Electrochemical Stability Research Articles

Stability of sputtered iridium oxide neural microelectrodes under kilohertz frequency pulsed stimulation

Objective. Kilohertz (kHz) frequency stimulation has gained attention as a neuromodulation therapy in spinal cord and in peripheral nerve block applications, mainly for treating chronic pain. Yet, few studies have investigated the effects of high-frequency stimulation on the performance of the electrode materials. In this work, we assess the electrochemical characteristics and stability of sputtered iridium oxide film (SIROF) microelectrodes under kHz frequency pulsed electrical stimulation.Approach. SIROF microelectrodes were subjected to 1.5-10 kHz pulsing at charge densities of 250-1000μC cm-2(25-100 nC phase-1), under monopolar and bipolar configurations, in buffered saline solution. The electrochemical behavior as well as the long-term stability of the pulsed electrodes was evaluated by voltage transient, cyclic voltammetry, and electrochemical impedance spectroscopy measurements.Main results. Electrode polarization was more pronounced at higher stimulation frequencies in both monopolar and bipolar configurations. Bipolar stimulation resulted in an overall higher level of polarization than monopolar stimulation with the same parameters. In all tested pulsing conditions, except one, the maximum cathodal and anodal potential excursions stayed within the water window of iridium oxide (-0.6-0.8 V vs Ag|AgCl). Additionally, these SIROF microelectrodes showed little or no changes in the electrochemical performance under continuous current pulsing at frequencies up to 10 kHz for more than 109pulses.Significance. Our results suggest that 10 000μm2SIROF microelectrodes can deliver high-frequency neural stimulation up to 10 kHz in buffered saline at charge densities between 250 and 1000μC cm-2(25-100 nC phase-1).

Synergetic effect driven LaMnO3@NiO composite based high energy semi-solid supercapacitor

Perovskite materials have gained substantial attention in last two decades as electrode materials for energy storage devices due to low cost, good electrochemical stability, mixed ionic-electronic conductivity, long-term stability, and environmentally friendly. We demonstrate the hybridization of lanthanum manganite (LaMnO3) and Nickel oxide (NiO) composite electrodes for supercapacitor application prepared via sol-gel assisted hydrothermal method. The structural, morphological, surface area, and elemental analysis has been done by X-ray diffraction, Field emission scanning electron microscopy, Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS) analysis. The structural, and morphological analysis confirmed the composite formation. The electrochemical properties have been examined by cyclic voltammetry, galvanostatic charge-discharge, and impedance analysis. The resulting LaMnO3/NiO composite material exhibits enhanced electrochemical performance compared to the individual components. The composite exhibits a specific capacitance of up to 170 F/g at a scan rate of 10 mV/s, which is higher than that of individual LaMnO3 or NiO materials. The composite also demonstrates desirable cycling stability, with a capacity retention of 76 % after 5000 cycles. These results advocate that the LaMnO3/NiO composite is a promising material for high-energy supercapacitor applications. Further performance of the nano-composite was evaluated by LED testing. Three symmetric SCs of the composite linked in series were able to glow a green, red, blue LED for about 1 min and a panel of 26 red LED was illuminated for about 12 min. These findings suggested that the obtained composite material is an exceptional electrode with huge potential for potential for supercapacitor application.

Exploring the Formulation and Efficacy of Phosphazene-Based Flame Retardants for Conventional Supercapacitor Electrolytes.

The formulation of safe electrolytes for supercapacitors based on phosphazene used as a flame-retardant (FR) is carried out. 3 molecules are used: hexafluorocyclotriphosphazene (FR1), (ethoxy)pentafluorocyclotriphosphazene (FR2) and pentafluoro(phenoxy)cyclotriphosphazene (FR3). A comparative study on the efficacy from a safety point of view is performed to determine the minimum percentages of each to be used in a conventional acetonitrile (ACN)/1.0 M tetraethylammonium tetrafluoroborate (Et4NBF4) electrolyte to make it non-flammable. Flammability tests have shown that 5%FR1, 15%FR2 or 20%FR3 are required to do that. The FTIR coupled to the TGA as well as the measurements of surface tensions and contact angles showed that the FRs tend to protect the surface of the electrolyte. The transport properties always remain good, superior to PC/1.0 M Et4NBF4 for example, and the electrochemical stability windows determined in 3-electrode cells with platinum or activated carbon are at least 2.5 V. The cycling performances are also interesting because the AC|AC EDLCs made in this study are compatible with these FRs, which makes it possible to operate devices providing energies and powers of 23.0 Wh.kg-1 and 3.7 kW.kg-1 with the electrolytes based on FR1 or FR2 between 0 and 2.5 V.

Ordered Pt3Ni intermetallic compound: A high-performance oxygen reduction reaction catalyst for Zn-air batteries

The development of advanced catalysts for oxygen reduction reaction (ORR) is crucial for Zinc-air batteries (ZABs). In this study, we focus on the controlled synthesis of ordered Pt3Ni intermetallic compounds through impregnation and high-temperature annealing, aiming to enhance the ORR performance for ZABs. The ordered Pt3Ni (denoted as Pt3Ni) and conventional alloy Pt3Ni (denoted as A-Pt3Ni) are synthesized at 600 ℃ and 200 ℃, respectively. Detailed structural characterizations confirm the formation of both ordered and disordered structures. Pt3Ni demonstrates superior ORR catalytic activity and stability compared to A-Pt3Ni and commercial Pt/C catalyst, as evidenced by higher half-wave potentials, lower Tafel slopes, and enhanced electrochemical stability. Furthermore, Pt3Ni exhibits exceptional performance in ZABs, with higher power density, specific capacity, and longer cycle life than its counterparts. These findings highlight the potential of ordered Pt3Ni intermetallic compounds as efficient ORR catalysts in ZABs, offering a promising route for the development of advanced energy conversion and storage systems.

Iron Doping of 2D Nickel-Based Metal-Organic Frameworks Enhances the Lattice Heterogeneous Interface Coupling Effect for Improved Electrocatalytic Oxygen Evolution.

The coupling of lattice and heterostructure interfaces represents an effective strategy for disrupting the so-called scalar relationship and accelerating reactions involving multiple intermediates. In view of this, a lattice-heterostructure interfacial catalyst consisting of a crystalline Fe/Ni bimetallic MOF and amorphous Fe-MOF was designed in this paper for high-performance alkaline oxygen evolution reaction electrocatalysis. The strongly coupled lattice-heterostructure interface induces a unique synergistic effect that promotes electron transfer of the catalyst. The resulting catalyst exhibits exceptionally high catalytic activity for the oxygen evolution reaction in alkaline media, the Ni9Fe1-BDC-1@Fe-MOF coated on a glassy carbon electrode has an overpotential of 257 mV at a current density of 10 mA cm-2. Furthermore, this catalyst demonstrates a high electrochemical stability. These research results highlight the superiority of lattice-heterostructure interfaces in the development of advanced catalysts.

Imidazolium-Based Ionic Liquid Electrolytes for Fluoride Ion Batteries.

The fluoride-ion battery (FIB) is a post-lithium anionic battery that utilizes the fluoride-ion shuttle, achieving high theoretical energy densities of up to 1393 Wh L-1 without relying on critical minerals. However, developing liquid electrolytes for FIBs has proven arduous due to the low solubility of fluoride salts and the chemical reactivity of the fluoride ion. By introducing a chemically stable electrolyte based on 1,3-dimethylimidazolium [MMIm] bis(trifluoromethanesulfonyl)imide [TFSI] and tetramethylammonium fluoride (TMAF), we achieve an electrochemical stability window (ESW) of 4.65 V, ionic conductivity of 9.53 mS cm -1, and a solubility of 0.67 m. The origin of this high solubility and the solvation structure were investigated using NMR spectroscopy and neutron total scattering, showing a fluoride solvation driven by strong electrostatic interactions and weak hydrogen bonding without covalent H-F character. This indicates the chemical stability of 1,3-dimethylimidazolium toward the fluoride ion and its potential as an electrolyte for high-voltage FIBs.

Optimizing Oxygen Redox Activity by Local Chemical Disorder toward Robust Co-Free Li-Rich Cathode with High Voltage Stability.

Despite extensive investigation on the lattice oxygen redox (LOR) in Li-rich cathodes, significant challenges remain in utilizing LOR activity without compromising structural and electrochemical stability. Related breakthroughs are hindered by the lack of understanding regarding how different LOR activity influences the structural evolution and electrochemical stability, and what is the optimal LOR activity. Herein, the degree of LOR activity is successfully regulated from 22% to 92% in Co-free Li-rich cathodes (Li1+xMn0.62Ni0.18O2) by controlling local chemical disorder, and the relationship between LOR activity and cycling stability is revealed. Conventional consensus is challenged by new findings that the over-suppressive LOR activity also undermines electrochemical/structural stability, and even causes more severe voltage fading compared to cases with excessive LOR. However, their failure mechanisms related to lattice strain present different characteristics. Based on the established understanding, the appropriate LOR activation is necessary to balance the maximum reversible LOR activity and good stability, and the optimal degree is identified as 86% in Li1.18Mn0.62Ni0.18O2 (LR-78). LR-78 exhibits remarkable voltage retention of 96% after 400 cycles at 1 C, and superior high-rate cyclability without capacity decay within 600 cycles at 5 C. These findings significantly broaden the understanding of LOR mechanisms and provide critical guidance for designing durable LOR-based cathodes.

Incorporating MXene with Redox Carriers on Capacitive Carbon Cloth-Based Freestanding Electrodes for Power Applications

Abstract Battery-like organic materials including quinone-based electrodes with electrochemical activity have been extensively investigated for their use as electrode materials in energy storage devices due to their economic competitiveness and sustainable benefits. However, the intrinsic electrical insulating nature of organic quinones and their electrochemical reactivity limit power capability and stability upon charge/discharge cycling, respectively. Here, we report the preparation of a concentric layered architecture, MXene/Anthraquinone/Carbon Cloth (M/AQ/CC), by physisorption of anthraquinone onto the surface of carbon cloth via non-covalent π–π interactions, followed by dipping in exfoliated MXene suspension. The M/AQ/CC electrode, with a high mass loading (18.2 mg cm-2), delivered a capacity of 46 mAh g-1 (about 1 mAh cm-2 areal capacity or 6 mAh mL-1 volume) at 0.5 A g-1, with good rate performance and an enhanced cyclability over 5k cycles. This simple preparation method can also be applied to incorporate MXene with a series of alternative organic redox carriers on freestanding carbon cloth, including thionin acetate and anthraquinone-2-sulfonate. The improvement in electrochemical performance highlights an efficient approach to store more charges via redox reactions from organic quinones pi-stacked at carbon surfaces, thanks to a protective MXene shield that stabilizes the Faradaic behavior of quinones over repetitive charge-discharge processes. The simplicity and versatility of this method should enable design of many advanced electrode materials based on MXene/quinones/carbon cloth for power devices

Cold Sintering Halide-in-Oxide Composite Solid-State Electrolytes with Enhanced Ionic Conductivity.

All-solid-state batteries (ASSBs) have attracted increasing attention for next-generation electrochemical energy storage due to their high energy density and enhanced safety, achieved through the use of nonflammable solid-state electrolytes (SSEs). Oxide-based SSEs, such as Li1.3Al0.3Ti1.7(PO4)3 (LATP), are notable for their high ionic conductivity and excellent chemical and electrochemical oxidation stability. Nevertheless, their brittle mechanical properties and poor interface contact with electrode materials necessitate high-temperature and long-duration sintering or postcalcination processes, limiting their processability for real-world applications. Additionally, the formation of secondary phases can detrimentally affect the ionic conductivity of LATP electrolytes. Emerging halide-based SSEs offer reliable deformation for practical processing while maintaining high ionic conductivity. In this work, we report a transient liquid-assisted cold sintering process to integrate oxide-based LATP as the matrix and halide-based Li3InCl6 as the conductive boundary phase into a halide-in-oxide ceramic composite electrolyte at a low processing temperature of 150 °C. This composite structure significantly reduces interface resistance, effectively addressing ion-transport depletion across the boundaries between LATP particles. Consequently, the cosintered LATP-Li3InCl6 composite SSE exhibits a high ionic conductivity of 1.4 × 10-4 S cm-1 at ambient temperature. Furthermore, the symmetric Li|LATP-Li3InCl6·nDMF|Li cell demonstrates stable stripping and plating processes for 1600 h at 55 °C (0.1 mA cm-2) and 1200 h at 100 °C (1 mA cm-2). This work represents the first demonstration of halide-oxide ceramic composite SSEs that combine the advantages of oxides and halides for high-performance SSBs.

Versatile Biopolymers for Advanced Lithium and Zinc Metal Batteries.

Lithium (Li) and zinc (Zn) metals are emerging as promising anode materials for next-generation rechargeable metal batteries due to their excellent electronic conductivity and high theoretical capacities. However, issues such as uneven metal ion deposition and uncontrolled dendrite growth result in poor electrochemical stability, limited cycle life, and rapid capacity decay. Biopolymers, recognized for their abundance, cost-effectiveness, biodegradability, tunable structures, and adjustable properties, offer a compelling solution to these challenges. This review systematically and comprehensively examines biopolymers and their protective mechanisms for Li and Zn metal anodes. It begins with an overview of biopolymers, detailing key types, their structures, and properties. The review then explores recent advancements in the application of biopolymers as artificial solid electrolyte interphases, electrolyte additives, separators, and solid-state electrolytes, emphasizing how their structural properties enhance protection mechanisms and improve electrochemical performance. Finally, perspectives on current challenges and future research directions in this evolving field are provided.

Cyanoethyl cellulose-enabled cathodes with interpenetrating electron transport and ion transport paths via phase inversion method for high energy density lithium metal batteries

Binders need to exhibit high bonding strength, sufficient mechanical properties, and electrolyte insolubility to help achieve uniform and stable porous structure and conductive network in electrode composites. Traditional binders like polyvinylidene fluoride offer good electrochemical stability but suffer from poor adhesion performance and weak mechanical flexibility, resulting in unstable electrode structures. To address these issues, a cyanoethyl cellulose-based binder was used to prepare a cyanoethyl cellulose-based cathodes with interpenetrating electron transport and ion transport paths via phase inversion method for high energy density lithium metal batteries. The polar groups (CN, C-O-C, and –OH) on the cyanoethyl cellulose chains could promote the transport of Li-ions through electrostatic interactions. The interpenetrating electron transport and ion transport paths enabled fast Li-ion and electron transport in the cyanoethyl cellulose-based cathodes, resulting in a higher Li-ion diffusion coefficient of to 3.74 × 10−10 cm2·s−1. Hence, the cyanoethyl cellulose-based cathodes enabled batteries with an energy density of 419.8 Wh·kgcathode−1 (mass loading of 16.6 mg·cm−2). This study provided a new strategy to achieve uniform and stable porous structure and conductive network in electrode composites high energy density batteries.

Electrifying energy storage by investigating the electrochemical behavior of CoCr2O4/graphene-oxide nanocomposite as supercapacitor high performance electrode material

This study reports novel three-step electrochemical fabrication of CoCr2O4/graphene-oxide nanocomposite on glassy carbon electrode including sequential synthesis of graphene-oxide using modified Hummer's method, CoCr2O4 nanoparticles using sol-gel method and the cost-effective co-precipitation technique for nanocomposite formation. The resulting nanocomposite was subjected to comprehensive analytical and morphological analysis. X-ray diffractometry (XRD) confirms nanocomposite formation with reduced average crystallite size value of 26.9 nm whereas SEM indicates spherical grains existence within nanocomposite. Energy-dispersive X-ray spectrometry (EDS) confirms no impurity peak existence whereas Raman spectroscopy clearly indicated D and G band existence at 1345 and 1587 cm−1 respectively. Photoluminescent spectra reveals decreasing trend in band gap value about 3.49 eV. The electrochemical properties of CoCr2O4/graphene-oxide nanocomposite electrode explored, showcasing remarkable capacitance with a surface area of merely 0.068 cm2, 574.8 F/g specific capacitance in alkaline 1M KOH and 488.6 F/g specific capacitance in acidic 0.1M H2SO4 electrolyte. Moreover, synthesized nanocomposite demonstrates remarkable electrochemical stability resulting capacitance retention about 95 % after 100 cycles in 1M KOH electrolyte. GCD analysis reveals impressive power and energy density values of 2489 W/kg and 14.88 Wh/kg respectively. These outstanding properties make the nanocomposite an attractive material for next-generation supercapacitors and energy storage solutions.

A Boat-Paddle-Like Molecule Binder with Twining-Blocked and Ultrafast Self-Healing Functionalities for Stable Silicon Anodes.

Self-healing binder is a prospective and efficient strategy to alleviate volume expansion of silicon (Si) anodes. However, excellent mechanical strength and healing ability tend to be mutually exclusive, due to enhanced tensile stress limit by twining polymer chains, while inhibiting polymer diffusion rate and inducing healing failure by blocked chains. Herein, inspired by the planning course of boat and paddles, a novel self-healing binder (PVA-4FBA-PEI) is designed and synthesized with mobile parallel structure and twining-blocked characteristics. The boat-like intermediate (4-formylphenyl) boronic acid (4FBA) blocks entanglement of poly(vinyl alcohol) (PVA) and poly(ethyleneimine) (PEI) chains, where two parallel chains as paddles can simultaneously form to ensure rapid diffusion of chains during bond breakage. Remarkably, it endows dynamic synergistic covalent bonds via C═N and B─O─C junctions within 4FBA, providing the binder with an ultrafast self-healing time of merely 2 min. Moreover, the binder integrates superior plasticity and flexibility of each chain, showing a high tensile strength (14.4 MPa) and stretchability (1163%) among state-of-the-art polymer binders, thus significantly improving structural integrity and electrochemical stability of Si anode during cycling. This work proposes a dynamic reversible structure via figurative molecular coordination, affording a rational viewpoint on synergetic functionalities of polymer binders for Si anodes.

Multiple hydrogen bonding induced by semi-interpenetrating polymer network binder to enhance the electrochemical performance of sodium-ion batteries electrodes

Molybdenum disulfide (MoS2) serves as an ideal anode for sodium-ion batteries (SIBs), boasting a high theoretical specific capacity and large interlayer spacing. However, the substantial volume change and low conductivity present significant challenges in maintaining the electrochemical stability of the electrode. Herein, a novel semi-interpenetrating polymer network (SIPN) binder (sodium alginate-g-poly (acrylamide-co-2-hydroxyethyl acrylate)-boric acid, SA-PAHB) is synthesized by free radical copolymerization grafting and the multiple hydrogen bonding crosslinking (bond energies spanning from − 33.89 to − 45.49 kcal/mol by theoretical calculations), which can effectively mitigate stress in Na+ deintercalation in MoS2 anodes under the synergy of the unique structure of the SIPN, maintaining electrode stability. Simultaneously, the variable hydrogen bonding crosslinking and abundant –NH2 groups greatly facilitate Na+ diffusion and enhance kinetic performance. Leveraging the advantages of SA-PAHB, the electrochemical performance is significantly enhanced compared to traditional SA and grafted SA-based binders. Specifically, MoS2 anodes using SA-PAHB binder exhibit an initial discharge specific capacity of 772.1 mAh/g at 0.1 A/g and retain 511.2 mAh/g at 0.5 A/g after 200 cycles, with no capacity loss. Additionally, an outstanding rate performance is achieved, delivering 378.5 mAh/g at 10 A/g. For sodium-ion coin full-cells, a discharge specific capacity of 125.2 mAh/g is maintained at 0.5 A/g after 50 cycles.

Enhanced electrochemical stability of poly(pyridylthiophene) with zirconium dioxide/zirconium disulphide nanocomposites for high-performance supercapacitors

Zirconium dioxide (ZrO2) and zirconium disulphide (ZrS2) nanoparticles were added to poly(pyridylthiophene) (PPT) to improve its electrochemical stability. Characterization and comparison with pristine PPT were conducted to understand the surface influence, crystalline structure, and electrochemical performance of the PPT/ZrO2/ZrS2 material. Without reducing its available specific capacitance, surface modification can increase PPT’s structural stability. Through the use of AC impedance and cyclic voltammetry (CV) methods in a 3 M KOH electrolyte, the electrochemical characteristics of the produced PPT/ZrO2/ZrS2 electrode were assessed. PPT, PPT/ZrO2, PPT/ZrS2, and PPT/ZrO2/ZrS2 each had specific capacitances of 265, 655, 747, and 1326F/g at 5 A/g. The Zr4+ ions’ synergistic impact in the PPT/ZrO2/ZrS2 electrode material is responsible for this improvement. The energy and power density of the PPT/ZrO2/ZrS2 electrode in KOH are 166 Wh kg−1 and 664 W kg−1, respectively. After 10,000 cycles, the capacitance only loses 4 % of its initial value. The resulting PPT/ZrO2/ZrS2 nanocomposite included multilayer structures that were extremely stable and porous. The PPT/ZrO2/ZrS2 nanocomposites perform well electrochemically and structurally, making them suitable materials for use in supercapacitors.

Entropy-engineered perovskite cathodes: A novel approach for efficient and durable CO2 electrolysis

The application of solid oxide electrolysis cells (SOECs) for high-temperature CO2 reduction reaction (CO2RR) is constrained by the electrochemical activity and stability of the cathode materials. In this study, a series of iron-based perovskite oxides, designed by systematically varying A-site configurational entropy, are investigated as cathode materials for the CO2RR. Experimental results reveal that these high-entropy materials, derived from La1/2Sr1/2FeO3−δ (LSF), exhibit high electrocatalytic activity and durability. Notably, the SOEC with La1/5Sr1/5Pr1/5Ba1/5Ca1/5FeO3-δ (LSPBCF) cathode achieves a remarkable current density of 2.14 A cm−2 at 800 °C and 1.5 V, maintaining excellent stability over 120 h of operation with negligible fluctuations. Density functional theory (DFT) calculations further unveil the electronic structure modulation mechanism of the high-entropy material, revealing that A-site entropy engineering could enhance CO2 adsorption and activation by reducing the oxygen vacancy formation energy. This study underscores the potential of entropy engineering to improve the electrocatalytic performance and stability of other energy conversion systems.

Understanding the Mechanism of Evaporation-Induced Islands during the Formation of Catalyst Layers and Their Influence on the Alkaline Oxidation Evolution Reaction

Advancements in anode development substantially reduce the cost and enhance the performance of water electrolysis. The strategic configuration of nano-sized catalyst materials on anode supports is a pivotal factor in the expansion of the production of catalyst layers and has a significant influence on their electrochemical performance [1–3]. Therefore, it is essential to understand the structure formation mechanisms during electrode fabrication. This contribution aims to explore the inherent drying mechanisms in the coating process and their subsequent influence on the morphological evolution of anodes, ultimately establishing a linkage between these morphological changes and electrochemical performance and stability metrics. The initial phase of the study involved a detailed characterization of commercial nickel cobalt oxide nanoparticles via advanced analytical techniques, including transmission electron microscopy and energy-dispersive X-ray spectroscopy [4]. Subsequently, a stable ink was formulated by dispersing the catalyst alongside a binder in a solvent, which was then uniformly applied to a conductive nickel plate utilizing an ultrasonic spray coater. Prior to application, the catalyst inks underwent optimization based on the Hansen solubility parameters of catalyst materials [5, 6] and subsequent visualization of their stability and dispersibility characteristics through transmittogram analysis [7]. The drying process of the coating was conducted at two distinct temperatures, 50 °C and 150 °C, to investigate the effect of temperature on solvent evaporation. Morphological and structural analyses of the anodes were subsequently performed using scanning electron microscopy (SEM), laser scanning microscopy (LSM), and atomic force microscopy (AFM), providing insight into the alterations induced by the drying process. The analyses conducted in this study elucidate significant modifications in the morphology of the layer structures attributable to variations in drying temperatures as illustrated in Figure 1. Specifically, lower temperature resulted in reduced evaporation rates that facilitated the formation of larger, isolated regions/islands on the anode support. These are indicative of a non-uniform coating distribution. In contrast, a higher temperature promoted rapid evaporation, resulting in a quite homogeneous distribution of smaller islands accompanied by the emergence of voids within the anode layer. Electrochemical analysis revealed that these morphological changes are of vital importance: they govern the wetting behaviour and the dynamics of bubble formation which are important for the electrochemical performance and durability of the catalyst layers. Moreover, the insights gleaned from this study are instrumental in identifying optimal configurations of catalyst layer structures, i.e., features that should be maintained during scale-up. In conclusion, this study significantly advances the field by revealing novel principles governing the design and optimization of electrode structures for the oxygen evolution reaction. In particular, the complicated relationship between drying temperatures and morphological evolution, which significantly influences electrochemical performance is explained.

Shielding Fluoride Ion Basicity through Diurea Coordination for Nonaqueous Fluoride Shuttle Batteries.

The strong basicity of fluoride ions leads to detrimental nucleophilic attack on organic components in the electrolytes, such as β-hydrogen elimination reactions with organic cations and solvents, converting "naked" F- into corrosive and unstable bifluoride (HF2-) ions. These reactions significantly constrain the choice of suitable solvents and salts to develop electro(chemical) stable fluoride ion electrolytes. In this work, we replaced the triple water ligands typically present in industrialorganic fluoride salts with dual 1,3-diphenylurea (DPU) coordination via hydrogen bonding interaction. This modification successfully suppressed the Lewis basicity of fluoride ions, providing long-term chemical stability (over 1000 hours) acrossa wide range of aprotic solvents, a broadened electrochemical stability window (-2.5 ~ 0.9 V vs. Ag+/Ag) and high ionic conductivity (1.7 mS cm-1) at room temperature. Additionally, the weaker hydrogen bonding in F--DPU coordination, compared to the conventional boron-based anion acceptor (AA) strategy that relies on intensive Lewis acid-base interactions, facilitates faster (de)fluorination kineticsat the electrode. The proposed room temperature fluoride ion batteries sustain improved electrochemical performance by pairing with the Pb-PbF2 anode and BiF3 or Ag cathode.

An Amphiphilic Molecule Induced Anion-Enrichment Interface for Next-Generation Lithium Metal Batteries.

The electrolyte engineering enables the fabrication of robust electrode/electrolyte interphase with excellent electrochemical stability for reliable lithium (Li) metal batteries (LMBs). Herein, an amphiphilic molecule nonafluoro-1-butanesulfonate (NFSA) is employed in electrolytes to realize anion-enrichment interfacial design. The functions of such an amphiphilic molecule in the electrolyte and anode/electrolyte interphases of LMBs are elucidated via theoretical and experimental analyses. The polar lithophilic segments (-SO3-) present a capability to solvate Li+, while the perfluoroalkyl chains (-CF2CF2CF2CF3) exhibit a solvent-phobic, which alters the Li+ solvation environment in the electrolyte and thus building a favorable interphase enriched with anion-derived inorganic compositions on Li electrode. As a result, the designed electrolyte enables stable operation of the Li||Cu cells for more than 200 cycles with a cumulative irreversible capacity loss of only 2.4 mAh cm-2, and the long-term cycle life of the Li||Li cells is extended to more than 1500h with a small overpotential (36.5mV). Moreover, prolonged cycle life of the full cell assembled with commercial LiFePO4 cathode (over 80% capacity retention after 500 cycles at 0.5 C) is achieved even under the limiting Li source (≈5 mAh cm-2), high cathode loading (≈12mg cm-2), and lean electrolyte (≈2.5µL mg-1).

Mass Transfer Limitation within Molecular Crowding Electrolyte Reorients Preferential (100) and (101) Texture for Dendrite-Free Zinc Metal Batteries

Aqueous zinc metal batteries have significant potential for use in portable devices and large-scale energy storage systems.1 Nevertheless, the growth of zinc dendrites and parasitic reactions worsen the stability of zinc metal electrodes.2 Therefore, strategies must be found to prevent zinc dendrites and other unfavorable reactions. In this study, we develop a macromolecular crowding electrolyte (MCE) by using polyvinylpyrrolidone (PVP) as a crowding agent. The strong hydrogen bonds between PVP and H2O molecules effectively suppress water activity, resulting in an enlarged electrochemical stability window and wide operating temperatures (−20 to 50 °C). Furthermore, the adsorption of PVP on the electrode surface enables progressive nucleation in the MCE, providing promising reversibility and long-term stability during the zinc plating/stripping process. More importantly, the deep insights into Zn deposition morphology and crystallinity illustrate the crystallographic reorientation into (100) and (101) facets, exhibiting vertical and uniform zinc deposition. Density functional theory calculations confirm that the preferential exposure of crystal facets is due to the adsorption of PVP molecules on the zinc metal surface. Furthermore, the electrochemical tests employing a rotating disc electrode and a three-electrode system demonstrate the notable mass transfer limitation in the MCE, which mainly contributes to the reoriented zinc deposition. The vertical arrangement of deposited zinc is more beneficial than parallel deposition to contact the ions outside the depletion region to overcome mass transfer limitation in the MCE. As a consequence, the preferential zinc deposition by exposing (100) and (101) facets enables Zn/Zn symmetric cells to cycle for over 3000 hours at different current densities. Additionally, Na0.33V2O5/Zn and MnO2/Zn full cell batteries in MCE exhibit favorable cycling stability and capacity across a wide temperature range from −20 to 50 °C. This work unveils a unique approach to reorienting the preferential crystallography of deposited zinc, providing a new direction to regulate and control the favorable orientation of zinc deposition.