Nanoporous SiOx coated amorphous silicon anode material with robust mechanical behavior for high-performance rechargeable Li-ion batteries

Abstract

Silicon is a promising anode material for rechargeable Li-ion battery (LIB) due to its high energy density and relatively low operating voltage. However, silicon based electrodes suffer from rapid capacity degradation during electrochemical cycling. The capacity decay is predominantly caused by (i) cracking due to large volume variations during lithium insertion/extraction and (ii) surface degradation due to excessive solid electrolyte interface (SEI) formation. In this work, we demonstrate that coating of a-Si thin film with a Li-active, nanoporous SiOx layer can result in exceptional electrochemical performance in Li-ion battery. The SiOx layer provides improved cracking resistance to the thin film and prevent the active material loss due to excessive SEI formation, benefiting the electrode cycling stability. Half-cell experiments using this anode material show an initial reversible capacity of 2173 mAh g−1 with an excellent coulombic efficiency of 90.9%. Furthermore, the electrode shows remarkable capacity retention of ∼97% after 100 cycles at C/2 charging rate. The proposed anode architecture is free from Li-inactive binders and conductive additives and provides mechanical stability during the charge/discharge process. Keywords: Amorphous silicon, Thin film, Solid electrolyte interphase, Silicon oxide, Anode, Li-ion battery