Semimetallic Si3C as a high capacity anode material for advanced lithium ion batteries

In combination of the merits of Si- and C-based anode materials for lithium-ion batteries (LIBs), we propose and evaluate the potential of novel Si₃C as an anode material, which consists of light silicon and carbon atoms and is characterized by a Dirac cone. The adsorption energy for lithium atom is identified to be −2.58 eV, which is large enough to ensure a good lithium adsorption stability during the (de)lithiation process. Our results reveal that the energy barrier for Li diffusion on Si₃C is only 0.46 eV, indicative of a fast charge/discharge rate. In addition, Si₃C exhibits a semimetallic nature with a great advantage in electrical conductivity. Remarkably, the fully lithiated phase of Si₃C is (Li₆Si₃C)₂, corresponding to a theoretical specific capacity of 1675 mAh/g, almost 4.5 times higher than that of commercial graphite (375 mAh/g). Besides, the low open-circuit voltage (OCV) of (Li₆Si₃C)₂ is determined to be 0.2 V. These intriguing superiorities endow the Si₃C a promising anode material for LIBs.