Surface chemical analysis of CuO nanofiber composite electrodes at different stages of lithiation/delithiation

Abstract

Abstract 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 (SEI) layer comprised of LiF, Li 2 CO 3 and Li 2 O while their quantity varied depending on the stage of lithiation/delithiation. Initially, no copper signal is observed on the surface of the SEI 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 Li x CuO 2 and hydroxide in the SEI layer. At the end of first charge, a large fraction of Cu 2 O 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.