Regulating adhesion of solid-electrolyte interphase to silicon via covalent bonding strategy towards high Coulombic-efficiency anodes

Abstract

Nanostructured silicon-based materials are the promising anodes for next-generation lithium-ion batteries. However, as the result of the weak adhesion of solid-electrolyte interphase (SEI) to Si, the fracture, exfoliation and subsequent regrowth of SEI layer on the expanded Si remains unsolved, leading to low initial Coulombic efficiency (ICE) (50–80%). Herein, the Ti‒Si covalent bond between nano-Si and MXene-derived artificial SEI layer is elaborately introduced, to effectively strengthen the interfacial stability and suppress the excessive interfacial side reaction. Upon the three-times expansion during first cycling, the as-obtained anodes with the ultrathin SEI still deliver a high ICE of 91.4%. Due to the stable interfacial ionic conduction, remarkable capacity retention of 90.7% after 1000 cycles at 5 A g −1 with an average Coulombic efficiency of 99.8% could be maintained. This strategy provides new insight into designing durable alloy anodes from the point of the interfacial adhesion strength. The low initial Coulombic efficiency (ICE) of nanostructured Si-based anodes remains unsolved. In this work, a covalently bonded SEI layer design is proposed for the first time to achieve high ICE. The high interfacial adhesion induced by the strong Ti‒Si covalent bond avoids the fracture and exfoliation of SEI layer, leading to the ultrathin SEI layer of 10 nm and high ICE of 91.4%. Our work provides a new insight into designing high ICE alloy anodes from the point of the interfacial adhesion strength. • A robust artificial SEI layer with abundant covalent bonds on Si anode is rationally designed. • An ultrathin SEI layer of 10 nm is obtained owing to the tremendously decreased interfacial side reaction upon cycling. • High initial Coulombic efficiency of 91.4% and robust cycling stability over 1000 cycles are achieved.