The specific electrostatic capacity QSi/C of (SiC)12 composites is determined by the formula QSi/C = αSiQSi + αcQC = 3051 mAh/h (where αC=0.3, αSi=0.7 – mole fractions and QC = 372 and QSi = 4200 mAh/h – theoretical specific capacities of carbon and silicon respectively).