Effect of Single-Walled Carbon Nanotubes as Conductive Additives on the Performance of LiCoO2-Based Electrodes

Single-walled carbon nanotubes (SWNTs) and carbon black (CB) were used as conductive additives in lithium-ion batteries. Composites containing nanostructured LiCoO2 and carbon additives were applied as positive electrodes in coin-type electrochemical cells with Li metal as a counter electrode. The conductive SWNTs with their wirelike shape and high aspect ratio are proved to have significant impact on the electrochemical performance of the electrode. The electrode composite containing 0.5 wt % of SWNTs has an internal resistance comparable to that of the 10 wt % of carbon black. Whereas the discharge capacity of the electrode containing 0.5 wt % of CB drops to 0 when increasing the rate to 5C, the capacity of the electrode containing the same weight fraction of SWNTs retains 67% of its initial capacity even at 18C. Cycling performance measured up to 23 cycles demonstrates that the SWNTs at a low concentration are as efficient in the capacity retention as the 10 wt % of carbon black. We interpret the SWNT-induced electrode performance by formation of a flexible, electrically wired network of conducting SWNTs in close contact with LiCoO2 nano-particles, which accelerates the exchange of the Li ions and allows a rapid transfer of electrons throughout the electrode. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3526601] All rights reserved.