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

"Win-Win" Modification of LiCoO2 Enables Stable and Long-Life Cycling of Sulfide-Based All Solid-State Batteries

Interfacial side reactions and space charge layers between the oxide cathode material and the sulfide solid-state electrolytes (SSEs), along with the structural degradation of the active material, significantly compromise the electrochemical performance of all-solid-state batteries (ASSLBs). Surface coating and bulk doping of the cathodes are considered the most effective approaches to mitigate the interface issues between the cathode and SSEs and enhance the structural integrity of composite cathodes. Here, a one-step low-cost means is ingeniously designed to modify LiCoO2 (LCO) with heterogeneous Li2 TiO3 /Li(TiMg)1/2 O2 surface coating and bulk gradient Mg doping. When applied in Li10 GeP2 S12 -based ASSLBs, the Li2 TiO3 and Li(TiMg)1/2 O2 coating layers effectively suppress interfacial side reactions and weaken space charge layer effect. Furthermore, gradient Mg doping stabilizes the bulk structure to mitigate the formation of spinel-like phases during local overcharging caused by solid-solid contact. The modified LCO cathodes exhibit excellent cycle performance with a capacity retention of 80 % after 870 cycles. This dual-functional strategy provides the possibility for large-scale commercial implementation of cathodes modification in sulfide based ASSLBs in the future.

Recent progress in structural modification of polymer gel electrolytes for use in solid-state zinc-ion batteries

Zinc-ion batteries are one of the promising energy storage devices, which have the advantages of environmental friendliness, high safety and low price and are expected to be used in large-scale battery application fields. However, four prominent water-induced adverse reactions, including zinc dendrite formation, zinc corrosion, passivation and the hydrogen evolution reaction in aqueous systems, seriously shorten the cycling life of zinc-ion batteries and greatly hinder their development. Based on this, polymer gel electrolytes have been developed to alleviate these issues due to their unique network structure, which can reduce water activity and suppress water-induced side reactions. Based on the challenges of polymer gel electrolytes, this review systematically summarizes the latest research progress in the use of additives in them and explores new perspectives in response to the existing problems with polymer electrolytes. In order to expand the performance of polymer gel electrolytes in zinc-ion batteries, a range of different types of additives are added via physical/chemical crosslinking, such as organic or inorganic substances, natural plants, etc. In addition, different types of additives and polymerization crosslinking from different angles essentially improve the ionic conductivity of the gel electrolyte, inhibit the growth of zinc dendrites, and reduce hydrogen evolution and oxygen-absorbed corrosion. After these modifications of polymer gel electrolytes, a more stable and superior electrochemical performance of zinc-ion batteries can be obtained, which provides some strategies for solid-state zinc-ion batteries.

Antiperovskite Electrolytes for Solid-State Batteries

Solid-state batteries have fascinated the research community over the past decade, largely due to their improved safety properties and potential for high-energy density. Searching for fast ion conductors with sufficient electrochemical and chemical stabilities is at the heart of solid-state battery research and applications. Recently, significant progress has been made in solid-state electrolyte development. Sulfide-, oxide-, and halide-based electrolytes have been able to achieve high ionic conductivities of more than 10^-3 S/cm at room temperature, which are comparable to liquid-based electrolytes. However, their stability toward Li metal anodes poses significant challenges for these electrolytes. The existence of non-Li cations that can be reduced by Li metal in these electrolytes hinders the application of Li anode and therefore poses an obstacle toward achieving high-energy density. The finding of antiperovskites as ionic conductors in recent years has demonstrated a new and exciting solution. These materials, mainly constructed from Li (or Na), O, and Cl (or Br), are lightweight and electrochemically stable toward metallic Li and possess promising ionic conductivity. Because of the structural flexibility and tunability, antiperovskite electrolytes are excellent candidates for solid-state battery applications, and researchers are still exploring the relationship between their structure and ion diffusion behavior. Herein, the recent progress of antiperovskites for solid-state batteries is reviewed, and the strategies to tune the ionic conductivity by structural manipulation are summarized. Major challenges and future directions are discussed to facilitate the development of antiperovskite-based solid-state batteries.

Nanoscale Li, Na, and K Ion-Conducting Polyphosphazenes by Atomic Layer Deposition

Solid state batteries (SSBs), and corresponding solid-state electrolytes (SSEs), have been proposed to address both dimensional restrictions and safety concerns associated with liquid electrolyte batteries. Atomic layer deposition (ALD) is...

Atomic and Molecular Layer Deposition of Alkali Metal Based Thin Films

Atomic layer deposition (ALD) is the fastest growing thin-film technology in microelectronics, but it is also recognized as a promising fabrication strategy for various alkali-metal-based thin films in emerging energy technologies, the spearhead application being the Li-ion battery. Since the pioneering work in 2009 for Li-containing thin films, the field has been rapidly growing and also widened from lithium to other alkali metals. Moreover, alkali-metal-based metal-organic thin films have been successfully grown by combining molecular layer deposition (MLD) cycles of the organic molecules with the ALD cycles of the alkali metal precursor. The current literature describes already around 100 ALD and ALD/MLD processes for alkali-metal-bearing materials. Interestingly, some of these materials cannot even be made by any other synthesis route. In this review, our intention is to present the current state of research in the field by (i) summarizing the ALD and ALD/MLD processes so far developed for the different alkali metals, (ii) highlighting the most intriguing thin-film materials obtained thereof, and (iii) addressing both the advantages and limitations of ALD and MLD in the application space of these materials. Finally, (iv) a brief outlook for the future perspectives and challenges of the field is given.

Recent progress and future prospects of atomic layer deposition to prepare/modify solid-state electrolytes and interfaces between electrodes for next-generation lithium batteries

Lithium ion batteries (LIBs) are encouraging electrochemical devices with remarkable properties including a high energy/power density, fast charging capability, and low self-discharge rate. Further increase in energy density as well as safe usage is needed for next-generation LIBs in electric transportation vehicles. Solid-state electrolytes (SSEs) are very promising for high-performance LIBs since they enable improved safety along with increased energy density compared to flammable liquid organic electrolytes. However, utilizing SSEs with a Li metal anode is very challenging due to the possibility of undesired side reactions and the formation of an unstable solid-electrolyte interphase. Therefore, it is critical to enhance the stability of SSEs against the Li anode. One feasible approach is to form a thin and conductive interlayer between the Li anode and solid-state electrolyte. Atomic layer deposition (ALD) is a unique technique for conformal coating of complex 3D structures with finely controlled film thickness (at the atomic scale). ALD coating on the surface of SSEs can be adopted for engineering solid-electrolyte interfaces with desired attributes and improved stability. In this review paper, we have discussed recent progress in implementing the ALD technique for depositing thin layers on various SSE configurations including lithium phosphorus oxynitride (LiPON), garnets, oxides, perovskites, sulphides, Li₃BO₃-Li₂CO₃ (LBCO), and sodium super ionic conductors (NASICON). We have also highlighted the major areas for future research and development in the field. We believe that this review will be very helpful for directing future research on implementing ALD for synthesizing stable and high-performance SSEs with an engineered solid-electrolyte interface for next-generation electrochemical devices (e.g., Li-ion batteries, supercapacitors, and flow batteries).

Atomic Layer Deposition of Ni-Co-O Thin-Film Electrodes for Solid-State LIBs and the Influence of Chemical Composition on Overcapacity

Nanostructured metal oxides (MOs) demonstrate good electrochemical properties and are regarded as promising anode materials for high-performance lithium-ion batteries (LIBs). The capacity of nickel-cobalt oxides-based materials is among the highest for binary transition metals oxide (TMOs). In the present paper, we report the investigation of Ni-Co-O (NCO) thin films obtained by atomic layer deposition (ALD) using nickel and cobalt metallocenes in a combination with oxygen plasma. The formation of NCO films with different ratios of Ni and Co was provided by ALD cycles leading to the formation of nickel oxide (a) and cobalt oxide (b) in one supercycle (linear combination of a and b cycles). The film thickness was set by the number of supercycles. The synthesized films had a uniform chemical composition over the depth with an admixture of metallic nickel and carbon up to 4 at.%. All samples were characterized by a single NixCo1-xO phase with a cubic face-centered lattice and a uniform density. The surface of the NCO films was uniform, with rare inclusions of nanoparticles 15–30 nm in diameter. The growth rates of all films on steel were higher than those on silicon substrates, and this difference increased with increasing cobalt concentration in the films. In this paper, we propose a method for processing cyclic voltammetry curves for revealing the influence of individual components (nickel oxide, cobalt oxide and solid electrolyte interface—SEI) on the electrochemical capacity. The initial capacity of NCO films was augmented with an increase of nickel oxide content.

Atomic/molecular layer deposition for energy storage and conversion

Energy storage and conversion systems, including batteries, supercapacitors, fuel cells, solar cells, and photoelectrochemical water splitting, have played vital roles in the reduction of fossil fuel usage, addressing environmental issues and the development of electric vehicles. The fabrication and surface/interface engineering of electrode materials with refined structures are indispensable for achieving optimal performances for the different energy-related devices. Atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques, the gas-phase thin film deposition processes with self-limiting and saturated surface reactions, have emerged as powerful techniques for surface and interface engineering in energy-related devices due to their exceptional capability of precise thickness control, excellent uniformity and conformity, tunable composition and relatively low deposition temperature. In the past few decades, ALD and MLD have been intensively studied for energy storage and conversion applications with remarkable progress. In this review, we give a comprehensive summary of the development and achievements of ALD and MLD and their applications for energy storage and conversion, including batteries, supercapacitors, fuel cells, solar cells, and photoelectrochemical water splitting. Moreover, the fundamental understanding of the mechanisms involved in different devices will be deeply reviewed. Furthermore, the large-scale potential of ALD and MLD techniques is discussed and predicted. Finally, we will provide insightful perspectives on future directions for new material design by ALD and MLD and untapped opportunities in energy storage and conversion.

Synthesis and Crystallization of Atomic Layer Deposition β-Eucryptite LiAlSiO4 Thin-Film Solid Electrolytes

Atomic layer deposition (ALD) was used to control the stoichiometry of thin lithium aluminosilicate films, thereby enabling crystallization into the ion-conducting β-eucryptite LiAlSiO₄ phase. The rapid thermal annealed ALD film developed a well-defined epitaxial relationship to the silicon substrate: β-LiAlSiO₄ (12̅10)||Si (100) and β-LiAlSiO₄ (101̅0)||Si (001). The extrapolated room temperature ionic conductivity was found to be 1.2 × 10^-7 S/cm in the [12̅10] direction. Because of the unique 1-D channel along the c axis of β-LiAlSiO₄, the epitaxial thin film has the potential to facilitate ionic transport if oriented with the c axis normal to the electrode surface, making it a promising electrolyte material for three-dimensional lithium-ion microbatteries.

Atomic Layer Deposition of Lithium–Nickel–Silicon Oxide Cathode Material for Thin-Film Lithium-Ion Batteries

Lithium nickelate (LiNiO2) and materials based on it are attractive positive electrode materials for lithium-ion batteries, owing to their large capacity. In this paper, the results of atomic layer deposition (ALD) of lithium–nickel–silicon oxide thin films using lithium hexamethyldisilazide (LiHMDS) and bis(cyclopentadienyl) nickel (II) (NiCp2) as precursors and remote oxygen plasma as a counter-reagent are reported. Two approaches were studied: ALD using supercycles and ALD of the multilayered structure of lithium oxide, lithium nickel oxide, and nickel oxides followed by annealing. The prepared films were studied by scanning electron microscopy, spectral ellipsometry, X-ray diffraction, X-ray reflectivity, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected-area electron diffraction. The pulse ratio of LiHMDS/Ni(Cp)2 precursors in one supercycle ranged from 1/1 to 1/10. Silicon was observed in the deposited films, and after annealing, crystalline Li2SiO3 and Li2Si2O5 were formed at 800 °C. Annealing of the multilayered sample caused the partial formation of LiNiO2. The obtained cathode materials possessed electrochemical activity comparable with the results for other thin-film cathodes.

Rational design of spontaneous reactions for protecting porous lithium electrodes in lithium-sulfur batteries

A rechargeable lithium anode requires a porous structure for a high capacity, and a stable electrode/electrolyte interface against dendrite formation and polysulfide crossover when used in a lithium-sulfur battery. Here, we design two simple steps of spontaneous reactions for protecting porous lithium electrodes. First, a reaction between molten lithium and sulfur-impregnated carbon nanofiber forms a fibrous network with a lithium shell and a carbon core. Second, we coat the surface of this porous lithium electrode with a composite of lithium bismuth alloys and lithium fluoride through another spontaneous reaction between lithium and bismuth trifluoride, solvated with phosphorous pentasulfide, which also polymerizes with lithium sulfide residual in the electrode to form a solid electrolyte layer. This protected porous lithium electrode enables stable operation of a lithium-sulfur battery with a sulfur loading of 10.2 mg cm-2 at 6.0 mA cm-2 for 200 cycles.

Diatomite derived hierarchical hybrid anode for high performance all-solid-state lithium metal batteries

Lithium metal based anode with hierarchical structure to enable high rate capability, volume change accommodation, and dendritic suppression is highly desirable for all-solid-state lithium metal battery. However, the fabrication of hierarchical lithium metal based anode is challenging due to the volatility of lithium. Here, we report that natural diatomite can act as an excellent template for constructing hierarchical silicon-lithium based hybrid anode for high performance all-solid-state lithium metal battery. This hybrid anode exhibits stable lithium stripping/plating performance over 1000 h with average overpotential lower than 100 mV without any short circuit. Moreover, all-solid-state full cell using this lithium metal composite anode to couple with lithium iron phosphate cathode shows excellent cycling stability (0.04% capacity decay rate for 500 cycles at 0.5C) and high rate capability (65 mAh g⁻¹ at 5C). The present natural diatomite derived hybrid anode could further promote the fabrication of high performance all-solid-state lithium batteries from sustainable natural resources.

Lithium metal is the anode of choice for the next-generation high energy density batteries. To address the key technological challenges, the authors report a hybrid Li anode design with hierarchical pores structure derived from natural diatomite and improved electrochemical performance in all-solid-state lithium batteries.

Lithium-Ion Intercalation into Graphite in SO2-Based Inorganic Electrolyte toward High-Rate-Capable and Safe Lithium-Ion Batteries

Herein, we have identified that lithium ions in an SO₂-based inorganic electrolyte reversibly intercalate and deintercalate into/out of graphite electrode using ex situ X-ray diffraction and various electrochemical methods. X-ray photoelectron spectroscopy shows that the solid electrolyte interphase on the graphite electrode is mainly composed of inorganic compounds, such as LiCl and lithium sulfur-oxy compounds. Graphite electrode in SO₂-based inorganic electrolyte has stable capacity retention up to 100 cycles and outstanding rate capability performance. This can be attributed to low interfacial impedance and high ionic conductivity of SO₂-based inorganic electrolyte, which are superior to those of conventional organic electrolytes. Considering the remarkable rate capability and intrinsically nonflammable properties of the electrolyte, use of graphite and an SO₂ electrolyte will likely facilitate the development of advanced lithium-ion batteries.

Metal Fluorides as Lithium-Ion Battery Materials: An Atomic Layer Deposition Perspective

Lithium-ion batteries are the enabling technology for a variety of modern day devices, including cell phones, laptops and electric vehicles. To answer the energy and voltage demands of future applications, further materials engineering of the battery components is necessary. To that end, metal fluorides could provide interesting new conversion cathode and solid electrolyte materials for future batteries. To be applicable in thin film batteries, metal fluorides should be deposited with a method providing a high level of control over uniformity and conformality on various substrate materials and geometries. Atomic layer deposition (ALD), a method widely used in microelectronics, offers unrivalled film uniformity and conformality, in conjunction with strict control of film composition. In this review, the basics of lithium-ion batteries are shortly introduced, followed by a discussion of metal fluorides as potential lithium-ion battery materials. The basics of ALD are then covered, followed by a review of some conventional lithium-ion battery materials that have been deposited by ALD. Finally, metal fluoride ALD processes reported in the literature are comprehensively reviewed. It is clear that more research on the ALD of fluorides is needed, especially transition metal fluorides, to expand the number of potential battery materials available.

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.