Key Takeaways & Executive Findings
- •• • Silicon anodes exhibit a theoretical capacity of 4200 mAh g−1, which is more than 11 times higher than graphite's 372 mAh g−1, yet their practical application is limited by severe volume expansion and low conductivity; Si/C composites address these issues by integrating carbon matrices. • • Ball milling, spray drying, electrostatic spinning, and CVD are the primary preparation methods for Si/C composites; each offers distinct advantages in controlling particle size, morphology, and carbon coating uniformity, directly impacting electrochemical performance. • • Carbon precursor coating and silicon surface modification are effective structural engineering strategies that improve electrical conductivity and buffer volume changes, leading to enhanced cycling stability and rate capability. • • Recent studies report Si/C composite anodes with specific capacities exceeding 1000 mAh g−1 and stable cycling over hundreds of cycles, demonstrating the potential for high-energy-density LIBs; however, scalable production and cost reduction remain critical challenges for commercialization.
Abstract
Silicon/carbon (Si/C) composites are promising anode materials for high-energy-density lithium-ion batteries (LIBs) because they mitigate the severe volume expansion and poor electrical conductivity of pure silicon anodes. This review systematically summarizes the state-of-the-art preparation methods for Si/C composites, including ball milling, spray drying, electrostatic spinning, and chemical vapor deposition (CVD). Structural engineering strategies, such as carbon precursor coating, silicon-precursor-based wet chemistry, and silicon surface modification, are critically assessed for their effectiveness in enhancing electrical conductivity, buffering volume changes, and improving overall electrochemical performance. The review highlights that while Si offers a theoretical capacity of 4200 mAh g−1, far exceeding graphite's 372 mAh g−1, its practical application is hindered by capacity fading and low initial coulombic efficiency. The integration of carbon matrices not only provides mechanical flexibility but also facilitates electron transport. Key performance metrics from recent studies, including specific capacities exceeding 1000 mAh g−1 and improved cycling stability over hundreds of cycles, are discussed. The review also addresses the challenges of scalable production and cost-effectiveness, emphasizing the need for optimized precursor selection and processing parameters. Future research directions are proposed, focusing on the rational design of hierarchical structures and the development of novel binders to further enhance the long-term durability of Si/C anodes. This comprehensive overview serves as a valuable resource for researchers and engineers aiming to advance the commercialization of high-energy-density LIBs.
1. Introduction
Lithium-ion batteries (LIBs) are ubiquitous in modern electronics, electric vehicles, and energy storage systems, yet their energy density remains a bottleneck for extended usage and range. The energy density of a LIB is governed by the capacities of both cathode and anode materials, as well as the overall cell weight. While cathode development has progressed, the commercial graphite anode, with a theoretical capacity of only 372 mAh g−1, limits the achievable energy density. Silicon (Si) has emerged as a compelling alternative due to its exceptional theoretical capacity of 4200 mAh g−1 and natural abundance. However, Si anodes suffer from two critical drawbacks: a massive volume change (~300%) during lithiation/delithiation, which leads to electrode pulverization and capacity fading, and intrinsically low electrical conductivity, which hampers rate performance.
To overcome these challenges, silicon/carbon (Si/C) composites have been developed, leveraging the high capacity of Si and the mechanical flexibility and electrical conductivity of carbon materials. This review critically examines the preparation methods for Si/C composites, including ball milling, spray drying, electrostatic spinning, and chemical vapor deposition, and evaluates structural engineering strategies such as carbon precursor coating and silicon surface modification. By optimizing these parameters, Si/C composites can achieve enhanced cycling stability and rate capability, bringing high-energy-density LIBs closer to practical application. The review also addresses the industrial scalability and cost-effectiveness of these approaches, providing a roadmap for future research and development.
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ZHANG Lei, PENG Yuhua, ZHAO Liping, LUO Yu (2026). Progress in the Preparation of Silicon/Carbon Composites for Use as Anodes in Lithium-Ion Batteries. New Carbon Materials. https://doi.org/10.1016/S1872-5805(26)61097-9
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Frequently Asked Questions
What are the primary failure mechanisms of Si/C composite anodes under prolonged cycling, and how do the preparation methods address them?
The primary failure mechanisms include volume expansion-induced electrode pulverization, continuous solid electrolyte interphase (SEI) formation, and loss of electrical contact. Ball milling and spray drying can produce uniform Si/C composites with carbon coatings that buffer volume changes and maintain structural integrity. CVD allows for conformal carbon coatings that enhance conductivity and reduce electrolyte decomposition. Electrostatic spinning creates fibrous structures that accommodate strain. These methods collectively improve cycling stability by mitigating mechanical stress and stabilizing the SEI layer.
How do the different preparation methods (ball milling, spray drying, electrostatic spinning, CVD) compare in terms of scalability and cost for industrial production?
Ball milling is a simple, cost-effective method suitable for large-scale production, but it may result in less uniform carbon coating. Spray drying is also scalable and offers good control over particle morphology, but requires careful optimization of slurry properties. Electrostatic spinning is more complex and less scalable, but produces unique fibrous structures with high surface area. CVD provides high-quality, uniform coatings but is expensive and requires specialized equipment. For industrial adoption, ball milling and spray drying are currently more feasible, while CVD may be reserved for high-end applications where performance justifies cost.
What are the typical specific capacities and cycling stability achieved by Si/C composites prepared via these methods, and how do they compare to graphite anodes?
Si/C composites prepared via these methods typically exhibit specific capacities ranging from 800 to 1500 mAh g−1, with some reports exceeding 2000 mAh g−1 for optimized structures. They can maintain capacity retention of over 80% after 200-500 cycles, depending on the Si content and carbon coating quality. In contrast, graphite anodes have a theoretical capacity of 372 mAh g−1 and practical capacities around 350 mAh g−1 with excellent cycling stability. Si/C composites offer significantly higher energy density but require further optimization to match graphite's longevity.
How does the initial coulombic efficiency (ICE) of Si/C composites compare to graphite, and what strategies are employed to improve it?
Si/C composites often suffer from lower ICE (typically 70-85%) compared to graphite (>90%) due to irreversible reactions forming SEI on high-surface-area carbon and Si. Strategies to improve ICE include prelithiation, surface coating with thin carbon layers, and using carbon precursors that form less reactive surfaces. For instance, CVD coatings can reduce surface area and side reactions, while controlled pyrolysis of carbon precursors can create a dense carbon layer that minimizes electrolyte decomposition.
What are the key challenges in scaling up Si/C composite production from laboratory to industrial scale, and what solutions are proposed?
Key challenges include achieving uniform Si dispersion and carbon coating at scale, controlling particle size distribution, and reducing production costs. Ball milling and spray drying are amenable to scale-up but require careful control of process parameters to maintain quality. CVD is less scalable due to high costs and batch processing. Solutions include developing continuous production lines, using low-cost silicon precursors (e.g., metallurgical-grade Si), and optimizing carbon sources (e.g., biomass-derived carbon). Additionally, process automation and quality control are essential to ensure batch-to-batch consistency.
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