Increase In Ionic Conductivity Research Articles

Structural Properties of Amorphous Vanadium Pentoxide Under Compression

Structural properties of amorphous vanadium pentoxide (V2O­5) under compression investigated by molecular dynamics simulation. The simulated amorphous V2O5 is composed of basic structural units of type VO5, VO6 at low-pressure and VO6, VO7 at high-pressure. These basic structural units connected by vertex-, edge- and face- shared links to form a structural network. The random distribution of atom and void clusters leading to a high degree of disorder in the V2O5 structure. Under compression, the fraction of average vertex-, edge- and face- shared links increased strongly. The number of VCs and VTs also increases as the large voids are divided into smaller voids. Our results also elucidated the decreasing of cross-section and increasing of length in VTs are main causes for increasing ion conductivity of the amorphous V2O5.

Influence of grain boundary plane distribution on ionic conductivity in yttria-stabilized zirconia sintered at elevated temperatures

The paper investigates electrical properties of fully stabilized zirconia, which is widely applied as a solid electrolyte in electrochemical devices such as solid oxide fuel cells. High ionic conductivity of these materials is crucial for effective operating of the devices; however, grain boundary resistivity limits conductivity in polycrystalline ceramics. Thus, optimisation of the microstructure of zirconia is necessary from an application point of view. Based on three-dimensional electron backscatter diffraction (3D EBSD) data, the research employed a complex impedance spectroscopy to establish a correlation between microstructure of cubic zirconia sinters and their conductivity. Samples with different levels of anisotropy in grain boundary plane parameters were investigated. The obtained results indicate that the conduction of ions through the grain boundaries is higher in the sample with the higher representation of the near-(001) grain boundaries. Such a relationship suggests that an over-representation of low-energy grain boundaries in zirconia polycrystals leads to an increase of ionic conductivity.

Structural investigation of solid biopolymer electrolytes: 2-hydroxyethyl cellulose doped ammonium formate as a promising proton conductor

Fabrication of solid biopolymer electrolytes (SBEs) was mainly to cater the drawbacks of lithium-ion electrolytes in terms of leakage, high cost, and toxic material. In this present work, solid biopolymer electrolytes system comprises of 2-Hydroxyethyl Cellulose (2-HEC) as polymer host, and various weight percentage (wt.%) of Ammonium Formate (AF) as ionic doping salt are produced by using solution casting technique. The relation between structural and ionic conductivity of 2-HEC/AF was analyzed and investigated by using X-Ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Electrical Impedance Spectroscopy (EIS). Through the analysis of XRD, it can be observed that the amorphous region of SBEs increases as the concentration of AF salt increases. The amorphous region of SBEs can be confirmed due to the interaction of salt concentration and polymer. However, in this present work, the broadest peak in XRD of the sample does not necessarily correlate with the highest conductivity among the samples. The interaction between polymer-salt complexes is proved through FTIR spectrum at the range of 700 cm−1 to 1300 cm−1. The highest ionic conductivity of 2-HEC/AF achieved is 2.40 × 10−3 S/cm at room temperature for SBEs containing 40 wt.% of AF. The findings from this study made it clear that the concentration of Ammonium Formate salt affects the increase in ionic conductivity.

Efficient statistical approach for thermo-electrical properties of gadolinia-doped ceria thin films

The thermo-electrical properties of gadolinia-doped ceria (GDC) thin films play a vital role in solid oxide fuel cell (SOFC) applications. Nonetheless, the effects of temperature, dopant concentration, and thickness on thermal expansion, and ionic conduction remain ambiguous. In the present study, we propose an efficient theoretical approach to emphasize the roles of surface layers and surface vicinity (called next-surface layers) on the thermo-electrical properties of GDC thin films. Using statistical moment method, thermal expansion coefficient, and ionic conductivity are calculated as functions of temperature, dopant concentration, and thickness. The lattice strain and ionic disorder in the surface and next-surface layers cause an increase in thermal expansion coefficient and ionic conductivity of thin films. Compared with bulk GDC, the thermal expansion coefficient is slightly larger while the ionic conductivity is more than one to two orders of magnitude enhancement and exhibits the maximum value at the higher concentration. The ionic conductivity depends non-linearly on the dopant concentration and the maximum conductivity is shifted toward a higher value as the temperature increases. The enhancement in thermal expansion coefficient and ionic conductivity offers new opportunities for SOFC electrolytes whose efficiency can be effectively controlled by tailoring the thickness. The theoretical calculations are compared to measured results from experiments.

Enhancement of microstructure and electrochemical properties of LLZTO solid state electrolyte by co-doping with Ga and Y

Recently, there has been strong interest in inorganic solid-state electrolytes for all-solid-state batteries, among which the garnet electrolyte LLZO has attracted much attention due to its excellent properties, such as high ionic conductivity and broad electrochemical stability. The aim of our study was to improve the performance of Ta-doped LLZO (LLZTO) by co-doping Ga and Y at the Li and La sites using conventional solid-phase synthesis methods. We thoroughly investigated how Ga and Y affect the microstructure and electrochemical properties of LLZTO. The results show that the relative density of Ga- and Y-doped LLZTO increases significantly up to 94% under the same sintering conditions. This doping resulted in a significant increase in ionic conductivity from 2.0 × 10−4 S·cm−1 to 1.05 × 10−3 S·cm−1 and a decrease in electronic conductivity from 2.16 × 10−7 S·cm−1 to 9.18 × 10−8 S·cm−1. Subsequently, the symmetric cells were assembled and tested, and it was found that the interfaces of the doped solid-state electrolytes were much more stable and that the cycling time was longer. Thus, our study successfully coordinated the co-doping of Ga, Y, and Ta, providing valuable insights for the subsequent production of LLZO materials with higher densities and better performance. This study is a promising step toward the realization of safer all-solid-state batteries with higher energy densities.

DIW 3D Printing Aligned Catkins to Access Significant Enhanced Responsive Ionogel

AbstractAlthough stimuli‐responsive gels have received significant attention due to their flexible structure and high tolerance to various stimuli, the high solvent content leads to relatively low mechanical properties and instability in performance due to water evaporation. This limits their application to some extent. Here, catkins enhanced ionogel is crafted that prevents solvent vaporization‐induced properties from abating yet remains humidity responsiveness. By using direct ink writing (DIW) 3D printing, the catkins can be aligned within the ionogel, resulting in a significant increase in ionic conductivity (0.17 S·cm−1) and mechanical properties (4.75 times). Moreover, the environment stability (−50–150 °C) and hygroscopicity of the ionic liquid (IL) allow the 3D‐printed composite to perform a controllable lubrication behavior in response to changes in humidity and temperature. This work demonstrates the significant enhancement of responsive ionogels through DIW 3D printing with aligned catkins and presents a new strategy for achieving the lubricating regulation.

Structural and dielectric properties of Eu3+,B3+ co-doped CoNb2O6 ceramic

The boron co-doped CoNb2O6:xEu3+, yB3+ (x=1, 3, 6, 9, 12 mol%, y=10 mol%) ceramics were obtained by the molten salt method, which has advantageous properties such as short reaction time, low sintering temperature, improved homogeneity, and crystallinity. The ceramic samples were examined by structural and dielectric analyses. In X-ray diffractions, the orthorhombic columbite type CoNb2O6 structure was obtained, and also a minor EuNbO4 phase was detected with increasing Eu3+ doping concentrations. Additionally, increasing Eu3+ concentration led to a slight increase in crystallite size, and two theta peak shifts occurred towards higher angles associated with shrinkage in the lattice or reduction in the lattice constant. In SEM examinations, a slight increase was observed in grain sizes from 1 to 9 mol% Eu3+ in the range of 1-30 m, while some decrease occurred in grain sizes at 12 mol%, and there was an evident increase in plate-shaped and elongated grains. The dielectric constant (ε') of the ceramic samples increased with increasing Eu3+ concentration and reached approximately 35 and 0.24 at 20 Hz for 9 mol% Eu3+, respectively. The increase in dielectric loss with increasing Eu3+ was associated with an increase in ionic conductivity, in which Eu3+ substitution does not suppress oxygen vacancies or make them more ordered.

High‐Entropy Argyrodite‐Type Sulfide Electrolyte with High Conductivity and Electro‐Chemo‐Mechanical Stability for Fast‐Charging All‐Solid‐State Batteries

AbstractInorganic solid electrolytes offer inherently unique transport, thermal, and mechanical attributes that can potentially address the fast‐charging barriers of safety, performance, and degradation exhibited by their liquid counterparts; however, to achieve reliable fast charging while retaining long cycle life remains a challenge for all‐solid‐state lithium batteries (ASSLBs), which is hindered by the electro‐chemo‐mechanical and transport issues at solid–solid interface. Herein, a high‐entropy strategy is reported to design ideal argyrodite electrolytes for fast‐charging ASSLBs with boosted transport kinetics and mitigated electrolyte‐electrode reactions via anionic site disordering. As proof of concept, multiple aliovalent cations (Si4+/Ge4+/Sn4+) and anions (Cl−) are introduced to Li6PS5Br (LPSBr) to prepare its high‐entropy counterpart, HE‐LPSBrCl. As the configuration entropy increases from 1.35 to 2.29 R, the disordering increases by 6.83‐fold and ionic conductivity increases by nearly one order of magnitude (7.96 mS cm−1 at 30 °C for HE‐LPSBrCl). The HE‐LPSBrCl full cells deliver a high capacity of 67.7 mA h g−1 at 10 C, 61.5 times higher than that of LPSBr counterparts, and retain 85.6% of the capacity (96.2 mA h g−1 at 5 C) after 1400 cycles. Unwanted mechanical penetration of Li and interfacial delamination and particle cracking of composite cathode at high rates are successfully suppressed.

Influence of Carbon Black on Conductivity and Structure of Polyethylene Oxide Based Polymer Electrolyte Film

AbstractThe potential applications of carbon black are expected to grow as science and technology improve offering up new possibilities for innovation throughout disciplines included in the field of energy storage. The present work shows the influence of carbon black to improve the ionic conductivity of the polymer electrolyte. The synthesis of polyethylene oxide: ammonium iodide based polymer electrolyte incorporated with carbon black varying from 0.01 to 0.06 wt% with respect to PEO: NH4I system by solution casting method. Different characterizations like polarized optical microscopy (POM), impedance spectroscopy, and ionic transference number (tion) are studied in detail. The maximum ionic conductivity is achieved at 0.05 wt% carbon black shows 1.20 × 10−5 S cm−1 at ambient temperature. In accordance with POM data, the amorphous region has increased whereas the crystalline region has shrunk which further indicated the increase in ionic conductivity. The value of (tion) is calculated to be 0.97 which shows the system is ionic in nature. PEO based polymer electrolyte doped carbon black can be used for the fabrication of energy storage devices.

In-Situ construction of Lithium-Ion channel within PVDF/VNs@PDA composite separators for remarkable enhanced cycle stability and safety for lithium batteries (LIBs)

In this work, a non-solvent induced phase separation (NIPS) technique was used to prepare polyvinylidene difluoride (PVDF) lithium battery (LIB) separators. Firstly, vermiculite nanosheets (VNs) coated by polydopamine (PDA), i.e., VNs@PDA, was ultrasonically dispersed in DMAc and PVDF was solution-blended with VNs@PDA with final porous composite films obtained after the extraction of DMAc. Effects of the presence of VNs@PDA on both structure and properties of PVDF films were intensively studied, and the SEM observations further suggested that the addition of VNs@PDA heavily affected the thermodynamic parameters between the polymer and solvent, causing a remarkable enhancement on the thermodynamic instability of the PVDF solution system. The polymer–solvent phase separation by the addition of less nonsolvent tended to induce the formation of long finger-like pores. An incorporation of 7.0 wt% VNs@PDA resulted in an increase in ionic conductivity of the composite membrane from 0.320 mS·cm−1 to 1.515 mS·cm−1 via AC impedance tests. The incorporation of VNs@PDA not only enhanced the hydrophilicity of the composite films (as judged by water contact angle dropping from 112.7° to 74.2°), but also significantly improved both battery performance and mechanical properties. The present study provides a facile way of fabricating LIB separators with sufficiently high safety and superior performance.

Polymer electrolyte membrane based on PVA/LiClO4 nanocomposite reinforced cellulose nanocrystalline from corncob for lithium‐ion battery

AbstractIn the field of high‐energy‐density lithium‐ion battery applications, Polymer electrolyte membranes (PEMs) have garnered significant attention due to their favorable mechanical properties and compatibility with lithium metal anodes. However, their relatively lower ionic conductivity compared to liquid electrolytes, making this problem a challenge for further research. In this study, we present a new approach to overcome these limitations, resulting in PEMs that exhibit exceptional ionic conductivity, flexibility, and interface stability. This achievement was realized by blending polyvinyl alcohol (PVA)/LiClO4 composite reinforced cellulose nanocrystalline (CNC), which is sourced from well and carefully isolated corncob cellulose. PEMs show remarkable improvements regarding ionic conductivity and mechanical strength. Membrane transparency decreased with increasing CNC addition. The maximum improvement mechanical strength was observed with the addition of 5% CNC, namely elongation at break (strain) increased by 15%. At the same composition shows an increase in ionic conductivity to 1.31 × 10−4 S/cm. This study provides the potential of precise material design and composition optimization in overcoming drawbacks associated with conventional PEMs. The findings not only advance the current understanding but also provide a promising avenue for the development of high‐performance PEMs, which are critical for the evolution of future energy storage technologies.

Fabrication of Dual-Functional Bacterial-Cellulose-Based Composite Anion Exchange Membranes with High Dimensional Stability and Ionic Conductivity.

Anion exchange membranes (AEMs) are increasingly becoming a popular research area due to their ability to function with nonprecious metals in electrochemical devices. Nevertheless, there is a challenge to simultaneously optimize the dimensional stability and ionic conductivity of AEMs due to the "trade-off" effect. Herein, we adopted a novel strategy of combining filling and cross-linking using functionalized bacterial cellulose (PBC) as a dual-functional porous support and brominated poly(phenylene oxide) (Br-PPO) as the cross-linking agent and filler. The PBC nanofiber framework together with cross-linking can provide a reliable mechanical support for the subsequent filled polymer, thus improving the mechanical properties and effectively limiting the size change of the final quaternized-PPO (QPPO)-filled PBC composite membrane. The composite membrane showed a very low swelling ratio of only 10.35%, even at a high water uptake (81.83% at 20 °C). Moreover, the existence of multiple -NR3+ groups in the cross-link bonds between BC and Br-PPO can provide extra OH- ion transport sites, contributing to the increase in ionic conductivity. The final membrane demonstrated a hydroxide ion conductivity of 62.58 mS cm-1, which was remarkably higher than that of the pure QPPO membrane by up to 235.93% (80 °C). The successful preparation of the PBC3/QPPO membrane provides an effective avenue to tackle the trade-off effect through a dual-functional strategy.

Pressure-Induced Dislocations and Their Influence on Ionic Transport in Li+-Conducting Argyrodites.

The influence of the microstructure on the ionic conductivity and cell performance is a topic of broad scientific interest in solid-state batteries. The current understanding is that interfacial decomposition reactions during cycling induce local strain at the interfaces between solid electrolytes and the anode/cathode, as well as within the electrode composites. Characterizing the effects of internal strain on ion transport is particularly important, given the significant local chemomechanical effects caused by volumetric changes of the active materials during cycling. Here, we show the effects of internal strain on the bulk ionic transport of the argyrodite Li6PS5Br. Internal strain is reproducibly induced by applying pressures with values up to 10 GPa. An internal permanent strain is observed in the material, indicating long-range strain fields typical for dislocations. With increasing dislocation densities, an increase in the lithium ionic conductivity can be observed that extends into improved ionic transport in solid-state battery electrode composites. This work shows the potential of strain engineering as an additional approach for tuning ion conductors without changing the composition of the material itself.

Design of polybenzimidazolium membranes for use in vanadium redox flow batteries.

In recent years, polybenzimidazole (PBI) membranes have been proposed for vanadium redox flow batteries (VRFBs) as an alternative to perfluoroalkylsulfonic acid membranes such as Nafion™. Despite their excellent capacity retention, PBI membranes tend to suffer from a low ionic conductivity. The formation of a polybenzimidazolium through an N-alkylation of the benzimidazole core is shown to improve the ionic conductivity of the membrane, with this class of materials having found uses in alkaline fuel cell and water electrolysis systems. However, much less is known about their incorporation into a VRFB. This article describes the use of hexamethyl-p-terphenyl polybenzimidazolium (HMT-PMBI) membranes for a vanadium redox flow battery, with the membrane characteristics in acidic media being related to their performance in a single-cell VRFB setup. A change of the degree of methylation from 56 to 65, 75, and 89% leads to an increase in ionic conductivity, correlated with an increased fraction of free water in the ionomer. The corresponding increase in cell performance is, however, accompanied by a drop in capacity retention. The membrane with a degree of methylation of 65% shows balanced properties, with a 5% higher efficiency and a two times improved capacity retention compared to Nafion™ NR212 over 200 charge-discharge cycles at 200 mA cm-2.

Recrystallization and heterovalent substitution effects on mechanical and electrical parameters of Ag6+x(P1−xGex)S5I–based ceramics

Herein, we present the results of a study of nanopowders of Ag6.25P0.75Ge0.25S5I, Ag6.5P0.5Ge0.5S5I solid solutions, and ceramic materials based on them. Nanopowders were obtained by dry grinding in a ball mill and characterized by XRD and SEM. Solid solutions based ceramic materials obtained by annealing of pressed disks were studied by SEM, EDS, EIS, and microhardness measurement. The SEM method revealed a change in the size of crystallites during recrystallization. The frequency dependence of the electrical conductivity is typical for superionic conductors. For ceramics of the composition Ag6.5P0.5Ge0.5S5I, a slight increase in ionic electrical conductivity of 3.62 × 10–2 S/cm (30 min) and 3.84 × 10–2 S/cm (60 min) is observed with a decrease in crystallite size. For the entire series of solid solutions of Ag6+x(P1−xGex)S5I, a comparative analysis of the parameters of ceramics made from micro- and nanocrystalline powders (with different grain sizes) with single crystalline samples was performed.

Nonconventional Symmetric Double-Side Electrochromic Devices Employing a Nafion Conductive Layer to Unlock Superior Durability.

In this work, we present a methodology to create an effective novel double-sided symmetric architecture of solid-state electrochromic devices. This principally new nonconventional configuration provides access to novel electrochromic systems that could be applicable for the creation of smart double-side signage, smart boards, nonemissive displays, and other smart interactive devices that change their color upon application of a voltage. The proposed configuration is based on the assembly of two identical electrochromic materials facing each other through an opaque optical separator. As a proof of concept, we use an electrochromic material based on bis(4'-(pyridin-4-yl)-2,2':6',2″-terpyridine) iron complex, covalently immobilized on screen-printed surface-extended ITO support. The symmetric configuration allows for a drastic enhancement of the overall stability of the device due to both attenuation of the counter electrode polarization and minimization of electrolyte decomposition. A nontransparent ion-permeable separator, in turn, allows observing the color change of only one of the electrodes by cutting off the optical contribution of the electrode located behind it. Further functionalization of the electrochromic material with a thin layer of Nafion is a beneficial strategy to significantly boost up long-term durability of the devices. Applying a layer of Nafion to the electrochromic material results in an increase in ionic conductivity within the device and ensures better retention of electrochromic molecules on the surface, thus minimizing device decomposition during long-term electrochemical cycling. An electrochromic device that bears Nafion-functionalized electrodes can operate (i) in the dual-side mode, where both sides demonstrate effective electrochromic performance; or (ii) in a one-side manner, where only one side of the device changes color. Notably, when operating in the one-side mode, the device withstands 70,000 cycles, after which the performance of the device can be resumed by simply turning the device to the other side (via switching the polarity of the electrodes).

Improved Lewis Acidity Using Ionic Liquid-Grafted Bimetallic Zr/Ti Uio-66 Fillers for Composite Solid Electrolytes

In recent years, solid-state lithium batteries have gained significant attention due to their high energy density and stability. However, challenges such as low ionic conductivity, non-homogeneous Li ion flux, and low interfacial compatibility of solid electrolytes still remain. Composite solid electrolytes (CSEs) have emerged as a potential solution to these issues, by combining an inorganic filler with a polymer matrix. To develop high-performance CSEs, extensive research has been conducted on inorganic active fillers with an abundance of Lewis acidic sites. The acidic sites of the filler can induce Lewis acid-base interactions, which can decrease the crystallinity of fillers by weakening the attraction between polymer segments and increasing chain mobility. Additionally, they increase the degree of dissociation of lithium salt, resulting in an increase in ionic conductivity. In terms of the concentration gradient of Li-ions, the free anion of lithium salt can be trapped by an acidic filler, thereby reducing the mobility and concentration of the anion. Finally, the acidic filler prevents the oxidation of ether oxygen groups in PEO, thus, improves its electrochemical stability. Furthermore, for increasing the ionic conductivity, inorganic filler should be an active filler capable of serving as Li-ion sources to the interfacial region between polymeric matrix and inorganic fillers, thereby facilitating Li-ion transport. Consequently, Li-ions can hop along the surface of active fillers. Therefore, in order to achieve high-performance CSEs with a polymer matrix, inorganic active fillers with an abundance of acidic sites have emerged as one of the most effective strategies for designing high performance fillers with good compatibility with the matrix. To address this technological need, in this work, we present a novel CSE based on a polyethylene oxide (PEO) matrix with a bimetallic (Zr/Ti) UiO-66-ionic liquid grafted filler (BUIL) that simultaneously modified the metal and ligand sites of UiO-66 MOF particles. The bimetallic structure of BUIL was prepared by replacing the metal sites of UiO-66 with Ti metal ions using the metal exchange method, resulting in the formation of more structural defects and an increase in the number of Lewis acid sites of filler. In addition, the pre-synthesized ionic liquids containing a -OH functional group (IL-OH), N-hydroxyhexyl-N’-methyl imidazolium bis(trifluoromethylsulfonyl)imide, were grafted when synthesizing UiO-66 with a ligand containing a -Br functional group. The BUIL filler functions as a high Lewis acid filler owing to its bimetallic structure and grafted ionic liquid. Also, to utilize BUIL as an active filler, lithium bis(trifluoromethanesulfonyl)imide/1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (IL, LiTFSI/EMIM-TFSI) was loaded into BUIL (IL@BUIL). In order to confirm the effect of Lewis acid filler interaction on PEO polymer matrix and lithium salt, various spectroscopic characterization methods were employed. As a result, CSEs containing IL@BUIL filler and PEO matrix exhibited markedly improved ionic conductivity, lithium-ion transference number, electrochemical stability, and long-cycle stability of Li metal electrode. After optimization, the ionic conductivity of CSEs at 30°C was enhanced to 0.458 mS cm-1, the lithium-ion transference number was raised to 0.668, and the electrochemical stability window was widened to 4.5 V. In addition, during a continuous plating/stripping test, the lithium metal symmetric cell of CSEs stably cycled for 500 h at a current density of 0.2 mA cm-2. Finally, LiFePO4/IL@BUIL/Li cell shows a capacity of 148 mA h g-1 at 1C.The present strategy of simultaneously modifying the metal and the ligand sites of MOF to improve the properties of CSEs can be used as a general platform for the design of a MOF filler in CSEs system, as well as a guideline for the next generation CSEs.

(Invited) Ion Transport in Solid-State Electrolytes Based on TTF - TCNQ Charge-Transfer Complexes

Current research on solid-state organic electrolytes mainly focuses on polymer electrolytes where ion transport is facilitated by chain segmental motion. The ionic conductivity of these polymer electrolytes at room temperature in too low for many practical applications. A limited number of prior reports suggest that solid-state electrolytes including organic crystalline charge-transfer complexes can have surprisingly high ionic conductivity. We report1 that processing and environmental conditions drastically impact electron and ion charge transport properties of charge-transfer complex electrolytes based on tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) mixed with lithium bis(trifluoromethylsulfonylimide) (LiTFSI). Thermal annealing and water vapor treatment decrease electronic conductivity and increase ionic conductivity. The electrolyte with 1-1-2-0.45 molar ratio of TTF-TCNQ-LiTFSI-H2O has an ionic conductivity of 2 × 10-3 S/cm at 25 °C with electronic conductivity of order 10-7 S/cm. Thermal annealing helps reduce connectivity of the charge-transfer complexes and expose more surfaces to interact with LiTFSI, thereby decreasing electronic conductivity. Exposure of the sample to water vapor then causes a substantial increase in ionic conductivity, even when the material remains in the solid state. In this presentation, we will also report on additional experimental studies of solid-state electrolytes incorporating TTF-TCNQ.Reference 1. L. Yang and J. L. Schaefer, “Water-Assisted Ion Conduction in Solid-State Charge-Transfer Complex Electrolytes for Lithium Batteries,” ChemRxiv, 2023. https://doi.org/10.26434/chemrxiv-2023-9k024

Bimetallic UiO‐66(Zr/Ti)‐Ionic Liquid Grafted Fillers with Intensified Lewis Acidity for High‐Performance Composite Solid Electrolytes

AbstractEnhancing the incorporation of highly accessible Lewis acid sites on fillers is crucial for achieving exceptional electrochemical performances in composite solid electrolytes (CSEs). Typically, they can provide a vital role in improving CSEs performance by interacting with lithium salt anions and the polymer matrix through Lewis acid–base interactions. To address this technological need, in this work, a novel filler of bimetallic UiO‐66(Zr/Ti)‐ionic liquid grafted composite (BUIL) is developed to enhance its inherent electrochemical properties. The bimetallic structure, which introduces structural defects, along with the grafted ionic liquid, abundantly creates accessible Lewis acid sites. This modification of the intrinsic Lewis acidity results in a remarkable enhancement of CSEs performances. The incorporation of BUIL in CSEs leads to a significant increase in ionic conductivity (0.458 mS cm−1) and lithium‐ion transference number (0.668) at 30 °C. Furthermore, LiFePO4/CSEs/Li cells demonstrate a high specific capacity of 148.5 mAh g−1 at a current density of 1 C, which is stably maintained over 880 cycles. Overall, the innovative synthetic approach in producing multifunctional fillers for CSEs shows strong potential for enhancing the performance of advanced lithium metal batteries.

Interface Induced Fast Ion Conduction in Complex Hydride/Oxide Nanocomposites: Interplay between Hydride and Oxide Properties

Solid-state electrolytes are crucial for next generation batteries with high energy density, long lasting and improved safety. The compatibility of most solid electrolytes with metallic anodes such as Li and Na metals, and cathodes such as sulfur, makes them suitable for high-capacity batteries (e.g., Li-S). They also address the safety concerns of current batteries by eliminating the flammable organic solvents in liquid electrolytes and by preventing/limiting dendrite formation. The lithium and sodium containing complex metal hydrides (e.g., LiBH4, NaBH4, LiCB11H12) have recently gained attention as solid-state electrolyte. They show high ionic conductivities but only at elevated temperatures (typically above 110 °C). Extending the high ionic conductivities to ambient temperatures is pivotal to the application of this fascinating class of solid electrolytes [1]. In this contribution, we will use LiBH4 and NaBH4 as examples to show that the ionic conductivities of complex hydrides can be greatly enhanced through interface effects resulting from the formation of nanocomposites with metal oxides. This strategy can lead to several orders of magnitude increase in the room temperature ionic conductivity [2]. Using DSC, DRIFT, solid-state NMR, and XRS (Xray Raman scattering), I will discuss how nanocomposite formation and presence of interfaces modifies either the phase stability, the defect concentration and/or leads to the formation of tertiary phase, and thereby increase profoundly the ion mobility of the complex hydrides. Systematic studies with different oxide nanoscaffolds and surface modified metal oxides, reveal that these effects can be optimized by tuning/engineering the nanostructure and interfaces in the nanocomposites. [3-4]. We will show that the effects also depend on a complex interplay between the stability of the metal hydride and surface properties of the metal oxide. Finally, the performance of some of the nanocomposite electrolytes in all-solid-state batteries, will be highlighted [5] References [1] L.M de Kort, P. Ngene et al. J. Journal of Alloys and Compounds 901 (2022) 163474[2] D. Blanchard et al., Advanced Functional Material. 25 (2015), 182.[3] P. Ngene et al. Physical Chemistry Chemical Physics 21 (40), 22456-22466[4] L.M de Kort, P. Ngene et al. Journal of Materials Chemistry A 8.39 (2020): 20687-20697[5] D. Blanchard et al, J. Electrochem. Soc. (2016).