Thermolytically grafted silicon particles with ultrathin carbonaceous coating rich of phenyl moieties as lithium-storage anode material

Abstract

The most critical bottleneck of Si anode materials is an inevitable cracking and pulverization of Si nanostructure during electrochemical cycling process, resulting in a significant loss of electrical contact and rapid capacity fading. The low-temperature thermolytic grafting process at 360-400 degrees C was employed to produce a conformal carbon coating on a bundle-like porous silicon (por-Si) prepared by silver-assisted chemical etching. During the thermolytic grafting process, polystyrene infiltrated in the por-Si was depolymerized into styrenic carbon fragments rich of phenyl moieties. The styrenic carbon fragments were subsequently grafted uniformly on the por-Si surface as an ultrathin carbonaceous film of 5 nm, which was confirmed by transmission electronic microscope, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. The polystyrene grafted por-Si (por-Si@PS) was employed as a lithium-storage anode material. After 100 cycles at a current rate of 0.5C, the por-Si@PS anode exhibited an excellent reversible capacity of 1938.82 mAh g(-1), when compared to those of por-Si and pristine Si anodes with 1228.57 mAh g(-1) and 117.43 mAh g(-1). The por-Si@PS exhibited a good recovery capability of 93.1% in the C-rate test. The ultrathin carbonaceous coating rich of phenyl moieties not only prevents the rapid pulverization of nanostructured Si, but also enhances the interfacial properties of por-Si@PS as lithium-storage anode material. Notably, the thermolytically grafted Si-C species rich of phenyl moieties played as a strong adhesive passivation layer against the corrosive electrochemical agents during cycling.