Silicon Carbide as a Protective Layer to Stabilize Si-Based Anodes by Inhibiting Chemical Reactions.

Developing a practical silicon-based (Si-based) anode is a precondition for high-performance lithium-ion batteries. However, the chemical reactivity of the Si renders it liable to be consumed, which must be completely understood for it to be used in practical battery systems. Here, a fresh and fundamental mechanism is proposed for the rapid failure of Si-based materials. Silicon can chemically react with lithium hexafluorophosphate (LiPF) to constantly generate lithium hexafluorosilicate (LiSiF) aggregates during cycling. In addition, nanocarbon coated on silicon acts as a catalyst to accelerate such detrimental reactions. By taking advantage of the high strength and toughness of silicon carbide (SiC), a SiC layer is introduced between the inner silicon and outer carbon layers to inhibit the formation of LiSiF. The side reaction rate decreases significantly due to the increase in the activation energy of the reaction. Si@SiC@C maintains a specific capacity of 980 mAh g at a current density of 1 A g after 800 cycles with an initial Coulombic efficiency over 88.5%. This study will contribute to improved design of Si-based anode for high-performance Li-ion batteries.