Scalable 3D porous residual Al-doped Si/SiOx composites for high performance anodes: Coupling effects of porosity, conductive sites and oxide layer

Abstract

The micron-sized porous residual Al-doped Si/SiOx composite (∼6 μm) for high performance anodes is synthesized by the scalable method of dealloying corrosion. The porosity of the ideal porous structure PSi9 with inner 3D interconnected channels is 82.04%, which can buffer enormous volume expansion of Si. The thickness of the outer SiOx/Si layer on the surface of porous Si is approximately 10 nm, which can decrease the surface contact between the Si and electrolyte, and further buffer the volume change. The composition and proportion changes of Si at different depths of the SiOx/Si layer are analyzed based on Ar ion etching and X-ray photoelectron spectroscopy (XPS). The proportions of Si4+/Si0, Si3+, and Si4+ decrease as corrosion depth increase, and the corresponding proportion of Si0 with reversible capacity increases from 15.37% to 74.61%, which can undergo alloying/dealloying reaction with Li+ and further improve the electrical performance. The best initial discharge and charge capacities of porous residual Al-doped Si/SiOx composite at 1.0 Ag-1 are 3058.7 and 2364.4 mAhg−1, those can reach 903.2, and 899.7 mAhg−1 after 300 cycles, which display attractive application prospects for lithium ion batteries.