Conductivity Of Electrolyte Research Articles

Enhancing the performance of ionic conductivity for solid-state electrolytes: an effective strategy of injecting lithium ions within anionic metal-organic frameworks.

Metal-organic frameworks (MOFs) are considered as potential solid-state electrolyte (SSE) materials due to their structural diversity and porosity. Adding lithium ions into the anionic frameworks of MOFs and then realizing single-ion transport is an efficient way to enhance the performance of ionic conductivity of SSE materials. Herein, an ionotropic MOF (Li+[Cu-BTC]-) with lithium ions in the pores of the lattice was synthesized through an ion exchange strategy, which exhibits outstanding lithium ionic conducting properties over a wide temperature range (ionic conductivity: 0.11-2.96 × 10-3 S cm-1 in the temperature range of -40 to 100 °C). The strategy of injecting Li+ within anionic metal-organic frameworks provides a new opportunity for exploring advanced SSEs.

Tuning the Nucleophilicity of Anion in Lithium Salt to Enable an Anion‐Rich Solvation Sheath for Stable Lithium Metal Batteries

AbstractTraditional lithium salts typically adhere to the designing principles of enhancing cation‐anion dissociation degree to obtain a high electrolyte conductivity. This promotes the invention of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), where the symmetric electron‐withdrawing trifluoromethanesulfonyl groups significantly delocalize the negative charge density around the nitrogen atom, thereby weakening the electrostatic interaction between Li+ and the anion. Herein, deviating from the general principle, lithium (methanesulfonyl)(trifluoromethanesulfonyl) imide (LiMTFSI) is deliberately designed by substituting a unilateral electron‐withdrawing trifluoromethyl (─CF3) group of LiTFSI with an electron‐donating methyl (─CH3) group, to tune the nucleophilicity of the anion. This modification enhances Li‐anion interaction, causing the anion to replace the solvent molecules in the Li+ solvation shell. Additionally, the MTFSI− anion exhibits an elevated donor number to facilitate the solubility of LiNO3 in carbonate‐based electrolytes. The synergistic effect of these changes suppresses the decomposition of solvent and helps construct a stable solid electrolyte interphase (SEI) enriched with multiple inorganic lithium salts (e.g., Li2S, Li3N, and LiNxOy) on the Li metal anode, which enables the 500 mAh Li||LiNi0.5Co0.2Mn0.3O2 pouch cell to operate steadily for 150 cycles. It is believed this work would provide new insights and another dimension for designing functional anions beyond their role as charge carriers.

Halogen-Bonding Nanoarchitectonics in Supramolecular Plasticizers for Breaking the Trade-Off between Ion Transport and Mechanical Strength of Polymer Electrolytes for High-Voltage Li-Metal Batteries.

The low ionic conductivity of poly(ethylene oxide) (PEO)-based polymer electrolytes at room temperature impedes their practical applications. The addition of a plasticizer into polymer electrolytes could significantly promote ion transport while inevitably decreasing their mechanical strength. Herein, we report a supramolecular plasticizer (SMP) to break the trade-off effect between ionic conductivity and mechanical properties in PEO-based polymer electrolytes. Accordingly, the SMP is constructed by tetraethylene glycol dimethyl ether (G4) and SbF3 through halogen bonds. The SMP-plasticized PEO electrolyte (PEO/SMP) presents a simultaneously enhanced ionic conductivity of 2.4 × 10-4 S cm-1 (25 °C) and a high mechanical strength of 8.1 MPa, compared to those of pristine PEO-based electrolytes. Benefiting from the halogen bonds between G4 and SbF3, the Li-O coordination in PEO/SMP is evidently weakened, and thus rapid Li+ transport is achieved. Furthermore, the PEO/SMP electrolyte possesses a wide electrochemical stability window of 4.5 V and, importantly, derives an inorganic-rich SEI with a low interfacial resistance on a lithium metal surface. By using PEO/SMP, the lithium-metal battery with the LiNi0.5Co0.2Mn0.3O2 cathode exhibits a good rate and long-term cycling performance with a capacity retention of 75.3% (500 cycles). This work offers a rational guideline for the design of polymer electrolytes suitable for high-performance lithium-metal batteries.

Soft Matter Electrolytes: Mechanism of Ionic Conduction Compared to Liquid or Solid Electrolytes

Soft matter electrolytes could solve the safety problem of widely used liquid electrolytes in Li-ion batteries which are burnable upon heating. Simultaneously, they could solve the problem of poor contact between electrodes and solid electrolytes. However, the ionic conductivity of soft matter electrolytes is relatively low when mechanical properties are relatively good. In the present review, mechanisms of ionic conduction in soft matter electrolytes are discussed in order to achieve higher ionic conductivity with sufficient mechanical properties where soft matter electrolytes are defined as polymer electrolytes and polymeric or inorganic gel electrolytes. They could also be defined by Young’s modulus from about Pa to Pa. Many soft matter electrolytes exhibit VFT (Vogel–Fulcher–Tammann) type temperature dependence of ionic conductivity. VFT behavior is explained by the free volume model or the configurational entropy model, which is discussed in detail. Mostly, the amorphous phase of polymer is a better ionic conductor compared to the crystalline phase. There are, however, some experimental and theoretical reports that the crystalline phase is a better ionic conductor. Some methods to increase the ionic conductivity of polymer electrolytes are discussed, such as cavitation under tensile deformation and the microporous structure of polymer electrolytes, which could be explained by the conduction mechanism of soft matter electrolytes.

Borophosphate glass based electrolyte composite for high lithium ionic conductivity

The application requirements of solid-state lithium (Li) metal batteries are satisfied by the ionic conductivity of composite solid-state electrolytes, attributed to their minimal interfacial resistance. Herein, composite solid electrolytes were obtained by mixing a crystalline Li0.5La0.5TiO3 (LLTO) perovskite with different amount of 47Li2O-30B2O3-23P2O5 (LBP) glass phase. The results show that the crystal phase of the composite samples exhibit a tetragonal perovskite structure with a P4/mmm space group. Frequency dependent AC conductivity shows that composite containing 1 % LBP glass avoids the phenomenon of charge carrier blocking at low frequency and low temperature at the same time. The room temperature maximum total ionic conductivity was obtained for sample with 0.5 % LBP glass presenting a conductivity that is almost three times higher than that of pure LLTO. The factors influencing ionic conductivity are not only grain morphology and size, and activation energy, but also lithium content, and entropic effects contribute to the facility or difficulty with which Li+ can migrate into the LLTO solid electrolyte.

Autonomous Battery Optimization by Deploying Distributed Experiments and Simulations

AbstractNon‐trivial relationships link individual materials properties to device‐level performance. Device optimization therefore calls for new automation approaches beyond the laboratory bench with tight integration of different research methods. This study demonstrates a Materials Acceleration Platform (MAP) in the field of battery research based on the problem‐agnostic Fast INtention‐Agnostic LEarning Server (FINALES) framework, which integrates simulations and physical experiments while leaving the active control of the hardware and software resources executing experiments or simulations with the partners running the respective units. This decentralization of control is a distinctive feature of MAPs using the FINALES framework. The connected capabilities entail the formulation and characterization of electrolytes, cell assembly and testing, early lifetime prediction, and ontology‐mapped data storage provided by institutions distributed across Europe. The infrastructure is used to optimize the ionic conductivity of electrolytes and the End Of Life (EOL) of lithium‐ion coin cells by varying the electrolyte formulation. Trends in ionic conductivity are rediscovered and the effect of the electrolyte formulation on the EOL is investigated. Further, the capability of this MAP to bridge diverse research modalities, scales, and institutions enabling system‐level investigations under asynchronous conditions while handling concurrent workflows on the material‐ and system‐level is shown, demonstrating true intention‐agnosticism.

Enhancement of Low-Temperature Cycling Performance of Lithium-Ion Batteries by use of Dual Cosolvent

Abstract Lithium-ion batteries (LIBs) based on conventional electrolyte suffer from poor cycling performance at low temperatures due to the reduced ionic conductivity of electrolytes, sluggish charge transfer reaction, and Li plating during the charging process. Herein, we propose a dual cosolvent composed of methyl acetate (MA) and ethyl fluoroacetate (EFA). MA effectively reduced the viscosity of the electrolyte, improving the ionic conductivity at low temperatures. EFA facilitated the de-solvation of Li+ ions and formed an anion-derived solvation structure, enabling the formation of an inorganic-rich solid electrolyte interphase on the graphite anode. Due to the synergistic effect of MA and EFA, the graphite/LiFePO4 cell employing a dual cosolvent exhibited good cycling performance at low temperatures, delivering a discharge capacity of 68.7 mAh g-1 at -20 °C and 0.2 C and showing a capacity retention of 99.7% after 100 cycles at -20 °C and 0.33 C. Additionally, the cell exhibited an initial discharge capacity of 131.2 mAh g-1 at 25 °C and 1.0 C, with a capacity retention of 99.4% after 300 cycles. Our results demonstrate that liquid electrolytes containing dual cosolvent with various beneficial roles can be a promising solution for improving the low-temperature cycling performance of LIBs.

DNA: Novel Crystallization Regulator for Solid Polymer Electrolytes in High-Performance Lithium-Ion Batteries.

In this work, we designed a novel polyvinylidene fluoride (PVDF)@DNA solid polymer electrolyte, wherein DNA, as a plasticizer-like additive, reduced the crystallinity of the solid polymer electrolyte and improved its ionic conductivity. At the same time, due to its Lewis acid effect, DNA promotes the dissociation of lithium salts when interacting with lithium salt anions and can also fix the anions, creating more free lithium ions in the electrolyte and thus improving its ionic conductivity. However, owing to hydrogen bonding between DNA and PVDF, excess DNA occupies the lone pairs of electrons of the fluorine atoms on the PVDF molecular chains, affecting the conduction of lithium ions and the conductivity of the solid electrolyte. Hence, in this study, we investigated the effects of adding different DNA amounts to solid polymer electrolytes. The results show that 1% DNA addition resulted in the best improvement in the electrochemical performance of the electrolyte, demonstrating a high ionic conductivity of 3.74 × 10-5 S/cm (25 °C). The initial capacity reached 120 mAh/g; moreover, after 500 cycles, the all-solid-state batteries exhibited a capacity retention of approximately 71%, showing an outstanding cycling performance.

Synergistic effect of ceramic filler in polymer salt complex for improved ion dissociation and migration mechanism

Abstract Use of Ceramic filler is one of the most common approaches to improve the conductivity and stability properties of a solid polymer electrolyte (SPE) cum separator. Among them, active fillers like Garnet have been extensively used to enhance the stability and conductivity of SPE. However, SPE suffers from limited ion migration at room temperature acting as a bottleneck for their application in all solid-state batteries. An extensive study on these fillers' role in ion dissociation and migration can be a stepping stone for advanced SPE. In the present work, an FTIR analysis has primarily been used to identify and evaluate cation coordinate site-cation, and ion pair interactions in a Li6.5La3Zr1.75Te0.25O12 loaded polyethylene oxide-LiCF3SO3 matrix with varying ceramic concentrations. Further, the Trukhan model has been used to calculate diffusion coefficient, mobility, and charge carrier density to interpret relaxation parameters, conductivity, and FTIR results in the SPE samples. Finally, an ion migration model has been proposed based on the results obtained in experimental studies.

Scaling the ionic conductivity and electrochemical properties of bio-based gel polymer electrolytes reinforced with Al2O3 nanofibers for energy storage applications

Scaling the ionic conductivity and electrochemical properties of bio-based gel polymer electrolytes reinforced with Al2O3 nanofibers for energy storage applications

Fabrication of Scalable Covalent Organic Framework Membrane-based Electrolytes for Solid-State Lithium Metal Batteries.

The conventional covalent organic framework (COF)-based electrolytes with tailored ionic conducting behaviors are typically fabricated in the powder morphology, requiring further compaction procedures to operate as solid electrolyte tablets, which hinders the large-scale manufacturing of COF materials. In this study, we present a feasible electrospinning strategy to prepare scalable, self-supporting COF membranes (COMs) that feature a rigid COF skeleton bonded with flexible, lithiophilic polyethylene glycol (PEG) chains, forming an ion conduction network for Li+ transport. The resulting PEG-COM electrolytes exhibit enhanced dendrite inhibition and high ionic conductivity of 0.153 mS cm-1 at 30 °C. The improved Li+ conduction in PEG-COM electrolytes stems from the loose ion pairing in the structure and the production of higher free Li+ content, as confirmed by solid-state 7Li NMR experiments. These changes in the local microenvironment of Li+ facilitate its directional movement within the COM pores. Consequently, solid-state symmetrical Li|Li, Li|LFP, and pouch cells demonstrate excellent electrochemical performance at 60 °C. This strategy offers a universal approach for constructing scalable COM-based electrolytes, thereby broadening the practical applications of COFs in solid-state lithium metal batteries.

Effects of a Mechanically Interlocked Structure on Ionic Conductivity in Polyrotaxane-Based Polymer Electrolytes.

Polyrotaxane (PR) is a mechanically interlocked polymer (MIP) utilized as an electrolyte because of its distinctive property of dynamic molecular mobility. While numerous studies have concentrated on modifying external properties to decrease high crystallinity, few have explored the control of intrinsic properties. This study examines the crystalline properties and molecular mobility of PR-based electrolytes, along with their effects on ionic conductivity, by manipulating intrinsic properties. By systematically varying the inclusion ratio, we demonstrate that lower inclusion ratios lead to reduced crystallinity, enhancing molecular mobility. Consequently, 100PRE exhibits decreased crystallinity due to lower aggregation probabilities of α-cyclodextrins (α-CDs), longer T2 relaxation times (0.215 s), and higher ionic conductivity (3.4 × 10-3 S cm-1 at 25 °C).

Boosting Li-Ion Conductivity of Fluoride Solid Electrolyte by Low-Temperature Molten Salt Ablation and Particle Boundary Doping.

Halide solid electrolytes (SEs) are attracting great attention, owing to their high ionic conductivity and excellent high-voltage compatibility. However, severe moisture sensitivity, poor thermal stability, and instability at the lithium metal anode interface with chloride and bromide SEs retard their applications in solid-state lithium metal batteries. Fluoride SEs are expected to solve these problems, but they are now plagued by inadequate room-temperature (RT) ionic conductivity. Herein, a low-temperature molten salt (LiCl+1.33AlCl3) ablation method is proposed to enhance the ionic conductivity of monoclinic Li3GaF6 by particle boundary doping. The RT ionic conductivity of Li3GaF6 is correspondingly increased by 2 orders of magnitude, and the conductivity reaches 10-4 S cm-1 at 60 °C. The improved ionic conductivity benefits from the enhancement of interfacial ion transport, with the formation of more conductive chlorine-doped Li3GaF6-xClx and in situ binder LiAlCl4 to cement surrounding nanoparticles. The as-synthesized Li3GaF6 demonstrates outstanding humidity tolerance without conductivity degradation after exposure to a relative humidity of up to 35%. It also exhibits the widest electrochemical stability window experimentally (close to 6 V) compared with other state-of-the-art SEs. The solid-state Li/Li3GaF6/LiFePO4 cell with a stable Li+-conductive polymer interface is successfully driven for at least 200 cycles at 0.5C. Our study provides a solution to various chemical and electrochemical stability issues encountered by the halide SE family.

Ionic Covalent Organic Frameworks Consisting of Tetraborate Nodes and Flexible Linkers.

Covalent organic frameworks (COFs) have emerged as versatile materials with many applications, such as carbon capture, molecular separation, catalysis, and energy storage. Traditionally, flexible building blocks have been avoided due to their potential to disrupt ordered structures. Recent studies have demonstrated the intriguing properties and enhanced structural diversity achievable with flexible components by judicious selection of building blocks. This study presents a novel series of ionic COFs (ICOFs) consisting of tetraborate nodes and flexible linkers. These ICOFs use borohydrides to irreversibly deprotonate the alcohol monomers to achieve a high degree of polymerization. Structural analysis confirms the dia topologies. Reticulation is explored using various monomers and metal counterions. Also, these frameworks exhibit excellent stability in alcohols and coordinating solvents. The materials have been tested as single-ion conductive solid-state electrolytes. ICOF-203-Li displays one of the lowest activation energies reported for ion conduction. This tetraborate chemistry is anticipated to facilitate further structural diversity and functionality in crystalline polymers.

Congelation- and dehydration-tolerant, mechanically robust hydrogel electrolyte for durable iontronic sensors operating in open air and freezing temperatures over wide strain and pressure ranges

Conventional hydrogels have limitations in mechanical properties and are susceptible to loss of elasticity and conductivity caused by congelation and dehydration, limiting their practical uses for application in high-stress environments, open air, and freezing temperatures. This study introduces a mechanically robust, dehydration- and congelation-tolerant, and ionically conductive hydrogel electrolyte, practical for iontronic sensors working in wide pressure and strain ranges under open-air and freezing temperatures. This hydrogel electrolyte is fabricated through a reconstruction process comprising a drying-induced densification of double-network hydrogel of alginate and polyacrylamide, a structure fixation by Fe3+ crosslinking, and a Li+ infiltration. The resultant hydrogel electrolyte is tolerant to dehydration and congelation and mechanically robust, with strength and elastic modulus of a few mega-pascals comparable to those of non-conductive elastomers/rubbers used as dielectric materials. Therefore, the hydrogel electrolyte-based iontronic sensors demonstrate exceptional sensitivity and stability under compression and tension and across a wide temperature range. Further, the sensor demonstrates their practical applicability in high-stress environments from kg-range human weight to ton-range car weight. These achievements evince that iontronic sensors, based on mechanically robust and ionically conductive hydrogel electrolytes tolerant to congelation and dehydration, can be employed for practical applications.

Understanding Li6.24La3Zr2Al0.24O11.98 effect on poly(ionic liquid)-based electrolytes for high voltage solid-state lithium batteries working at room temperature

Hybrid electrolytes composed of poly(ionic liquid), ionic liquids (ILs), and fillers are very promising candidates for solid-state lithium metal batteries (SSLMBs). However, a significant knowledge gap in the field of hybrid electrolytes lies in the understanding of filler effect on properties and performance. Herein, we have investigated hybrid electrolytes based on poly(diallyldimethylammonium) bis(fluorosulfonyl)imide (PDDA-FSI), N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI), lithium bis(fluorosulfonyl)imide (LiFSI) and different loadings (from 0 to 19.2 vol%) of Li6.24La3Zr2Al0.24O11.98 (Al-LLZO) particles. All the electrolytes present a homogeneous morphology and excellent thermal stability. Moreover, our results demonstrate that Al-LLZO particles do not contribute to the ionic conductivity of the hybrid electrolytes. A 2.6 vol% of Al-LLZO led to the excellent performance in full cells at room temperature. Surprisingly, the battery performance was not correlated with the transport properties. Instead, this study found out a mechanical-performance relationship, which follows a master equation: t = A (−12.48 (1-e(1.53x10-4σy))) / P that enables to correlate the effect Al-LLZO particles on the cell performance, and predicts, for the first time, the lifetime of the battery through the mechanical properties.

Unlocking Mechanism of Anion and Cation Interaction on Ion Conduction of Polymer Based Electrolyte in Metal Batteries.

Polymer based electrolyte shows advantages in compatibly improving safety and interface stability of batteries, while its limited ion conductivity and transfer number make it difficult to apply it in batteries with high energy density. Herein, by designing four crosslinking polyesters with different electron withdrawing group (EWG), it is found that strengthening the binding of EWG to anion for weakening the binding of anion to Li+ is critical for high Li+ transfer number (tLi+) and ionic conductivity of electrolyte. As a result, poly(2,2,3,3-tetrafluoropropyl methacrylate) (PTFM) based gel polymer electrolyte (GPE) shows an ionic conductivity of 0.78 mS cm-1 and a tLi+ of 0.85, much higher than those of poly(methyl methacrylate) (PMMA) without EWG. Moreover, PTFM based GPE shows excellent flame retardancy property. Li||PTFM||NCM811 batteries with an ultrahigh capacity of 5.5 mAh cm-2 show stable cycles of 5 times to that of Li||PMMA||NCM811. Moreover, the assembled graphite||PTFM||NCM811 pouch cell shows a capacity retention rate of 92% after 500 cycles. This work clarifies the mechanism of cation||anion interaction on ionic conductivity of GPE, which is important to develop high-performance devices with good safety and flexibility.

Unlocking Mechanism of Anion and Cation Interaction on Ion Conduction of Polymer Based Electrolyte in Metal Batteries

Polymer based electrolyte shows advantages in compatibly improving safety and interface stability of batteries, while its limited ion conductivity and transfer number make it difficult to apply it in batteries with high energy density. Herein, by designing four crosslinking polyesters with different electron withdrawing group (EWG), it is found that strengthening the binding of EWG to anion for weakening the binding of anion to Li+ is critical for high Li+ transfer number (tLi+) and ionic conductivity of electrolyte. As a result, poly(2,2,3,3−tetrafluoropropyl methacrylate) (PTFM) based gel polymer electrolyte (GPE) shows an ionic conductivity of 0.78 mS cm−1 and a tLi+ of 0.85, much higher than those of poly(methyl methacrylate) (PMMA) without EWG. Moreover, PTFM based GPE shows excellent flame retardancy property. Li||PTFM||NCM811 batteries with an ultrahigh capacity of 5.5 mAh cm−2 show stable cycles of 5 times to that of Li||PMMA||NCM811. Moreover, the assembled graphite||PTFM||NCM811 pouch cell shows a capacity retention rate of 92% after 500 cycles. This work clarifies the mechanism of cation||anion interaction on ionic conductivity of GPE, which is important to develop high‐performance devices with good safety and flexibility.

Soft ionic atmosphere model for molar conductivity, diffusion coefficient and viscosity in concentrated electrolytes

Soft ionic atmosphere model for molar conductivity, diffusion coefficient and viscosity in concentrated electrolytes

Differentiable modeling and optimization of non-aqueous Li-based battery electrolyte solutions using geometric deep learning

Electrolytes play a critical role in designing next-generation battery systems, by allowing efficient ion transfer, preventing charge transfer, and stabilizing electrode-electrolyte interfaces. In this work, we develop a differentiable geometric deep learning (GDL) model for chemical mixtures, DiffMix, which is applied in guiding robotic experimentation and optimization towards fast-charging battery electrolytes. In particular, we extend mixture thermodynamic and transport laws by creating GDL-learnable physical coefficients. We evaluate our model with mixture thermodynamics and ion transport properties, where we show improved prediction accuracy and model robustness of DiffMix than its purely data-driven variants. Furthermore, with a robotic experimentation setup, Clio, we improve ionic conductivity of electrolytes by over 18.8% within 10 experimental steps, via differentiable optimization built on DiffMix gradients. By combining GDL, mixture physics laws, and robotic experimentation, DiffMix expands the predictive modeling methods for chemical mixtures and enables efficient optimization in large chemical spaces.