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。
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:5～15nm).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 873mAh/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.
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基金资助
国家自然科学基金(51502194);山西省科学技术基金会(2014021019-4);山西省科技关键创新研究团队(2012041011);高性能陶瓷和超微观结构的国家重点实验室开放项目(SKL201511SIC)
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