Li-7 and F-19 magic angle spinning nuclear magnetic resonance (NMR) allows for the identification and quantification of LiF in the solid electrolyte interphase (SEI) at both electrodes in lithium-ion rechargeable batteries. An estimate of the percent of lithium not reintercalated into the cathode after numerous cycles is also obtained. In the cells presented, more LiF formed on the surface of the anode compared to its respective cathode. Positive correlations have been established for the amount of LiF formed on the cathode with both the number of cycles and the % Li loss from the cathode. (C) 2005 The Electrochemical Society.