Silicon is one of the most promising high-energy-density anode materials for upcoming generations of lithium ion batteries. Its high capacity (4200 mAh/g, 9660 mAh/cm^3) is associated with its very high lithium content, which results in drastic volume expansion. Consequently, silicon-based anodes often undergo strong capacity fading induced by cracking, electrolytic side reactions and low ionic and electrical conductivities. These issues can be managed by introducing a carbonaceous buffer shell around silicon in order to obtain chemomechanically consistent composite particles. Understanding the thermodynamics and kinetics during lithium transport in such hybrid structures is a prerequisite for their effective use. Therefore, we have applied ab initio methods based on density functional theory to investigate the properties of bulk, surface and interfacial structures. Using the resulting quantum mechanical dataset, we have developed a reactive force field for the Li–Si–C system which is able to describe phenomena observed during electrochemical cycling.