A Review: Analysis of SiO۲/C composites as high performance anodes for lithium-ion batteries

With the growing prosperity of society and economy, the demands for new energy and green resources keep increasing, and lithium-ion batteries (LIBs) have been given more attention. Lithium-ion batteries have many advantages, such as high energy density, long cycle life and no memory effect. The anode is one of the main components of a lithium-ion battery that plays a vital role in the cycle and electrochemical performance of a lithium-ion battery, depending on the active material. Therefore, it is essential to search for anode materials with high theoretical specific capacity and low cost. Presently, silicon-based materials are widely investigated because of their high capacity (pure silicon (Si): ۴۲۰۰ mAhg^(-۱); silicon monoxide (SiO): ۲۴۰۰ mAhg^(-۱); and silicon dioxide or silica (SiO_۲ ): ۱۹۶۵ mAhg^(-۱)) . Unfortunately, the silicon anode experiences considerable volume expansion because of the formation of Li–Si alloy during lithiation (Li_۲۲ Si_۵, up to ۳۰۰%). Therefore, SiO_۲ has become an alternative to Si due to its expansion volume, which is the lowest (۱۰۰%) compared to Si (۳۰۰%) and SiO (۱۵۰%). Compared to Si, the inert phase of Li_۴ SiO_۴ or Li_۲ O, formed during the lithiation process, might be used as a buffer layer to adapt to the volume changes. SiO_۲ also has a high theoretical capacity (۱۹۶۵ mAhg^(-۱)), low discharge potential, and the preparation process and the required cost are lower than those of Si-based materials. However, the low initial coulombic efficiency (۵۲.۳۸%) and electrical conductivity due to strong Si–O bonds are significant obstacles to the development of SiO_۲ as an anode material. The modified properties of SiO_۲ and the use of carbon materials as composites of SiO_۲ are effective strategies to overcome these problems. This review focuses on analyzing the role of various carbon materials in composite SiO_۲/C to enhance the performance of SiO_۲ materials. The variety of carbon of composite SiO_۲/C will be grouped as traditional carbon, graphene, carbon nanofibers, and carbon nanotubes. This review also details additional aspects supporting the performance of composite SiO_۲/C materials, such as SiO_۲ nanoparticles, crystals or amorphous phases, and the composition of composite SiO_۲/C.