In this work, we use operando impedance spectroscopy during LIB discharge to quantify loss processes and to inform rational electrode and electrolyte engineering to maximize low temperature performance. We show that the graphite charge transfer resistance is the dominant loss process at low temperatures. We also demonstrate that inclusion of 𝛾-butyrolactone (GBL), a low melting point solvent that has similar structure to ethylene carbonate (EC), into the electrolyte as a co-solvent with EC decreases the resistances at the NMC positive electrode during low temperature operation, but it leads to substantial resistance increases at the graphite negative electrode when compared to a similar electrolyte with no GBL added. We discuss physical explanations for these resistance behaviors. Lastly, we use impedance spectroscopy to develop a coupled ion-electron transfer kinetic model to quantifiably compare the low temperature performance of different LIB chemistries. These findings will enable the development of significantly improved LIB discharge performance at low temperatures, paving the way for wider use and adoption of important LIB-powered devices, such as EVs.