Inorganic Electrolytes Research Articles

Research Progress on Improvement Strategies of Polymer Electrolytes in Solid-State Batteries

The solid electrolyte material can replace the liquid electrolyte in the lithium-ion batteries, which ensures higher safety due to the flammable and corroded of liquid electrolyte. The polymer electrolytes demonstrated feasibility due to its suitable ductility. However, lithium ions in the polymer electrolytes are more difficult to ionize, resulting in worse ionic conductivity. At the same time, the mechanical strength of polymer electrolytes is not as good as that of inorganic electrolytes, which is not enough to inhibit the penetration of lithium dendrite. To solve these problems, researchers adopt two strategies: adding fillers or reactants and constructing artificial interface layers, focusing on improving ionic conductivity and mechanical strength. Based on the latest research, the problems faced by polymer electrolytes and improvement measures are reviewed, which provide references for the future development of polymer electrolytes.

Nanostructured Solid Electrolytes for Enhanced Safety and Performance of Battery Materials

Solid-state batteries (SSB) have garnered significant attention by reason of their potential advantages over traditional liquid electrolyte batteries, including higher energy density, enhanced safety, and reduced volume. However, the development and implementation of solid electrolytes confront several challenges, such as lower ionic conductivity, dendrite formation, and interface stability issues. This review explores the current advancements in solid electrolytes (SLs), with a focus on nanostructured materials, including solid polymer electrolytes (SPEs), solid inorganic electrolytes (SIEs), and composite solid electrolytes (CSEs). The review highlights the benefits of nanostructuring in improving mechanical intensity, ionic conductivity and thermostability. Key methods for synthesizing nanostructured solid electrolytes (NSLs), such as the sol-gel method and 3D printing, are discussed. Additionally, the review addresses critical challenges, including the high cost of materials and manufacturing processes, and proposes future research directions to overcome these barriers. The purpose is to comprehensively understand the current status and future potential of NSL in promoting SSB technology.

Novel Anodic TiO2 Synthesis Method with Embedded Graphene Quantum Dots for Improved Photocatalytic Activity

Photocatalytic degradation of pollutants have a high potential for sustainable and renewable uses. TiO2 is a widely studied photocatalyst due to its high chemical and photochemical stability and wide range of applications. However, the wide band gap and low capacity of photo-induced charge separation provide lower catalytic activity; thus, improvement of these properties must be found. The doping of TiO2 with other elements, such as carbon nanoparticles (CNP) in a quantum dot form, offers a promising pathway to improve the aforementioned properties. In addition, in situ doping methods should be investigated for practical scalability, as they offer the advantage of integrating dopants directly during material synthesis, ensuring a more uniform distribution and better interaction between the dopant and the host material, in turn leading to more consistent photocatalytic properties. Current technologies primarily involve nanoparticle combinations. This work focuses on the development of a novel in situ synthesis methodology by the introduction of three different graphene-based quantum nanodots into anodic TiO2 and the following investigation of structural, morphological, and photocatalytic properties. Results indicate that the introduction of CNP allows for the shift of a set of parameters, such as the optical band gap, increased photo-induced charge carrier density of TiO2/CNP composite, and, most importantly, the change of crystalline phase composition depending on added CNP material. Research indicates that not only a higher concentration of added CNP enhances higher photocatalytic activity as tested by the degradation of methylene blue dye, but also the type of CNP determines final crystalline phase. For the first time brookite and rutile phases were obtained in anodic titania synthesized in inorganic electrolyte by introducing hydrothermally treated exfoliated graphene.

In Situ Optical Observation of Lithium Dendrite Pattern in Solid Polymer Electrolytes.

Solid polymer electrolytes (SPEs) have been treated as a viable solution to build high-performance solid-state lithium metal batteries (SSLMBs) at the industrial level, bypassing the safety and energy density dilemmas experienced by today's lithium-ion battery technology. To promote a wider application of SPEs-based SSLMBs, the chemical and electrochemical characteristics of lithium metal (Li°) electrode in SPEs have to be clearly elucidated. In this work, the morphological evolution of Li° electrode in the SPEs-based SSLMBs is comprehensively investigated, via a customized electrochemical cell allowing optical microscopic analyses. The results demonstrate that differing from inorganic solid electrolytes, the elastic feature of SPEs eliminates the "memory effect" of the dendrite formation, in which the previously formed dendrites can be dissolved and the resulting space can be simultaneously occupied by electrolyte components, instead of leaving for a second-round growth of Li° dendrites. Furthermore, the largely increased electronic conductivities of the as-formed interphases between Li° electrode and SPEs are found to be responsible for the notoriously soft short-circuit behavior observed during cycling. These findings bring a fresh understanding of the formation and evolution of lithium dendrites in SPE-based cells, which are vital for improving the long-term stability of SSLMBs and other related high-energy battery systems.

Breath inspired multifunctional low-cost inorganic colloidal electrolyte for stable zinc metal anode

The practical application of aqueous zinc-ion batteries (AZIBs) is primarily constrained by issues such as corrosion, zinc dendrite formation, and the hydrogen evolution reaction occurring at the zinc metal anode. To overcome these challenges, strategies for optimizing the electrolyte are crucial for enhancing the stability of the zinc anode. Inspired by the role of hemoglobin in blood cells, which facilitates oxygen transport during human respiration, an innovative inorganic colloidal electrolyte has been developed: calcium silicate-ZnSO4 (denoted as CS-ZSO). This electrolyte operates in weak acidic environment and releases calcium ions, which participate in homotopic substitution with zinc ions, while the solvation environment of hydrated zinc ions in the electrolyte is regulated. The reduced energy barrier for the transfer of zinc ions and the energy barrier for the desolvation of hydrated ions imply faster ion transfer kinetics and accelerated desolvation processes, thus favoring the mass transfer process. Furthermore, the silicate colloidal particles act as lubricants, improving the transfer of zinc ions. Together, these factors contribute to the more uniform concentration of zinc ions at the electrode/electrolyte interface, effectively inhibiting zinc dendrite formation and reducing by-product accumulation. The Zn//CS-ZSO//Zn symmetric cell demonstrates stable operation for over 5000 h at 1 mA cm−2, representing 29-fold improvement compared to the Zn//ZSO//Zn symmetric cell, which lasts only 170 h. Additionally, the Zn//CS-ZSO//Cu asymmetric cell shows stable average Coulombic efficiency (CE) exceeding 99.6% over 2400 cycles, significantly surpassing the performance of the ZSO electrolyte. This modification strategy for electrolytes not only addresses key limitations associated with zinc anodes but also provides valuable insights into stabilizing anodes for the advancement of high-performance aqueous zinc-ion energy storage systems.

Advances in inorganic solid electrolytes for lithium-ion batteries

Advances in inorganic solid electrolytes for lithium-ion batteries

A near-single-ion conducting polymer-in-ceramic electrolyte for solid-state lithium metal batteries with superior cycle stability and rate capability

Composite solid-state electrolytes (CSE) represent a promising alternative to conventional porous separators and organic liquid electrolyte systems in commercialized lithium metal battery (LMBs), offering effective dendrite suppression, high interfacial compatibility and enhanced cycle life. This study introduces a polymer-in-ceramic electrolyte, which is synthesized by blending perovskite-type inorganic electrolyte Li1.5La1.5TeO6 (LLTeO) with polymethyl methacrylate (PMMA) and polyvinylidene fluoride (PVDF), denoted as PMMA/PVDF-LLTeO. The resulting CSE features a dense, non-porous structure, high mechanical strength, excellent thermal stability, and a broad electrochemical window. Notably, with the incorporation of a high ceramic filler content (up to 70 %), the CSE promotes a hybrid ion transport mechanism, yielding a near-single-ion conducting behavior with an ion transference number of 0.833, and a high elastic modulus of approximately 1 GPa. These attributes collectively contribute to the suppression of dendrite growth, as analyzed through multiphysics-based simulations. Li//Li symmetric cells using PMMA/PVDF-LLTeO-70 exhibit robust lithium stripping-plating stability, with a critical current density of 0.45 mA cm−2. Furthermore, the corresponding Li//LiFePO4 cells exhibit superior rate performance and cyclic stability, achieving over 150 cycles with a capacity retention rate of 92.2 % at high temperatures (60 °C). This research highlights the potential of the proposed CSE with high-temperature applications, significantly improving the safety and performance of LMBs

Research and Application of Thermally Activated Gel for Control of Lost Circulations

Summary Thermally activated gel (TAG) for control of lost circulations was evaluated, which is based on acrylamide (AM) and N-vinylpyrrolidone (NVP) copolymers crosslinked by polyethyleneimine (PEI). Viscoelasticity, pumpable time, breakthrough pressures, thermal tolerance, and fluid compatibility were tested in this paper, and then field applications in Missan Oilfield, Iraq, were introduced. Laboratory results showed that the strain limit in the linear viscoelastic region was 169% and storage modulus was 870 Pa. Pumpable time of TAG varies with pH values, so pumpable time can be controlled above 60 minutes by adjusting pH values in the temperature ranges of 100°C to 140°C. Breakthrough pressures were tested in 5-mm (inner diameter) and 10-mm (inner diameter) simulating pipes.The breakthrough pressure gradients were 1.172 psi/cm and 1.200 psi/cm at 0.5 mL/min and 1.0 mL/min, respectively, for 10-mm simulating pipes, 1.872 psi/cm and 2.200 psi/cm for 5-mm simulating pipes. TAG maintained morphologies completely and dehydrated slightly after 30 days of aging at 140°C, transformed into a degraded and low-viscosity fluid after 45 days of aging. Tests proved that invasions of inorganic electrolytes, drilling fluid additives, and drilling fluids can lengthen the pumpable time of TAG, so flash settings due to invasions could not occur. Applications in Missan Oilfield verified the performances of TAG mentioned above.

Fluorinated co-solvent electrolytes enable lithium metal batteries to operate at low temperatures

Enhancing the energy output of batteries in low temperatures is critical to broadening the application areas of advanced electronic devices, which can be accomplished by utilizing high-voltage cathodes to match lithium metal anode, optimizing electrolyte electrochemical windows and forming stable solid electrolyte interphases to provide facile ion-transmission kinetics at low temperature. Herein, we demonstrate a fluorinated ester co-solvent electrolyte, which applies 1 M LiPF6 in an ethyl 4,4,4-trifluoro butyrate/fluoroethylene carbonate (FEC) (4/1 by volume ratio) that jointly satisfies high voltage cathode and lithium metal anode reversibility at required ambient. The performance of the battery is due to the rapid dissociation of Li+ and the formation of a fluorine-rich inorganic electrolyte interface in the fluorinated solvent. Therefore, the fluorinated ester co-solvent electrolyte system can provide 209.9 mAh g−1, 194.8 mAh g−1, and 175.5 mAh g−1 when discharged at room temperature, −20 ℃ and −40 ℃, respectively, those far exceeds the performance of carbonate electrolytes. This work advances the development of low-temperature lithium metal batteries.

Self-Templated 3D Sulfide-Based Solid Composite Electrolyte for Solid-State Sodium Metal Batteries.

Rechargeable solid-state sodium metal batteries (SSMBs) experience growing attention owing to the increased energy density (vs Na-ion batteries) and cost-effective materials. Inorganic sulfide-based Na-ion conductors also possess significant potential as promising solid electrolytes (SEs) in SSMBs. Nevertheless, due to the highly reactive Na metal, poor interface compatibility is the biggest obstacle for inorganic sulfide solid electrolytes such as Na3SbS4 to achieve high performance in SSMBs. To address such electrochemical instability at the interface, new design of sulfide SE nanostructures and interface engineering are highly essential. In this work, a facile and straightforward approach is reported to prepare 3D sulfide-based solid composite electrolytes (SCEs), which utilize porous Na3SbS4 (NSS) as a self-templated framework and fill with a phase transition polymer. The 3D structured SCEs display obviously improved interface stability toward Na metal than pristine sulfide. The assembled SSMBs (with TiS2 or FeS2 as cathodes) deliver outstanding electrochemical cycling performance. Moreover, the cycling of high-voltage oxide cathode Na0.67Ni0.33Mn0.67O2 (NNMO) is also demonstrated in SSMBs using 3D sulfide-based SCEs. This study presents a novel design on the self-templated nanostructure of SCEs, paving the way for the advancement of high-energy sodium metal batteries.

Bifunctional Fluorocarbon Electrode Additive Lowers the Salt Dependence of Aqueous Electrolytes.

The solid electrolyte interphase (SEI) plays a crucial role in extending the life of aqueous batteries. The traditional anion-derived SEI formation in aqueous electrolytes highly depends on high-concentrated organic fluorinating salts, resulting in low forming efficiency and long-term consumption. In response, this study proposes a bifunctional fluorocarbon electrode additive (BFEA) that enables electrochemical pre-reduction instead of TFSI anion to form the LiF-rich SEI and in situ produce conductive graphite inside the anode before the lithiation. The BFEA lowers the salt dependence of aqueous electrolytes, enabling the inorganic LiCl electrolyte to work first, but also successfully achieves a high SEI formation efficiency in the relatively low 10m LiTFSI without mass transfer concerns, suppressing the parasitic hydrogen evolution from 11.24 to 4.35nmol min-1. Besides, BFEA strengthens the intrinsic superiority of Li storage reaction by lowering battery polarization resulting from the in situ production of graphite, promoting charge transfer of electrode kinetics. Compared with the control group, the demonstrated Ah-level pouch cell employing BFEA exhibits better cycle stability above 300 cycles with higher capacity retention of 78.2% and the lower decay of the round-trip efficiency (△RTE = 2%), benefiting for maintaining the high efficiency and reducing heat accumulation in large-scale electric energy storage.

Recent research progress on Li29Zr9Nb3O40-based solid electrolytes for lithium batteries

All-solid-state batteries have become a research hotspot because of their high specific capacity and safety. Solid-state electrolytes are the key material of all-solid-state lithium-ion batteries, and their properties directly affect the overall performance of lithium-ion batteries. So far, many inorganic solid electrolytes have been reported, such as NASICON, LISICON, perovskite, and garnet-type solid electrolyte. However, some lithium-rich rock salt-structured electrolytes, such as Li2ZrO3, LiNbO4, and Li6Zr2O7, have been underappreciated in the field of solid-state electrolytes due to their lower ionic conductivity at room temperature. While investigating solid solution formation, Li6Zr[Formula: see text][Formula: see text]Nb[Formula: see text]O[Formula: see text][Formula: see text][Formula: see text], a new phase known as Li[Formula: see text]Zr9Nb3O[Formula: see text] with a rock-salt structure was discovered. After decades, it was not until a team prepared Li[Formula: see text]Zr9Nb3O[Formula: see text] ceramics by sol-gel method, which exhibited high ionic conductivity (10[Formula: see text]–10[Formula: see text]S cm[Formula: see text]) at room temperature, that the substance showed great potential as a solid electrolyte in all-solid-state lithium-ion batteries. In this paper, the crystal structure, lithium-ion transport mechanism, preparation method, and element doping of Li[Formula: see text]Zr9Nb3O[Formula: see text] are described comprehensively based on research progress in recent years. Then, development prospects and challenges of the concrete application of Li[Formula: see text]Zr9Nb3O[Formula: see text]in all-solid-state lithium-ion batteries are also discussed.

Enhancing the Filler Utilization of Composite Gel Electrolytes via In Situ Solution-Processable Method for Sustainable Sodium-Ion Batteries.

The composite gel electrolyte (CGE), which combines the advantages of inorganic solid-state electrolytes and solid polymer electrolytes, is regarded as the ultimate candidate for constructing batteries with high safety and superior electrode-electrolyte interface contact. However, the ubiquitous agglomeration of nanofillers results in low filler utilization, which seriously reduces structural uniformity and ion transport efficiency, thus restricting the development of consistent and durable batteries. Herein, a solution-processable method to in situ construct CGE with high filler utilization is introduced. The homogeneous metal-organic framework fillers contribute to uniform ionic and electronic filed distribution, realizing a stable electrode-electrolyte interface. Consequently, the CGE with high filler utilization achieves an ultra-long lifespan of 10000 cycles with a capacity retention of 80.2%. This work provides guidance for constructing high-performance CGEs in electrochemical energy-storage devices.

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.

MXene Electrodes for All Strain-Free Solid-State Batteries.

All-solid-state batteries with nonflammable inorganic solid electrolytes are the key to addressing the safety issues of lithium-ion batteries with flammable organic liquid electrolytes. However, conventional electrode materials suffer from substantial volume changes during Li+ (de)intercalation, leading to mechanical failure of interfaces between electrode materials and solid electrolytes and then severe performance degradation. In this study, we report strain-free charge storage via the interfaces between transition metal carbides (MXenes) and solid electrolytes, where MXene shows negligible structural changes during Li+ (de)intercalation. Operando scanning electron transmission microscopy with electron energy-loss spectroscopy reveals the pillar effect of trapped Li+ in the interlayer spaces of MXene to achieve the strain-free features. An all strain-free solid-state battery, which consists of a strain-free Ti3C2Tx negative electrode and a strain-free disordered rocksalt Li8/7Ti2/7V4/7O2 positive electrode, demonstrates long-term stable operation while preserving the interfacial contact between electrode materials and solid electrolytes.

Revealing the Failure Mechanisms of Lithium Metal Solid‐State Batteries with Solid Inorganic Electrolytes by In situ Electron Microscopy

Lithium metal solid‐state batteries (LMSSBs) are considered to be one of the ultimate choices for future energy storage systems because of their high theoretical energy density and enhanced safety. However, the development of LMSSBs has been seriously hindered by some practical issues, such as Li dendrite penetration in the solid‐state electrolytes (SSEs) and uncontrolled interphase growth at the Li/SSE interface, which can cause severe battery degradation, failure, and even safety hazards. To construct safe high‐performance LMSSBs, it is crucial to gain an in‐depth understanding of the failure mechanisms induced by these challenges, especially through direct visualization of the failure processes. In this review, the recent progress on the mechanistic study of LMSSBs by in situ electron microscopy is summarized. In situ transmission electron microscopy (TEM) and scanning electron microscopy (SEM) offer an opportunity to probe the battery failure mechanism by observing the associated physical and chemical processes at nano/atomic resolution. The failure causes of Li dendrites growth and interphase formation are classified and discussed, followed by the corresponding solutions to address these issues. Additionally, the emerging perspectives on future research directions in this field are also summarized.

Covalent Organic Frameworks Interfacial Modification of Ceramic Electrolytes for Enhanced Electrochemical Performance

AbstractThe interface instability between inorganic ceramic electrolytes and lithium metal anodes seriously affects the cycling behavior of high‐performance lithium‐metal batteries. Herein, an in situ interfacial modification strategy is proposed to build the precise hybrid organic/inorganic lithium‐ion conducting layer where the Li1.3Al0.3Ti1.7(PO4)3 (LATP) particle surface is anchored by ion‐conducting covalent organic frameworks (COF) with affluent poly(ethylene glycol) (PEG) moieties. This interlayer features ion transport regulation to avoid high interfacial resistance and enhances interfacial stability by building a functional COF‐based shield against electrons. These as‐prepared particles are employed to fabricate flexible quasi‐solid electrolyte membranes interconnected by polytetrafluoroethylene binder based on the dry process. The obtained membranes perform two‐fold increase in ion conductivity at 30 °C of 2.55 × 10−3 S cm−1 and the prolonged lithium deposition up to 1000 h compared to the pristine, which are attributed to synergistic effects in the inorganic/organic phase. Moreover, an integrated cathode/electrolytes design is proposed and exhibits excellent cycling performance with capacity retention of 98.8% after 200 cycles at 1 C. The corresponding pouch cells can light up LED after bending and recovery. This research provides new insights into the great potential of fabricating soft ceramic‐based membranes in a low‐cost and green way for highly‐stable lithium‐metal batteries.

Electrochemical Kinetics of LiFePO4 Cathode Material in Non-flammable Inorganic Liquid Electrolyte.

We unveil the fundamental insights of electrochemical kinetics of LFP cathode material and the passivation layer formation in the SO2-based non-flammable inorganic liquid electrolyte (IE). The influence of temperature and electrochemical potential cutoff in the electrochemical activity of LFP cathode and IE is disclosed. Furthermore, the materials compatibility, structural and chemical stability of LFP in IE is demonstrated using very slow galvanostatic cycling in combination with LiFePO4||Li0.1FePO4 symmetric cells. The lithium storage performance of LFP half-cell using inorganic electrolyte is presented with the optimum voltage window. LFP half-cells exhibit discharge capacities of 147, 111, and 75 mAh/g at 1, 4, 8 C rates, respectively, with coulombic efficiencies of ~99.98 %. The electrochemical behavior and mechanism of LFP||Graphite cell in IE is investigated while concurrently tracking the electrochemical potentials of LFP and Graphite half-cell.

Li3V2(PO4)3 sintering atmosphere optimisation for its integration in all-solid-state batteries

Integration of active materials into the architecture of all-solid-state batteries represents a significant scientific inquiry. Li3V2(PO4)3 (LVP), a positive and negative electrode active material for Li-ion batteries, has been subject to extensive research to elucidate its electrochemical behaviour during cycling processes. However, the comprehensive analysis of its thermal behaviour under different sintering atmosphere conditions has remained underexplored, particularly in the context of its compatibility with solid electrolytes. This study presents a meticulous study of sintering process under different atmospheres with precise control over oxygen partial pressure. Interestingly, we were able to sinter LVP and obtain dense, pure ceramic phase under slightly oxidising atmosphere, characterized by conductivity properties analogous to those observed in samples sintered under Ar/H2 conditions. The findings of this investigation contribute to the understanding of the optimal conditions required for the sintering of LVP, paving the way for the co-sintering of this material with inorganic solid electrolyte unstable under reducing atmosphere, such as LATP.

A self-healing composite solid electrolyte with dynamic three-dimensional inorganic/organic hybrid network for flexible all-solid-state lithium metal batteries

Composite solid electrolytes (CSEs), which combine the advantages of solid polymer electrolytes and inorganic solid electrolytes, are considered to be promising electrolytes for all-solid-state lithium metal batteries. However, the current CSEs suffer from defects such as poor inorganic/organic interface compatibility, lithium dendrite growth, and easy damage of electrolyte membrane, which hinder the practical application of CSEs. Herein, a CSE (PBHL@LLZTO@DDB) with polyurethane (PBHL) as the polymer matrix and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) modified by silane coupling agent (DDB) as inorganic fillers (LLZTO@DDB) has been prepared. Disulfide bond exchange reactions between PBHL and LLZTO@DDB enable PBHL@LLZTO@DDB to form a dynamic three-dimensional (3D) inorganic/organic hybrid network, which promotes the uniform dispersion of LLZTO in PBHL@LLZTO@DDB, improves the Li+ conductivity (1.24 ± 0.08 × 10−4 S cm−1 at 30 ℃), and broadens the electrochemical stability window (5.16 V vs. Li+/Li). Moreover, a combination of hydrogen bonds and disulfide bonds endows PBHL@LLZTO@DDB with excellent self-healing properties. As such, both all-solid-state symmetric and full cells exhibit excellent cycle performance at ambient temperature. More importantly, the healed PBHL@LLZTO@DDB can almost completely restore its original electrochemical properties, indicating its application potential in flexible electronic products.