We report Si–S full cells with lithiated Nafion-coated porous Si as anode.

We report that spontaneous Li_xSi–Li₂S_y reaction leads to failure of Si-S full cell.

Nafion coating on Si anode improves the Si–S full cell performance.

High specific capacity of Si–S full cell is achieved by optimizing S/Si mass ratio.

The full cell yields capacity of 330 mA h/g and energy density of 590 W h/kg.