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

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 SiO (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.