Single-, Double-, and Multi-Walled Carbon Nanotubes as Electrically Conductive Additives to Lithium-Ion Battery Cathodes

The characteristics of lithium iron phosphate cathodes containing various types of commercially available carbon nanotubes—single-walled (SWCNTs), double-walled (DWCNTs), and multi-walled (MWCNTs)—have been compared. Electrochemical characteristics of the cathode materials have been studied by electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements. The cyclic stability at various current densities has been estimated. The best electrochemical characteristics are shown by the cathode materials containing SWCNTs (advantage over the DWCNT-based cathode materials at discharge rates higher than 10C) and DWCNTs (advantage over the SWCNT-based cathode materials during long-term cycling). During the long-term cycling at a current density of 1C, the greatest loss of capacity is observed for the MWCNT-based electrode. At the same time, the SWCNT- and DWCNT-based electrodes demonstrate satisfactory capacity retention after 50 charge/discharge cycles: over 94 and 98%, respectively.