Ultrathin Coatings Research Articles

Insights into the reactivity and lithium plating mechanisms of ultra-thin metal oxide coatings for anode-free solid-state lithium metal batteries

Solid-state batteries (SSBs) in an “anode-free” cell format using lithium metal anodes are the best candidates for high energy density battery applications. However, low lithium metal Coulombic efficiency and charge loss due to solid electrolyte interphase (SEI) formation severely limit the cycle life of anode-free SSBs. Here, we explore ultra-thin (5–20 nm) Al2O3 and ZnO coatings deposited by atomic layer deposition (ALD) on copper electrodes for anode-free cells with a solid polymer electrolyte. Voltammetry shows that lithium inventory loss from SEI formation is reduced over 50% with Al2O3@Cu electrodes, but these electrodes experience orders of magnitude higher interface resistances than bare Cu and ZnO@Cu electrodes due to low ionic and electronic conductivities. The electrochemical differences are reflected in XPS, where Al2O3 undergoes a self-limiting lithiation reaction with Li0, while ZnO reacts completely with Li0 to form LiZn and Li2O. These chemical differences result in higher and lower lithium plating nucleation overpotentials for Al2O3 (up to 220 mV) and ZnO (down to 15 mV) coatings, respectively, relative to uncoated Cu electrodes (35 mV). ToF-SIMS reveals lithium plating underneath a LiyAlOx coating and through emergent defects and pinholes with Al2O3@Cu electrodes, while it plates exclusively on top of converted ZnO@Cu electrodes. SEM corroborates these mechanisms, showing sparse coverage of isolated Li clusters plated with Al2O3@Cu electrodes, while Cu and ZnO@Cu grow more dense and interconnected deposits. Despite both coatings improving different aspects of anode-free battery design, unmodified Cu electrodes show higher Coulombic efficiencies (∼77%) than Al2O3@Cu (up to 70%) and ZnO@Cu (up to 75%) electrodes. Increasing Al2O3 thickness decreases the practical current density compared to unmodified Cu (30 µA/cm2), but increasing ZnO thicknesses can double or triple this value. These (electro)chemical and morphological observations suggest two mechanisms: less-reactive metal oxides develop lithium ion conductivity through their structure to plate lithium underneath, while more-reactive metal oxides undergo full reduction and conversion with lithium plating above the coating. This fundamental research opens future work to leverage these mechanisms and explore other materials for high-efficiency anode-free SSBs.

The role of atomic layer deposited coatings on lithium-ion transport: A comprehensive study

The use of ultrathin film coatings prepared through Atomic Layer Deposition (ALD) has become widespread for improving lithium-ion diffusivity of active particles, which plays a crucial role in determining the rate capability of Lithium-ion Batteries (LIBs). In this study, the impact of ALD coating thickness on ionic diffusivity in CeO2-coated LiMn2O4 (LMO) cathode particles is comprehensively investigated through first-principles calculations by focusing on the trade-offs between the physical properties of the film and its impact on the diffusivity of ions. Our findings indicate that several physical factors affect the diffusivity of the coating, including the crystal-amorphous structure that depends on thickness, as well as surface and bulk diffusion, and the influence of neighboring atoms. These factors contribute to the observed trade-offs in diffusivity. In addition, we observe a previously unknown phenomenon: variation in diffusivity along the thickness of the coating, which can be explained by the aforementioned physical factors. This study is the first to provide a fundamental atomic-level understanding of how the thickness of the coating affects the diffusivity of coated particles. Our findings provide valuable insights into the control of ALD coating thickness and the design of cathodes to improve the performance of LIBs.

Bio-AFM exploits enhanced response of human gingival fibroblasts on TiO2 nanotubular substrates with thin TiO2 coatings

The present work studies anodic TiO2 nanotube (TNT) layers and their surface modifications for enhancing the cell behavior of human gingival fibroblast cells (hGFs) with the contribution of bio-AFM (Atomic Force Microscopy) method. TNT layers, prepared via electrochemical anodization of Ti, with an average tube diameter of 15, 30, and 100 nm, were used as primary substrates for the study. Flat Ti foils were used as reference substrates. Part of the substrates was coated by ultrathin TiO2 coatings (≈ 0.3 nm thin) using Atomic Layer Deposition (ALD). The cell growth and adhesion of hGFs on the TNT layers and Ti foils were compared between ALD coated and uncoated ones. The supplemental coatings altered the surface chemistry of the TNT layers, particularly shading the fluorine and carbon impurities within anodic TiO2, while preserving the original structure and morphology. The presented approach of very mild surface modification remarkably effects the material's biocompatibility and possess great prospect as implant materials. For the first time, the TNT/cell interface was investigated using bio-AFM in terms of Young's modulus, stiffness, cell adhesive force and roughness. Improved biocompatibility was studied in terms of increased cell viability, density, cell cytoskeleton orientation and overall stiffness of the hGFs.

Experimental Investigation on Laser-Induced Electrochemical Silver Plating Technology.

The silver coating is widely used in electronic device manufacturing due to its excellent conductivity and soldering properties. Conventional preparation of local silver coating often uses the preplated silver, mask high-speed silver plating, and deplated silver processes. In this paper, the laser-induced electrodeposition technique is used to perform maskless laser-induced localized electrodeposition on a copper substrate preplated with a layer of silver. After the deplated silver process, ultrathin silver coatings with high dimensional accuracy, good corrosion resistance, and good bonding were obtained. The spatial distribution of the transient temperature field under laser irradiation is studied, the variation pattern of cathode substrate current under laser irradiation is tested, and finally, the spatial distribution of the pressure field under laser irradiation is simulated by Comsol. The effect of different laser scanning methods on the coating morphology was investigated, and the experimental study of the different single pulse energy-induced localized silver coatings was systematically carried out. The results show that the localized coating obtained by cross-line scanning with a laser single pulse energy of 93 μJ is flat with a film thickness of 0.23 μm, high dimensional accuracy, and good bonding force and corrosion resistance properties. This method provides a new approach for the preparation of a localized silver coating.

Transforming Spirulina maxima Biomass into Ultrathin Bioactive Coatings Using an Atmospheric Plasma Jet: A New Approach to Healing of Infected Wounds.

The challenge of wound healing, particularly in patients with comorbidities such as diabetes, is intensified by wound infection and the accelerating problem of bacterial resistance to current remedies such as antibiotics and silver. One promising approach harnesses the bioactive and antibacterial compound C-phycocyanin from the microalga Spirulina maxima. However, the current processes of extracting this compound and developing coatings are unsustainable and difficult to achieve. To circumvent these obstacles, a novel, sustainable argon atmospheric plasma jet (Ar-APJ) technology that transforms S. maxima biomass into bioactive coatings is presented. This Ar-APJ can selectively disrupt the cell walls of S. maxima, converting them into bioactive ultrathin coatings, which are found to be durable under aqueous conditions. The findings demonstrate that Ar-APJ-transformed bioactive coatings show better antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Moreover, these coatings exhibit compatibility with macrophages, induce an anti-inflammatory response by reducing interleukin 6 production, and promote cell migration in keratinocytes. This study offers an innovative, single-step, sustainable technology for transforming microalgae into bioactive coatings. The approach reported here has immense potential for the generation of bioactive coatings for combating wound infections and may offer a significant advance in wound care research and application.

Ultra-thin parylene-aluminium hybrid coatings on nanocellulose films to resist water sensitivity

Non-sustainable single-use plastics used for food packaging needs to be phased out. Films made from cellulose nanofibrils (CNFs) are suitable candidates for biodegradable and recyclable packaging materials as they exhibit good mechanical properties, excellent oxygen barrier properties and high transparency. Yet, their poor water vapour barrier properties have been a major hindrance in their commercialisation. Here, we describe the preparation of 25 μm thick CNF films with significantly improved water vapour barrier properties after deposition of ultrathin polymeric and metallic coatings, parylene C and aluminium, respectively. When first adding a 40 nm aluminium layer followed by an 80 nm parylene layer, i.e. with a combined thickness of less than one percent of the CNF film, a water vapour transmission rate of 2.8 g m−2 d−1 was achieved at 38 °C and 90 % RH, surpassing a 25 μm polypropylene film (4–12 g m−2 d−1). This is an improvement of more than 700 times compared to uncoated CNF films, under some of the harshest possible conditions a packaging material will need to endure in commercial use. The layers showed a good and even coverage, as assessed by atomic force microscopy, and the parylene-coated surfaces were hydrophobic with a contact angle of 110°, providing good water repellency.

Ag sputter coating of PLLA nonwovens

Abstract Physical vapor deposition (PVD) sputtering is a promising technique for the generation of electrically conductive coatings on complex structured biomaterials, such as nonwovens, that can be used in implants. The ultra-thin coatings can fulfil a variety of purposes, such as drug depot or biosensor. The aim of our studies was to determine the feasibility of generating thin silver (Ag) coatings on complex structured poly-L-lactide (PLLA) nonwovens by sputtering and their morphological characterization. PVD sputter process was performed using a customized plasma chamber and a complex rotation of the tender electrospun PLLA nonwovens. Morphological analysis revealed a promising homogenous Ag coating, representing the structure of the nonwovens.

Modification of ultrathin conversion coatings for AMg3 aluminum alloy and their interaction with painting system

Modification of ultrathin conversion coatings for AMg3 aluminum alloy and their interaction with painting system

Tunable Conformal Electrodeposition of Ultra-Thin Polymeric Films for Electrolyte Interphases

Functional coatings and interphases influence the stability and performance parameters of electrodes in various applications. Polymer thin films offer a wide range of molecular structures and compositions for tunable functionalities that can be custom designed to the needs of an application. In solid-state energy storage devices in particular, electrolyte-type polymeric interfaces between battery components and materials with disparate functions, such as the active electrode material and solid electrolyte could overcome some of these incompatibility detriments and the increase in contact resistance over long-term operation. In high-performance micro scale power sources, 3D thin-film all-solid-state batteries show great potential as they take advantage of both short ion diffusion distances for high-rate capability with low heat generation, as well as the third dimension for high material loading and energy density. Therefore, conformal deposition methods for ultra-thin polymeric electrolyte interphases on the interior surface of electrodes with mesoscale 3D architectures and complex porosity are in demand. Here, we report a molecular design concept of dual-functional molecules that contain electrochemically active end groups for self-limiting electropolymerization, and a core molecular motif that determines the thin film functionality. The electrodeposition of this monomer represents a non-line-of-sight coating method for polymer thin films with independently tailorable functionalities and tunable properties on conductive substrates with arbitrary shape. We exemplify this method using monomers with poly(ethylene glycol) (PEG) as the core motif for lithium-ion transport and phenol as electrochemically active end groups. We studied the electrodeposition of the monomers, poly(ethylene glycol) diphenol (PEGDP), and demonstrate their self-limiting film formation mechanism (Figure 1a) which originates from the insulating nature of resulting poly(PEGDP) film that confines the charge transfer reaction. We present an exhaustive exploration of their material-processing-structure-property relationships that reveals the multi-scale control over the ultrathin-film properties. For example, the uniform film thickness is tunable from 10 to 100s of nanometer through electrodeposition conditions and molecular design, while their molecular permeability and electronic resistance can be tailored from pervious to fully blocking. We show that the electrodeposited functional interphases fully coat complex 3D electrode architectures (Figure 1b top: uncoated carbon electrode, bottom: film coated carbon electrode) with retention of their functionality in a battery. This work demonstrates that rational molecular design enables the conformal electrodeposition of ultrathin functional coatings with solid polymer electrolyte properties on 3D structured electrodes that will enable designer interphases in various solid-state battery architectures and chemistries. Figure 1

LiBF4 Induced Unique Surface Modification Enables Improved Electrochemical Performance of LiNi0.8Co0.1Mn0.1O2 Cathode

AbstractLiNi0.8Co0.1Mn0.1O2 (NCM811) has been regarded as a potential cathode material for next‐generation lithium‐ion batteries. However, the electrochemical performance of this material is severely affected by structural deterioration and capacity degradation, and the residual lithium is one of the main culprits. Herein, we propose an effective strategy to design ultrathin coatings on the surface of NCM811 by using LiBF4 as the precursor. The homogeneous hybrid LiF‐Li2B4O7 coating layers can be obtained due to the reaction between LiBF4 and the residual lithium, which can not only effectively reduce the residual lithium, but also improve interfacial lithium‐ion diffusion kinetics and suppress side reactions. Accordingly, the LiBF4‐modified samples exhibited significantly improved electrochemical performance. The coated sample of NCM811@LBF‐0.7 delivers the 127.1 mAh g−1 discharge capacity with 69.8 % capacity retention even after 300 cycles at 1 C. While the pristine sample only shows 97.1 mAh g−1 and the capacity retention decreases to 31.0 %. This method provides a simple and effective strategy to extend the service life and safety characteristics of high‐energy‐density lithium‐ion batteries.

Vapour phase assembly of ultrathin coatings from alanine ternary complex on the carbon steel surface with enhanced corrosion resistance

ABSTRACT A novel alanine ternary complex (ALA-T) is prepared by the reaction of alanine (ALA), phosphoric acid, and dibutylamine. FTIR technique is used to characterise its structure. The weight-loss experiments in the closed space study the volatility of the alanine ternary complex. The ultrathin coating is formed on the surface of carbon steel by vapour phase assembly of the alanine ternary complex. The thickness of the coatings is measured using spectroscopic ellipsometry. The inhibition effect of ultrathin coatings on the corrosion of carbon steel is studied by the volatile-inhibiting ability (VIA) and the electrochemical tests. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are utilised to examine the morphology and composition of the carbon steel surface. It shows that the complex ultrathin coating has good corrosion inhibition for carbon steel. The protection mechanism of the ultrathin coating is discussed and analysed.

Process validation and a new method for quality control of ultrathin polyelectrolyte multilayer coatings

The properties of polyelectrolyte multilayers are ruled by the process parameters employed during self-assembly. This is the first study in which a design of experiment approach was used to validate and control the production of ultrathin polyelectrolyte multilayer coatings by identifying the ranges of critical process parameters (polyelectrolyte concentration, ionic strength and pH) within which coatings with reproducible properties (thickness, refractive index and hydrophilicity) are created. Mathematical models describing the combined impact of key process parameters on coatings properties were developed demonstrating that only ionic strength and pH affect the coatings thickness, but not polyelectrolyte concentration. While the electrolyte concentration had a linear effect, the pH contribution was described by a quadratic polynomial. A significant contribution of this study is the development of a new approach to estimate the thickness of polyelectrolyte multilayer nanofilms by quantitative rhodamine B staining, which might be useful in all cases when ellipsometry is not feasible due to the shape complexity or small size of the coated substrate. The novel approach proposed here overcomes the limitations of known methods as it offers a low spatial sampling size and the ability to analyse a wide area without restrictions on the chemical composition and shape of the substrate.

Morphology of ultrathin gold and copper coatings thermally evaporated on polydimethylsiloxane elastomers: From isolated nanoparticles to continuous coatings

This article presents a morphological study of ultrathin gold and copper coatings (between 1 nm and 20 nm equivalent metal thickness) thermally evaporated on polydimethylsiloxane (PDMS). Results are discussed on the basis of transmission electron microscopy and atomic force microscopy. Gold is demonstrated to grow in the form of isolated particles following a Volmer-Weber growth mode, whereas copper more likely grows in the form of a continuous film, following a Stranski–Krastanov growth mode. Our results demonstrate a negligible role of the PDMS elastic modulus (between 0.5 and 2.5 MPa) in the gold and copper coatings morphology respectively. However, significant morphological changes are observed when the metals are thermally evaporated on a PDMS substrate of extremely higher surface elastic modulus obtained after O2 plasma exposure.

Deposition of ultra-thin coatings by a nature-inspired Spray-on-Screen technology

Nanometre-thick, ultrathin coatings applied over a large area are of paramount importance for various application fields such as biomedicine, space and automotive, organic electronics, memory devices, or energy storage devices. So far wet chemical deposition as a cost-effective, scalable, and versatile method can only be used for thicker deposits. Here the formation of uniform ultra-thin coatings with thicknesses below 15 nm using a nature-inspired, roll-to-roll compatible Spray-on-Screen (SoS) technology is reported. For this, the finite micro-droplet generation of Ultrasonic Spray Coating (USSC) is combined with the coating formation from a screen printing mesh. Hydrophobic micro-threads of the mesh, resembling the micro-hair on the legs of water striders, produce millidroplets from micro droplets, and when applying an external pressure to the mesh, dynamic wetting is enforced. The proposed technology is applicable for a wide variety of substrates and applications. It is shown by theory and experiment that ultra-thin coatings below 5 nm homogeneous over a large area can be deposited without the use of extended ink formulation or high substrate temperatures during or after deposition. This simple yet effective technique enables the deposition of ultra-thin films on any substrates, and is very promising to fabricate the organic, inorganic electronics devices and batteries cost effectively.

Electrically Conductive and Highly Stretchable Piezoresistive Polymer Nanocomposites via Oxidative Chemical Vapor Deposition.

Electrically conductive polymer nanocomposites have been the subject of intense research due to their promising potential as piezoresistive biomedical sensors, leveraging their flexibility and biocompatibility. Although intrinsically conductive polymers such as polypyrrole (PPy) and polyaniline have emerged as lucrative candidates, they are extremely limited in their processability by conventional solution-based approaches. In this work, ultrathin nanostructured coatings of doped PPy are realized on polyurethane films of different architectures via oxidative chemical vapor deposition to develop stretchable and flexible resistance-based strain sensors. Holding the substrates perpendicular to the reactant flows facilitates diffusive transport and ensures excellent conformality of the interfacial integrated PPy coatings throughout the 3D porous electrospun fiber mats in a single step. This allows the mechanically robust (stretchability > 400%, with fatigue resistance up to 1000 cycles) nanocomposites to elicit a reversible change of electrical resistance when subjected to consecutive cycles of stretching and releasing. The repeatable performance of the strain sensor is linear due to dimensional changes of the conductive network in the low-strain regime (ε ≤ 50%), while the evolution of nano-cracks leads to an exponential increase, which is observed in the high-strain regime, recording a gauge factor as high as 46 at 202% elongational strain. The stretchable conductive polymer nanocomposites also show biocompatibility toward human dermal fibroblasts, thus providing a promising path for use as piezoresistive strain sensors and finding applications in biomedical applications such as wearable, skin-mountable flexible electronics.

Wrapping up Metal–Organic Framework Crystals with Carbon Nanotubes

AbstractThe presence of tetrazine units in the organic nodes of UiO‐68‐TZCD controls the formation of ultrathin coatings of single‐wall nanotubes that decorate the surface of the crystal. These crystal hybrids can be prepared straightforwardly in one step and are extraordinarily respectful with the properties of the framework for combination of mesoporosity and surface areas ≈4.000 m2 g−1, with excellent stability in water, and conductivities at room temperature of 4 × 10−2 S cm−1 even at very low carbon weight contents (2.3 wt.%).

Hydrogen and deuterium permeation on niobium coated by ultrathin Pd25%Ag for tritium recovery in EU DEMO

The hydrogen and deuterium permeation in pure niobium and niobium Pd25%Ag coated are measured using a permeation gas phase technique. The coating with different thicknesses, are deposited on Nb by a Dual Ion Beam Sputtering Technique. Measurements are performed in the temperature range of 573–723 K with hydrogen or deuterium driving pressures in the range 1.0⋅102−1.2⋅104 Pa (1 to 120 mbar). This work highlights how PdAg-coated Nb membranes can be fruitfully rated in the design of tritium recovery plants where niobium pipes for lead lithium are under consideration. Ultra-thin PdAg coatings mitigate the effects of the oxide in reducing of hydrogen permeation through the niobium walls.

Metrological Comparison of Available Methods to Correct Edge-Effect Local Plasticity in Instrumented Indentation Test.

The Instrumented Indentation Test (IIT) mechanically characterizes materials from the nano to the macro scale, enabling the evaluation of microstructure and ultra-thin coatings. IIT is a non-conventional technique applied in strategic sectors, e.g., automotive, aerospace and physics, to foster the development of innovative materials and manufacturing processes. However, material plasticity at the indentation edge biases the characterization results. Correcting such effects is extremely challenging, and several methods have been proposed in the literature. However, comparisons of these available methods are rare, often limited in scope, and neglect metrological performance of the different methods. After reviewing the main available methods, this work innovatively proposes a performance comparison within a metrological framework currently missing in the literature. The proposed framework for performance comparison is applied to some available methods, i.e., work-based, topographical measurement of the indentation to evaluate the area and the volume of the pile-up, Nix-Gao model and the electrical contact resistance (ECR) approach. The accuracy and measurement uncertainty of the correction methods is compared considering calibrated reference materials to establish traceability of the comparison. Results, also discussed in light of the practical convenience of the methods, show that the most accurate method is the Nix-Gao approach (accuracy of 0.28 GPa, expanded uncertainty of 0.57 GPa), while the most precise is the ECR (accuracy of 0.33 GPa, expanded uncertainty of 0.37 GPa), which also allows for in-line and real-time corrections.

Ultrathin Carbon Coating and Defect Engineering Promote RuO2 as an Efficient Catalyst for Acidic Oxygen Evolution Reaction with Super‐High Durability (Adv. Energy Mater. 23/2023)

Acidic OER Catalysts In article number 2300152, Zhong-Jie Jiang and co-workers use a strategy of ultrathin carbon coating and oxygen-vacancy generation to improve the activity and stability of the RuO2 nano-catalysts towards the acidic oxygen evolution reaction. The obtained catalyst only needs an overpotential of 170.0 mV to drive 10.0 mA cm−2 and shows a mass activity 110 times higher than the commercial RuO2.

Corrosion prevention and control using in situ phase layers formation via application of the complexing‐type inhibitors

AbstractA set of organic ligands of different natures has been investigated as complexing‐type corrosion inhibitors for the protection of low carbon steel in an acidic medium. The inhibitive mechanism implying the formation of phase protective layers on the metal surface as a result of the complexation process of added organic ligands with the metal cations is being discussed. The results of the investigation of the influence of pH and temperature conditions on the phase layers formation dynamics have been presented. A range of practical aspects of the application of organic ligands as complexing‐type inhibitors for the formation of ultrathin coatings have been discussed. The stability constant of the metal–ligand complex and its solubility have been proposed as the basis of a predictive model for analytical assessment of their potential protective efficiency.