Do Composite Single-Walled Nanotubes Have Enhanced Capability for Lithium Storage?

The lithium adsorption energies of C, BC 3, BC 2 N, and BN single-walled nanotubes and the electronic structures of the lithium-intercalated nanotubes products were computed using density functional methods. Due to the strong propensity of boron to accept electrons from lithium energetically, the electron-deficient BC 3 nanotubes, both zigzag and armchair, adsorb lithium very favorably. Electron-sufficient BN nanotubes with partial ionic bonding, in contrast, adsorb lithium poorly. In addition, the wide band gap and low electrical conductivity of BN nanotubes make them unsuitable for Li ion battery applications. Hence, Li adsorption depends critically on the electronic structure of composite nanotubes. Also, our study of lithium diffusion in C and BC 3 nanotubes revealed that high energy barriers preclude Li passage through the sidewalls of perfect BC 3 nanotubes. However, the penetration barriers for C nanotubes are twice as large. Model studies also show that it is possible that dilithium can be adsorbed favorably on the exterior of carbon nanotubes, while the BC 3 tubes can adsorb lithium atoms both inside and outside. The present computations suggest that BC 3 nanotubes are promising candidates for Li intercalation materials suitable for battery applications.