Encapsulating silicon particles by graphitic carbon enables High-performance Lithium-ion batteries

Silicon combines the advantages of high theoretical specific capacity, low potential and natural abundance, which exhibits great promise as an anode for lithium-ion batteries. However, the main challenges associated with Si anode are continuous volume expansion upon cycling and intrinsic low electronic conductivity, leading to sluggish reaction kinetics and rapid capacity fading. Herein we propose a novel in-situ self-catalytic strategy for the growth of highly graphitic carbon to encapsulate Si nanoparticles by chemical vapor deposition, where the magnesiothermic reduction byproducts are used as templates and catalysts for the formation of three-dimensional (3D) conductive network architecture. Benefiting from the improved electronic conductivity and significant suppression of volume expansion, the as-synthesized Si carbon composites exhibit excellent lithium storage capabilities in terms of high specific capacity (2126 mAh g-1 at 0.1 A g-1), remarkable rate capability (750 mAh g-1 at 5 A g-1), and good cycling stability over 450 cycles. Furthermore, the as-fabricated full cell (Si//Ni-rich LiNi0.815Co0.185-xAlxO2) shows high energy density of 395.1 Wh kg-1 and long-term stable cyclability. Significantly, this work demonstrates the effectiveness of in-situ self-catalysis reaction by using magnesiothermic reduction byproducts catalytically derived carbon matrix to encapsulate alloy-type anode material in giving rise to the overall energy storage performance.