Nanospace-Confinement Synthesis: Designing High-Energy Anode Materials toward Ultrastable Lithium-Ion Batteries

Confined Synthesis of Noble Metal Clusters Assisted by Liquid Film for Photocatalytic CO2 Reduction

The important concept of confined synthesis is considered a promising strategy for the design and synthesis of definable nanostructured materials with controllable compositions and specific morphology, such as highly loaded single-atom catalysts capable of providing abundant active sites for photocatalytic reactions. In recent years, researchers have been working on developing new confined reaction systems and searching for new confined spaces. Here, we present for the first time the concept of a bubble liquid film as a novel confined space. The liquid film has a typical sandwich structure consisting of a water layer, sandwiched between the upper and lower surfactant layers, with the thickness of the intermediate water layer at the micro- and nanometer scales, which can serve as a good confinement. Based on the above understanding and combined with the photodeposition method, we successfully confined synthesized Ag/TiO2, Au/TiO2, and Pd/TiO2 photocatalysts in liquid film. By HAADF-STEM, it can be seen that the noble metal morphologies are all nanoclusters of about 1 nm and are highly uniformly dispersed on the TiO2 surface. Compared with photodeposition in solution, we believe that the surfactant molecular layer restricts a limited amount of precursor to the liquid film, avoiding the accumulation of noble metals and the formation of large particle size nanoparticles. The liquid film, meanwhile, restricts the migration path of noble metal precursors, allowing for thorough in situ photodeposition and enables the complete and uniform dispersion of noble metal precursors, greatly reducing the photodeposition time. The uniform loading of the three noble metals proved the universality of the method, and the catalysts showed high activity for photocatalytic CO2 reduction. The rates of reduction of CO2 to CO over the Ag/TiO2 photocatalytic reached 230 μmol g-1 h-1.This study provides a new idea for the expansion of the confined reaction system and a reference for the study of liquid film as the confined space.

A Universal Cross-Synthetic Strategy for Sub-10 nm Metal-Based Composites with Excellent Ion Storage Kinetics

The sub-10 nm metal-based nanomaterials (SMNs) show great potential for the electrochemical energy storage field. However, their ion storage capacity and stability suffer from severe agglomeration and interface problems. Herein, a universal strategy is reported to synthesize a wide range of SMNs (e.g., metal, nitride, oxide, and sulfides) embedded in free-standing carbon foam (SMN/FC-F) composite electrodes by crossing the interfacial confinement of NaCl self-assembly with the thermal-mechanical coupling of powder metallurgy. The pressure-enhanced NaCl self-assembly interfacial confinement is greatly beneficial to preventing SMN agglomeration and promoting SMNs embedded in FC-F which originate from the welding of carbon nanosheets. They are confirmed via a series of advanced characterizations including X-ray photoelectron spectroscopy, and spherical aberration-corrected scanning transmission electron microscopy, with theoretical computations. Benefiting from the unique structure, SMNs/FC-F delivers ultrafast and stable ion-storage kinetics. As a proof-of-concept demonstration, the MoS2 /FC-F shows excellent ion storage kinetics and superior long-term cycling performance for ion storage (e.g., Na3 V2 (PO4 )2 O2 F/C//MoS2 /FC-F sodium-ion batteries exhibit a high reversible capacity of 185 mAh g-1 at 0.5 A g-1 with a decay rate of 0.05% per cycle.). This work provides a new opportunity to design and fabricate promising SMN-based free-standing working electrodes for electrochemical energy storage and conversion applications.

Perspective: New directions in dynamical density functional theory

Classical dynamical density functional theory (DDFT) has become one of the central modeling approaches in nonequilibrium soft matter physics. Recent years have seen the emergence of novel and interesting fields of application for DDFT. In particular, there has been a remarkable growth in the amount of work related to chemistry. Moreover, DDFT has stimulated research on other theories such as phase field crystal models and power functional theory. In this perspective, we summarize the latest developments in the field of DDFT and discuss a variety of possible directions for future research.

Solid-State Reaction Synthesis of Nanoscale Materials: Strategies and Applications

Nanomaterials (NMs) with unique structures and compositions can give rise to exotic physicochemical properties and applications. Despite the advancement in solution-based methods, scalable access to a wide range of crystal phases and intricate compositions is still challenging. Solid-state reaction (SSR) syntheses have high potential owing to their flexibility toward multielemental phases under feasibly high temperatures and solvent-free conditions as well as their scalability and simplicity. Controlling the nanoscale features through SSRs demands a strategic nanospace-confinement approach due to the risk of heat-induced reshaping and sintering. Here, we describe advanced SSR strategies for NM synthesis, focusing on mechanistic insights, novel nanoscale phenomena, and underlying principles using a series of examples under different categories. After introducing the history of classical SSRs, key theories, and definitions central to the topic, we categorize various modern SSR strategies based on the surrounding solid-state media used for nanostructure growth, conversion, and migration under nanospace or dimensional confinement. This comprehensive review will advance the quest for new materials design, synthesis, and applications.

Single-Atom Tailored Hierarchical Transition Metal Oxide Nanocages for Efficient Lithium Storage

Mitigating the mechanical degradation and enhancing the ionic/electronic conductivity are critical but challengeable issues toward improving electrochemical performance of conversion-type anodes in rechargeable batteries. Herein, these challenges are addressed by constructing interconnected 3D hierarchically porous structure synergistic with Nb single atom modulation within a Co₃ O₄ nanocage (3DH-Co₃ O₄ @Nb). Such a hierarchical-structure nanocage affords several fantastic merits such as rapid ion migration and enough inner space for alleviating volume variation induced by intragrain stress and optimized stability of the solid-electrolyte interface. Particularly, experimental studies in combination with theoretical analysis verify that the introduction of Nb into the Co₃ O₄ lattice not only improves the electron conductivity, but also accelerates the surface/near-surface reactions defined as pesudocapacitance behavior. Dynamic behavior reveals that the ensemble design shows huge potential for fast and large lithium storage. These features endow 3DH-Co₃ O₄ @Nb with remarkable battery performance, delivering ≈740 mA h g^-1 after ultra-long cycling of 1000 times under a high current density of 5 A g^-1 . Importantly, the assembled 3DH-Co₃ O₄ @Nb//LiCoO₂ pouch cell also presents a long-lived cycle performance with only ≈0.059% capacity decay per cycle, inspiring the design of electrode materials from both the nanostructure and atomic level toward practical applications.

The cobalt atom protection layers in-situ anchored titanium carbide with controllable interlayer spacing towards stable and fast lithium ions storage

MXenes are the typical ions insertion-type two-dimensional (2D) nanomaterials, have attracted extensive attention in the Li⁺ storage field. However, the self-stacking of layered structure and the consumption of electrolyte during the process of charge/discharge will limit the Li⁺ diffusion dynamics, rate capability and capacity of MXenes. Herein, a Co atom protection layers with electrochemical nonreactivity were anchored on/in the surface/interlayer of titanium carbide (Ti₃C₂) by in-situ thermal anchoring (x-Co/m-Ti₃C₂, x  = 45, 65 and 85), which can not only avoid the self-stacking and expand the interlayer spacing of Ti₃C₂ but also reduce the consumption of Li⁺ and electrolyte by forming the thin solid electrolyte interphase (SEI) film. The interlayer spacing of Ti₃C₂ can be expanded from 0.98 to 1.21, 1.36 and 1.33 nm when the anchoring temperatures are 45, 65 and 85 °C due to the pillaring effects of Co atom layers, in where the 65-Co/m-Ti₃C₂ can achieve the best specific capacity and rate capability attributed to its superior diffusion coefficient of 8.8 × 10^-7 cm² s^-1 in Li⁺ storage process. Furthermore, the 45, 65 and 85-Co/m-Ti₃C₂ exhibit lower SEI resistances (R_SEI) as 1.45 ± 0.01, 1.26 ± 0.01 and 1.83 ± 0.01 Ω compared with the R_SEI of Ti₃C₂ (5.18 ± 0.01 Ω), suggesting the x-Co/m-Ti₃C₂ demonstrates a thin SEI film due to the protection of Co atom layers. The findings propose a Co atom protection layers with electrochemical nonreactivity, not only giving an approach to expand the interlayer spacing, but also providing a protection strategy for 2D nanomaterials.

Rationally integrated nickel sulfides for lithium storage: S/N co-doped carbon encapsulated NiS/Cu2S with greatly enhanced kinetic property and structural stability

Nickel sulfides are promising anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacities but suffer from the sluggish kinetic process and poor structural stability. Herein, we develop...

A free-standing VN/MXene composite anode for high-performance Li-ion hybrid capacitors

The Li-ion hybrid capacitor (LIHC) is considered as a promising candidate for electrochemical energy storage owing to the high energy and power density. However, the sluggish anodic reaction kinetics and high reaction voltage greatly hinder the overall performance of LIHCs. Herein, a free-standing VN/MXene composite anode with high specific capacity and low reaction voltage was prepared by a simple vacuum filtration method. The obtained VN/MXene composite anode shows a high discharge specific capacity of 501.7 mA h g⁻¹ at 0.1 A g⁻¹ and excellent rate capability (191.8 mA h g⁻¹ at 5 A g⁻¹), as well as much extended cycling stability (1500 cycles at 2 A g⁻¹). When combined with an egg white-derived activated carbon (E-AC) cathode, the assembled LIHC delivers a high specific capacity of 59.1 F g⁻¹ and a high energy density of 129.3 W h kg⁻¹ with a power density of 449.7 W kg⁻¹. Even at a high current density of 5 A g⁻¹, the LIHC still maintains an exciting energy density of 42.81 W h kg⁻¹ at 11 249 W kg⁻¹. Meanwhile, the cycling life can be extended to 5000 cycles with a high capacity retention of 98% at 1 A g⁻¹. We believe that this work opens up new possibilities for developing advanced free-standing MXene-based electrodes for Li-ion storage.

The Li-ion hybrid capacitor (LIHC) is considered as a promising candidate for electrochemical energy storage owing to the high energy and power density.

Carbon nanotubes coupled with layered graphite to support SnTe nanodots as high-rate and ultra-stable lithium-ion battery anodes

SnTe exhibits a layered crystal structure, which enables fast Li-ion diffusion and easy storage, and is considered to be a promising candidate for an advanced anode material. However, its applications are hindered by the large volume variation caused by intercalation/deintercalation during the electrochemical reaction processes. Herein, topological insulator SnTe and carbon nanotubes (CNTs) supported on a graphite (G) carbon framework (SnTe-CNT-G) were prepared as a new, active and robust anode material for high-rate lithium-ion batteries by a scalable ball-milling method. Remarkably, the SnTe-CNT-G composite used as a lithium-ion battery anode offered an excellent reversible capacity of 840 mA h g-1 at 200 mA g-1 after 100 cycles and high initial coulombic efficiencies of 76.0%, and achieved a long-term cycling stability of 669 mA h g-1 at 2 A g-1 after 1400 cycles. The superior electrochemical performance of SnTe-CNT-G is attributed to the stable design of its electrode structure and interesting topological transition of SnTe, combined with multistep conversion and alloying processes. Furthermore, in situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy were employed to study the reaction mechanism. The results presented here provide new insights to design and reveal the reaction mechanisms of transition metal telluride materials in various energy-storage materials.