The commercial 18650 Li(Ni1/3Co1/3Mn1/3)O-2/graphite high power batteries were prepared and their electrochemical performance at temperatures of 25 and 50 degrees C was extensively investigated. The results showed that the charge-transfer resistance (R-ct) and solid electrolyte interface resistance (R-sei) of the high power batteries at 25 degrees C decreased as states of charge (SOC) increased from 0 to 60%, whereas Rct and Rsei increased as SOC increased from 60 to 100%. The discharge plateau voltage of batteries reduced greatly with the increase in discharge rate at both 25 and 50 degrees C. The high power batteries could be discharged at a very wide current range to deliver most of their capacity and also showed excellent power cycling performance with discharge rate of as high as 10C at 25 degrees C. The elevated working temperature did not influence the battery discharge capacity and cycling performance at lower discharge rates (e.g. 0.5, 1, and 5 C), while it resulted in lower discharge capacity at higher discharge rates (e.g. 10 and 15 C) and bad cycling performance at discharge rate of 10 C. The batteries also exhibited excellent cycle performance at charge rate of as high as 8 C and discharge rate of 10 C. (C) 2008 Elsevier B.V. All rights reserved.