Boron (B) has a high theoretical lithium storage capacity of 3046 mAh g(-1) for forming Li5B4 phase. Li-B alloy has been used in high temperature thermal lithium batteries. In this work, a new tetragonal boron (B-50) thin film with a thickness of 80 nm has been deposited on a vanadium coated glass substrate by a pulse laser deposition (PLD) method. It is found that this electrode film shows only a lithium storage capacity of 43 mAh g(-1) in a nonaqueous electrolyte at room temperature. According to a first-principles calculation, the B-50 is a metallic conductor. Therefore, the very poor activity could be related to poor lithium ion diffusion property since the diffusion barrier in this tetragonal B-50 lattice is calculated as 2.59 eV. This consists well with the fact that the lithium storage capacity in the B-50 thin film is improved significantly to 268 mAh g(-1) at 85 degrees C. (C) 2012 Elsevier Ltd. All rights reserved.