Self-Climbed Amorphous Carbon Nanotubes Filled with Transition Metal Oxide Nanoparticles for Large Rate and Long Lifespan Anode Materials in Lithium Ion Batteries

van der Waals one-dimensional atomic crystal heterostructure derived from carbon nanotubes

One-dimensional (1D) van der Waals (vdWs) heterojunctions, due to the dimensional reduction leading to 1D quantum confinement effects and interface effects of the heterojunctions, typically exhibit discrete energy levels and strong electron interactions, resulting in unique conductive and optical behaviors. Carbon nanotube (CNT)-derived 1D atomic crystal vdWs heterojunctions represent a new class of 1D vdWs heterojunctions. They leverage the excellent chemical stability, nanoscale cavities, and adjustable diameters provided by CNTs as templates, ensuring controlled synthesis and precise structural tuning. The 1D radial pathways can alter the photonic-electronic propagation characteristics. At the same time, their unique metal-semiconductor-like electronic structure creates conditions for constructing various types of heterojunctions. The CNTs and their encapsulated 1D materials can lead to synergistic enhancement in the fields of electronics, magnetism, and optics. Currently, research is concentrated on understanding the synthesis mechanisms, integration characteristics, and host-guest interactions, and the exploration of novel 1D atomic crystal vdWs heterojunctions derived from CNTs. This review is focused on the latest progress made in 1D vdWs heterojunctions using CNTs as growth templates, emphasizing the construction methods, selection criteria, and the unique properties and applications arising from these complex interfacial electronic or phonon interactions. We also propose several future directions for the development of CNT-derived 1D atomic crystal vdWs heterojunctions. This review aims to enhance the understanding of their synthesis mechanisms and fundamental properties, broaden the range of available materials, and explore new and broader applications.

State-of-the-Art Review on Amorphous Carbon Nanotubes: Synthesis, Structure, and Application

Carbon nanotubes (CNTs) have rapidly received increasing attention and great interest as potential materials for energy storage and catalyst fields, which is due to their unique physicochemical and electrical properties. With continuous improvements in fabrication routes, CNTs have been modified with various types of materials, opening up new perspectives for research and state-of-the-art technologies. Amorphous CNTs (aCNTs) are carbon nanostructures that are distinctively different from their well-ordered counterparts, such as single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs, respectively), while the atoms in aCNTs are grouped in a disordered, crystalline/non-crystalline manner. Owing to their unique structure and properties, aCNTs are attractive for energy storage, catalysis, and aerospace applications. In this review, we provide an overview of the synthetic routes of aCNTs, which include chemical vapor deposition, catalytic pyrolysis, and arc discharge. Detailed morphologies of aCNTs and the systematic elucidation of tunable properties are also summarized. Finally, we discuss the future perspectives as well as associated challenges of aCNTs. With this review, we aim to encourage further research for the widespread use of aCNTs in industry.

Synthesis of Hybrid Carbon Materials Consisting of N-Doped Microporous Carbon and Amorphous Carbon Nanotubes

The N-doped hybrid carbon materials containing amorphous carbon nanotubes (ACNTs) were obtained by free growth of a polymer at 200 °C. The improvement of electrical conductivity was achieved by a final carbonization at 600–800 °C under the flow of nitrogen. The microstructure of ACNT/N-doped hybrids was characterized using a transmission electron microscope and X-ray diffusion. Furthermore, their elemental composition was measured using energy-dispersive X-ray spectroscopy and an elemental analyzer. The experimental results indicated that the ACNTs had a diameter in the range of 40–60 nm and the N-doped carbon background contained nitrogen atoms in most bonded pyrrolic-N and quaternary-N groups. The results revealed that the microstructure of the as-grown nanotubes, prepared by the proposed method, is mainly amorphous. This technique introduces the advantages of low cost and process simplicity, which may redeem some drawbacks of the methods commonly used in ACNT synthesis.

Plasma production of nanomaterials for energy storage: continuous gas-phase synthesis of metal oxide CNT materials via a microwave plasma

In this work we show for the first time that a continuous plasma process can synthesize materials from bulk industrial powders to produce hierarchical structures for energy storage applications. The plasma production process's unique advantages are that it is fast, inexpensive, and scalable due to its high energy density that enables low-cost precursors. The synthesized hierarchical material is comprised of iron oxide and aluminum oxide aggregate particles and carbon nanotubes grown in situ from the iron particles. New aerosol-based methods were used for the first time on a battery material to characterize aggregate and primary particle morphologies, while showing good agreement with observations from TEM measurements. As an anode for lithium ion batteries, a reversible capacity of 870 mA h g-1 based on metal oxide mass was observed and the material showed good recovery from high rate cycling. The high rate of material synthesis (∼10 s residence time) enables this plasma hierarchical material synthesis platform to be optimized as a means for energetic material production for the global energy storage material supply chain.

Electrospinning-based construction of porous Mn3O4/CNFs as anodes for high-performance lithium-ion batteries

Porous one-dimensional Mn₃O₄/CNFs composites are fabricated and used as anode materials for Li-ion batteries; they exhibit excellent electrochemical performance.

A Double-Buffering Strategy to Boost the Lithium Storage of Botryoid MnOx /C Anodes

Transition metal oxides (TMOs) are regarded as promising candidates for anodes of lithium ion batteries, but their applications have been severely hindered by poor material conductivity and lithiated volume expansion. As a potential solution, herein is presented a facile approach, by electrospinning a manganese-based metal organic framework (Mn-MOF), to fabricate yolk-shell MnO_x nanostructures within carbon nanofibers in a botryoid morphology. While the yolk-shell structure accomodates the lithiated volume expansion of MnO_x , the fiber confinement ensures the structural integrity during charge/discharge, achieving a so-called double-buffering for cyclic volume fluctuation. The formation mechanism of the yolk-shell structure is well elucidated through comprehensive instrumental characterizations and cogitative control experiments, following a combined Oswald ripening and Kirkendall process. Outstanding electrochemical performances are demonstrated with prolonged stability over 1000 cycles, boosted by the double-buffering design, as well as the "breathing" effect of lithiation/delithiation witnessed by ex situ imaging. Both the fabrication methodology and electrochemical understandings gained here for nanostructured MnO_x can also be extended to other TMOs toward their ultimate implementation in high-performance lithium ion batteries (LIBs).