at 20 °C) values than the neat ILE (2.5 mS cm-1). Anodic and cathodic linear sweep voltammetry in three-electrode cells was performed to determine that the SCEs can have an electrochemical stability window exceeding 5 V (i.e. lithium plating < 0 vs Li+/Li and electrolyte oxidation > 5.0 V vs Li+/Li). Electrochemical impedance spectroscopy further confirmed the SCE’s compatibility with lithium metal. As no acids are added to the precursor solution, a good electrode compatibility is expected. As such, the precursor solutions were impregnated into NMC622-based electrodes, solidified, and incorporated in half cells. These cells had an initial discharge capacity of 162 mAh g-1 at 0.1 C, retaining 86.8% of this capacity after 100 cycles.This work was supported by funding from the European Union’s Horizon 2020 research and innovation program for the Solidify project under grant agreement No. 875557.(1) Chen, X.; Put, B.; Sagara, A.; Gandrud, K.; Murata, M.; Steele, J. A.; Yabe, H.; Hantschel, T.; Roeffaers, M.; Tomiyama, M.; et al. Silica Gel Solid Nanocomposite Electrolytes with Interfacial Conductivity Promotion Exceeding the Bulk Li-Ion Conductivity of the Ionic Liquid Electrolyte Filler. Sci. Adv. 2020, 6 (2). https://doi.org/10.1126/sciadv.aav3400.

Insights into the Development and Performances of Ionogel-Based Electrolytes for Solid-State Lithium-Based Batteries

Solid-state electrolytes (SSEs) aim to overcome safety issues, decrease package volume, and increase the energy density of next-generation energy storage devices, such as Li-ion and post-lithium batteries. Among different types of SSEs, the ionogel (or ion gel) systems, in which polymer electrolytes are doped with room-temperature ionic liquids (RTILs), are amongst the most attractive choices to reach ionic conductivity values comparable to those of liquid electrolytes, ensuring better safety and electrode/electrolyte interface stability [1]. In our previous studies, several ionogel samples were prepared by in-situ UV-curing [2]. Here, we present the results of newly optimized methacrylate-based solid-state electrolyte systems conceived for ambient temperature cycling with high-energy cathodes. We characterized the electrolyte formulations using various physico-chemical and electrochemical methods, including gel content, FTIR, rheology, DMTA, TGA, SEM, voltammetry, impedance spectroscopy, and galvanostatic cycling. The focus is particularly on the influence of using two different RTILs as reaction media on the properties of the resulting materials and their electrochemical behaviours. The achieved results indicate that viscosity affects the polymerization kinetics of the ionogels, which in turn affects their thermal stability and galvanostatic cycling behavior. The obtained ready-to-use and self-standing crosslinked ionogel electrolyte membranes (~100 µm thickness) showed relatively high ionic conductivity (0.8 to 2 mS/cm at 20 °C) and anodic stability (up to 4.5-5 V vs. Li). Lithium lab-scale cells were assembled with ionogel-polymerized-on-NMC-cathodes for galvanostatic cycling measurements, and they demonstrated initial discharge capacities of around 180 mAh/g at low C-rate in the voltage range of 3.0-4.3 V at room temperature. Furthermore, motivated by the demand of increasing the overall performance of the SSEs, different types of composite solid electrolytes are now under our investigation and further development, including the utilization of active and inert inorganic fillers. For example, we introduced LLZO ceramic microparticles into the aforementioned ionogel systems for fabricating composite SSEs via in-situ photopolymerization. So far, the best achieved preliminary cycling results show enhanced and more stable cycling behaviour at higher C-rates up to 0.2C at room temperature, suggesting the promising prospects of our composite SSEs and their potential contribution to the fabrication of solid-state, high-energy lithium-based batteries.Acknowledgements: This work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860403.

Liquid-Phase Synthesis of the Li–Si–P–S–Cl Solid Electrolyte for All-Solid-State Li-Ion Battery

Sulfide solid Li-ion conductors can be applied as electrolytes for high-performance all-solid-state batteries. For establishing mass production of such sulfides, liquid-phase synthesis is an attractive alternative to conventional solid-state method. Nevertheless, the new method has only been adapted to limited compositions (i.e., the Li–P–S system) with resulting in low ionic conductivity values of < 1.5 mS cm−1 at room temperature1. This study reports the liquid-phase synthesis of solid electrolytes in the Li–Si–P–S–Cl system (Li9.54Si1.74P1.44S11.7Cl0.3: LSiPSCl)2 with the high ionic conductivity of 6.6 mS cm-1 at 298 K3.In liquid-phase method, it is essential to find appropriate dissolution conditions without decomposition reactions of the raw materials, but such conditions have not been found for Si. We investigated the dissolution conditions of Si in anhydrous acetonitrile (ACN), which typically promotes severe decomposition reactions of dissolved raw materials. However, it was found that SiS2 is highly soluble in ACN when mixed with Li2S in specific molar ratio. This composition was confirmed by ICP-AES, wherein the molar ratio of Si : Li in the homogeneous solution was determined to be 1:1. Based on this finding, LSiPSCl was synthesized by the liquid-phase approach (Fig. 1a). Two homogeneous solutions containing either (Li, Si, and S) or (Li, P, and S)4 were prepared separately and then combined. Subsequently, LiCl and Li2S were added to obtain the precursor slurry solution. The precursor slurry solution was dried at 453 K under vacuum to remove all the solvent and sintered by heating at 748 K to obtain the liquid-phase synthesized sample (L-LSiPSCl).The L-LSiPSCl exhibited high ionic conductivity of 6.6 mS cm-1 at 298 K, which was comparable to the value for the reference sample (S-LSiPSCl) synthesized by the solid-state method. All-solid-state battery cells were prepared to examine the applicability of L-LSiPSCl as a solid electrolyte (Fig. 1b), with In–Li alloy anode and the composite cathode consisting of L-LSiPSCl (or S-LSiPSCl) and LiNbO3-coated LiCoO2. The charge–discharge cycle was conducted at the current density of 0.096 mA cm-2, which corresponds to 0.2 C rate. After 100 cycles, the discharge capacity for the cell with L-LSiPSCl was 88% of its theoretical value (i.e., 137 mA h g-1 for 1.9–3.6 V vs. Li+ /In–Li), and its capacity retention was > 97%. The charge–discharge performance was slightly better than that of the cell with S-LSiPSCl. The possible slight improvement might be attributed to the characteristic particle properties of L-LSiPSCl; scanning electron microscopy and micro-Raman spectroscopy indicated L-LSiPSCl is composed of aggregated particles with pores and carbides on particle surface. Overall, this study expanded the applicability of liquid-phase synthesis and implied its potential merits for sulfide Li-ion conductors for all-solid-state batteries.Reference1) A. Miura et al., Nat. Rev. Chem., 3, 189 (2019)2) Y. Kato et al., Nat. Energy, 1, 16030 (2016)3) T. Ito et al., J. Mater. Chem. A, 10, 14392 (2022)4) M. Calpa et al., Chem. Mater., 32, 9627 (2020) Figure 1

Microstructural, electrical and thermal characterization of Dy3+, Sm3+, Er3+, Y3+ and Gd3+ multi-doped cerium dioxide as SOFCs solid electrolytes

The production of electrolytes with high ionic conductivity has been a key challenge in the progressive development of solid oxide fuel cells (SOFCs) for practical applications. Conventional approaches use ionic doping to develop electrolyte materials, such as yttria-stabilized zirconia (YSZ), but challenges remain. The doping systems discovered so far can confirm that co-doping/triple doping can introduce more oxygen vacancies to improve the electrical properties of ceria-based electrolytes compared to unitary doping. Therefore, In this work, we select the optimal dopant based on the criterion of optimal doping in cerium dioxide (effective average ionic radius close to 1.093 Å). And propose a novel multi-doped cerium-based Ce1−x(Dy1/5Sm1/5Er1/5Y1/5Gd1/5)xO2-δ (x = 0.10, 0.15, 0.20, 0.25, 0.30, abbreviated as DSEYG1, DSEYG2, DSEYG3, DSEYG4, DSEYG5) electrolytes to study its microstructure, electrical properties and thermal properties. Dy3+, Sm3+, Er3+, Y3+, and Gd3+ multi-doped electrolyte materials. Over 95% of the relative density values were obtained by sintering DSEYG series samples at 1400 °C. The single-phase cubic fluorite structure, high-density surface microstructure, elemental confirmation, and oxygen vacancy concentration were confirmed using X-ray diffraction, scanning electron microscope, energy dispersive spectrum, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electrical analysis by impedance spectroscopy confirmed the highest value of total ionic conductivity (σ800 °C= 4.04 ×10−2 S/cm) and the lowest value of activation energy (Ea= 0.834 eV) for the DSEYG3 composition. Thermal expansion analysis confirmed the moderate thermal expansion coefficient values for all compositions (TEC =11.12 ×10−6 K−1) in the range of RT-800 °C) and was found to be in good agreement with recently developed materials. The enhanced total ionic conductivity and moderate thermal expansion coefficient of DSEYG3 make it a potential electrolyte material for medium-temperature fuel cells.

Solid electrolytes based on cellulose nanocrystals with protic ionic liquid for next-generation fuel cells

AbstractThe search for solid electrolytes which have good proton conductivity in anhydrous conditions, thermal and mechanical stability, and are at the same time environmentally friendly and easy to manufacture is a big challenge which we have undertaken. This work presents new solid electrolytes based on cellulose nanocrystals with protic ionic liquid 1-methylimidazolium bis(trifluoromethylsulfonyl) imide (PIL) which have been obtained and whose thermal and conductivity properties and nanoscale organization has been determined. Two membranes were synthesized which differ as to the amount of absorbed PIL. They show excellent thermal stability up to 200 °C. The maximum value of ionic conductivity is about 10−2 S/m at 200 °C in anhydrous conditions and falls in the range of 10−3–10−2 S/m for temperatures from 150 to 200 °C. The correlation between the transport properties of membranes and their nanostructure has been probed by solid-state nuclear magnetic resonance spectroscopy. The thermal and conductivity properties of the new materials can compete with currently available membranes. Further work on a composite with a similar chemical composition should lead to obtaining a membrane capable of operating in next-generation fuel cells (T &gt; 120 °C).