PANI-Encapsulated Si Nanocomposites with a Chemical Bond Linkage in the Interface Exhibiting Higher Electrochemical Stability as Anode Materials for Lithium-Ion Batteries

Abstract

A covalent linkage between polyaniline (PANI) and Si nanoparticles in PANI-encapsulated Si nanocomposites was proposed and achieved by a facile and economical synthetic strategy, in which NH2-grafted Si was first obtained via a chemical modification of Si surface and the polymerization of aniline initiated at NH2 group surface was readily accomplished to get PANI shell. The characterizations suggested that NH2 groups were successfully introduced onto Si surface and PANI-encapsulated Si nanocomposites with a core/shell structure were fabricated. Electrochemical tests showed that our proposed Si nanocomposites delivered a high initial specific capacity of 2135[Formula: see text]mAh/g and retained 848[Formula: see text]mAh/g after 100 charge/discharge cycles at a current density of 0.1[Formula: see text]A/g, which were superior than that of the normal PANI-encapsulated Si nanocomposites with the absence of chemical bonds in the interface. The enhanced electrochemical performance was ascribed to the surface chemical modification and the introduction of chemical bond in the interface. NH2 group function of Si could improve the homogeneity of encapsulated PANI shell. Additionally, PANI was tightly anchored to Si nanoparticles via a covalent bond between silicon and PANI, which would greatly inhibit the separation of PANI from Si surface during the expansion/contraction of Si particles. Thus, the structural integrity was maintained. Besides, PANI layer with a unique structure promoted the transport of both electrons and lithium ions.