Anodic Layer Research Articles

Improvement of corrosion resistance and adhesion of hydroxyapatite coating on AZ31 alloy by an anodizing intermediate layer.

The primary objective of this study is using an anodizing intermediate layer to improve corrosion resistance and adhesion of hydroxyapatite coated AZ31 alloy for applications in biodegradable implants. An anodizing intermediate layer was formed on the surface of AZ31 substrate at various anodizing voltage of 10, 20, 30, and 40 V respectively by anodizing process. HAp was grow on the surface of AZ31 substrate at 90°C and pH solution of 7.5 by chemical solution treatment method for 2 h. The coated samples were evaluated their corrosion behavior by Electrochemical measurements and biodegradation behavior by immersion test in Hank's balanced salts solution (HBSS) for 28 days via amount of Mg2+ ion released. While, their adhesion strength were evaluated by pull-off method. The amount of Mg2+ ions released of the samples was quantified by the Inductively coupled plasma mass spectrometry. An anodizing intermediate layer was successfully synthesized at various voltages by anodizing process and HAp coatings were prepared by chemical solution treatment method. The corrosion rate of hydroxyapatite coated AZ31 alloy with an anodizing intermediate layer decreased 4.4 times, while adhesion strength increased about two times compared to the HAp coated AZ31 specimen without an anodizing layer and achieved ~14.70, ~6.92 MPa, respectively. After immersion test in HBSS, the adhesion strength of HAp/AZ31-HBSS-specimen decrease to 45% because of large corroded areas with depth holes of hundreds of micrometers. The slighter decrease in adhesion strength of HAp/30V/AZ31-HBSS-specimen to 22% is due to the contribution of the anodizing intermediate layer. HAp coated AZ31 alloy specimen with the existence of a porous structure with an elliptical shape, uniform and high density of MgO on the surface at anodizing voltage of 30 V resulted in a significant increase in corrosion resistance and the adhesion strength of HAp coatings.

Protective layer for stable lithium-metal anodes at 60 mA·h/cm2 and 60 mA/cm2 with ion channel and inductive effect

Contradiction between ultrafast nucleation and deposition rates of lithium (Li) crystals at high rate and heterogeneity of Li+ flux resulting from concentration polarization has compromised the performance of Li metal anodes especially at high areal capacity and current density. Here, multifunctional protective layer consisting of MoO3 nanobelt films (MoO3-NF) is introduced on the surface of Li by a simple rolling method. The strong binding energy between Li and MoO3 guides the homogeneous nucleation and deposition of Li, while the nanobelt networks provide effective ion channels for uniform distribution of the Li+ flux. Because of the novel multifunctional protective layer, the MoO3-NF@Li anodes demonstrate a remarkable stability for 800 h with ultralow overpotential of 159 mV at extreme harsh conditions of 60 mA·h/cm2 and 60 mA/cm2. MoO3-NF@Li||LiNi0.6Co0.2Mn0.2O2 full-cells can run 100 cycles with a superior capacity retention of 84.2% under practical test conditions, demonstrating great potential for high output and energy-density metal batteries.

Development of nanostructured Ge/C anodes with a multistacking layer fabricated via Ar high-pressure sputtering for high-capacity Li+-ion batteries

To realize high-capacity Ge anodes for next-generation Li+-ion batteries, a multilayer anode with a C(top)/Ge(middle)/C(bottom) structure was developed, where nanostructured amorphous Ge (a-Ge) and amorphous-like carbon films with a grain size of 10–20 nm were deposited sequentially by high-pressure Ar sputtering at 500 mTorr. Compared with the a-Ge anode, the C(top)/a-Ge(middle)/C(bottom) multistacking layer anode showed improved capacity degradation for repeated lithiation/delithiation reactions and achieved a high capacity of 910 mAh g−1 with no capacity fading after 90 cycles at a C-rate of 0.1.

The role of peening processes as a pre‐treatment to anodizing on fatigue behavior of aircraft aluminum alloy

AbstractIn this work, the possibility of employing shot peening and laser peening as pre‐treatments to a tartaric–sulfuric anodizing process on the fatigue behavior of 7050‐T7451 aluminum alloy components was investigated. The surface modifications and stress fields induced by the combination of the peening and anodizing processes were evaluated by scanning electron microscopy and residual stress assessment methodologies based on diffraction techniques, respectively. It was found that the anodizing process alone results in a significant reduction in fatigue life compared to the as‐machined condition especially in the high‐cycle fatigue (HCF) region of the S–N diagrams due to the presence of defects within the anodic layer that act as stress concentrators facilitating the initiation of fatigue cracks. The application of both shot and laser peening treatments is demonstrated to offset the negative effects induced by anodizing, offering greater safety margins useful for the design of critical aeronautical structures.

Spherical Graphite Anodes: Influence of Particle Size Distribution and Multilayer Structuring in Lithium-Ion Battery Cells

Current research focuses on lithium-ion battery cells with a high energy density and efficient fast-charging capabilities. However, transport limitations, and, therefore, the uniform diffusion of lithium-ions across the electrode layers, remain a challenge and could lead to reduced cell performance. One approach to overcome these transport challenges is the use of subsequently produced two-layer anodes with the particle size variation of spherical graphite (x50 = 18 µm; x50 = 11 µm). Thereby, a defined pore network is created, which reduces the ionic resistance and ensuring improved fast charging capabilities. The analysis focuses on the evaluation of electrode properties and the electrochemical performance. By examining the pore size distribution of the anodes, it has been found that during the manufacturing of the two-layer anodes, carbon black and binder particles are transported into the existing microstructure of the lower layer, resulting in localized densification between the anode layers. This could also be supported by color measurements. This effect also extends to electrochemical investigations, with electrochemical impedance spectroscopy showing significantly lower ionic resistances in all two-layer anodes. Reduced ionic resistance and tortuosity near the separator due to absorption effects enhance the ion diffusion and have a direct impact on anode performance. Cell ageing analysis showed a significant capacity decrease of almost 15 mAh g −1 in the single-layer references only, in contrast to the stability of the two-layer anodes. This could also be attributed to the reduced ionic resistance and active counteraction of binder migration. In conclusion, this study highlights how subsequently produced two-layer anodes significantly shape the electrode properties and cell performance of lithium-ion batteries.

Interface engineering driven molybdenum disulfide coupled polyaniline functionalized carbon fabric with high mass loading anode for fiber lithium-ion batteries

Carbon fiber (CF) cloth presents a preeminent substrate for growing numerous active materials, emerging as a promising electrode design in fiber lithium-ion batteries (F-LiBs) for powering future wearable electronics. Nevertheless, the hydrophobic nature of CF affects the interaction between the active materials and CF, leading to inferior battery performance. Herein, we report a polyaniline (PANi) driven interface-engineering approach to address the recurring issue associated with CF. To demonstrate the concept, molybdenum disulfide (MoS2), a two-dimensional layered anode was grown on PANi-functionalized CF (MoS2/PANi/CF). The nitrogen functionalities of the PANi backbone enriched the surface functionality and facilitated the coupling adhesion between MoS2 and CF. This key feature influenced the charge transport kinetics across the MoS2/CF interface and preserved the structural integrity. More importantly, the strong coordination interaction between MoS2 and PANi improved the growth density of MoS2, resulting in high mass loading. Given these merits, the interfacially coupled MoS2/PANi/CF anode delivered a high specific capacity and enhanced rate and cycling performances. This study verifies the significance of the interface engineering approach, which can be extended to developing wide arrays of flexible electrodes for other wearable battery chemistries.

Numerical investigation of the effect of functional layer thickness on solid oxide fuel cell performance

ABSTRACT In this 3D numerical study, the effects of cathode and anode functional layer thicknesses on the performance of solid oxide fuel cells under different operating parameters are analysed and elucidated. The performance of the model is evaluated using direct ammonia and an equivalent amount of hydrogen fuel with functional layers ranging from 0 to 50 μm. The findings unveiled that the cathode functional layer has a stronger influence on cell performance than the anode functional layer. The parametric analysis also showed that the effect of temperature gradually weakened with the increase of the cathode functional layer which is the exact opposite of what anode functional layers do. This gives more promising result for the cathode functional layer than the anode functional layer, especially for hydrogen-powered cells. However, the anode functional layer works best when green ammonia is supplied directly to the solid oxide fuel cell. In this regard, the 10 μm functional layers of the anode and cathode layers achieved the highest possible power density using ammonia and hydrogen fuels under similar operating conditions. This suggests that the anode layer has outstanding performance than the cathode counterparts for ammonia-fuelled cells and the layers of the cathode have better performance for hydrogen-fuelled cells. It is also observed that the performance of the cell is decreasing while the thickness of the functional layer is increasing particularly after 10 μm. The study also confirmed that solid oxide fuel cells with functional layers have outstanding performance over corresponding cells without functional layers. Thus, the finding of this study concluded that the functional layer thickness is strongly dependent on the types of fuel and electrodes used in the cells.

Enhancing the performance of metallic lithium anode in batteries through water-resistant and air-stable coating

The limited reversibility and high reactivity of lithium metal with the liquid electrolyte in lithium batteries hinder its widespread adoption. The formation of an unstable solid electrolyte interphase layer and the sensitivity of lithium metal to moisture and air are major issues that need to be addressed. To overcome the practical challenges associated with the application of lithium anodes in lithium metal batteries, a well-thought-out design of a protective layer is proposed. Here, we have developed a composite coating comprising polyvinylidene fluoride, fumed colloidal silica, and paraffin wax as a protective layer for lithium metal anodes. The coating exhibits excellent electrochemical stability, high ionic conductivity, and mechanical stability, effectively suppressing dendrite growth and accommodating lithium volume changes during cycling. Moreover, the hydrophobic wax component can mitigate the atmospheric sensitivity of metallic lithium anodes. The coating process employed is facile and economically viable, significantly enhancing the scalability of lithium metal batteries. Experimental characterizations confirm the structure and composition of the coating, and electrochemical measurements demonstrate the improved electrochemical performance and cyclability of the coated lithium metal anodes. The results indicate that the developed composite coating has great potential for enhancing the electrochemical and processing stability of metallic lithium anodes for lithium metal batteries.

Construction of Robust Organic–Inorganic Interface Layer for Dendrite‐Free and Durable Zinc Metal Anode

AbstractConstructing artificial interface layer is an effective approach to facilitate the utilization rate of zinc metal, but the practical application is still hindered by the inferior mechanical strength, low ionic conductivity, and poor stability. Herein, robust organic–inorganic layer (Nafion/BM@Zn) is coated on zinc metal through ultrasonic spraying method with boehmite and Nafion as the composite precursor. As demonstrated, the high cation selectivity and high hydrophilicity of Nafion, as well as the zincophilic property and layered structure of boehmite, synergistically contribute to the low nucleation barrier, uniform deposition, and fast transport kinetics of Zn2+ ions. As a result, the Nafion/BM@Zn anode exhibits superior reversibility with a high Coulombic efficiency of 99.9% for 9000 cycles in asymmetrical cells and durable cycling stability for 4200 h in symmetrical cells at 5 mA cm−2−1 mAh cm−2. Even in the seawater‐based electrolyte, the Nafion/BM@Zn anode still displays reversible deposition behavior for 820 h and high Coulombic efficiency of 99.91% for 2800 cycles at 5 mA cm−2−1 mAh cm−2. Furthermore, the corresponding Nafion/BM@Zn//NH4V4O10 cell presents high capacity of 258.4 mAh g−1 after 1500 cycles at 5 A g−1. This work provides a new design strategy for high‐efficiency interfacial layer of zinc metal anode.

Membrane electrode assembly simulation of anion exchange membrane water electrolysis

Anion exchange membrane water electrolysis (AEMWE) offers a green hydrogen production method that eliminates the need for platinum group metals (PGM) as electrocatalysts. This study employs a COMSOL® 6.0 model to simulate a 1x1 cm2 Ni fibre − Raney® Ni || X37-50RT || NiFe2O4− SS316L fibre AEMWE membrane electrode assembly (MEA). The membrane is set at a thickness of 60μm, while the anodic and cathodic porous transport layers (PTL) are modelled with a thickness of 370μm, each having an average porosity of 0.70. The half−cell overpotentials are experimentally measured to validate the half−cell model in a three−electrode setup consisting of (working electrode) || AGAR-Ag/AgCl || Pt−wire (counter electrode). Two freshly prepared MEAs validated the (i) base case and (ii) sensitivity analysis models. The base case model validated the MEA results at 20 °C and 1 atm in 1M KOH electrolyte feed at 1.56 ml min−1 cm−2. The five parameters studied with the sensitivity analysis revealed the most influential parameters based on area-specific resistance (ASR) change in the following order (＋ and − indicate increase and decrease in ASR, respectively): KOH concentration (−97%), membrane thickness (＋ 9%), temperature (−4%), cathode feed type (<+0.5%), and KOH flow rate (>−0.5%).

Multilayered inverted polymer-based light emitting diodes fabricated by meniscus coating and transfer-printing technique

We have developed polymer-based inverted organic LEDs (iOLED) with a multilayered structure using orthogonal solvent, transfer-printing, improved meniscus-coating method that moves back and forth. Reciprocating the glass rod back and forth repeatedly, the material usage of electron-injection layers, polymeric light-emitting layer and polymeric hole-transporting layers were decreased to 1/10 for the film deposited onto the glass slide and to ca. 1/20 for the film deposited onto the elastomer stamp compared with the conventional spin-coating. We obtained higher external quantum efficiency (EQE) and lower operation voltage with solution processable metal oxide hole-injection layer and silver anode. The improvements in the threshold voltage and the maximum EQE were observed for the device with electron-transporting EIL, such as alcohol soluble phenanthroline derivative, which is an effective way to reduce the number of multilayers and the tact time for fabricating iOLEDs.

Atomic Sn sites on nitrogen-doped carbon as a zincophilic and hydrophobic protection layer for stable Zn anodes

A 3D coating of atomic zincophilic Sn sites anchored on NC supports on Zn anodes are designed to simultaneously guide Zn nucleation, boost Zn2+ diffusion, regulate electric field distribution, inhibit dendrite growth, and prevent side reactions.

Dual role of hBN as an artificial solid–electrolyte interface layer for safe zinc metal anodes

Monolayer and large area hBN as an artificial SEI layer shows dual role in preventing the undesired side reaction of HER and inducing the heteroepitaxial grown of Zn, successfully resolving the dendrite issue for safe Zn metal anode.

Achieving stable lithium metal anodes via the synergy of electrostatic shielding and the high Li+ flux inorganic interphase

A cationic polymer was developed as protective layer for Li anodes. The multiple cationic sites in molecule provided enhanced electrostatic shielding, whereas NO3− anions generated robust and high Li+ flux inorganic SEI.

Dual-anion chemistry synchronously regulating the solvation structure and electric double layer for durable Zn metal anodes

Dual-anion chemistry is engineered by adding strong polarity Ac− into Zn(OTf)2 electrolyte, which enables synchronous regulation of solvation structure and electric double layer, thereby countering rapid Zn2+ consumption and prompting favorable interphase formation for durable Zn metal anodes.

Microporous transport layers facilitating low iridium loadings in polymer electrolyte water electrolysis

The 3D structure of the anodic catalyst layer in polymer electrolyte water electrolysis is characterized and its shown that Pt-coated microporous transport layers help to reduce iridium loadings by maximizing catalyst utilization.

Ion Beam Etching of Anodic Aluminium Oxide Barrier Layer for Au Nanorod-Based Hyperbolic Metamaterials

Porous anodic aluminium oxide (AAO) is widely used as a template for the electrodeposition of ordered arrays of one-dimensional nanostructures. Prior to template filling, the barrier layer, which blocks the...

Can electrodeposited Ti replace rolled Ti as substrate for the growth of anodic TiO2 nanotube layers?

This study conducted a deep investigation of TiO2 nanotube (TNT) layers of two different thicknesses anodically grown on electrodeposited Ti films. The Ti films were grown from molten salts on Ni foils. The structure of the starting metals was compared by XRD (X-Ray Diffraction) and EBSD (Electron Backscatter Diffraction analyses), which showed a strong orientation towards the titanium (101) for the electrodeposited substrate, compared to the rather polycrystalline structure of the rolled Ti. The photoelectrochemical and electrochemical properties of 1 μm and 5 μm thick TNT layers anodically grown on these substrates were examined and compared with TNT layers of the same thickness. No significant morphological and compositional differences were found using SEM (Scanning Electron Microscopy) and XPS (X-ray Photoelectron Spectroscopy) between the TNT layers grown on the two substrates. However, higher photocurrent densities and ICPE values were observed for TNT layers grown on electrodeposited Ti. An in-depth investigation using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) analyses showed increased conductivity of the TNT layers produced on electrodeposited Ti compared to their counterparts. The carrier density (ND) for the TNT layers on electrodeposited Ti, calculated from Mott-Schottky measurements, showed a higher doping level than the TNT layers grown on Ti foils. This increase in ND results in more optimal photoelectrochemical performance of the TNT layers grown on electrodeposited Ti. All in all, the results presented herein pave the way for the use of electrodeposited Ti, with all its inherent benefits, and allow the further study of its promising properties in a wide range of applications.

Development and Evaluation of the Joining Process of Gas Diffusion Layer and Membrane Electrode Assembly for PEM Fuel Cells

To achieve the goal of decarbonizing the heavy-duty transport sector, polymer electrolyte membrane (PEM) fuel cells need to be commercialized, and manufacturing processes must be optimized to meet the demands of industrial upscaling. By joining the anode and cathode gas diffusion layers (GDL) to the 5-layer membrane electrode assembly (MEA), the number of repeating units for the subsequent stacking process can be reduced from four to two. Hence, the stacking process time based on pick-and-place operations can be reduced by almost half. In the joined state, the relatively rigid GDL can also protect the fragile CCM from potential material damage caused by handling processes during stacking. Both literature and patent screening were conducted on possible joining options between the GDL and the 5-layer MEA. A low viscosity UV-activated adhesive was selected for the systematic investigation of the joining process. In order to achieve a highly precise and repeatable adhesive dispensing process within the scope of a roll-to-roll (R2R) MEA assembly system, a semi-automatic test rig was designed and built to bond the GDL to the 5-layer MEA. Various criteria for evaluating adhesive joint were analyzed and pre-selected, taking into account the economic factor, the quality of the joint, and the influence on downstream processes. A pre-activation strategy was deployed to successfully compensate for the adhesive absorption effect of the GDL due to its porous structure. A parameter combination of mass flow rate, joint design, applied pressure and curing strategy was found, where the adhesive bond between the GDL and the subgasket was sufficient for further manufacturing processes. With the developed joining process and the test rig, it is possible to create industrial process-like conditions and transfer the results to an industrial R2R MEA assembly process.© 2024 The Authors, Published by Elsevier B.V.5

A new nanostructured γ-Li3PO4/GeO2 composite for all-solid-state Li-ion battery applications.

High-temperature sintering is crucial to achieve good crystallinity and fast-ion conduction in oxide-type solid-electrolytes such as lithium garnets, NASICONs and LISICONs, leading to stiff ceramics which are difficult to integrate in all-solid-state batteries. Developing conventional oxide-based solid-electrolytes in deformable forms that maintain good ion transport properties and allow facile formulation of bulk-type solid-state batteries, hence, remains a challenge. Here, a new γ-Li3PO4/GeO2 composite, that adopts a novel nanostructured architecture and retains deformability after calcination at 500 °C, is successfully synthesized and densified by cold-pressing. Cold-pressed pellets of the new composite showed an ion conductivity that is four orders of magnitude higher than that of the parent γ-Li3PO4 and comparable to those of high-temperature stiff Li3+xP1-xGexO4 ceramics. The γ-Li3PO4/GeO2 composite is stable against high voltages (up to 5 V vs Li+/Li), which suggests a safe use in contact with high-voltage cathodes. The new composite can also be modified to serve as an active anode layer in solid-state cells due to the electrochemical activity of GeO2 at low voltages (<1 V vs. Li+/Li). This study emphasizes the potential of using low-temperature synthesis to develop novel oxide-based nanoarchitectures for all-solid-state battery applications.