新型核壳结构硅碳复合负极材料的制备及电化学性能

通过对氧化硅预处理得到多组分硅pSi(Si、SiO、SiO_(2)),再利用化学气相沉积法(CVD)设计了具有核壳结构的pSi与碳纳米纤维(CNF)的复合材料(pSi-CNF)。多组分硅中Si、SiO提供电化学可逆容量,SiO_(2)可以抑制硅的体积膨胀;碳纳米纤维包覆形成的壳层结构可以有效提高复合材料的导电性,同时进一步抑制硅的体积膨胀保持核壳结构的完整。通过SEM、TEM、EDS、XRD、Raman和XPS对复合物的微观结构进行分析。结果表明:pSi-CNF的粒径为5~20μm,碳纳米纤维的直径为5~40 nm,pSi-CNF复合材料中含有Si、SiO和SiO_(2)多种组分硅,有明显特征峰;碳纳米纤维均匀包覆于硅表面,形成核壳结构。电化学性能测试表明,在0.2 A·g^(−1)的电流密度下,经100次循环后其可逆容量为1411 mAh·g^(−1),容量保持率为74%,具有良好的循环稳定性和较高的可逆容量;在1 A·g^(−1)的电流密度下,经300次循环后其可逆容量为735 mAh·g^(−1),容量保持率为86%,且具有良好的倍率性能。

Influence of nitrogen hetero-substitution on the electrochemical performance of coal-based activated carbons measured in non-aqueous electrolyte

Nitrogen-containing carbons were prepared by modification of activated carbons.The modified carbons were used as electrode materials with improved electrochemical performance.Precursor anthracite was activated by KOH(KOH:anthracite= 1:1), modified by melamine or urea and then treated at 1173 K to obtain the modified carbons.The porous structure, the chemical composition and the electrochemical characteristics of the carbons were investigated by nitrogen sorption, XPS and electrochemical methods respectively.Electrochemical experiments were performed in an organic electrolytic solution of 1 M(C2H5)4NBF4/PC.The samples modified by the different methods showed differences in chemical composition that introduced varying degrees of electrochemical performance enhancement.The presence of nitrogen enhanced the electron donor properties and the surface wettability of the activated carbons:this ensured a sufficient utilization of the exposed surface for charge storage.