氮掺杂碳包覆多孔硅微球的制备及电化学性能

Preparation and electrochemical performance of nitrogen-doped carbon-coated porous silicon microspheres

以铝硅合金(AlSi)粉末为原料,采用脱合金法获得多孔硅(porous silicon,P-Si)微球。再采用原位化学聚合法在P-Si微球表面包覆聚吡咯(PPy),得到PPy包覆的P-Si微球(P-Si@PPy),最后将P-Si@PPy置于Ar气氛中在800℃下煅烧3 h得到氮掺杂碳包覆多孔硅(nitrogen-doped carbon-coated porous silicon,P-Si@NC)微球。利用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)以及电化学测试等手段对材料的形貌、结构及电化学性能进行表征。结果表明,多孔硅微球直径在1μm左右,氮掺杂碳层的厚度约为18 nm。将P-Si@NC复合材料应用于锂离子电池负极,在0.1 A/g电流密度下首次放电比容量高达2609.2 mAh/g,首次库伦效率达87.52%,充放电循环50次后放电比容量仍能达到1574.8 mAh/g,展示出优异的电化学性能。P-Si@NC微球的多孔结构为嵌/脱锂过程中硅的膨胀/收缩提供了缓冲空间,氮掺杂碳层既作为保护层维持颗粒的完整性,又加速了锂离子和电子转移。

Porous silicon(P-Si)microspheres were obtained by dealloying method using AlSi powders as raw material.Then,the surface of P-Si microspheres was coated with polypyrrole(PPy)by in situ chemical oxidation polymerization to get PPy-coated P-Si microspheres(P-Si@PPy).Finally,P-Si@PPy was calcined at 800℃for 3 h in an Ar atmosphere to obtain nitrogen-doped carbon-coated porous silicon(P-Si@NC)microspheres.The morphology,structure,and electrochemical properties of the as-prepared P-Si@NC were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and electrochemical tests.The results show that the diameter of porous silicon microspheres is about 1μm and the thickness of nitrogen-doped carbon layer is about 18 nm.When P-Si@NC composites are used as the anode of lithium-ion batteries,the initial discharge specific capacity is up to 2609.2 mAh/g at a current of 0.1 A/g with a high coulombic efficiency of 87.5%,and a discharge specific capacity of 1574.8 mAh/g is achieved after 50 cycles,exhibiting excellent electrochemical performance.The porous structure of P-Si@NC provides a buffer space for the expansion/contraction of silicon during the lithiation/delithiation process,and the nitrogen-doped carbon layer not only serves as a protective layer to maintain the particle integrity,but also accelerates the transfer rate of lithium ions and electrons.