High aspect ratio, electrospun CuO nanofibers have been fabricated and tested for its electrochemical performance as lithium ion battery anode. These nanofibers are composed of CuO nanoparticles about 35 -40 nm in size forming good inter-connected network. Fabricated half cells maintained specific capacity of 310 mAh g(-1) at 1C rate for 100 cycles and stabilized capacity of about 120 mAh g(-1) at 5C rate for 1000 cycles. Ex situ x-ray photoelectron spectroscopy (XPS) was performed to understand the electrodes surface chemical changes at the end of first discharge, first charge and after tenth charge. The solid electrolyte interface (SE!) layer comprised of LiF, Li2CO3 and Li2O while their quantity varied depending on the stage of lithiation/delithiation. Initially, no copper signal is observed on the surface of the SE! layer. However, in situ sputtering of the electrodes in the XPS chamber revealed that at the end of first discharge, formation Cu-0 with detectable fraction of LixCuO2 and hydroxide in the SE! layer. At the end of first charge, a large fraction of Cu2O phase with a small fraction of hydroxide is observed. At the end of 10th charge no change in SEI layer content but increase in thickness was observed. (C) 2016 Elsevier B.V. All rights reserved.