Remarkable Impact of Water on the Discharge Performance of a Silicon–Air Battery

Abstract Here, we report on a Si–air/ionic liquid electrolyte battery whose performance improves with small amounts of water in the electrolyte. The shift of the generation zone of the SiO 2 discharge product from the air cathode surface into the bulk region of the liquid electrolyte, caused by water addition, is demonstrated through various means. Addition of 15 vol % water leads to an increase of 40 % in the discharge capacity as compared to the capacity obtained using a pure ionic liquid electrolyte. If the water content increases above 20 vol %, the Si–air cell capacity dramatically decreases. The water–ionic liquid electrolyte mixture shows a maximum in the ionic conductivity with a water content of 10 vol %. In‐depth studies indicate a reduced amount of discharge product at the air electrode using 15 vol % H 2 O electrolyte. The morphology of the anode surface, as well as the developed surface film in the presence of water‐containing ionic liquid, is reported. This study shows that exposing a Si–air battery to a humid environment does not result in capacity losses, but rather improves cell performance.