Mixed silicon–graphite composites have been prepared by means of mechanical milling process. Their micro-heterogeneous structure is considered responsible for electrode failures. A fingerprint of this process is seen by cycling the carbonaceous component of the composite in an electrolyte containing small amount of propylene–carbonate (PC). Local voltage drops close to 0V (versus Li metal) resulted in local electrode mechanical deterioration. In the presence of silicon particles such local disorders would lead to a loose interparticle contact (zones called dead spots). Deterioration pattern of the mixed composite electrode may be considered as a set of ‘dead spots’ spreading across the electrode as the cycling proceeds. Hence, a careful optimization is necessary in order to fabricate composite electrode giving minimum local disorders and having satisfactory cycling performance.