氮掺杂碳层包覆椭球状多孔微米硅负极材料的制备及储能研究

Preparation and Energy Storage of Ellipsoidal Porous Micron Silicon Anode Material Coated with Nitrogen-Doped Carbon Layer

摘要:

硅（Si）材料因高的理论比容量（4 200 mAh?g^-1）和优异的嵌锂容量，被广泛认为是下一代锂离子电池最具有潜力的负极材料。近年来，各种纳米和微米尺度的硅材料被设计和合成，如纳米硅线、空心球等。相比于昂贵的纳米硅材料，微米硅材料因容量高和成本低，逐渐成为锂离子电池负极材料的重要研究方向。然而，微米硅负极材料在脱嵌锂的过程中存在严重的体积膨胀和粉化问题，导致其首次库伦效率低，循环稳定性差。为此，采用两次酸刻蚀法和原位聚合反应，以微米铝硅合金球为原料，制备了氮掺杂碳层包覆的椭球状多孔微米硅（CPSi@C_N）复合材料。结果表明，CPSi@C_N的多孔结构有效缓解了硅在循环中的体积膨胀，促进了离子传输。说明，表面纳米碳层能调控CPSi@C_N复合材料的体积膨胀，减少副反应，从而提高了循环稳定性。同时，氮元素的掺杂进一步提升了碳层的离子传输性能和导电性，增加了活性位点。作为锂离子电池负极材料CPSi@C_N，其在2.4 mg?cm^-2的负载量和1.0 A?g^-1的电流密度下循环100次，比容量仍保持为705.16 mAh?g^-1、首次库伦效率达到80%，在5.0 A?g^-1的电流密度下比容量为429.97 mAh?g^-1，当恢复至小电流0.2 A?g^-1时容量恢复率达92%。表明，所制备的CPSi@C_N负极材料，具有高的首次库伦效率、优良的倍率性能和循环稳定性，在电动汽车和储能设备等领域的应用前景广阔。

Abstract:

Silicon （Si）， with its high theoretical specific capacity （4 200 mAh?g^-1） and excellent lithium intercalation capacity， is considered a promising anode material for next-generation of lithium-ion batteries， potentially replacing graphite. In recent years， a variety of nano- and micro-scale silicon structures， such as nano-silicon wires， hollow spheres， have been developed. Compared with expensive nano-silicon materials， micro-silicon materials are gaining attention due to their high capacity and low cost. However， micro-silicon anode materials face challenges such as volume expansion and pulverization during lithium intercalation and deintercalation， leading to low initial coulombic efficiency and rapid capacity decay over long cycles. This study applies micron-sized Al-Si alloy balls as precursors to synthesize an ellipsoidal， porous micro-silicon coated with nitrogen-doped carbon layer （CPSi@C_N） composite material through dual acid etching and in-situ polymerization. Results indicate that the porous structure of CPSi@C_N composites effectively mitigates silicon's volume expansion during cycling and enhances ion transport. The surface nano-carbon layer modulates volume expansion and minimizes side reactions， improving cycle stability. Additionally， nitrogen doping enhances ion transport capacity and conductivity of the carbon layer， increasing active sites. As an anode material for lithium-ion batteries， CPSi@C_N maintains a specific capacity of 705.16 mAh?g^-1 after 100 cycles at a loading of 2.4 mg?cm^-2 and a current density of 1.0 A?g^-1， acheving an initial coulombic efficiency of 80%. In rate capability tests， it delivers a specific capacity of 429.97 mAh?g^-1 at a current density of 5.0 A?g^-1 and retains 92% capacity when returned to 0.2 A?g^-1. The nitrogen-doped carbon-coated ellipsoidal porous micron silicon anode material coated shows high initial coulombic efficiency， excellent rate capability， and outstanding cycling stability， showing significant promise as a high-performance anode material for lithium-ion batteries in electric vehicles and energy storage applications.