Electrolytes hold the key for enabling various battery chemistries including lithium batteries. Currently, the electrolyte based on using LiPF6 as salt and ethylene carbonate/dimethyl carbonate as solvents have been very successful for applications under normal conditions. However, extreme conditions can arise from using batteries during very cold weather or increasing the charge voltage limit to increase overall energy density. Conventional electrolytes fail under these conditions because they cannot support effective lithium ion transport across the electrolyte and the interphase. Our lab has been working on developing novel electrolyte for extreme conditions by engineering the solvent and the electrolyte additives. Taking advantage of the local synchrotron facility, we have been able to characterize the electrolyte and the interphase with techniques that are beyond the reach of lab-based tools. The obtained insight helps us to better understand the electrolyte and optimize our development. In this talk, I will give two examples of our recent efforts in this direction.