Mixed Electrolyte Research Articles

Evaluation of 3D surface roughness in electrochemical micromachining of Nitinol

Equiatomic nickel-titanium (NiTi) composed of Nickel and Titanium (i.e. 50:50% of Ni and Ti) or Nitinol, an expensive, very smart shape memory alloy material of choice for biomedical applications because of its bio compatibility. Machining Nitinol is challenging by means of non- traditional techniques. Experiments are carried out to produce a precise geometrical micro hole in Shape memory alloy Nitinol, using Electrochemical Micromachining (Abbreviated as ECMM). In ECMM process, micro holes are produced with 500 μm tool electrode in a shape memory alloy (SMA)—Nitinol of 0.25 mm thickness using the Non-passivating electrolyte (NPE), Passivating electrolyte (PE) and the Composite electrolyte (CPE) to study the machining characteristics. A tedious effort is made to produce such a micro hole using a noval mixed electrolyte to improve machining process. Polarization studies are also carried out for all the chosen electrolytes. The process is clearly analyzed thoroughly with the help of polarization and SEM. Expected results with good precision and surface characteristics are obtained when the nitinol is machined with the composite electrolyte. The results proved that the compatibility of machining nitinol is composite type of electrolyte. Composite electrolyte provides the combined advantages of both the passivated and non-passivated electrolytes. This study resulted in finding the suitable and optimized parameters for machining Nitinol with PE, NPE and CPE with better precision and good surface integrity.

Plasma electrolytic oxidation of zircaloy-4 in a mixed alkaline electrolyte

Characteristics of coating resulted from plasma electrolytic oxidation (PEO) of zircaloy-4 in an electrolyte containing phosphate, silicate, and hydroxide were investigated. The mixed electrolyte is proposed to reduce power consumption. PEO was conducted in a DC mode at a current density of 30, 50, and 70 mA/cm2. Plasma was generated at a relatively low breakdown voltage of 150 V, independent of the current density. The resulting coating was composed of amorphous SiO2 and crystalline monoclinic (m) and tetragonal (t) ZrO2 phases. XRD analysis revealed that the porous outer layer developed at 30 mA/cm2 was dominated by the m phase. The percentage of the m phase decreased while the t phase increased with increasing current density. Therefore, the coating formed at 70 mA/cm2 showed the highest abrasive wear resistance, three times higher than the substrate. Similarly, the polarization curve and electrochemical impedance spectroscopy showed that the highest corrosion resistance, more than two orders of magnitude higher than the substrate, was obtained in the coated-70 mA/cm2 specimen. The use of low power and a mixed electrolyte is beneficial in producing PEO coating with high wear resistance and excellent anti-corrosion characteristic.

Phase boundary of gas hydrates in single and mixed electrolyte solutions: Using a novel unified equation of state

The phase boundary of gas hydrates is key to flow assurance, energy recovery, and hydrate-based technologies. In this work, a new thermodynamic model has been proposed for calculating the phase boundary of gas hydrates based on a unified equation of state (EoS) for the non-hydrate phases and the van der Waals-Platteeuw (vdW-P) model for the hydrate phase. A modified Peng-Robinson EoS is employed to describe the interactions between water, gas, and uncharged ions, combining with a simplified explicit mean spherical approximation (MSA) term for the long-range Coulombic forces and the Born terms for the discharging-charging process of ions. A new set of reference properties have been applied and the Kihara parameters in the vdW-P model are optimized by fitting against the measured phase boundary data of hydrates formed in the pure water. The newly developed model has been validated with 734 measured phase boundary data points of pure CH4 and binary CH4-C2H6 and CH4-CO2 hydrates formed in single- and mixed-NaCl, KCl, MgCl2, and CaCl2 solutions as well as in the pure water. It is found that this model is capable of predicting the phase boundary of CH4 hydrates formed in the 1–1 electrolyte solutions (NaCl-KCl) with the average absolute relative deviation (AARD) of 3.7%. The AARD of CH4 hydrates formed in the 2–1 electrolyte solutions (MgCl2-CaCl2) is 4.2%, which is greater than that for the 1–1 electrolytes. This is acceptable given the fact that none of the ion-associated parameters have been optimized in this work. The calculated phase boundary of pure CH4 hydrate formed in mixed-electrolyte solutions deviates from the measured ones only by 2.8%. The AARD of the binary hydrates (CH4-CO2 and CH4-C2H6) formed in single- and mixed-electrolyte solutions is 3.5%. This model can also be reduced to calculate the hydrate phase boundary in pure water. The AARD of the CH4-CO2 hydrates formed in pure water is determined as 3.0%. The overall AARD of these 734 data points predicted by this newly developed model is 3.4%, which proves the capability of the newly developed model in predicting the phase boundary of hydrates in multi-component systems. It is also presented that this unified EoS is reliable to determine the gas solubility in aqueous phase with and without electrolytes.

Thermodynamics of ion exchange coupled with swelling reactions in hydrated clay minerals

Crystalline hydrates of swelling clay minerals (smectites) exhibit a strong coupling between their ion exchange and hydration/dehydration reactions. The uptake or removal of water from smectite interlayers as a result of a change in the environmental conditions also leads to the partitioning of cations. Three factors, the solid ion composition, the solid basal spacing/water content, and the aqueous solution composition, are all implicated in controlling the thermodynamics of ion exchange. However, conventional approaches to measuring the exchange free energy cannot separate the influence of each of these individual factors. Here, we explore the energetics of the swelling and ion exchange reactions in montmorillonite using a potential of mean force approach and the thermodynamic integration method within molecular simulations. We investigate the influence of solution and clay composition on the spontaneity of the reactions, focusing on the 2 water-layer hydration state. The swelling simulations provide the equilibrium water content, interlayer water structure, and basal spacings, while thermodynamic integration of sodium–potassium exchange in the aqueous solution and solid phase are combined to calculate ion exchange free energies as a function of solution composition. Results confirm the tendency of the clay to collapse to lower hydration states as the concentration of the solution increases. Changes to the equilibrium water content, even at fixed hydration states, and the composition of the mixed electrolyte solution play a critical role in driving ion exchange and the selectivities of the clay to the exchanged cation, while the composition of the solid phase is shown to be insignificant. These findings underscore the extreme sensitivity of clay swelling and ion exchange thermodynamics to small (tenths of an Angstrom) deviations in layer spacing.

Electrochemical manufacture of graphene oxide/polyaniline conductive membrane for antibacterial application and electrically enhanced water permeability

Electrofiltration, an effective approach for membrane fouling mitigation, is significantly limited by membrane properties. A facile electrochemical method was proposed to fabricate the graphene oxide/sulfuric acid-doped polyaniline (GO/S-PANI) membrane. For which, charging the graphite in H2SO4 (98 wt%) to obtain graphite intercalation compound (GIC), then in a mixed electrolyte (H2SO4, CuSO4, (NH4)2SO4), GO was exfoliated and assembled concurrently on the PANI membrane, which was doped by H2SO4 simultaneously. The introduction of Cu2+ made the GO layers on the membrane stable. Also, the GO/S-PANI membrane showed higher conductivity (55.6 S m−1) than the PANI membrane (0.019 S m−1). Moreover, GO/S-PANI membrane possessed a more applicable pore structure and improved hydrophilicity. As a result, membrane rejection increased, and the resistance to the negatively charged pollutants was enhanced. For 1 V electrofiltration of yeast suspension, water permeation was sustainably raised by using GO/S-PANI membrane than PANI membrane. The GO/S-PANI membrane was more stable with 1 V than without electric fields. The antibacterial rate can reach 92.1% for the GO/S-PANI membrane against Escherichia coli. Overall, our strategy provides a facile preparation method for the GO/S-PANI conductive membrane with application potential in electrofiltration and antibacterial fields.

Electrolyte-Guided Design of Electroreductive CO Coupling on Copper Surfaces

Engineering the interfacial distribution of electrolytic ions can aid in modulating the electrocatalyst performance and efficiency. Using a hybrid quantum-classical modeling approach, we describe how predictive tuning of the solution microenvironment on copper can enhance the efficiency of CO2 reduction (CO2R) to C2 products. We elucidate how competing electrolyte constituents in mixed electrolyte solutions stimulate restructuring of the electrochemical double layer (EDL) and stabilize the OCCO* dimer (* denotes surface adsorbed), with predictions validated in flow reactors using copper gas diffusion electrodes (Cu-GDEs). Our findings highlight how molecular-scale electrolyte engineering with informed models of the EDL can be leveraged to tailor CO2R activity and selectivity toward C2 products.

Assessing capacity loss remediation methods for asymmetric redox flow battery chemistries using levelized cost of storage

Redox flow batteries, a promising grid-scale energy storage solution, have an open architecture that can host a broad range of redox electrolytes. Vanadium is the most mature chemistry, which is largely due to its symmetry, where all active species are based on a single parent compound, that allows for inexpensive crossover remediation via rebalancing. However, the industry has increasingly sought chemistries with lower-cost and higher-abundance redox couples. Most chemistries cannot be configured symmetrically, though, necessitating research into capacity-recovery methods for asymmetric chemistries. In this work, we adapt our previously developed levelized cost of storage model, which tracks capacity fade and recovery and evaluates the costs across the battery's lifetime, to analyze two classes of asymmetric chemistries, those with active species of finite or infinite lifetimes, and their respective remediation options. For finite-lifetime chemistries, we explore active-species replacement to counter decay. For infinite-lifetime chemistries, we consider two methods for addressing crossover: imposition of pseudo-symmetry via the spectator strategy (i.e., mixed electrolytes) and elimination of crossover via membranes with perfect selectivity. We anticipate this framework will help guide the evaluation and design of new redox chemistries, balancing the desire for low capital costs with the need to remediate capacity repeatedly and inexpensively.

Miniature Ion‐selective Electrodes with Mesoporous Carbon Black as Solid Contact

AbstractHerein, we demonstrated miniature solid‐contact ion‐selective electrodes (ISEs) using a commercial mesoporous carbon black (MCB) as ion‐to‐electron transducer. MCB is attractive in its high surface area, good conductivity, relative low cost and availability. ISEs for potassium (K+) and nitrate (NO3−) ions were prepared by subsequently coating the sealed glass capillaries (1.5 mm) with MCB and ion‐selective membranes. Addition of MCB substantially stabilized electrode response by providing adequate double‐layer capacitance and lowering resistance by more than 100× compared to the coated‐wire electrodes. The electrodes exhibited near‐Nernstian slopes of 59.6 (K+ ionophore), 57.8 (K+ ion‐exchanger) and −54.8 (NO3− ion‐exchanger) with standard solutions in the range of 10−5 to 10−1 M. Fast response (∼10 s) and reproducible sensitivities were also obtained in a mixed electrolyte containing interfering ions, although with a baseline drift of 2–10 mV/day in the long term. Importantly, the electrodes can be simply stored in air between measurements and used directly without conditioning in solutions. With simple fabrication and free maintenance, these sensors offer a low cost and convenient alternative to bulk ISEs, especially when sample volumes or space are limited.

The Critical Role of the Solvent Effect on Titanium Anodizing Current

Ti anodization was carried out in five mixed electrolytes containing polyethylene glycol and ethanol of different proportions. We found that in the mixed electrolytes containing a high proportion of ethanol, dense films with uneven surfaces were obtained. In the mixed electrolytes containing low proportion of ethanol, orderly nanotube arrays were obtained and their growth rates were inhibited under smaller anodizing current. We therefore introduce the concept of hydrogen bond and electron mobility to discuss the essential relationship between the solvent effect and the anodizing current; in addition, the ionic and electronic dual–current model and oxygen bubble mold are invoked to explain the microstructures obtained in each electrolyte.

Chemical Speciation of Zinc–Halide Complexes in Zinc/Bromine Flow Battery Electrolytes

Zinc/bromine flow batteries are a promising solution for utility-scale electrical energy storage. The behavior of complex Zn–halogen species in the electrolyte during charge and discharge is currently not well-understood, and is an important aspect to be addressed in order to facilitate future electrolyte formulations. The speciation of the primary zinc bromide electrolyte with and without a secondary zinc chloride electrolyte is studied in the present work. Raman spectroscopy was carried out on aqueous solutions of zinc bromide at 5 concentrations (2–4 M) to account for the initial and later stages of charging, with 3 concentrations (1–2 M) of zinc chloride. Mixed solutions containing various combinations of each primary and secondary electrolyte concentrations were also studied. Semi-quantitative analysis of peaks after Gaussian and Lorentzian peak deconvolution showed that the proportion of four-ligand coordinated Zn–halides (i.e. [ZnBr4]2− and [ZnCl4]2−) increases with higher salt concentration, as compared to complexes with lower halide coordination numbers. The presence of a previously unassigned peak was observed at the 220 cm−1 band in the Raman spectra of mixed electrolytes. Results from ab-initio molecular modeling using the GAUSSIAN 16 software package suggests this peak is due to the presence of the hybrid-halide anionic complex [ZnBr2Cl(H2O)]–. Increasing the Cl:Br ratio in electrolytes promotes hybridization and subsequently decreasing the proportion of single-halide Zn–Br complexes. While this speciation study is focused on Zn/Br batteries, the findings are also potentially applicable to other energy storage and electrochemical systems containing zinc halide electrolytes.

Activated carbon derived from bamboo-leaf with effect of various aqueous electrolytes as electrode material for supercapacitor applications

Activated carbon (AC) material has been prepared from bamboo-leaf carbonized under high temperature at 500 °C for 2hr. Then, the chemical reaction method was processed on carbon material to activate using KOH solvent as activating agent. XRD and FT-Raman have confirmed the crystal structure and molecule interaction of the prepared activated carbon. The morphology was characterized using FE-SEM (EDS). The novelty of activated carbon was studied by various aqueous electrolyte such as 1 M Na2SO4, 0.5 M KOH and 1 M Na2SO4 + 0.5 M KOH. The activated carbon delivers the high specific capacitance found as 290F/g at 1A/g using mixed electrolyte (1 M Na2SO4 + 0.5 M KOH). In addition, capacity retention was achieved 93% after 1000 cycles at 10A/g. Mixed electrolytes can be used as a promising electrode material for supercapacitors with high power density.

Cost-effective, long-term aqueous rechargeable hybrid sodium/zinc batteries based on Zn anode and Na3MnTi(PO4)3 cathode

Aqueous rechargeable batteries have promising application in large-scale energy storage owing to their cost-effective, eco-friendly, high safety and good electrochemical performance. An aqueous rechargeable hybrid sodium/zinc battery with Zn anode, Na3MnTi(PO4)3 cathode and 0.5 mol L-1 CH3COONa and Zn(CH3COO)2 mixed electrolyte has been designed for the first time. The battery delivered a reversible and stable capacity of 95.0 mAh g−1 at 1.5 C for 50 cycles with a high and flat working voltage of 1.75 V vs. Zn2+/Zn. Impressively, the battery showed the excellent cycling performance and superior rate capability, which can be cycled at 10.0 C for 2000 cycles with a capacity retention of 93.6% and a reversible capacity of 55.6 mAh g−1 at 30.0 C. Meanwhile, the co-intercalation mechanism of hybrid Na+ and Zn2+ in the cathode is elucidated by cyclic voltammogram, ex-situ XRD, ex-situ XPS and Rietveld refinement analysis. This work gets insight into the charge/discharge processes of hybrid ions for NASICON-structured Na3MnTi(PO4)3, providing a feasible way to design cost-effective, high safety and long-term aqueous rechargeable batteries.

Electrolytic alloying of iron-chromium during deposition of coatings from a sulfate-chloride electrolyte

The paper presents the results of studies of the process of electroreduction of alloy iron-chromium from a sulfate-chloride electrolyte, influence of electrolyte composition and electrolysis (acidity, electrolyte temperature and cathode current density) on the process kinetics, the output of the alloy current efficiency and physico-mechanical properties of the coatings (microhardness, morphology). There were determined such parameters as the optimal ratio of concentrations of electrolyte components – 150 g/l of iron chloride (2) and 50 g/l of chromium sulfate (3) and modes of electrical recovery of metals – current density 40 A/dm2; the temperature of the electrolyte is 50°C, the acidity of the solution is 0.5 pH units, which contribute to obtaining a high-quality coating with high tribological characteristics. Assumptions are made about the mechanism of the alloy formation by electrolysis from a mixed electrolyte.

Mixed gel electrolytes: Synthesis, characterization, and gas release on PbSb electrode

Abstract Mixed gel electrolytes were fabricated chemically at a temperature range of 2–5°C using some additives comparing with traditional electrolytes (1.26 g/cm3 H2SO4). The polyacrylamide (PAM) content is kept constant (0.2 wt%), while the propylene glycol (PPG) and nano fumed silica (NFS) contents varied. The material characteristics of samples were assessed by physical appearance observation, electrochemical measurements, and physicochemical methods. The results showed that a hard gel without separation of solutions was found in the case using a PAM/PPG/NFS ternary additive (0.2/0.1/0.6 wt%). The morphological structure (<50 nm) of mixed gel electrolytes was in the range of nanometer. The gas release on the PbSb electrode was strongly inhibited (92.2–93.7% for O2 and ∼55% for H2 at the 120th cycle), which will both contributes to reducing the pressure as well as limiting water loss in the sealed lead acid battery, compared with that in the sulfuric acid medium.

Vanadium/Oxygen Systems for Energy Storage

With the increase in renewable energies worldwide, the demand for storage technologies to cover capacity shortages is increasing. Due to their modular scalability and decentralized installation options, batteries are ideally suited for this task. Redox flow batteries (RFB) in particular offer the possibility of potentially low storage costs over a long service life, with simultaneous independent scalability of performance and energy. In the scientific literature there is an almost unmanageable variety of different redox pairs and redox pair combinations for RFBs [1]. However, in addition to the zinc/bromine RFB, the vanadium redox flow battery (VRFB) [2] is almost exclusively in a marketable state of development. To date, hundreds of MWh of electrical energy have been installed or are currently under construction. A disadvantage of VRFBs is the relatively low energy density with a maximum of 30 Wh/L and the necessity to integrate a cooling concept to avoid electrolyte temperatures above 40 °C. The energy density of VRFBs is relatively low with a maximum of 30 Wh/L.These problems were addressed by developments resulting in V/Br-RFBs and VRFBs with HCl/H2SO4 mixed acid electrolytes. Vanadium/oxygen systems are another possibility for using vanadium as an energy storage medium that was recognized at an early stage [3]. Vanadium/oxygen systems use the redox pairs V2+/V3+ and O2/O2- in different configurations, whereby the standard potential difference is 1.49 V. With VRFBs, the energy density and temperature stability are largely determined by the behaviour of pentavalent VO2 + cations, which is why significantly higher energy densities and temperatures of over 60 °C can be achieved with vanadium/oxygen systems with up to 150 Wh/L [4]. Furthermore, only half the vanadium is required. Depending on the mode of operation, vanadium/oxygen systems can function as unitary redox flow batteries with charging and discharging in the same cell or as separate units in two separate cells for charging and discharging. Strictly speaking, this is a combination of vanadium/oxygen fuel cell and vanadium/water electrolyser.In the context of this overview presentation, the developments of the last years in vanadium/oxygen systems from Fraunhofer ICT and UNSW are presented on the basis of vanadium/oxygen fuel cells and vanadium/water electrolysers. For example, electrolyte studies have been performed to increase concentration and energy density up to 150 Wh/L, cell studies have been performed resulting in a stack of 5 cells and a cell design with two membranes to avoid side reactions. Upscaling into a stackable cell design was performed and furthermore the reversal of reactions with vanadium/water electrolysers was investigated and the feasibility of energy storage was demonstrated. In addition, techno-economic modelling and simulation was performed to calculate investment costs and to investigate the cost distribution especially in comparison with other RFBs.1 Noack, J.; Roznyatovskaya, N.; Herr, T.; Fischer, P. The Chemistry of Redox-Flow Batteries. Angew. Chem. Int. Ed. 2015, 54, 9776-9809, doi:10.1002/anie.201410823.2 Skyllas‐Kazacos, M.; Rychcik, M.; Robins, R.G.; Fane, A.G.; Green, M.A. New All‐Vanadium Redox Flow Cell. Journal of The Electrochemical Society 1986, 133, 1057-1058, doi:10.1149/1.2108706.3 Kaneko, H., Negishi, A., Nozaki, K., Sato, K., Nakajima, M. Redox Battery, Patent US5318865A, 1994.4 Risbud, M.; Menictas, C.; Skyllas-Kazacos, M.; Noack, J. Vanadium Oxygen Fuel Cell Utilising High Concentration Electrolyte. Batteries 2019, 5, 24, doi:10.3390/batteries5010024. Figure 1

Electrochemical performance of the mixed solid electrolyte (100-x)Li3SI-xLi6PS5Cl (x = 0, 10, 20, and 30) for all-solid-state lithium batteries

In this study, solid electrolytes with improved performance are synthesized by mixing Li3SI with an anti-perovskite structure that is stable to lithium metal and Li6PS5Cl with high ionic conductivity. (100–x)Li3SI-xLi6PS5Cl (x = 0, 10, 20, 30), which is a mixture of two sulfide-based solid electrolytes, is prepared by ball milling. The structural characteristics, surface morphology, and particle size of the electrolyte material are analyzed using physico-chemical characterization technologies, such as high-power X-ray diffraction and field emission scanning electron microscopy. Electrochemical impedance spectroscopy is used to calculate the ionic conductivity of the mixed solid electrolyte. The ionic conductivity of 80Li3SI–20Li6PS5Cl, which exhibits the best all-solid-state lithium battery performance, is 5.84 × 10−4 S cm−1. In addition, 80Li3SI–20Li6PS5Cl shows excellent stability against lithium metal. The 2032-type coin cell composed of fabricated Li–In/80Li3SI–20Li6PS5Cl/NCM811 composites shows a superior capacity of 165 mAh g−1 in the initial cycle. This study provides high ionic conductivity and excellent electrochemical performance through the mixing of two kinds of solid electrolyte materials to obtain a promising solid electrolyte.

Mixed Lithium and Sodium Ion Aprotic DMSO Electrolytes for Oxygen Reduction on Au and Pt Studied by DEMS and RRDE

In order to advance the development of metal-air batteries and solve possible problems, it is necessary to gain a fundamental understanding of the underlying reaction mechanisms. In this study we investigate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER, from species formed during ORR) in Na+ containing dimethyl sulfoxide (DMSO) on poly and single crystalline Pt and Au electrodes. Using a rotating ring disk electrode (RRDE) generator collector setup and additional differential electrochemical mass spectrometry (DEMS), we investigate the ORR mechanism and product distribution. We found that the formation of adsorbed Na2O2, which inhibits further oxygen reduction, is kinetically favored on Pt overadsorption on Au. Peroxide formation occurs to a smaller extent on the single crystal electrodes of Pt than on the polycrystalline surface. Utilizing two different approaches, we were able to calculate the heterogeneous rate constants of the O2/O2− redox couple on Pt and Au and found a higher rate for Pt electrodes compared to Au. We will show that on both electrodes the first electron transfer (formation of superoxide) is the rate-determining step in the reaction mechanism. Small amounts of added Li+ in the electrolyte reduce the reversibility of the O2/O2− redox couples due to faster and more efficient blocking of the electrode by peroxide. Another effect is the positive potential shift of the peroxide formation on both electrodes. The reaction rate of the peroxide formation on the Au electrode increases when increasing the Li+ content in the electrolyte, whereas it remains unaffected on the Pt electrode. However, we can show that the mixed electrolytes promote the activity of peroxide oxidation on the Pt electrode compared to a pure Li+ electrolyte. Overall, we found that the addition of Li+ leads to a Li+-dominated mechanism (ORR onset and product distribution) as soon as the Li+ concentration exceeds the oxygen concentration.Graphical abstract

Comparative study on the anodizing process of Ti and Zr and oxide morphology

Metal anodizations have attracted much attention, but the formation mechanisms of the porous anodic oxides are still unclear. Compared with the Ti anodization, the anodization of Zr is relatively less studied. In order to compare the anodizing processes of Ti and Zr, a comparative study of Ti and Zr was carried out under the different voltages of anodizing process in the same mixed electrolyte of ammonium fluoride and phosphate acid. It was found that the structure and morphology of their nanotubes were very different. The anodizing curve of Ti showed a state of constant current. However, the anodizing curve of Zr did not show the state of constant current and ZrO2 nanotubes were still formed. This indicates that there is no equilibrium between oxide growth and dissolution in the anodization. TiO2 nanotubes show an orderly array of nanotubes, but ZrO2 nanotubes have three kinds of composite structures: nanoflower, nanotube and dense films. By comparing the great difference of current-time curves between the two anodizing processes, the composite structure of ZrO2 nanotubes are interpreted reasonably by combining electronic current theory and oxygen bubble mold.

Improving stability using a mixed ion/hybrid electrolyte strategy in a sodium ion capacitor

In Sodium-ion capacitors (SICs), employing high-capacity anodes based on alloying/conversion reactions can potentially alleviate the performance issues but are susceptible to rapid capacity fading due to consistent dissolution of the electrode surface by the electrolyte. Herein, we extend the “hybrid mixed electrolyte” strategy to ion capacitors for overcoming the rapid cycle decay issues in high-energy SICs: molybdenum disulphide (MoS2, MS) nanocrystals grown on carbon nitride (C3N4, CN), denoted as MS/CN, as anode exhibited remarkable performance in both sodium electrolyte and replaced with a hybrid mixed electrolyte comprising larger Na+ ions and smaller Li+ ions. Thus, constructed SICs exhibited a high energy density of 124 Wh Kg−1 with a mixed ion electrolyte, and low energy loss (71% retention after 40000 cycles) with a hybrid electrolyte (lower than conventional sodium-ion-based electrolyte: 37% retention after 15000 cycles). Systematic investigations, including X-ray photoelectron spectroscopy and electron probe microanalysis, revealed an advantageous formation of a stable interface for electrode and electrolyte.

The Origin of the Non-Constancy of the Bulk Resistance of Ion-Selective Electrode Membranes within the Nernstian Response Range.

The dependence of the bulk resistance of membranes of ionophore-based ion-selective electrodes (ISEs) on the composition of mixed electrolyte solutions, within the range of the Nernstian potentiometric response, is studied by chronopotentiometric and impedance measurements. In parallel to the resistance, water uptake by the membranes is also studied gravimetrically. The similarity of the respective curves is registered and explained in terms of heterogeneity of the membranes due to the presence of dispersed aqueous phase (water droplets). It is concluded that the electrochemical equilibrium is established between aqueous solution and the continuous organic phase, while the resistance refers to the membrane as whole, and water droplets hamper the charge transfer across the membranes. In this way, it is explained why the membrane bulk resistance is not constant within the range of the Nernstian potentiometric response of ISEs.