The intrinsic role of c-Li15Si4 on capacity retention was examined by modulating the cycling conditions to either maximize or minimize its formation for three distinct Si absolutely and relatively with respect to the total delithiation capacity as cycling progresses. A causal and general link between the formation of the c-Li15Si4 phase and capacity decay was not obvious, as capacity decayed at a similar rate for the CC and CCCV protocols in silicon nanoparticle electrodes and porous Si films. This observation is in contrast to the planar thin films, where it was found that c-Li15Si4 is linked directly to an increased capacity loss, most likely due to delamination. While the c-Li15Si4 phase is not associated with greater capacity loss in porous films and silicon nanoparticles, it does seem to be more reactive with the electrolyte. The larger buildup of SEI is observable both through larger polarization of the electrode and lower coulombic efficiencies using the CCCV protocol as compared to CC. Increasing the cut-off voltage in CCCV cycling resulted in both lower amounts of c-Li15Si4 and lower cumulative irreversibilities due to electrolyte decomposition, confirming the increased reactivity of c-Li15Si4 compared to an amorphous phase. Since there is no conclusive evidence for enhanced capacity degradation, the higher reactivity with the electrolyte should be regarded as the main reason for avoiding formation of the c-Li15Si4 phase.