Silicon Carbide as a protective layer to inhibit the chemical formation reaction of Li2SiF6 for stable Si-based anode

Si-based materials are the promising anode candidates for the next generation lithium-ion battery. However, the poor cycle performance has hindered their practical applications. Herein, a fresh and fundamental reason for the rapid capacity decay of silicon-based materials was proclaimed. Silicon can chemically react with LiPF6 and generate Li2SiF6 aggregations constantly during cycling. Moreover, nano carbon on the surface of silicon acted as a catalyst to accelerate such detrimental reaction. Herein, taking advantage of high strength and toughness of SiC, SiC layer was rationally introduced between inner silicon and outer carbon to inhibit the chemical formation reaction of Li2SiF6. The side reaction rate reduced by 10 times than that of Si, and 300 times than that of Si@C, attributed to the increased activation energy of Li2SiF6 formation reaction. The Si@SiC@C maintained a specific capacity of 980 mAh g-1 at the current density of 1 A g-1 after 800 cycles with the initial Coulombic efficiency (ICE) over 88.5%. This work will shed fresh light on the degradation of Si-based materials and further guide the rational design of silicon structures for high-performance Si-based materials.

Fei Wei Cheungkong scholar Professor, Director of Beijing key lab of green chemical reaction engineering and technology, Fei Wei obtained his PhD in chemical engineering from China University of Petroleum in 1990. After a postdoctoral fellowship at Tsinghua University (China), he was appointed an associate professor in 1992 and professor of chemical engineering of Tsinghua University (China) in 1996. His scientific interests are technological applications of chemical reaction engineering, multiphase flow, carbon nano materials, and sustainable energy. He has designed and successfully running over 30 industrial fluidized bed reactors, and authored three books and over 600 refereed publications with more than 36000 citations with H index 86.