Carbon-based anode materials are widely used in lithium-ion batteries due to their minimal volume change during charge and discharge, excellent cycle stability, and intrinsic ability to conduct both ions and electrons. Additionally, silicon shares similar chemical properties with carbon, allowing them to form a strong bond. As a result, carbon is often chosen as the ideal substrate for combining with silicon, enhancing the performance of the composite.
In Si/C composite systems, silicon serves as the active material that stores lithium ions, while carbon plays a crucial role in mitigating the volume expansion of silicon during cycling. It also improves the electrical conductivity of the silicon and prevents particle agglomeration, which can degrade performance over time. This synergy between silicon and carbon leads to high specific capacity and long cycle life, making Si/C composites a promising candidate to replace traditional graphite anodes in next-generation batteries.
When it comes to the structural design of silicon-carbon composites, two main configurations are commonly studied: coating structures and embedded structures. Among these, the coating structure involves applying a carbon layer around silicon particles to reduce the impact of volume changes and enhance conductivity. Based on the arrangement of the layers, this type of structure can be further categorized into core-shell, egg-yolk-shell, and porous types.
The egg-yolk-shell structure represents an advanced configuration that builds upon the core-shell model by introducing a void space between the inner silicon core and the outer carbon shell. This unique architecture allows the silicon core to expand freely without damaging the surrounding carbon layer, thus maintaining the integrity of the composite material during repeated charge-discharge cycles. This feature not only enhances structural stability but also supports the formation of a robust solid electrolyte interphase (SEI) film, which is critical for battery performance and longevity.
Researchers such as Zhou et al. have successfully fabricated egg-yolk-shell Si@void@C composites using a sol-gel method followed by pyrolysis with sucrose as the carbon source. After etching the SiO₂ layer with HF, they achieved a composite with 28.54% silicon content. Compared to conventional silicon nanoparticles or hollow carbon, the Si@void@C showed significantly improved cycle performance, with a first specific capacity of 813.9 mA·h/g and a capacity retention of 500 mA·h/g after 40 cycles.
Similarly, Tao et al. developed a stable Si@void@C composite through a comparable process. Their results showed that after 100 cycles, the composite retained a specific capacity of 780 mA·h/g. Interestingly, optimizing the carbon loading revealed that a 63% carbon content yielded better performance than a 72% loading, highlighting the need for careful structural optimization to maximize the capacity of such composites.
Liu et al. used polydopamine as a carbon precursor to synthesize Si@void@C composites. Their design allowed sufficient space between the silicon core and the thin carbon layer, preventing damage to the shell during lithiation. This ensured the formation of a stable SEI film, which is essential for maintaining good electrochemical performance over time.
The Si@void@C composite demonstrated remarkable electrochemical performance, achieving a reversible capacity of up to 2800 mA·h/g at 0.1 C, retaining 74% of its initial capacity after 1000 cycles, and exhibiting a Coulombic efficiency of 99.84%. These results highlight the potential of this structure for high-performance energy storage applications.
More recently, researchers have introduced a multi-shell concept into the design of egg-yolk-shell Si/C composites to improve mechanical strength and better accommodate the volume expansion of silicon. This approach aims to enhance the overall durability and stability of the material under prolonged cycling conditions.
For example, Sun et al. prepared a Si@void@SiOâ‚‚ composite using a vesicle template method, then coated the inner surface of the porous SiOâ‚‚ shell with polysaccharide before pyrolyzing it to form a Si@void@C@SiOâ‚‚@C structure. After etching the SiOâ‚‚ layer with HF, they obtained a double-shell composite (Si@DC), as shown in the figure. The introduction of a second carbon layer significantly improved the electrical conductivity of the material.
At a current density of 50 mA/g, the Si@DC composite maintained a specific discharge capacity of 943.8 mA·h/g after 80 cycles, far outperforming both the single-shell Si@SC and pure silicon particles, which dropped to 719.8 and 115.3 mA·h/g, respectively. This demonstrates the effectiveness of the double-shell design in stabilizing the structure and improving electrochemical performance.
Yang et al. also developed a double-shell composite (Si@void@SiO₂@void@C) by sequentially coating SiO₂ and carbon layers on silicon nanoparticles using the Stöber and pyrolysis methods. Their material exhibited exceptional cycle stability, maintaining a capacity of 956 mA·h/g after 430 cycles at 460 mA/g, with a capacity retention rate of 83%. In contrast, the Si@C core-shell material experienced significant capacity decay within the first 10 cycles, dropping below 200 mA·h/g after 430 cycles.
The dual-layer structure consisting of SiOâ‚‚ and carbon provides multiple benefits. The carbon layer enhances electrical conductivity, the SiOâ‚‚ layer increases structural stability, and the cavities offer space for silicon expansion. Moreover, the double-shell layers act as a barrier, preventing direct contact between the silicon nanoparticles and the electrolyte, thereby reducing unwanted side reactions and improving the overall safety and performance of the battery.
In the field of sensor technology, SVLEC has a complete set of diverse technologies and their different working principles. You can order high-quality Sensors and systems that are suitable for various purposes and meet various requirements from our company, from linear displacement detection and identification to target detection and fluid measurement. Suitable for daily industrial applications and arduous use in critical environments. To match it, we provide you with the best network and connection technology and a wide range of accessory products.
Sensor Actuator, Pressure Switch,Led light,Multi-Functional Signal Light, led indicator
Kunshan SVL Electric Co.,Ltd , https://www.svlelectric.com