At Sandia National Laboratories, we have built 18650 Li-ion cells with Li reference electrode for in situ characterization of electrodes including impedance and other electrochemical properties. At a 200 mA (similar to C/5 rate) discharge, the cell gave similar to 900 mAh. Impedance measurements indicate that the anode dominates the cell impedance. For example, at 0 degrees C, the anode and cathode impedances at 10 mHz were around 149 and 53 m Omega, respectively, and the total cell impedance at 10 mHz was similar to 203 m Omega. The three-electrode configuration also permits measurement of individual electrode voltages during charge and discharge. During discharge, while the cell voltage drops from 4.1 to 3 V, the cathode and the anode voltages change from 4.1 to 3.7 and from similar to 0 to 0.7 V, respectively. During charge, the cathode and anode voltages trace back to their initial values before discharging. The voltage swing for the anode is higher than that for the cathode. This also indicates that the impedance for the anode is higher than for the cathode. Pulse measurements on the cells indicate the voltage drop of the full-cell is equal to the sum of the anode and cathode voltage drops for a 2 A discharge pulse. (c) 2005 Published by Elsevier B.V.