Thin Functional Layer Research Articles

Lithium aluminium titanium phosphate based ceramic composite membrane for selective lithium-ion separation via a scalable membrane-based electrodialysis process

The escalating global demand for lithium necessitates efficient extraction methods, particularly from natural sources such as brine. Herein, we report a novel, thin, and dense functionalised composite ceramic membrane that is employed in conjunction with electrodialysis technology for selective lithium extraction from salt lakes. This membrane exhibits high mechanical strength, low ionic impedance, and high lithium conductivity. The thin functional layer, ~20 μm-thick NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) superionic conductor material, is deposited on high-strength and porous alumina membrane via a facile dip-coating method, providing structural stability for the composite membrane. The preparation and sintering processes of LATP-Al2O3 ceramic composite membrane were systematically studied and precisely controlled to improve its morphology and performance. A membrane-based electrodialysis set-up was designed specifically for lithium extraction demonstrated the remarkable performance of the composite-LATP membrane in separating lithium from magnesium-lithium solutions with a high Mg/Li ratio. The LATP composite membrane effectively reduced the Mg/Li ratio from 40 to 2.1 after three-stage electrodialysis. Moreover, the Li+ recovery reached 77.15% from the feed solution with an estimated power consumption of ~47.6 kWh per 1 kg of lithium carbonate. These findings have significant implications for the development of low-cost and environmentally friendly inorganic membrane separation technologies, which are important for promoting technological innovation in the lithium industry chain.

PEI@MOFs thin film nanocomposite (TFN) membrane for efficient CO2 separation

Polyetherimide (PEI) membrane exhibits high CO2 selectivity while suffer from low permeance thus limiting the further application in CO2 separation. Thin film nanocomposite (TFN) membrane which contains a thin selective functional layer with nanomaterials porous fillers is a new class of high-performance membranes. In this work, a series of novel PEI@MOFs TFN membranes were prepared for efficient CO2 separation. The sub-micro scale PEI layers (about 400 nm) with four kinds of MOFs fillers including 3-dimensional MOFs nanoparticles (UiO-66 and MIL-101 (Cr)) and MOFs nanosheets (2-D CuBDC and Zn2(bim)4) were prepared by a simple spin-coating strategy. The properties and CO2 separation performance of the TFN membranes were further studied. The MOFs in PEI increased the diffusion coefficient and selectivity for CO2, at the same time, the ultra-thin functional layer maximized reducing the CO2 transport resistance. As a result, the PEI@MOFs TFN membranes exhibited high CO2 permeance as well as enhanced CO2 separation performance which close to the Robeson upper bound. The PEI@CuBDC TFN membrane exhibited CO2 permeance of 15.6 GPU (3.3 times higher than the neat PEI membrane), and the selectivity of CO2/CH4 reached 39.8 (2.2 times higher than the neat PEI membrane). In addition, the PEI@MOFs TFN membranes showed good thermal and operation stability.

Interface Resistance Analysis in Solid Oxide Fuel Cells

A sophisticated design of the interface structure between the cathode and the electrolyte is essential to improve the performance of solid oxide fuel cells (SOFCs). It is because the interface is the place where it directly affects both the ohmic resistance and the polarization resistance as interface contact and interface reaction, respectively. To improve interface properties, electrolyte surface treatment or inserting interface functional layer between the cathode and the electrolyte have been applied. They improved cell performance by effectively enhancing the interfacial characteristics such as interface bonding and interface reaction area. However, although both ohmic and polarization resistance greatly contributed to the improved cell performance, a detailed analysis related to ohmic resistance compared to polarization resistance is insufficient. Unlike polarization resistance which can quantify interface reaction related resistance using distribution of relaxation time (DRT) model, there is no proper methodology to quantify interface resistance in the case of ohmic resistance. The interface resistance has been analyzed to the extent that it belongs to the remaining resistance except for the electrolyte resistance from total ohmic resistance in consideration of the ionic conductivity and thickness of the electrolyte, which still not completely separate the interface resistance from the total ohmic resistance. Furthermore, in recent years, the electrolyte thickness has gradually decreased to less than 5 μm for high-performance and the electrolyte resistance has been significantly reduced, increasing proportion of interface resistance in total ohmic resistance. Therefore, we need to reduce the interface resistance for further cell improvement. Also, quantifying the interface resistance and having a deeper understanding of the correlation between interface resistance and interface structure should be supported.Here, to realize the interface resistance from the ohmic resistance, we designed several types of interface structure using electrostatic spray deposition (ESD) which can precisely control the particle size and be used to fabricate a thin functional layer. Using the different interface properties and equivalent circuit models, we separate the interface resistance from the ohmic resistance quantitatively. Our results can suggest a simple and effective interface analysis method for achieving high performance SOFCs. Figure 1

Green Solvent Ethanol-Based Inks for Industrially Applicable Deposition of High-Quality Perovskite Films for Optoelectronic Device Applications.

Incontrovertibly there is an increasing demand for the development of benign inks suitable for fabrication of high-performing perovskite-based thin film functional layers. Nevertheless, most reported perovskite precursors rely on the use of highly toxic solvents such as acetonitrile, 2-methoxyethanol, dimethylformamide, and many others. Hence, there is a strong imperative for the development of novel and greener inks, which will facilitate smoother commercialization of technologies based on functional perovskite films. Therefore, four perovskite precursors are studied, some of which consist of up to 90% ethanol. All inks are developed to fulfill the requirements of a high-throughput deposition compatible with roll-to-roll techniques at room temperature, assisted by an air knife for instant solvent removal. Two of the inks are particularly suitable for the fabrication of high-quality and densely packed multi-crystalline (CH3 NH3 )PbI3 layers, as confirmed by numerous nanoscale spectroscopic and material characterization techniques. Additionally, large-area photoluminescence (PL) imaging is demonstrated to improve the quality of the deposited perovskite films, with a route to enhance deposition uniformity when upscaling for manufacture. The genuine potential of the developed greener perovskite inks is demonstrated with the fabrication of solar cells with power conversion efficiencies above 19.5%.

Preparation and stability enhancement of anchor bonded 3D-network extracting membrane for nickel extraction

A novel and efficiently anchored 3-dimensional network extracting membrane (3D-NEM) with a thin functional surface layer comprising extraction carrier Bis(2-ethylhexyl) phosphate (D2EHPA) for nickel extraction was designed and studied in this paper. The active sites on the supporting Polytetrafluoroethylene (PTFE) hydrophilic ultrafiltration membrane were introduced by treating PTFE surface with potassium permanganate. Polydimethylsiloxane (PDMS) and Polymethylhydrosiloxane (PMHS) were applied to prepare a 3D network layer which is tightly anchored to the PTFE surface by introducing a crosslinking agent vinyltriethoxysilane (VTES). The prepared 3D-NEM was characterized by SEM, EDS, ATR-IR, XPS and etc. The influence of preparation parameters of 3D-NEM was studied and compared systematically. The optimum preparation conditions of 3D-NEM were based on a PDMS/PMHS/VTES ratio of 2:1:0.1 and a total polysiloxane concentration of 8 wt%. The operation stability test confirmed the average flux of the 3D-NEM in 72h reached 1871.16 mg·m-2·h-1, and only 14.42% flux declined at the end of operation. The proposed designed 3D network structure produced a 5.5 μm-functional extracting layer which has benefits in both effective fixing of D2EHPA and tight anchor to the supporting surface. This work has dual advantages in improving flux and reducing extractant loss compared to supported liquid membrane (SLM) and polymer inclusion membrane (PIM) processes.

Modification of Battery Separators via Electrospinning to Enable Lamination in Cell Assembly

To meet the requirements of today’s fast-growing Li-ion battery market, cell production depends on cheap, fast and reliable methods. Lamination of electrodes and separators can accelerate the time-consuming stacking step in pouch cell assembly, reduce scrap rate and enhance battery performance. However, few laminable separators are available on the market so far. This study introduces electrospinning as a well-suited technique to apply thin functional polymer layers to common battery separator types, enabling lamination. The method is shown to be particularly appropriate for temperature resistant ceramic separators, for which stable interfaces between separator and electrodes were formed and capacity fading during 600 fast charging cycles was reduced by 44%. In addition, a straightforward approach to apply the method to other types of separators is presented, including separator characterization, coating polymer selection, mechanical tests on intermediates and electrochemical validation in pouch cells. The concept was successfully used for the modification of a polyethylene separator, to which a novel fluoroelastomer was applied. The stability of the electrode/separator interface depends on the polymer mass loading, lamination temperature and lamination pressure, whereas poorly selected lamination conditions may cause damage on the separator. Appropriate adhesion force of 8.3 N/m could be achieved using a polymer loading as low as 0.25 g/m2. In case separator properties, coating polymer, morphology of the fibrous coating and lamination conditions are well adjusted to each other, the implementation of electrospinning and lamination allows for faster, more flexible and robust pouch cell production at comparable or better electrochemical cell behaviour.

Flame coatings by CCVD (Pyrosil) for R2R applications

Flame coatings by CCVD (Pyrosil) for R2R applications

Functionalized 12µm Polyethylene Separator to Realize Dendrite-Free Lithium Deposition toward Highly Stable Lithium-Metal Batteries.

Direct application of metallic lithium (Li) as the anode in rechargeable lithium metal batteries (LMBs) is still hindered by some annoying issues such as lithium dendrites formation, low Coulombic efficiency, and safety concerns arising therefrom. Herein, an advanced composite separator is prepared by facilely blade coating lightweight and thin functional layers on commercial 12 µm polyethylene separator to stabilize the Li anode. The composite separator simultaneously improves the Li ion transport and lithium deposition behaviors with uniform lithium ion distribution properties, enabling the dendrite‐free Li deposition. As a result, the lithium anode can stably cycle up to 3000 cycles with the high capacity of 3.5 mAh cm−2. Moreover, the composite separator exhibits wide compatibility in LMBs (Li–S and Li‐ion battery) and delivers stable cycling performance and high Coulombic efficiency both in coin and lab‐level soft‐pack cells. Thus, this cost‐effective modification strategy exhibits great application potential in high‐energy LMBs.

Engineering novel high-flux thin-film composite (TFC) hollow fiber nanofiltration membranes via a facile and scalable coating procedure

A novel defect-free polyamide/(polyether sulfone/poly(vinylidene fluoride)) PA/(PES/PVDF) thin-film composite (TFC) hollow fiber membrane (HFM) with desirable separation characteristics were developed through a facile and scalable coating procedure. By the introduction of piperazine (PIP) monomers into the PES coating solutions, the functional monomer-enriched PES coating layer was formed on the shell side of porous matrix-reinforced hollow fiber (HF) support through phase inversion process. Subsequently, PIP and TMC was interfacial polymerized during the fiber coating line to form a thin and defect-free polyamide (PA) functional layer for TFC HFM with high water permeability. Furthermore, the introduction of aqueous monomers only into the PES layer allowed economizing the cost of membrane manufacturing compared with bulk modification of the membrane substrate. Interestingly, the formation of bowl-like structures endowed the separation layer with higher permeation surface area and thus favored high water permeability. On combining these separation features, the optimized TFC membranes presented a high pure water permeability (PWP) of 13.8 L·m−2·h−1·bar−1, approximately twice than that of conventional TFC membrane, with a satisfying Na2SO4 rejection of 98.2%. Moreover, the PA/(PES/PVDF) TFC HFM exhibited excellent stability, backwash ability and anti-fouling ability, suggesting its huge potential for the water purification. Compared with the conventional two-step IP process on flat sheet membrane, the in-situ IP procedure performed on HF greatly simplifies the manufacturing process, shortens the production period and reduces monomer usage while the high packing density and great surface area per unit volume are obtained. This work may provide a simple and economical strategy for engineering high-performance TFC HFM.

Multiplexing temperature-compensated open-cavity Fabry-Perot sensors at a fiber tip.

We investigate multiplexing of four highly sensitive Fabry-Perot (FP) microresonators at the tip of a single-mode optical fiber for refractive index (RI) measurements with simultaneous temperature compensation. The individual sensing elements for RI or temperature consist of either open-cavity FP resonators or solid fiber core regions fabricated by diamond-blade dicing of single-mode optical fibers, respectively. The reflectivity of the open resonators is further enhanced by matched dielectric coatings. At the same time, the solid core resonators formed by the fiber pieces between the open cavities are used as thermometers. This allows immediate compensation for temperature cross-sensitivity during RI measurements. The general performance of the sensor is demonstrated by measuring the RI of sucrose solutions, where we use phase tracking of the characteristic Fourier transform components of the backreflected optical spectrum for evaluation. The temperature sensitivity is on average 20±/∘C with an accuracy of 0.01°C, fully sufficient for biomedical applications. Meanwhile, the four RI sensing (open) cavities show high sensitivity of approximately 1160 nm/RIU. Due to the compact size of the sensor, small spatial inhomogeneities of RI can be accurately detected. If the cavities are additionally filled with molecularly imprinted polymers or coated with thin functional layers, they could also be used for the detection of trace substances in biomedical laboratory-on-a-fiber applications.

Fabrication and Characterization of Thin-Film SOFC Supported by Microchannel-Structured Zirconia Substrate for Direct Methane Operation

Ni-cermet anode demonstrates excellent catalytic activity and electrical conductivity but suffers from carbon deposition issue. To utilize Ni-cermet anode while preventing carbon deposition, a synergic strategy is employed to design anode electrode. In particular, Zr is incorporated into Ce0.8Sm0.2O2-δ lattice to tailor oxygen storage and catalytic properties of Ni-Ce0.8-xSm0.2ZrxO2-δ anode for improving electrochemical oxidizations of various fuel species. An inert thick YSZ microtubular substrate with radially well-aligned microchannels open at the inner surface is used to support multi thin functional layers of solid oxide cell, i.e., Ni current collector, Ni-Ce0.8-xSm0.2ZrxO2-δ anode, YSZ/SDC electrolyte, and LSCF cathode. The thick YSZ substrate is able to inhibit the ratio of fuel to product gases in the thin anode functional layer, which favors the prevention of carbon buildup in the thin anode layer when synergistically combined with Ni-Ce0.8-xSm0.2ZrxO2-δ anode material. The microchannels embedded in the YSZ substrate can also avoid too much dilutions of the fuel in the anode functional layer. The cell is fabricated and tested with both hydrogen and methane as the fuel. A short-term test is conducted with methane as fuel and good stability is obtained. The fundamental mechanisms for the prevention of carbon buildup in anode functional layer are also discussed.

Novel SOI LDMOS Without RESURF Effect by Flexible Substrate for Flexible Electronic Systems

In this article, laterally diffused MOS (LDMOS) combined with flexible substrate polydimethylsiloxane (PDMS) which can be used in flexible electronic system is described. The flexible substrate has insulation characteristics, which makes the original substrate float; thus, the substrate electrode and reduce surface electric field (RESURF) technology are missing. The simulation results show that the breakdown voltage (BV) of LDMOS combined with PDMS decreases by 23.3%. Considering that most flexible electronic systems require thin functional layers to achieve portability, the use of SOI LDMOS can achieve better performance on thinner substrates. Then, through simulation, the flexible substrate will reduce the BV of the SOI LDMOS by 17.4%, and combined with experiments and tests, it is verified that the flexible substrate will indeed reduce the BV of the SOI LDMOS by 15%, which is basically consistent with the simulation results. But there is no obvious effect on the specific ON-resistance ( R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> ON,sp</sub> ). For the phenomenon of substrate floating, a new structure named surface electrodes trench drift region SOI LDMOS (SETD SOI LDMOS) is proposed. After optimizing the simulation, compared with conventional SOI LDMOS, the SOI LDMOS combined with the flexible substrate can achieve a 57.54% increase in the BV while reducing R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> ON,sp</sub> by 11%.

Thin Functional Zeolite Layer Supported on Infrared Resonant Nano‐Antennas for the Detection of Benzene Traces

AbstractInfrared absorption spectroscopy is a powerful analytical tool that enables the identification of molecular species. The sensitivity of this technique, that is strongly limited by the small absorption cross‐section of molecular vibration, can be greatly improved by resonant interaction with nano‐antennas via the surface‐enhanced infrared absorption (SEIRA) mechanism. However, most of the examples of SEIRA concern solid‐state molecular layers adsorbed on the nano‐antennas, while the detection of gas traces still remains elusive due to the spatial extent of the near‐field that is used to amplify the molecular vibrations resonantly. Here, a hybrid system composed of a plasmonic nano‐antenna array coupled with nanosized zeolite coating for detection of volatile organic compounds in the near field of the resonators is demonstrated. The concerted action of the coating and the nano‐antennas enabled the authors to detect record traces of benzene (25 ppb) within 10 min. This approach may ultimately allow the fabrication of a compact system for rapid detection of pharmaceutical and biocompounds with high sensitivity and high selectivity.

The Effect of Thin Functional Electrode Layers on Characteristics of Intermediate Temperature Solid Oxide Fuel Cell

The thin-film multilayer structure of the membrane-electrode assembly in a solid oxide fuel cell which involves a NiO/ZrO2:Y2O3 anode functional layer and a La0.6Sr0.4CoO3 cathode functional layer and also a bilayer ZrO2:Y2O3/Ce0.9Gd0.1O1.95 electrolyte is formed by magnetron sputtering onto a supporting NiO/ZrO2:Y2O3 anode. The effect of the functional electrode layers involved in the structure of a solid oxide fuel cell on its efficiency is studied. The volt–ampere characteristics of multilayer fuel cells are studied in the temperature range of 800–600°C. It is shown that the inclusion of a thin (600 nm thick) cathode functional layer into the structure of the membrane–electrode assembly enhances the fuel cell efficiency by reducing the polarization losses on electrodes. The maximum power density of the fuel cell with the cathode functional layer is 2290 and 500 mW/cm2 at 800 and 600°С, respectively. The simultaneous presence of anode and cathode functional layers is found to be unwelcome because gives rise to diffusion limitations on the anode.

Intrinsic kinetics of interfacial polycondensation reactions– the reaction of mPDA with TMC

The performance of thin film composite membranes used in reverse osmosis is decided by the thickness and structure of the thin functional layer, which in turn depend on the kinetics of the interfacial polycondensation (IP) reaction which produces this layer. Quantitative determination of these kinetics has been a challenge. In the present study, we extend the method of pH-metry developed in our earlier work to the study of IP kinetics, in the presence of the side reaction of hydrolysis of the organic phase monomer. The method has been used to establish the kinetics of MPDA –TMC system in the presence and absence of a surfactant, Tween-85. The experimental method used eliminates all transport resistances, so that intrinsic kinetic control of the observed process is ensured. The hydrolysis reaction is studied separately by an adaptation of the same method, and those kinetics are systematically incorporated in the treatment of the data from the IP reaction. The observed kinetics have been fitted to a lumped kinetic form of the power law type, and show that the reaction is approximately first order in the acid chloride group concentration, and order 1.6 in the amine group concentration. The surfactant has been seen to influence the magnitude of the rate constant significantly. The reaction usually stops well short of 100% conversion of the stoichiometrically limiting monomer, because of the lowering of pH which restricts the availability of the aqueous phase monomer at the reaction locale.

Functional Plasma Polymerized Surfaces for Biosensing.

The capabilities of biosensors for fast, economic, and user-friendly analysis of complex samples has led to the exploitation of analytical devices for detection, quantification, and monitoring of specific chemical species for various applications. For a sufficiently high surface reactivity toward the adopted bioreceptors, a thin functional layer is required to enable coupling of the target biomolecules and to provide good stability in the presence of a sample matrix. In this work, the generation of water-stable oxygen-rich plasma polymerized (pp) films deposited by atmospheric-pressure jet plasma for reliable immobilization of biomolecules is presented. Three types of pp films were developed and characterized. All of the obtained pp films were successfully used as a matrix layer in the SPR immunosensors, which provided excellent level of sensitivity, stability, and regenerability. The achieved results show that atmospheric pressure plasma-induced polymerization is a powerful alternative method for the preparation of matrix layers for a wide range of applications in the biological field.

Calibration of systems for quantitative fluorescence analysis of thin layers.

Imaging fluorescence analysis is a powerful tool for the characterization of thin functional layers. Due to the development of new components such as cost-efficient and long life diode lasers and LEDs as well as sensitive cameras, the number of industrial in situ sensors based on fluorescence analysis technology increased rapidly in recent years. Of crucial importance for all these new sensors are efficient and robust methods for calibration. Although there are many examples for the calibration of laboratory setups for single specialized applications, there is no standardized method for the traceable device independent calibration of imaging fluorescence systems. This paper presents the evaluation of five different methods for the calibration of systems for quantitative fluorescence analysis. Each method is applied for the calibration of an imaging fluorescence laser scanner. In addition to characterizing the precision of the methods, the work analyzes the usability of the methods for different applications. The results show for the first time that a calibrated IR point sensor can be used for the auto calibration of high resolution imaging inline fluorescence sensors. In addition, we present a novel method for the transfer of calibration data between analysis systems with different optical setups by using a solid material fluorescence standard.

Tubular solid oxide fuel cells fabricated by a novel freeze casting method

AbstractFreeze casting is an established method for fabricating porous ceramic structures with controlled porosity and pore geometries. Herein, we developed a novel freeze casting and freeze drying process to fabricate tubular anode supports for solid oxide fuel cells (SOFCs). Freeze casting was performed by injecting aqueous anode slurry to a dual‐purpose freeze casting and freeze drying mold wrapped with peripheral coils for flowing a coolant. With the use of an ice barrier layer, proper control of the experimental setup, and adjustments in the drying temperature profile, complete drying of the individual anode tubes was achieved in 4 hours. The freeze‐cast anode tubes contained radially aligned columnar pore channels, thus significantly enhancing the gaseous diffusion. SOFC single cells with conventional Ni/yttria‐stabilized zirconia/strontium‐doped lanthanum manganite materials were prepared by dip coating the thin functional layers onto the anode support. Single cell tests showed that the concentration polarization was low owing to the highly porous anode support with directional pores. With H2/N2 (1:1) fuel, maximum power densities of 0.47, 0.36, and 0.27 W/cm2 were recorded at 800°C, 750°C, and 700°C, respectively. Our results demonstrate the feasibility of using freeze casting to obtain tubular SOFCs with desired microstructures and fast turn‐around times.

Stochastic Geometrical and Microstructural Modeling for Solid Oxide Cell Electrodes

As it plays a key role on the performances and durability of solid oxide cells, the electrode microstructure has to be finely characterized and modelled. In this frame, a plurigaussian random field model and an original sphere packing algorithm have been developed to simulate a large variety of electrode microstructures. The two stochastic geometrical models have been validated on various electrode reconstructions obtained by synchrotron X-ray holotomography including the microstructures of thin functional layers and a thick current collector. Afterwards, semi-analytical microstructural correlations have been proposed and validated on a large dataset of representative synthetic microstructures. These equations allow establishing the links between the microstructural properties controlling the performances (Triple Phase Boundary lengths density and specific surface areas) to the ‘basic’ geometric attributes of the electrode (composition, porosity and particle size distribution). These correlations have been used to model the loss of active TPBl due to the Ni agglomeration.

Deposition of thin δ-MnO2 functional layers on carbon foam/sulfur composites for synergistically inhibiting polysulfides shuttling and increasing sulfur utilization

Practical application of LiS battery is greatly impeded by the critical challenges of large volume expansion, intrinsic insulation problem of active materials, and serious polysulfides shuttling. Thus, it is still quite essential for us to search an efficient strategy to synergistically overcome these problems. Herein, we design and in-situ deposit a functional δ-MnO2 layer onto the outside surface of porous carbon foam/sulfur composites to synergetic inhibit the polysulfides shuttling and increase sulfur utilization, finally improve the electrochemical performance of LiS batteries. As verified by UV–vis and XPS results, the strong chemical interaction between the MnO2 layer and polysulfide intermediates is characterized to be an internal disproportionation reaction by transferring the absorbed long-chain polysulfides into insoluble polythionate complex. Also, the unique structure possesses high conductivity and good volume expansion tolerance, further guaranteeing the electrode a good cycling stability, rate performance and low self-discharge behavior. The MnO2 coated carbon foam/S electrode displays a remarkable capacity of 1547 mA g−1 at 0.1 C, and achieves a reversible capacity of 629 mA g−1 after 300 cycles at 1 C. Even with sulfur loading of 2.6 and 4.3 mg cm−2, the designed electrodes still deliver an initial discharge capacity of 1106 and 963 mA g−1 at 0.2 C.