The influence of the operation conditions temperature and state of charge (SOC) on the performance of a commercial high-power lithium-ion cell is investigated by electrochemical impedance spectroscopy. Based on the results of several preliminary tests, measurements were run covering the complete range of automotive applications. The cell impedance is presented and analyzed. A strong nonlinear temperature correlation is shown for all frequency ranges. Although the ohmic resistance is nearly unaffected by variation in SOC, the mass transport impedance reduces from 100% to 60% SOC and increases significantly again for lower SOCs.