Electrolyte Composition Research Articles

Self-supported flexible organic electrochemical synaptic transistors on self-healing composite electrolyte membranes

A variety of organic electrochemical transistors have been recently developed; however, their self-healing performance has been largely ignored. In this study, we propose the use of a lithium-ion composite electrolyte membrane as a dielectric layer and the use of poly(3-hexylthiophene) (P3HT) as a channel layer to fabricate flexible self-supporting organic synaptic transistors. A variety of synaptic behaviors were emulated within the proposed organic synaptic transistors. By leveraging the self-healing features of polymer electrolytes, along with cross-linking reactions and low-resistance lithium-ion transmission, the device maintained its electrical performance. Testing involving different curvatures also revealed the device's potential for use in flexible electronics. Significantly, due to the device's self-healing ability, consistent dataset recognition rates were sustained. This work highlights its vast prospects in the field of flexible and wearable electronics.

Composite polymer electrolyte with vertically aligned garnet scaffolds for quasi solid-state lithium batteries

Structure design is of great importance for composite solid electrolytes to meet the high requirements for lithium batteries today. Herein, a novel composite polymer electrolyte with vertically aligned fast ion pathways has been constructed through the in-situ UV-induced polymerization of poly (butyl acrylate) (PBA) based gel polymer electrolyte inside the honeycomb-structure Li6.5La3Zr1.5Ta0.5012 (LLZTO) scaffolds by freeze casting. The addition of LLZTO enhances the anion adsorption through the Lewis-acid sites of the La ions and reduces the Li+ complexation by participating in the interaction of CO⋯Li+. Therefore, the interface of PBA and LLZTO scaffold serves as a continuous Li+ transport pathway and the resulting composite solid electrolyte exhibits a high ionic conductivity (5.098×10−4 S cm−1), near single-ion conducting characteristic (a transference number of 0.8) and high electrochemical stability window (5.15 V). Based on the above superior performance, the composite electrolyte promotes uniform distribution of lithium ion concentration and electrolyte potential. Thus, quasi-solid-state LiFePO4/Li cells exhibit excellent cycling performance (capacity retention of 91.7 % after 300 cycles at 0.5 C).

Intergranular amorphous film in GeO2-enriched Li1.5Al0.5Ti1.5(PO4)3 composite electrolytes for high-performance solid-state lithium-ion batteries

Solid-state electrolytes have emerged as a key area of development in the field of Li-ion batteries owing to safety concerns surrounding liquid electrolytes. Among solid-state electrolytes, Li1.5Al0.5Ti1.5(PO4)3 (LATP), a NASICON-type material, is a leading candidate owing to its promising ionic conductivity, chemical and environmental stability, and cost-effectiveness. However, its ionic conductivity is limited by grain-boundary scattering, which hinders its broader adoption. Herein, we introduce a novel grain-boundary engineering strategy for the LATP electrolyte system using typical solid-state method, wherein a Ge-rich liquid phase spontaneously forms at the grain boundaries of GeO2-enriched LATP during synthesis, producing an intergranular amorphous film in the final material that significantly enhances Li-ion transport at the grain boundaries. With an optimal content of 4 wt% GeO2, the ionic conductivity reaches 8.92 × 10−4 S cm−1—an eightfold increase compared to that of pristine LATP. This high ionic conductivity also bestows 4 wt% GeO2-LATP with excellent cell performance, with a symmetric Li/4 wt% GeO2-LATP/Li cell exhibiting stable operation for over 500 h with low overpotentials. Our findings underscore the importance of grain-boundary engineering in advancing solid-state electrolytes and pave the way for the commercialization of next-generation all-solid-state Li-ion batteries.

Operando Temperature Dynamic Investigation of Electric Double‐Layer Capacitors Containing Organic Electrolytes

AbstractInvited for this month's cover picture is the Balducci's group who works on the development of innovative electrolytes and materials for safer, high‐performance supercapacitors and batteries, and on advanced real‐time characterization techniques to improve the understanding of aging and charge storage processes in electrochemical devices. The front cover illustrates a supercapacitor evaluated with the screening technique presented in this report. It highlights different electrolyte compositions, indicated by chemical compounds above the setup. This approach provides insights into how capacitance, energy, power, entropy, and enthalpy respond to changes in temperature and voltage. Read the full text of the Research Article at 10.1002/batt.202300581.

Fluorocarbon Nanodroplets: Their Formation and Stability in Complex Solution Systems.

Perfluorocarbon (PFC) nanodroplets (NDs) are expanding in a wide range of applications in biotechnology and nanotechnology. Their efficacy in biological systems is significantly influenced by their size uniformity and stability within bioelectrolyte contexts. Presently, methods for creating monodisperse, highly concentrated, and well-stabilized PFC NDs under harsh conditions using low energy consumption methods have not been thoroughly developed, and their stability has not been sufficiently explored. This gap restricts their applicability for advanced medical interventions in tissues with high pH levels and various electrolytic conditions. To tackle these challenges and to circumvent potential toxicity from surface stabilizers, we have conducted an in-depth investigation into the formation and stability of uncoated perfluorohexane (PFH) NDs, which were synthesized by using a low-energy consumption solvent exchange technique, across complex electrolyte compositions or a broad spectrum of pH levels. The results indicated that low concentrations of low-valent electrolyte ions facilitate the nucleation of NDs and consistently accelerate Ostwald ripening over an extended period. Conversely, high concentrations of highly valent electrolyte ions inhibit nucleation and decelerate the ripening process over time. Given the similarities between the properties of NDs and nanobubbles, we propose a potential stabilization mechanism. Electrolytes influence the Ostwald ripening of NDs by adjusting the adsorption and distribution of ions on the NDs' surface, modifying the thickness of the electric double layer, and fine-tuning the energy barrier between droplets. These insights enable precise control over the stability of PFC NDs through the meticulous adjustment of the surrounding electrolyte composition. This offers an effective preparation method and a theoretical foundation for employing bare PFC NDs in physiological settings.

Dielectric LiNbO3 electrolyte regulating internal electric field in composite solid-state electrolyte to fundamentally boost Li-ion transport

Dielectric LiNbO3 electrolyte regulating internal electric field in composite solid-state electrolyte to fundamentally boost Li-ion transport

Electropolishing of gold and gold alloys in HCl-glycerol-ethanol electrolytes

Electropolishing or electrochemical polishing (EP) is an ultrafinishing process that improves esthetic, technical and functional properties of metallic surfaces by reducing their roughness. This process is based on anodic dissolution of the workpiece through an oxidation reaction. For many years, cyanide-based electrolytes were used to electropolish precious metals like gold and its alloys. The need for safer working conditions encouraged the replacement of cyanide by other complexing agents, mainly thiourea. However, the latter is also harmful. Therefore, the aim of this work is to electropolish pure gold and 18k jewelry gold alloys (yellow, rose, red and gray) in a cyanide-free electrolyte, to evaluate the electrochemical behavior and the influence of different parameters. For this purpose, a previously reported solution based on hydrochloric acid and glycerol was used. In the first part of the study, the influence of chloride concentration on pure gold EP was determined by electrochemical techniques and surface properties analysis. The effects of adding ethanol to electrolyte composition and of variating rotation speed were also evaluated. The best results were obtained for a HCl 50% vol. - Glycerol 25 % vol. - Ethanol 25 % vol. electrolyte at a rotation speed of 1000 rpm. In the second part of the study, this solution was used to electropolish 18 K gold alloys. Silver-containing alloys were not uniformly polished due to the formation of an AgCl film on the surface that partially masks the substrates.

A “Concentrated Ionogel‐in‐Ceramic” Silanization Composite Electrolyte with Superior Bulk Conductivity and Low Interfacial Resistance for Quasi‐Solid‐State Li Metal Batteries

The ideal composite electrolyte for the pursued safe and high‐energy‐density lithium metal batteries (LMBs) is expected to demonstrate peculiarity of superior bulk conductivity, low interfacial resistances, and good compatibility against both Li‐metal anode and high‐voltage cathode. There is no composite electrolyte to synchronously meet all these requirements yet, and the battery performance is inhibited by the absence of effective electrolyte design. Here we report a unique “concentrated ionogel‐in‐ceramic” silanization composite electrolyte (SCE) and validate an electrolyte design strategy based on the coupling of high‐content silane‐conditioning garnet and concentrated ionogel that builds well‐percolated Li+ transport pathways and tackles the interface issues to respond all the aforementioned requirements. It is revealed that the silane conditioning enables the uniform dispersion of garnet nanoparticles at high content (70 wt%) and forms mixed‐lithiophobic‐conductive LiF‐Li3N solid electrolyte interphase. Notably, the yielding SCE delivers an ultrahigh ionic conductivity of 1.76 × 10−3 S cm−1 at 25 °C, an extremely low Li‐metal/electrolyte interfacial area‐specific resistance of 13 Ω cm2, and a distinctly excellent long‐term 1200 cycling without any capacity decay in 4.3 V Li||LiNi0.5Co0.2Mn0.3O2 (NCM523) quasi‐solid‐state LMB. This composite electrolyte design strategy can be extended to other quasi−/solid‐state LMBs.

Excellent Stable Cycle Performance of Polyethylene Oxide‐Based 3D Solid Dual‐Salt Composite Electrolyte with Porous Polyimide Thin Films Host

AbstractPolyethylene oxide composite electrolytes are widely used in lithium‐ion batteries because of their excellent moldability, good flexibility, and favorable chemical compatibility. However, they still suffer from low ionic conductivity and weak mechanical strength. Herein, a 3D nanofiber‐reinforced dual‐salt composite solid electrolyte (PI@PCB) is synthesized. Benefiting from the support of the porous polyimide films and the addition of lithium bis(oxalate)borate, the obtained PI@PCB electrolyte exhibits high mechanical strength, good thermal stability, excellent electrochemical stability, and a high lithium ion transference number (0.70). In addition, the assembled Li/PI@PCB/Li cell shows the lowest overpotential of 200 mV at the initial cycling stage and increases to 246 mV slightly after 1500 h. The capacity retention rate of Li/PI@PCB/LFP battery is about 88.3% after 500 cycles at 60 °C.

Revealing the effect of double bond-modified Li6.75La3Zr1.75Ta0.25O12 on the Li-ion conduction of composite solid electrolytes

Lithium metal batteries with polyethylene oxide (PEO) electrolytes have shown great potential to be one of the next-generation energy candidates. As the branch family of PEO electrolytes, poly(ethylene glycol) acrylates (PEGAs) attract more attention owing to their better electrochemical properties than that of PEO electrolytes. Introducing double bond-modified Li6.75La3Zr1.75Ta0.25O12 fillers (KH@LLZTO) has been a popular method to improve the electrochemical properties of PEGAs electrolytes due to the homogeneous dispersion of LLZTO. However, in this work, an inverse phenomenon is discovered. The electrochemical properties of PEGAs electrolytes get worse when introducing KH@LLZTO. By exploring the Li+ transport mechanism, the reason for the inverse phenomenon is revealed. More importantly, the design principle of PEGAs electrolytes with fast ionic conductor fillers is presented. Double bond-modified LLZTO can decrease the electrochemical properties of PEGAs electrolytes instead when there are low-molecular weight monomers that can participate in the PEGAs polymer network and interact with Li+, while the double bond-modified LLZTO can improve the electrochemical properties of PEGAs electrolytes when there are not aforementioned low-molecular weight monomers. This work provides a new understanding for componential design and optimization of PEGAs electrolytes with fast ionic conductors, hoping to promote the practical application of PEGAs electrolytes.

Sulfonated poly(ether ether ketone)-Protic ionic Liquid-Based anhydrous Proton-Conducting composite polymer electrolyte membranes for High-Temperature fuel cell applications

A high-temperature polymer electrolyte membrane fuel cell (PEMFC) has enormous potential to produce clean energy with minimal environmental pollution along with high energy density and conversion efficiency. In the present work, anhydrous proton-conducting polymer electrolyte membranes for prospective high-temperature fuel cell application were successfully prepared using different protic ionic liquids (PILs) and sulfonated poly(ether ether ketone) (SPEEK). The protic ionic liquids (PILs), 2-hydroxyethylammonium formate, diethylmethyl ammonium triflate, 1-ethylimidazolium bis(trifluoromethylsulfonyl)imide, 1,2-dimethyl imidazolium bis(trifluoro methylsulfonyl)imide, and diethylmethylammonium methanesulfonate were selected based on their favorable physicochemical properties. The effect of the incorporation of the PIL on the structural, thermal, and electrical transport properties of the composite SPEEK polymer electrolyte membranes was studied. The prepared polymer electrolyte membranes (PEMs) were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and electrochemical impedance spectroscopy (EIS) techniques. FTIR results indicated an interaction between the PIL and the SPEEK, which resulted in homogeneous and flexible membranes. The DSC results confirmed good miscibility and elucidated plasticizing effect of the incorporated PIL on the SPEEK polymer matrix. All the PEMs showed good thermal stability and high-temperature anhydrous proton conductivity, achieving best proton conductivity, ≈8 × 10–3 S cm−1 at 120 °C and low activation energy ≈0.26 eV, making it suitable for prospective high-temperature PEMFC applications.

Investigating sulfide-based all solid-state cells performance through P2D modelling

All solid-state batteries, combining metallic lithium with a solid-state electrolyte, are now considered as a very promising answer to the growing need for higher energy density in safer batteries. While research interests are quickly raising on this topic, the number of experiments to perform in order to find the best combination of active material and solid electrolyte composition could be infinite. Therefore, an easy and low computational-cost model forecasting all solid-state cells performance could accelerate the optimization and lower the number of experiments, reaching more rapidly an up scalable solution.In this work, an innovative electrochemical model for a metallic lithium – argyrodite Li6PS5Cl – NMC622 cell is developed. In particular, two important aspects, characterizing this new battery generation, are implemented inside a P2D model.The first aspect is the implementation of a solid-state electrolyte, in substitution to liquid electrolyte, which means using the single ion conducting electrolyte theory, according to which Ohm's law is the only equation to be solved in the electrolyte domain. This reduces the number of parameters characterizing the electrolyte from three, for the liquid electrolyte (ionic conductivity, transference number, and mean molar activity coefficient), to only one, for the solid electrolyte (ionic conductivity). The second aspect regards the anode side, lithium metal is chosen, in substitution to graphite, and this implies a different treatment from an electrochemical point of view, which is to consider the anode as a boundary condition instead of a porous electrode. Such drastic simplification of the P2D model allows, after careful calibration and validation based on experimental data, to obtain reliable charge/discharge profiles at C/10 and C/5 for lithium – argyrodite Li6PS5Cl – NMC622 cells.

Flexible High Lithium-Ion Conducting PEO-Based Solid Polymer Electrolyte with Liquid Plasticizers for High Performance Solid-State Lithium Batteries.

Lithium-ion secondary batteries (LIB) with high energy density have attracted much attention for electric vehicle (EV) applications. However, LIBs have a safety problem because these batteries contain a flammable organic electrolyte. As such, all-solid secondary batteries that are not flammable have been extensively reported recently. In this study, we have focused on polymer electrolytes, which is flexible and is expected to address the safety problem. However, the conventional polymer electrolytes have low electrial conductivity at room temperature. Various attempts have been made to solve this problem, such as the addition of inorganic fillers and ionic liquids; however, these composite polymer electrolytes have not yet reached a practical level of lithium-ion conductivity. In this study, high electrical conductivity and lithium dendrite formation-free PEO based composite electrolytes are developed with both a filler of Li6,4La3Zr1.4Ta0.6O12 and liquid plasticizers of tetraethylene glycol dimethyl ether and 1,2 dimethoxyethane. The proposed flexible polymer electrolyte shows a high electrical conduciviy of 6.01×10-4 S cm-1 at 25 °C.

Clean and efficient preparation of metallic bismuth from methane-sulfonate electrolyte in the membrane electrolysis cell

As a prevailing hydrometallurgical extraction system for bismuth sulfide concentrate, the acidic chloride solution has superior applicability to raw materials and high recovery ratio of metallic bismuth. Nevertheless, it has disadvantages of being easily volatile and strongly corrosive, as well as large energy consumption and poor deposition morphology during chloride electrolysis. Methane-sulfonic acid (MSA) solution is widely considered as the next generation of green hydrometallurgical system, due to its excellent physicochemical properties such as high metal salts solubility, low volatility, and biodegradability. In this study, membrane electrolysis technique was adopted based on the acidic bismuth methane-sulfonate leaching solution, and the influence of electrolyte composition, cathode current density (CCD), and temperature parameters on the bismuth conversion ratio (BCR) and deposition rate (BDR), techno-economic indicators and cathodic bismuth morphology were studied. The results show that the CCD affects the deposits morphology significantly, and the bismuth metal is partially dark and composed of loose ellipsoidal particles at high current density. Under the optimal conditions (70 g/L Bi3+ ions, 5 g/L Fe2+ ions, 110 g/L MSA, 35 °C, 180 A/m2), high-purity metallic bismuth (Bi 99.97 %) with silver-white luster is obtained. The BCR and BDR are 9.43 % and 0.46 kg/(h·m2), respectively. The cathodic current efficiency (CCE) reaches over 98 %, and specific energy consumption (SEC) is less than 715 kWh/t Bi. Compared with the traditional chloride system, the MSA-based membrane electrolysis medium has advantages of environmental friendliness, low occupational risks, low carbon and energy consumption, and can thus provide a sustainable green solution for bismuth hydrometallurgy.

Cover Image, Volume 141, Issue 20

Wet spinning of chitin nanowhiskers: Effects of electrolyte composition in coagulation baths on mechanical properties and nanowhisker orientation by Jun Araki and Minami Nakajima. DOI: 10.1002/app.55335 image

Improved electro-kinetics of new electrolyte composition for realizing high-performance zinc-bromine redox flow battery

Aqueous Redox Flow Batteries (ARFB) are the most prominent technology for large-scale energy storage applications. The energy density of the ARFBs is mainly determined by the electrolyte components, which highly influence the flow battery performance. In the present work, we acutely investigated the various electrolyte compositions and optimized the best electrolyte for realizing the high performance of Zn-Br2 ARFBs. The electrode kinetics, such as rate constant, exchange current density, conductivity, and diffusion coefficient, were analyzed using electrochemical techniques, cyclic voltammetry, and electrochemical impedance analysis. It was observed that zinc bromide (ZnBr2) + perchloric acid (HClO4) + 1-Ethyl-1-methylmorpholinium bromide (MEM) + N-ethyl-N-methylpyrrolidinium bromide (MEP) and ZnBr2 + zinc chloride (ZnCl2) + MEM + MEP electrolytes showed improved performance, where the redox kinetics of 2Br-/Br2 redox couple is greatly enhanced. The presence of perchloric acid unlocks the capacity of full electro-oxidation of bromide (Br-) to bromine (Br2) as it involves 1e- per Br-, which would be highly beneficial to attain high energy density. Further, Zn-Br2 RFB adopted with optimized electrolyte formulation ZnBr2 + HClO4 + MEM+ MEP shows a better round-trip efficiency and displays a stable long cycling performance over 200 cycles with an energy (EE) and coulombic efficiency (CE) of > 68% and > 92%, respectively.

Constructing Robust LiF‐Enriched Interfaces in High‐Voltage Solid‐State Lithium Batteries Utilizing Tailored Oriented Ceramic Fiber Electrolytes

AbstractThe pursuit of high‐performance energy storage devices has fueled significant advancements in the all‐solid‐state lithium batteries (ASSLBs). One of the strategies to enhance the performance of ASSLBs, especially concerning high‐voltage cathodes, is optimizing the structure of composite polymer electrolytes (CPEs). This study fabricates a high‐oriented framework of Li6.4La3Zr2Al0.2O12 (o‐LLZO) ceramic nanofibers, meticulously addressing challenges in both the Li metal anode and the high‐voltage LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode. The as‐constructed electrolyte features a highly efficient Li+ transport and robust mechanical network, enhancing both electron and ion transport, ensuring uniform current density distribution, and stress distribution, and effectively suppressing Li dendrite growth. Remarkably, the Li symmetric cells exhibit outstanding long‐term lifespan of 9800 h at 0.1 mA cm−2 and operate effectively over 800 h even at 1.0 mA cm−2 under 30 °C. The CPEs design results from the formation of a gradient LiF‐riched SEI and CEI film at the Li/electrolyte/NCM811 dual interfaces, enhancing ion conduction and maintaining electrode integrity. The coin‐cells and pouch cells demonstrate prolonged cycling stability and superior capacity retention. This study sets a notable precedent in advancing high‐energy ASSLBs.

The Electrocatalytic Activity of Au Electrodes Changes Significantly in Various Na+/K+ Supporting Electrolyte Mixtures

The potential of maximum entropy (PME) is an indicator of extreme disorder at the electrode/electrolyte interface and can predict changes in catalytic activity within electrolytes of varying compositions. The laser‐induced current transient technique is employed to evaluate the PME for Au polycrystalline (Aupc) electrodes immersed in Ar‐saturated cation electrolyte mixtures containing potassium and sodium ions at pH = 8. Five cation ratios (0.5 M K2SO4:0.5 M Na2SO4 = 0:1, 0.25:0.75, 0.5:0.5, 0.75:0.25, and 1:0) are explored, considering earlier studies that unveil cation‐dependent shifts at near‐neutral pH. Moreover, for all electrolyte compositions, electrochemical impedance spectroscopy is utilized to determine the double‐layer capacitance (CDL), the minimum of which should be close to the potential of zero charge (PZC). By correlating cation molar ratios with the PMEs and PZCs, the impact on the model oxygen reduction reaction (ORR) activity, assessed via the rotating disk electrode method, is analyzed. The results demonstrate a linear relationship between electrolyte cation mixtures and PME, while ORR activity exhibits an exponential trend. This observation validates the PME–activity link hypothesis, underscoring electrolyte components’ pivotal role in tailoring interfacial properties for electrocatalytic systems. These findings introduce a new degree of freedom for designing optimal electrocatalytic systems by adjusting various electrolyte components.

Effect of flame retardant hexafluorocyclotriphosphazene on combustion characteristics of electrolyte for lithium-ion batteries

Hexafluorocyclotriphosphazene (HFPN) is a promising flame retardant to be applied in lithium-ion batteries (LIBs) to decrease the fire risk during the treatment of electrolyte. In this manuscript, the influence of HFPN on the combustion characteristics of LIB electrolyte was investigated, the combustion behaviors and flame retardancy of the electrolyte with or without HFPN were systematically studied by using cone calorimeter, flash point meter and a series of standard equipment, as well as self-made water spray fire extinguishing platform. The flash points of 3 kinds of control group as base solution and 3 kinds of flame-retarded electrolyte were measured and obtained by SCKB3000 closed cup automatic flash point tester. The combustion characteristics of 6 types of electrolytes were analyzed by a cone calorimeter. The heat release rate (HRR), fire growth index (FGI), fire magnitude index (FMI) and other important combustion parameters of the electrolytes were studied. Based on the self-made water mist fire extinguishing platform, the fire extinguishing effect on 6 kinds of electrolytes under the same water mist condition was compared, and the influence of flame retardants in the fire extinguishing process was analyzed. The results showed that the change of flash point was obviously related to the composition of electrolyte. Flame retardant could reduce the peak HRR (pHRR) during electrolyte fire to a large extent, while it could also prolong the combustion duration of electrolyte pool fire. Under the action of fine water mist, the electrolyte pool fire would quickly extinguish, but there would remain a lot of smoke.

Weakening Ionic Coordination for High Ionic Conductivity Composite Solid Electrolytes

Weakening Ionic Coordination for High Ionic Conductivity Composite Solid Electrolytes