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 (LiPF₆) to constantly generate lithium hexafluorosilicate (Li₂SiF₆) 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 Li₂SiF₆. 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^-1 at a current density of 1 A g^-1 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.