Regulating Lithium Transfer Pathway to Avoid Capacity Fading of Nano Si Through Sub-Nano Scale Interfused Siox /C Coating.

Abstract

Si nanoparticles (NPs) are considered as a promising high-capacity anode material owing to their ability to prevent mechanical failure from drastic volume change during (de)lithiation. However, upon cycling, a quick capacity fading is still observed for Si NPs, and the underlying mechanism remains elusive. In this contribution, we demonstrate that the quick capacity fading is mainly caused by the generation of dead (electrochemically inert) Si with blocked electron conductivity in a densely composited Si/SEI (solid electrolyte interface) hybrid. This is due to the combined influence of electrolyte-related side reactions and the accompanied agglomeration of Si NPs. We construct a compact, sub-nano scale interfused SiOx /C composite coating onto the Si NPs, and achieve a highly stabilized electrochemistry upon long cycling. The SiOx /C coating with electron/ion dual transport paths and robust mechanical flexibility enables a fast and stable lithium ion/electron dual diffusion pathway towards the encapsulated Si. With fast reaction kinetics, stable SEI, and an anti-agglomeration feature, the obtained Si@SiOx /C composite demonstrates a stable high capacity. This work unravels new perspectives on the capacity fading of Si NPs and provides an effective encapsulating method to remedy the structure degradation and capacity fading of nano Si. This article is protected by copyright. All rights reserved.