Three-dimensionally interconnected Si frameworks derived from natural halloysite clay: a high-capacity anode material for lithium-ion batteries

Nickel Oxide Decorated Halloysite Nanotubes as Sulfur Host Materials for Lithium-Sulfur Batteries

Lithium-sulfur batteries with high energy density still confront many challenges, such as polysulfide dissolution, the large volume change of sulfur, and fast capacity fading in long-term cycling. Herein, a naturally abundant clay material, halloysite, is introduced as a sulfur host material in the cathode of Li-S batteries. Nickel oxide nanoparticles are embedded into the halloysite nanotubes (NiO@Halloysite) by hydrothermal and calcination treatment to improve the affinity of halloysite nanotubes to polysulfides. The NiO@Halloysite composite loaded with sulfur (S/NiO@Halloysite) is employed as the cathode of Li-S batteries, which combines the physical confinements of tubular halloysite particles and good chemical adsorption ability of NiO. The S/NiO@Halloysite electrode exhibits a high discharge capacity of 1205.47 mAh g^-1 at 0.1 C. In addition, it demonstrates enhanced cycling stability, retaining ≈60% of initial capacity after 450 cycles at 0.5 C. The synthesized NiO@Halloysite can provide a promising prospect and valuable insight into applying natural clay materials in Li-S batteries.

Low Temperature Aluminothermic Reduction of Natural Sepiolite to High-Performance Si Nanofibers for Li-Ion Batteries

Nanostructure silicon is one of the most promising anode materials for the next-generation lithium-ion battery, but the complicated synthesis process and high cost limit its large-scale commercial application. Herein, a simple and low-cost method was proposed to prepare silicon nanofibers (SNF) using natural sepiolite as a template via a low-temperature aluminum reduction process. The low temperature of 260°C during the reduction process not only reduced the production cost but also avoided the destruction of the natural sepiolite structure caused by the high temperature above 600°C in the traditional magnesium thermal reduction process, leading to a more complete nanofiber structure in the final product. For the first time, the important role of Mg-O octahedral structure in the maintenance of nanofiber structure during the process of low-temperature aluminothermic reduction was verified by experiments. When used as an anode for lithium-ion batteries, SNF yield a high reversible capacity of 2005.4 mAh g−1 at 0.5 A g−1 after 50 cycles and 1017.6 mAh g−1 at 2 A g−1 after 200 cycles, remarkably outperforming commercial Si material. With a low-cost precursor and facile approach, this work provides a new strategy for the synthesis of a commercial high-capacity Si anode.

Silicon micron cages derived from a halloysite nanotube precursor and aluminum sacrificial template in molten AlCl3 as an anode for lithium-ion batteries

Porous nanostructures have been proposed a promising strategy to improve the electrochemical performance of Si materials as anodes of lithium-ion batteries (LIBs). However, expensive raw materials and the tedious preparation processes hinder their widespread adoption. In this work, silicon micron cages (SMCs) have been synthesized in molten AlCl₃ through using spherical aluminum particles as a sacrificial template, and the earth-abundant and low-cost natural halloysite clay as a precursor. The aluminum spheres (1–3 μm) not only act as a sacrificial template but also facilitate the formation of silicon branches, which connect together to form SMCs. As anodes for LIBs, the SMC electrode exhibits a high reversible capacity of 1977.5 mA h g⁻¹ after 50 cycles at a current density of 0.2 A g⁻¹, and 1035.1 mA h g⁻¹ after 300 cycles at a current density of 1.0 A g⁻¹. The improved electrochemical performance of SMCs could be ascribed to the micron cage structure, providing abundant buffering space and mesopores for Si expansion. This promising method is expected to offer a pathway towards the scalable application of Si-based anode materials in the next-generation LIB technology.

(1) Silicon micron cages (SMCs) was synthesized using natural halloysite as precursor. (2) The electrochemical performance of SMCs as anode materials of lithium-ion batteries can be improved for the micron cage structure.

Silicon nanosheets derived from silicate minerals: controllable synthesis and energy storage application

Silicon plays a crucial part in developing high-performance energy storage materials, owing to a high specific capacity compared to carbon. Moreover, nanoscale silicon is beneficial for reducing the inherent disadvantage of large volume change during repeated lithiation/de-lithiation, while artificial synthesis methods usually involve complex procedures and high costs. On account of the abundant natural reserve and low cost, the manipulation of silicate minerals is a simple and economical approach to prepare silicon nanosheets. In this regard, this mini review introduces different classes of silicate minerals and summarizes some typical molten salt-assisted reduction methods and other valuable methods applied to prepare silicon nanosheets for energy storage. Finally, the challenges and perspectives in this field are also proposed.

When Silicon Materials Meet Natural Sources: Opportunities and Challenges for Low-Cost Lithium Storage

The manipulation of progressive lithium-ion batteries (LIBs) with high energy density, low cost, and long-term cycling stability is of high priority to meet the growing demands for next-generation energy storage devices. Silicon (Si) has been receiving marvelous attention as a promising anode material for rechargeable LIBs, due to its high theoretical gravimetric capacity and low cost. Si is the second most abundant element in the earth crust in the form of silicates, so it is the most cost-effective element as an anode material in next-generation LIBs. In this review, different natural sources such as rice husk, sugar cane bagasse, bamboo, reed plant, sand, halloysite, and different waste sources such as waste of the solar power industry, fly ash, straw ash, and other industrial waste that can give rise to different nanostructured Si are systematically summarized. In addition, different synthesis methods of fabricating nanostructured Si are reviewed as well as including magnesiothermic reduction, etching methods, ball milling, and chemical vapor deposition. The advantages and disadvantages of these kind of synthesis methods are discussed as well. Furthermore, the opportunities and challenges of nano-Si are also discussed.

A carbon network strategy to synthesize silicon–carbon anodes toward regulated morphologies during molten salt reduction

In this work, a carbon network strategy was proposed to prepare Si/SiO_x/C anodes with regulated morphologies during molten salt reduction.

Functional biohybrid materials based on halloysite, sepiolite and cellulose nanofibers for health applications

Biohybrid materials were prepared by co-assembling the three following components: nanotubular halloysite, microfibrous sepiolite, and cellulose nanofibers dispersed in water, in order to exploit the most salient features of each individual component and to render homogeneous, flexible, yet strong films. Indeed, the incorporation of halloysite improves the mechanical performance of the resulting hybrid nanopapers and the assembly of the three components modifies the surface features concerning wetting properties compared to pristine materials, so that the main characteristics of the resulting materials become tunable with regard to certain properties. Owing to their hierarchical porosity together with their diverse surface characteristics, these hybrids can be used in diverse biomedical/pharmaceutical applications. Herein, for instance, loading with two model drugs, salicylic acid and ibuprofen, allows controlled and sustained release as deduced from antimicrobial assays, opening a versatile path for developing other related organic-inorganic materials of potential interest in diverse application fields.

A facile in situ synthesis of SiC&Si@CNT composite 3D frameworks as an anode material for lithium-ion batteries

SiC&Si@CNT composite 3D frameworks were successfully synthesized via an in situ reduction method of a C@SiO₂@CNT precursor. Owing to the extremely large amount of heat derived from magnesiothermic reduction, SiC particles of the SiC&Si@CNT composite were obtained by a reaction between Si and C. The amount of SiC could be adjusted by changing the poly-dopamine coating time. The SiC&Si@CNT composite is composed of reduced nano Si, fine SiC and CNTs. The as-prepared materials, particularly the SiC&Si@CNT-1 sample, show superior cycling performance and electrochemical characteristics as anode materials for lithium-ion batteries. In particular, the specific capacity of the SiC&Si@CNT-1 electrode reaches 1051.44 mA h g^-1 at 1 A g^-1 even after 880 cycles. Furthermore, the SiC&Si@CNT-1 electrode delivered ideal reversible capacities of 671.58 mA h g^-1 and 476.71 mA h g^-1 at high current densities of 4 A g^-1 and 8 A g^-1, respectively. The porous nanostructure of the SiC&Si@CNT composite 3D framework is beneficial for shortening the path of lithium-ion diffusion inside the electrode, alleviating the volume expansion and contraction during the cycling process. These results suggest that the SiC&Si@CNT composite 3D frameworks can be used as appropriate anode materials for lithium-ion batteries.