Stability Of Electrolyte Research Articles

Insights into polymer electrolyte stability and reaction pathways: A first-principle calculations study.

To identify suitable polymer candidates for electrolytes in solid-state batteries, this study investigates the electrochemical behavior and decomposition pathways of four monomers involving esters, ethers, and carbonates via first-principles calculations. In particular, we determine the oxidation and reduction potentials of these monomers near different ions (Li+, TFSI-, and [Li]+[TFSI]-) and the corresponding reorganization energies. The latter quantity is central to Marcus theory of electron transfer and, therefore, provides additional kinetic information. Our results reveal notable sensitivity of the monomers to reduction in a Li+-rich regime and to oxidation in a TFSI--rich regime. Additionally, the reactivity and decomposition pathways of the monomers were investigated for various electrochemical environments, focusing on the quantification of gaseous and ionic products during the initial stage of formation of interphasial layers. Based on the electrochemical windows and spontaneous Ab initio molecular dynamics calculations, we observe that monomers containing carbonate groups exhibit greater stability against decomposition caused by reduction, especially in different regimes, when compared to monomers with ester and ether groups.

Irreversible oxygen uptake and thermal expansion in the solid electrolyte oxygen-deficient perovskite Ca(Ti0.8Fe0.2)O3−δ

The efficient operation of solid oxide fuel cells for renewable energy generation requires solid electrolytes with high ionic conductivity, thermal stability, and chemical durability. Metal oxide perovskites of the form ABO3 are promising candidates, especially when doped with cations that incorporate interstitial oxygen or oxygen vacancies to enhance ionic conductivity. However, doping can lead to complex and poorly understood crystallographic structures. In this study, we investigate the effects of Fe3+ doping on the orthorhombic Pbnm CaTiO3 perovskite, forming Ca(Ti0.8Fe0.2)O3−δ, and demonstrate the complexity of its phase transitions at operational temperatures. Using synchrotron X-ray diffraction and thermogravimetric analysis, we show that this material undergoes significant oxygen uptake at elevated temperatures, leading to an irreversible expansion of the unit cell and changes in polyhedral coordination upon cooling. These structural modifications are attributed to the partial oxidation of Fe3+ to Fe4+, providing insight into the inconsistencies observed in previous studies of oxygen-deficient perovskites. Our findings highlight the critical role of thermal history and oxygen availability in determining the structural stability and long-term performance of perovskite-based solid electrolytes in solid oxide fuel cells.

Self-Assembled Monolayer in Hybrid Quasi-Solid Electrolyte Enables Boosted Interface Stability and Ion Conduction.

Complex interactions between the inorganic solid electrolyte (ISE) and the liquid electrolyte (LE) give rise to challenges of achieving durable interface stability in hybrid quasi-solid electrolytes (HQSE), and the influence on the involved ISE surface ionic conductivity also needs to be investigated. Here, 4-chlorobenzenesulfonic acid (CBSA) is utilized to establish a self-assembled monolayer (SAM) on the surface of Li6.4La3Zr1.4Ta0.6O12 (LLZTO), which is then incorporated into PEGDA-based in situ polymerized HQSE. The results show that the introduction of CBSA significantly improves the LLZTO/LE interface stability with the optimized solvation structure, resulting in a favorable ionic conductivity (1.19 mS⋅cm-1) and an increasing Li+ transference number (0.647). Mechanisms for the promotion of ionic conduction and interfacial stability of SAM-HQSE are unveiled through the density functional theory (DFT) combined with Raman spectra and 7Li solid-state nuclear-magnetic-resonance. There are no short-circuits in the Li|SAM-HQSE|Li cells after 1000 h. The LFP|SAM-HQSE|Li cells or LFP|SAM-HQSE|Graphite pouch cells respectively achieve the capacity retention of 91.2 % and 87.0 % with the 0.5.C-rate for 500 and 300 cycles. This facile and effective strategy proposed in this work make it accessible for constructing the stable surface micro-environments of LLZTO where boost and homogenize the Li+ conduction in a hybrid quasi-solid electrolyte system.

In Situ Surface-Enhanced Infrared Absorption Spectroscopy to Explore the Stability of Electrolyte in Nonaqueous Lithium Oxygen Batteries

Tetraethylene glycol dimethyl ether (TEGDME) decomposition on the Au electrode surface is studied using in situ attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). Due to the weak solvation of TEGDME, the superoxide intermediate (LiO2/O2−) of the discharge process rapidly gains electrons on the electrode surface to generate Li2O2. Furthermore, alkyl radical, formed by LiO2/O2− extracting hydrogen from ether, undergoes oxidative decomposition reactions to form by-products. During the charge process, amorphous film-like Li2O2 obtained from surface-phase mechanism oxidizes in the low potential range of 3–3.4 V, while the oxidation potential of large-sized crystal Li2O2 particles obtained from solution-phase mechanism is above 3.4 V. Besides, TEGDME is intrinsically unstable and can decompose at 3.8 V even the solution is saturated with argon, indicating that the degradation of ether-based electrolyte is inevitable during the cycling process. This work confirms the feasibility of ATR-SEIRAS in probing the reaction mechanism and electrolyte stability of lithium oxygen batteries, and provides direct spectroscopic evidence for subsequent optimization of electrolyte components.

Eliminating chemo-mechanical degradation of lithium solid-state battery cathodes during >4.5 V cycling using amorphous Nb2O5 coatings.

Lithium solid-state batteries offer improved safety and energy density. However, the limited stability of solid electrolytes (SEs), as well as irreversible structural and chemical changes in the cathode active material, can result in inferior electrochemical performance, particularly during high-voltage cycling (>4.3 V vs Li/Li+). Therefore, new materials and strategies are needed to stabilize the cathode/SE interface and preserve the cathode material structure during high-voltage cycling. Here, we introduce a thin (~5 nm) conformal coating of amorphous Nb2O5 on single-crystal LiNi0.5Mn0.3Co0.2O2 cathode particles using rotary-bed atomic layer deposition (ALD). Full cells with Li4Ti5O12 anodes and Nb2O5-coated cathodes demonstrate a higher initial Coulombic efficiency of 91.6% ± 0.5% compared to 82.2% ± 0.3% for the uncoated samples, along with improved rate capability (10x higher accessible capacity at 2C rate) and remarkable capacity retention during extended cycling (99.4% after 500 cycles at 4.7 V vs Li/Li+). These improvements are associated with reduced cell polarization and interfacial impedance for the coated samples. Post-cycling electron microscopy analysis reveals that the Nb2O5 coating remains intact and prevents the formation of spinel and rock-salt phases, which eliminates intra-particle cracking of the single-crystal cathode material. These findings demonstrate a potential pathway towards stable and high-performance solid-state batteries during high-voltage operation.

Lewis Acid Sites in Hollow Cobalt Phytate Micropolyhedra Promote the Electrocatalytic Water Oxidation.

The acid-base microenvironment of the metal center is crucial for constructing advanced oxygen evolution reaction (OER) electrocatalysts. However, the correlation between acidic site and OER performance remains unclear for cobalt-based catalysts. Herein, Lewis acid sites in hollow cobalt phytate micropolyhedra (M-CoPA, M = Cu, Sr) were synthesized by a cation-exchange strategy, and their OER performances were studied systematically. Experimentally, Lewis acid Cu2+ sites with stronger Lewis acidity exhibited superior intrinsic activity and long-term stability in alkaline electrolytes. The spectroscopic and electrochemical studies show Lewis acid sites in hollow cobalt phytate micropolyhedra can modulate the electronic distribution of the adjacent cobalt center and further optimize the adsorption strength of oxygenated species. This study figures out the effect of Lewis acid sites on the OER kinetics and provides an effective way to develop high-efficiency electrocatalysts for energy conversion systems.

Influence of Chloride and Electrolyte Stability on Passivation Layer Evolution at the Negative Electrode of Mg Batteries Revealed by operando EQCM-D.

Rechargeable magnesium batteries are promising for future energy storage. However, among other challenges, their practical application is hindered by low coulombic efficiencies of magnesium plating and stripping. Fundamental processes such as the formation, structure, and stability of passivation layers and the influence of different electrolyte components on them are still not fully understood. In this work, we gain unique insights into the initial Mg plating and stripping cycles by comparing magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2)- and magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)4]2)-based electrolytes, each with and without MgCl2, on gold electrodes by highly sensitive operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) applying hydrodynamic spectroscopy. With the stable Mg[B(hfip)4]2-based electrolytes, highly efficient and interphase-free cycling is possible and passivation layers are attributed to electrolyte contaminants. These are forming and degrading during the so-called initial conditioning process. With the more reactive Mg(TFSI)2-based electrolyte, thick passivation layers with small pores are growing during cycling. We demonstrate that the addition of chloride lowers the amount of passivated Mg deposits in these electrolytes and accelerates the currentless dissolution of the passivation layer. This has a positive effect since we observe the most efficient cycling and uniform deposition when no interphase is present on the electrode.

Confined Water Dynamics in Topological Networks Hydrogel for Aqueous Electrochemical Devices.

The unique properties of confined water molecules within polymer networks have garnered extensive research interest in energy storage, catalysis, and sensing. Confined water molecules exhibit higher thermodynamic stability compared to free water, which reduces decomposition and evaporation of water in hydrogel electrolyte system. Herein, a facile strategy is developed to limit active water molecules in a hydrogel network via hydrogen bonding within a topological network. The design of this gel enhances hydrogen bonding between the gel network and water molecules, thereby improving stability by constructing interpenetrating networks. Using this design, the topological network gel is selected as the electrolyte for batteries, demonstrating an extended electrochemical window from 2.37V with polyvinyl alcohol gel to 2.96V, indicating superior confinement of water molecules by hydrogen bonds in the topological network. Additionally, batteries and capacitors assembled with the topological gel exhibit high-capacity retention rates of 94.25% after 20000 cycles at a current density of 1.0 A g-1 and 87.63% after 10000 cycles at a current density of 0.5 A g-1, respectively. This study demonstrates the feasibility of using a topological gel design to enhance gel electrolyte stability, offering a promising avenue for future research in regulating topological networks within gels for various applications.

High Configuration Entropy Promises Electrochemical Stability of Chloride Electrolytes for High‐Energy, Long‐Life All‐Solid‐State Batteries

AbstractSolid‐state electrolytes (SSEs) with high ionic conductivity, stability, and interface compatibility are indispensable for high‐energy‐density and long‐life all‐solid‐state batteries (ASSBs), yet there are scarce SSEs with sufficient ionic conductivity and electrochemical stability. In this study, with a high‐entropy SSE (HE‐SSE, Li2.9In0.75Zr0.1Sc0.05Er0.05Y0.05Cl6), we show the high configuration entropy has a thermodynamically positive relationship with the high‐voltage stability. As a result, the ASSBs with HE‐SSE and high‐voltage cathode materials exhibit superior high‐voltage and long‐cycle stability, achieving 250 cycles with 81.4 % capacity retention when charged to 4.8 V (vs. Li+/Li), and even 5000 cycles if charged to 4.6 V (vs. Li+/Li). Experimental characterizations and density functional theory calculations confirm that the HE‐SSE greatly suppresses the high‐voltage degradation of SSE at the interface, promoting the high‐voltage stability coordinately through high entropy and interface stability. The high entropy design offers a general strategy to simultaneously improve the high‐voltage stability and ionic conductivity of SSEs, creating an avenue to building high‐energy and long‐life ASSBs.

High Configuration Entropy Promises Electrochemical Stability of Chloride Electrolytes for High-Energy, Long-Life All-Solid-State Batteries.

Solid-state electrolytes (SSEs) with high ionic conductivity, stability, and interface compatibility are indispensable for high-energy-density and long-life all-solid-state batteries (ASSBs), yet there are scarce SSEs with sufficient ionic conductivity and electrochemical stability. In this study, with a high-entropy SSE (HE-SSE, Li2.9In0.75Zr0.1Sc0.05Er0.05Y0.05Cl6), we show the high configuration entropy has a thermodynamically positive relationship with the high-voltage stability. As a result, the ASSBs with HE-SSE and high-voltage cathode materials exhibit superior high-voltage and long-cycle stability, achieving 250 cycles with 81.4 % capacity retention when charged to 4.8 V (vs. Li+/Li), and even 5000 cycles if charged to 4.6 V (vs. Li+/Li). Experimental characterizations and density functional theory calculations confirm that the HE-SSE greatly suppresses the high-voltage degradation of SSE at the interface, promoting the high-voltage stability coordinately through high entropy and interface stability. The high entropy design offers a general strategy to simultaneously improve the high-voltage stability and ionic conductivity of SSEs, creating an avenue to building high-energy and long-life ASSBs.

Non‐Aqueous Liquid Electrolytes for Li‐O2 Batteries

AbstractLi‐O2 batteries (LOBs) have become a research hotspot of energy storage devices because of its high theoretical energy density. Practical applications require that non‐aqueous LOBs can deliver stable and high reversible capacity, which heavily depends on the appropriate electrolyte system. Therefore, it is very important to select electrolytes that are hard to decompose and conducive to modulating the growth kinetics of discharge products. Herein, we will review the current progress and challenges of non‐aqueous liquid electrolytes for LOBs by analyzing the influence factors on electrolyte stability and introducing the design and modification methods of electrolytes with different solvent types. At last, the possible research tactics have been proposed to develop advanced electrolytes for improving electrochemical performance of LOBs.

High-Na-Content Birnessite via P'3-Stacking with Tunable Active Facets for Advanced Aqueous Sodium-Ion Batteries.

Layered Na-birnessites are promising cathode materials for aqueous sodium-ion batteries due to their high theoretical capacity, low cost, and environmental benignity. However, the general O'3 Na-birnessites possess low Na content and dominant inactive {001} exposed facets, which compromise their Na storage capability and cycling stability. Herein, we develop a high-Na-content P'3-Na0.71MnO2·0.15H2O with highly enriched {010} active facets by a hydrothermal conversion method. In comparison with the O'3 Na-birnessite, the P'3 Na-birnessite with a high ratio of {010}/{001} exposed facets provides greatly increased open channels for Na+ diffusion, while the P'3 stacking affords a lower Na+ diffusion barrier, resulting in improved electrode kinetics with a large specific capacity of 176 mAh g-1 at 0.2 A g-1. More importantly, the P'3 Na-birnessite manifests solo Na+ intercalation/deintercalation with extraordinary cycling stability in an aqueous electrolyte, achieving 90.5% capacity retention after 60,000 cycles. When coupled with the NaTi2(PO4)3 anode, the P'3 Na-birnessite-based full cell delivers both high energy density and long cycle life, demonstrating the potential application in aqueous sodium-ion batteries. This study demonstrates an efficient method to prepare high-Na-content P'3 birnessite with tunable exposed facets and provides important insights into developing highly stable layered cathodes for sustainable aqueous sodium-ion batteries.

1,8-Diazabicyclo[5.4.0]undec-7-ene as Cyclic Ether Electrolyte Polymerization Inhibition for Wide-Temperature-Range High-Rate Lithium-ion Batteries.

1,3-Dioxolane (DOL), with its broad liquid phase temperature window and low Li+-solvent binding energy, stands out as an ideal solvent candidate for the wide-temperature and high-rate electrolytes. Unfortunately, DOL is susceptible to undergo ring-opening polymerization under common lithium salts, which markedly retards the reaction kinetics. This work introduces the organic basic additive 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) to effectively suppress the polymerization, thus achieving compatibility between LiFSI, LiDFOB lithium salts, and DOL. Furthermore, density functional theory (DFT) calculations are utilized to elucidate the underlying mechanisms of DOL polymerization and to clarify how DBU inhibits its polymerization. The resulting electrolyte, devoid of polymer chain formation, forms a weak solvation structure rich in anions, which demonstrates rapid ion transport kinetics in the bulk electrolyte and excellent electrochemical stability at the electrolyte-electrode interfaces (EEIs) simultaneously. When applied to the LiFePO4||graphite full cell, it exhibits exceptional wide-temperature and high-rate performance, with specific capacities reaching 101.2 mAh g -1 at room temperature (20 C), 36.9 mAh g-1 at -40 °C (0.5 C), and 118.0 mAh g-1 at 60 °C (20 C). This study significantly guides the development of wide-temperature, high-rate electrolytes.

Cyclodextrin Metal-Organic Framework Functionalized Carbon Materials with Optimized Interface Electronics and Selective Supramolecular Channels for High-Performance Lithium-Sulfur Batteries.

During the reaction process in lithium-sulfur batteries, Lewis acidic lithium polysulfides (LiPSs) affect ion distribution and overall electrolyte stability, degrading battery performance and product distribution (e.g., Li2S). Here, a microenvironment regulation strategy with optimized interface electronics and selective supramolecular channels, is proposed to enhance LiPS reaction kinetics through Lewis basic γ-cyclodextrin metal-organic framework (γ-CDMOF). To validate this concept, γ-CDMOF is rapidly synthesized on 3D graphene foam (GF) via a microwave-assisted method, resulting in a γ-CDMOF/GF cathode for high-performance Li-S batteries. A range of analytical techniques combined with density functional theory (DFT) calculations confirm that introducing a Lewis basic supramolecular microenvironment mitigates the LiPSs shuttle effect, enhances polysulfide capture, and improves sulfur redox conversion. Additionally, COMSOL simulations reveal that the γ-CDMOF framework and oxygen sites significantly reduce volumetric expansion stress during the LiPS solid-liquid phase transition. Impressively, the γ-CDMOF/GF cathode exhibits exceptional performance, including a high specific capacity (1253.01 mAh g⁻¹ at 0.1C), excellent rate performance (589.68 mAh g⁻¹ at 5C), and long cycle life (over 1200 cycles). This study introduces a new concept of supramolecular microenvironment regulation and interfacial interaction strategy, offering a unique approach for the development of multifunctional electrode materials.

Recent Advancements in the Interfacial Stability of Garnet Solid Electrolytes and Design Strategies for Solid-State Lithium Batteries: A Review

Recent Advancements in the Interfacial Stability of Garnet Solid Electrolytes and Design Strategies for Solid-State Lithium Batteries: A Review

All-solid-state electrochemical marine sensors based on Na3V2(PO4)3@Na4Zr2Si3O12 solid-state reference electrodes

In this study, Na4Zr2Si3O12 (NZS) solid electrolyte was prepared using an elevated-temperature solid-state method. After heating under supercritical conditions (i.e., 400 °C and 40 MPa), the structure and performance stability of the as-fabricated NZS solid electrolyte were evaluated applying scanning electron microscopy (SEM), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). A new all-solid-state reference electrode, combining Na3V2(PO4)3(NVP) with NZS (NVP@NZS), was developed, and its electrochemical properties were investigated. The prepared reference electrode demonstrated steady potential in both simulated seawater and buffer solutions across a range of pH values and different salt solutions. The reference electrode, integrated with an Ir/IrO2 working electrode, was used to construct an all-solid-state potentiometric pH sensor. This sensor demonstrated a strong linear related response when measuring the pH of both aqueous solutions and simulated seawater samples. Additionally, an ion sensor based on anodic stripping voltammetry, constructed with the assembled solid-state reference electrode, a platinum counter electrode, and a gold-mercury working electrode, was utilized to measure Cu2+ and S2− ions in both aqueous solutions and simulated seawater samples. These all-solid-state electrochemical sensors, incorporating the NVP@NZS solid-state reference electrode, demonstrated a small detection threshold, excellent linear correlation (R2 > 0.99), and a broad detection range, making them well-suited for chemical analysis in challenging marine environments.

First‐Principles Molecular Dynamics Study on Reductive Stability of High Concentration Electrolyte on Zn Doped Cu Current Collector Surface

AbstractIn enhancing the lifespan of anode‐free Li metal batteries (AFLMBs), current collector (CC) engineering is crucial for achieving uniform and dendrite‐free lithium deposition. The commonly used copper (Cu) CC is unsatisfactory because of its poor lithiophilicity. Here, we consider Zn doping on the Cu CC surface (Zn−Cu) and explore the reductive stability of a high‐concentration electrolyte (HCE), consisting of 3.6 M Lithium Hexafluorophosphate (LiPF6) salt in a mixture of ethylene carbonate (EC) and diethylcarbonate (DEC), on the Zn−Cu (111) surface (HCE|Zn−Cu) using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. The interfacial reactions in the HCE|Zn−Cu system are compared to those on the pristine Cu (111) surface (HCE|Cu). We have also studied the effect of electron‐rich environments on the decomposition mechanism of the HCE mixture on both the CC surfaces. It is found that the HCE mixture is electrochemically stable on both Cu and Zn−Cu surfaces in a neutral environment. However, under electron‐rich conditions, only one DEC molecule has decomposed upon contact with the Cu CC surface, while the two PF6− anion groups from Li salts have decomposed much faster (within 100 fs) when the HCE mixture interacts with the Zn−Cu surface. Our results indicate that Zn doping suppresses undesirable solvent decomposition and improves the quality of the solid electrolyte interphase (SEI) layer.

Si-doped NASICON-type Li1.4Al0.4Ti1.6(PO4)3 solid electrolytes for enhanced stability and performance of Li-CO2 batteries

Li-CO2 batteries (LCBs) have attracted significant research interest owing to their potential as energy storage devices and their contribution to carbon neutrality. In this study, we synthesized a solid electrolyte using Si-doped Li1.4Al0.4Ti1.6(PO4)3 (LASTP), by incorporating Si into the NASICON-structured LATP. Through Si doping, P in the tetrahedral PO4 units within the NASICON framework is substituted with Si, and bridging oxygen bonds are formed after high-temperature heat treatment The LASTP powder synthesized via a solution-based method exhibited uniform particle size and composition, and the resulting pellet achieved high densification and the formation of interconnected structures. The pellet exhibited an ionic conductivity of approximately 8.8 × 10-4S/cm at 25℃. The LCB utilizing LASTP demonstrated a maximum discharge capacity of 23,887mAh/g and successfully operated for 200 cycles at a current density of 100mA/g with a cut-off capacity of 500mAh/g. The post-cycling analysis of the cathode confirmed the reversible reactions of the LCB. Additionally, comparative post-cycling XPS analysis of LATP and LASTP revealed that Si doping in LASTP mitigated the reduction of Ti4+ to Ti3+, thereby enhancing the chemical stability of the solid electrolyte. Also, the structural stability of the solid electrolyte was enhanced owing to the formation of new bonds, surpassing the cycle performance and full-depth capacity of LCBs using conventional solid electrolytes. The introduction of structurally and chemically stabilized LASTP enabled the realization of long-lasting, high-capacity LCBs.

Wet sulfuration of molybdate and reconstruction regulation of trace Fe doping for oxygen evolution

There is a growing interest in the development of active, durable, and cost-effective electrocatalysts for oxygen evolution reactions (OER). In this study, we synthesized a self-reconstruction iron-doped sulfide-regulated nickel molybdate catalyst using wet chemical sulfuration and electrodeposition techniques. The core-shell nanorods (SC@NMO) were produced through rapid sulfuration. We investigated the effects of sulfur leaching on rapid and extensive electrochemical self-reconstruction. Our approach utilized the phase change of Fe3+ and electrodeposition-induced restructuring to enhance the catalyst's OER activity and stability in an alkaline electrolyte. Notably, iron ions establish a precipitation-dissolution dynamic equilibrium at the interface between the catalyst surface and the electrolyte, which minimizes iron loss and results in a more efficient and stable catalyst. The prepared sample, SC-Fe(Ni)OOH@NMO, demonstrated exceptional oxygen evolution performance and long-term stability in a 1 M KOH solution, achieving an overpotential of only 279 mV at a current density of 100 mA cm−2. It maintained stable operation for 200 h in a high-concentration 6 M KOH solution. The above data prove that this work provides a feasible strategy to enhance the OER catalytic capacity of metal oxides by the two modification methods of co-doping of metal and non-metal and reconstruction.

Investigating the thermal stability and explosion characteristics of electrolytes composed of different ratios of carbonate organic solvents

Investigating the thermal stability and explosion characteristics of electrolytes composed of different ratios of carbonate organic solvents