Protective Surface Layer Research Articles

Toward Optimization of the Chemical/Electrochemical Compatibility of Halide Solid Electrolytes in All-Solid-State Batteries

All-solid-state batteries (ASSBs) that rely on the use of solid electrolytes (SEs) with high ionic conductivity are the holy grail for future battery technology, since it could enable both greater energy density and safety. However, practical application of ASSBs is still being plagued by difficulties in mastering the SE–electrode interphases. This calls for a wide exploration of electrolyte candidates, among which halide-based Li+ conductors show promise despite being not stable against Li or LixIny negative electrodes, hence the need to assemble cells with a dual SE design. In the work described herein, we studied the electrochemical/chemical compatibility of Li3InCl6 against layered oxide positive electrode (LiNi0.6Mn0.2Co0.2O2, NMC622), carbon additive, and Li6PS5Cl under both cycling and aging conditions. Combining electroanalytical and spectroscopic techniques, we provide evidence for the onset of electrochemically driven parasitic decomposition reactions between Li3InCl6 and NMC622/carbon at lower potentials (3.3 V vs LiIn/In) than theoretically predicted in the literature. Moreover, to combat chemical incompatibility between dual SEs, we propose a new strategy that consists of depositing a nanometer-thick (1 or 2 nm) surface protective layer of Li3PO4 made by atomic layer deposition between Li3InCl6 and Li6PS5Cl. Through this surface engineering process with highly conformal and pinhole-free thin films, halide-based solid-state cells showing spectacular capacity retention over 400 cycles were successfully assembled. Altogether, these findings position halide SEs as serious contenders for the development of ASSBs.

Histological Study of Glandular Variability in the Skin of the Natterjack Toad-Epidalea calamita (Laurenti, 1768)-Used in Spanish Historical Ethnoveterinary Medicine and Ethnomedicine.

Simple SummaryCommon toads, including the natterjack toad (Epidalea calamita), have been used since ancient times for remedies, and thus constitute excellent biological material for pharmacological and natural product research. After a previous analysis of the historical-folk therapeutic use of amphibians in Spain, a histological study was carried out to provide a complementary ethnopharmacological view through the analysis of the integumentary heterogeneity of the serous (venom) and mucous glands from two adult specimens. Plastic-embedded semi-thin sections showed that serous/venom glands are cytologically homogeneous in spite of their genetic and biochemical complexity, leading to a cocktail that remains stored until extrusion. On the contrary, mucous glands, working continuously, show a more complex cytological variation and regional heterogeneity, which suggests an adaptive variability, leading to an invisible topographic map of skin toxicity. Natterjack toad-based folk remedies are usually extracted from the whole animal as a therapeutic unit in ethnoveterinary practice. However, a new ethnopharmacological vision could emerge from the study of tegumentary regional variation.Common toads have been used since ancient times for remedies and thus constitute excellent biological material for pharmacological and natural product research. According to the results of a previous analysis of the therapeutic use of amphibians in Spain, we decided to carry out a histological study that provides a complementary view of their ethnopharmacology, through the natterjack toad (Epidalea calamita). This species possesses a characteristic integument, where the parotoid glands stand out, and it has been used in different ethnoveterinary and ethnomedical practices. This histological study of their glandular variability allow us to understand the stages through which the animal synthesises and stores a heterogeneous glandular content according to the areas of the body and the functional moment of the glands. To study tegumentary cytology, a high-resolution, plastic embedding, semi-thin (1 micron) section method was applied. Up to 20 skin patches sampled from the dorsal and ventral sides were processed from the two adult specimens collected, which were roadkill. Serous/venom glands display a genetic and biochemical complexity, leading to a cocktail that remains stored (and perhaps changes over time) until extrusion, but mucous glands, working continuously to produce a surface protection layer, also produce a set of active protein (and other) substances that dissolve into mucous material, making a biologically active covering. This study provides a better understanding of the use of traditional remedies in ethnoveterinary medicine.

Aqueous-Based Post-Treatment of Li- and Mn-Rich Ncm

To achieve lithium-ion batteries with high energy density at competitive prices for automotive and large-scale applications, cathode active materials (CAMs) based on Li- and Mn-rich NCMs (LMR-NCMs), like Li1.14(Ni0.26Co0.14Mn0.60)0.86O2, are promising candidates.[1] However, LMR-NCMs still suffer from high gassing, particularly during cell formation, and detrimental voltage and capacity fading over their cycle life.[2,3] Different approaches can be utilized to try to mitigate these issues, such as the use of electrolyte additives, novel material designs (compositional gradients, etc.), or post-treatments.[4–7] In this study, we investigated the effect of a water-based post-treatment of LMR-NCM. It consists of a washing process of the LMR-NCM that results in a partial delithiation of its near-suface region by a lithium/proton ion exchange, while at the same time avoiding transition metal dissolution. A recalcination of this protonated near-surface layer of the LMR-NCM particles results in the formation of a protective spinel-like surface layer. We observed that after this treatment, the gassing during formation is decreased by »10-fold. Furthermore, the cycling performance of graphite/LMR-NCM full-cells is also drastically increased.By conducting on-line electrochemical mass spectrometry (OEMS) measurements, we analyzed the gas evolution of as-received and post-treated LMR-NCMs during the first activation cycle. It is known from the literature that the activation of LMR-NCMs is accompanied by a strong O2 and CO2 evolution during the first charge.[2] As seen in Figure 1, CO2 is evolved simultaneously with O2 from Li/LMR-NCM half-cells, prepared with untreated, as-received LMR-NCM (as-received, black line). With post-treated LMR-NCM, both CO2 and O2-evolution during the activation cycle are reduced by »10-fold (post-treated, green line). Only a small amount of the first-charge capacity (<10%) is lost due to the post-treatment, as seen in Figure 1a, reflecting the slight extent of delithiation that is part of the post-treatment.As will be shown, cycling tests of graphite/LMR-NCM full-cells with a post-treated LMR-NCM reveal a greatly increased cycling stability in comparison to cells with an as-received material. Using TGA-MS, XPS and ICP-OES, we further elucidate the beneficial mechanism of the here developed water-based post-treatment.

Electrochemical Birch Reduction: A Molecular-Level Venture into the Solvation Structure at the Electrode Interface

Although selective hydrogenation of aromatics through Birch reduction has long been at the heart of synthetic organic chemistry, its various proposed procedures suffer from monumental challenges. The optimized design of salt, solvent, and additives along with a sacrificial anode material has enabled the recent success of Electrochemically driven Birch reduction (E-Birch) reactions, which are procedurally convenient, safe, and sustainable1. The E-Birch reactions are premised upon the concepts applied in Li-ion battery research regarding the surface protection layer formation, also referred as the solid electrolyte interphase (SEI). However, the impacts of these constituents on the surface layer formation in E-Birch reactions is largely unknown. In this study, we have employed a combination of molecular dynamics (MD) simulations and density functional theory (DFT) calculations to provide insights into the liquid structure and the interactions of these constituents, both in bulk of the solution and at the electrode surface. Specifically, an optimal electrolyte design of LiBr salt in tetrahydrofuran (THF) solvent, with 1,3-dimethylurea (DMU) as the proton donor, and tris(pyrrolidino)phosphoramide (TPPA), as surface protector, has been studied as it promoted high yields of 1,4-diene formation from several aromatic-ring containing molecules with a variety of functional groups. We have found that THF, DMU, and TPPA are all present in the Li+ solvation sheath at the bulk of the solution and at the electrode surface. Since the surface layer is formed by the reduction reactions of solution, the reduction voltage was computed for representative solvation structures. It was found that the reduction voltage and reduction process of THF, DMU, and TPPA were altered by the Li+ coordination and are therefore sensitive to the liquid solution structures. In addition, we have demonstrated that the species in the solvation shell can undergo bond breaking events, which lead to protection layer formation at the electrode surface. The role of salt, solvent, additives, and sacrificial anodes in altering the solution structure and reduction reactions was further discussed. References Peters Byron, K.; Rodriguez Kevin, X.; Reisberg Solomon, H.; Beil Sebastian, B.; Hickey David, P.; Kawamata, Y.; Collins, M.; Starr, J.; Chen, L.; Udyavara, S.; Klunder, K.; Gorey Timothy, J.; Anderson Scott, L.; Neurock, M.; Minteer Shelley, D.; Baran Phil, S., Scalable and safe synthetic organic electroreduction inspired by Li-ion battery chemistry. Science 2019, 363 (6429), 838-845.

The vaginal microbiota

The vagina is an ecosystem consisting of various species of microorganisms (microbiota) that play important role in maintaining vaginal health. The vaginal ecosystem includes a variety of species classified into aerobic and anaerobic microorganisms which are vaginal microbiota (VMB). In the vagina of a healthy woman, 70% of normal microbiota is dominated by the Lactobacillus species. Lactobacillus is a Gram-positive, anaerobic bacterium, and belongs to the group of lactic acid bacteria (LAB). LAB produces lactic acid which plays a role in maintaining vaginal acidity at pH &lt;4, producing H2O2 and bacteriocin, modulating non-specific immune responses, and preventing colonization of microorganisms through competitive adhesion in the vaginal epithelium. The composition of the VMB can vary between women and can change dramatically in a short time in the same individual. Over the past several decades, it has been known that a significant shift from the normal number of VMB colonies affects the integrity of the mucosal surface protective layer. The imbalance of VMB colonies and their effects on the vagina can cause an increased risk of sexually transmitted infections (STI) including bacterial vaginosis, vulvovaginal candidiasis, gonorrhea, trichomoniasis, Chlamydia trachomatis infection, herpes simplex virus (HSV) infection, bacterial vaginosis infection, vulvovaginal candidiasis, gonorrhea, trichomoniasis, Chlamydia trachomatis infection, herpes simplex virus (HSV) infection, human papillomavirus infection (HPV), and human immunodeficiency virus (HIV) infection. Keywords: Lactobacillus, STI, vaginal microbiota

Developmental Plasticity of the Amphibious Liverwort Riccia fluitans.

The colonization of land by ancestors of embryophyte plants was one of the most significant evolutionary events in the history of life on earth. The lack of a buffering aquatic environment necessitated adaptations for coping with novel abiotic challenges, particularly high light intensities and desiccation as well as the formation of novel anchoring structures. Bryophytes mark the transition from freshwater to terrestrial habitats and form adaptive features such as rhizoids for soil contact and water uptake, devices for gas exchange along with protective and repellent surface layers. The amphibious liverwort Riccia fluitans can grow as a land form (LF) or water form (WF) and was employed to analyze these critical traits in two different habitats. A combination of light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies was conducted to characterize and compare WF and LF morphologies. A complete phenotypic adaptation of a WF plant to a terrestrial habitat is accomplished within 15 days after the transition. Stable transgenic R. fluitans lines expressing GFP-TUBULIN and mCherry proteins were generated to study cell division and differentiation processes and revealed a higher cell division activity in enlarged meristematic regions at LF apical notches. Morphological studies demonstrated that the R. fluitans WF initiates air pore formation. However, these pores are arrested at an early four cell stage and do not develop further into open pores that could mediate gas exchange. Similarly, also arrested rhizoid initial cells are formed in the WF, which exhibit a distinctive morphology compared to other ventral epidermal cells. Furthermore, we detected that the LF thallus has a reduced surface permeability compared to the WF, likely mediated by formation of thicker LF cell walls and a distinct cuticle compared to the WF. Our R. fluitans developmental plasticity studies can serve as a basis to further investigate in a single genotype the molecular mechanisms of adaptations essential for plants during the conquest of land.

Plutonic Rocks as Protection Layers to Concrete Exposed to Ultra-High Temperature.

Concrete structures perform poorly when withstanding thermal shock events, usually requiring repair or replacement after one single instance. In certain industries (such as petrol, metallurgic and ceramics), these events are not only likely but frequent, which represents a considerable financial burden. One option to solve this issue would be to decrease the heating rate imposed onto the concrete material through the use of a protective surface layer. In this work, the suitability of dunite and microgabbro as protective materials is explored through X-ray diffraction, thermal dilation, optical microscopy, X-ray microtomography, thermo-gravimetric analysis and a compressive test. Further, the thermal dilation was used as an input to simulate a composite concrete-rock wall and the respective stresses caused by a thermal shock event. The dehydration of chrysotile in dunite and the decomposition of analcime, chamosite and pumpellyite in microgabbro were both favourable for the performance of the stones in the desired application. The thermal stability and deformation were found in the range of what can be applied directly on concrete; however, it was clear that pre-heating treatment results in a far more durable system in a cyclic thermal load situation.

Renal-clearable dye-conjugated silver nanoparticles for in vivo plasma biothiol sensing through urinalysis

The attractive physical and chemical properties of silver nanoparticles (AgNPs) have enabled their applications in many sectors such as medicine and sensing. Here, we report an ultra-stable AgNPs-based platform for real-time in vivo plasma biothiol sensing through a facile urinalysis. The platform is created by conjugating a renal-clearable organic dye, TAMRA, as a protecting surface layer on glutathione (GSH)-coated AgNPs. This AgNPs-based platform is stable in aqueous solution for at least 4 months; while upon interactions with biothiols like GSH, a 24-fold increase in fluorescence intensity and a 30 nm red shift in UV-Vis spectra can be achieved. After intravenous (i.v.) injection, the AgNPs-based platform can be activated by plasma biothiols. The successful fluorescent imaging of mouse bladder and the following UV-Vis analysis of urine samples at different time points post i.v. injection proved the AgNPs-based platform an efficient tool for plasma biothiol sensing through urinalysis. Taken together, this approach offers a practical pathway for diagnosis of biothiol-associated diseases in clinics, and the synergistic effects generate from the combination of dyes and AgNPs enable them for further in vivo monitoring and detection.

Corrosion resistant and high-strength dual-phase Mg-Li-Al-Zn alloy by friction stir processing

Magnesium is the lightest structural metal, and alloying with lithium makes it even lighter. However, multi-phase Mg-Li alloys typically undergo rapid corrosion, and their strength decreases at room temperature due to natural age-softening. Here, we engineer a rapidly degrading dual-phase Mg-Li-Al alloy to be durable via friction stir processing followed by liquid CO2 quenching. The best performing alloy has a low electrochemical degradation rate of 0.72 mg·cm−2· day−1, and high specific strength of 209 kN·m·kg−1. We attribute this electrochemical and mechanical durability to its microstructure, which consists of a refined grain size of approximately 2 µm and dense nanoprecipitates. This microstructure suppressed the formation of the detrimental AlLi phase, and an aluminium-rich protective surface layer also formed. This processing route might be useful for designing lightweight and durable engineering alloys.

Interaction of beryllium with 316H stainless steel in molten Li2BeF4 (FLiBe)

The increased demand in renewable energy resources has led to a renewed interest in nuclear reactors including a new generation of molten salt reactors. One of the issues encountered in handling of molten chloride or fluoride salts is the inability of metals to form and retain a protective oxide surface layer, generally chromium oxide. The low chromium content, nickel-based alloy INOR-8, later marketed as Hastelloy N, was specifically developed to contain molten fluorides. This alloy had some deficiencies, but its composition resulted in it incurring far less chromium depletion by the molten fluoride salts than alloys like 316 stainless steel. For the next generation of molten salt reactors, an alloy with pressure vessel code approval and higher temperature capability than Hastelloy N is required. Consequently, several reactor designers have reportedly chosen to build the reactor containment vessel from 316H stainless steel. In order to minimize corrosion of the stainless steel by the molten fluoride salt (2LiF-BeF2), it is proposed to add beryllium metal to the salt to react with impurities and provide a means to lower the oxidation potential thus making the salt less corrosive. However, there is a concern whether the beryllium would react with components of the stainless steel. To address this concern, static capsule tests were conducted in which selected amounts of beryllium were added to capsules containing 2LiF-BeF2 (FLiBe) salt and 316H stainless steel and Hastelloy N samples. Following exposure, the samples were cleaned and examined using a variety of analysis techniques including, optical microscopy, SEM-EDS, XPS, LIBS, XRD and EPMA. Tensile samples were also exposed in capsules, and those were subjected to tensile testing. It was found that for the level of beryllium additions used in this study, intermetallic compounds were formed which could be detrimental to the long-term performance of the 316H stainless steel.

Ultra-broadband nearly perfect absorbers based on graphene-coated lossy metallic nanostructures

In this paper, we present a new thin-film broadband nanostructured metamaterial absorber based on a graphene-coated plasmonic lossy metal–insulator–metal. Using the finite element method, we study the absorption properties of the proposed nanostructure and demonstrate the possibility of achieving an ultrabroad absorption spectrum by combining graphene and lossy metals. We demonstrate that graphene coating of the lossy metallic nano-disks improves the average absorption of the metamaterial by more than 10% while acts as a surface protection layer for the lossy metal films. Using the optimized design parameters and owing to the resonance coupling, a broad absorption from 400 nm to 2300 nm, particularly in the near-infrared region from 700 nm to 2000 nm, with a nearly flat absorption curve and an average absorption of 95.25% and a maximum absorption of 99.94% can be achieved. Other advantages of the proposed optical nano-absorber based on lossy metals instead of gold and silver include higher melting point (1668 °C compared to 1064 °C), the lower production cost of the metamaterial by using alternative materials, polarization insensitivity of the structure, and relative insensitivity to the radiation angle. In particular, the absorber maintains nearly an average of 90% absorptivity as the light incident angle reaches 30°. The proposed graphene-coated absorber demonstrates broader and stronger absorption, and much higher structural meting point compared to the previously reported thin-film based broadband absorbers, resulting in a viable platform for broadband applications with higher stability and durability.

Surface and Interface Engineering of Zn Anodes in Aqueous Rechargeable Zn-Ion Batteries.

Rechargeable zinc-ion batteries (ZIBs) have shown great potential as an alternative to lithium-ion batteries. The ZIBs utilize Zn metal as the anode, which possesses many advantages such as low cost, high safety, eco-friendliness, and high capacity. However, on the other hand, the Zn anode also suffers from many issues, including dendritic growth, corrosion, and passivation. These issues are largely related to the surface and interface properties of the Zn anode. Many efforts have therefore been devoted to the modification of the Zn anode, aiming to eliminate the above-mentioned problems. This review gives a comprehensive summary on the mechanism behind these issues as well as the recent progress on Zn anode modification with focus on the strategies of surface and interface engineering, covering the design and application of both the Zn anode supports and surface protective layers, along with abundant examples. In addition, the promising research directions and perspective on these strategies are also presented.

Inhibitive effect of sodium molybdate on corrosion of AZ31 magnesium alloy in chloride solutions

In this work, corrosion inhibition of the AZ31 magnesium alloy was investigated in NaCl solutions containing different amounts of sodium molybdate inhibitor. Electrochemical, hydrogen evolution, microscopic, and spectroscopic experiments were utilized to examine the mechanism of corrosion inhibition by molybdates. The results showed that Na2MoO4 inhibitor provides reliable inhibition at high concentrations (150 mM). Surface examination by Raman and XPS spectroscopy confirmed the formation of a protective surface layer of mixed Mo(VI, V, IV) species. Based on these results, the mechanism of corrosion inhibition of the AZ31 alloy by aqueous molybdates was proposed.

Evaluation of corrosion inhibition performance of thiazolidine-2,4-diones and its amino derivative: Gravimetric, electrochemical, spectroscopic, and surface morphological studies

To produce effective, less expensive molecules with minimum impact on the environment, the study aims to develop green corrosion inhibitors, which can significantly protect mild steel during its pickling and descaling treatment. Therefore, the present study describes the corrosion inhibition performance of two thiazole derivatives, namely thiazolidine-2,4-diones and its amino derivative 2-aminothiazolidin-4-one designated as TZD, and AT, respectively mild steel in 5%HCl solution through gravimetric measurement, electrochemical measurement (open circuit potential, electrochemical Impedance Spectroscopy, and potentiodynamic polarization). The spectroscopic measurement like FT-IR, UV–vis, X-ray photoelectron spectroscopy (XPS) along with surface morphological analysis like scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and atomic force microscopy (AFM) was also carried out. Gravimetric studies suggested that the inhibitory effects of the proposed compounds improves with an increase in the concentration of TZD and AT and solution temperature, having the most significant efficiencies of 98.0% and 99.7%, respectively, at 5 × 10−4 M at 60 °C. According to electrochemical tests, the analyzed inhibitor molecules function as mixed-type corrosion inhibitors and improve corrosion charge transfer resistance. AFM, SEM, and EDS investigations indicated that TZD and AT molecules adhere and construct a surface protective layer.

Crack control for repair and strengthening of reinforced concrete structures using the multi-cracking behaviour of Ultra-high Performance Fibre Reinforced Shotcrete (UHPFRSC)

Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) is an innovative material for the repair and/or strengthening of reinforced concrete structures. In the field of traffic infrastructure, the outstanding mechanical properties are used as a protective surface layer and to increase the load capacity of the structure. UHPFRC is characterised by a dense granular structure and correspondingly high resistance against chloride attack. The material is typically applied as cast in-situ concrete. To optimise implementation of the strengthening and repair method, the UHPFRC is applied as sprayed concrete, so-called Ultra-High Performance Fibre Reinforced Shotcrete (UHPFRSC). The research aims to increase the service life of damaged and/or overloaded structures. Crack widths in the UHPFRSC layer must be limited to avoid migration of chlorides. The thin UHPFRSC layer provides crack distribution and control of localised macro cracks in the existing reinforced concrete structure. The fibres in the Ultra-High Performance Shotcrete (UHPSC) allows for limiting the crack width to 50 µm. When the UHPFRSC is applied on cracked reinforced concrete, it can be assumed that multi-cracking in the UHPFRSC surface layer will provide a chloride-dense layer equivalent to a coating. Under load, the two layers - UHPFRC and RC - act as a composite. For structural analysis, a particular focus must be placed on the interaction between cementitious materials. In addition, the pre-damage and pre-loading of the existing structure will influence the structural behaviour and crack formation. The paper presents the results of bending tests of UHPFRC - RC composite elements. The investigation shows the outstanding crack control behaviour of UHPFRSC. Based on this investigation, an analytical model will be provided, and a calculation of the crack widths will be derived. The research presents a central aspect of a large interdisciplinary research project at Munich University of Applied Science, called i-SCUP.

Corrosion inhibition of aluminum in 1 M HCl by novel pyrimidine derivatives, EFM measurements, DFT calculations and MD simulation

• Pyridine-pyrimidine derivatives inhibit aluminum corrosion in the protonated form. • Adsorption of inhibitors is spontaneous and is physical–chemical adsorption. • Characteristic molecular parameters are explored using DFT and MD. • Surface analysis results indicate the presence of a protective surface layer. • EMMD has the greatest inhibition efficiency theoretically and experimentally. Four pyridine-pyrimidine derivatives, namely pyridine-2,6-diamine (PD), pyrimidine-2-amine (PA), 6-amino-3,4-dihydropyrimidine-2(1H)-thione (ADT) and ethyl (R)-6-(4-chlorophenyl)-2-mercapto-4-methyl-1,6-dihydropyrimidine-5-carboxylate (EMMD) are used as effective inhibitors for aluminum corrosion in 1 M HCl solution. The anti-corrosive potential of these heterocyclic compounds has been evaluated by electrochemical frequency modulation (EFM) method, The inhibition efficiency of these inhibitors was strongly associated to the concentration (10 −7 –10 −3 M) and the structure of the molecules; reached a maximum of 95.68% for EMMD at 10 −3 M owing to more anchoring functional groups. The effect of temperature on the corrosion behaviour was assessed at solution temperature range 298–323 K. The four inhibitors adsorbed according to the Langmuir’s adsorption isotherm. Thermodynamic activation parameters for the dissolution process of aluminum in 1 M HCl and inhibited solutions were calculated and discussed. Surface analysis (SEM, EDX, and AFM) confirmed the formation of a protective layer adsorbed on the aluminum surface. In addition, theoretical studies by DFT and MD revealed the correlation between the molecular chemical structure of studied inhibitors and their inhibition efficiency. The adsorption mechanism is revealed by theoretical calculations.

Electrochemical characteristics of aluminum amorphous alloys modified by oligomeric coatings in different media

Amorphous Al-based alloys are strong, ductile and corrosion resistant. They are used widely in various fields. Oligomeric films are used to modify amorphous alloys. Еlectrochemical characteristics of amorphous metal alloys Al 87,0 Gd 5,0 Ni 8,0 and Al 87,0 Gd 5,0 Ni 4,0 Fe 4,0 in aqueous-ammonia solution of oligoperoxide (OP) based on vinyl acetate, 2-tert-butylperoxy-2-methyl-5-hexen-3-yne and maleic anhydride was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The affinity of the oligomeric coating to metal surfaces was evaluated based on the value of the wetting (cosθ) with respective solutions and the calculated values of the work of adhesion. Higher adhesion activity of contact surfaces of tapes to oligoperoxide solutions is observed. The formation of protective surface layers is indicated by the change in the electrochemical parameters of samples of amorphous alloys Al 87 Gd 5 Ni 8 and Al 87 Gd 5 Ni 4 Fe 4 in a medium of 1 % aqueous-ammonia solution of oligoperoxide, namely the expansion of the passive region on the current-voltage curve, indicates. The oligoperoxide layer formed on the surface of the alloy obtained with Fe additives shows greater resistance to polarization. The strength of oligoperoxide layers formed on the surface of aluminum amorphous alloys in 0.1 M NaCl (aq.) was estimated. For Al 87 Gd 5 Ni 8 we observed a shift of corrosion potentials to the anode side, some decrease in corrosion currents and polarization resistance. In the case of Al 87 Gd 5 Ni 4 Fe 4 , the corrosion potential is slightly shifted to the cathode side, and the value of the polarization resistance is 2-6 times higher, which confirms the higher affinity of the oligoperoxide layers. The results of studies of modified samples by electrochemical impedance spectroscopy showed that on the surface of the amorphous alloy Al 87 Gd 5 Ni 4 Fe 4 in aqueous-ammonia solution OP on the surface formed a highly conductive layer of oligoperoxide. It shows low charge transfer resistance, which changes very little during electrochemical studies in 0.1 M aqueous sodium chloride solution. Keywords : amorphous metallic alloy, aluminum, electrochemical characteristics, oligomeric coatings.

Anticorrosive nanosized LiF thin film coating for achieving long-cycling stability of LiCoO2 at high voltages

The mutability of layered structures and unfavorable side reactions between cathodes and traditional electrolytes are barriers for the commercialization of LiCoO2 (LCO) at high voltages (above 4.2 V). Metal fluorides, owing to their effective passivation effect, have been considered promising coating materials for various electrochemical applications. As a chemical stability species, LiF can combine the advantages of fluorides with those of lithium without introducing extra elements. In this study, we deposited a uniform nanosized LiF thin film coating onto the LCO particles by coprecipitation to enhance the reversible capacity and cycle stability of the LCO batteries at high voltage. Electrochemical tests indicated that at room temperature, the LCO@LiF cell exhibited an excellent capacity retention with 71.4% after 300 cycles, which is higher than that of many reported oxide and fluoride coatings for LCO at high voltage. This study demonstrated that LiF, an outstanding cathode surface protection layer, can hamper the immediate contact of LCO with the electrolyte, stabilize the LCO surface structure, and successfully protect the cathode from corrosion by the electrolyte. Consequently, a significant enhancement of the electrochemical properties of the LiF-coated LCO was observed. This study provides a facile commercial approach for the mass production of high-voltage LCO cathodes.

Controlled Deposition of Zinc-Metal Anodes via Selectively Polarized Ferroelectric Polymers.

Aqueous zinc-ion batteries are regarded as ideal candidates for stationary energy-storage systems due to their low cost and high safety. However, zinc can readily grow into dendrites, leading to limited cycling performance and quick failure of the batteries. Herein, a novel strategy is proposed to mitigate this dendrite problem, in which a selectively polarized ferroelectric polymer material (poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))) is employed as a surface protective layer on zinc anodes. Such a polarized ferroelectric polymer layer can enable a locally concentrated zinc-ion distribution along the coated surface and thus enable the horizontal growth of zinc plates. As a result, symmetrical zinc batteries using such anodes exhibit long cycling lifespan at 0.2mA cm-2 , 0.2 mAh cm-2 for 2000 h, and a high rate performance up to 15mA cm-2 . Also, the full cell (including a Zn-MnO2 battery and a zinc-ion capacitor) based on this anode is demonstrated. This work provides a novel strategy to protect the zinc anode and even other metal anodes exploiting polymer ferroelectricity.

A facile surface passivation strategy for Na2SiF6:Mn4+,Li+ phosphors to achieve high moisture resistance and luminescent thermal stability

Recently, Mn4+-doped fluoride red phosphors become widely used as red emitting components of WLEDs (white light-emitting diodes), but such phosphors are easy to hydrolyze in humidity environment and it limits their application. Herein, LNSF:Mn4+-CA (LNSF: Mn4+ = Na2SiF6: 0.066Mn4+,0.06 Li+, CA = passivation with citric acid solution) with high water resistance, luminescent thermal stability and luminescent intensity was synthesized though the H2O2-free hydrothermal method and surface passivation process. The water resistance, luminescent thermal stability and luminescent intensity are obviously enhanced by surface passivation. The high thermal stability is caused by strong negative thermal quenching (NTQ). The mechanism of the strong NTQ is attributed to the increase of electron traps after surface passivation. Furthermore, mechanism for improvement of water resistance is suggested as that a homogeneous Mn4+-rare surface protective layer is in situ formed on surface of the sample after surface passivation. The layer isolates external moisture and then makes the sample resistive to interaction with water. Improvement of water resistance is demonstrated as that after immersing in water for 6 h (0.25 day), luminescent intensity of the un-passivation sample drops to 42.73% of the initial one, while that of the passivation sample remains to have 92.33% of its initial one. The prototype WLEDs with good luminescent performances (CCT = 3916 K and Ra = 89.6) was assembled by using the optimal coated sample. The results suggest that the optimal passivated sample is potential red emitting phosphor for the application in blue-based warm WLEDs.