TiO2 nanotube branched tree on a carbon nanofiber nanostructure as an anode for high energy and power lithium ion batteries

Abstract

The inherently low electrical conductivity of TiO2-based electrodes as well as the high electrical resistance between an electrode and a current collector represents a major obstacle to their use as an anode for lithium ion batteries. In this study, we report on high-density TiO2 nanotubes (NTs) branched onto a carbon nanofiber (CNF) “tree” that provide a low resistance current path between the current collector and the TiO2 NTs. Compared to a TiO2 NT array grown directly on the current collector, the branched TiO2 NTs tree, coupled with the CNF electrode, exhibited ∼10 times higher areal energy density and excellent rate capability (discharge capacity of ∼150 mA·h·g−1 at a current density of 1,000 mA·g−1). Based on the detailed experimental results and associated theoretical analysis, we demonstrate that the introduction of CNFs with direct electric contact with the current collector enables a significant increase in areal capacity (mA·h·cm−2) as well as excellent rate capability.