【Abstract】 The discharge behavior and uniformity of lithium-ion batteries were experimentally investigated at low temperatures. The discharge test and electrochemical impedance spectroscopy (EIS) test were conducted for several commercial 18650 type cells. The cell average capacity decreases by 58.4% with the capacity standard deviation increasing by 6.6 times when the temperature decreases from 25 ℃ to -20 ℃. The charge transfer resistance (Rct) dramatically increases, dominating other types of resistance. The cell impedance variations, mainly in the Rct, increase significantly at lower temperatures. A linear correlation between the capacity and the over-potential resistance is established by statistics from 15 cells. Therefore, at low temperatures, the cell-to-cell capacity variation increase is attributed to the cell over-potential resistance (mainly the Rct) variation increase.