Within this work, we investigate the structural and electrochemical properties of new composite materials based on disordered carbons embedded into a polymer-derived silicon carbonitride matrix. In particular, we focus on the relationship between the initial characteristic of disordered carbon, that is its microstructure and porosity with the lithiumions storage properties of the composite. Although there is almost no difference between composites found by means of Raman spectroscopy and X-ray powder diffraction, it is demonstrated that the pore volume of the carbon is of significant importance, i.e., volume of the preceramic polymer must be matched with pore volume of the carbon in order to ensure the optimal electrochemical performance. Thus, it is possible to synthesize a composite containing only 50 % of external carbon, which recovers the capacity comparable to that of pure carbon.