Self-Rearrangement of Silicon Nanoparticles Embedded in Micro-Carbon Sphere Framework for High-Energy and Long-Life Lithium-Ion Batteries

Despite its highest theoretical capacity, the practical applications of the silicon anode are still limited by severe capacity fading, which is due to pulverization of the Si particles through volume change during charge and discharge. In this study, silicon nanoparticles are embedded in micron-sized porous carbon spheres (Si-MCS) via a facile hydrothermal process in order to provide a stiff carbon framework that functions as a cage to hold the pulverized silicon pieces. The carbon framework subsequently allows these silicon pieces to rearrange themselves in restricted domains within the sphere. Unlike current carbon coating methods, the Si-MCS electrode is immune to delamination. Hence, it demonstrates unprecedented excellent cyclability (capacity retention: 93.5% after 500 cycles at 0.8 A g^-1), high rate capability (with a specific capacity of 880 mAh g^-1 at the high discharge current density of 40 A g^-1), and high volumetric capacity (814.8 mAh cm^-3) on account of increased tap density. The lithium-ion battery using the new Si-MCS anode and commercial LiNi_0.6Co_0.2Mn_0.2O₂ cathode shows a high specific energy density above 300 Wh kg^-1, which is considerably higher than that of commercial graphite anodes.