Lithium ion batteries (LIBs) have been considered as a key component for popularizing personal electric devices such as laptops, cell phones and digital cameras, due to the unique properties of LIBs including high power and energy densities, low self-discharge rate and no memory effect. In particular, LIBs enable super-slim smartphones and laptops by providing high energy within extremely limited space. Accordingly, for the last 25 years, LIBs have led us to developing ever-smaller, more powerful and portable electronic devices and being free from being tethered to a grid by wires. However, current LIBs technology faces new challenges of popularizing electric vehicles (EVs), which requires approximately quadruple more energy than that supplied by conventional LIBs to enable 800 km-driving, corresponding to a petrol tank, by EVs. There have been many efforts to improve the energy density of battery, by searching alternative anode and cathode materials which can overcome the limitation of the conventional LIBs. In this work, we propose a simple and reliable method for large-scale synthesis of Si@SiC by magnesium thermal reduction method in which a SiO₂@C composite was reduced by magnesium vapor at temperature of 600 ^oC. By controlling the carbon content in SiO₂@C sample we could prepare Si@SiC with various SiC content. Interestingly, the Si@SiC exhibited an outstanding electrochemical performance such as ultra-long cyclability, an excellent rate capability, and high reversible capacity. Furthermore, the full cell fabricated by coupling Si@SiC anode and lithiated-sulfur cathode showed extremely high energy density and power density.