Effect of a Ti layer on the growth of binder-free carbon nanotubes on Cu foil and their performance as lithium ion battery anodes

Abstract

We report a unique approach to fabricate lithium ion battery anodes based on multiwalled carbon nanotubes (MWCNTs) grown directly on copper foils via chemical vapor deposition. This process eliminates the use of binders for lithium ion battery anodes. The intermediate conductive Ti and alumina blocking layers have been optimized to seamlessly connect the CNTs with the Cu substrate, providing robust structural integrity that facilitates charge transfer. This anode material showed a high capacity of 448 mA h g⁻¹ at 50 mA g⁻¹, superior rate capability and no capacity degradation up to 70 cycles at different current densities (100 mA g⁻¹ to 500 mA g⁻¹). Within a small voltage window of 0.8 V vs. Li/Li⁺, this anode offers the usable capacity of 300 mA h g⁻¹. The observed electrochemical performance of this anode can be attributed to the high theoretical capacity of carbon nanotubes, faster Li-ion insertion into the walls of CNTs and better conductivity at the point of contact between the substrate and the CNTs enhanced by the inclusion of Ti at the substrate–CNT interface.