Thermal polymerization of ion-modified carbon dots into multi-functional LiF-carbon interface for stabilizing SiO anode

Abstract

SiO has been demonstrated as one type of promising high-capacity anode for Li-ion batteries. However, the parasitic reactions between the electrolyte and SiO interface, severer than that of the well-developed graphite, are generally overlook. Herein, a multi-functional LiF-carbon co-coating layer on SiO (SiO@LCD) is designed to resist the interfacial reactions, which originates from thermal-assembly of zero-dimensional Li-absorbed and F-doped carbon dots produced by hydro/alcohol-thermal reaction of discarded wood sawdust with a high yield of 96.9 %. Combined with advanced spectroscopy characterizations and theoretical calculations, the LiF-carbon co-coating layer has been determined to induce preferential decomposition of LiPF6 to form a thin and dense solid electrolyte interface (SEI) with LiF-rich inner layer, and promote the rapid transmission of ion/electron. As a result, the initial Coulombic efficiency (CE) of the SiO@LCD increases from 66.1 % to 78.6 %, and the average CE is increased by 0.3 % at 0.2 A g−1 with enhanced rate capability and cycling stability during the (de)lithiation process. More importantly, the assembled 3.7 Ah pouch cell exhibits a long-term cycling life over 400 cycles at 0.2 C with the capacity retention of 85.1 %.