Key Takeaways & Executive Findings
- •• A new top-down strategy for preparing microsize porous silicon is proposed, combined with a nitrogen-doped carbon coating from polyacrylonitrile (PAN). • Treatment at 400 °C yields a high nitrogen content of 11.35 at% in the PAN coating, enhancing ionic-electronic transport properties. • The optimized composite anode exhibits remarkable cycling stability, retaining a specific capacity of 857.6 mAh g−1 after 200 cycles at 4 A g−1. • The porous structure and carbon coating effectively mitigate volume expansion and structural degradation, demonstrating potential for high-capacity energy storage.
Abstract
Silicon anodes are promising for use in lithium-ion batteries. However, their practical application is severely limited by their large volume expansion leading to irreversible material fracture and electrical disconnects. This study proposes a new top-down strategy for preparing microsize porous silicon and introduces polyacrylonitrile (PAN) for a nitrogen-doped carbon coating, which is designed to maintain the internal pore volume and lower the expansion of the anode during lithiation and delithiation. We then explore the effect of temperature on the evolution of the structure of PAN and the electrochemical behavior of the composite electrode. After treatment at 400 °C, the PAN coating retains a high nitrogen content of 11.35 at%, confirming the presence of C―N and C―O bonds that improve the ionic-electronic transport properties. This treatment not only results in a more intact carbon layer structure, but also introduces carbon defects, and produces a material that has remarkable stable cycling even at high rates. When cycled at 4 A g−1, the anode had a specific capacity of 857.6 mAh g−1 even after 200 cycles, demonstrating great potential for high-capacity energy storage applications.
1. Introduction
The energy demand growing parallel to the demand for new-generation electronic devices and energy vehicles has made lithium-ion batteries (LIBs) ubiquitous in daily life and industrial production, due to their higher energy density[1-3]. Silicon (Si) has attracted significant research attention because of its high theoretical capacity (～3 579 mAh g–1 for Li15Si4)[4-6]. However, the commercialization of silicon-based anode is still hampered by some challenges[7], such as the extreme volume change (～300%) and continuous growth of the solid electrolyte interphase (SEI) layer. These issues result in structural damage, electrical contact failure, and sluggish kinetics, eventually leading to rapid capacity degradation[8-10].
Currently, the typical solution mainly involves the design of nanoscale materials, including nanoparticles[11-13], nanowires[14-16] and nanotubes[17,18]. Nevertheless, the high cost, complex process of preparation, and low tap density of nano-silicon hinder their practical application[19]. Especially, the low tap density adversely affects the volume-specific capacity of the electrodes[20]. Therefore, some researchers shifted focus to micro-sized silicon (M-Si) anodes as a cost-effective and feasible alternative to nano silicon. However, these micro-sized silicon anodes also encounter their own set of challenges. Particularly, the larger size of M-Si makes the transport path of lithium ions longer, and the local stress concentration in the process of lithiation and delithiation is more obvious, which result in more serious fracture and pulverization[21], impeding their ability to fully utilize the high capacity.
Several approaches have been developed to address those challenges in recent years. The top-down synthesis of porous silicon using micro-silicon has proven to be an effective strategy[22-24]. This technique creates a 3D porous structure with sufficient internal voids to alleviate the volume changes of the silicon anode, thereby mitigating structural pulverization during cycling[25,26]. Li et al.[27] presented a nitrogen-doped carbon dual-bonded silicon ...
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TIAN Zhen-yu, WANG Ya-fei, QIN Xin, Shaislamov Ulugbek, Hojamberdiev Mirabbos, ZHENG Tong-hui, DONG Shuo, ZHANG Xing-hao, KONG De-bin, ZHI Lin-jie (2025). Porous silicon/carbon composites as anodes for high-performance lithium-ion batteries. SinoTechIntel Verified Research. https://doi.org/10.1016/S1872-5805(NCM2024-39-05-12)
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Frequently Asked Questions
What is the main challenge for silicon anodes in lithium-ion batteries?
Silicon anodes suffer from large volume expansion (~300%) during lithiation, leading to material fracture, electrical disconnection, and rapid capacity degradation.
How does the proposed strategy address silicon anode issues?
The strategy uses a top-down method to create microsize porous silicon, providing internal voids to accommodate volume changes, and applies a nitrogen-doped carbon coating from polyacrylonitrile to enhance structural integrity and ionic-electronic transport.
What is the effect of heat treatment temperature on the PAN coating?
Treatment at 400 °C retains a high nitrogen content of 11.35 at% in the PAN coating, forming C-N and C-O bonds that improve transport properties, while higher temperatures may reduce nitrogen content and alter the carbon structure.
What electrochemical performance does the optimized anode achieve?
The optimized anode delivers a specific capacity of 857.6 mAh g−1 after 200 cycles at a high current density of 4 A g−1, demonstrating remarkable cycling stability.
What are the potential applications of this material?
The porous silicon/carbon composite anode shows great potential for high-capacity energy storage applications, particularly in lithium-ion batteries for electric vehicles and portable electronics.
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