A facile, low-cost synthesis of high-performance silicon-based composite anodes with high tap density for lithium-ion batteries†
Micro-sized carbon-coated Si-based composites have been developed by a simple mechanochemical reaction between SiO, Ni, and Al, followed by an additional milling process with graphite. The resultant carbon-coated Si-based composite exhibits a reversible capacity of over 580 mA h g−1 after 200 cycles with a considerably higher tap density of ∼1.34 g cm−3 compared to nanosized Si (∼0.16 g cm−3). The improvement in the electrochemical performance is achieved due to both highly conductive NiSi2 nanoinclusions and amorphous Al2O3 buffer matrix in the composite. Upon cycling, the multifunctional NiSi2 phase not only provides enhanced electronic conductivity but also suppresses the formation of crystalline Li15Si4 that causes an inhomogeneous volume change. Simultaneously, amorphous Al2O3 plays a crucial role in maintaining particle connectivity by impeding the agglomeration of active Si nanocrystallites. The combination of these advantages with a low-cost, scalable, and environmentally benign synthetic process make the Si-based composite a promising alternative anode for high performance Li-ion batteries.