In situ synthesis of a silicon flake/nitrogen-doped graphene-like carbon composite from organoclay for high-performance lithium-ion battery anodes

Mechanochemical reduction of clay minerals to porous silicon nanoflakes for high-performance lithium-ion battery anodes

Hierarchically porous silicon nanoflakes were synthesized from natural talc via a mechanochemical reduction method, which showed great potential in the scalable production of silicon nanoflakes due to the abundant precursor and facile strategy. The unique layered structure and chemical composition of talc enabled the formation of two-dimensional nanostructured silicon without any additional templates. As lithium-ion battery anodes, the silicon nanoflakes showed excellent electrochemical properties.

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.

A Review on Recent Advances for Boosting Initial Coulombic Efficiency of Silicon Anodic Lithium Ion batteries

Rechargeable silicon anode lithium ion batteries (SLIBs) have attracted tremendous attention because of their merits, including a high theoretical capacity, low working potential, and abundant natural sources. The past decade has witnessed significant developments in terms of extending the lifespan and maintaining high capacities of SLIBs. However, the detrimental issue of low initial Coulombic efficiency (ICE) toward SLIBs is causing more and more attention in recent years because ICE value is a core index in full battery design that profoundly determines the utilization of active materials and the weight of an assembled battery. Herein, a comprehensive review is presented of recent advances in solutions for improving ICE of SLIBs. From design perspectives, the strategies for boosting ICE of silicon anodes are systematically categorized into several aspects covering structure regulation, prelithiation, interfacial design, binder design, and electrolyte additives. The merits and challenges of various approaches are highlighted and discussed in detail, which provides valuable insights into the rational design and development of state-of-the-art techniques to deal with the deteriorative issue of low ICE of SLIBs. Furthermore, conclusions and future promising research prospects for lifting ICE of SLIBs are proposed at the end of the review.

Lignin Derived Porous Carbons: Synthesis Methods and Supercapacitor Applications

Lignin, one of the renewable constituents in natural plant biomasses, holds great potential as a sustainable source of functional carbon materials. Tremendous research efforts have been made on lignin-derived carbon electrodes for rechargeable batteries. However, lignin is considered as one of the most promising carbon precursors for the development of high-performance, low-cost porous carbon electrode materials for supercapacitor applications. Yet, these efforts have not been reviewed in detail in the current literature. This review, therefore, offers a basis for the utilization of lignin as a pivotal precursor for the synthesis of porous carbons for use in supercapacitor electrode applications. Lignin chemistry, the synthesis process of lignin-derived porous carbons, and future directions for developing better porous carbon electrode materials from lignin are systematically reviewed. Technological hurdles and approaches that should be prioritized in future research are presented.

Natural Clay-Based Materials for Energy Storage and Conversion Applications

Among various energy storage and conversion materials, functionalized natural clays display significant potentials as electrodes, electrolytes, separators, and nanofillers in energy storage and conversion devices. Natural clays have porous structures, tunable specific surface areas, remarkable thermal and mechanical stabilities, abundant reserves, and cost-effectiveness. In addition, natural clays deliver the advantages of high ionic conductivity and hydrophilicity, which are beneficial properties for solid-state electrolytes. This review article provides an overview toward the recent advancements in natural clay-based energy materials. First, it comprehensively summarizes the structure, classification, and chemical modification methods of natural clays to make them suitable in energy storage and conversion devices. Then, the particular attention is focused on the application of clays in the fields of lithium-ion batteries, lithium-sulfur batteries, zinc-ion batteries, chloride-ion batteries, supercapacitors, solar cells, and fuel cells. Finally, the possible future research directions are provided for natural clays as energy materials. This review aims at facilitating the rapid developments of natural clay-based energy materials through a fruitful discussion from inorganic and materials chemistry aspects, and also promotes the broad sphere of clay-based materials for other utilization, such as effluent treatment, heavy metal removal, and environmental remediation.

Organoclay-derived lamellar silicon carbide/carbon composite as an ideal support for Pt nanoparticles: facile synthesis and toluene oxidation performance

A lamellar SiC/C composite was synthesized from organoclay via pyrolysis followed by salt-assisted magnesiothermic reduction. The in situ-formed carbon sheet within the restricted interlayer space of clay served as the carbon source and nanotemplate for forming SiC/C. With a large specific surface area, hierarchical porosity, available anchoring sites, good hydrophobicity, and thermal stability, SiC/C proved to be a promising support for Pt. The resulting Pt loaded SiC/C exhibited an excellent toluene oxidation performance.

Solvent-free functionalisation of graphene oxide with amide and amine groups at room temperature

A new solvent free protocol is presented to introduce amide and amine functionalities (N-aliphatic groups) onto graphene oxide in an energy efficient manner. Nitrogen contents of 3.6 wt% are obtained in only 5 minutes at room temperature by using ammonia gas as the nitrogen source for the ammonolysis of graphene oxide.

Synthesis of Porous Si/C Composite Nanosheets from Vermiculite with a Hierarchical Structure as a High-Performance Anode for Lithium-Ion Battery

Silicon nanosheets are fascinating anode materials for lithium-ion batteries because of their high specific capacities, structural stability, and fast kinetics in alloying/dealloying with Li. The nanosheets can be synthesized through chemical vapor deposition (CVD), topochemical reaction, and templating method. After coating with a carbon nanolayer, they exhibit enhanced electrochemical performance. However, it is challenging to synthesize ultrathin carbon-coated silicon nanosheets. In this work, porous silicon/carbon (pSi/C) composite nanosheets are synthesized by reducing the carbon-coated expanded vermiculite with metallic Al in the molten salts. The as-prepared pSi/C nanosheets retain the layered nanostructure of vermiculite, with a thickness of less than 50 nm. The carbon nanolayer serves as the diffusion barrier and mechanical support for the growth of mesoporous silicon nanosheets. The anode of pSi/C nanosheets achieves remarkable electrochemical performance, exhibiting a reversible capacity of 1837 mA h g^-1 at 4 A g^-1 and retaining 71.5% of the initial capacity after 500 cycles. The process can be extended to the synthesis of the pSi/C composite nanotube by using other carbon-coated silicate templates such as halloysite.