Silicon and its Composites as Anode Materials in Li-ion Batteries

Abstract

Recent technological advances need a reliable and sustainable energy storage system with a high energy density.  LiCoO₂ and graphite are the cathode and anode materials used in current Li-ion batteries, respectively, however their capacity is restricted. The anode side of the battery plays an important function in storing Li-ions during charging and discharging cycles. Si has evolved as a unique anode material in recent decades with a theoretical capacity almost ten times that of traditional graphite. But there are various issues with Si, like massive volume expansion, electrode pulverization, decreasing cell capacity over time, etc. The electrochemical output of Si and its composites is determined by the materials utilized. Direct alloying of Si with Li yields stable phases such as Li₁₂Si₇, Li₇Si₃, Li₁₃Si₄ and Li₂₁Si₅ with the highest theoretical capacity. Composites of Si, which include carbon, polymer and other elements, exhibit promising outcomes. This paper summarizes and discusses current breakthroughs in Si and its composites tested as anodes in Li-ion batteries. The use of 1D, 2D and 3D carbon with various matrices for Si composite helps to accommodate volume expansion. Structural and morphological changes as well as the electrochemical performance of thus synthesized batteries have also been described.