Electrolyte Coatings Research Articles

Composite electrochemical coatings of Ni-CrB2 from sulfuric acid and sulfamate electrolytes: formation, structure and properties

Electrodeposited coatings are in demand in many industries: due to the high adhesive strength to the base metal, they can be applied to complex-shaped products, and the thickness of the deposited coating can be controlled. However, standard electrolytic coatings do not always meet the necessary operating requirements. In this case, the formation of composite electrolytic coatings, which consist in the modification of electrolytes by various dispersed particles, becomes an urgent task. These particles are introduced into the electrolyte and deposited together with the precipitate metals, which leads to changes in the coating properties. In this article, the structure, adhesive and corrosion properties of nickel-chromium diboride composite coatings obtained in the electrodeposition process are studied. Precipitation was carried out in sulfuric acid and sulfamate electrolytes with a concentration of dispersed chromium diboride particles of 10-40 g/l. The coatings consist of nickel and CrB2 phases. The adhesive strength of the coating with a steel base is satisfactory; chipping and peeling were not observed. The corrosion resistance of sulfamate electrolyte coatings is higher than that of the coatings obtained from sulfuric acid electrolyte due to the compactness of nickel precipitates. Chromium diboride in the coating provides 1.5-2 times greater corrosion resistance.

Effect of low concentration electrolytes on the formation and corrosion resistance of PEO coatings on AM50 magnesium alloy

In this paper, the formation process, morphology, and electrochemical performance of PEO coatings on AM50 magnesium alloy prepared in low concentration phosphate, aluminate, and phosphate-aluminate electrolytes were systematically studied. The results show that the coatings prepared from the phosphate electrolytes have a higher thickness and better corrosion resistance properties compared to the other electrolytes. The coatings prepared from low concentration phosphate-aluminate mixed electrolytes have slightly thinner thickness, a similar coating structure and an order of magnitude lower value of electrochemical impedance compared with phosphate electrolyte coatings. The Coatings prepared from low concentration aluminate electrolytes have the lowest thickness and the worst corrosion resistance properties which gets close to corrosion behavior of the bare AM50 under the same test conditions. Considering application, coatings prepared from single low concentration phosphate electrolytes and low concentration phosphate-aluminate electrolytes have greater potential than single low concentration aluminate coatings. However, reducing the electrolyte concentrations of coating forming ions too much has negative influence on the coating growth rate.

Submicron-thick single anion-conducting polymer electrolytes

Non-line-of-sight techniques are well suited for fabrication of thin and conformal solid-state electrolyte coatings, especially within three-dimensionally porous electrode architectures.

Fabrication of fuel electrode supported proton conducting SOFC via EPD of La2Ce2O7 electrolyte and its performance evaluation

The proton conducting La2Ce2O7 electrolyte has already been shown to be chemically more stable to H2O and CO2 than BaCeO3 based electrolyte materials. It has become widely popular as an alternative electrolyte for low to intermediate temperature operation in solid oxide fuel cells. Few initial studies have reported the fabrication of LCO-based fuel cells using the co-pressing process. Here, we present an alternative, simple, cost-effective and efficient method for the deposition of uniform and dense La2Ce2O7 electrolyte coatings, which is a key requirement for any fuel cell fabrication process. In this work, La2Ce2O7 is synthesized by a conventional solid state reaction route and we have established the process of fuel cell fabrication followed by its investigation for SOFC application as electrolyte material. Different alcohols (e.g. butanol, ethanol, acetone, acetyl acetone and isopropanol) are used as dispersion medium, the suspension chemistry and subsequent coating of LCO powders by electrophoretic deposition are investigated. A thin and good quality coating of about 11 μm thickness is obtained in an ethanol-based suspension under deposition conditions at 50 V for 2 min. Fuel electrode supported half cells with LCO electrolyte fabricated by electrophoretic deposition and performance test of fabricated cell is evaluated in moist H2 (∼3% H2O) as reducing medium and static air as oxidizing medium.

Electrolyte Coatings for High Adhesion Interfaces in Solid-State Batteries from First Principles.

We introduce an adhesion parameter that enables rapid screening for materials interfaces with high adhesion. This parameter is obtained by density functional theory calculations of individual single-material slabs rather than slabs consisting of combinations of two materials, eliminating the need to calculate all configurations of a prohibitively vast space of possible interface configurations. Cleavage energy calculations are used as an upper bound for electrolyte and coating energies and implemented in an adapted contact angle equation to derive the adhesion parameter. In addition to good adhesion, we impose further constraints in electrochemical stability window, abundance, bulk reactivity, and stability to screen for coating materials for next-generation solid-state batteries. Good adhesion is critical in combating delamination and resistance to lithium diffusivity in solid-state batteries. Here, we identify several promising coating candidates for the Li7La3Zr2O12 and sulfide electrolyte systems including the previously investigated electrode coating materials LiAlSiO4 and Li5AlO8, making them especially attractive for experimental optimization and commercialization.

Engineering Cathode-Electrolyte Interface of High-Voltage Spinel LiNi0.5Mn1.5O4 via Halide Solid-State Electrolyte Coating.

The high-voltage spinel LiNi0.5Mn1.5O4 (LNMO) cathode material with high energy density, low cost, and excellent rate capability has grabbed the attention of the field. However, a high-voltage platform at 4.7 V causes severe oxidative side reactions when in contact with the organic electrolyte, leading to poor electrochemical performance. Furthermore, the contact between the liquid electrolyte and LNMO leads to Mn dissolution during cycles. In this work, we applied the sol-gel method to prepare Li3InCl6-coated LNMO (LIC@LNMO) to address the mentioned problems of LNMO. By introducing a protective layer of halide-type solid-state electrolyte on LNMO, we can prevent direct contact between LNMO and electrolyte while maintaining good ionic conductivity. Thus, we could demonstrate that 5 wt % LIC@LNMO exhibited a good cycle performance with a Coulombic efficiency of 99% and a capacity retention of 80% after the 230th cycle at the 230th cycle at 1C at room temperature.

Utilizing torch-substrate relative velocity to reduce segmentation crack density in plasma sprayed zirconia for solid oxide cell applications

Torch-substrate relative velocity is a plasma spray coating control parameter that affects lamellar thickness, heat transfer from the torch to the substrate, splat dispersion, and segmentation crack density. Within the thermal barrier coating and solid oxide fuel cell/solid oxide electrolysis literature, plasma sprayed coatings are rarely fabricated with velocities that exceed ∼2 m s−1. Here, we explore the effect of torch-substrate relative velocities in the range of 4–20 m s−1 on crack density in thin (10–15 μm) solid oxide cell electrolyte coatings. Crack densities were observed to drop from ∼2.4 to ∼0.04 mm−1 by increasing the torch-substrate relative velocity from 4 to 16 m s−1. In agreement with previous studies performed at lower velocities, crack densities correlate well with plasma torch heat impulse. Full cells were fabricated using torch-substrate relative velocities of 12–20 m s−1.

Direct Electrophoretic Deposition and Characterization of Thin-Film Membranes Based on Doped BaCeO3 and CeO2 for Anode-Supported Solid Oxide Fuel Cells.

In this work, a technology was developed for the formation of BaCe0.8Sm0.2O3+1 wt% CuO (BCS-CuO)/Ce0.8Sm0.2O1.9 (SDC) thin-film electrolyte membranes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) on porous NiO-BCS-CuO anode substrates using direct electrophoretic deposition (EPD). The effect of increasing the zeta potential when modifying the base suspension of a micro-sized SDC-gn powder (glycine–nitrate method) with the addition of a SDC-lec nanopowder (laser evaporation–condensation) was investigated. Dependences of the current strength on the deposition time and the deposited weight on the EPD voltage were obtained, and evolution of the morphology of the coatings during the modification of the SDC-gn suspension and a suspension of BCS-CuO powder was studied. The compatibility of the shrinkage kinetics of the SDC, the BCS-CuO electrolyte coatings and the NiO-BCS-CuO anode substrate was studied during the high-temperature sintering. Dense BCS-CuO/SDC films of different thicknesses were obtained for the first time on porous NiO-BCS-CuO anode substrates and comprehensive microstructural and electrochemical studies were carried out. The developed technology can be applied to the formation of anode-supported SOFCs with thin-film electrolyte membranes.

Li2s-P2S5 Solutions for Forming Solid Electrolyte Coating Layers on Electrode Materials for All-Solid-State Batteries

Sulfide-based solid electrolytes are promising for all-solid-state batteries because they exhibit high ionic conductivity over 10−4 S cm−1 and have good ductility. They are often prepared by mechanical milling or high-temperature synthesis. As an alternative to these methods, the preparation of sulfide solid electrolytes by a liquid-phase process, using organic solvents to promote the reactions, has been proposed during the last few years. The liquid-phase synthesis is a more facile process for industrial scaling-up. It also offers the possibility to produce solid electrolyte coating layers on electrode materials by their direct precipitation, achieving intimate contacts, which is crucial for good electrochemical performance in all-solid-state batteries.Although great attention has been given to the liquid-phase synthesis of sulfide solid electrolytes during the last years, the reaction mechanisms and the role of solvents in the reactions is not yet well understood. In this work, we elucidated the reaction between Li2S and P2S5, mediated by acetonitrile that leads to the formation of the PxSy z- thiophosphate anions.Li2S and P2S5 in a 1:1 molar ratio were found to quickly react to form a LiPS3 solution. The 31P NMR spectrum of the LiPS3 solution (Figure 1) showed that the P atom was located in different chemical environments, indicating the formation of polymer-like [PS3 −]n chain units. The [PS3 −]n chains react upon heat treatment at temperatures above 180 °C to form P2S6 2− units, as it was confirmed by Raman and 31P MAS NMR spectroscopy. However, an increase in the sulfur content by adding Li2S to the LiPS3 solution was found to break the P-S-P bonds in the [PS3 −]n chains, resulting in the formation of PS4 3− units. If sulfur provided by Li2S is not enough to break all P−S−P bridges, the PS4 3− units and the remaining [PS3 −]n chains react upon heat treatment (>180 °C), resulting in the formation of P2S7 4− units [2]. These findings give a deeper insight into the reaction mechanisms governing the liquid-phase synthesis of sulfide solid electrolytes. Moreover, the characterization of the LiPS3 solution indicates it as a promising material for the formation of solid electrolyte coating layers on electrode materials.

Microscale Thermal Modelling of Multifunctional Composite Materials Made from Polymer Electrolyte Coated Carbon Fibres Including Homogenization and Model Reduction Strategies

Polymer electrolyte coated carbon fibres embedded in polymeric matrix materials represent a multifunctional material with several application scenarios. Structural batteries, thermal management materials as well as stiffness adaptive composites, made from this material, are exposed to significant joule heat, when electrical energy is transferred via the carbon fibres. This leads to a temperature increase of up to 100 K. The thermal behaviour of this composite material is characterized in this numerical study based on a RVE representation for the first time. Compared to classical fibre reinforced plastics, this material comprises a third material phase, the polymer electrolyte coating, covering each individual fibre. This material has not been evaluated for effective thermal conductivity, specific heat and thermal behaviour on the microscale before. Therefore, boundary conditions, motivated from applications, are applied and joule heating by the carbon fibres is included as heat source by an electro-thermal coupling. The resulting temperature field is discussed towards its effect on the mechanical behaviour of the material. Especially the temperature gradient is pronounced in thickness direction, leading to a temperature drop of 1 °Cmm, which needs to be included in thermal stress analysis in future thermo-mechanically coupled models. Another important emphasis is the identification of suitable homogenization and model reduction strategies in order to reduce the numerical effort spent on the thermal problem. Therefore, traditional analytical homogenization methods as well as a newly proposed “Two-Level Lewis-Nielsen” approach are discussed in comparison to virtually measured effective quantities. This extensive comparison of analytical and numerical methods is original compared to earlier works dealing with PeCCF composites. In addition, the accuracy of the new Two-Level Lewis-Nielsen method is found to fit best compared to classical methods. Finally, a first efficient and accurate 2D representation of the thermal behaviour of the PeCCF composite is shown, which reduces computational cost by up to 97%. This benefit comes with a different Temperature drop prediction in thickness direction of 1.5 °Cmm. In the context of future modelling of multifunctional PeCCF composite materials with multiphysical couplings, this deviation is acceptable with respect to the huge benefit for computational cost.

An Effective Strategy for Interface Modification and Polysulfide Confinement by Gel Polymer Electrolyte Coating on the Sulfur Cathode

A novel poly(acrylamide-co-acrylic acid) (P(AM-co-AA)) coating layer is facilely introduced on the top of sulfur composite cathode. The polymer membrane owns abundant and well-distributed microporous framework, favoring large electrolyte uptake and high ionic conductivity. Upon activation with the liquid electrolyte, the porous matrix immediately swells, forming a gel polymer electrolyte coating (GPEC) cathode. Not only does the unique coating design greatly restrain the out-diffusion of polysulfides from the cathode, but also improves ion transport at the cathode/electrolyte interface and provides flexible surface protection for the electrode structure. The GPEC cathode exhibits relatively low polarization, high sulfur utilization and superior cycle stability, as compared to the conventional sulfur cathode.

Protection of fuel filter with alkaline and acid zinc coatings

Galvanic coatings are applied so that the surface of the base material obtains appropriate properties, corrosion resistance, durability, aesthetic appearance, and long-term application in the appropriate industry. In this paper, the aim was to protect steel fuel filters with alkaline and acid zinc coatings of different thicknesses. The coating of zinc, which is applied from the alkaline electrolyte, provides good corrosion protection with excellent coating flexibility. The thickness of the coating by the X-ray fluorescence method was tested, followed by coating tests, corrosion resistance, and electrochemical tests. The results of adhesion showed a high quality coating, as no corrosion occurred during the test. The corrosion resistance tested by the salt chamber method speaks of the appearance of white and red corrosion. On alkaline electrolyte coatings, white corrosion occurred after 168 hours of exposure to the salt test, while on white zinc samples there was a white corrosion after 240 hours of exposure. Tafel polarization diagrams have been determined: corrosion potentials, current intensities, anode and cathode Tafel coefficients and calculated corrosion rates. The active and passive corrosion zone is determined by the cyclic voltammetry.

Aerosol Deposition as a Promising Technique to Fabricating a Thin-Film Solid Electrolyte of Solid Oxide Fuel Cells

In present work we developed and tested model anode-supported planar solid oxide fuel cells. We used commercially available 2-layered (current-collector and functional) anode supports. Thin-film electrolyte layer based on 8 mol.% yttria-stabilized zirconia (YSZ) was produced by aerosol deposition method using converging-diverging (de Laval) type nozzle. To provide the fabrication of pinhole-free gas-tight thin-film electrolyte coatings, the pre-treatment procedure of initial powders was developed. The optimal operating parameters of the deposition modes of the YSZ solid electrolyte of different thicknesses are determined. Morphology analysis of the obtained thin-film coatings showed that the application of these modes provides the fabrication of thin-film YSZ layer with thickness of a few microns possessed good adhesion to the anode support, gas tightness and uniformity thickness.

Dendrite-free sandwiched ultrathin lithium metal anode with even lithium plating and stripping behavior

Thin artificial solid electrolyte coatings are effective to enhance the electrochemical performances and safety issues of lithium (Li) metal anode. However, massive and efficient fabrication of artificial protection layers on Li metal anode surface remains challenging. Herein, we describe a sandwiched Li metal anode fabricated through a continuous roll to roll calendering method to implant a thin and large-area carbon layer on Li metal anode surface at room temperature. Specifically, a carbon layer (~ 3 μm in thickness) can be entirely grafted from Cu substrate to 50 μm Li belt surface due to the stickiness of metallic Li. The carbon layer not only plays a critical role in providing rich nucleation sites for Li plating, but more importantly diminishes the metallurgical nonuniformity effects (slip lines) on stripping. Therefore, even Li plating/stripping morphologies are achieved and the as-obtained sandwiched Li/C composite anodes exhibit improved cycling stability both in Li | LiFePO4 and Li | S coin cells and pouch cells. This continuous roll to roll calendering strategy opens a new avenue for grafting various thin artificial protection layers on Li metal surface for safe rechargeable batteries.

Pulsed constant voltage electrophoretic deposition of YSZ electrolyte coating on conducting porous Ni–YSZ cermet for SOFCs applications

In the present investigation, solid oxide fuel cells (SOFCs) electrolyte coatings of 8 mol% Y2O3 stabilized ZrO2 (YSZ) are applied on Ni-YSZ cermet fuel cell anode in ethanol by pulsed constant voltage-electrophoretic deposition (EPD). Press pressure and sintering temperature as two of the most effective parameters for NiO-YSZ composite fabrication are investigated. In order to create electrically conductive anodes, NiO-YSZ composite is reduced in H2 atmosphere while its crystallinity being studied by X-ray diffraction (XRD). Pulsed constant voltage EPD process parameters such as pulse width, applied voltage and total deposition time are examined. The YSZ electrolyte film is sintered for 4 h at two different temperatures of 1300 and 1350 C°. Optical microscope (OM) is used to study the surface quality of coating. Substrate morphology and the quality of YSZ electrolyte film are investigated by scanning electron microscope (SEM). Atomic force microscopy (AFM) is used to probe the surface roughness and the morphology of green and sintered coatings. Results show improved deposition yield by increasing applied voltage and total deposition time. Uniform and dense coating was deposited at voltage of 35 V, pulse width of 1 ms, 50% duty cycle and total deposition time of 6 min having the thickness and roughness of about 17 ± 1 μm and 166 ± 5 nm, respectively.

Enable High Initial Coulombic Efficiency for Lithium Battery Anode By Ultrathin Polymer Electrolyte Coating

The current lithium battery anodes (graphite and graphite-silicon composite) suffer from low initial coulombic efficiency and low charging rate at low temperature. To address these issues, uniform stable solid electrolyte interphase (SEI) and higher ionic transference number are of primary importance. Recent advancements of nanoscale polymer coating open a new way in surface optimization for better performance. Initiated chemical vapor deposition ((iCVD) could achieve uniform nanoscale polymer coating on the porous substrate, which can enable the large-scale coating on battery electrode sheet. Here, ultrathin conformal coating of the Poly(methacrylic acid) (PMAA) polymer is achieved on graphite electrode by iCVD. Then, Ion-exchange is conducted to form the lithium polymer electrolyte. The high ionic transference number of the polymer electrolyte would significantly reduce the ionic polarization at the electrochemical interface, enabling the higher initial coulombic efficiency and power performance at low temperature. The cycling performance was also significantly improved due to the uniform nanoscaled polymer coating.

Optimization of MRR and Electrolyte Coating Thickness of ECM Parameters using PCA based GRA

Now a days, Electro chemical machining (ECM) is used under non-traditional machining process for machining of complicated shape. The aim of this paper is to recognize the performance of MRR and Electrolyte Coating Thickness parameters on the AA 6082 and AA 6082 MMC. Experiment is conducted on the basis of four machining parameters i.e. voltage, feed rate, electrolyte concentration and electrode. PCA coupled Grey relational analysis methodology is used in present work. Design-Expert 6.0.8. has been used to perform the experimental runs. The optimum combination of process parameters are obtained from the analysis and the corresponding value of MRR and Electrolyte Coating Thickness are also obtained separately. ANOVA is performed to get contribution of each parameter on the performance characteristics. Confirmation tests are carried out to check the validity of the study.

Elastic and Stretchable Gel Polymer Electrolyte Coating to Improve Long-Term Cycling Stability of High-Areal-Capacity Sio Electrode for Lithium-Ion Battery

Si-based anode is an advanced anode material to improve the energy density of Li-ion battery. In order to pair with commercial cathode, the areal capacity of Si-based anode should be increased to 3-4 mAh/cm2. However, high-areal-capacity Si-based anode still encounters fast capacity fading and poor cycling stability, because large volume change upon cycling will damage electrode structure integrity and arise accumulated growth of SEI (solid electrolyte interface) layer. Here we develop an elastic and stretchable polyurethane-urea (PUU) gel polymer electrolyte (GPE) coating strategy to improve the long-term cycling stability of high-areal-capacity SiO anode. The PUU polymer coating can swell and uptake 48 w% carbonate electrolyte, providing a moderate ionic conductivity of 2.4*10-4 S/cm at room temperature. The GPE shows good chemical and electrochemical stability with lithium metal. At the electrode level, the GPE coating can improve electrode adhesion strength and alleviate electrode thickness change during charge/discharge process. For long-term cycling, the GPE coating can restrict the pulverized particles in a localized space to prevent loss of conductive network and maintain the electrode structure integrity. In the half-cell test, the SiO electrode with GPE coating shows a reversible capacity of 3.0 mAh/cm2 (or specific capacity of 1200 mAh/g) for 280 cycles. In the full-cell test, the cell of pre-cycled NCM/pre-cycled SiO electrode with GPE coating has a reversible capacity of 2.1 mAh/cm2 (or specific capacity of 150 mAh/g) for 200 cycles, with an improved Coulombic efficiency of 99.9%.

Electrochemical and structural evaluation for bulk-type all-solid-state batteries using Li4GeS4-Li3PS4 electrolyte coating on LiCoO2 particles

Bulk-type all-solid-state batteries, which use composite electrodes with a powder mixture of active materials and solid electrolytes, are anticipated for large-scale power sources. However, conventional powder mixing protocols are insufficient to maintain ion-conductive pathways within composite electrodes. Herein, sulfide electrolyte coatings have attracted attention as a promising means to overcome this difficulty. We assessed the effects of sulfide electrolyte coatings for active materials on the electrochemical properties and structural changes in all-solid-state cells. A favorable electrode-electrolyte interface was formed by coating significantly small amounts (ca. 3 wt%) of Li4GeS4-Li3PS4 solid electrolyte (SE) onto LiCoO2 particles via vapor phase process. The all-solid-state cell (In/Li2S-P2S5/SE-coated LiCoO2) was charged and discharged with a larger capacity than that using non-SE-coated LiCoO2 particles, indicating that the SE-coating is effective in forming a favorable ion-conductive pathway to LiCoO2 particles. Improvement of the cell performance after heat treatment was considered to derive not only from the enhancement of ionic conductivity in the SE-coating layer, but also from the reduction of voids in the composite electrode. Less ionic resistance and denser environment are beneficial for the Li-ion supply to the deepest part in the composite electrode, which results in more homogeneous electrochemical reaction in all-solid-state cells.

(Invited) Atomic Layer Deposition: Eye on the Future of Batteries

Over the past few years, as atomic layer deposition (ALD) has emerged as a promising technique to improve the performance of electrochemical energy storage devices. In conventional battery architectures and chemistries, ALD layers have been used to protect the surface of anodes1 and cathodes,2 resulting in improved electrode stability and enhanced cycling performance. Beyond conventional Li-ion batteries, ALD has allowed fabrication of ultra-high performance 3D nanoheterostructures that combine intimate contact between high electrical conductivity current collectors and thin layers of active material for incredible charge/discharge rate capabilities proportional to the active material surface area. Both anode3 and cathode4 nanoheterostructures exhibit significantly higher charge/discharge rate capabilities over their bulk electrode counterparts in ½ cell geometries. The culmination of this architecture uses the high degree of control inherent in the ALD process to fabricate arrays of opposing cylindrical heterostructures inside a nanoporous template, and can achieve nearly 50% theoretical capacity while charging/discharging at a rate of 150 C.5 However, use of liquid electrolytes present a number of challenges with high power electrodes. High charge/discharge rates, desirable for fast charging of plug-in hybrid vehicles and personal electronic devices exacerbate already present safety issues, particularly that of Li dendrite formation and subsequent cell failure. Increased electrode surface area may mitigate dendrite formation by lowering the local current density, but deleterious electrolyte degradation reactions can consume electrolyte and result in eventual cell failure. Use of solid state electrolytes, previously only suitable for niche applications due to their low inherent ionic conductivity and limitations in fabrication process, can now be expanded to new applications such as the previously described 3D batteries by utilizing ALD processes. A number of suitable ALD process for well-known solid electrolytes have been developed,6,7 allowing deposition of thin, conformal solid electrolyte layers at temperatures as low as 150˚C. The current status of 3D solid state batteries will be discussed, as will remaining challenges. ALD’s capability for very thin solid electrolyte layers opens the door to advanced electrode protection, and and recent results showcasing the utility of ALD solid electrolyte coatings for protection layers on 3D nanoheterostructured electrodes and next-generation Li metal anodes will be discussed. In the case of conversion electrode materials, ALD coatings can prevent electrolyte decomposition and solid electrolyte interphase formation, lowering overpotential required for charge and discharge. Additionally, ALD coatings mechanically constrain conversion electrode particles, preventing volume expansion and fracturing of the coatings upon cycling.8 ALD layers applied to Li metal anodes can prevent electrolyte decomposition and Li dendrite formation by chemical stabilization of the electrode surface, resulting in both higher capacities and longer cycling lifetimes in the case of the Li-S and Li-Air systems.9,10