New Chemical Synthesis Strategy To Construct a Silicon/Carbon Nanotubes/Carbon-Integrated Composite with Outstanding Lithium Storage Capability

Abstract

The Si/C anode is one of the most promising candidate materials for the next-generation lithium-ion batteries (LIBs). Herein, a silicon/carbon nanotubes/carbon (Si/CNTs/C) composite is in situ synthesized by a one-step reaction of magnesium silicide, calcium carbonate, and ferrocene. Transmission electron microscopy reveals that the growth of CNTs is attributed to the catalysis of iron atoms derived from the decomposition of ferrocene. In comparison to a Si/C composite, the cycle stability of the Si/CNTs/C composite can obviously be improved as an anode for LIBs. The enhanced performance is mainly attributed to the following factors: (i) the perfect combination of Si nanoparticles and in situ grown CNTs achieves high mechanical integrity and good electrical contact; (ii) Si nanoparticles are entangled in the CNT cage, effectively reducing the volume expansion upon cycling; and (iii) in situ grown CNTs can improve the conductivity of composites and provide lithium ion transport channels. Moreover, the full cell constructed by a LiFePO4 cathode and Si/CNTs/C anode exhibits excellent cycling stability (137 mAh g–1 after 300 cycles at 0.5 C with a capacity retention rate of 91.2%). This work provides a new way for the synthesis of a Si/C anode for high-performance LIBs.

In Situ Copper Coating on Silicon Particles Enables Long Durable Anodes in Lithium-Ion Batteries

“…To overcome these obstacles, researchers have employed a few methodologies, − among which carbon coating is undoubtedly one of the most exemplary modification techniques. In fabricated Si/C nanocomposites, such as yolk–shell structures and core–shell structures, − carbon inclusion can not only improve electrical conductivity but also effectively relieve the mechanical stress caused by volume expansion to enhance the cycle stability. ,,− Although these endeavors have yielded promising results, their practical application is limited by the complex preparation process of carbon-coated nanomaterials and low yield. − Additionally, carbon in Si/C nanocomposites often has lower crystallinity, conductivity, and mechanical strength, hindering its ability to achieve durable cycling performance in LIBs. , …”

“…During the lithiation/delithiation processes, pure silicon materials exhibit volumetric expansion exceeding threefold, which in turn results in pulverization of the active constituents, continuous formation of solid–electrolyte interphase (SEI) film, detachment from copper foil current collectors, and ultimately leads to rapid capacity decay . Moreover, the inherent low conductivity of silicon hinders both electron and ion transport, further inhibiting its LIB performance. ,, …”

Constructing a Stable Integrated Silicon Electrode with Efficient Lithium Storage Performance through Multidimensional Structural Design

“…Carbon nanotubes (CNT) are also employed due to their high aspect ratio, excellent conductivity, and high mechanical strength. Encapsulation of CNT on the outer surface of Si through electrostatic self-assembly, , electrostatic adsorption, or in situ growth − methods achieves a comparable effect to that of an elastic carbon layer. Researchers have also adopted a skin-like covalent encapsulation strategy to create two-dimensional covalent Si/C materials, which exhibit high stability, capacity, and rate capability.…”

“…Furthermore, it establishes a two-dimensional highway, facilitating the rapid transport of lithium ions (Li + ). The one-dimensional Si nanowires (SiNW) serve as the primary component for lithium storage and offer advantages in mitigating stress changes compared to bulky Si particles. , CNT plays a crucial role in enhancing electrical conductivity within the integrated electrode. , Additionally, its binding to SiNW and G helps to restrict outward expansion during SiNW alloying. When combined with cPAN, a rigid, flexible protective layer (CNT/cPAN) is formed, which extends to every corner of the integrated electrode.…”

Carbon Nanofiber Cages and Interface Engineering Stabilizing Silicon-Based Anode for High-Performance Lithium-Ion Batteries

“…Numerous studies have reported that Si compounds with carbon materials can effectively address the above issues. Carbon nanofibers (CNFs) are an ideal composite component with a high surface area, high mechanical strength, and good electrical conductivity. − Si/CNF composites can not only alleviate the huge volume expansion of Si but also improve the electrical conductivity and structural stability of the composites. − For instance, Bai et al synthesized Si-CNF@C composites by electrostatic self-assembly and further carbonization. CNFs and amorphous carbon can effectively improve the dispersion and contact problems of Si nanoparticles.…”