Emerging applications of atomic layer deposition for lithium-ion battery studies

Nanoprocess and nanoscale surface functionalization on cathode materials for advanced lithium-ion batteries

Nanotechnology-driven development of cathode materials is an essential part to revolutionize the evolution of the next generation lithium ion batteries. With the progress of nanoprocess and nanoscale surface modification investigations on cathode materials in recent years, the advanced battery technology future seems very promising - Thanks to nanotechnology. In this review, an overview of promising nanoscale surface deposition methods and their significance in surface functionalization on cathodes is extensively summarized. Surface modified cathodes are provided with a protective layer to overcome the electrochemical performance limitations related to side reactions with electrolytes, reduce self-discharge reactions, improve thermal and structural stability, and further enhance the overall battery performance. The review addresses the importance of nanoscale surface modification on battery cathodes and concludes with a comparison of the different nanoprocess techniques discussed to provide a direction in the race to build advanced lithium-ion batteries.

Recent Progresses and Development of Advanced Atomic Layer Deposition towards High-Performance Li-Ion Batteries

Electrode materials and electrolytes play a vital role in device-level performance of rechargeable Li-ion batteries (LIBs). However, electrode structure/component degeneration and electrode-electrolyte sur-/interface evolution are identified as the most crucial obstacles in practical applications. Thanks to its congenital advantages, atomic layer deposition (ALD) methodology has attracted enormous attention in advanced LIBs. This review mainly focuses upon the up-to-date progress and development of the ALD in high-performance LIBs. The significant roles of the ALD in rational design and fabrication of multi-dimensional nanostructured electrode materials, and finely tailoring electrode-electrolyte sur-/interfaces are comprehensively highlighted. Furthermore, we clearly envision that this contribution will motivate more extensive and insightful studies in the ALD to considerably improve Li-storage behaviors. Future trends and prospects to further develop advanced ALD nanotechnology in next-generation LIBs were also presented.

Remodeling Tau and Prion Proteins Using Nanochaperons

There is increasing evidence that tau protein behaves in a prion-like manner in tauopathy. The stabilization of tau protein using a small molecular compound can limit tauopathy associated morbidity that advances with ageing. Here, a lab-on-a-chip experiment is reported, where gold citrate nanoparticles (5 nm, AuNPs) can remodel mutant tau protein (P301L) and prion, thus resolving the mutant tau- and prion-mediated impairment of kinesin cargo transport on microtubules. It is found that tau protein is overexpressed in Alzheimer's disease (AD) patient serum samples and the tau conformational change can also be affected in human serum samples of AD when treated with AuNPs ex vivo. Similarly, AuNPs reorganizing the prion protein and inducing conformational changes of prions in AD serum have been observed, while having no effect on alpha-synuclein in Parkinson patient serum. The mapping of AD serum mediated traffic jams, using particle tracking and mean square displacement analysis, and the observed recovery of uninterrupted processive motor functions by AuNP treatment show that kinesin cargo assays might be a useful method for future ex vivo validation of a targeted therapy against tauopathy before administration, a viable option to combat various neurodegenerative disorders arising from the susceptibility of amyloidogenic proteins toward aggregation.

Atomic Layer Deposited Lithium Silicates as Solid-State Electrolytes for All-Solid-State Batteries

Development of solid-state electrolyte (SSE) thin films is a key toward the fabrication of all-solid-state batteries (ASSBs). However, it is challenging for conventional deposition techniques to deposit uniform and conformal SSE thin films in a well-controlled fashion. In this study, atomic layer deposition (ALD) was used to fabricate lithium silicate thin films as a potential SSE for ASSBs. Lithium silicates thin films were deposited by combining ALD Li₂O and SiO₂ subcycles using lithium tert-butoxide, tetraethylorthosilane, and H₂O as precursors. Uniform and self-limiting growth was achieved at temperatures between 225 and 300 °C. X-ray absorption spectroscopy analysis disclosed that the as-deposited lithium silicates were composed of SiO₄ tetrahedron structure and lithium oxide as the network modifier. X-ray photoelectron spectroscopy confirmed the chemical states of Li in the thin films were the same with that in standard lithium silicate. With one to one subcycle of Li₂O and SiO₂ the thin films had a composition close to Li₄SiO₄ whereas one more subcycle of Li₂O delivered a higher lithium content. The lithium silicate thin film prepared at 250 °C exhibited an ionic conductivity of 1.45× 10^-6 S cm^-1 at 373 K. The high ionic conductivity of lithium silicate was due to the higher lithium concentration and lower activation energy.

Inorganic-Organic Coating via Molecular Layer Deposition Enables Long Life Sodium Metal Anode

Metallic Na anode is considered as a promising alternative candidate for Na ion batteries (NIBs) and Na metal batteries (NMBs) due to its high specific capacity, and low potential. However, the unstable solid electrolyte interphase layer caused by serious corrosion and reaction in electrolyte will lead to big challenges, including dendrite growth, low Coulombic efficiency and even safety issues. In this paper, we first demonstrate the inorganic-organic coating via advanced molecular layer deposition (alucone) as a protective layer for metallic Na anode. By protecting Na anode with controllable alucone layer, the dendrites and mossy Na formation have been effectively suppressed and the lifetime has been significantly improved. Moreover, the molecular layer deposition alucone coating shows better performances than the atomic layer deposition Al₂O₃ coating. The novel design of molecular layer deposition protected Na metal anode may bring in new opportunities to the realization of the next-generation high energy-density NIBs and NMBs.

High performance asymmetric V2O5-SnO2 nanopore battery by atomic layer deposition

Here we report the high performance and cyclability of an asymmetric full cell nanopore battery, comprised of V₂O₅ as the cathode and prelithiated SnO₂ as the anode, with integrated nanotubular Pt current collectors underneath each nanotubular storage electrode, confined within an anodized aluminium oxide (AAO) nanopore. Enabled by atomic layer deposition (ALD), this coaxial nanotube full cell is fully confined within a high aspect ratio nanopore (150 nm in diameter, 50 μm in length), with an ultra-small volume of about 1 fL. By controlling the amount of lithium ion prelithiated into the SnO₂ anode, we can tune the full cell output voltage in the range of 0.3 V to 3 V. When tested as a massively parallel device (∼2 billion cm^-2), this asymmetric nanopore battery array displays exceptional rate performance and cyclability: when cycled between 1 V and 3 V, capacity retention at the 200C rate is ∼73% of that at 1C, and at 25C rate only 2% capacity loss occurs after more than 500 charge/discharge cycles. With the increased full cell output potential, the asymmetric V₂O₅-SnO₂ nanopore battery shows significantly improved energy and power density over the previously reported symmetric cell, 4.6 times higher volumetric energy and 5.2 times higher power density - an even more promising indication that controlled nanostructure designs employing nanoconfined environments with large electrode surface areas present promising directions for future battery technology.

Role of graphene in enhancing the mechanical properties of TiO2/graphene heterostructures

Graphene has been integrated in many heterogeneous structures in order to take advantage of its superior mechanical properties. However, the complex mechanical response of heterogeneous films incorporating graphene is not well understood. Here, we studied the mechanical behavior of atomic layer deposition (ALD) synthesized TiO₂/graphene, as a representative building block of a typical composite, to understand the mechanical behavior of heterostructures using an experiment-computational approach. The inclusion of graphene was found to significantly enhance the Young's modulus of TiO₂/graphene hetero-films for films below a critical thickness of 3 nm, beyond which the Young's modulus approaches that of pure TiO₂ film. A rule-of-mixtures was found to reasonably estimate the modulus of the TiO₂/graphene hetero-film. Experimentally, these hetero-films were observed to fail via brittle fracture. Complimentary density functional theory and finite element modeling demonstrates strong adhesion at the graphene TiO₂ interface and that graphene serves as a reinforcement, providing the hetero-film with an ability to sustain significantly high stresses at the point of failure initiation. The results and methodology described herein can contribute to the rational design of strong and reliable ultrathin hetero-films for versatile applications.

Atomic-Layer-Deposition Assisted Formation of Wafer-Scale Double-Layer Metal Nanoparticles with Tunable Nanogap for Surface-Enhanced Raman Scattering

A simple high-throughput approach is presented in this work to fabricate the Au nanoparticles (NPs)/nanogap/Au NPs structure for surface enhanced Raman scattering (SERS). This plasmonic nanostructure can be prepared feasibly by the combination of rapid thermal annealing (RTA), atomic layer deposition (ALD) and chemical etching process. The nanogap size between Au NPs can be easily and precisely tuned to nanometer scale by adjusting the thickness of sacrificial ALD Al₂O₃ layer. Finite-difference time-domain (FDTD) simulation data indicate that most of enhanced field locates at Au NPs nanogap area. Moreover, Au NPs/nanogap/Au NPs structure with smaller gap exhibits the larger electromagnetic field. Experimental results agree well with FDTD simulation data, the plasmonic structure with smaller nanogap size has a stronger Raman intensity. There is highly strong plasmonic coupling in the Au nanogap, so that a great SERS effect is obtained when detecting methylene blue (MB) molecules with an enhancement factor (EF) over 10⁷. Furthermore, this plasmonic nanostructure can be designed on large area with high density and high intensity hot spots. This strategy of producing nanoscale metal gap on large area has significant implications for ultrasensitive Raman detection and practical SERS application.

Superior Stable and Long Life Sodium Metal Anodes Achieved by Atomic Layer Deposition

Na-metal batteries are considered as the promising alternative candidate for Li-ion battery beneficial from the wide availability and low cost of sodium, high theoretical specific capacity, and high energy density based on the plating/stripping processes and lowest electrochemical potential. For Na-metal batteries, the crucial problem on metallic Na is one of the biggest challenges. Mossy or dendritic growth of Na occurs in the repetitive Na stripping/plating process with an unstable solid electrolyte interphase layer of nonuniform ionic flux, which can not only lead to the low Coulombic efficiency, but also can create short circuit risks, resulting in possible burning or explosion. In this communication, the atomic layer deposition of Al₂ O₃ coating is first demonstrated for the protection of metallic Na anode for Na-metal batteries. By protecting Na foil with ultrathin Al₂ O₃ layer, the dendrites and mossy Na formation have been effectively suppressed and lifetime has been significantly improved. Furthermore, the thickness of protective layer has been further optimized with 25 cycles of Al₂ O₃ layer presenting the best performance over 500 cycles. The novel design of atomic layer deposition protected metal Na anode may bring in new opportunities to the realization of the next-generation high energy-density Na metal batteries.

Porous One-Dimensional Nanomaterials: Design, Fabrication and Applications in Electrochemical Energy Storage

Electrochemical energy storage technology is of critical importance for portable electronics, transportation and large-scale energy storage systems. There is a growing demand for energy storage devices with high energy and high power densities, long-term stability, safety and low cost. To achieve these requirements, novel design structures and high performance electrode materials are needed. Porous 1D nanomaterials which combine the advantages of 1D nanoarchitectures and porous structures have had a significant impact in the field of electrochemical energy storage. This review presents an overview of porous 1D nanostructure research, from the synthesis by bottom-up and top-down approaches with rational and controllable structures, to several important electrochemical energy storage applications including lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-oxygen batteries and supercapacitors. Highlights of porous 1D nanostructures are described throughout the review and directions for future research in the field are discussed at the end.

Amorphous and Crystalline Vanadium Oxides as High-Energy and High-Power Cathodes for Three-Dimensional Thin-Film Lithium Ion Batteries

Flexible wearable electronics and on-chip energy storage for wireless sensors drive rechargeable batteries toward thin-film lithium ion batteries. To enable more charge storage on a given surface, higher energy density materials are required, while faster energy storage and release can be obtained by going to thinner films. Vanadium oxides have been examined as cathodes in classical and thin-film lithium ion batteries for decades, but amorphous vanadium oxide thin films have been mostly discarded. Here, we investigate the use of atomic layer deposition, which enables electrode deposition on complex three-dimensional (3D) battery architectures, to obtain both amorphous and crystalline VO₂ and V₂O₅, and we evaluate their thin-film cathode performance. Very high volumetric capacities are found, alongside excellent kinetics and good cycling stability. Better kinetics and higher volumetric capacities were observed for the amorphous vanadium oxides compared to their crystalline counterparts. The conformal deposition of these vanadium oxides on silicon micropillar structures is demonstrated. This study shows the promising potential of these atomic layer deposited vanadium oxides as cathodes for 3D all-solid-state thin-film lithium ion batteries.

Atomic Layer Deposition Alumina-Passivated Silicon Nanowires: Probing the Transition from Electrochemical Double-Layer Capacitor to Electrolytic Capacitor

Silicon nanowires were coated by a 1-5 nm thin alumina layer by atomic layer deposition (ALD) in order to replace poorly reproducible and unstable native silicon oxide by a highly conformal passivating alumina layer. The surface coating enabled probing the behavior of symmetric devices using such electrodes in the EMI-TFSI electrolyte, allowing us to attain a large cell voltage up to 6 V in ionic liquid, together with very high cyclability with less than 4% capacitance fade after 10⁶ charge/discharge cycles. These results yielded fruitful insights into the transition between an electrochemical double-layer capacitor behavior and an electrolytic capacitor behavior. Ultimately, thin ALD dielectric coatings can be used to obtain hybrid devices exhibiting large cell voltage and excellent cycle life of dielectric capacitors, while retaining energy and power densities close to the ones displayed by supercapacitors.

Heterogeneous TiO2/V2O5/Carbon Nanotube Electrodes for Lithium-Ion Batteries

Vanadium pentoxide (V₂O₅) is proposed and investigated as a cathode material for lithium-ion (Li-ion) batteries. However, the dissolution of V₂O₅ during the charge/discharge remains as an issue at the V₂O₅-electrolyte interface. In this work, we present a heterogeneous nanostructure with carbon nanotubes supported V₂O₅/titanium dioxide (TiO₂) multilayers as electrodes for thin-film Li-ion batteries. Atomic layer deposition of V₂O₅ on carbon nanotubes provides enhanced Li storage capacity and high rate performance. An additional TiO₂ layer leads to increased morphological stability and in return higher electrochemical cycling performance of V₂O₅/carbon nanotubes. The physical and chemical properties of TiO₂/V₂O₅/carbon nanotubes are characterized by cyclic voltammetry and charge/discharge measurements as well as electron microscopy. The detailed mechanism of the protective TiO₂ layer to improve the electrochemical cycling stability of the V₂O₅ is unveiled.

Atomic and molecular layer deposition: off the beaten track

ALD archetype and deviations from it.

Molecular layer deposition of “vanadicone”, a vanadium-based hybrid material, as an electrode for lithium-ion batteries

Post-deposition heat treatments activate MLD vanadicone as a lithium-ion battery electrode.

Plasma-assisted and thermal atomic layer deposition of electrochemically active Li2CO3

Growth per cycle as a function of process table temperature for both plasma-assisted (squares) and thermal (circles) ALD processes.

Advances in electrode materials for Li-based rechargeable batteries

We summarize strategies to enhance the performance of electrode materials for Li-based batteries through nanoengineering and surface coating, and introduce new trends in developing alternative materials, battery concepts and cell configurations.

The role of nanotechnology in the development of battery materials for electric vehicles

A significant amount of battery research and development is underway, both in academia and industry, to meet the demand for electric vehicle applications. When it comes to designing and fabricating electrode materials, nanotechnology-based approaches have demonstrated numerous benefits for improved energy and power density, cyclability and safety. In this Review, we offer an overview of nanostructured materials that are either already commercialized or close to commercialization for hybrid electric vehicle applications, as well as those under development with the potential to meet the requirements for long-range electric vehicles.

Porous NASICON-Type Li3Fe2(PO4)3 Thin Film Deposited by RF Sputtering as Cathode Material for Li-Ion Microbatteries

We report the electrochemical performance of porous NASICON-type Li3Fe2(PO4)3 thin films to be used as a cathode for Li-ion microbatteries. Crystalline porous NASICON-type Li3Fe2(PO4)3 layers were obtained by radio frequency sputtering with an annealing treatment. The thin films were characterized by XRD, SEM, and electrochemical techniques. The chronoamperometry experiments showed that a discharge capacity of 88 mAhg(-1) (23 μAhcm(-2)) is attained for the first cycle at C/10 to reach 65 mAhg(-1) (17 μAhcm(-2)) after 10 cycles with a good stability over 40 cycles.

A Selectively Permeable Membrane for Enhancing Cyclability of Organic Sodium-Ion Batteries

A novel strategy to enhance the cyclability of organic sodium-ion batteries is developed by applying a selectively permeable membrane to allow the passage of Na ions but block the slightly dissolved active molecules and thereby inhibit the further dissolution. After utilization of the membrane, the batteries show highly enhanced cyclability. Such strategy can be potentially extended to many organic materials with low solubilities.

Recent Development of Advanced Electrode Materials by Atomic Layer Deposition for Electrochemical Energy Storage

Electrode materials play a decisive role in almost all electrochemical energy storage devices, determining their overall performance. Proper selection, design and fabrication of electrode materials have thus been regarded as one of the most critical steps in achieving high electrochemical energy storage performance. As an advanced nanotechnology for thin films and surfaces with conformal interfacial features and well controllable deposition thickness, atomic layer deposition (ALD) has been successfully developed for deposition and surface modification of electrode materials, where there are considerable issues of interfacial and surface chemistry at atomic and nanometer scale. In addition, ALD has shown great potential in construction of novel nanostructured active materials that otherwise can be hardly obtained by other processing techniques, such as those solution-based processing and chemical vapor deposition (CVD) techniques. This review focuses on the recent development of ALD for the design and delivery of advanced electrode materials in electrochemical energy storage devices, where typical examples will be highlighted and analyzed, and the merits and challenges of ALD for applications in energy storage will also be discussed.

Sodium-Oxygen Batteries: A Comparative Review from Chemical and Electrochemical Fundamentals to Future Perspective

Alkali metal-oxygen (Li-O2 , Na-O2 ) batteries have attracted a great deal of attention recently due to their high theoretical energy densities, comparable to gasoline, making them attractive candidates for application in electrical vehicles. However, the limited cycling life and low energy efficiency (high charging overpotential) of these cells hinder their commercialization. The Li-O2 battery system has been extensively studied in this regard during the past decade. Compared to the numerous reports of Li-O2 batteries, the research on Na-O2 batteries is still in its infancy. Although, Na-O2 batteries show a number of attractive properties such as low charging overpotential and high round-trip energy efficiency, their cycling life is currently limited to a few tens of cycles. Therefore, understanding the chemistry behind Na-O2 cells is critical towards enhancing their performance and advancing their development. Chemical and electrochemical reactions of Na-O2 batteries are reviewed and compared with those of Li-O2 batteries in the present review, as well as recent works on the chemical composition and morphology of the discharge products in these batteries. Furthermore, the determining kinetics factors for controlling the chemical composition of the discharge products in Na-O2 cells are discussed and the potential research directions toward improving Na-O2 cells are proposed.

High Pressure Chemical Vapor Deposition of Hydrogenated Amorphous Silicon Films and Solar Cells

Thin films of hydrogenated amorphous silicon can be produced at MPa pressures from silane without the use of plasma at temperatures as low as 345 °C. High pressure chemical vapor deposition may open a new way to low cost deposition of amorphous silicon solar cells and other thin film structures over very large areas in very compact, simple reactors.

Safe and Durable High-Temperature Lithium-Sulfur Batteries via Molecular Layer Deposited Coating

Lithium-sulfur (Li-S) battery is a promising high energy storage candidate in electric vehicles. However, the commonly employed ether based electrolyte does not enable to realize safe high-temperature Li-S batteries due to the low boiling and flash temperatures. Traditional carbonate based electrolyte obtains safe physical properties at high temperature but does not complete reversible electrochemical reaction for most Li-S batteries. Here we realize safe high temperature Li-S batteries on universal carbon-sulfur electrodes by molecular layer deposited (MLD) alucone coating. Sulfur cathodes with MLD coating complete the reversible electrochemical process in carbonate electrolyte and exhibit a safe and ultrastable cycle life at high temperature, which promise practicable Li-S batteries for electric vehicles and other large-scale energy storage systems.

Hierarchical Carbon with High Nitrogen Doping Level: A Versatile Anode and Cathode Host Material for Long-Life Lithium-Ion and Lithium-Sulfur Batteries

Nitrogen-rich carbon with both a turbostratic microstructure and meso/macroporosity was prepared by hard templating through pyrolysis of a tricyanomethanide-based ionic liquid in the voids of a silica monolith template. This multifunctional carbon not only is a promising anode candidate for long-life lithium-ion batteries but also shows favorable properties as anode and cathode host material owing to a high nitrogen content (>8% after carbonization at 900 °C). To demonstrate the latter, the hierarchical carbon was melt-infiltrated with sulfur as well as coated by atomic layer deposition (ALD) of anatase TiO2, both of which led to high-quality nanocomposites. TiO2 ALD increased the specific capacity of the carbon while maintaining high Coulombic efficiency and cycle life: the composite exhibited stable performance in lithium half-cells, with excellent recovery of low rate capacities after thousands of cycles at 5C. Lithium-sulfur batteries using the sulfur/carbon composite also showed good cyclability, with reversible capacities of ∼700 mA·h·g(-1) at C/5 and without obvious decay over several hundred cycles. The present results demonstrate that nitrogen-rich carbon with an interconnected multimodal pore structure is very versatile and can be used as both active and inactive electrode material in high-performance lithium-based batteries.

Ultrafast triggered transient energy storage by atomic layer deposition into porous silicon for integrated transient electronics

Here we demonstrate the first on-chip silicon-integrated rechargeable transient power source based on atomic layer deposition (ALD) coating of vanadium oxide (VOx) into porous silicon. A stable specific capacitance above 20 F g(-1) is achieved until the device is triggered with alkaline solutions. Due to the rational design of the active VOx coating enabled by ALD, transience occurs through a rapid disabling step that occurs within seconds, followed by full dissolution of all active materials within 30 minutes of the initial trigger. This work demonstrates how engineered materials for energy storage can provide a basis for next-generation transient systems and highlights porous silicon as a versatile scaffold to integrate transient energy storage into transient electronics.

Solid Electrolyte Lithium Phosphous Oxynitride as a Protective Nanocladding Layer for 3D High-Capacity Conversion Electrodes

Materials that undergo conversion reactions to form different materials upon lithiation typically offer high specific capacity for energy storage applications such as Li ion batteries. However, since the reaction products often involve complex mixtures of electrically insulating and conducting particles and significant changes in volume and phase, the reversibility of conversion reactions is poor, preventing their use in rechargeable (secondary) batteries. In this paper, we fabricate and protect 3D conversion electrodes by first coating multiwalled carbon nanotubes (MWCNT) with a model conversion material, RuO2, and subsequently protecting them with conformal thin-film lithium phosphous oxynitride (LiPON), a well-known solid-state electrolyte. Atomic layer deposition is used to deposit the RuO2 and the LiPON, thus forming core double-shell MWCNT@RuO2@LiPON electrodes as a model system. We find that the LiPON protection layer enhances cyclability of the conversion electrode, which we attribute to two factors. (1) The LiPON layer provides high Li ion conductivity at the interface between the electrolyte and the electrode. (2) By constraining the electrode materials mechanically, the LiPON protection layer ensures electronic connectivity and thus conductivity during lithiation/delithiation cycles. These two mechanisms are striking in their ability to preserve capacity despite the profound changes in structure and composition intrinsic to conversion electrode materials. This LiPON-protected structure exhibits superior cycling stability and reversibility as well as decreased overpotentials compared to the unprotected core-shell structure. Furthermore, even at very low lithiation potential (0.05 V), the LiPON-protected electrode largely reduces the formation of a solid electrolyte interphase.

Atomic/Molecular Layer Deposition of Lithium Terephthalate Thin Films as High Rate Capability Li-Ion Battery Anodes

We demonstrate the fabrication of high-quality electrochemically active organic lithium electrode thin films by the currently strongly emerging combined atomic/molecular layer deposition (ALD/MLD) technique using lithium terephthalate, a recently found anode material for lithium-ion battery (LIB), as a proof-of-the-concept material. Our deposition process for Li-terephthalate is shown to well comply with the basic principles of ALD-type growth including the sequential self-saturated surface reactions, a necessity when aiming at micro-LIB devices with three-dimensional architectures. The as-deposited films are found crystalline across the deposition temperature range of 200-280 °C, which is a trait highly desired for an electrode material but rather unusual for hybrid inorganic-organic thin films. Excellent rate capability is ascertained for the Li-terephthalate films with no conductive additives required. The electrode performance can be further enhanced by depositing a thin protective LiPON solid-state electrolyte layer on top of Li-terephthalate; this yields highly stable structures with capacity retention of over 97% after 200 charge/discharge cycles at 3.2 C.

Atomic layer deposition of vanadium oxides for thin-film lithium-ion battery applications

A wide range of vanadium oxides is demostrated as lithium ion cathodes by a combination of ALD and post-ALD anneal, with lithium insertion capacities up to 1380 mAh cm⁻³.

High-voltage capabilities of ultra-thin Nb2O5 nanosheet coated LiNi1/3Co1/3Mn1/3O2 cathodes

The surface coating of LiNi_1/3Co_1/3Mn_1/3 electrode with 1.1 nm Nb₂O₅ nanosheet enhanced the high voltage capability and long term stability of the charged state at 60 °C by reducing the contact area between electrode and electrolyte.

Enhanced cycle life and capacity retention of iron oxide ultrathin film coated SnO2 nanoparticles at high current densities

Optimally thick and conformal iron oxide (FeOx) ultrathin films coated on SnO₂ nanoparticles by atomic layer deposition significantly improve the cycle life and capacity retention when operated in a practical voltage window at high current densities.

Ultrafine ferroferric oxide nanoparticles embedded into mesoporous carbon nanotubes for lithium ion batteries

An effective one-pot hydrothermal method for in situ filling of multi-wall carbon nanotubes (CNT, diameter of 20–40 nm, length of 30–100 μm) with ultrafine ferroferric oxide (Fe₃O₄) nanoparticles (8–10 nm) has been demonstrated. The synthesized Fe₃O₄@CNT exhibited a mesoporous texture with a specific surface area of 109.4 m² g⁻¹. The loading of CNT, in terms of the weight ratio of Fe₃O₄ nanoparticles, can reach as high as 66.5 wt%. Compared to the conventional method of using a Al₂O₃ membrane as template to fill CNT with iron oxides nanoparticles, our strategy is facile, effective, low cost and easy to scale up to large scale production (~1.42 g per one-pot). When evaluated for lithium storage at 1.0 C (1 C = 928 mA g⁻¹), the mesoporous Fe₃O₄@CNT can retain at 358.9 mAh g⁻¹ after 60 cycles. Even when cycled at high rate of 20 C, high capacity of 275.2 mAh g⁻¹ could still be achieved. At high rate (10 C) and long life cycling (500 cycles), the cells still exhibit a good capacity of 137.5 mAhg⁻¹.

Enhancing the High-Voltage Cycling Performance of LiNi(0.5)Mn(0.3)Co(0.2)O2 by Retarding Its Interfacial Reaction with an Electrolyte by Atomic-Layer-Deposited Al2O3

High-voltage (>4.3 V) operation of LiNi(x)Mn(y)Co(z)O2 (NMC; 0 ≤ x, y, z < 1) for high capacity has become a new challenge for next-generation lithium-ion batteries because of the rapid capacity degradation over cycling. In this work, we investigate the performance of LiNi(0.5)Mn(0.3)Co(0.2)O2 (NMC532) electrodes with and without an atomic-layer-deposited (ALD) Al2O3 layer for charging/discharging in the range from 3.0 to 4.5 V (high voltage). The results of the electrochemical measurements show that the cells with ALD Al2O3-coated NMC532 electrodes have much enhanced cycling stability. The mechanism was investigated by using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and electrochemical methods. We find that the ultrathin ALD Al2O3 film can reduce the interface resistance of lithium-ion diffusion and enhance the surface stability of NMC532 by retarding the reactions at NMC532/electrolyte interfaces for preventing the formation of a new microstructure rock-salt phase NiO around the NMC532 surfaces.

Can oriented-attachment be an efficient growth mechanism for the synthesis of 1D nanocrystals via atomic layer deposition?

One-dimensional (1D) nanocrystals, such as nanorods and nanowires, have received extensive attention in the nanomaterials field due to their large surface areas and 1D confined transport properties. Oriented attachment (OA) is now recognized as a major growth mechanism for efficiently synthesizing 1D nanocrystals. Recently, atomic layer deposition (ALD) has been modified to be a powerful vapor-phase technique with which to synthesize 1D OA nanorods/nanowires with high efficiency and quality by increasing the temperature and purging time. In this invited mini-review, we look into the advantages of OA and high-temperature ALD, and investigate the potential of employing the OA growth mechanism for the synthesis of 1D nanocrystals via modified ALD, aiming to provide guidance to researchers in the fields of both OA and ALD for efficient synthesis of 1D nanocrystals.

Doped Si nanoparticles with conformal carbon coating and cyclized-polyacrylonitrile network as high-capacity and high-rate lithium-ion battery anodes

Doped Si nanoparticles (SiNPs) with conformal carbon coating and cyclized-polyacrylonitrile (PAN) network displayed capacities of 3500 and 3000 mAh g(-1) at C/20 and C/10, respectively. At 1 C, the electrode preserves a specific discharge capacity of ∼1500 mAh g(-1) for at least 60 cycles without decay. Al2O3 atomic layer deposition (ALD) helps improve the initial Coulombic efficiency (CE) to 85%. The dual coating of conformal carbon and cyclized-PAN help alleviate volume change and facilitate charge transfer. Ultra-thin Al2O3 ALD layers help form a stable solid electrolyte interphase interface.

Mechanistic Insight into the Stability of HfO2 -Coated MoS2 Nanosheet Anodes for Sodium Ion Batteries

It is demonstrated for the first time that surface passivation of 2D nanosheets of MoS2 by an ultrathin and uniform layer of HfO2 can significantly improve the cyclic performance of sodium ion batteries. After 50 charge/discharge cycles, bare MoS2 and HfO2 coated MoS2 electrodes deliver the specific capacity of 435 and 636 mAh g(-1) , respectively, at current density of 100 mA g(-1) . These results imply that batteries using HfO2 coated MoS2 anodes retain 91% of the initial capacity; in contrast, bare MoS2 anodes retain only 63%. Also, HfO2 coated MoS2 anodes show one of the highest reported capacity values for MoS2 . Cyclic voltammetry and X-ray photoelectron spectroscopy results suggest that HfO2 does not take part in electrochemical reaction. The mechanism of capacity retention with HfO2 coating is explained by ex situ transmission electron microscope imaging and electrical impedance spectroscopy. It is illustrated that HfO2 acts as a passivation layer at the anode/electrolyte interface and prevents structural degradation during charge/discharge process. Moreover, the amorphous nature of HfO2 allows facile diffusion of Na ions. These results clearly show the potential of HfO2 coated MoS2 anodes, which performance is significantly higher than previous reports where bulk MoS2 or composites of MoS2 with carbonaceous materials are used.

Highly stable Na2/3 (Mn0.54 Ni0.13 Co0.13 )O2 cathode modified by atomic layer deposition for sodium-ion batteries

For the first time, atomic layer deposition (ALD) of Al2 O3 was adopted to enhance the cyclic stability of layered P2-type Na2/3 (Mn0.54 Ni0.13 Co0.13 )O2 (MNC) cathodes for use in sodium-ion batteries (SIBs). Discharge capacities of approximately 120, 123, 113, and 105 mA h g(-1) were obtained for the pristine electrode and electrodes coated with 2, 5, and 10 ALD cycles, respectively. All electrodes were cycled at the 1C discharge current rate for voltages between 2 and 4.5 V in 1 M NaClO4 electrolyte. Among the electrodes tested, the Al2 O3 coating from 2 ALD cycles (MNC-2) exhibited the best electrochemical stability and rate capability, whereas the electrode coated by 10 ALD cycles (MNC-10) displayed the highest columbic efficiency (CE), which exceeded 97 % after 100 cycles. The enhanced electrochemical stability observed for ALD-coated electrodes could be a result of the protection effects and high band-gap energy (Eg =9.00 eV) of the Al2 O3 coating layer. Additionally, the metal-oxide coating provides structural stability against mechanical stresses occurring during the cycling process. The capacity, cyclic stability, and rate performance achieved for the MNC electrode coated with 2 ALD cycles of Al2 O3 reveal the best results for SIBs. This study provides a promising route toward increasing the stability and CE of electrode materials for SIB application.

Interface Engineering through Atomic Layer Deposition towards Highly Improved Performance of Dye-Sensitized Solar Cells

A composite photoanode comprising ultralong ZnO nanobelts and TiO2 nanoparticles was prepared and its performance in dye-sensitized solar cells (DSSCs) was optimized and compared to the photoanode consisting of conventional TiO2 nanoparticles. The ultralong ZnO nanobelts were synthesized in high yield by a facile solution approach at 90°C followed by annealing at 500°C. The effect of the ratio of ZnO nanobelts to TiO2 nanoparticles on the light scattering, specific surface area, and interface recombination were investigated. An optimum amount of ZnO nanobelts enhanced the photon-conversion efficiency by 61.4% compared to that of the conventional TiO2 nanoparticles. To further reduce the recombination rate and increase the carrier lifetime, Atomic Layer Deposition (ALD) technique was utilized to coat a continuous TiO2 film surrounding the ZnO nanobelts and TiO2 nanoparticles, functioning as a barrier-free access of all electrons to conductive electrodes. This ALD treatment improved the interface contact within the whole photoanode system, finally leading to significant enhancement (137%) in the conversion efficiency of DSSCs.

Stabilizing Nanosized Si Anodes with the Synergetic Usage of Atomic Layer Deposition and Electrolyte Additives for Li-Ion Batteries

A substantial increase in charging capacity over long cycle periods was made possible by the formation of a flexible weblike network via the combination of Al2O3 atomic layer deposition (ALD) and the electrolyte additive vinylene carbonate (VC). Transmission electron microscopy shows that a weblike network forms after cycling when ALD and VC were used in combination that dramatically increases the cycle stability for the Si composite anode. The ALD-VC combination also showed reduced reactions with the lithium salt, forming a more stable solid electrolyte interface (SEI) absent of fluorinated silicon species, as evidenced by X-ray photoelectron spectroscopy. Although the bare Si composite anode showed only an improvement from a 56% to a 45% loss after 50 cycles, when VC was introduced, the ALD-coated Si anode showed an improvement from a 73% to a 11% capacity loss. Furthermore, the anode with the ALD coating and VC had a capacity of 630 mAh g(-1) after 200 cycles running at 200 mA g(-1), and the bare anode without VC showed a capacity of 400 mAh g(-1) after only 50 cycles. This approach can be extended to other Si systems, and the formation of this SEI is dependent on the thickness of the ALD that affects both capacity and stability.