The study of carbon nanotubes as conductive additives of cathode in lithium ion batteries

Abstract

Carbon nanotubes (CNTs), including multi-walled CNTs (MWCNTs) and single-walled CNTs (SWCNTs), are employed as conductive additives in lithium ion batteries. The effects of MWCNTs’ carbon precursors, diameter, and weight fraction on the electrochemical behavior of MWCNTs/LiCoO2 composite cathode are investigated. Meanwhile, a comparison is made between SWCNTs /LiCoO2 and MWCNTs/LiCoO2. Among the three kinds of carbon precursors: CH4, natural gas, and C2H2, MWCNTs prepared from CH4 are very fit for acting as conductive additives due to their better crystallinity and lower electrical resistance. MWCNTs with smaller diameter favor improving the electrochemical behavior of MWCNTs/LiCoO2 composite cathode at higher charge/discharge rate owing to their advantage in primary particle number in unit mass. To make full use of LiCoO2 at higher rate, it is necessary to add at least 5 wt.% of MWCNTs with a diameter 10~30 nm. However, SWCNTs are not expected to be added into LiCoO2 composite cathode since they tend to form bundles.