Ionic Conductance Research Articles

Gradient-based parameter optimization method to determine membrane ionic current composition in human induced pluripotent stem cell-derived cardiomyocytes

Premature cardiac myocytes derived from human induced pluripotent stem cells (hiPSC-CMs) show heterogeneous action potentials (APs), probably due to different expression patterns of membrane ionic currents. We developed a method for determining expression patterns of functional channels in terms of whole-cell ionic conductance (Gx) using individual spontaneous AP configurations. It has been suggested that apparently identical AP configurations can be obtained using different sets of ionic currents in mathematical models of cardiac membrane excitation. If so, the inverse problem of Gx estimation might not be solved. We computationally tested the feasibility of the gradient-based optimization method. For a realistic examination, conventional 'cell-specific models' were prepared by superimposing the model output of AP on each experimental AP recorded by conventional manual adjustment of Gxs of the baseline model. Gxs of 4–6 major ionic currents of the 'cell-specific models' were randomized within a range of ± 5–15% and used as an initial parameter set for the gradient-based automatic Gxs recovery by decreasing the mean square error (MSE) between the target and model output. Plotting all data points of the MSE–Gx relationship during optimization revealed progressive convergence of the randomized population of Gxs to the original value of the cell-specific model with decreasing MSE. The absence of any other local minimum in the global search space was confirmed by mapping the MSE by randomizing Gxs over a range of 0.1–10 times the control. No additional local minimum MSE was obvious in the whole parameter space, in addition to the global minimum of MSE at the default model parameter.

Asymmetrical interface modification between electrodes and garnet-type electrolyte enabling all-solid-state lithium batteries

Garnet-based all-solid-state lithium batteries are expected to achieve high energy density and safety. However, the distinctly different chemical and electrochemical environment between the electrodes and garnet-type Li6·4La3Zr1·6Ta0·4O12 (LLZTO) electrolyte results in high interfacial impedance that greatly hinders the electrochemical performance. Herein, we propose an asymmetrical interface modification strategy by respectively introducing an ultrathin in-situ polymerized interlayer on the cathode side and a lithiophilic liquid metal coating layer on the Li metal anode side. As a result, the interfacial impedance on both side is significantly reduced to 214 Ω cm2 on the cathode side and 7.45 Ω cm2 on the Li metal anode side due to the intimate contact and enhanced wettability between Li metal and GSSE together with improved conformability on the cathode side and Li ion conductance within the cathode. Therefore, the interface modified LiFePO4||LLZTO||Li all-solid-state battery exhibits excellent cycling performance over 150 cycles with capacity retention of 96.7% and small voltage polarization of 55 mV at 0.1C and 60 °C. This work provides a convenient strategy to alleviate the interfacial issues in all-solid-state batteries.

Characterization of the surface charge property and porosity of track-etched polymer membranes.

As an important property of porous membranes, the surface charge property determines many ionic behaviors of nanopores, such as ionic conductance and selectivity. Based on the dependence of electric double layers on bulk concentrations, ionic conductance through nanopores at high and low concentrations is governed by the bulk conductance and surface charge density, respectively. Here, through the investigation of ionic conductance inside track-etched single polyethylene terephthalate (PET) nanopores under various concentrations, the surface charge density of PET membranes is extracted as ∼-0.021C/m2 at pH 10 over measurements with 40 PET nanopores. Simulations show that surface roughness can cause underestimation in surface charge density due to the inhibited electroosmotic flow. Then, the averaged pore size and porosity of track-etched multipore PET membranes are characterized by the developed ionic conductance method. Through coupled theoretical predictions in ionic conductance under high and low concentrations, the averaged pore size and porosity of porous membranes can be obtained simultaneously. Our method provides a simple and precise way to characterize the pore size and porosity of multipore membranes, especially for those with sub-100nm pores and low porosities.

The impact of Hodgkin-Huxley models on dendritic research.

For the past seven decades, the Hodgkin-Huxley (HH) formalism has been an invaluable tool in the arsenal of neuroscientists, allowing for robust and reproducible modelling of ionic conductances and the electrophysiological phenomena they underlie. Despite its apparent age, its role as a cornerstone of computational neuroscience has not waned. The discovery of dendritic regenerative events mediated by ionic and synaptic conductances has solidified the importance of HH-based models further, yielding new predictions concerning dendritic integration, synaptic plasticity and neuronal computation. These predictions are often validated through in vivo and in vitro experiments, advancing our understanding of the neuron as a biological system and emphasizing the importance of HH-based detailed computational models as an instrument of dendritic research. In this article, we discuss recent studies in which the HH formalism is used to shed new light on dendritic function and its role in neuronal phenomena.

Silicon Nitride Nanopores Formed by Simple Chemical Etching: DNA Translocations and TEM Imaging.

We demonstrate DNA translocations through silicon nitride pores formed by simple chemical etching on glass substrates using microscopic amounts of hydrofluoric acid. DNA translocations and transmission electron microscopy (TEM) prove the fabrication of nanopores and allow their characterization. From ionic measurements on 318 chips, we report the effective pore diameters ranging from zero (pristine membranes) and sub-nm to over 100 nm, within 50 μm diameter membranes. The combination of ionic conductance, DNA current blockades, TEM imaging, and electron energy loss spectroscopy (EELS) provides comprehensive information about the pore area and number, from single to few pores, and pore structure. We also show the formation of thinned membrane regions as precursors of pores. The average pore density, about 5 × 10-4 pores/μm2, allows pore number adjustment statistically (0, 1, or more). This simple and affordable chemical method for making solid-state nanopores accelerates their adoption for DNA sensing and characterization applications.

Electrical conductance of conical nanopores: Symmetric and asymmetric salts and their mixtures.

We have studied experimentally the electrical conductance-voltage curves of negatively and positively charged conical nanopores bathed in ionic solutions with monovalent, divalent, and trivalent cations at electrochemically and biologically relevant ionic concentrations. To better understand the interaction between the pore surface charge and the mobile ions, both single salts and salt mixtures have been considered. We have paid attention to the effects on the conductance of the cation valency, the pore charge asymmetry, and the pore charge inversion phenomena due to trivalent ions, both in single salts and salt mixtures. In addition, we have described how small concentrations of multivalent ions can tune the nanopore conductance due to monovalent majority ions, together with the effect of these charges on the additivity of ionic conductance and fluoride-induced negative differential conductance phenomena. This compilation and discussion of previously presented experimental data offers significant insights on the interaction between fixed and mobile charges confined in nanoscale volumes and should be useful in establishing and checking new models for describing ionic transport in the vicinity of charged surfaces.

Lithium Metal Polymer Batteries: Towards Operation at Ambient Temperature

A canonical electrolyte for lithium metal polymer batteries is PEO (Polyethylene Oxide) doped with lithium salts1. Its ionic conductivity is closely related to the local dynamics (Å, ps) of the polymer chains acting as a solid solvent. For good conductive performances, these batteries must be maintained above the melting point of the bulk PEO (TM =60°C).In order to lower this operating temperature, we propose to use one-dimensional nanoscale confinement to downshift the melting point of the confined electrolyte according to ΔTM ≈ 1/d where d is the pore diameter (Gibbs-Thomson effect)².Porous polymer composite membranes based on vertically aligned Carbon NanoTubes (VA-CNTs)3 ,4 seem to be able to meet this ambitious target. The pores are cylindrical (diameter 4nm, length 100µm) and have the particularity of being all macroscopically oriented and parallel.The effect we are seeking is driven by the curvature of the confining pore. It is then critical to ensure that only the interior of the CNTs is the permeable part of the membrane. We have followed by neutron imaging the time dependence of the penetration of the electrolyte within the membrane. We evidence a critical feature we target: only the interior of the CNTs are the permeable moieties of the membrane.As for the PEO dynamics under confinement, the electrolyte’s multiscale transport properties and ionic conductivity are characterized by PFG-NMR at the micrometer scale and Electrochemical Impedance Spectroscopy (EIS) at the macroscopic scale. We report a conductivity gain of one order of magnitude under VA-CNT confinement.Nevertheless, on a multitude of non-connected CNT pores, conductivity fluctuations are not in phase: by such classical spectroscopic techniques, only an averaged conductivity is measured. To complement the spectroscopic approach, we also probe the system by the Voltage Clamp (also called Single Pore) technique. The analysis of the conductivity noise going through a single CNT pore can indeed reveal whether the conductivity under confinement5 is due to an anomalous mobility and/or charge fluctuations.(1) Xue, Z. et al., Poly(Ethylene Oxide)-Based Electrolytes for Lithium-Ion Batteries. J. Mater. Chem. A 2015, 3 (38), 19218–19253.(2) Alba-Simionesco, C. et al., M. Effects of Confinement on Freezing and Melting. J. Phys.: Condens. Matter 2006, 18 (6), R15–R68.(3) Berrod, Q. et al., Enhanced Ionic Liquid Mobility Induced by Confinement in 1D CNT Membranes. Nanoscale 2016, 8 (15), 7845–7848.(4) Zanotti, J.-M. et al., Nanocomposite membranes for electrochemical devices. Patent WO2016151142 A1.(2016)(5) Tasserit, C. et al., Pink Noise of Ionic Conductance through Single Artificial Nanopores Revisited. Phys. Rev. Lett. 2010, 105 (26), 260602. Figure 1

Direct Acquisition of the Gap Height of Biological Tissue‐Electronic Chemical Sensor Interfaces

AbstractInterfacing biological tissues with electronic sensors offers the exciting opportunity to accurately investigate multiple biological processes. Accurate signal collection and application are the foundation of these measurements, but a long‐term issue is the signal distortion resulting from the interface gap. The height of the gap is the key characteristic needed to evaluate or model the distortion, but it is difficult to measure. By integrating a pair of nanopores at the electronic sensor plane and measuring the ion conductance between them, we developed a versatile and straightforward strategy to realize the direct cooperative evaluation of the gap height during exocytotic release from adrenal gland tissues. The signaling distortion of this gap has been theoretically evaluated and shows almost no influence on the amperometric recording of exocytosis in a classic “semi‐artificial synapse” configuration. This strategy should benefit research concerning various bio/chemical/machine interfaces.

MOF lamellar membrane-derived LLTO solid state electrolyte for high lithium ion conduction

Inorganic superionic conductor has been widely studied for potential application in all-solid-state lithium battery due to its high bulk ionic conductivity. However, the large grain boundary resistance and large thickness resulted from the poor film-forming ability, restricting its actual ionic conductivity. Inspired by the excellent film-forming ability and ultrathin thickness of 2D lamellar membrane, we reported an 11 μm-thick MOF lamellar membrane derived LLTO electrolyte (MLLTO). The electrolyte is prepared by impregnating LLTO precursors into the pores and interlayer channels of MOF lamellar membrane, followed by in situ sintering. It is demonstrated that the confined effect of interlayer channel in MOF lamellar membrane regulates the growth and arrangement of LLTO crystal, affording reduced grain boundary resistance. The porous structure of MOF nanosheet permits the construction of vertical Li+ transfer pathways between adjacent layers. Finally, MLLTO achieves a high ionic conductivity of 1.19 × 10−4 S cm−1 and ionic conductance of 0.215 S at room temperature, much higher than those of conventional LLTO electrolytes. The Li/MLLTO/Li symmetrical cell can stably cycle for 1000 h from 0.1 to 0.4 mA cm−2 at 60 °C without obvious polarization. The LFP/Li battery displays discharge capacity of 149.6 mAh g−1 at 0.5C after 200 cycles with low capacity decay of 0.04% per cycle.

Direct Acquisition of the Gap Height of Biological Tissue-Electronic Chemical Sensor Interfaces.

Interfacing biological tissues with electronic sensors offers the exciting opportunity to accurately investigate multiple biological processes. Accurate signal collection and application are the foundation of these measurements, but a long-term issue is the signal distortion resulting from the interface gap. The height of the gap is the key characteristic needed to evaluate or model the distortion, but it is difficult to measure. By integrating a pair of nanopores at the electronic sensor plane and measuring the ion conductance between them, we developed a versatile and straightforward strategy to realize the direct cooperative evaluation of the gap height during exocytotic release from adrenal gland tissues. The signaling distortion of this gap has been theoretically evaluated and shows almost no influence on the amperometric recording of exocytosis in a classic "semi-artificial synapse" configuration. This strategy should benefit research concerning various bio/chemical/machine interfaces.

Nanopore Probes Using Hydrogel-Filled Nanopipettes as Sensors for Chemical Imaging

Scanning ion conductance microscopy (SICM) using biological nanopores is a powerful analytical tool that can provide spatially resolved topography and chemical information. However, the low spatial resolution caused by the large tip diameter of the probe has limited the practical application of the SICM system. Although the tip-dip method has conventionally been used to form a lipid bilayer at the tip of pipettes, an alternative method to form the lipid bilayer is required because the lifetime of lipid bilayers formed by the tip-dip method is too short to map chemical information by stochastic nanopore sensing. Here, we propose a method to prepare lipid bilayers using a hydrogel-filled nanopipette. The lipid bilayer is formed at the tip of the pipette by inserting the pipette into a layered solution of an oil/lipid mixture and an aqueous electrolyte. Since the hydrogel supports the lipid bilayer, the lifetime of the lipid bilayers prepared by this method is improved over that formed by the tip-dip method. Furthermore, the hydrogel at the pore aperture reduces the translocation speed of analytes through nanopores, indicating that the hydrogel-filled nanopipette system can offer highly sensitive chemical sensing. Finally, we measure local single-strand deoxyribonucleic acid concentrations in the concentration gradient generated by a microhole using the biological nanopore probe. We believe that the SICM system using the hydrogel-filled nanopipette-based biological nanopore probe will offer a powerful analytical system for biological phenomena, including cell communication and signal transduction.

Ionic and morphological contributions to the variable gain of membrane responses in layer 2/3 pyramidal neurons of mouse primary visual cortex.

Many neuronal cell types exhibit a sliding scale of neuronal excitability in the subthreshold voltage range. This is due to a variable contribution of different voltage-gated ion channels, leading to scaling of input resistance (RN) as a function of membrane potential (Vm) and a voltage-dependent dynamic gain of neuronal responsiveness. In layer 2/3 pyramidal neurons within the primary visual cortex (V1), this response influences sensory processing by tightening neuronal tuning to preferred orientations, but the identity of the ionic conductances involved remains unknown. Here, we used in vitro physiological recordings in acute slices to identify the contributions of several voltage-dependent conductances to the dynamic gain of membrane responses in layer 2/3 pyramidal neurons in mouse primary visual cortex. We found that the steep voltage dependence of input resistance in these cells was mediated in part by a combination of persistent sodium, inwardly rectifying potassium, and hyperpolarization-activated nonselective cation channels. In addition, the steepness of the slope of the RN/Vm relationship was inversely correlated with the number of branches on the proximal apical dendrite. These data have uncovered physiological and morphological factors that underlie the scaling of membrane responses in L2/3 neurons of rodent V1. Regulation of these channels would serve as a mechanism of real-time neuromodulation of neuronal processing of sensory information.NEW & NOTEWORTHY Layer 2/3 pyramidal neurons in primary visual cortex scale subthreshold voltage responses with resting membrane potential because RN increases as Vm is depolarized. Here, we uncovered the voltage-dependent contributions of NaP, Kir, and HCN conductances toward this behavior, and we additionally demonstrated that the strength of the RN/Vm relationship is inversely correlated with proximal branching along the apical dendrite.

Unraveling the transport and compressibility behaviour of copper nitrates in non-aqueous solvents at 308 K temperature and 1 atmospheric pressure

In the present studies, density (ρ), viscosity (η), conductance and ultrasonic velocity (u) of copper (I) nitrate complexes were measured by conventional methods. The data was used to evaluate the transport and compressibility properties of the prepared compounds in Dimethylsulfoxide (DMSO), Pyridine (Py) and Nitromethane (NM) and in their binary mixtures: DMSO + Py and DMSO + NM at different concentrations at 308 K and 1 atmospheric pressure. The experimentally measured data was used to evaluate parameters like Limiting ionic molar conductance (λ⁰i), solvated radii (ri), ionic mobility (μ±), transport number(t±), Ionic B values (B±), Isentropic Compressibility (κs), Limiting molal ionic isentropic compressibility (κso,ø), limiting apparent molar volume (ɸ°v), Masson's coefficient (Sv), partial molar expansibilities (ɸ°E) and Hepler's constant. Trend in the transport behaviour of complexes like conductance and viscosity was discussed in terms of solvated radii and Jones Dole equation for B- coefficients respectively. Similarly, the compressibility behaviour was discussed in terms of trend in the values of limiting molal ionic isentropic compressibility's. The results were interpreted in terms of solute–solute/solute–solvent interaction and structure making/breaking characteristics of solute in the non-aqueous solution.

Cardiac cells stimulated with an axial current-like waveform reproduce electrophysiological properties of tissue fibers

Background and objective: In silico electrophysiological models are generally validated by comparing simulated results with experimental data. When dealing with single-cell and tissue scales simultaneously, as occurs frequently during model development and calibration, the effects of inter-cellular coupling should be considered to ensure the trustworthiness of model predictions. The hypothesis of this paper is that the cell-tissue mismatch can be reduced by incorporating the effects of conduction into the single-cell stimulation current. Methods: Five different stimulation waveforms were applied to the human ventricular O’Hara-Rudy cell model. The waveforms included the commonly used monophasic and biphasic (symmetric and asymmetric) pulses, a triangular waveform and a newly proposed asymmetric waveform (stimulation A) that resembles the transmembrane current associated with AP conduction in tissue. A comparison between single-cell and fiber simulated results was established by computing the relative difference between the values of AP-derived properties at different scales, and by evaluating the differences in the contributions of ionic conductances to each evaluated property. As a proof of the benefit, we investigated multi-scale differences in the simulation of the effects induced by dofetilide, a selective IKr blocker with high torsadogenic risk, on ventricular repolarization at different pacing rates. Results: Out of the five tested stimulation waveforms, stimulation A produced the closest correspondence between cell and tissue simulations in terms of AP properties at steady-state and under dynamic pacing and of ionic contributors to those AP properties. Also, stimulation A reproduced the effects of dofetilide better than the other alternative waveforms, mirroring the ’beat-skipping’ behavior observed at fast pacing rates in experiments with human tissue. Conclusions: The proposed stimulation current waveform accounts for inter-cellular coupling effects by mimicking cell excitation during AP conduction. The proposed waveform improves the correspondence between simulation scales, which could improve the trustworthiness of single-cell simulations without adding computational cost.

Thermodynamics of Charge Regulation during Ion Transport through Silica Nanochannels.

Ion-surface interactions can alter the properties of nanopores and dictate nanofluidic transport in engineered and biological systems central to the water-energy nexus. The ion adsorption process, known as "charge regulation", is ion-specific and is dependent on the extent of confinement when the electric double layers (EDLs) between two charged surfaces overlap. A fundamental understanding of the mechanisms behind charge regulation remains lacking. Herein, we study the thermodynamics of charge regulation reactions in 20 nm SiO2 channels via conductance measurements at various concentrations and temperatures. The effective activation energies (Ea) for ion conductance at low concentrations (strong EDL overlap) are ∼2-fold higher than at high concentrations (no EDL overlap) for the electrolytes studied here: LiCl, NaCl, KCl, and CsCl. We find that Ea values measured at high concentrations result from the temperature dependence of viscosity and its influence on ion mobility, whereas Ea values measured at low concentrations result from the combined effects of ion mobility and the enthalpy of cation adsorption to the charged surface. Notably, the Ea for surface reactions increases from 7.03 kJ mol-1 for NaCl to 16.72 ± 0.48 kJ mol-1 for KCl, corresponding to a difference in surface charge of -8.2 to -0.8 mC m-2, respectively. We construct a charge regulation model to rationalize the cation-specific charge regulation behavior based on an adsorption equilibrium. Our findings show that temperature- and concentration-dependent conductance measurements can help indirectly probe the ion-surface interactions that govern transport and colloidal interactions at the nanoscale─representing a critical step forward in our understanding of charge regulation and adsorption phenomena under nanoconfinement.

An Ultra-Thin Crosslinked Carbonate Ester Electrolyte for 24 V Bipolar Lithium-Metal Batteries

Fabrication of an ultrathin solid electrolyte with high conductance is essential to achieve high energy density of solid-state batteries. As solid polymer electrolytes (SPEs) are characterized by good ductility, ease of manufacturing, and low cost, the current solvent-based casting pathway suffers from the difficulty in controlling the thickness. In addition, the low ionic conductivity and narrow electrochemical window of the polyether-type SPEs further hinder their practical applications. We fabricate an ultra-thin solid-polymer electrolyte by in situ polymerization of carbonate ester vinyl ethylene carbonate and poly(ethylene glycol) diacrylate using a porous polypropylene membrane as a support. The obtained solid electrolyte is of only 8 μm and possesses an unprecedented ionic conductance of 83.3 mS at room temperature. Furthermore, the electrolyte is compatible with Li metal and can suppress dendrite growth. An all-solid-state lithium battery based on LiFePO4 cathode can operate stably for over 150 cycles with 86% capacity retention. The non-fluidic nature of the electrolyte further enables the fabrication of an energy-dense 24 V bipolar pouch cell which demonstrates extreme flexibility and safety. No voltage drop is observed upon folding and cutting. This in situ polymerized ultra-thin electrolyte provides a promising platform for the fabrication of high-energy solid-state batteries and also a potential candidate for flexible batteries.

Flexible ion-conducting membranes with 3D continuous nanohybrid networks for high-performance solid-state metallic lithium batteries

Polyethylene oxide (PEO)-based electrolytes are considered as one of the most promising solid-state electrolytes for next-generation lithium batteries with high safety and energy density; however, the drawbacks such as insufficient ion conductance, mechanical strength and electrochemical stability hinder their applications in metallic lithium batteries. To enhance their overall properties, flexible and thin composite polymer electrolyte (CPE) membranes with 3D continuous aramid nanofiber (ANF)–Li1.4Al0.4Ti1.6(PO4)3 (LATP) nanoparticle hybrid frameworks are facilely prepared by filling PEO–LiTFSI in the 3D nanohybrid scaffolds via a solution infusion way. The construction of the 3D continuous nanohybrid networks can effectively inhibit the PEO crystallization, facilitate the lithium salt dissociation and meanwhile increase the fast-ion transport in the continuous LATP electrolyte phase, and thus greatly improving the ionic conductivity (∼3 times that of the pristine one). With the integration of the 3D continuity and flexibility of the 3D ANF networks and the thermostability of the LATP phase, the CPE membranes also show a wider electrochemical window (∼5.0 V vs. 4.3 V), higher tensile strength (∼4–10 times that of the pristine one) and thermostability, and better lithium dendrite resistance capability. Furthermore, the CPE-based LiFePO4/Li cells exhibit superior cycling stability (133 mAh/g after 100 cycles at 0.3 C) and rate performance (100 mAh/g at 1 C) than the pristine electrolyte-based cell (79 and 29 mAh/g, respectively). This work offers an important CPE design criteria to achieve comprehensively-upgraded solid-state electrolytes for safe and high-energy metal battery applications.

Electrical recordings from dendritic spines of adult mouse hippocampus and effect of the actin cytoskeleton.

Dendritic spines (DS) are tiny protrusions implicated in excitatory postsynaptic responses in the CNS. To achieve their function, DS concentrate a high density of ion channels and dynamic actin networks in a tiny specialized compartment. However, to date there is no direct information on DS ionic conductances. Here, we used several experimental techniques to obtain direct electrical information from DS of the adult mouse hippocampus. First, we optimized a method to isolate DS from the dissected hippocampus. Second, we used the lipid bilayer membrane (BLM) reconstitution and patch clamping techniques and obtained heretofore unavailable electrical phenotypes on ion channels present in the DS membrane. Third, we also patch clamped DS directly in cultured adult mouse hippocampal neurons, to validate the electrical information observed with the isolated preparation. Electron microscopy and immunochemistry of PDS-95 and NMDA receptors and intrinsic actin networks confirmed the enrichment of the isolated DS preparation, showing open and closed DS, and multi-headed DS. The preparation was used to identify single channel activities and “whole-DS” electrical conductance. We identified NMDA and Ca2+-dependent intrinsic electrical activity in isolated DS and in situ DS of cultured adult mouse hippocampal neurons. In situ recordings in the presence of local NMDA, showed that individual DS intrinsic electrical activity often back-propagated to the dendrite from which it sprouted. The DS electrical oscillations were modulated by changes in actin cytoskeleton dynamics by addition of the F-actin disrupter agent, cytochalasin D, and exogenous actin-binding proteins. The data indicate that DS are elaborate excitable electrical devices, whose activity is a functional interplay between ion channels and the underlying actin networks. The data argue in favor of the active contribution of individual DS to the electrical activity of neurons at the level of both the membrane conductance and cytoskeletal signaling.

The equivalent electric conductivity of hydrochloric acid in solvents of lower permittivity than water, and its interrelation with the acid’s activity coefficient: A theoretical analysis

Theory–experiment fit for electrolytes in solvents other that pure water has always been challenging. In ionic activity, solvent’s permittivity (ε) plays an important role; at ambient pressure, ε is only a function of temperature, but in different solvents, it is also influenced by the nature of the solvent used, being smaller in less polar solvents. Employing the extended Debye–Hückel ion activity theory DH–SiS, HCl in nonaqueous or mixed solvents provided, up to moderate concentration, an excellent theory–experiment agreement even at very low ε, < 10 (Fraenkel, J. Phys. Chem. B 115 (2011) 14634). A parallel analysis is now reported for the ionic electric conductance of HCl in such solvents; specifically, in pure methanol, methanol–water mixtures, and dioxane–water mixtures. The analysis is done using DHO–SiS – a recently presented refined and extended Debye–Hückel–Onsager theory (Fraenkel, Phys. Chem. Chem. Phys. 20 (2018) 29896). In conductance, theory is further complicated by the effect of solvent’s viscosity (η) that – like ε – in addition to varying with temperature, varies also with the kind of solvent. However, good-to-excellent theory–experiment fit is achieved with different η values at ε > 30; and the equivalent conductivity proves, as before, to be theoretically interrelated with the activity coefficient. At ε < 30, a fit occurs only with an adjusted ε (εadj) postulated to reflect the influence of the exerted external electric field on solvent’s molecular arrangement.

Cellulose mesh supported ultrathin ceramic-based composite electrolyte for high-performance Li metal batteries

Oxide electrolytes show great potential in solid-state batteries due to their good stability and high ionic conductivity. However, some fatal shortcomings such as complex manufacture, large thickness, inferior flexibility and poor contact with electrodes caused by intrinsic rigidity and brittleness of oxides hinder their large-scale commercial application. Herein, an ultrathin ceramic (LAGP) membrane supported by light-weight cellulose mesh (LAC) is fabricated by a facile solution-casting method, in which a few PVDF serves as binder. Then gel electrolyte containing FEC is introduced on both sides of LAC by in-situ polymerization method to resolve the interfacial issue including poor contact and incompatibility between electrodes and LAC. The ultrathin LAC ceramic membrane presents a thickness of about 21 μm and exhibits superior flexibility, and the obtained gel electrolyte modified ceramic-based composite electrolyte (LACF) displays ultrahigh ionic conductance (86.05 mS), wide electrochemical window (4.7 V) and high Li+ transference number (0.54) at 25 °C. More importantly, the LACF composite electrolyte shows good stability to Li anode due to the LAC membrane with high proportion of mechanically-robust ceramic particles and FEC-containing gel electrolyte interlayer, which enables stable and uniform Li stripping/plating in Li/LACF/Li cell for 300 h at 0.1 mA cm−2. As a consequence, the LFP/LACF/Li full cell demonstrates excellent cyclic stability as the discharge capacity just shows an extremely minor decrease after 180 cycles at 0.5 C. Therefore, this work provides a novel insight for preparing flexible ceramic-based composite electrolyte which enables high-performance and safe Li metal batteries.