【摘要】 以酚醛树脂包覆纳米硅颗粒后通过碳化处理,制备了具有核壳结构的Si/C复合负极材料,并研究了碳化温度和电极中活性物质含量对储锂性能的影响。透射电子显微镜分析结果表明,该复合材料由厚度为5~15nm的无定型碳壳包覆的硅颗粒组成。电化学测试表明,750℃碳化所得复合材料在活性材料∶粘结剂∶乙炔黑=1∶1∶1(质量比)时,初始放电容量为1836mAh/g(首次库仑效率84.8%),循环50次后仍可保持873mAh/g的可逆容量。此外,具有核壳结构的Si/C复合负极比纯硅负极表现出更好的循环稳定性,这可能是因为碳壳的存在缓解了硅的体积膨胀、改善硅的导电性,在一定程度上保证了Li+嵌入和脱出过程的稳定进行。更多还原

【Abstract】 Core-shell Si/C composites(Si@C)cathodes were prepared by coating resorcinol-formaldehyde resin on commercial Si nano-particles(nano-Si)followed by a carbonization process.Afterwards,the effects of carbonization temperature and composition ratio of cathode material on electrochemical performance of electrode were investigated systematically.The transmission electron microscope(TEM)analysis indicated that Si@C consisted of nano-Si was coated by uniform amorphous carbon shell(thickness:5~15 nm).Electrochemical tests revealed that with an ratio of 1∶1∶1(active material∶carbon black∶binder),Si@C carbonized at 750℃ showed an initial discharge capacity of 1836 mAh/g(initial coulombic efficiency:84.8%).They still delivered reversible capacity of 873 mAh/g after 50 cycles.Besides,Si@C showed improved cycling stability compared with the bare nano-Si,possibly because the uniform and conductive carbon shells facilitated the reaction kinetic of Li+intercalation/extraction to some extent by alleviating the volume expansion and enhancing the electrical conductivity of Si.更多还原