Electrochemical Stability Window Research Articles

Kinetics Conditioning of (Electro) Chemically Stable Zn Anode with pH Regulation Toward Long-Life Zn-Storage Devices.

The safety, low cost, and high power density of aqueous Zn-based devices (AZDs) appeal to large-scale energy storage. Yet, the presence of hydrogen evolution reaction (HER) and chemical corrosion in the AZDs leads to local OH- concentration increasement and the formation of ZnxSOy(OH)z•nH2O (ZHS) by-products at the Zn/electrolyte interface, causing instability and irreversibility of the Zn-anodes. Here, a strategy is proposed to regulate OH- by introducing a bio-sourced/renewable polypeptide (ɛ-PL) as a pH regulator in electrolyte. The consumption of OH- species is evaluated through in vitro titration and cell in vivo in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy at a macroscopic and molecular level. The introduction of ɛ-PL is found to significantly suppress the formation of ZHS and associated side reactions, and reduce the local coordinated H2O of the Zn2+ solvation shell, widening electrochemical stable window and suppressing OH- generation during HER. As a result, the inclusion of ɛ-PL improves the cycle time of Zn/Zn symmetrical cells from 15 to 225h and enhances the cycle time of aqueous Zn- I2 cells to 1650h compared to those with pristine electrolytes. This work highlights the potential of kinetical OH- regulation for by-product and dendrite-free AZDs.

Printable Single‐Ion Polymer Nanoparticle Electrolytes for Lithium Batteries

New material solutions are searched for the manufacturing and safety of current batteries. Herein, an extrusion printable polymer separator for lithium batteries based on single‐ion polymer electrolytes is presented. The polymer electrolytes are based on methacrylic polymeric nanoparticles (NPs) functionalized with a lithium sulfonamide group combined with different organic plasticizers such as sulfolane and carbonates. The synthesis of the polymer NPs is carried out by emulsion copolymerization of methyl methacrylate and lithium sulfonamide methacrylate in the presence of a crosslinker, resulting in particle sizes of less than 30 nm, as shown by electron microscopy. Then polymer electrolytes are prepared by mixing polymer NPs with varying lithium sulfonamide content and different plasticizers such as carbonates and sulfolane. The polymer electrolytes show ionic conductivities between 2.9 × 10−4 and 2.3 × 10−5 S cm−1 at 85 °C with the highest values for the small‐sized NPs with the highest lithium content. As a proof‐of‐concept application, layer‐by‐layer printing of a sulfolane‐based polymer electrolyte is evaluated via direct ink writing directly onto classic battery electrodes. The electrochemical characterization of the printed solid electrolyte indicates favorable properties, ionic conductivity, lithium transfer number, electrochemical stability window, and cyclability in lithium symmetrical cells, to be used in lithium batteries.

Indolocarbazole‐Based Small Molecule Cathode‐Active Material Exhibiting Double Redox for High‐Voltage Li‐Organic Batteries

Most organic electrode materials (OEMs) for rechargeable batteries employ n‐type redox centers, whose redox potentials are intrinsically limited <3.0 V versus Li+/Li. However, p‐type materials possessing high redox potentials experience low specific capacities because they are capable of only a single redox reaction within the stable electrochemical window of typical electrolytes. Herein, we report 5,11‐diethyl‐5,11‐dihydroindolo[3,2‐b]carbazole (DEICZ) as a novel p‐type OEM, exhibiting stable plateaus at high discharge potentials of 3.44 and 4.09 V versus Li+/Li. Notably, the second redox potential of DEICZ is within the stable electrochemical window. The mechanism of the double redox reaction is investigated using both theoretical calculations and experimental measurements, including density functional theory calculations, ex situ electron spin resonance, and X‐ray photoelectron spectroscopy. Finally, hybridization with single‐walled carbon nanotubes (SWCNT) improves the cycle stability and rate performance of DEICZ owing to the π–π interactions between the SWCNT and co‐planar molecular structure of DEICZ, preventing the dissolution of active materials into the electrolyte. The DEICZ/SWCNT composite electrode maintains 70.4% of its initial specific capacity at 1‐C rate and also exhibits high‐rate capability, even performing well at 100‐C rate. Furthermore, we demonstrate its potential for flexible batteries after applying 1000 bending stresses to the composite electrode.

Tungsten Oxide Coated Liquid Metal Electrodes via Galvanic Replacement as Heavy Metal Ion Sensors.

Gallium liquid metals (LMs) like Galinstan and eutectic Gallium-Indium (EGaIn) have seen increasing applications in heavy metal ion (HMI) sensing, because of their ability to amalgamate with HMIs like lead, their high hydrogen potential, and their stable electrochemical window. Furthermore, coating LM droplets with nanopowders of tungsten oxide (WO) has shown enhancement in HMI sensing owing to intense electrical fields at the nanopowder-liquid-metal interface. However, most LM HMI sensors are droplet based, which show limitations in scalability and the homogeneity of the surface. A scalable approach that can be extended to LM electrodes is therefore highly desirable. In this work, we present, for the first time, WO-Galinstan HMI sensors fabricated via photolithography of a negative cavity, Galinstan brushing inside the cavity, lift-off, and galvanic replacement (GR) in a tungsten salt solution. Successful GR of Galinstan was verified using optical microscopy, SEM, EDX, XPS, and surface roughness measurements of the Galinstan electrodes. The fabricated WO-Galinstan electrodes demonstrated enhanced sensitivity in comparison with electrodes structured from pure Galinstan and detected lead at concentrations down to 0.1 mmol·L-1. This work paves the way for a new class of HMI sensors using GR of WO-Galinstan electrodes, with applications in microfluidics and MEMS for a toxic-free environment.

Unconventional PEO-PPC quasi-solid state blend polymer electrolyte for high efficiency solid-state Li-metal batteries

Polymer electrolytes represent a safer alternative over traditional liquid electrolytes, enabling the use of higher energy density active materials as electrodes for batteries. Among the wide variety of different polymeric matrix that are currently been proposed, polyethylene oxide (PEO) is considered one of the most promising. In this work, a PEO-based quasi-solid polymer electrolyte (QSPE) was produced by easily scalable solution casting technique, optimized with addition of plasticizers and blended with polypropylene carbonate (PPC). The resulting polymer electrolyte was ultimately supported to glass fiber separator. Improvement of ionic conductivity, transfer number and electrochemical stability window of the different formulations was confirmed through electrochemical impedance spectroscopy and linear sweep voltammetry. Plating and stripping tests in symmetric LiLi cells and charge–discharge tests in half-cell configuration (Li vs LFP) were performed to evaluate the cyclability and stability of the QSPEs. The PEO-PPC polymer electrolyte showed improved efficiency and stability during charge–discharge cycles, at room temperature, suggesting the positive effect of the presence of carbonate groups in the polymer matrix. The promising results demonstrate that the as-prepared QSPE could represent a feasible and viable alternative to conventional liquid electrolytes and could accelerate the adoption of high energy density storage systems, like Li-metal batteries.

MXene nanofiller doped ion conducting polyethylene oxide for electrochemical devices

AbstractNanofiller‐doped polymer electrolyte‐based electrochemical devices are now emerged as a novel material for electrochemical devices. This paper reports a solid polymer electrolyte film doped with a new nanofiller synthesized by the solution casting technique. Electrical, optical, and photoelectrochemical characterization are presented in detail. Electrochemical impedance spectroscopy (EIS) shows with the dispersion of nanofillers conductivity increases attains maxima and decreases. The maximum conductivity was at 0.04 wt% nanofiller concentration of 2.05 × 10−4 S/cm. The calculated ionic transference value was 0.92 which shows the dormancy of the system as ionic. The linear sweep voltammetry confirms a high electrochemical stability window (ESW) of 4.01V. Sandwitched electrical double‐layer capacitors (EDLC) have been developed using carbon‐based electrodes and sandwitched nanofiller dispersed polymer electrolyte, showing a high specific capacitance value of ~200 F/g.

A Low‐Cost Moderate‐Concentration Hybrid Electrolyte of Introducing CaCl2 and Ethylene Glycerol Enables Low‐Temperature and High‐Voltage Micro‐Supercapacitors

AbstractHigh‐concentration electrolyte effectively improves the energy density and anti‐freezing property of aqueous micro‐supercapacitors (MSCs), endowing them the opportunity serving as power sources for miniaturized electronics. However, the excessive usage of salt significantly increases the cost of the electrolyte. Herein, a cost‐effective moderate‐concentration hybrid electrolyte is designed by introducing CaCl2 and ethylene glycerol (EG) additives for low‐temperature and high‐voltage MSCs. The results manifest that the introduction of CaCl2 minimizes the number of water molecules with strong hydrogen bonds while the addition of EG can reduce the amount of H2O molecules in the primary solvation shell sheath of Ca2+ ion and strengthen the hydrogen bonds between EG and water molecules, thus endowing the optimal electrolyte with a wide electrochemical stability window of 3.5 V and a freezing point lower than −120 °C. Furthermore, the resulting hybrid MSCs offer a high voltage of 1.6 V, and realize 62% capacitance retention at −40 °C compared to that at room temperature. Moreover, The MSCs can endure 20000 cycles with 98.5% capacitance retention at −40 °C. This work provides a meaningful guidance for designing low‐cost moderate‐concentration hybrid electrolyte with wide electrochemical stability window and anti‐freezing property for intrinsically safe and environmentally adaptable devices.

In Situ/Operando Techniques for Unraveling Mechanisms of Ionic Transport in Solid-State Lithium Indium Halide Electrolyte

Over the past years, lithium-ion solid-state batteries have demonstrated significant advancements regarding such properties as safety, long-term endurance, and energy density. Solid-state electrolytes based on lithium halides offer new opportunities due to their unique features such as a broad electrochemical stability window, high lithium-ion conductivity, and elasticity at close to melting point temperatures that could enhance lithium-ion transport at interfaces. A comparative study of lithium indium halide (Li3InCl6) electrolytes synthesized through a mechano-thermal method with varying optimization parameters revealed a significant effect of temperature and pressure on lithium-ion transport. An analysis of Electrochemical Impedance Spectroscopy (EIS) data within the temperature range of 25–100 °C revealed that the optimized Li3InCl6 electrolyte reveals high ionic conductivity, reaching 1.0 mS cm−1 at room temperature. Herein, we present the utilization of in situ/operando X-ray Photoelectron Spectroscopy (XPS) and in situ X-ray powder diffraction (XRD) to investigate the temperature-dependent behavior of the Li3InCl6 electrolyte. Confirmed by these methods, significant changes in the Li3InCl6 ionic conductivity at 70 °C were observed due to phase transformation. The observed behavior provides critical information for practical applications of the Li3InCl6 solid-state electrolyte in a broad temperature range, contributing to the enhancement of lithium-ion solid-state batteries through their improved morphology, chemical interactions, and structural integrity.

Recent Advances in Graphene-Based Materials for Zinc-Ion Batteries.

Zinc-ion batteries (ZIBs) are a promising alternative for large-scale energy storage due to their advantages of environmental protection, low cost, and intrinsic safety. However, the utilization of their full potential is still hindered by the sluggish electrode reaction kinetics, poor structural stability, severe Zn dendrite growth, and narrow electrochemical stability window of the whole battery. Graphene-based materials with excellent physicochemical properties hold great promise for addressing the above challenges foe ZIBs. In this review, the energy storage mechanisms and challenges faced by ZIBs are first discussed. Key issues and recent progress in design strategies for graphene-based materials in optimizing the electrochemical performance of ZIBs (anode, cathode, electrolyte, separator and current collector) are then discussed. Finally, some potential challenges and future research directions of graphene-based materials in high-performance ZIBs are proposed for practical applications.

Electrospun gel composite electrolyte of solvent-free SiO2 nanofluids coupled polyacrylonitrile nanofibers for high-rate lithium-metal batteries

Composite polymer electrolytes (CPEs) are considered as one of the most promising electrolytes for the next generation of solid-state lithium metal batteries (LMBs) because of their good flexibility, favorable interface contact, easy large-scale processing and improved safety. To address the severe agglomeration of inorganic nanofillers at the high-level loading, a new gel polymer electrolyte (GPE) was fabricated by electrospun membranes adopting polyacrylonitrile (PAN) as the host matrix and solvent-free SiO2 nanofluids (NFs) as nanofillers, presenting low crystallinity, high electrolyte uptake, superior flexibility, and large porosity. The as-prepared PAN/SiO2 GPEs containing 20 % SiO2 NFs show the optimum mechanical and thermal properties, the maximum ionic conductivity (3.44 x 10−4 S cm−1) and Li+ transfer number (0.73), and the widest electrochemical stable window (4.99 V). Benefiting from multiple advantages, the percolated 3D Li+ transport networks are well-established to suppress the electrode polarization and Li dendrite growth. Further, the abundant ester groups on the SiO2 NFs shell and Lewis acid-based sites on SiO2 cores are favored to dissociate lithium salts and produce more free Li+. Accordingly, the assembled solid-state LiFePO4/Li cell exhibits superior cycling stability (132.7 mAh/g after 500 cycles at 3C with a retention of 90.8 %) and rate capability (80.4 mAh/g at 25C) at ambient temperature. This work provides a facile strategy to fabricate GPEs by incorporating solvent-free NFs containing inorganic cores for LMBs with high-rate capability, good cycling stability, and high safety.

Controlling the Supramolecular Architecture Enables High Lithium Cationic Conductivity and High Electrochemical Stability for Solid Polymer Electrolytes

AbstractSolid polymer electrolytes (SPEs) are long sought after for versatile applications due to their low cost, light weight, flexibility, ease of scale‐up, and low interfacial impedance. However, obtaining SPEs with high Li+ conductivity (σ+) and high voltage stability to avoid concentrated polarization and premature capacity loss has proven challenging. Here a stretchable dry‐SPE is reported with a semi‐interpenetrating, supermolecular architecture consisting of a cross‐linked polyethylene oxide (PEO) tetra‐network and an alternating copolymer poly(ethylene oxide‐alt‐butylene terephthalate). Such a unique supermolecular architecture suppresses the formation of Li+/PEO intermolecular complex and enhances the oxidation stability of PEO‐based electrolyte, thus maintaining high chain segmental motion even with high salt loading (up to 50 wt%) and achieving a wide electrochemical stability window of 5.3 V. These merits enable the simultaneous accomplishment of high ionic conductivity and high Li+ transference number (t+) to enhance the energy efficiency of energy storage device, and electrochemical stability.

On the Na+ transport and electrochemical stability window in NaTFSI:NMA deep eutectic solvent

Deep eutectic solvents (DES), such as the ▪:▪ (sodium bistrifluoromethane sulfonyl imide - N-methyl acetamide) system, have been considered as promising electrolytes for sodium-ion (▪) batteries. However, our current atomistic understanding of those systems is still in a state of evolution and remains incomplete. In this context, we combined classical force field molecular dynamics (MD) simulations and periodic density functional theory (DFT) calculations to enhance our atomistic understanding on the ▪ transport mechanisms, DES structure organization, hydrogen-bond network formation, and electrochemical stability windows (ESWs). Firstly, we obtained a substantial improvement in the description of the DES transport and structural properties using self-consistent MD/DFT calculations to assign effective charges on all atoms, while the remaining OPLS parameters were kept constant. From our analyses, an increasing in the ▪ mole fraction leads to different chemical environments, reflecting an electrolyte with larger aggregates, low conductivity, and high viscosity. The liquid structure seems to remain unchanged as a function of temperature. However, higher temperatures reduce the lifetime of ionic pairs and increase the mobility of ▪ ions. The disruption of the hydrogen-bonds formed between the ▪ species increases with the ▪ concentration. In addition, our periodic DFT calculations reveals the substitution of atomic sites from ▪ to ▪ during the reduction process. Furthermore, the ESW results provided evidence supporting the safeguarding of the solvent from degradation at higher salt concentrations.

Amorphous Magnesium-Doped Chitosan films as solid polymer electrolytes for energy storage device applications

Magnesium ion-conducting biodegradable solid polymer electrolyte (SPE) films of magnesium perchlorate [Mg(ClO4)2] doped Chitosan [CS] were prepared using the solution casting technique at room temperature. XRD study shows that amorphous nature of the polymer matrix increases upon doping. FTIR deconvolution confirm the complexation generated between the salt and the polymer. The current–voltage measurement exhibited electrochemical stability window for all samples above 2.14 V. The ionic transference number for the highest conducting sample was 0.99. The impedance analysis was done for each SPE film, and the sample with the highest concentration (40 wt%) exhibited the highest conductivity, 5.7 × 10-4 Scm−1. The prepared primary magnesium battery using the highest conducting SPE showed open circuit potential of 2.112 V. Due to its exceptional qualities, this prepared electrolyte may be a strong contender for energy storage systems.

Structural regulation of halide superionic conductors for all-solid-state lithium batteries

Metal halide solid-state electrolytes have gained widespread attention due to their high ionic conductivities, wide electrochemical stability windows, and good compatibility with oxide cathode materials. The exploration of highly ionic conductive halide electrolytes is actively ongoing. Thus, understanding the relationship between composition and crystal structure can be a critical guide for designing better halide electrolytes, which still remains obscure for reliable prediction. Here we show that the cationic polarization factor, which describes the geometric and ionic conditions, is effective in predicting the stacking structure of halide electrolytes formation. By supplementing this principle with rational design and preparation of more than 10 lithium halide electrolytes with high conductivity over 10−3 S cm−1 at 25 °C, we establish that there should be a variety of promising halide electrolytes that have yet to be discovered and developed. This methodology may enable the systematic screening of various potential halide electrolytes and demonstrate an approach to the design of halide electrolytes with superionic conductivity beyond the structure and stability predictions.

Polyimide-Based Aqueous Potassium Energy Storage Systems Using Concentrated WiSE Electrolyte.

Aqueous batteries are considered as promising alternative power sources due to their eco-friendly, cost-effective, and nonflammable attributes. Employing organic-based electrode materials offers further advantages toward building greener and sustainable systems, owing to their tunability and environmental friendliness. In order to enhance the energy and power densities, superconcentrated aqueous electrolytes, such as water-in-salt electrolytes (WiSE), have renewed the interest in aqueous batteries due to their enhanced stability and much wider electrochemical stability window (>1.23 V) compared with the traditional aqueous electrolytes. Here, we present a perylene diimide-based electrode material (PDI-Urea) as an appealing anode for aqueous potassium energy storage systems and investigate their electrochemical performance in three WiSE electrolytes, namely, 30 M potassium acetate, 40 M potassium formate and 30 M potassium bis(fluorosulfonyl)imide (KFSI). To explore the potential of PDI-Urea for potassium-based electrochemical energy systems, we fabricated full cell devices such as aqueous potassium dual-ion battery (APDIB) and aqueous K-ion battery (AKIB) and studied their electrochemical properties with 30 M KFSI electrolyte. The full cell K-ion battery, using a PBA cathode, exhibited excellent electrochemical performance with good rate capability and impressive capacity retention of 91% upon 1000 cycles. Further, the reaction mechanism of the electrodes is systematically analyzed using ex-situ studies.

Hydrogen-bond regulation in organic/aqueous hybrid electrolyte for safe and high-voltage K-ion batteries

Hydrogen-bond regulating organic/aqueous hybrid electrolyte with immobilized H2O provides new insights into realizing high-voltage aqueous batteries without compromising safety.

Self-degrading functional unit introduction for anti-oxidation ability enhancement of a poly(vinyl ethylene carbonate) electrolyte

A novel poly(vinyl ethylene carbonate-3-sulfolene) electrolyte has been developed by copolymerizing monomer precursors, which has a wide electrochemical stability window of 5 V (vs. Li+/Li) attributed to the pre-degradation of sulfolene-based functional units.

Novel propylene carbonate based localized high concentration electrolyte with high voltage, flame retardant and wide temperature characteristics enables excellent electrochemical performances of lithium metal batteries

A novel propylene carbonate based localized high concentration electrolyte using for lithium metal batteries achieves flame retardancy, a broad electrochemical stability window, dendrite-free Li deposition, and a wide operating temperature range.

Recent progress and perspectives on metal-organic frameworks as solid-state electrolytes for lithium batteries.

Solid-state electrolytes (SSEs) are the key materials in the new generation of all-solid-state lithium ion/metal batteries. Metal-organic frameworks (MOFs) are ideal materials for developing solid electrolytes because of their structural diversity and porous properties. However, there are several significant issues and obstacles involved, such as lower ion conductivity, a smaller ion transport number, a narrower electrochemical stability window and poor interface contact. In this review, a comprehensive analysis and summary of the unique ion-conducting behavior of MOF-based electrolytes in rechargeable batteries are presented, and the different design principles of MOF-based SSEs are classified and emphasized. Accordingly, four design principles for achieving these MOF-based SSEs are presented and the influence of SSEs combined with MOFs on the electrochemical performance of the batteries is described. Finally, the challenges in the application of MOF materials in lithium ion/metal batteries are explored, and directions for future research on MOF-based electrolytes are proposed. This review will deepen the understanding of MOF-based electrolytes and promote the development of high-performance solid-state lithium ion/metal batteries. This review not only provides theoretical guidance for research on new MOF-based SSE systems, but also contributes to further development of MOFs applied to rechargeable batteries.

Flame‐Retardant Polyurethane‐Based Solid‐State Polymer Electrolytes Enabled by Covalent Bonding for Lithium Metal Batteries

AbstractSolid‐state lithium metal batteries (SSLMBs) have gained extensive attraction as one kind of next‐generation energy storage device. However, the drawbacks of flammability, low mechanical strength, and low ionic conductivity limit the further development of solid‐state polymer electrolytes (SPEs). In this work, a reactive flame‐retardant unit into the polymer framework via covalent bonding to create a nonflammable and stretchable polyurethane‐based SPEs is introduced. Meanwhile, the mechanical strength of the polymer backbone is increased by grafting a rigid benzene ring unit, which remarkably suppresses the lithium‐dendrite growth. As a result, these inflammable SPEs do not burn after contact with flames for 6 s. Furthermore, the obtained SPE expands the electrochemical stability window up to 5.1 V. Small monomers containing bromine decompose on the surface of lithium metal creating a LiBr riched solid electrolyte interface (SEI). Li|SPEs|Li symmetric battery offers a stable cycling life for more than 2100 h at 0.2 mA cm−2 and 0.2 mAh cm−2. The LiNi0.6Co0.2Mn0.2O2|SPEs|Li cell equipped with the integrated cathode delivers a 142.1 mAh g−1 capacity after 330 cycles at 0.3 C with 85.2% capacity retention.