Aerogel Constructed by Ultrasmall Mn-Doped Silica Nanoparticles for Superior Lithium-Ion Storage.

Abstract

The high internal stress during (de)lithiation, poor ionic/electronic conductivity, and relatively low specific capacity are the three critical issues for the applications of silica (SiO2) anodes. Herein, a high-performance SiO2 anode is designed from the microscale to the atomic scale, and for the first time, an aerogel constructed by the graphene and manganese atom (Mn)-doped ultrasmall SiO2 nanoparticles (around 50 nm) is proposed to overcome the three issues. From the aspect of microscale, the ultrasmall SiO2 nanoparticles and the porous feature of aerogel improve the structural stability during (de)lithiation and the lithium-ion diffusion kinetics. From the aspect of atomic scale, the doping of Mn introduces the impurity level, expands the coordination environment, and enhances the adsorption for Li+, boosting the ionic/electronic conductivity and the amount of the Li+ intercalation. Therefore, the anode ranks among the best SiOx (0 < x ≤ 2) anodes. For example, the capacity is almost constant after 2000 cycles, and the specific capacities are around 1800, 1600, and 1300 mAh/g at 0.5, 1, and 3 A/g, respectively. Moreover, the reinforced reasons are revealed based on the density functional theory simulations and experiments.