The electrolytes for SEB cells were formulated by reducing EC content and adding TAP as an additive. Although EC is an essential solvent for SEI layer formation, it also leads to gas generation, especially at high voltage (13). Calendar aging testing shows that high-temperature and high-SOC conditions accelerate capacity fade and increase in internal resistance while also promoting gas generation. SEB cells initially contains 10 wt % EC in the electrolyte. Some EC is consumed during the formation cycle, resulting in an EC content much less than 10% in formed SEB cells. This is advantageous since the rate of gas generation in an EC-less electrolyte would be lower than that in an electrolyte with high EC content.