多孔硅碳复合材料实现高性能锂离子电池

Porous silicon/carbon composites as anodes for high-performance lithium-ion batteries

  • 摘要: 硅负极是锂离子电池理想的候选材料。然而,其显著的体积膨胀会导致严重的材料断裂,失去电接触,从而限制了其实际应用。本研究提出了一种新的自上而下的多孔硅制备策略,并引入聚丙烯腈(PAN)作为掺氮炭涂层,旨在保持硅负极的内部空间,缓解硅负极在锂化和脱锂过程中向外膨胀的问题。随后,探讨了温度对PAN热转变行为和复合电极电化学行为的影响。在400 °C下处理后,PAN涂层保留了11.35%的高氮掺杂含量,这明确证实了C―N和C―O键的存在,从而改善了离子电子传输特性。这种处理方法不仅保留了更完整的炭层结构,还引入了炭缺陷,即使在大电流下也能稳定循环。当以4 A g−1的电流循环时,优化后的负极在循环200次后仍具有857.6 mAh g−1的比容量,表明其在高容量储能应用方面的巨大潜力。

     

    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.

     

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