二次包覆对Si/C复合材料的性能影响

Effect of two times coating process on performances of Si/C composite

通过液相固化-高温热解法制备硅/碳(Si/C)复合材料,并对其进行二次碳包覆改性。采用XRD、SEM和HRTEM等手段研究材料的物理化学性能。Si/C复合材料由硅、鳞片石墨和酚醛树脂热解碳构成,并采用酚醛树脂作为无定型碳碳源对其进行二次包覆。二次包覆后,复合材料的结构并没有改变,纳米硅和鳞片石墨的衍射峰强度有所减弱,酚醛树脂热解碳的衍射宽峰稍有增强,复合材料表面更加致密均匀。电化学测试结果表明二次包覆后复合材料的首次充放电容量有所下降,但是循环稳定性得到增强。

Si/C composite was prepared by liquid solidification-pyrolysis method, followed by two times coating process with carbon. X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy were used to evaluate the physicochemical properties of the anodes. Si/C composite is composed of silicon, flake graphite and phenolic resin-pyrolyzed carbon, and was coated by phenolic resin again. The structure of the composite have no obvious change after the second time coating process, however, the diffracted intensity of silicon and flake graphite are weakened while the diffracted intensity of phenolic resin-pyrolyzed carbon is strengthened, and the surface of the composite is more homogeneous and dense. Electrochemical measurement results show the initial capacity is reduced, while the cycling stability is enhanced.